Research Article Attapulgite Nanofiber-Cellulose ...downloads.hindawi.com/journals/ijps/2016/2081734.pdfResearch Article Attapulgite Nanofiber-Cellulose Nanocomposite with Core-Shell

Research ArticleAttapulgite Nanofiber-Cellulose Nanocompositewith Core-Shell Structure for Dye Adsorption

Xiaoyu Chen Xiaoxue Song and Yihe Sun

School of Material Engineering Jinling Institute of Technology Nanjing 211169 China

Correspondence should be addressed to Xiaoyu Chen chxyjiteducn

Received 25 March 2016 Revised 22 May 2016 Accepted 31 May 2016

Academic Editor Ming Zhang

Copyright copy 2016 Xiaoyu Chen et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Nanocomposite particle used for adsorption has attracted continuous attention because of large specific surface area and adjustableproperties from nanocomponent Herein nanocomposite particle with cellulose core and attapulgite nanofibers shell was preparedThe size of cellulose core was about 2mm and the thickness of nanofibers shell is about 300 120583m Adsorption capacity ofnanocomposite particle tomethylene blue can reach up to 1107mg Lminus1 and the best adsorption effect occurs at pH= 8 pseudo-first-order equation and the Langmuir equation best describe the adsorption kinetic and isotherm respectively repeated adsorption-desorption experimental results show that 9464 of the original adsorption capacity can be retained after being reused threetimes

1 Introduction

Attapulgite nanofiber is a kind of hydrated octahedral layeredmagnesium aluminum silicate with diameter of 20 nm andlength of several hundred nanometers to several microm-eters [1 2] Theoretical formula of attapulgite nanofiber is(Al2Mg2)Si8O20(OH)2(OH2)4sdot4H2O [3] Due to large spe-cific surface area attapulgite nanofiber has high sorptionability and is widely used in decoloring drying removingheavy metal ions or organic contaminants and other fields[4 5] Attapulgite nanofiber possesses permanent negativecharges and exchangeable cations [2] Used as dye adsor-bent attapulgite nanofiber can remove cationic dye suchas methylene blue from water But when added to waterattapulgite nanofibers suspend in water and are difficult tobe separated from water after adsorption The suspendedattapulgite will cause secondary pollution to the water andcannot be reused [6] Therefore finding an excellent carrierfor attapulgite is important to avoid secondary pollution andto reuse attapulgite

Polymer nanocomposites are composites of particle-filled polymers for which at least one dimension of thedispersed particles is in the nanometer range [7ndash9] Polymer

nanocomposites containing attapulgite nanofiber have beenprepared in which polymer exists as hydrogel and attapulgitenanofibers are embedded in the hydrogel [10 11] Thishydrogel can be used as super adsorbent and adsorbent forheavy metal ions [10 11]

Adsorption usually occurred on the surface of absorbent[12 13] Particle adsorbents have large surface area whichleads to high adsorption ability Core-shell structure withadsorbent on the shell has low cost and is favorable forparticle adsorbent to adsorb dye Cellulose is one of the mostabundant biopolymers in nature [14 15] Nanocompositeparticle with cellulose core and attapulgite nanofiber shell hasnever been reported But cellulose is difficult to dissolve incommon solvent to form cellulose bead NaOHurea solutionis a ldquogreenrdquo and cheap method to dissolve cellulose with nopollution [16]

In this study we combined attapulgite nanofiber andcellulose to prepare a low-cost adsorbent for water treat-ment We prepared cellulose bead by dissolving cellulose inNaOHurea solution as core to afford necessary strengthAttapulgite nanofibers were coated on cellulose bead as shellto adsorb dye Coated attapulgite shell can prevent secondpollution of attapulgite in water The structure adsorption

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2016 Article ID 2081734 9 pageshttpdxdoiorg10115520162081734

2 International Journal of Polymer Science

behaviors and reusability of this nanocomposite were inves-tigated

2 Materials and Methods

21 Materials NaOH HCl CaCl2 urea acetic acid methy-lene blue (methylthioninium chloride C16H18N3SCl) andother reagents used in the current work are all AR gradereagents Attapulgite is provided by Jiangsu dianjinshi Ausoil Mining Industry Co Ltd Distilled water is used inall experiments Scoured cotton was used in this study ascellulose provided by Xuzhou weicai hygienematerial factoryCo Ltd Sodium alginate is provided by Shanghai QingxiChemical Technology Co Ltd

22 Preparation of the Nanocomposite Particle Cellulose wasdissolved inNaOHurea solution using reportedmethod [17]Solution of NaOH (7 g) urea (12 g) and H2O (81mL) wascooled to minus12∘C then 2 g scoured cotton was immediatelyadded to above solution then scoured cotton was stirred vig-orously for 2min to obtain a transparent cellulose solutionThe resulting solution was dropped into 20wt acetic acidsolution to form cellulose bead then the cellulose bead wasimmersed in water for three days to remove urea and NaOHin bead

Attapulgite powder was dispersed in 25 wt sodiumalginate solutions with agitation and the mass ratios ofsodium alginateattapulgite are 1 0 1 1 083 1 and 05 1Then cellulose bead was coated with above suspension anddipped in CaCl2 solution to cross-link the sodium alginateThe coated bead was washed with deionized water anddried in an oven at 50∘C for 48 h to get dried compositeparticle Composite particles with alginateattapulgite massratios of 1 0 1 1 083 1 and 05 1 were labeled as AC0AC1 AC2 and AC3 respectively In addition attapulgite andcellulose solution mixture was dropped into 20wt aceticacid solution to form bead coded as AC4

23 Morphology and Structure of Composite Particle Surfacemorphology of composite bead was observed by scanningelectron microscopy (SEM SU8010 Hitachi) Microstruc-ture of composite particles was observed by digital micro-scope (503+GuangzhouHaote optical instrument company)Fourier-transform infrared (FTIR) spectra are recorded bySmart iTR accessory of FTIR spectrometer (Thermo FisherNicolet iS10) Wide-angle X-ray diffraction (XRD) mea-surement was carried out on an XRD diffractometer (D8-Advance Bruker) The patterns with the Cu K120572 radiation at40 kV and 30mAwere recorded in the region of 2120579 from 5∘ to70∘ TGA (STA 409 PC Luxx NETZSCH) was performed byheating samples to 700∘C at 5∘Cmin under a nitrogen flow

24 Adsorption Studies

241 The Adsorption Ability Study 01 g adsorbent was im-mersed into 80mL methylene blue solution of 12016mg Lminus1

at 25∘C for 36 h with 120 rmin controlled by a full temper-ature incubator shaker The adsorption capacity 119876 (mg gminus1)was calculated using the following equation

119876 = (1198620 minus 119862119890) 119881119898 (1)

where 1198620 (mg Lminus1) is the initial dye concentrations of thesolutions 119862119890 (mg Lminus1) is the equilibrium dye concentrationsof the solutions 119881 (L) is the volume of the solution and119898 (g) is the dried weight of the adsorbent [18] Methyleneblue concentration was measured at 664 nm using UV-Visspectrophotometer (VARIAN Cary 50)

242 pHVariation Theinitial pHofmethylene blue solution(12016mg Lminus1) was adjusted by 01mol Lminus1 HCl or NaOHaqueous solutions to change between 206 and 993 01 g AC2was immersed into 80mL of above solution for 36 h at 25∘CThe adsorption capacity was calculated based on (1)

243 Adsorption Kinetics The change of adsorptioncapacity with time was measured 05 g adsorbents (AC1)were immersed into 200mL methylene blue solution of12016mg Lminus1 at 25∘C with continuous shaking at 120 rminAt desired time intervals 05mL dyes solution was takenout to detect the current methylene blue concentration and05mL distilled water was added to the bulk solution to keepthe volume constant At time 119905119894 the adsorption capacity119876(119905119894)(mg gminus1) was calculated using the following equation [18]

119876 (119905119894) =(1198620 minus 119862119905119894)1198810 minus sum119894minus12 119862119905119894minus1119881119878

119898 (2)

where119862119905119894 (mg Lminus1) is the dye concentration at time 119905119894119881119878 is thevolume of solution taken out each time for dye concentrationanalysis and119898 (g) represents the mass of the adsorbent [18]

244 Adsorption Equilibrium Study 01 g of AC2 wasimmersed into 80mL methylene blue solution withconcentration of 6008mg Lminus1 9012mg Lminus1 10514mg Lminus112016mg Lminus1 and 1502mg Lminus1 Above five solutions wereshook at 120 rmin at 25∘C for 36 h Then the adsorptioncapacity (119876119890) of each solution was measured based on (1)The same procedure was conducted at 30∘C 35∘C 40∘C and50∘CThen the curves of 119876119890-119862119890 were plotted

25 Reusability Property The methylene blue-loaded AC1and AC2 were immersed into 01mol Lminus1 H2SO4 aqueoussolutions washed with distilled water and then reused inthe next cycle of adsorption experiment The adsorption-desorption experiments were conducted for four cycles Allexperiments were performed at 25∘C

3 Results and Discussion

31 Preparation of Composite Particles When used as adsor-bent attapulgite nanofiber usually suspends in solution

International Journal of Polymer Science 3

Attapulgite shellCellulose core

AttapulgiteSodium alginate

Ca2+Ca2+Ca2+

Figure 1 Schematic depiction of core-shell structure of cellulose-attapulgite composite particle

which leads to second pollution to water and difficulty ofregeneration In this study attapulgite is mixed with sodiumalginate solution and is coated on the surface of cellulosebead Sodium alginate derived primarily from brown sea-weed is a linear polysaccharide copolymer that consists oftwo sterically different repeating units 120573-d-mannuronic acid(M) and 120572-l-guluronic acid (G) in varying proportions[19] Sodium alginate can be cross-linked by Ca2+ to formhydrogel Above mixture is cross-linked by Ca2+ to forma hydrogel layer above the cellulose bead After dryingthe hydrogel becomes an attapulgite shell on the surface ofcellulose core preventing the second pollution of attapulgitepowder The structure of nanocomposite particle is shown inFigure 1

Cellulose is selected to prepare the core for its low cost andbeing nontoxic and biodegradable But cellulose is difficult todissolve in usual solvent In this study we use NaOHureasolution in low temperature as solvent to dissolve celluloseand to prepare cellulose bead as the core

32 Morphology and Structure of Composite Particles Fig-ure 2(a) shows microscope image of AC2 and particle hasa diameter of about 2mm and has a core-shell structureFigures 2(b)ndash2(f) show the SEM image of cross sectionand surface of composite particle Figure 2(b) shows thatthe shell is adhered closely to the cellulose core and noobvious boundary is found Figure 2(c) shows the coarseshell with thickness of 300 120583m (area between two whitearrows) Figure 2(d) shows the aggregation area of attapulgitenanofibers (white arrow pointed) Aggregation areas of atta-pulgite indicate that the dispersion of attapulgite in shell is notwell The aggregation areas are enlarged in Figure 2(e) fromwhich fibrous attapulgite is found Figure 2(f) shows the puresodium alginate area existing in the shell

FTIR spectra of sodium alginate attapulgite and AC2 areshown in Figure 3 In the spectrum of AC2 1421 cmminus1 belongsto the symmetric stretch vibration of C=Oof sodium alginate3614 cmminus1 is attributed to the stretching modes of hydroxylscoordinated with the magnesium 3582 cmminus1 and 3553 cmminus1belong to the symmetric and antisymmetric stretching modeof molecular water coordinated with the magnesium at theedges of the channels [20] 1027 cmminus1 belongs to Si-O-Sistretching vibration of attapulgite [21] The results indicatethat the shell is composed by sodium alginate and attapulgiteSmart iTR measures the surface structure of sample So onlythe shell structure of composite particle can be detected

Figure 4 shows the XRD peaks of attapulgite and atta-pulgite shell Strong diffraction peak of 848∘ is a typicalpeak of attapulgite corresponding to basal spacing of about1055 A and is attributed to the primary diffraction of the (110)crystal face Other diffraction peaks are attributed as d(110)(1055 A) d(200) (643 A) d(130) (543 A) d(040) (448 A)d(121) (414 A) and d(061) (255 A) [22] All belong to thecharacter peaks of attapulgiteThe diffraction peaks of 2654∘are attributed to intergrowthminerals of quartz in attapulgiteIn attapulgite shell no obvious shift of peak position indicatesthat the crystal structure of attapulgite has no change duringmixing Absence of diffraction peaks of sodium alginaterevealed that sodium alginate exists as amorphous XRDresults confirmed that attapulgite is the main component ofshell

TG and DTG curves for the cellulose attapulgite andAC1 are presented in Figure 5 The weight loss rate ofAC1 is between attapulgite and cellulose For AC1 below100∘C the weight loss was ascribed to the removal ofwater which included surface water and zeolitic water ofattapulgite Between 200 and 300∘C the rapid weight losscan be attributed to the decomposition of cellulose andsodium alginate Above 300∘C the weight loss correspondsto the degradation of residual decomposition products andloss of coordinated water and structural hydroxyl water inattapulgite [23] The high residue mass of AC1 compared tothe cellulose indicates the existence of attapulgite

33 Adsorption Capacity Figure 6 shows the adsorptioneffect of AC1 (Figure 6(a) before adsorption Figure 6(b)after adsorption) The slight color of Figure 6(b) reveals thatthe nanocomposite particles could effectively remove themethylene blue from water The clear solution indicates thatattapulgite nanocomposite prevents the second pollution ofattapulgite nanofiber in water

Figure 7 compares the adsorption capacities of nanocom-posite particles (AC1 AC2 and AC3) with core-shell struc-ture to contrast samples (cellulose bead AC0 and AC4)Composite particles have better adsorption capacities com-pared to the adsorption capacities of cellulose bead AC0 andAC4 which indicate that the shell of attapulgite nanofiber caneffectively absorb methylene blue The adsorption capacitiesof AC1 AC2 and AC3 are higher than AC0 which only hasa shell of sodium alginate indicating the adsorption mainlyresulted from attapulgite nanofiber AC3 has maximumadsorption capacity of 91mgsdotgminus1

Attapulgite fiber is a kind of silicate with nanosized rod-like morphology and consists of two double chains of thepyroxene type (SiO3)

2minus like amphibole (Si4O11)6minus running

parallel to the fiber axis [24 25] Attapulgite fiber hashigh surface area and moderate cation exchange capacitywhich is useful for attapulgite as adsorbents to remove dyein wastewater In addition attapulgite fiber has negativelycharged sorption sites because of isomorphic substitutionsin structure So attapulgite nanofiber can absorb cationicdyes through electrostatic attraction The higher adsorptioncapacity of AC3 resulted from the high content of attapulgitenanofiber From Figure 8 we can see that AC1 has rare


(a) (b) (c)

(d) (e) (f)

Figure 2Themorphology of the cellulose-attapulgite composite particles (AC2) ((a) cross section of particle by digital microscope (b) crosssection of particle by SEM (c) shell structure of particle (d) aggregation area of attapulgite (e) amplified aggregation area of attapulgite (f)area of sodium alginate)

AC2

Attapulgite

Sodium alginate

1419

1034

14211027

35513585

3616

36143582

3553

3500 3000 2500 2000 1500 1000 5004000Wavenumber (cmminus1)

Figure 3 FTIR spectra of sodium alginate attapulgite and AC2

dispersion of attapulgite nanofibers on the shell compared toAC2 andAC3 which leads to low adsorption capacity of AC1

Other adsorption capacities formethylene blue have beenreported such as cross-linked porous starch (946mg gminus1)[26] sugar extracted spent rice biomass (813mg gminus1) [27]and attapulgite (51mg gminus1) [28] Compared to attapulgite therelative lower capacity of nanocomposite particle may haveresulted in the aggregation of attapulgite on the shell whichwas observed by SEM photo (Figure 2(d)) The aggregationdecreased the specific surface area of attapulgite and thendecreased adsorption ability [29]

(061

)

Qua

rts

(121

)(0

40)

(110

)(1

10)

(200

)(2

00)

(130

)(1

30)

Attapulgite

Attapulgite-alginate

(040

)(1

21)

Qua

rts

(061

)

20 30 40 50 60 70102120579 (deg)

Figure 4 The powder X-ray diffraction pattern of the attapulgiteand attapulgite shell

34 Effects of pH on the Adsorption Figure 9 shows theadsorption capacity of AC2 in the pH range of 206sim993As the pH increased from 206 to 797 adsorption capacityincreased from 770 to 888mg gminus1 as the pH increased from797 to 993 adsorption capacity decreased from 888 to843mg gminus1

For attapulgite some isomorphic substitutions in thetetrahedral layer such as Al3+ for Si4+ develop negativelycharged sorption sites (Si-Ominus) on the surface of attapulgite[30] Si-Ominus can absorb cation dye through electrostaticattraction [30] But at low pH these negatively charged


CellulosePure attapulgiteAC1


minus08

minus07

minus06

minus05

minus04

minus03

minus02

minus01

00

dW

dT

10

20

30

40

50

60

70

80

90

100W

eigh

t (

)

200 300 400 500 600 700100T (∘C)

100 150 200 250 300 350 400 450 500 550 600 650 70050T (∘C)

Figure 5 The TG and DTG of cellulose attapulgite and AC1

(a) (b)

Figure 6 The methylene blue adsorption effect of 05 g AC1 in200mL 12016mg Lminus1 methylene blue solution for 48 h ((a) beforeadsorption and (b) after adsorption)

sorption sites are protonated to form Si-OH2+ by H+ which

decrease the negative sites to attract methylene blue AspH increases protonated groups become less and negativelycharged sites such as Si-Ominus increase and favor the adsorptionof cationic dye In the alkaline pH range the decreasing ofadsorption capacity could be attributed to competition ofNa+ions for the negative adsorption sites [31]

35 Adsorption Kinetics Time dependence of the adsorptioncapacity of AC1 for methylene blue was tested to study theadsorption kinetics The initial concentration of methyleneblue is 12016mg Lminus1 The experimental results are shownin Figure 10 About 50 of methylene blue was adsorbedwithin 7 h The adsorption equilibrium was achieved after36 h These results were similar to cross-linked porous starch

Cellulose AC0 AC1 AC2 AC3 AC40

2

4

6

8

Qe

(mg g

minus1 )

Figure 7 Adsorption capacity of six samples (cellulose bead AC0AC1 AC2 AC3 and AC4)

whose adsorption equilibrium was reached in about 30 h formethylene blue [26]

To further investigate the adsorption mechanisms fourcommon kinetic models were used to fit the data namelypseudo-first-order model [32] pseudo-second-order model[33] intraparticle diffusion models [34] and the Elovichequation [35] Table 1 shows the equations of these modelsIn these models 1198961 is the rate constant first-order absorption(minminus1) [32] 119876eq (mg gminus1) is the amount of dye adsorbedat equilibrium 119876119905 (mg gminus1) is the amount of dye adsorbedat any time 119905 (min) 1198962 (gmgminus1minminus1) is the second-orderrate constant [33] 119870119879 (mg gminus1sdotmin12) is the diffusion rateconstant [34] 119862 is a constant related to the thickness ofboundary layer [34] 119886 (mg gminus1minminus1) is the initial sorptionrate [35] 119887 (gmgminus1) is the desorption constant related tothe extent of surface coverage and activation energy forchemisorption [35]


(a) (b) (c)

Figure 8 The surface morphology of the nanocomposite particles ((a) AC1 (b) AC2 (c) AC3)

Table 1 Kinetic models and their equations

Kinetic model Equation Plot ReferencePseudo-first-order log(119876eq minus 119876119905) = log119876eq minus 1198961119905 log(119876eq minus 119876119905) versus 119905 [32]Pseudo-second-order 119905

119876119905 =111989621198762eq+ 1119876eq 119905 119905119876119905 versus 119905 [33]

Intraparticle diffusion 119876119905 = 11987011987911990512 + 119862 119876119905 versus 119905 [34]

Elovich equation 119876119905 = (1119887) ln (119886119887) +1119887 ln 119905 119876119905 versus ln 119905 [35]

76

78

80

82

84

86

88

90

Qe

(mg g

minus1 )

4 6 8 102pH

Figure 9The influence of pH on the adsorption capacity of AC2 formethylene blue with concentration of 12016mg Lminus1 at 25∘C

The pseudo-second-order model assumes that the ratelimiting step is chemical sorption [36] Elovich modelrecently has been found to be valid to describe the sorptionkinetics of ion exchange systems [18]The fitted parameters ofthese kineticmodels are listed in Table 21198772 of the linear formfor the various models suggests that the pseudo-first-ordermodel is more suitable to describe the adsorption kineticbehavior Using intraparticle diffusion model plots of 119876119905versus 11990512 do not pass through the origin indicating that theadsorption process is also controlled by film diffusion [36]

36 Adsorption Equilibrium Study The equilibrium adsorp-tion data is shown in Figure 11 At each temperature adsorp-tion capacity of AC2 for five different concentrations of

5 10 15 20 25 30 35 40 45 50 550t (h)

0

2

4

6

8

10

Con

cent

ratio

n (m

g Lminus

1 )

00

05

10

15

20

25

30

35

40

45

50

Qt

(mg g

minus1 )

Figure 10 The absorbed capacity of AC1 for methylene blue withconcentration of 12016mg Lminus1at 25∘C and pH = 70 as a functionof time (◼ represents experiment data the full line represents fitof experimental data with a pseudo-first-order kinetic equation 998771represents concentration of methylene blue in solution)

methylene blue was measured The equilibrium adsorptiondata was correlated to four isotherm models Langmuir [37]Freundlich [38] Sips [39] and Dubinin-Radushkevich [40]Table 3 shows the equations of these models In these models119876max is the maximum adsorption at monolayer coverage(mg gminus1) [37] 119887 is equilibrium constant (mLmgminus1) in Lang-muir adsorption [37] or Sips constant related to energy ofadsorption in Sips model [39] 119870119865 is the Freundlich charac-teristic constants [38] 1119899 is the Freundlich characteristicconstants [38] 119899 could be regarded as the Sips parametercharacterizing the system heterogeneity 119861 is a constant


Table 2 The kinetic parameters for MB adsorption onto AC1

119879 (∘C)

Pseudo-first-order

equation

Pseudo-second-orderequation Intraparticle diffusion models Elovich equation

1198961(minminus1) 1198772 1198962(gmgminus1minminus1) 1198772 119870119879(mg gminus1minminus12) 1198772 119886

(mggminus1minminus1)119887(gmgminus1) 1198772

25 011309 09952 001674 09779 07593 08746 13717 07705 09687

Table 3 Isotherm models and their equations

Isotherm model Equation Plot ReferenceLangmuir 1

119876eq =1119876max+ 1119876max119887

1119862119890 1119876eq versus 1119862119890 [37]

Freundlich ln119876eq = 1119899 ln119862119890 + ln119870119865 ln119876eq versus ln119862119890 [38]

Sips 119876eq = 1198761198981198871198621119899

119890

1 + 1198871198621119899119890119876eq versus 119862119890 [39]

Dubinin-Radushkevich ln119876eq = ln119876119898 minus 1198611205762 ln119876eq versus 120576 [40]

25∘C

30∘C

35∘C

40∘C

50∘C

02 04 06 08 10 12 14 16 18 20 22 24 26 2800Ce (mg Lminus1)

4

5

6

7

8

9

10

11

12

Qe

(mg g

minus1 )

Figure 11 The curve of 119862119890-119876119890 of AC2 under different temperatureswith duration time of 36 h

related to the mean free energy of adsorption per mol ofthe adsorbate (mol2 Jminus2) [40]119876119898 is the theoretical saturationcapacity (mg gminus1) [40] 120576 is the Polanyi potential [40] whichis equal to119877119879ln(1+1119862119890)119877 (Jmolminus1 Kminus1) is the gas constant119879 (K) is the absolute temperature

The Langmuir isothermmodel assumes the adsorption ismonolayer adsorption [18] A finite number of identical sitesexist on a surface and all sites are energetically equivalentand there is no interaction between adsorbed moleculesFreundlich model is applied to describe that adsorptionoccurs on a heterogeneous surface The fitting parameters ofthe above models are listed in Table 4 Most of the determi-nation coefficients (1198772) of the Langmuir model exceed 093compared with those of the other models This indicates thatthe Langmuir model is suitable to describe the adsorption

behavior of AC2 So it can be concluded that methylene bluemolecule is absorbed on the surface with monolayer FromFigure 11 we can see that119862119890 is almost near zero at 25∘C 40∘Cand 50∘C which indicates that the particle can remove dye invery dilute aqueous solutions

37 Regeneration Efficiency Reusability is very importantfor adsorbent in practical applications In current work theadsorption and desorption processes were repeated for threecycles to measure the regeneration efficiency 01mol Lminus1H2SO4 aqueous solution was used to recover the methyleneblue loaded composite particles Table 5 shows the adsorptioncapacities and the regeneration efficiency in each cycleAfter three cycles AC2 gets 9464 recovery indicating ahigh regeneration efficiency This also illuminates that theadsorbent is suitable for practical applications

4 Conclusions

The attapulgite nanofibers were coated onto the surface ofcellulose bead to form nanocomposite particles with core-shell structure SEM FTIR XRD and TG all revealed thatattapulgite nanofiber exists in the shell of nanocompositeparticles Nanocomposite particles have higher adsorptioncapacity than cellulose bead Adsorption capacity is changedwith pH of dye solution and largest adsorption capacityoccurs at pH = 8 The adsorption equilibrium and kineticsstudy of composite particles indicate that the adsorptionbehavior follows Langmuir model and pseudo-first-orderequation Dye-loaded nanocomposite could be regeneratedeasily and high adsorption ability is reserved Simple prepa-ration low cost being easy to regenerate make the core-shellstructured nanocomposite a suitable carrier for attapulgiteand an attractive adsorbent for removal of the organic dyesfrom water This study also proposes a new approach to usethe attapulgite and cellulose as adsorption material


Table 4 The isotherms parameters for methylene blue adsorption onto AC2

119879 (∘C)Langmuir model Freundlich model Dubinin-Radushkevich

model Sips model

119876max(mggminus1)119887(Lmgminus1) 1198772 1119899 119870119865(mg gminus1) 1198772 119876max(mggminus1)

119864(kJmol) 119877

2 119876max(mg gminus1) 119887 1119899 1198772

25 112284 46800 09365 02410 88710 09282 87615 63976 08012 1231803 00795 02963 0915330 141965 07031 09875 05227 57221 09991 91354 20422 09360 516949 01252 05965 0999235 131130 15313 09801 04446 76222 09677 96025 29773 09125 1670934 08786 07696 0967740 116023 87149 09721 01413 94353 09199 88507 121932 07702 1510619 00699 01783 0900650 113469 368745 09940 00741 107578 08544 102382 164501 07087 3209413 00351 00818 08492

Table 5 Adsorption-desorption cycles of methylene blue

Sample Adsorption ability First adsorption Second adsorption Third adsorption Fourth adsorption

AC1 Adsorption capacity (mg gminus1) 86317 85228 79651 76254Recovery () mdash 9874 9228 8834


Competing Interests

The authors declare that they have no competing interests

Acknowledgments

The authors would like to thank the Natural Science Founda-tion for Colleges and Universities of Jiangsu Province (Grantno 12KJD150006) for the financial support of this research

References

[1] Y Liu P Liu Z Su F Li and F Wen ldquoAttapulgite-Fe3O4magnetic nanoparticles via co-precipitation techniquerdquoAppliedSurface Science vol 255 no 5 pp 2020ndash2025 2008

[2] W BWang andAQWang ldquoNanocomposite of carboxymethylcellulose and attapulgite as a novel pH-sensitive superab-sorbent synthesis characterization and propertiesrdquo Carbohy-drate Polymers vol 82 no 1 pp 83ndash91 2010

[3] B Mu Q Wang and A Q Wang ldquoPreparation of magneticattapulgite nanocomposite for the adsorption of Ag+ andapplication for catalytic reduction of 4-nitrophenolrdquo Journal ofMaterials Chemistry A vol 1 no 24 pp 7083ndash7090 2013

[4] Y Liu W B Wang Y L Jin and A Q Wang ldquoAdsorptionbehavior of methylene blue from aqueous solution by thehydrogel composites based on attapulgiterdquo Separation Scienceand Technology vol 46 no 5 pp 858ndash868 2011

[5] L Wang J P Zhang and A Q Wang ldquoFast removal of methy-lene blue from aqueous solution by adsorption onto chitosan-g-poly (acrylic acid)attapulgite compositerdquo Desalination vol266 no 1ndash3 pp 33ndash39 2011

[6] Q-H Fan P Li Y-F Chen and W-S Wu ldquoPreparationand application of attapulgiteiron oxide magnetic compositesfor the removal of U(VI) from aqueous solutionrdquo Journal ofHazardous Materials vol 192 no 3 pp 1851ndash1859 2011

[7] M Alexandre and P Dubois ldquoPolymer-layered silicatenanocomposites preparation properties and uses of a newclass of materialsrdquoMaterials Science and Engineering R Reportsvol 28 no 1 pp 1ndash63 2000

[8] K Kabiri H Omidian M J Zohuriaan-Mehr and S Doroudi-ani ldquoSuperabsorbent hydrogel composites and nanocompos-ites a reviewrdquo Polymer Composites vol 32 no 2 pp 277ndash2892011

[9] M Shibayama ldquoStructure-mechanical property relationship oftough hydrogelsrdquo SoftMatter vol 8 no 31 pp 8030ndash8038 2012

[10] H X Yang W B Wang and A Q Wang ldquoA pH-sensitivebiopolymer-based superabsorbent nanocomposite fromsodium alginate and attapulgite synthesis characterizationand swelling behaviorsrdquo Journal of Dispersion Science andTechnology vol 33 no 8 pp 1154ndash1162 2012

[11] P Liu L P Jiang L X Zhu and A Q Wang ldquoAttapulgitepoly(acrylic acid) nanocomposite (ATPPAA) hydrogels withmultifunctionalized attapulgite (org-ATP) nanorods as uniquecross-linker preparation optimization and selective adsorptionof Pb(II) Ionrdquo ACS Sustainable Chemistry and Engineering vol2 no 4 pp 643ndash651 2014

[12] M Zhang J Soto-Rodrıguez I-C Chen and M AkbulutldquoAdsorption and removal dynamics of polymeric micellarnanocarriers loaded with a therapeutic agent on silica surfacesrdquoSoft Matter vol 9 no 42 pp 10155ndash10164 2013

[13] I-C Chen M Zhang B Teipel I S De Araujo Y Yeginand M Akbulut ldquoTransport of polymeric nanoparticulatedrug delivery systems in the proximity of silica and sandrdquoEnvironmental Science and Technology vol 49 no 6 pp 3575ndash3583 2015

[14] S Liu D Tao T Yu H Shu R Liu and X Liu ldquoHighly flexibletransparent cellulose composite films used in UV imprintlithographyrdquo Cellulose vol 20 no 2 pp 907ndash918 2013

[15] M Zhang and M Akbulut ldquoAdsorption desorption andremoval of polymeric nanomedicine on and from cellulosesurfaces effect of sizerdquo Langmuir vol 27 no 20 pp 12550ndash12559 2011

[16] J Zhou C Chang R Zhang and L Zhang ldquoHydrogelsprepared from unsubstituted cellulose in NaOHurea aqueoussolutionrdquoMacromolecular Bioscience vol 7 no 6 pp 804ndash8092007

[17] J Cai L Zhang J Zhou et al ldquoMultifilament fibers basedon dissolution of cellulose in NaOHurea aqueous solution


structure and propertiesrdquo Advanced Materials vol 19 no 6 pp821ndash825 2007

[18] W X Zhang H Yang L Dong et al ldquoEfficient removal of bothcationic and anionic dyes from aqueous solutions using a novelamphoteric straw-based adsorbentrdquo Carbohydrate Polymersvol 90 no 2 pp 887ndash893 2012

[19] J Han Z Zhou R Yin D Yang and J Nie ldquoAlginate-chitosanhydroxyapatite polyelectrolyte complex porous scaf-folds preparation and characterizationrdquo International Journalof Biological Macromolecules vol 46 no 2 pp 199ndash205 2010

[20] J-HHuang Y-F Liu Q-Z Jin andX-GWang ldquoSpectra studyon the influence of drying process on palygorskite structurerdquoSpectroscopy and Spectral Analysis vol 27 no 2 pp 408ndash4102007

[21] Z Lei Q Yang S Wu and X Song ldquoReinforcement ofpolyurethaneepoxy interpenetrating network nanocompositeswith an organically modified palygorskiterdquo Journal of AppliedPolymer Science vol 111 no 6 pp 3150ndash3162 2009

[22] C Wang Q Wu F Liu et al ldquoSynthesis and characterization ofsoy polyol-based polyurethane nanocomposites reinforcedwithsilylated palygorskiterdquo Applied Clay Science vol 101 pp 246ndash252 2014

[23] W Li A Adams J D Wang B Blumich and Y G YangldquoPolyethylenepalygorskite nanocomposites preparation by insitu polymerization and their characterizationrdquo Polymer vol 51no 21 pp 4686ndash4697 2010

[24] Y Zhang W Wang J Zhang P Liu and A Wang ldquoA compar-ative study about adsorption of natural palygorskite for methy-lene bluerdquo Chemical Engineering Journal vol 262 pp 390ndash3982015

[25] Y Liu W Wang and A Wang ldquoAdsorption of lead ionsfrom aqueous solution by using carboxymethyl cellulose-g-poly(acrylic acid)attapulgite hydrogel compositesrdquo Desalinationvol 259 no 1ndash3 pp 258ndash264 2010

[26] L Guo G Y Li J S Liu Y F Meng and Y F Tang ldquoAdsorptivedecolorization of methylene blue by crosslinked porous starchrdquoCarbohydrate Polymers vol 93 no 2 pp 374ndash379 2013

[27] M S U Rehman I Kim and J-I Han ldquoAdsorption ofmethylene blue dye from aqueous solution by sugar extractedspent rice biomassrdquo Carbohydrate Polymers vol 90 no 3 pp1314ndash1322 2012

[28] A Al-Futaisi A Jamrah A Al-Rawas and S Al-HanaildquoAdsorption capacity and mineralogical and physico-chemicalcharacteristics of Shuwaymiyah palygorskite (Oman)rdquo Environ-mental Geology vol 51 no 8 pp 1317ndash1327 2007

[29] G Y Tian Y R Kang B Mu and A Q Wang ldquoAttapulgitemodified with silane coupling agent for phosphorus adsorptionand deep bleaching of refined palm oilrdquo Adsorption Science ampTechnology vol 32 no 1 pp 37ndash48 2014

[30] H Chen and J Zhao ldquoAdsorption study for removal of Congored anionic dye using organo-attapulgiterdquo Adsorption vol 15no 4 pp 381ndash389 2009

[31] M T Yagub T K Sen and M Ang ldquoRemoval of cationic dyemethylene blue (MB) from aqueous solution by ground raw andbasemodified pine cone powderrdquoEnvironmental Earth Sciencesvol 71 no 4 pp 1507ndash1519 2014

[32] S Lagergren ldquoAbout the theory of so-called adsorption ofsoluble substancesrdquo Kungliga Svenska VetenskapsakademiensHandlingar vol 24 pp 1ndash39 1898

[33] Y S Ho and G McKay ldquoSorption of dye from aqueous solutionby peatrdquo Chemical Engineering Journal vol 70 no 2 pp 115ndash124 1998

[34] Y A YahayaMMatDon and S Bhatia ldquoBiosorption of copper(II) onto immobilized cells of Pycnoporus sanguineus fromaqueous solution equilibrium and kinetic studiesrdquo Journal ofHazardous Materials vol 161 no 1 pp 189ndash195 2009

[35] M J D Low ldquoKinetics of chemisorption of gases on solidsrdquoChemical Reviews vol 60 no 3 pp 267ndash312 1960

[36] C Duran D Ozdes A Gundogdu andH B Senturk ldquoKineticsand isotherm analysis of basic dyes adsorption onto almondshell (Prunus dulcis) as a low cost adsorbentrdquo Journal ofChemical amp Engineering Data vol 56 no 5 pp 2136ndash2147 2011

[37] I Langmuir ldquoThe adsorption of gases on plane surfaces ofglassmica and platinumrdquoThe Journal of the AmericanChemicalSociety vol 40 no 9 pp 1361ndash1403 1918

[38] H M F Freundlich ldquoUber die adsorption in losungenrdquoZeitschrift fur Physikalische Chemie vol 57 pp 385ndash470 1906

[39] R Sips ldquoOn the structure of a catalyst surfacerdquo The Journal ofChemical Physics vol 16 no 5 pp 490ndash495 1948

[40] M M Dubinin ldquoSorption and structure of active carbons IAdsorption of organic vaporsrdquo Zhurnal Fizicheskoi Khimii vol21 pp 1351ndash1362 1947

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


behaviors and reusability of this nanocomposite were inves-tigated

2 Materials and Methods

21 Materials NaOH HCl CaCl2 urea acetic acid methy-lene blue (methylthioninium chloride C16H18N3SCl) andother reagents used in the current work are all AR gradereagents Attapulgite is provided by Jiangsu dianjinshi Ausoil Mining Industry Co Ltd Distilled water is used inall experiments Scoured cotton was used in this study ascellulose provided by Xuzhou weicai hygienematerial factoryCo Ltd Sodium alginate is provided by Shanghai QingxiChemical Technology Co Ltd

22 Preparation of the Nanocomposite Particle Cellulose wasdissolved inNaOHurea solution using reportedmethod [17]Solution of NaOH (7 g) urea (12 g) and H2O (81mL) wascooled to minus12∘C then 2 g scoured cotton was immediatelyadded to above solution then scoured cotton was stirred vig-orously for 2min to obtain a transparent cellulose solutionThe resulting solution was dropped into 20wt acetic acidsolution to form cellulose bead then the cellulose bead wasimmersed in water for three days to remove urea and NaOHin bead

Attapulgite powder was dispersed in 25 wt sodiumalginate solutions with agitation and the mass ratios ofsodium alginateattapulgite are 1 0 1 1 083 1 and 05 1Then cellulose bead was coated with above suspension anddipped in CaCl2 solution to cross-link the sodium alginateThe coated bead was washed with deionized water anddried in an oven at 50∘C for 48 h to get dried compositeparticle Composite particles with alginateattapulgite massratios of 1 0 1 1 083 1 and 05 1 were labeled as AC0AC1 AC2 and AC3 respectively In addition attapulgite andcellulose solution mixture was dropped into 20wt aceticacid solution to form bead coded as AC4

23 Morphology and Structure of Composite Particle Surfacemorphology of composite bead was observed by scanningelectron microscopy (SEM SU8010 Hitachi) Microstruc-ture of composite particles was observed by digital micro-scope (503+GuangzhouHaote optical instrument company)Fourier-transform infrared (FTIR) spectra are recorded bySmart iTR accessory of FTIR spectrometer (Thermo FisherNicolet iS10) Wide-angle X-ray diffraction (XRD) mea-surement was carried out on an XRD diffractometer (D8-Advance Bruker) The patterns with the Cu K120572 radiation at40 kV and 30mAwere recorded in the region of 2120579 from 5∘ to70∘ TGA (STA 409 PC Luxx NETZSCH) was performed byheating samples to 700∘C at 5∘Cmin under a nitrogen flow

24 Adsorption Studies

241 The Adsorption Ability Study 01 g adsorbent was im-mersed into 80mL methylene blue solution of 12016mg Lminus1

at 25∘C for 36 h with 120 rmin controlled by a full temper-ature incubator shaker The adsorption capacity 119876 (mg gminus1)was calculated using the following equation

119876 = (1198620 minus 119862119890) 119881119898 (1)

where 1198620 (mg Lminus1) is the initial dye concentrations of thesolutions 119862119890 (mg Lminus1) is the equilibrium dye concentrationsof the solutions 119881 (L) is the volume of the solution and119898 (g) is the dried weight of the adsorbent [18] Methyleneblue concentration was measured at 664 nm using UV-Visspectrophotometer (VARIAN Cary 50)

242 pHVariation Theinitial pHofmethylene blue solution(12016mg Lminus1) was adjusted by 01mol Lminus1 HCl or NaOHaqueous solutions to change between 206 and 993 01 g AC2was immersed into 80mL of above solution for 36 h at 25∘CThe adsorption capacity was calculated based on (1)

243 Adsorption Kinetics The change of adsorptioncapacity with time was measured 05 g adsorbents (AC1)were immersed into 200mL methylene blue solution of12016mg Lminus1 at 25∘C with continuous shaking at 120 rminAt desired time intervals 05mL dyes solution was takenout to detect the current methylene blue concentration and05mL distilled water was added to the bulk solution to keepthe volume constant At time 119905119894 the adsorption capacity119876(119905119894)(mg gminus1) was calculated using the following equation [18]

119876 (119905119894) =(1198620 minus 119862119905119894)1198810 minus sum119894minus12 119862119905119894minus1119881119878

119898 (2)

where119862119905119894 (mg Lminus1) is the dye concentration at time 119905119894119881119878 is thevolume of solution taken out each time for dye concentrationanalysis and119898 (g) represents the mass of the adsorbent [18]

244 Adsorption Equilibrium Study 01 g of AC2 wasimmersed into 80mL methylene blue solution withconcentration of 6008mg Lminus1 9012mg Lminus1 10514mg Lminus112016mg Lminus1 and 1502mg Lminus1 Above five solutions wereshook at 120 rmin at 25∘C for 36 h Then the adsorptioncapacity (119876119890) of each solution was measured based on (1)The same procedure was conducted at 30∘C 35∘C 40∘C and50∘CThen the curves of 119876119890-119862119890 were plotted

25 Reusability Property The methylene blue-loaded AC1and AC2 were immersed into 01mol Lminus1 H2SO4 aqueoussolutions washed with distilled water and then reused inthe next cycle of adsorption experiment The adsorption-desorption experiments were conducted for four cycles Allexperiments were performed at 25∘C

3 Results and Discussion

31 Preparation of Composite Particles When used as adsor-bent attapulgite nanofiber usually suspends in solution




Ca2+Ca2+Ca2+














(a) (b) (c)

(d) (e) (f)


AC2

Attapulgite

Sodium alginate

1419

1034

14211027

35513585

3616

36143582

3553





(061

)

Qua

rts

(121

)(0

40)

(110

)(1

10)

(200

)(2

00)

(130

)(1

30)

Attapulgite


(040

)(1

21)

Qua

rts

(061

)

20 30 40 50 60 70102120579 (deg)







minus08

minus07

minus06

minus05

minus04

minus03

minus02

minus01

00

dW

dT

10

20

30

40

50

60

70

80

90

100W

eigh

t (

)

200 300 400 500 600 700100T (∘C)

100 150 200 250 300 350 400 450 500 550 600 650 70050T (∘C)


(a) (b)






2

4

6

8

Qe

(mg g

minus1 )





(a) (b) (c)




119876119905 =111989621198762eq+ 1119876eq 119905 119905119876119905 versus 119905 [33]



76

78

80

82

84

86

88

90

Qe

(mg g

minus1 )

4 6 8 102pH




5 10 15 20 25 30 35 40 45 50 550t (h)

0

2

4

6

8

10

Con

cent

ratio

n (m

g Lminus

1 )

00

05

10

15

20

25

30

35

40

45

50

Qt

(mg g

minus1 )





119879 (∘C)

Pseudo-first-order

equation




25 011309 09952 001674 09779 07593 08746 13717 07705 09687



119876eq =1119876max+ 1119876max119887

1119862119890 1119876eq versus 1119862119890 [37]


Sips 119876eq = 1198761198981198871198621119899

119890

1 + 1198871198621119899119890119876eq versus 119862119890 [39]


25∘C

30∘C

35∘C

40∘C

50∘C

02 04 06 08 10 12 14 16 18 20 22 24 26 2800Ce (mg Lminus1)

4

5

6

7

8

9

10

11

12

Qe

(mg g

minus1 )






4 Conclusions





model Sips model


119864(kJmol) 119877

2 119876max(mg gminus1) 119887 1119899 1198772

25 112284 46800 09365 02410 88710 09282 87615 63976 08012 1231803 00795 02963 0915330 141965 07031 09875 05227 57221 09991 91354 20422 09360 516949 01252 05965 0999235 131130 15313 09801 04446 76222 09677 96025 29773 09125 1670934 08786 07696 0967740 116023 87149 09721 01413 94353 09199 88507 121932 07702 1510619 00699 01783 0900650 113469 368745 09940 00741 107578 08544 102382 164501 07087 3209413 00351 00818 08492





Competing Interests


Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Ca2+Ca2+Ca2+














(a) (b) (c)

(d) (e) (f)


AC2

Attapulgite

Sodium alginate

1419

1034

14211027

35513585

3616

36143582

3553





(061

)

Qua

rts

(121

)(0

40)

(110

)(1

10)

(200

)(2

00)

(130

)(1

30)

Attapulgite


(040

)(1

21)

Qua

rts

(061

)

20 30 40 50 60 70102120579 (deg)







minus08

minus07

minus06

minus05

minus04

minus03

minus02

minus01

00

dW

dT

10

20

30

40

50

60

70

80

90

100W

eigh

t (

)

200 300 400 500 600 700100T (∘C)

100 150 200 250 300 350 400 450 500 550 600 650 70050T (∘C)


(a) (b)






2

4

6

8

Qe

(mg g

minus1 )





(a) (b) (c)




119876119905 =111989621198762eq+ 1119876eq 119905 119905119876119905 versus 119905 [33]



76

78

80

82

84

86

88

90

Qe

(mg g

minus1 )

4 6 8 102pH




5 10 15 20 25 30 35 40 45 50 550t (h)

0

2

4

6

8

10

Con

cent

ratio

n (m

g Lminus

1 )

00

05

10

15

20

25

30

35

40

45

50

Qt

(mg g

minus1 )





119879 (∘C)

Pseudo-first-order

equation




25 011309 09952 001674 09779 07593 08746 13717 07705 09687



119876eq =1119876max+ 1119876max119887

1119862119890 1119876eq versus 1119862119890 [37]


Sips 119876eq = 1198761198981198871198621119899

119890

1 + 1198871198621119899119890119876eq versus 119862119890 [39]


25∘C

30∘C

35∘C

40∘C

50∘C

02 04 06 08 10 12 14 16 18 20 22 24 26 2800Ce (mg Lminus1)

4

5

6

7

8

9

10

11

12

Qe

(mg g

minus1 )






4 Conclusions





model Sips model


119864(kJmol) 119877

2 119876max(mg gminus1) 119887 1119899 1198772

25 112284 46800 09365 02410 88710 09282 87615 63976 08012 1231803 00795 02963 0915330 141965 07031 09875 05227 57221 09991 91354 20422 09360 516949 01252 05965 0999235 131130 15313 09801 04446 76222 09677 96025 29773 09125 1670934 08786 07696 0967740 116023 87149 09721 01413 94353 09199 88507 121932 07702 1510619 00699 01783 0900650 113469 368745 09940 00741 107578 08544 102382 164501 07087 3209413 00351 00818 08492





Competing Interests


Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b) (c)

(d) (e) (f)


AC2

Attapulgite

Sodium alginate

1419

1034

14211027

35513585

3616

36143582

3553





(061

)

Qua

rts

(121

)(0

40)

(110

)(1

10)

(200

)(2

00)

(130

)(1

30)

Attapulgite


(040

)(1

21)

Qua

rts

(061

)

20 30 40 50 60 70102120579 (deg)







minus08

minus07

minus06

minus05

minus04

minus03

minus02

minus01

00

dW

dT

10

20

30

40

50

60

70

80

90

100W

eigh

t (

)

200 300 400 500 600 700100T (∘C)

100 150 200 250 300 350 400 450 500 550 600 650 70050T (∘C)


(a) (b)






2

4

6

8

Qe

(mg g

minus1 )





(a) (b) (c)




119876119905 =111989621198762eq+ 1119876eq 119905 119905119876119905 versus 119905 [33]



76

78

80

82

84

86

88

90

Qe

(mg g

minus1 )

4 6 8 102pH




5 10 15 20 25 30 35 40 45 50 550t (h)

0

2

4

6

8

10

Con

cent

ratio

n (m

g Lminus

1 )

00

05

10

15

20

25

30

35

40

45

50

Qt

(mg g

minus1 )





119879 (∘C)

Pseudo-first-order

equation




25 011309 09952 001674 09779 07593 08746 13717 07705 09687



119876eq =1119876max+ 1119876max119887

1119862119890 1119876eq versus 1119862119890 [37]


Sips 119876eq = 1198761198981198871198621119899

119890

1 + 1198871198621119899119890119876eq versus 119862119890 [39]


25∘C

30∘C

35∘C

40∘C

50∘C

02 04 06 08 10 12 14 16 18 20 22 24 26 2800Ce (mg Lminus1)

4

5

6

7

8

9

10

11

12

Qe

(mg g

minus1 )






4 Conclusions





model Sips model


119864(kJmol) 119877

2 119876max(mg gminus1) 119887 1119899 1198772

25 112284 46800 09365 02410 88710 09282 87615 63976 08012 1231803 00795 02963 0915330 141965 07031 09875 05227 57221 09991 91354 20422 09360 516949 01252 05965 0999235 131130 15313 09801 04446 76222 09677 96025 29773 09125 1670934 08786 07696 0967740 116023 87149 09721 01413 94353 09199 88507 121932 07702 1510619 00699 01783 0900650 113469 368745 09940 00741 107578 08544 102382 164501 07087 3209413 00351 00818 08492





Competing Interests


Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






minus08

minus07

minus06

minus05

minus04

minus03

minus02

minus01

00

dW

dT

10

20

30

40

50

60

70

80

90

100W

eigh

t (

)

200 300 400 500 600 700100T (∘C)

100 150 200 250 300 350 400 450 500 550 600 650 70050T (∘C)


(a) (b)






2

4

6

8

Qe

(mg g

minus1 )





(a) (b) (c)




119876119905 =111989621198762eq+ 1119876eq 119905 119905119876119905 versus 119905 [33]



76

78

80

82

84

86

88

90

Qe

(mg g

minus1 )

4 6 8 102pH




5 10 15 20 25 30 35 40 45 50 550t (h)

0

2

4

6

8

10

Con

cent

ratio

n (m

g Lminus

1 )

00

05

10

15

20

25

30

35

40

45

50

Qt

(mg g

minus1 )





119879 (∘C)

Pseudo-first-order

equation




25 011309 09952 001674 09779 07593 08746 13717 07705 09687



119876eq =1119876max+ 1119876max119887

1119862119890 1119876eq versus 1119862119890 [37]


Sips 119876eq = 1198761198981198871198621119899

119890

1 + 1198871198621119899119890119876eq versus 119862119890 [39]


25∘C

30∘C

35∘C

40∘C

50∘C

02 04 06 08 10 12 14 16 18 20 22 24 26 2800Ce (mg Lminus1)

4

5

6

7

8

9

10

11

12

Qe

(mg g

minus1 )






4 Conclusions





model Sips model


119864(kJmol) 119877

2 119876max(mg gminus1) 119887 1119899 1198772

25 112284 46800 09365 02410 88710 09282 87615 63976 08012 1231803 00795 02963 0915330 141965 07031 09875 05227 57221 09991 91354 20422 09360 516949 01252 05965 0999235 131130 15313 09801 04446 76222 09677 96025 29773 09125 1670934 08786 07696 0967740 116023 87149 09721 01413 94353 09199 88507 121932 07702 1510619 00699 01783 0900650 113469 368745 09940 00741 107578 08544 102382 164501 07087 3209413 00351 00818 08492





Competing Interests


Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b) (c)




119876119905 =111989621198762eq+ 1119876eq 119905 119905119876119905 versus 119905 [33]



76

78

80

82

84

86

88

90

Qe

(mg g

minus1 )

4 6 8 102pH




5 10 15 20 25 30 35 40 45 50 550t (h)

0

2

4

6

8

10

Con

cent

ratio

n (m

g Lminus

1 )

00

05

10

15

20

25

30

35

40

45

50

Qt

(mg g

minus1 )





119879 (∘C)

Pseudo-first-order

equation




25 011309 09952 001674 09779 07593 08746 13717 07705 09687



119876eq =1119876max+ 1119876max119887

1119862119890 1119876eq versus 1119862119890 [37]


Sips 119876eq = 1198761198981198871198621119899

119890

1 + 1198871198621119899119890119876eq versus 119862119890 [39]


25∘C

30∘C

35∘C

40∘C

50∘C

02 04 06 08 10 12 14 16 18 20 22 24 26 2800Ce (mg Lminus1)

4

5

6

7

8

9

10

11

12

Qe

(mg g

minus1 )






4 Conclusions





model Sips model


119864(kJmol) 119877

2 119876max(mg gminus1) 119887 1119899 1198772

25 112284 46800 09365 02410 88710 09282 87615 63976 08012 1231803 00795 02963 0915330 141965 07031 09875 05227 57221 09991 91354 20422 09360 516949 01252 05965 0999235 131130 15313 09801 04446 76222 09677 96025 29773 09125 1670934 08786 07696 0967740 116023 87149 09721 01413 94353 09199 88507 121932 07702 1510619 00699 01783 0900650 113469 368745 09940 00741 107578 08544 102382 164501 07087 3209413 00351 00818 08492





Competing Interests


Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





119879 (∘C)

Pseudo-first-order

equation




25 011309 09952 001674 09779 07593 08746 13717 07705 09687



119876eq =1119876max+ 1119876max119887

1119862119890 1119876eq versus 1119862119890 [37]


Sips 119876eq = 1198761198981198871198621119899

119890

1 + 1198871198621119899119890119876eq versus 119862119890 [39]


25∘C

30∘C

35∘C

40∘C

50∘C

02 04 06 08 10 12 14 16 18 20 22 24 26 2800Ce (mg Lminus1)

4

5

6

7

8

9

10

11

12

Qe

(mg g

minus1 )






4 Conclusions





model Sips model


119864(kJmol) 119877

2 119876max(mg gminus1) 119887 1119899 1198772

25 112284 46800 09365 02410 88710 09282 87615 63976 08012 1231803 00795 02963 0915330 141965 07031 09875 05227 57221 09991 91354 20422 09360 516949 01252 05965 0999235 131130 15313 09801 04446 76222 09677 96025 29773 09125 1670934 08786 07696 0967740 116023 87149 09721 01413 94353 09199 88507 121932 07702 1510619 00699 01783 0900650 113469 368745 09940 00741 107578 08544 102382 164501 07087 3209413 00351 00818 08492





Competing Interests


Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






model Sips model


119864(kJmol) 119877

2 119876max(mg gminus1) 119887 1119899 1198772

25 112284 46800 09365 02410 88710 09282 87615 63976 08012 1231803 00795 02963 0915330 141965 07031 09875 05227 57221 09991 91354 20422 09360 516949 01252 05965 0999235 131130 15313 09801 04446 76222 09677 96025 29773 09125 1670934 08786 07696 0967740 116023 87149 09721 01413 94353 09199 88507 121932 07702 1510619 00699 01783 0900650 113469 368745 09940 00741 107578 08544 102382 164501 07087 3209413 00351 00818 08492





Competing Interests


Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Attapulgite Nanofiber-Cellulose ...downloads.hindawi.com/journals/ijps/2016/2081734.pdfResearch Article Attapulgite Nanofiber-Cellulose Nanocomposite with Core-Shell