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Int J Electrochem Sci 8 (2013) 5067 - 5085
International Journal of
ELECTROCHEMICAL SCIENCE
wwwelectrochemsciorg
Ionic Conductivity and Thermophysical Properties of 1-Butyl-1-
Methylpyrrolidinium Butyl Sulfate and its Binary Mixtures with
Poly(ethylene glycol) at Various Temperatures
Tzi-Yi Wu Lin Hao Pin-Rong Chen Jian-Wei Liao
Department of Chemical and Materials Engineering National Yunlin University of Science and
Technology Yunlin 64002 Taiwan ROC
E-mail wutyyuntechedutw
Received 18 February 2013 Accepted 16 March 2013 Published 1 April 2013
The work studies the synthesis and thermophysical characterization of butylsulfate-based Ionic Liquid
(IL) [PyrMB][BuSO4] The synthesized IL is characterized by NMR spectroscopy elemental analysis
and Karl Fischer titration Thermophysical properties such as density viscosity and conductivity
for the binary mixture of butylsulfate-based IL [PyrMB][BuSO4] with poly(ethylene glycol) (PEG)
[Mw = 200] are measured over the whole composition range The thermal expansion coefficient of neat
[PyrMB][BuSO4] and its binary mixtures is ascertained using the experimental density results and
their excess volume expansivity is also estimated The temperature dependence of viscosity and
conductivity over the whole composition range can be described by the Vogel-Tammann-Fulcher
(VTF) equation and the maximum of conductivity is located at xPEG200 = 059 and corresponds to a
value of 171 mS cmminus 1
at 33315 K The excess properties and deviations are fitted to the Redlich-Kister polynomial equation to obtain the binary coefficients and the standard errors The variation of
these properties with composition of the binary mixtures is discussed in terms of molecular
interactions between components and structural effects
Keywords ionic liquids binary mixture viscosity conductivity Vogel-Tammann-Fulcher equation
excess properties deviations
1 INTRODUCTION
Room temperature ionic liquids (ILs) are typically salts that contain at least one organic cation
or anion and have melting points below or not far above ambient temperatures [1] The
physicochemical properties of ILs can be molecularly designed to positively affect different kinds of
processes by varying these anions and cations [2-5] During the past decade ionic liquids (ILs) have
attracted increasing attention and intensive investigation and witnessed a steady growth from the
Int J Electrochem Sci Vol 8 2013
5068
academics to industry due to their distinctive properties such as wide temperature range of application
high thermal stability [3-5] nonflammability wide electrochemical window [6-9] and high electrical
conductivity [10-13] They have been used in a broad variety of synthesis [1415] corrosion inhibition
[16-20] biotechnology [21-24] and nano technology [25-32] especially as promising ldquogreenrdquo
electrolyte for electrochemical devices such as dye-sensitized solar cells [33ndash38] lithium ion batteries
[39-42] sensors [43-55] and fuel cells [56] but experimental data of physicochemical properties [57-
61] are still scarce Alkylsulfate-based ILs are some of the most promising ILs to be applied in
academic investigations and industrial processes since most of these ILs can be easily synthesized at a
reasonable cost [62] So far the viscosity of sulfate-based ILs are 1 to 3 orders of magnitude greater
than those of traditional organic liquids which affect the rate of mass transfer leading to much more
power needed for mixing in liquid reactions or separation processes In some current studies the
problem of high viscosity can be resolved partially by means of adding organic solvents to pure ionic
liquid [63] Although the addition of organic solvents into ILs decreases the viscosity of mixture
significantly the conventional organic solvents has high volatility due to their boiling temperature are
below 80 oC Accordingly some scientists studied the thermodynamic properties of ethylene glycol
derivatives instead of conventional organic solvents Poly(ethylene glycol) (PEG) is one of the
ethylene glycol derivatives PEG of various molecular weights have been widely used in processes
across many industrial sectors as a result of being non-toxic biodegradable inexpensive widely
available and with a very low volatility [6465] Low molecular weight PEG (Mw = 200) is liquid at
room temperature making it easy to combine with ILs generate solvent systems and thus use in
advanced environmentally friendly processes [65]
In the present research the density viscosity and conductivity of a sulfate-based IL
([PyrMB][BuSO4]) and its binary mixture with PEG200 over the whole composition range and
temperatures between (29315 and 35315) K at atmospheric pressure are estimated From these
experimental results excess molar volume excess volume expansivity and viscosity deviations from
the ideal behavior were characterized The excess properties were calculated and then correlated at
each temperature as a function of composition by a Redlich-Kister-type equation The impact nature
of the solute on the ionic conductivity and thermophysical properties of binary mixture was
investigated in detail
2 EXPERIMENTAL
21 Materials
Poly(ethylene glycol)s dibutyl sulfate and 1-methylpyrrolidine were obtained from
commercial suppliers and used without further purification The poly(ethylene glycol)s of average
molar mass 200 was purchased from Showa Chemical Industry Co Ltd Japan dibutyl sulfate (95 )
and 1-methylpyrrolidine (gt98 ) was purchased from Tokyo Chemical Industry Co Ltd
Int J Electrochem Sci Vol 8 2013
5069
22 1-Butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])
Dibutyl sulfate (757 g 360 mmol) was added dropwise to a solution of equal molar amounts of
1-methylpyrrolidine (3065 g 360 mmol) in 200 mL toluene and then cooled in an ice-bath under
nitrogen at a rate that maintained the reaction temperature below 31315 K (highly exothermic
reaction) The reaction mixture was stirred at room temperature for 4h After the reaction stopped the
upper organic phase of the resulting mixture was decanted and the lower ionic liquid phase was
washed with ethyl acetate (4 x 70 mL) After the last washing the remaining ethyl acetate was
removed by rotavapor under reduced pressure The IL obtained was dried by heating at (34315 to
35315) K and stirring under a high vacuum (2 10-1
Pa) for 48 h In order to reduce the water content
to negligible values (lower than 003 mass ) a vacuum (2 x 10-1
Pa) and moderate temperature
(34315 K) were applied to the IL for 2 days The IL was kept in bottles under an inert gas The
structure of [PyrMB][BuSO4] is shown in Figure 1
Yield 91 1H NMR (300 MHz D2O ppm) 395 (t 2H -CH2SO4) 338 (m 4H N-CH2-)
321 (m 2H N-CH2-) 292 (s 3H N-CH3) 210 (m 4H N-CH2CH2-) 167 (m 2H -CH2CH2SO4)
155 (m 2H N-CH2CH2-) 128 (m 4H N-CH2CH2CH2- and -CH2CH2CH2SO4) 082 (m 6H N-
CH2CH2CH2CH3 and CH3CH2CH2CH2SO4) Elem Anal Calcd for C13H29NO4S C 5285 H 989
N 474 Found C 5268 H 979 N 465
NC4H9SO4
Figure 1 Molecular structure of 1-butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])
23 Measurements
The conductivity () of the ionic liquids was systematically measured with a conductivity
meter (LF 340 WTW Germany) and a standard conductivity cell (TetraCon 325 WTW Germany)
The cell constant was determined by calibration after each sample measurement using an aqueous 001
M KCl solution The density of the ILs was measured with a dilatometer which was calibrated by
measuring the density of neat glycerin at 30 40 50 60 70 and 80 oC The dilatometer was placed in a
thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K
To measure density IL or a binary mixture was placed into the dilatometer up to the mark the top of
the capillary tube (located on the top of the dilatometer) was sealed and the dilatometer (with capillary
tube) was placed into a temperature bath for 10 min to allow the temperature to equilibrate The main
interval between the two marks in the capillary tube was 001 cm3 and the minor interval between two
marks was 0001 cm3 From the correction coefficient of glycerin in capillary tube at various
temperatures we can calculate the density of neat IL or binary system by the expanded volume of
liquid in the capillary tube at various temperatures Each sample was measured at least three times to
determine an average value and the values of the density were plusmn00001 gmL The viscosity (η) of the
Int J Electrochem Sci Vol 8 2013
5070
IL was measured using a calibrated modified Ostwald viscometer (Cannon-Fenske glass capillary
viscometers CFRU 9721-A50) The viscometer capillary diameter was 12 mm as measured using a
caliper (model No PD-153) with an accuracy of plusmn 002 mm The viscometer was placed in a
thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K
The flow time was measured using a stopwatch with a resolution of 001 s For each IL the
experimental viscosity was obtained by averaging three to five flow time measurements The water
content of synthesized IL [PyrMB][BuSO4] was determined using the KarlndashFischer method the
content was below 300 ppm The nuclear magnetic resonance (NMR) spectra of the synthesized IL
were recorded on a BRUKER AV300 spectrometer and calibrated with tetramethylsilane (TMS) as the
internal reference
3 RESULTS AND DISCUSSION
31 Density and excess molar volume
The densities of neat IL [PyrMB][BuSO4] neat PEG200 and PEG200 (1) + [PyrMB][BuSO4]
(2) binary mixture over the temperature range (29315 to 35315) K and at atmospheric pressure are
presented in Table 1 and Figure 2 As shown in Figure 2 the trend of density for the binary system
with respect to temperature was decreased with increasing temperature The variations of the densities
with concentration at the different temperatures studied are shown in Figure 3 from analysis of the
data it was found that the densities depend more strongly on the mole fraction of PEG200 in the
mixture than on temperature
Figure 2 ρ vs T plot of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system
A third-order polynomial was found to satisfactorily correlate the change of density with various
compositions
T K
290 300 310 320 330 340 350 360
g
cm
-3
109
110
111
112
113
114
x1 = 00000
x1 = 01452
x1 = 01942
x1 = 02912
x1 = 03897
x1 = 04893
x1 = 05890
x1 = 06903
x1 = 07922
x1 = 08958
Int J Electrochem Sci Vol 8 2013
5071
ρ = a0 + a1 x1 + a2 x12 + a3 x1
3 (1)
where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit
parameters are listed in Table 2 for the mixtures
Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)
+ [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ρg middotcm-3
0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912
01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936
01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949
02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972
03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984
04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984
05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973
06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948
07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923
08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896
1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860
E
mV cm3 mol-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003
01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375
02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952
03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061
04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201
05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459
06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997
07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903
08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration
at various temperatures
The correlation constants for Eq (1) were established using the least square method and are
presented in Table 2 along with the standard deviation estimated using the following equation
2
exp cal 1 2( - )
[ ]Z Z
n
(2)
x1
00 02 04 06 08 10
g c
m-3
106
108
110
112
114
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5072
where n is the number of experimental points and Zexp and Zcal are the experimental and
calculated values respectively
Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm
-3) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK a0 g cm
-3 a1 g cm
-3 a2 g cm
-3 a3 g cm
-3
29315 11248 00455 -00638 0024 0000840
29815 11219 00447 -00617 00217 0000800
30315 1119 00439 -00596 00195 0000764
30815 11161 00431 -00575 00173 0000732
31315 11132 00422 -00554 00152 0000704
31815 11103 00413 -00533 00132 0000680
32315 11075 00403 -00512 00112 0000660
32815 11046 00393 -00492 00093 0000640
33315 11018 00382 -00471 00074 0000625
33815 10989 00372 -0045 00055 0000613
34315 10961 0036 -0043 00037 0000606
34815 10933 00349 -00409 0002 0000596
35315 10905 00337 -00389 00003 0000592
a ρ = a0 + a1 x1 + a2 x1
2 + a3 x1
3
As can be seen from the Table 1 the value of the density decreases with increasing temperature
eventhough the variation is very small If the variation of the density with the temperature is
considered as linear then the change in the calculated thermal expansion coefficient values becomes
nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was
used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]
(2) binary system
ρ = b0 + b1 T + b2 T2 (3)
where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation
coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)
Excess thermodynamic properties are of great importance for understanding the nature of
molecular interaction in binary mixtures The excess molar volume E
mV which is the difference
between the real and ideal mixing behaviors is defined by
m m 1 1 2 2 E o o
V V xV x V (4)
where Vm represents the volume of a mixture containing one mole of (PEG200 +
[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2
([PyrMB][BuSO4]) respectively and V10 and V2
0 are the molar volumes of the pure components The
Int J Electrochem Sci Vol 8 2013
5073
excess molar volumes of mixtures over the entire composition range were calculated from our
measurements of density according to the following equation
Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat
PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]
(2)
x1 b0 b1 b2
0 1326 -000077105 00000003 000003
01452 1301 -0000588 0 000023
01942 1304 -0000593 0 000032
02912 131 -0000604 0 000047
03897 1315 -0000613 0 000009
04893 1318 -0000621 0 000034
05890 1319 -0000629 0 000045
06903 132 -0000639 0 000046
07922 1325 -0000658 0 000036
08958 1335 -0000694 0 000030
1 1405 -000108 000000051 000112
Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and
fitted curves using the Redlich-Kister parameters
1 1 2 2 1 1 2 2m
1 2
E
Vx M x M x M x M
(5)
where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture
respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E
mV
values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole
x1
00 02 04 06 08 10
Vm
E
cm
3 m
ol-1
-20
-15
-10
-05
00
30315 K
31315 K
32315 K
33315 K
Int J Electrochem Sci Vol 8 2013
5074
fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the
binary system is mainly concerned with the weak chemical interactions the physical and structural
characteristics of the system components If the chemical or nonchemical interaction of the same
components is the dominant way of the interaction the excess volume of the mixture should be
positive If the molecules of the components have a more effective packing in the mixture than that in
the pure component that is the attracting interaction between the molecules of two components is the
dominant way the excess molar volume of the binary system should be negative [66] As shown in
Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the
entire composition range the minimum of E
mV is reached at a mole fraction of PEG200 near x1 = 04
and the absolute values of the excess volume increase with increasing temperature The molar volume
for [PyrMB][BuSO4] is 26243 cm3 mol
-1 at T = 29315 K which is greater than the molar volumes of
PEG200 (17681 cm3 mol
-1) at T = 29315 K The large difference between molar volumes of the
molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic
molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids
in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)
oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar
excess volumes
32 Volume expansivity and excess volume expansivity
Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were
also used to derive the coefficient of thermal expansion From the relationship of vs T the volume
expansivity (coefficient of thermal expansion) α is defined as
1 1
( ) ( )p p
V
TV T
(6)
where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and
PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion
coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature
and increases with increasing mole fraction of the PEG200
The corresponding excess function (excess volume expansivity) was calculated using
E id id
1 1 2 2 (7)
where id
1 is an ideal volume fraction given by the following relation
1 m11
1 m1 2 m2
id xV
xV x V
(8)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5068
academics to industry due to their distinctive properties such as wide temperature range of application
high thermal stability [3-5] nonflammability wide electrochemical window [6-9] and high electrical
conductivity [10-13] They have been used in a broad variety of synthesis [1415] corrosion inhibition
[16-20] biotechnology [21-24] and nano technology [25-32] especially as promising ldquogreenrdquo
electrolyte for electrochemical devices such as dye-sensitized solar cells [33ndash38] lithium ion batteries
[39-42] sensors [43-55] and fuel cells [56] but experimental data of physicochemical properties [57-
61] are still scarce Alkylsulfate-based ILs are some of the most promising ILs to be applied in
academic investigations and industrial processes since most of these ILs can be easily synthesized at a
reasonable cost [62] So far the viscosity of sulfate-based ILs are 1 to 3 orders of magnitude greater
than those of traditional organic liquids which affect the rate of mass transfer leading to much more
power needed for mixing in liquid reactions or separation processes In some current studies the
problem of high viscosity can be resolved partially by means of adding organic solvents to pure ionic
liquid [63] Although the addition of organic solvents into ILs decreases the viscosity of mixture
significantly the conventional organic solvents has high volatility due to their boiling temperature are
below 80 oC Accordingly some scientists studied the thermodynamic properties of ethylene glycol
derivatives instead of conventional organic solvents Poly(ethylene glycol) (PEG) is one of the
ethylene glycol derivatives PEG of various molecular weights have been widely used in processes
across many industrial sectors as a result of being non-toxic biodegradable inexpensive widely
available and with a very low volatility [6465] Low molecular weight PEG (Mw = 200) is liquid at
room temperature making it easy to combine with ILs generate solvent systems and thus use in
advanced environmentally friendly processes [65]
In the present research the density viscosity and conductivity of a sulfate-based IL
([PyrMB][BuSO4]) and its binary mixture with PEG200 over the whole composition range and
temperatures between (29315 and 35315) K at atmospheric pressure are estimated From these
experimental results excess molar volume excess volume expansivity and viscosity deviations from
the ideal behavior were characterized The excess properties were calculated and then correlated at
each temperature as a function of composition by a Redlich-Kister-type equation The impact nature
of the solute on the ionic conductivity and thermophysical properties of binary mixture was
investigated in detail
2 EXPERIMENTAL
21 Materials
Poly(ethylene glycol)s dibutyl sulfate and 1-methylpyrrolidine were obtained from
commercial suppliers and used without further purification The poly(ethylene glycol)s of average
molar mass 200 was purchased from Showa Chemical Industry Co Ltd Japan dibutyl sulfate (95 )
and 1-methylpyrrolidine (gt98 ) was purchased from Tokyo Chemical Industry Co Ltd
Int J Electrochem Sci Vol 8 2013
5069
22 1-Butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])
Dibutyl sulfate (757 g 360 mmol) was added dropwise to a solution of equal molar amounts of
1-methylpyrrolidine (3065 g 360 mmol) in 200 mL toluene and then cooled in an ice-bath under
nitrogen at a rate that maintained the reaction temperature below 31315 K (highly exothermic
reaction) The reaction mixture was stirred at room temperature for 4h After the reaction stopped the
upper organic phase of the resulting mixture was decanted and the lower ionic liquid phase was
washed with ethyl acetate (4 x 70 mL) After the last washing the remaining ethyl acetate was
removed by rotavapor under reduced pressure The IL obtained was dried by heating at (34315 to
35315) K and stirring under a high vacuum (2 10-1
Pa) for 48 h In order to reduce the water content
to negligible values (lower than 003 mass ) a vacuum (2 x 10-1
Pa) and moderate temperature
(34315 K) were applied to the IL for 2 days The IL was kept in bottles under an inert gas The
structure of [PyrMB][BuSO4] is shown in Figure 1
Yield 91 1H NMR (300 MHz D2O ppm) 395 (t 2H -CH2SO4) 338 (m 4H N-CH2-)
321 (m 2H N-CH2-) 292 (s 3H N-CH3) 210 (m 4H N-CH2CH2-) 167 (m 2H -CH2CH2SO4)
155 (m 2H N-CH2CH2-) 128 (m 4H N-CH2CH2CH2- and -CH2CH2CH2SO4) 082 (m 6H N-
CH2CH2CH2CH3 and CH3CH2CH2CH2SO4) Elem Anal Calcd for C13H29NO4S C 5285 H 989
N 474 Found C 5268 H 979 N 465
NC4H9SO4
Figure 1 Molecular structure of 1-butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])
23 Measurements
The conductivity () of the ionic liquids was systematically measured with a conductivity
meter (LF 340 WTW Germany) and a standard conductivity cell (TetraCon 325 WTW Germany)
The cell constant was determined by calibration after each sample measurement using an aqueous 001
M KCl solution The density of the ILs was measured with a dilatometer which was calibrated by
measuring the density of neat glycerin at 30 40 50 60 70 and 80 oC The dilatometer was placed in a
thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K
To measure density IL or a binary mixture was placed into the dilatometer up to the mark the top of
the capillary tube (located on the top of the dilatometer) was sealed and the dilatometer (with capillary
tube) was placed into a temperature bath for 10 min to allow the temperature to equilibrate The main
interval between the two marks in the capillary tube was 001 cm3 and the minor interval between two
marks was 0001 cm3 From the correction coefficient of glycerin in capillary tube at various
temperatures we can calculate the density of neat IL or binary system by the expanded volume of
liquid in the capillary tube at various temperatures Each sample was measured at least three times to
determine an average value and the values of the density were plusmn00001 gmL The viscosity (η) of the
Int J Electrochem Sci Vol 8 2013
5070
IL was measured using a calibrated modified Ostwald viscometer (Cannon-Fenske glass capillary
viscometers CFRU 9721-A50) The viscometer capillary diameter was 12 mm as measured using a
caliper (model No PD-153) with an accuracy of plusmn 002 mm The viscometer was placed in a
thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K
The flow time was measured using a stopwatch with a resolution of 001 s For each IL the
experimental viscosity was obtained by averaging three to five flow time measurements The water
content of synthesized IL [PyrMB][BuSO4] was determined using the KarlndashFischer method the
content was below 300 ppm The nuclear magnetic resonance (NMR) spectra of the synthesized IL
were recorded on a BRUKER AV300 spectrometer and calibrated with tetramethylsilane (TMS) as the
internal reference
3 RESULTS AND DISCUSSION
31 Density and excess molar volume
The densities of neat IL [PyrMB][BuSO4] neat PEG200 and PEG200 (1) + [PyrMB][BuSO4]
(2) binary mixture over the temperature range (29315 to 35315) K and at atmospheric pressure are
presented in Table 1 and Figure 2 As shown in Figure 2 the trend of density for the binary system
with respect to temperature was decreased with increasing temperature The variations of the densities
with concentration at the different temperatures studied are shown in Figure 3 from analysis of the
data it was found that the densities depend more strongly on the mole fraction of PEG200 in the
mixture than on temperature
Figure 2 ρ vs T plot of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system
A third-order polynomial was found to satisfactorily correlate the change of density with various
compositions
T K
290 300 310 320 330 340 350 360
g
cm
-3
109
110
111
112
113
114
x1 = 00000
x1 = 01452
x1 = 01942
x1 = 02912
x1 = 03897
x1 = 04893
x1 = 05890
x1 = 06903
x1 = 07922
x1 = 08958
Int J Electrochem Sci Vol 8 2013
5071
ρ = a0 + a1 x1 + a2 x12 + a3 x1
3 (1)
where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit
parameters are listed in Table 2 for the mixtures
Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)
+ [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ρg middotcm-3
0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912
01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936
01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949
02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972
03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984
04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984
05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973
06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948
07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923
08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896
1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860
E
mV cm3 mol-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003
01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375
02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952
03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061
04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201
05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459
06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997
07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903
08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration
at various temperatures
The correlation constants for Eq (1) were established using the least square method and are
presented in Table 2 along with the standard deviation estimated using the following equation
2
exp cal 1 2( - )
[ ]Z Z
n
(2)
x1
00 02 04 06 08 10
g c
m-3
106
108
110
112
114
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5072
where n is the number of experimental points and Zexp and Zcal are the experimental and
calculated values respectively
Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm
-3) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK a0 g cm
-3 a1 g cm
-3 a2 g cm
-3 a3 g cm
-3
29315 11248 00455 -00638 0024 0000840
29815 11219 00447 -00617 00217 0000800
30315 1119 00439 -00596 00195 0000764
30815 11161 00431 -00575 00173 0000732
31315 11132 00422 -00554 00152 0000704
31815 11103 00413 -00533 00132 0000680
32315 11075 00403 -00512 00112 0000660
32815 11046 00393 -00492 00093 0000640
33315 11018 00382 -00471 00074 0000625
33815 10989 00372 -0045 00055 0000613
34315 10961 0036 -0043 00037 0000606
34815 10933 00349 -00409 0002 0000596
35315 10905 00337 -00389 00003 0000592
a ρ = a0 + a1 x1 + a2 x1
2 + a3 x1
3
As can be seen from the Table 1 the value of the density decreases with increasing temperature
eventhough the variation is very small If the variation of the density with the temperature is
considered as linear then the change in the calculated thermal expansion coefficient values becomes
nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was
used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]
(2) binary system
ρ = b0 + b1 T + b2 T2 (3)
where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation
coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)
Excess thermodynamic properties are of great importance for understanding the nature of
molecular interaction in binary mixtures The excess molar volume E
mV which is the difference
between the real and ideal mixing behaviors is defined by
m m 1 1 2 2 E o o
V V xV x V (4)
where Vm represents the volume of a mixture containing one mole of (PEG200 +
[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2
([PyrMB][BuSO4]) respectively and V10 and V2
0 are the molar volumes of the pure components The
Int J Electrochem Sci Vol 8 2013
5073
excess molar volumes of mixtures over the entire composition range were calculated from our
measurements of density according to the following equation
Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat
PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]
(2)
x1 b0 b1 b2
0 1326 -000077105 00000003 000003
01452 1301 -0000588 0 000023
01942 1304 -0000593 0 000032
02912 131 -0000604 0 000047
03897 1315 -0000613 0 000009
04893 1318 -0000621 0 000034
05890 1319 -0000629 0 000045
06903 132 -0000639 0 000046
07922 1325 -0000658 0 000036
08958 1335 -0000694 0 000030
1 1405 -000108 000000051 000112
Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and
fitted curves using the Redlich-Kister parameters
1 1 2 2 1 1 2 2m
1 2
E
Vx M x M x M x M
(5)
where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture
respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E
mV
values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole
x1
00 02 04 06 08 10
Vm
E
cm
3 m
ol-1
-20
-15
-10
-05
00
30315 K
31315 K
32315 K
33315 K
Int J Electrochem Sci Vol 8 2013
5074
fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the
binary system is mainly concerned with the weak chemical interactions the physical and structural
characteristics of the system components If the chemical or nonchemical interaction of the same
components is the dominant way of the interaction the excess volume of the mixture should be
positive If the molecules of the components have a more effective packing in the mixture than that in
the pure component that is the attracting interaction between the molecules of two components is the
dominant way the excess molar volume of the binary system should be negative [66] As shown in
Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the
entire composition range the minimum of E
mV is reached at a mole fraction of PEG200 near x1 = 04
and the absolute values of the excess volume increase with increasing temperature The molar volume
for [PyrMB][BuSO4] is 26243 cm3 mol
-1 at T = 29315 K which is greater than the molar volumes of
PEG200 (17681 cm3 mol
-1) at T = 29315 K The large difference between molar volumes of the
molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic
molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids
in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)
oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar
excess volumes
32 Volume expansivity and excess volume expansivity
Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were
also used to derive the coefficient of thermal expansion From the relationship of vs T the volume
expansivity (coefficient of thermal expansion) α is defined as
1 1
( ) ( )p p
V
TV T
(6)
where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and
PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion
coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature
and increases with increasing mole fraction of the PEG200
The corresponding excess function (excess volume expansivity) was calculated using
E id id
1 1 2 2 (7)
where id
1 is an ideal volume fraction given by the following relation
1 m11
1 m1 2 m2
id xV
xV x V
(8)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
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5083
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(2011) 874
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(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
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4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5069
22 1-Butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])
Dibutyl sulfate (757 g 360 mmol) was added dropwise to a solution of equal molar amounts of
1-methylpyrrolidine (3065 g 360 mmol) in 200 mL toluene and then cooled in an ice-bath under
nitrogen at a rate that maintained the reaction temperature below 31315 K (highly exothermic
reaction) The reaction mixture was stirred at room temperature for 4h After the reaction stopped the
upper organic phase of the resulting mixture was decanted and the lower ionic liquid phase was
washed with ethyl acetate (4 x 70 mL) After the last washing the remaining ethyl acetate was
removed by rotavapor under reduced pressure The IL obtained was dried by heating at (34315 to
35315) K and stirring under a high vacuum (2 10-1
Pa) for 48 h In order to reduce the water content
to negligible values (lower than 003 mass ) a vacuum (2 x 10-1
Pa) and moderate temperature
(34315 K) were applied to the IL for 2 days The IL was kept in bottles under an inert gas The
structure of [PyrMB][BuSO4] is shown in Figure 1
Yield 91 1H NMR (300 MHz D2O ppm) 395 (t 2H -CH2SO4) 338 (m 4H N-CH2-)
321 (m 2H N-CH2-) 292 (s 3H N-CH3) 210 (m 4H N-CH2CH2-) 167 (m 2H -CH2CH2SO4)
155 (m 2H N-CH2CH2-) 128 (m 4H N-CH2CH2CH2- and -CH2CH2CH2SO4) 082 (m 6H N-
CH2CH2CH2CH3 and CH3CH2CH2CH2SO4) Elem Anal Calcd for C13H29NO4S C 5285 H 989
N 474 Found C 5268 H 979 N 465
NC4H9SO4
Figure 1 Molecular structure of 1-butyl-1-methylpyrrolidinium butyl sulfate ([PyrMB][BuSO4])
23 Measurements
The conductivity () of the ionic liquids was systematically measured with a conductivity
meter (LF 340 WTW Germany) and a standard conductivity cell (TetraCon 325 WTW Germany)
The cell constant was determined by calibration after each sample measurement using an aqueous 001
M KCl solution The density of the ILs was measured with a dilatometer which was calibrated by
measuring the density of neat glycerin at 30 40 50 60 70 and 80 oC The dilatometer was placed in a
thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K
To measure density IL or a binary mixture was placed into the dilatometer up to the mark the top of
the capillary tube (located on the top of the dilatometer) was sealed and the dilatometer (with capillary
tube) was placed into a temperature bath for 10 min to allow the temperature to equilibrate The main
interval between the two marks in the capillary tube was 001 cm3 and the minor interval between two
marks was 0001 cm3 From the correction coefficient of glycerin in capillary tube at various
temperatures we can calculate the density of neat IL or binary system by the expanded volume of
liquid in the capillary tube at various temperatures Each sample was measured at least three times to
determine an average value and the values of the density were plusmn00001 gmL The viscosity (η) of the
Int J Electrochem Sci Vol 8 2013
5070
IL was measured using a calibrated modified Ostwald viscometer (Cannon-Fenske glass capillary
viscometers CFRU 9721-A50) The viscometer capillary diameter was 12 mm as measured using a
caliper (model No PD-153) with an accuracy of plusmn 002 mm The viscometer was placed in a
thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K
The flow time was measured using a stopwatch with a resolution of 001 s For each IL the
experimental viscosity was obtained by averaging three to five flow time measurements The water
content of synthesized IL [PyrMB][BuSO4] was determined using the KarlndashFischer method the
content was below 300 ppm The nuclear magnetic resonance (NMR) spectra of the synthesized IL
were recorded on a BRUKER AV300 spectrometer and calibrated with tetramethylsilane (TMS) as the
internal reference
3 RESULTS AND DISCUSSION
31 Density and excess molar volume
The densities of neat IL [PyrMB][BuSO4] neat PEG200 and PEG200 (1) + [PyrMB][BuSO4]
(2) binary mixture over the temperature range (29315 to 35315) K and at atmospheric pressure are
presented in Table 1 and Figure 2 As shown in Figure 2 the trend of density for the binary system
with respect to temperature was decreased with increasing temperature The variations of the densities
with concentration at the different temperatures studied are shown in Figure 3 from analysis of the
data it was found that the densities depend more strongly on the mole fraction of PEG200 in the
mixture than on temperature
Figure 2 ρ vs T plot of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system
A third-order polynomial was found to satisfactorily correlate the change of density with various
compositions
T K
290 300 310 320 330 340 350 360
g
cm
-3
109
110
111
112
113
114
x1 = 00000
x1 = 01452
x1 = 01942
x1 = 02912
x1 = 03897
x1 = 04893
x1 = 05890
x1 = 06903
x1 = 07922
x1 = 08958
Int J Electrochem Sci Vol 8 2013
5071
ρ = a0 + a1 x1 + a2 x12 + a3 x1
3 (1)
where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit
parameters are listed in Table 2 for the mixtures
Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)
+ [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ρg middotcm-3
0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912
01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936
01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949
02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972
03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984
04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984
05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973
06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948
07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923
08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896
1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860
E
mV cm3 mol-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003
01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375
02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952
03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061
04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201
05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459
06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997
07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903
08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration
at various temperatures
The correlation constants for Eq (1) were established using the least square method and are
presented in Table 2 along with the standard deviation estimated using the following equation
2
exp cal 1 2( - )
[ ]Z Z
n
(2)
x1
00 02 04 06 08 10
g c
m-3
106
108
110
112
114
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5072
where n is the number of experimental points and Zexp and Zcal are the experimental and
calculated values respectively
Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm
-3) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK a0 g cm
-3 a1 g cm
-3 a2 g cm
-3 a3 g cm
-3
29315 11248 00455 -00638 0024 0000840
29815 11219 00447 -00617 00217 0000800
30315 1119 00439 -00596 00195 0000764
30815 11161 00431 -00575 00173 0000732
31315 11132 00422 -00554 00152 0000704
31815 11103 00413 -00533 00132 0000680
32315 11075 00403 -00512 00112 0000660
32815 11046 00393 -00492 00093 0000640
33315 11018 00382 -00471 00074 0000625
33815 10989 00372 -0045 00055 0000613
34315 10961 0036 -0043 00037 0000606
34815 10933 00349 -00409 0002 0000596
35315 10905 00337 -00389 00003 0000592
a ρ = a0 + a1 x1 + a2 x1
2 + a3 x1
3
As can be seen from the Table 1 the value of the density decreases with increasing temperature
eventhough the variation is very small If the variation of the density with the temperature is
considered as linear then the change in the calculated thermal expansion coefficient values becomes
nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was
used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]
(2) binary system
ρ = b0 + b1 T + b2 T2 (3)
where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation
coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)
Excess thermodynamic properties are of great importance for understanding the nature of
molecular interaction in binary mixtures The excess molar volume E
mV which is the difference
between the real and ideal mixing behaviors is defined by
m m 1 1 2 2 E o o
V V xV x V (4)
where Vm represents the volume of a mixture containing one mole of (PEG200 +
[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2
([PyrMB][BuSO4]) respectively and V10 and V2
0 are the molar volumes of the pure components The
Int J Electrochem Sci Vol 8 2013
5073
excess molar volumes of mixtures over the entire composition range were calculated from our
measurements of density according to the following equation
Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat
PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]
(2)
x1 b0 b1 b2
0 1326 -000077105 00000003 000003
01452 1301 -0000588 0 000023
01942 1304 -0000593 0 000032
02912 131 -0000604 0 000047
03897 1315 -0000613 0 000009
04893 1318 -0000621 0 000034
05890 1319 -0000629 0 000045
06903 132 -0000639 0 000046
07922 1325 -0000658 0 000036
08958 1335 -0000694 0 000030
1 1405 -000108 000000051 000112
Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and
fitted curves using the Redlich-Kister parameters
1 1 2 2 1 1 2 2m
1 2
E
Vx M x M x M x M
(5)
where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture
respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E
mV
values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole
x1
00 02 04 06 08 10
Vm
E
cm
3 m
ol-1
-20
-15
-10
-05
00
30315 K
31315 K
32315 K
33315 K
Int J Electrochem Sci Vol 8 2013
5074
fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the
binary system is mainly concerned with the weak chemical interactions the physical and structural
characteristics of the system components If the chemical or nonchemical interaction of the same
components is the dominant way of the interaction the excess volume of the mixture should be
positive If the molecules of the components have a more effective packing in the mixture than that in
the pure component that is the attracting interaction between the molecules of two components is the
dominant way the excess molar volume of the binary system should be negative [66] As shown in
Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the
entire composition range the minimum of E
mV is reached at a mole fraction of PEG200 near x1 = 04
and the absolute values of the excess volume increase with increasing temperature The molar volume
for [PyrMB][BuSO4] is 26243 cm3 mol
-1 at T = 29315 K which is greater than the molar volumes of
PEG200 (17681 cm3 mol
-1) at T = 29315 K The large difference between molar volumes of the
molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic
molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids
in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)
oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar
excess volumes
32 Volume expansivity and excess volume expansivity
Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were
also used to derive the coefficient of thermal expansion From the relationship of vs T the volume
expansivity (coefficient of thermal expansion) α is defined as
1 1
( ) ( )p p
V
TV T
(6)
where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and
PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion
coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature
and increases with increasing mole fraction of the PEG200
The corresponding excess function (excess volume expansivity) was calculated using
E id id
1 1 2 2 (7)
where id
1 is an ideal volume fraction given by the following relation
1 m11
1 m1 2 m2
id xV
xV x V
(8)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
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(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
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Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
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(2010) 853
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4381
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Int J Electrochem Sci 7 (2012) 6998
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(2012) 965
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43 (2012) 573
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Int J Electrochem Sci 7 (2012) 7547
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(2012) 2633
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Electrochem Sci 7 (2012) 1908
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4756
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Chem Soc 22 (2011) 780
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(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
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Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
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6085
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Norouzi Int J Electrochem Sci 6 (2011) 739
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Int J Electrochem Sci 6 (2011) 717
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Chem Soc 8 (2011) 149
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(2012) 2047
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Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5070
IL was measured using a calibrated modified Ostwald viscometer (Cannon-Fenske glass capillary
viscometers CFRU 9721-A50) The viscometer capillary diameter was 12 mm as measured using a
caliper (model No PD-153) with an accuracy of plusmn 002 mm The viscometer was placed in a
thermostatic water bath (TV-4000 TAMSON) whose temperature was regulated to within plusmn 001 K
The flow time was measured using a stopwatch with a resolution of 001 s For each IL the
experimental viscosity was obtained by averaging three to five flow time measurements The water
content of synthesized IL [PyrMB][BuSO4] was determined using the KarlndashFischer method the
content was below 300 ppm The nuclear magnetic resonance (NMR) spectra of the synthesized IL
were recorded on a BRUKER AV300 spectrometer and calibrated with tetramethylsilane (TMS) as the
internal reference
3 RESULTS AND DISCUSSION
31 Density and excess molar volume
The densities of neat IL [PyrMB][BuSO4] neat PEG200 and PEG200 (1) + [PyrMB][BuSO4]
(2) binary mixture over the temperature range (29315 to 35315) K and at atmospheric pressure are
presented in Table 1 and Figure 2 As shown in Figure 2 the trend of density for the binary system
with respect to temperature was decreased with increasing temperature The variations of the densities
with concentration at the different temperatures studied are shown in Figure 3 from analysis of the
data it was found that the densities depend more strongly on the mole fraction of PEG200 in the
mixture than on temperature
Figure 2 ρ vs T plot of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system
A third-order polynomial was found to satisfactorily correlate the change of density with various
compositions
T K
290 300 310 320 330 340 350 360
g
cm
-3
109
110
111
112
113
114
x1 = 00000
x1 = 01452
x1 = 01942
x1 = 02912
x1 = 03897
x1 = 04893
x1 = 05890
x1 = 06903
x1 = 07922
x1 = 08958
Int J Electrochem Sci Vol 8 2013
5071
ρ = a0 + a1 x1 + a2 x12 + a3 x1
3 (1)
where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit
parameters are listed in Table 2 for the mixtures
Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)
+ [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ρg middotcm-3
0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912
01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936
01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949
02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972
03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984
04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984
05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973
06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948
07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923
08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896
1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860
E
mV cm3 mol-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003
01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375
02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952
03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061
04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201
05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459
06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997
07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903
08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration
at various temperatures
The correlation constants for Eq (1) were established using the least square method and are
presented in Table 2 along with the standard deviation estimated using the following equation
2
exp cal 1 2( - )
[ ]Z Z
n
(2)
x1
00 02 04 06 08 10
g c
m-3
106
108
110
112
114
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5072
where n is the number of experimental points and Zexp and Zcal are the experimental and
calculated values respectively
Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm
-3) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK a0 g cm
-3 a1 g cm
-3 a2 g cm
-3 a3 g cm
-3
29315 11248 00455 -00638 0024 0000840
29815 11219 00447 -00617 00217 0000800
30315 1119 00439 -00596 00195 0000764
30815 11161 00431 -00575 00173 0000732
31315 11132 00422 -00554 00152 0000704
31815 11103 00413 -00533 00132 0000680
32315 11075 00403 -00512 00112 0000660
32815 11046 00393 -00492 00093 0000640
33315 11018 00382 -00471 00074 0000625
33815 10989 00372 -0045 00055 0000613
34315 10961 0036 -0043 00037 0000606
34815 10933 00349 -00409 0002 0000596
35315 10905 00337 -00389 00003 0000592
a ρ = a0 + a1 x1 + a2 x1
2 + a3 x1
3
As can be seen from the Table 1 the value of the density decreases with increasing temperature
eventhough the variation is very small If the variation of the density with the temperature is
considered as linear then the change in the calculated thermal expansion coefficient values becomes
nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was
used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]
(2) binary system
ρ = b0 + b1 T + b2 T2 (3)
where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation
coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)
Excess thermodynamic properties are of great importance for understanding the nature of
molecular interaction in binary mixtures The excess molar volume E
mV which is the difference
between the real and ideal mixing behaviors is defined by
m m 1 1 2 2 E o o
V V xV x V (4)
where Vm represents the volume of a mixture containing one mole of (PEG200 +
[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2
([PyrMB][BuSO4]) respectively and V10 and V2
0 are the molar volumes of the pure components The
Int J Electrochem Sci Vol 8 2013
5073
excess molar volumes of mixtures over the entire composition range were calculated from our
measurements of density according to the following equation
Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat
PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]
(2)
x1 b0 b1 b2
0 1326 -000077105 00000003 000003
01452 1301 -0000588 0 000023
01942 1304 -0000593 0 000032
02912 131 -0000604 0 000047
03897 1315 -0000613 0 000009
04893 1318 -0000621 0 000034
05890 1319 -0000629 0 000045
06903 132 -0000639 0 000046
07922 1325 -0000658 0 000036
08958 1335 -0000694 0 000030
1 1405 -000108 000000051 000112
Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and
fitted curves using the Redlich-Kister parameters
1 1 2 2 1 1 2 2m
1 2
E
Vx M x M x M x M
(5)
where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture
respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E
mV
values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole
x1
00 02 04 06 08 10
Vm
E
cm
3 m
ol-1
-20
-15
-10
-05
00
30315 K
31315 K
32315 K
33315 K
Int J Electrochem Sci Vol 8 2013
5074
fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the
binary system is mainly concerned with the weak chemical interactions the physical and structural
characteristics of the system components If the chemical or nonchemical interaction of the same
components is the dominant way of the interaction the excess volume of the mixture should be
positive If the molecules of the components have a more effective packing in the mixture than that in
the pure component that is the attracting interaction between the molecules of two components is the
dominant way the excess molar volume of the binary system should be negative [66] As shown in
Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the
entire composition range the minimum of E
mV is reached at a mole fraction of PEG200 near x1 = 04
and the absolute values of the excess volume increase with increasing temperature The molar volume
for [PyrMB][BuSO4] is 26243 cm3 mol
-1 at T = 29315 K which is greater than the molar volumes of
PEG200 (17681 cm3 mol
-1) at T = 29315 K The large difference between molar volumes of the
molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic
molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids
in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)
oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar
excess volumes
32 Volume expansivity and excess volume expansivity
Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were
also used to derive the coefficient of thermal expansion From the relationship of vs T the volume
expansivity (coefficient of thermal expansion) α is defined as
1 1
( ) ( )p p
V
TV T
(6)
where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and
PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion
coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature
and increases with increasing mole fraction of the PEG200
The corresponding excess function (excess volume expansivity) was calculated using
E id id
1 1 2 2 (7)
where id
1 is an ideal volume fraction given by the following relation
1 m11
1 m1 2 m2
id xV
xV x V
(8)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
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43 (2012) 573
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26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
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Electrochem Sci 7 (2012) 1908
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30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
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32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
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35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
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Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
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43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
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5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5071
ρ = a0 + a1 x1 + a2 x12 + a3 x1
3 (1)
where x1 is the mole fractions of PEG200 and a0 a1 a2 and a3 refer to the fit coefficients Fit
parameters are listed in Table 2 for the mixtures
Table 1 Experimental density () and excess molar volume (VmE) for the binary system PEG200 (1)
+ [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ρg middotcm-3
0 11258 11228 11199 11169 11140 11111 11082 11053 11025 10996 10968 10940 10912
01452 11288 11259 11230 11200 11171 11142 11112 11083 11053 11024 10995 10965 10936
01942 11305 11275 11245 11216 11186 11157 11127 11097 11068 11038 11008 10979 10949
02912 11334 11304 11274 11243 11213 11183 11153 11123 11092 11062 11032 11002 10972
03897 11352 11321 11291 11260 11229 11199 11168 11138 11107 11076 11046 11015 10984
04893 11356 11325 11294 11263 11232 11201 11170 11139 11108 11077 11046 11015 10984
05890 11350 11319 11288 11256 11225 11193 11162 11131 11099 11068 11036 11005 10973
06903 11331 11299 11267 11235 11203 11172 11140 11108 11076 11044 11012 10980 10948
07922 11318 11285 11252 11219 11186 11153 11120 11087 11054 11021 10988 10956 10923
08958 11312 11278 11243 11208 11174 11139 11104 11070 11035 11000 10966 10931 10896
1 11312 11273 11234 11195 11157 11119 11081 11044 11007 10970 10933 10896 10860
E
mV cm3 mol-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -05572 -05884 -06161 -06404 -06613 -06787 -06925 -07028 -07096 -07127 -07123 -07081 -07003
01942 -08575 -08917 -09225 -09498 -09737 -09942 -10111 -10245 -10343 -10406 -10432 -10422 -10375
02912 -13539 -13931 -14289 -14614 -14903 -15159 -15379 -15564 -15714 -15828 -15906 -15947 -15952
03897 -15730 -16197 -16630 -17029 -17394 -17726 -18022 -18284 -18511 -18702 -18858 -18978 -19061
04893 -14983 -15521 -16026 -16498 -16936 -17341 -17711 -18047 -18348 -18615 -18846 -19041 -19201
05890 -12361 -12970 -13547 -14090 -14601 -15078 -15522 -15931 -16306 -16647 -16953 -17224 -17459
06903 -07359 -08013 -08634 -09222 -09777 -10300 -10788 -11243 -11663 -12049 -12400 -12717 -12997
07922 -03606 -04235 -04831 -05394 -05923 -06418 -06878 -07304 -07695 -08051 -08371 -08655 -08903
08958 -01410 -01915 -02384 -02818 -03216 -03578 -03903 -04192 -04443 -04656 -04832 -04969 -05068
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 3 ρ of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a function of concentration
at various temperatures
The correlation constants for Eq (1) were established using the least square method and are
presented in Table 2 along with the standard deviation estimated using the following equation
2
exp cal 1 2( - )
[ ]Z Z
n
(2)
x1
00 02 04 06 08 10
g c
m-3
106
108
110
112
114
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5072
where n is the number of experimental points and Zexp and Zcal are the experimental and
calculated values respectively
Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm
-3) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK a0 g cm
-3 a1 g cm
-3 a2 g cm
-3 a3 g cm
-3
29315 11248 00455 -00638 0024 0000840
29815 11219 00447 -00617 00217 0000800
30315 1119 00439 -00596 00195 0000764
30815 11161 00431 -00575 00173 0000732
31315 11132 00422 -00554 00152 0000704
31815 11103 00413 -00533 00132 0000680
32315 11075 00403 -00512 00112 0000660
32815 11046 00393 -00492 00093 0000640
33315 11018 00382 -00471 00074 0000625
33815 10989 00372 -0045 00055 0000613
34315 10961 0036 -0043 00037 0000606
34815 10933 00349 -00409 0002 0000596
35315 10905 00337 -00389 00003 0000592
a ρ = a0 + a1 x1 + a2 x1
2 + a3 x1
3
As can be seen from the Table 1 the value of the density decreases with increasing temperature
eventhough the variation is very small If the variation of the density with the temperature is
considered as linear then the change in the calculated thermal expansion coefficient values becomes
nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was
used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]
(2) binary system
ρ = b0 + b1 T + b2 T2 (3)
where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation
coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)
Excess thermodynamic properties are of great importance for understanding the nature of
molecular interaction in binary mixtures The excess molar volume E
mV which is the difference
between the real and ideal mixing behaviors is defined by
m m 1 1 2 2 E o o
V V xV x V (4)
where Vm represents the volume of a mixture containing one mole of (PEG200 +
[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2
([PyrMB][BuSO4]) respectively and V10 and V2
0 are the molar volumes of the pure components The
Int J Electrochem Sci Vol 8 2013
5073
excess molar volumes of mixtures over the entire composition range were calculated from our
measurements of density according to the following equation
Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat
PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]
(2)
x1 b0 b1 b2
0 1326 -000077105 00000003 000003
01452 1301 -0000588 0 000023
01942 1304 -0000593 0 000032
02912 131 -0000604 0 000047
03897 1315 -0000613 0 000009
04893 1318 -0000621 0 000034
05890 1319 -0000629 0 000045
06903 132 -0000639 0 000046
07922 1325 -0000658 0 000036
08958 1335 -0000694 0 000030
1 1405 -000108 000000051 000112
Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and
fitted curves using the Redlich-Kister parameters
1 1 2 2 1 1 2 2m
1 2
E
Vx M x M x M x M
(5)
where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture
respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E
mV
values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole
x1
00 02 04 06 08 10
Vm
E
cm
3 m
ol-1
-20
-15
-10
-05
00
30315 K
31315 K
32315 K
33315 K
Int J Electrochem Sci Vol 8 2013
5074
fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the
binary system is mainly concerned with the weak chemical interactions the physical and structural
characteristics of the system components If the chemical or nonchemical interaction of the same
components is the dominant way of the interaction the excess volume of the mixture should be
positive If the molecules of the components have a more effective packing in the mixture than that in
the pure component that is the attracting interaction between the molecules of two components is the
dominant way the excess molar volume of the binary system should be negative [66] As shown in
Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the
entire composition range the minimum of E
mV is reached at a mole fraction of PEG200 near x1 = 04
and the absolute values of the excess volume increase with increasing temperature The molar volume
for [PyrMB][BuSO4] is 26243 cm3 mol
-1 at T = 29315 K which is greater than the molar volumes of
PEG200 (17681 cm3 mol
-1) at T = 29315 K The large difference between molar volumes of the
molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic
molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids
in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)
oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar
excess volumes
32 Volume expansivity and excess volume expansivity
Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were
also used to derive the coefficient of thermal expansion From the relationship of vs T the volume
expansivity (coefficient of thermal expansion) α is defined as
1 1
( ) ( )p p
V
TV T
(6)
where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and
PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion
coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature
and increases with increasing mole fraction of the PEG200
The corresponding excess function (excess volume expansivity) was calculated using
E id id
1 1 2 2 (7)
where id
1 is an ideal volume fraction given by the following relation
1 m11
1 m1 2 m2
id xV
xV x V
(8)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5072
where n is the number of experimental points and Zexp and Zcal are the experimental and
calculated values respectively
Table 2 Coefficients of polynomiala for the correlation of the density (ρgmiddotcm
-3) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK a0 g cm
-3 a1 g cm
-3 a2 g cm
-3 a3 g cm
-3
29315 11248 00455 -00638 0024 0000840
29815 11219 00447 -00617 00217 0000800
30315 1119 00439 -00596 00195 0000764
30815 11161 00431 -00575 00173 0000732
31315 11132 00422 -00554 00152 0000704
31815 11103 00413 -00533 00132 0000680
32315 11075 00403 -00512 00112 0000660
32815 11046 00393 -00492 00093 0000640
33315 11018 00382 -00471 00074 0000625
33815 10989 00372 -0045 00055 0000613
34315 10961 0036 -0043 00037 0000606
34815 10933 00349 -00409 0002 0000596
35315 10905 00337 -00389 00003 0000592
a ρ = a0 + a1 x1 + a2 x1
2 + a3 x1
3
As can be seen from the Table 1 the value of the density decreases with increasing temperature
eventhough the variation is very small If the variation of the density with the temperature is
considered as linear then the change in the calculated thermal expansion coefficient values becomes
nearly constant In order to have an improved accuracy a second order polynomial of the eqn (3) was
used to correlate the variation of the density with the temperature for PEG200 (1) + [PyrMB][BuSO4]
(2) binary system
ρ = b0 + b1 T + b2 T2 (3)
where T is the temperature and b0 b1 and b2 are the correlation coefficients The correlation
coefficients are listed in Table 3 together with the standard deviations (σ) calculated using Eq (2)
Excess thermodynamic properties are of great importance for understanding the nature of
molecular interaction in binary mixtures The excess molar volume E
mV which is the difference
between the real and ideal mixing behaviors is defined by
m m 1 1 2 2 E o o
V V xV x V (4)
where Vm represents the volume of a mixture containing one mole of (PEG200 +
[PyrMB][BuSO4]) x1 and x2 are the mole fractions of components 1 (PEG200) and 2
([PyrMB][BuSO4]) respectively and V10 and V2
0 are the molar volumes of the pure components The
Int J Electrochem Sci Vol 8 2013
5073
excess molar volumes of mixtures over the entire composition range were calculated from our
measurements of density according to the following equation
Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat
PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]
(2)
x1 b0 b1 b2
0 1326 -000077105 00000003 000003
01452 1301 -0000588 0 000023
01942 1304 -0000593 0 000032
02912 131 -0000604 0 000047
03897 1315 -0000613 0 000009
04893 1318 -0000621 0 000034
05890 1319 -0000629 0 000045
06903 132 -0000639 0 000046
07922 1325 -0000658 0 000036
08958 1335 -0000694 0 000030
1 1405 -000108 000000051 000112
Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and
fitted curves using the Redlich-Kister parameters
1 1 2 2 1 1 2 2m
1 2
E
Vx M x M x M x M
(5)
where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture
respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E
mV
values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole
x1
00 02 04 06 08 10
Vm
E
cm
3 m
ol-1
-20
-15
-10
-05
00
30315 K
31315 K
32315 K
33315 K
Int J Electrochem Sci Vol 8 2013
5074
fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the
binary system is mainly concerned with the weak chemical interactions the physical and structural
characteristics of the system components If the chemical or nonchemical interaction of the same
components is the dominant way of the interaction the excess volume of the mixture should be
positive If the molecules of the components have a more effective packing in the mixture than that in
the pure component that is the attracting interaction between the molecules of two components is the
dominant way the excess molar volume of the binary system should be negative [66] As shown in
Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the
entire composition range the minimum of E
mV is reached at a mole fraction of PEG200 near x1 = 04
and the absolute values of the excess volume increase with increasing temperature The molar volume
for [PyrMB][BuSO4] is 26243 cm3 mol
-1 at T = 29315 K which is greater than the molar volumes of
PEG200 (17681 cm3 mol
-1) at T = 29315 K The large difference between molar volumes of the
molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic
molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids
in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)
oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar
excess volumes
32 Volume expansivity and excess volume expansivity
Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were
also used to derive the coefficient of thermal expansion From the relationship of vs T the volume
expansivity (coefficient of thermal expansion) α is defined as
1 1
( ) ( )p p
V
TV T
(6)
where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and
PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion
coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature
and increases with increasing mole fraction of the PEG200
The corresponding excess function (excess volume expansivity) was calculated using
E id id
1 1 2 2 (7)
where id
1 is an ideal volume fraction given by the following relation
1 m11
1 m1 2 m2
id xV
xV x V
(8)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5073
excess molar volumes of mixtures over the entire composition range were calculated from our
measurements of density according to the following equation
Table 3 The adjustable parameters of density (ρ = b0 + b1 T + b2 T2) at various temperature for neat
PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system PEG200 (1) + [PyrMB][BuSO4]
(2)
x1 b0 b1 b2
0 1326 -000077105 00000003 000003
01452 1301 -0000588 0 000023
01942 1304 -0000593 0 000032
02912 131 -0000604 0 000047
03897 1315 -0000613 0 000009
04893 1318 -0000621 0 000034
05890 1319 -0000629 0 000045
06903 132 -0000639 0 000046
07922 1325 -0000658 0 000036
08958 1335 -0000694 0 000030
1 1405 -000108 000000051 000112
Figure 4 Excess molar volumes for the binary system PEG200 (1) + [PyrMB][BuSO4] (2) and
fitted curves using the Redlich-Kister parameters
1 1 2 2 1 1 2 2m
1 2
E
Vx M x M x M x M
(5)
where ρ1 ρ2 and ρ are the densities of neat PEG200 [PyrMB][BuSO4] and their mixture
respectively M1 and M2 are the molar masses of PEG200 and [PyrMB][BuSO4] respectively The E
mV
values of mixtures are summarized in Table 1 The excess molar volumes of mixtures versus the mole
x1
00 02 04 06 08 10
Vm
E
cm
3 m
ol-1
-20
-15
-10
-05
00
30315 K
31315 K
32315 K
33315 K
Int J Electrochem Sci Vol 8 2013
5074
fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the
binary system is mainly concerned with the weak chemical interactions the physical and structural
characteristics of the system components If the chemical or nonchemical interaction of the same
components is the dominant way of the interaction the excess volume of the mixture should be
positive If the molecules of the components have a more effective packing in the mixture than that in
the pure component that is the attracting interaction between the molecules of two components is the
dominant way the excess molar volume of the binary system should be negative [66] As shown in
Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the
entire composition range the minimum of E
mV is reached at a mole fraction of PEG200 near x1 = 04
and the absolute values of the excess volume increase with increasing temperature The molar volume
for [PyrMB][BuSO4] is 26243 cm3 mol
-1 at T = 29315 K which is greater than the molar volumes of
PEG200 (17681 cm3 mol
-1) at T = 29315 K The large difference between molar volumes of the
molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic
molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids
in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)
oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar
excess volumes
32 Volume expansivity and excess volume expansivity
Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were
also used to derive the coefficient of thermal expansion From the relationship of vs T the volume
expansivity (coefficient of thermal expansion) α is defined as
1 1
( ) ( )p p
V
TV T
(6)
where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and
PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion
coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature
and increases with increasing mole fraction of the PEG200
The corresponding excess function (excess volume expansivity) was calculated using
E id id
1 1 2 2 (7)
where id
1 is an ideal volume fraction given by the following relation
1 m11
1 m1 2 m2
id xV
xV x V
(8)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
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5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
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Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5074
fraction of PEG200 from 29315 to 35315 K are plotted in Figure 4 The excess molar volume of the
binary system is mainly concerned with the weak chemical interactions the physical and structural
characteristics of the system components If the chemical or nonchemical interaction of the same
components is the dominant way of the interaction the excess volume of the mixture should be
positive If the molecules of the components have a more effective packing in the mixture than that in
the pure component that is the attracting interaction between the molecules of two components is the
dominant way the excess molar volume of the binary system should be negative [66] As shown in
Figure 4 the excess molar volumes are asymmetric and negative for all of the systems studied over the
entire composition range the minimum of E
mV is reached at a mole fraction of PEG200 near x1 = 04
and the absolute values of the excess volume increase with increasing temperature The molar volume
for [PyrMB][BuSO4] is 26243 cm3 mol
-1 at T = 29315 K which is greater than the molar volumes of
PEG200 (17681 cm3 mol
-1) at T = 29315 K The large difference between molar volumes of the
molecular liquid and [PyrMB][BuSO4] indicates that it is possible that the relatively small organic
molecules fit into the interstices upon mixing Therefore the filling effect of organic molecular liquids
in the interstices of ionic liquids and the ionndashdipole interactions between poly(ethylene glycol)
oligomer and the butylsulfate-based ionic liquids all contribute to the negative values of the molar
excess volumes
32 Volume expansivity and excess volume expansivity
Density results for the PEG200 and [PyrMB][BuSO4] binary system studied in current work were
also used to derive the coefficient of thermal expansion From the relationship of vs T the volume
expansivity (coefficient of thermal expansion) α is defined as
1 1
( ) ( )p p
V
TV T
(6)
where subscript p indicates constant pressure The α values of pure [PyrMB][BuSO4] and
PEG200 and their mixture are summarized in Table 4 The values indicate that the thermal expansion
coefficient of this binary mixture (PEG200 + [PyrMB][BuSO4]) increases with increasing temperature
and increases with increasing mole fraction of the PEG200
The corresponding excess function (excess volume expansivity) was calculated using
E id id
1 1 2 2 (7)
where id
1 is an ideal volume fraction given by the following relation
1 m11
1 m1 2 m2
id xV
xV x V
(8)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
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Acta 56 (2011) 7278
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6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5075
where Vmi is the molar volume of pure component i
Table 4 Experimental volume expansivity (α) and the excess volume expansivity (αE) for the binary
system PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
104 αK-1
0 51245 51380 51516 51651 51787 51922 52058 52193 52329 52464 52600 52735 52871
01452 52053 52189 52325 52462 52600 52739 52878 53018 53159 53300 53443 53586 53730
01942 52438 52576 52715 52854 52994 53135 53276 53418 53561 53705 53850 53995 54141
02912 53299 53443 53586 53731 53877 54023 54170 54318 54466 54616 54766 54917 55069
03897 53973 54120 54268 54417 54567 54717 54869 55021 55174 55328 55483 55638 55795
04893 54667 54818 54971 55124 55278 55433 55589 55745 55903 56061 56221 56381 56542
05890 55372 55527 55683 55840 55998 56157 56317 56477 56639 56801 56965 57129 57294
06903 56358 56517 56677 56838 57000 57163 57327 57492 57657 57824 57992 58160 58330
07922 58175 58344 58515 58687 58860 59033 59208 59384 59561 59739 59918 60098 60279
08958 61313 61502 61691 61882 62074 62268 62462 62658 62855 63053 63252 63453 63655
1 66532 66763 66993 67224 67455 67685 67916 68146 68377 68607 68838 69069 69299
104 αEK-1
0 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
01452 -00762 -00772 -00782 -00792 -00800 -00808 -00815 -00822 -00827 -00832 -00837 -00840 -00843
01942 -00942 -00954 -00966 -00977 -00987 -00997 -01006 -01014 -01021 -01028 -01033 -01038 -01043
02912 -01259 -01275 -01289 -01302 -01315 -01327 -01339 -01349 -01359 -01368 -01376 -01383 -01389
03897 -01870 -01889 -01908 -01926 -01943 -01959 -01975 -01989 -02003 -02016 -02028 -02040 -02050
04893 -02576 -02600 -02623 -02646 -02668 -02689 -02709 -02728 -02746 -02764 -02780 -02796 -02811
05890 -03382 -03412 -03441 -03470 -03497 -03524 -03550 -03574 -03598 -03621 -03644 -03665 -03685
06903 -04064 -04100 -04136 -04170 -04204 -04236 -04268 -04299 -04329 -04358 -04386 -04413 -04439
07922 -04073 -04110 -04146 -04181 -04214 -04247 -04279 -04310 -04339 -04368 -04396 -04422 -04448
08958 -02968 -02998 -03026 -03053 -03079 -03104 -03128 -03151 -03172 -03192 -03211 -03228 -03245
1 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000 00000
Figure 5 Plot of excess volume expansivity αE of the PEG200 (1) + [PyrMB][BuSO4] (2) binary
system versus mole fraction x1 at various temperatures
Typical concentration dependencies of excess volume expansivity are given in Figure 5 for the
PEG200 + [PyrMB][BuSO4] binary system The values of excess thermal coefficient αE are found to
x1
00 02 04 06 08 10
10
4
E K
-1
-04
-03
-02
-01
00
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Temp
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003
2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5076
be negative over the whole composition range for the binary system at 29315 ~ 35315 K The curves
are asymmetrical with the minimum located at the IL mole fraction of about 08 In general negative
αE values indicate the presence of strong interaction between the components in the mixtures [67] The
trends observed in αE values for the present mixtures suggest the formation of H-bonding between
unlike molecules which is stronger in PEG200 + [PyrMB][BuSO4] binary system The increasing
negative αE values for PEG200 + [PyrMB][BuSO4] with increase in temperature indicate enhanced
unlike interaction between components of the mixture that is more destruction of order during mixing
contributes negatively to αE
33 Viscosity
Since ILs are more viscous than conventional solvents in most applications they can be used in
mixtures with other less viscous compounds Therefore the viscosity of pure ILs and their mixtures
with PEG oligomer (or conventional solvents) is an important property and their knowledge is
primordial for each industrial processes [6869] The measured dynamic viscosities for the neat
PEG200 neat [PyrMB][BuSO4] and PEG200 + [PyrMB][BuSO4] binary mixture as a function of
temperature over the whole composition range are shown in Figure 6 and their data are listed in Table
5 the viscosities of the mixtures decrease rapidly when PEG oligomer are added to the ionic liquid
especially at lower temperatures The fitting lines in Figure 6 were calculated with the following
fourth-order polynomial equation
= c0 + c1 x1 + c2 x12 + c3 x1
3 + c4 x1
4 (9)
where x1 is the mole fractions of PEG200 and c0 c1 c2 c3 and c4 refer to the fit coefficients
The parameters of correlation are shown in Table 6
Figure 6 Dynamic viscosity for the PEG200 (1) + [PyrMB][BuSO4] (2) binary system as a
function of mole fractions of the PEG200 at different temperatures Lines represent the
polynomial correlation
x1
00 02 04 06 08 10
mP
a s
0
200
400
600
800
1000
1200
1400
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
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2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5077
Table 5 Experimental dynamic viscosity (η) and viscosity deviation (Δη) for the binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
29315 29815 30315 30815 31315 31815 32315 32815 33315 33815 34315 34815 35315
ηmPamiddots
0 13209 9343 6745 4961 3712 2821 2176 1700 1345 1077 871 712 587
01452 5907 4362 3294 2539 1992 1589 1286 1055 876 735 623 533 460
01942 4656 3475 2656 2072 1647 1331 1091 907 763 649 557 483 422
02912 3134 2395 1870 1489 1205 991 826 697 594 512 445 390 345
03897 2367 1846 1463 1177 959 792 660 557 474 406 351 306 269
04893 1799 1396 1104 887 723 598 501 424 362 312 272 238 210
05890 1540 1194 941 753 611 502 418 351 298 255 220 191 167
06903 1185 926 736 594 485 402 336 284 242 209 181 158 139
07922 954 742 589 475 389 323 271 231 198 172 150 132 117
08958 811 639 512 415 342 285 240 204 175 151 132 116 102
1 629 505 410 337 280 235 199 170 146 126 110 97 85
ΔηmPamiddots
0 00 00 00 00 00 00 00 00 00 00 00 00 00
01452 -5475 -3698 -2530 -1751 -1221 -857 -602 -423 -295 -204 -137 -89 -54
01942 -6111 -4152 -2859 -1991 -1398 -988 -700 -496 -347 -244 -166 -110 -68
02912 -6411 -4374 -3030 -2126 -1507 -1077 -774 -558 -391 -288 -204 -142 -103
03897 -5940 -4053 -2813 -1982 -1415 -1022 -745 -547 -405 -300 -223 -166 -123
04893 -5254 -3622 -2541 -1811 -1255 -957 -708 -528 -396 -299 -227 -173 -131
05890 -4260 -2944 -2073 -1484 -1034 -796 -594 -448 -341 -262 -203 -158 -124
06903 -3340 -2316 -1636 -1176 -826 -634 -475 -360 -275 -212 -165 -129 -101
07922 -2289 -1599 -1138 -823 -579 -449 -320 -257 -197 -152 -118 -92 -72
08958 -1129 -787 -559 -404 -277 -220 -152 -126 -96 -74 -58 -45 -35
1 00 00 00 00 00 00 00 00 00 00 00 00 00
Table 6 Coefficients of polynomiala for the correlation of the viscosity ( mPa s) in function of
concentration at different temperatures of the binary systems PEG200 (1) + [PyrMB][BuSO4]
(2)
TK c0 mPa s c1 mPa s c2 mPa s c3 mPa s C4 mPa s
29315 13154 -68701 15960 -16688 63543 1075
29815 93069 -46703 10681 -11113 42269 727
30315 67211 -32185 72085 -74396 28222 497
30815 49454 -22431 48886 -49866 18828 343
31315 37016 -15772 33175 -33281 12474 238
31815 28146 -1116 22406 -21947 81322 165
32315 21713 -7923 14947 -1413 51409 114
32815 16975 -56244 97349 -870 30666 077
33315 13435 -39753 60667 -4908 16219 051
33815 10756 -27812 34718 -22519 61382 033
34315 87026 -19098 16304 -39091 -88892 021
34815 71108 -12698 32285 90904 -5763 016
35315 58636 -79728 -60345 18103 -91096 017 a = c0 + c1 x1 + c2 x1
2 + c3 x1
3 + c4 x1
4
The temperature dependence becomes distinctly nonlinear especially at high [PyrMB][BuSO4]
content The Vogel-Tammann-Fulcher (VTF) equation [70-75] suitably correlates the nonlinear
behavior as a function of the temperature not only the viscosities of the neat IL but also the viscosities
of the mixtures for the binary systems through the composition range
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003
2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5078
exp[ ]( )
o
o
B
T T
(10)
where ηo B and To are constants The parameter To is the ideal glass transition temperature which
should be slightly below the experimental glass transition temperature Tg [76] The adjustable
parameters obtained from the VTF correlation were presented in Table 7 The obtained parameters o
and B change smoothly with composition for binary mixtures
Table 7 The VTF equation parameters of viscosity ( 1 exp[ ]( )
o
o
B
T T
) and conductivity
(
exp[ ]( )
o
o
B
T T
) for neat PEG200 (x1 = 1) [PyrMB][BuSO4] (x1 = 0) and binary system
PEG200 (1) + [PyrMB][BuSO4] (2)
x1
ηo (mPa s) To (K) B (K) R2a
o (mS cm-1
) To (K) Brsquo (K) R2a
0 027 1810 9540 0999 792 1788 6854 0999
01452 026 1712 9413 0999 577 1699 6268 0999
01942 043 1788 7975 0999 401 1792 5297 0999
02912 053 1794 7264 0999 521 1662 6031 0999
03897 026 1629 8902 0999 274 1803 4381 0999
04893 023 1666 8455 0999 177 1951 3272 0999
05890 015 1648 8865 0999 216 1883 3672 0999
06903 015 1647 8572 0999 88 2174 2000 0999
07922 017 1717 7702 0999 92 2020 2578 0999
08958 012 1642 8360 0999 43 2110 2088 0999
1 014 1649 7868 0999 556 1928 9815 0999
a Correlation coefficient
The viscosities of the mixtures decrease rapidly when organic oligomers are added to the ionic
liquid this decrease is particularly evident in dilute solutions of organic oligomers in the ionic liquid
The strong coulomb interactions between the [BuSO4]- anion and [PyrMB]
+ cation are weakened upon
mixing with the polar organic oligomers which leads to a higher mobility of the ions and a lower
viscosity of the mixtures [77] This indicates that the viscosity of ILs could be therefore tuned for
several applications by adding an organic solvent or by changing temperature [78]
Due to the wide range of possible molecular interactions between the two components
deviations can occur from ideal behavior These viscosity deviations can be quantified by the viscosity
deviation Δη also known as ldquoexcess viscosityrdquo in other sources
1 1 2 2 (mPa s) x x (11)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003
2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5079
where x1 and x2 are the mole fractions of PEG200 and [PyrMB][BuSO4] respectively and 1
and 2 are the viscosities (mPa middot s) of the solution the pure solvent and the pure IL respectively
Figure 7 shows the viscosity deviations as a function of the PEG200 mole fraction composition x1 and
temperature for the PEG200 + [PyrMB][BuSO4] binary mixture The values of viscosity deviations
are compared with those obtained from the RedlichndashKister polynomial equation The viscosity
deviation for the mixture show negative deviations from ideality over the whole mole fraction range
Figure 7 also shows that the negative values of viscosity deviations decrease with increasing
temperature this can be attributed to the specific interactions in mixtures typically hydrogen bonds break-
up as the temperature increases [79] The minimum value of Δη is observed at about x1 asymp 03 and the
viscosity deviation depends on molecular interactions as well as on the size and shape of the molecules
[80]
Figure 7 Viscosity deviations Δη versus the mole fraction at various temperatures for the binary
mixture PEG200 (1) + [PyrMB][BuSO4] (2)
34 Conductivity
The experimental data of conductivity of the neat ILs [PyrMB][BuSO4] neat PEG200 and
binary system are plotted against the x1 at various temperatures in Figure 8 together with lines
calculated with the four-order polynomial equation
= d0 + d1 x1 + d2 x12 + d3 x1
3 + d4 x1
4 (12)
where x1 is the mole fractions of PEG200 and d0 d1 d2 d3 and d4 refer to the fit coefficients
The parameters of correlation are shown in Table 8 The conductivities of neat IL [PyrMB][BuSO4]
neat PEG200 and binary system at various temperatures were fitted using the VTF equation
exp[ ]
( )o
o
B
T T
(13)
x1
00 02 04 06 08 10
m
Pa s
-700
-600
-500
-400
-300
-200
-100
0
29315 K
30315 K
31315 K
32315 K
33315 K
34315 K
35315 K
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003
2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5080
where T is the absolute temperature and Brsquo and To are adjustable parameters The best-fit
mS cm-1 Brsquo (K) and To (K) parameters are given in Table 7 Neat [PyrMB][BuSO4] neat
PEG200 and binary system were very well fit by the VTF model over the temperature range studied
Figure 8 Plot of conductivity of the PEG200 (1) + [PyrMB][BuSO4] (2) binary system versus
mole fraction x1 at various temperatures
Table 8 Coefficients of polynomiala for the correlation of the conductivity ( mS cm
-1) in function
of concentration at different temperatures of the binary systems PEG200 (1) +
[PyrMB][BuSO4] (2)
TK d0 mS cm
-1 d1 mS cm
-1 d2 mS cm
-1 d3 mS cm
-1 d4 mS cm
-1
29315 02019 09622 -01679 0734 -17284 00095
29815 02588 11031 -02503 09086 -20181 00109
30315 03255 12119 -01935 08565 -21971 00125
30815 04025 13165 -01329 0767 -23477 00141
31315 04904 13712 01238 03677 -23439 00156
31815 05894 15032 -00006 04737 -25518 00171
32315 06999 15802 00743 0265 -25986 00188
32815 08221 16427 01595 00089 -26032 00208
33315 09562 16373 04858 -06207 -24165 00233
a = d0 + d1 x1 + d2 x1
2 + d3 x1
3 + d4 x1
4
As shown in Figure 8 it can be seen that the conductivity of the binary mixture increases with
increasing amount of PEG200 goes through a maximum and then goes down to the specific
conductivity of the neat PEG200 The conductivity is related to the ion mobility and the number of
charge carriers [81] At a fixed concentration the ions move faster at higher temperature due to the
relatively lower viscosity of the mixture On the other hand the composition influences both the ion
mobility and the number of charge carriers at a fixed temperature At the beginning the number of
charge and the ion mobility increase with increasing PEG oligomer composition the maximum of
conductivity is located at x1 = 059 and corresponds to a value of 171 mS cmminus 1
at 33315 K It can also
be observed that the conductivity increases as the temperature increases The higher temperature may
x1
00 02 04 06 08 10
mS
cm
-1
00
05
10
15
20
29315 K
29815 K
30315 K
30815 K
31315 K
31815 K
32315 K
32815 K
33315 K
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003
2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5081
weaken the influence of aggregation to the conductivity which suggests that a higher temperature is
better for the ILs to act as electrolytes
Table 9 RedlickndashKister fitting coefficients Ak and the standard deviation of the VE and ∆for the
binary mixture of PEG200 (1) + [PyrMB][BuSO4] (2) system
TK A0 A1 A2 A3 A4
VEcm
3 mol
-1
29315 -5979 -4906 6585 5754 -1717 002687
29815 -6200 -4760 6464 5767 -2022 002693
30315 -6408 -4612 6345 5774 -2276 002698
30815 -6602 -4461 6229 5774 -2476 002701
31315 -6782 -4310 6116 5767 -2623 002701
31815 -6948 -4155 6006 5753 -2716 002699
32315 -7100 -3999 5899 5732 -2754 002692
32815 -7239 -3840 5795 5704 -2738 002683
33315 -7363 -3679 5694 5669 -2666 002670
33815 -7472 -3515 5596 5626 -2538 002654
34315 -7568 -3350 5501 5576 -2353 002634
34815 -7648 -3182 5409 5518 -2111 002611
35315 -7714 -3011 5320 5452 -1812 002586
∆mPa s
29315 -20414 -17226 -15592 -95544 -75863 399496
29815 -14035 -11558 -10713 -62192 19493 340180
30315 -98261 -78407 -73734 -40709 58145 286725
30815 -69922 -53591 -50601 -2676 67556 235258
31315 -48876 -39537 -41051 -14118 16739 079245
31815 -36917 -25169 -22939 -11646 51047 146189
32315 -27415 -1721 -12581 -92603 21498 104339
32815 -20441 -11703 -77538 -38334 -81478 090708
33315 -15382 -67274 -31134 -47585 -18255 059539
33815 -11664 -44928 -15533 -22312 -05591 037855
34315 -89038 -24163 68654 -15007 -10347 024263
34815 -68279 -91813 23131 -10367 -18636 017759
35315 -52525 -24051 26474 15498 -85341 018640
35 Redlich-Kister Equation for Binary System
The binary excess property ( E
mV ) and deviations (Δ) at several temperatures were fitted to a
Redlich-Kister-type equation [82]
1 1 1
0
(or ) (1 ) (1 2 )j
E i
i
i
Y Y x x A x
(14)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003
2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5082
where ΔY (YE) represents E
mV (cm3 mol
minus1) and Δ
(mPa s)x1 denotes the mole fraction of
PEG200 Ai represents the polynomial coefficients and j is the degree of the polynomial expansion
The correlated results for excess molar volumes ( E
mV ) viscosity deviations (Δ) including the values
of the fitting parameters Ai together with the standard deviation σ are given in Table 9 where the
tabulated standard deviation σ [83] is defined as
2
exp cal 1 2( )
[ ]Y Y
m n
(15)
where m is the number of experimental data points and n is the number of estimated
parameters The subscripts ldquoexprdquo and ldquocalrdquo denote the values of the experimental and calculated
property respectively As shown in Table 9 the experimentally derived E
mV and Δη values were
correlated satisfactorily by the Redlich-Kister equation
4 CONCLUSIONS
This paper is a systematic characterizations of thermophysical properties for IL binary system
Density viscosity and conductivity for (PEG200 + [PyrMB][BuSO4]) binary system are presented as a
function of temperature at atmospheric pressure it was demonstrated that viscosity and conductivity
were more sensitive to the changes in PEG content or temperature than density and the viscosity and
conductivity of pure IL and (PEG200 + [PyrMB][BuSO4]) binary system at different temperature are
fitted using the VogelndashTammannndashFulcher (VTF) equation with good accuracy The excess molar
volumes excess volume expansivity and viscosity deviations show negative deviations from the ideal
solution the results are interpreted in terms of molecular interactions in the (PEG200 +
[PyrMB][BuSO4]) binary mixture The conductivity increases to a maximum value when the
concentration of PEG200 is increased and decreases after the maximum the data obtained will be
helpful for the application of the ionic liquids as electrolytes and also useful for the ionic liquids
database
ACKNOWLEDGEMENTS
The authors would like to thank the National Science Council of the Republic of China for financially
supporting this project
References
1 P Wasserscheid T Welton Ionic Liquids in Synthesis Second ed Weinheim VCH 2003
2 TY Wu IW Sun ST Gung MW Lin BK Chen HP Wang SG Su J Taiwan Inst Chem
Eng 42 (2011) 513
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5083
3 TY Wu SG Su KF Lin YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim
Acta 56 (2011) 7278
4 B Baek S Lee C Jung Int J Electrochem Sci 6 (2011) 6220
5 PN Tshibangu SN Ndwandwe ED Dikio Int J Electrochem Sci 6 (2011) 2201
6 TY Wu SG Su HP Wang IW Sun Electrochem Commun 13 (2011) 237
7 TY Wu SG Su HP Wang YC Lin ST Gung MW Lin IW Sun Electrochim Acta 56
(2011) 3209
8 IW Sun YC Lin BK Chen CW Kuo CC Chen SG Su PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 7206
9 TY Wu SG Su ST Gung MW Lin YC Lin CA Lai IW Sun Electrochim Acta 55
(2010) 4475
10 AN Soriano AM Agapito LJLI Lagumbay AR Caparanga MH Li J Taiwan Inst Chem
Eng 42 (2011) 258
11 TY Wu IW Sun ST Gung BK Chen HP Wang SG Su J Taiwan Inst Chem Eng 42
(2011) 874
12 S Ibrahim MR Johan Int J Electrochem Sci 6 (2011) 5565
13 TY Wu SG Su YC Lin HP Wang MW Lin ST Gung IW Sun Electrochim Acta 56
(2010) 853
14 H Wang LX Wu YC Lan JQ Zhao JX Lu Int J Electrochem Sci 6 (2011) 4218
15 FF Liu SQ Liu QJ Feng SX Zhuang JB Zhang P Bu Int J Electrochem Sci 7 (2012)
4381
16 HA Barham SA Brahim Y Rozita KA Mohamed Int J Electrochem Sci 6 (2011) 181
17 SK Shukla LC Murulana EE Ebenso Int J Electrochem Sci 6 (2011) 4286
18 NV Likhanova O Olivares-Xometl D Guzman-Lucero MA Dominguez-Aguilar N Nava
M Corrales-Luna MC Mendoza Int J Electrochem Sci 6 (2011) 4514
19 A Zarrouk M Messali H Zarrok R Salghi AA Ali B Hammouti SS Al-Deyab F Bentiss
Int J Electrochem Sci 7 (2012) 6998
20 BS Ali BH Ali R Yusoff MK Aroua Int J Electrochem Sci 7 (2012) 3835
21 MH Lin YJ Liu ZH Yang YB Huang ZH Sun Y He CL Ni Int J Electrochem Sci 7
(2012) 965
22 CH Su MH Chung HJ Hsieh YK Chang JC Ding HM Wu J Taiwan Inst Chem Eng
43 (2012) 573
23 H Shekaari A Kazempour J Taiwan Inst Chem Eng 43 (2012) 650
24 ZJ Wei Y Li D Thushara YX Liu QL Ren J Taiwan Inst Chem Eng 43 (2012) 363
25 GQ Zhang HW Yang JF Gao HK Zhang CB Zheng YL Cao YH Wang KQ Ding
Int J Electrochem Sci 7 (2012) 7547
26 P Norouzi MR Ganjali F Faridbod SJ Shahtaheri HA Zamani Int J Electrochem Sci 7
(2012) 2633
27 F Faridbod MR Ganjali M Hosseini P Norouzi Int J Electrochem Sci 7 (2012) 1927
28 MR Ganjali Z Rafiei-Sarmazdeh T Poursaberi SJ Shahtaheri P Norouzi Int J
Electrochem Sci 7 (2012) 1908
29 A Babaei DJ Garrett AJ Downard Int J Electrochem Sci 7 (2012) 3141
30 MR Ganjali T Alizade P Norouzi Int J Electrochem Sci 7 (2012) 4800
31 MR Ganjali T Alizade B Larijani F Faridbod P Norouzi Int J Electrochem Sci 7 (2012)
4756
32 P Norouzi B Larijani MR Ganjali Int J Electrochem Sci 7 (2012) 7313
33 TY Wu MH Tsao SG Su HP Wang YC Lin FL Chen CW Chang IW Sun J Braz
Chem Soc 22 (2011) 780
34 MH Tsao TY Wu HP Wang IW Sun SG Su YC Lin CW Chang Mater Lett 65
(2011) 583
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5084
35 SY Ku SY Lu Int J Electrochem Sci 6 (2011) 5219
36 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin IW Sun J Iran
Chem Soc 7 (2010) 707
37 IW Sun HP Wang H Teng SG Su YC Lin CW Kuo PR Chen TY Wu Int J
Electrochem Sci 7 (2012) 9748
38 TY Wu MH Tsao FL Chen SG Su CW Chang HP Wang YC Lin WC Ou-Yang
IW Sun Int J Mol Sci 11 (2010) 329
39 YX An PJ Zuo XQ Cheng LX Liao GP Yin Int J Electrochem Sci 6 (2011) 2398
40 LC Xuan YX An W Fang LX Liao YL Ma ZY Ren GP Yin Int J Electrochem Sci
6 (2011) 6590
41 HM Wang SQ Liu K Huang XG Yin YN Liu SJ Peng Int J Electrochem Sci 7
(2012) 1688
42 HM Wang SQ Liu NF Wang YN Liu Int J Electrochem Sci 7 (2012) 7579
43 H Ganjali MR Ganjali T Alizadeh F Faridbod P Norouzi Int J Electrochem Sci 6 (2011)
6085
44 MR Ganjali MH Eshraghi S Ghadimi SM Moosavi M Hosseini H Haji-Hashemi P
Norouzi Int J Electrochem Sci 6 (2011) 739
45 MR Ganjali T Poursaberi M Khoobi A Shafiee M Adibi M Pirali-Hamedani P Norouzi
Int J Electrochem Sci 6 (2011) 717
46 P Norouzi M Hosseini MR Ganjali M Rezapour M Adibi Int J Electrochem Sci 6 (2011)
2012
47 MR Ganjali MR Moghaddam M Hosseini P Norouzi Int J Electrochem Sci 6 (2011)
1981
48 MR Ganjali M Hosseini M Pirali-Hamedani HA Zamani Int J Electrochem Sci 6 (2011)
2808
49 MR Ganjali M Rezapour SK Torkestani H Rashedi P Norouzi Int J Electrochem Sci 6
(2011) 2323
50 P Norouzi M Pirali-Hamedani SO Ranaei-Siadat MR Ganjali Int J Electrochem Sci 6
(2011) 3704
51 F Faridbod HA Zamani M Hosseini M Pirali-Hamedani MR Ganjali P Norouzi Int J
Electrochem Sci 6 (2011) 3694
52 MR Ganjali SO Ranaei-Siadat H Rashedi M Rezapour P Norouzi Int J Electrochem Sci
6 (2011) 3684
53 TH Tsai KC Lin SM Chen Int J Electrochem Sci 6 (2011) 2672
54 MR Ganjali T Alizadeh F Azimi B Larjani F Faridbod P Norouzi Int J Electrochem
Sci 6 (2011) 5200
55 R Mirshafian MR Ganjali P Norouzi Int J Electrochem Sci 7 (2012) 1656
56 J Gao JG Liu WM Liu B Li YC Xin Y Yin ZG Zou Int J Electrochem Sci 6 (2011)
6115
57 TY Wu BK Chen L Hao KF Lin IW Sun J Taiwan Inst Chem Eng 42 (2011) 914
58 TY Wu BK Chen L Hao CW Kuo IW Sun J Taiwan Inst Chem Eng 43 (2012) 313
59 SW Peng AN Soriano RB Leron MH Li J Taiwan Inst Chem Eng 42 (2011) 233
60 TY Wu IW Sun MW Lin BK Chen CW Kuo HP Wang YY Chen SG Su J Taiwan
Inst Chem Eng 43 (2012) 58
61 TY Wu BK Chen CW Kuo L Hao YC Peng IW Sun J Taiwan Inst Chem Eng 43
(2012) 860
62 A Arce H Rodriguez A Soto Green Chem 9 (2007) 247
63 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Taiwan Inst Chem Eng 41 (2010)
315 64 X Li M Hou Z Zhang B Han G Yang X Wang L Zou Green Chem 10 (2008) 879
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)
Int J Electrochem Sci Vol 8 2013
5085
65 J Chen SK Spear JG Huddleston RD Rogers Green Chem 7 (2005) 64
66 U Domanska M Laskowska J Solution Chem 38 (2009) 779
67 K Tamura M Nakamura S Murakami J Solution Chem 26 (1997) 1199
68 Z Yu H Gao H Wang L Chen J Chem Eng Data 56 (2011) 2877
69 KN Marsh JA Boxall R Lichtenthaler Fluid Phase Equilib 219 (2004) 93
70 TY Wu SG Su ST Gung MW Lin YC Lin WC Ou-Yang IW Sun CA Lai J Iran
Chem Soc 8 (2011) 149
71 TY Wu L Hao CW Kuo YC Lin SG Su PL Kuo IW Sun Int J Electrochem Sci 7
(2012) 2047
72 TY Wu L Hao PR Chen JW Liao Int J Electrochem Sci 8 (2013) 2606
73 CW Kuo CW Huang BK Chen WB Li PR Chen TH Ho CG Tseng TY Wu Int J
Electrochem Sci 8 (2013) 3834
74 CW Kuo WB Li PR Chen JW Liao CG Tseng TY Wu Int J Electrochem Sci 8
(2013) 5007
75 TY Wu BK Chen L Hao YC Lin HP Wang CW Kuo IW Sun Int J Mol Sci 12
(2011) 8750
76 H Rodriguez JF Brennecke J Chem Eng Data 51 (2006) 2145
77 Y Tian X Wang J Wang J Chem Eng Data 53 (2008) 2056
78 TY Wu HC Wang SG Su ST Gung MW Lin CB Lin J Chin Chem Soc 57 (2010)
44
79 TY Wu BK Chen L Hao YC Peng IW Sun Int J Mol Sci 12 (2011) 2598
80 H Eyring MS John Significant Liquid Structure Wiley New York 1969
81 H Every AG Bishop M Forsyth DR MacFarlane Electrochim Acta 45 (2000) 1279 82 O Redlich AT Kister Ind Eng Chem 40 (1948) 345
83 A Paul P Kumar A Samanta J Phys Chem B 109 (2005) 9148
copy 2013 by ESG (wwwelectrochemsciorg)