Research Article The Application of Response Surface ...Research Article The Application of Response Surface Methodology for Lead Ion Removal from Aqueous Solution Using Intercalated

Hindawi Publishing CorporationInternational Journal of Chemical EngineeringVolume 2013 Article ID 937675 7 pageshttpdxdoiorg1011552013937675

Research ArticleThe Application of Response Surface Methodology forLead Ion Removal from Aqueous Solution Using IntercalatedTartrate-Mg-Al Layered Double Hydroxides

Yamin Yasin1 Maszlin Mohamad2 and Faujan B H Ahmad2

1 INTEC Education College Universiti Teknologi MARA 40450 Shah Alam Malaysia2 Faculty of Applied Sciences Universiti Teknologi MARA 40450 Shah Alam Malaysia

Correspondence should be addressed to Yamin Yasin yamin961salamuitmedumy

Received 19 October 2012 Revised 15 January 2013 Accepted 19 January 2013

Academic Editor Deepak Kunzru

Copyright copy 2013 Yamin Yasin 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

Layered double hydroxide intercalated with tartrate (tartrate-Mg-Al) was used as an adsorbent to remove lead ions from aqueoussolutionsThe effects of various optimization parameters such as contact time solution pH lead ion concentrations and adsorbentdosage were investigated by the use of Response Surface Methodology (RSM) The Response Surface Methodology (RSM) basedon a four-level four-variable Central Composite Rotatable Design (CCRD) was employed to evaluate the interactive effects of thevarious optimization parametersThe parameters were contact time (6ndash10 h) solution pH (1ndash3) adsorbent dosage (006ndash01 g) andlead ion concentrations (10ndash30mgL) The percentage of lead ions removal for each of the parameters studied was determinedby Inductively Coupled Plasma-Optical Emission Spectrophotometer Simultaneously by increasing contact time and amount ofdosage of tartrate-Mg-Al used the percentage of lead ions removal from aqueous solution will increase however the percentageremoval decreases with an increase in pH and concentrations of lead ions The experimental percentage removal recorded underoptimum conditions was compared well with the maximum predicted value from the RSM which suggest that Central CompositeRotatable Design of RSM can be used to study the removal of lead from aqueous solution by the use of tartrate-Mg-Al as anadsorbent

1 Introduction

The pollution of aqueous solution by high concentrationsof metal cations can contribute to a serious environmentalproblemThe removal ofmetal cations from aqueous solutionto a certain concentration level is therefore becoming animportant issue Adsorption is one of the effective methodsto remove metal cations from aqueous solution [1] Variousmaterials can be used as an adsorbent for the removal ofmetalcations such as activated carbon [1] biomaterials [2] and clayminerals [3] In recent years the use of clay minerals as anadsorbent were found increasing in interest and numerousstudies on the adsorption of metal cations have been carriedout by use of the metal oxides [4] metal hydroxides [5] andmetal carbonates [6] which are due to their abundance innature and good metal cations adsorption 1 properties [4ndash6]

Layered Double Hydroxide (LDH) is one of the clayminerals that have good metal cations adsorption propertieswith a negatively charged layers high anion exchange prop-erty and high surface areas The chemical composition oflayered double hydroxides can be described by the formula[M2+1minus119909

M3+119909(OH)2]119909+(A119899minus)

119909119899sdotmH2O where M2+ and M3+ are

metal cations for example Mg2+ and Al3+ that occupy octa-hedral sites in the hydroxide layers A119899minus is an exchangeableanion and x is the ratio of M3+(M2++ M3+) Carbonatesare the interlayer anions in the naturally occurring mineralhydroxides which is a member of this class of materials

Several studies have reported on the use of layereddouble hydroxides as an adsorbent for the preservationof aqueous environments such as treatment of colouredwater [7 8] treatment of water polluted with heavy metals[9 10] and as nitrogen oxide storage [11] The adsorption

2 International Journal of Chemical Engineering

properties of layered double hydroxides towardmetal cationscan be improved by intercalating layered double hydroxideswith metal chelating agents such as tartrate [5] Recentlyseveral studies on the intercalated compounds of layereddouble hydroxides which can be used as an adsorbent forthe removal of heavy metals have been reported Magne-sium aluminium layered double hydroxides intercalated withethylenediaminetetraacetate (EDTA) have been reported tohave successfully taken up heavy metals such as Cu2+ andCd2+ from aqueous solution and the formation of EDTA-metal complex in the interlayer of layered double hydroxidewas to be believed as the principalmechanism for the removal[9] Similar study was also reported in the use of intercalatedEDTA-zinc-aluminium layered double hydroxides for theremoval of heavy metals of Cu2+ Cd2+ and Pb2+ [10]

Response Surface Methodology (RSM) is an effective sta-tistical technique which provides an investigative approachtowards optimization In addition it is a collection ofmathematical and statistical techniques used in significanceof several affecting factors in an optimum manner evenin the presence of complex interactions [12] The mainreason for implementing RSM is to determine the optimumoperational conditions for the process or to determine aregion that satisfies the operating specifications [13] Thelimitations posed by conventional analytical optimizationmethod can be eliminated by optimizing all the affectingparameters collectively using RSM In our present studyRSM comprises of a four-level four-factor Central CompositeRotatable Design (CCRD) which was used to evaluate theinteractive effects and to obtain the optimum conditions forlead ions removal from aqueous solutions using intercalatedtartrate-Mg-Al layered double hydroxide

2 Experimental

21 Synthesis of Tartrate-Mg-Al Layered Double Hydrox-ide (Tartrate-Mg-Al) All chemicals used in this synthesiswere of analytical grade and used without any purifica-tion The coprecipitation method was adapted to synthesizetartrate-Mg-Al layered double hydroxides in this work Inthe preparation of Mg-Al solution an aqueous solutionof Mg(NO

3)2sdot6H2O and Al(NO

3)3sdot9H2O was dissolved in

deionized water to give Mg2+Al3+ ratio of 4 The tartratesolutions were prepared by dissolving the required amountof organic salt of tartrate in deionized water according to thestoichiometric quantities defined by the following equation[5]

02Mg2+ + 005Al3+ + 01C4H4O6

2minus+ 2OHminus

997888rarr Mg02Al005(OH)2(C4H4O6)

01

(1)

An aqueous solution of Mg-Al-NO3at a ratio of 4 was

then added dropwise to a solution of tartrate under nitrogenatmosphere with vigorous stirring The solution mixture waskept under nitrogen atmosphere throughout the synthesisprocess to minimize the effects of dissolved carbon dioxideThe pH of the solution mixture was kept constants at a pHof 10 by adding a sodium hydroxide solution The resulting

Table 1 The level and range of independent variables chosen forremoval of lead from aqueous solution using tartrate-Mg-Al layereddouble hydroxide

Factor Variable UnitRange and level of actual and

coded valuesLow actual (minus1) High actual (+1)

119860 Time hour 6 10119861 pH mdash 1 3119862 Dosage mg 006 01119863 Concentration mgL 10 30

slurry was aged at 70∘C for 24 hours in an oil batch shaker andwas then filtered and washed with deionized water to removefree ions and excess organic salt The material was then driedin an oven at 60∘C for 24 hours andwas kept in sample bottlesfor further use and characterizations

22 Characterization of Original Mg-Al Layered DoubleHydroxide (Mg-Al-NO

3) and Tartrate-Mg-Al Layered Double

Hydroxide (Tartrate-Mg-Al) The X-ray Diffraction (XRD)patterns of Mg-Al-NO

3and tartrate-Mg-Al layered dou-

ble hydroxide before and after removal experiments wereobtained by PANlytical Xrsquopert Pro using Ni-filtered Cu

120572

radiation 60KV and 60mA The basal spacing (119889-spacing)of the compounds was determined via powder technique Allsolid samplesweremounted onPW18xx sample holder seriesand the scans were done at 5∘ndash90∘ over 2120579min at 0003∘ steps

23 Experimental Design A four-level four-factor CCRDdesignwas employed in this study leading to a set of 15 exper-imentsThe variables and their levels selected for the study ofthe removal of lead ions using tartrate-Mg-Al layered doublehydroxide were contact time (6ndash10 h) adsorbent dosage(006ndash01 g) solution pH (1ndash3) and lead ion concentrations(10ndash30mgL) based on the preliminary experiments usingconventional optimization method as shown in Table 1 Thevariables and their respective levels are presented in Table 2which represents the actual experiments (in triplicate) carriedout for developing themodelThe data obtainedwere fitted toa second-order polynomial equation

119910 = 120573

0+

4

sum

119894=1

120573

119894119909

119894+

4

sum

119894=1

120573

119894119894119909

2+

3

sum

119894=1

4

sum

119895=1+1

120573

119894119895119909

119894119895 (2)

where 119884 is percentage of lead ions removed 1205730 120573

119894 120573

119894119894 120573

119894119895

are constant coefficients 119909119894are the uncoded independent

variables Subsequent regression analyses analyses of vari-ance (ANOVA) and response surfaces were performed usingthe Design Expert Software (Version 604) from Stat-EaseInc (Minneapolis MN USA) Optimal reaction parametersfor maximum removal were generated using the softwarersquosnumerical optimization function

24 Batch Adsorption and Analysis Batch method wasemployed in the removal experiment of lead ions from aque-ous solution using tartrate-Mg-Al layered double hydroxides

International Journal of Chemical Engineering 3

Table 2 Central composite rotatable quadratic polynomial modelexperimental data and actual and predicted values for five-levelfour-factor response surface analysis

Run 119860 119861 119862 119863

Actual( Removal)

Predicted( Removal)

1 10 25 008 30 9913 99222 8 35 006 40 9715 102213 12 35 01 20 9838 95774 10 25 008 30 9923 99225 8 35 006 20 9905 106876 12 15 01 20 9514 91067 10 25 008 30 9923 99228 10 25 004 30 7315 56469 10 25 008 30 9923 992210 10 05 008 30 34 74011 10 25 008 50 918 904912 10 25 008 30 9924 992213 6 25 008 30 9748 950114 12 35 006 40 9923 1055715 10 25 012 30 9885 1113316 12 15 006 20 2464 302817 10 45 008 30 9877 905618 8 15 01 20 9514 920319 12 15 01 40 9671 921220 8 15 006 20 3025 307021 10 25 008 30 9923 992222 14 25 008 30 9914 974023 10 25 008 10 9698 940824 8 35 01 40 9872 963125 8 15 006 40 1794 237726 8 35 01 20 9797 981927 8 15 01 40 9258 878828 12 15 006 40 2781 285829 12 35 01 40 9857 991130 12 35 006 20 9932 10501119860 time (h) 119861 pH 119862 dosage (mg)119863 concentration (mgL)

(tartrate-Mg-Al) A sample of 005 g tartrate-Mg-Al wasplaced in a 100mL Schott Duran bottles and 25mL of 20ndash40mgL lead solution was added to the bottles and agitatedby the use of shaker operating at room temperature with aspeed of 150 rpm The amount of lead ions removed () wascalculated as

119862

0minus 119862

119905

119862

0

times 100 (3)

where 1198620is the initial concentration (mM) of the lead ions

solution and 119862119905is the concentration at equilibrium at the

time 119905 At predetermined time 5mL of the solutions werewithdrawn and filtered through 045120583m Whatman syringefilter The remaining concentration of lead ions was thenmeasured by using Perkin Elmer Optima 8300 Inductive

5 10 15 20 25 30 35 40 45 50 55 60 65 70

Inte

nsity

(a)

(b)

(c)

(d)

bull 003

bull 006

bull 110

bull 009

bull009

2120579 (degrees)

802 A

838 A803 A

304 A399 A

154 A

398 A

4 A

258 A

256 A

315 A

154 A

153 A

152 A

762 A381 A

Figure 1 XRDpatterns of (a) originalMg-Al-NO3 (b)Mg-Al-NO

3-

Pb (c) tartrate Mg-Al and (d) tartrate-Mg-Al-Pb

Coupled Plasma-Optical Emission Spectrophotometer (ICP-OES) All experiments were conducted in duplicate andcontrols were simultaneously carried out to ensure that theremoval was by the adsorbent and not by the wall of theglassware In order to avoid precipitation the pH of thesolution was kept below than 6 since the solubility productof Pb(OH)

2is recorded at 143 times 10minus20 [14]

3 Results and Discussion



Hydroxide (Tartrate-Mg-Al) The structure of layered doublehydroxides (Mg-Al-NO

3) synthesized at a ratio of 4 and

the structures of intercalated compound before (tartrate-Mg-Al) and after removal of lead (tartrate-Mg-Al-Pb) ionswere characterized and their XRD patterns were shown inFigure 1 As shown in Figure 1(a) original layered doublehydroxides (Mg-Al-NO

3) indicate fairly good crystallinity

This was proved by the 119889-spacing recorded at 76 A thatdemonstrated general features of layered double hydroxides[15ndash17] The 119889-spacing shows the characteristic values fortrigonal structures with a strong sharp and symmetricalpeaks assigned to (003) and (006) planes respectively Theinterlayer spacing of the sample corresponding to the (006)plane was found to be 38 A

The original XRD patterns of tartrate-Mg-Al (Figure 1(c))show broader in patterns as compared to the original Mg-Al-NO

3which suggest that tartrate-Mg-Al had the common

structure of the Mg-Al-NO3 The basal spacing for tartrate-

Mg-Al recorded at 838 A indicates that the interlayer spacingwas larger than that of the Mg-Al-NO

3 The pattern reveals

that the intercalation of tartrate ions in the interlayer of Mg-Al-NO

3increased the basal spacing from 76 A to 838 A

The basal spacing recorded for the tartrate-Mg-Al suggeststhat the tartrate ions which are larger than the nitrate ionswere intercalated into the interlayer of Mg-Al-NO

3layered

double hydroxides [5] The XRD patterns of tartrate-Mg-Al-Pb after removal of lead ions (Figure 1(d)) show the basalspacing which is slightly lower than that of original tartrate-Mg-Al The pattern shows no additional peaks detected


Table 3 ANOVA for removal of lead from aqueous solution usingtartrate-Mg-Al layered double hydroxide

Source Degree offreedom

Sum ofsquares

Meansquare 119865 value 119875

Model 14 2435042 173932 3086 lt00010Residual 15 84543 5636Lack of fit 10 84542 8454 4830997 lt00010Pure error 5 000875 000175Total 29 2519586Time (119860) 1 854 854 015 07025pH (119861) 1 1037172 1037172 18402 lt00010Dosage (119862) 1 451608 451608 8013 lt00010Concentration(119863) 1 1933 1933 034 05668

for precipitation products of lead which indicates that themain mechanism for the removal of lead ion is not throughthe surface precipitation reaction between lead ions andhydroxide ions Therefore the result suggests that the mainmechanism for the removal of lead is through the formationof metal complexes between the lead ions and the tartrateswhich are formed in the interlayer of tartrate-Mg-Al layereddouble hydroxides

32 Model Development The coefficients of the empiricalmodel and their statistical analyses evaluated using theDesign Expert Software are presented in Table 3 The pre-dicted values were obtained from themodel-fitting techniqueusing the Design Expert Software version 604 and were seento be sufficiently correlated with the observed values Fittingof the data to various models (linear two factorial quadraticand cubic) and their subsequent ANOVA showed that theremoval of lead ions from aqueous solution using tartrate-Mg-Al layered double hydroxide was suitably described byquadratic model From the Design Expert Software thequadratic polynomial is given as follows

Removal () = 9922 + 060119860 + 2079119861 + 1372119862

minus 090119863 minus 075119860

2minus 1256119861

2

minus 383119862

2minus 173119863

2minus 036119860119861

minus 014119860119862 + 130119860119863 minus 1750119861119862

+ 057119861119863 + 069119862119863

(4)

where 119860 is contact time 119861 is solution pH 119862 is the amount ofdosage and119863 is the concentration

The computed model 119865-value of 3086 was higher thanthe tabular value implying that the model is significant at1 confidence level There is only a 001 chance that themodel 119865-value large could occur due to noise The modelalso showed a very low value of pure error of 00087which indicates good reproducibility of the data obtainedThe values of ldquoProb gt 119865rdquo less than 00500 indicate thesignificance of the model Based on the analyzed results the

6416

7508

86

9692

10784

Rem

oval

()

8 9

10 11

12

15 2

25

3 35

A time

B pH

Figure 2 Response surface plot showing the effect of contact timeand pH and theirmutual effect on the removal of lead using tartrate-Mg-Al layered double hydroxide

solution pH the adsorbent dosage and the combination ofpH and adsorbent dosage are significant model terms Thehigh coefficient of determination (1198772 = 09664) showed thatthe quadratic polynomial was highly significant and sufficientto represent the actual relationship between the removal ()and the significant variables

33 Response Surface Plots The quadratic polynomial equa-tion was then used to facilitate plotting of response surfacesTwo parameters were plotted at any one time on the 119909

1and

119909

2axes respectively with the other remaining parameters set

at their center points values (coded level 0) Figure 2 showsthe profile of contact time versus pH of lead solution forremoval of lead ions from aqueous solution using tartrate-Mg-Al layered double hydroxide A response surface plot forinteraction between contact time and pH of lead solutionwas generated with the parameters of amount of dosageand concentrations fixed at center points of (005 g) and(30mgL) respectively under any given conditions FromFigure 2 at any given pH of lead solutions from 1 to 3 anincrease in contact time led to a higher percentage removalAn increase in pHup to 10 resulted in a decrease in percentageremoval of lead ions The metal cations in layered doublehydroxides layers begin to dissolve at high pH which resultedin the decrease of lead removal at high pH Removal of leadfrom aqueous solution using tartrate-Mg-Al layered doublehydroxide as an adsorbent with moderate pH and maximumcontact time favored maximal percentage removal

Response surface predicted the interaction of contacttime and amount of adsorbent dosage are illustrated inFigure 3 with the concentration of lead solution set at centerpoint value of 30mgL As shown in Figure 3 at any givenamount of layered double hydroxide dosage from 006 to01 g an increase in contact time led to a higher percentage


8018

8743

9468

10192

10917

8 9

11 10

12

006 007

008

009 01

A time

C dosage

Rem

oval

()

Figure 3 Response surface plot showing the effect of contact timeand amount of dosage and their mutual effect on the removal of leadusing tartrate-Mg-Al layered double hydroxide

removal of lead ions Removal with the highest dosage andhighest contact time favored maximal percentage removalThe similar trend of profile in contact time versus amount ofdosage also has been previously found and has indeed beenreported [18 19]

The response surface presented in Figure 4 shows theeffect of contact time and concentration of lead solution ata fixed pH and adsorbent dosage on the percentage removalof lead using tartrate-Mg-Al layered double hydroxide Asshown in Figure 4 adsorption at the highest contact timeand low concentration of lead solution favors maximum per-centage removal The percentage removal of lead decreaseswith increasing concentrations of lead solutionThis explainsa common observation that the percentage removal of leadis decreased due to the limiting amount of tartrate-Mg-Aldosage used that could inhibit the formation of complexesbetween tartrate and lead ions with an increase in con-centrations of lead solution This can be attributed to thedecrease in the area for the formation of complexes withthe increase of lead solution concentration Figures 5 and 6present the response surface plots as functions of pH versuslead solution concentration and pH versus dosage of tartrate-Mg-Al layered double hydroxide respectively As expectedthe percentage removal of lead is maximized at the highestlead concentrations and moderate pH

Figure 7 presents the effect of varying the lead ion con-centrations and the tartrate-Mg-Al dosages At low dosagesand low concentrations of lead solution the percentageremoval of lead was lower and this was attributed to a limitedaffective area for the formation of complexes between leadand tartrate ions and the decrease in probability of lead ions tofind a site for the formation of complexes Higher percentageremoval is achieved with high amounts of tartrate-Mg-Aland high concentrations of lead solution because larger

9393

9529

9665

98

9936

Rem

oval

()

8 9

10 11

12

20

25

30

35

40

A tim

e

D concentration

Figure 4 Response surface plot showing the effect of contact timeand concentration of lead and their mutual effect on the removal oflead using tartrate-Mg-Al layered double hydroxide

6267

7396

8525

9654

10783

Rem

oval

()

15 2

25

3 35

20

25

30

3540

B pH

D concentration

Figure 5 Response surface plot showing the effect of pH andconcentration of lead and their mutual effect on the removal of leadusing tartrate-Mg-Al layered double hydroxide

quantities of lead ions increase the ratio of the adsorbate toadsorbent thus promoting the formation of complexes as wellas increasing the percentage removal

34 Optimum Conditions Within the experimental rangestudied the optimum conditions for lead ion removal usingtartrate-Mg-Al have been predicted using Design Expertrsquosoptimization function The optimum conditions are pre-sented in Table 3 along with their predicted and actual valuesThe analysis indicates that a maximum percentage removal


3082

5044

7006

8968

10931

Rem

oval

()

15 2

25 3

35

006 007

008

009

01

B pH C dosage

Figure 6 Response surface plot showing the effect of pH andamount of dosage and their mutual effect on the removal of leadusing tartrate-Mg-Al layered double hydroxide

7834

8603

9373

10142

10911

Rem

oval

()

006 007

008 009

01

2025

30

3540

C dosag

e

D concentration

Figure 7 Response surface plot showing the effect concentration oflead and amount of dosage and their mutual effect on the removalof lead using tartrate-Mg-Al layered double hydroxide

of lead ion requires a contact time of 798 hours an initialconcentration of 4009mgL adsorbent dosage of 006 g anda pH of 352 The predicted and experimental percentageremoval values of 9922 and 9832 under these conditionsare in good agreement implying that the empirical modelderived by RSM could be used adequately to describe therelationship between the factors and response with respectto the removal of lead ions using tartrate-Mg-Al layereddouble hydroxide The results of the study were supportedby previously reported paper on the optimization of leadremoval from aqueous solution using specific adsorbents

Table 4 Predicted removal from the design experiments for theremoval of lead by the use of other adsorbents

Adsorbents Predicted removalImmobilized Pycnoporus sanguineus 977Biomass of Aeromonas hydrophila 986Polyvinyl alcohol semi-IPN poly(acrylicacid)tourmaline composite 68ndash69

[20ndash22] As shown in Table 4 the predicted and experimentalpercentage removals of lead from the design experiments arein agreement which was implying that the model can beused adequately to study the removal of lead from aqueoussolution using other adsorbents

4 Conclusion

The adequacy of the predicted model was evaluated byperforming additional independent experiments using sug-gested optimal removal conditions From the data obtainedthe observed values were statistically near the predicted val-ues and hence it can be concluded that the generated modeladequately predicted the percentage removalThe removal oflead using tartrate-Mg-Al layered double hydroxide has beensuccessfully described through the development of a modelusing Response Surface Methodology fractional factorialdesign

Nomenclature

119862

0 Initial concentration of lead ion solution

(mgL)119862

119905 Concentration of lead ion solution at the

desired time 119905 (mgL)119909

119894 Uncoded independent variables119884 Predicted response119860 Time119861 pH119862 Dosage119863 Initial concentrationExp Experimental valuePred Predicted valueANOVA Analysis of variance

Greek Letters

120573

0 Offset term120573

119894 Linear effect120573

119894119894 Squared effect120573

119894119895 Interaction effect

Acknowledgment

The authors thank Universiti Teknologi MARA for financialsupport under Excellent Research Grant Scheme


References

[1] J P Chen and S Wu ldquoAcidbase-treated activated carbonscharacterization of functional groups and metal adsorptivepropertiesrdquo Langmuir vol 20 no 6 pp 2233ndash2242 2004

[2] V K Gupta A Rastogi V K Saini and N Jain ldquoBiosorptionof copper(II) from aqueous solutions by Spirogyra speciesrdquoJournal of Colloid and Interface Science vol 296 no 1 pp 59ndash632006

[3] J U KOubagaranadin andZV PMurthy ldquoIsothermmodelingand batch adsorber design for the adsorption of Cu(II) on a claycontaining montmorilloniterdquo Applied Clay Science vol 50 no3 pp 409ndash413 2010

[4] M Hua S Zhang B Pan W Zhang L Lv and Q ZhangldquoHeavy metal removal from waterwastewater by nanosizedmetal oxidesrdquo Journal of Hazardous Materials vol 211 pp 317ndash331 2012

[5] T Kameda H Takeuchi and T Yoshioka ldquoUptake of heavymetal ions from aqueous solution using MgndashAl layered doublehydroxides intercalated with citrate malate and tartraterdquo Sep-aration and Purification Technology vol 62 no 2 pp 330ndash3362008

[6] A Sdiri T Higashi T Hatta F Jamoussi and N TaseldquoEvaluating the adsorptive capacity of montmorillonitic andcalcareous clays on the removal of several heavy metals inaqueous systemsrdquo Chemical Engineering Journal vol 172 no 1pp 37ndash46 2011

[7] Yasin A H Abdul Malik S M Sumari and F B H AhmadldquoRemoval of amido black dye from aqueous solution by uncal-cined and calcined hydrotalciterdquo Research Journal of Chemistryand Environment vol 14 no 1 pp 78ndash84 2010

[8] Y Yasin A H Abdul Malik and S M Sumari ldquoAdsorptionof eriochrome black dye from aqueous solution onto anioniclayered double hydroxidesrdquo Oriental Journal of Chemistry vol26 no 4 pp 1293ndash1298 2010

[9] T Kameda S Saito and Y Umetsu ldquoMg-Al layered dou-ble hydroxide intercalated with ethylene-diaminetetraacetateanion synthesis and application to the uptake of heavy metalions from an aqueous solutionrdquo Separation and PurificationTechnology vol 47 no 1-2 pp 20ndash26 2005

[10] D Zhao G Sheng J Hu C Chen and X Wang ldquoTheadsorption of Pb(II) on Mg

2Al layered double hydroxiderdquo

Chemical Engineering Journal vol 171 no 1 pp 167ndash174 2011[11] J Cheng X Wang C Ma and Z Hao ldquoNovel Co-Mg-Al-Ti-

O catalyst derived from hydrotalcite-like compound for NOstoragedecompositionrdquo Journal of Environmental Science vol24 no 3 pp 488ndash493 2012

[12] K Ravikumar S Krishnan S Ramalingam and K Balu ldquoOpti-mization of process variables by the application of responsesurface methodology for dye removal using a novel adsorbentrdquoDyes and Pigments vol 72 no 1 pp 66ndash74 2007

[13] R H Myers and D C Montgomery Response Surface Method-ology John Wiley and Sons 2nd edition 2001

[14] Q Liu and Y Liu ldquoDistribution of Pb(II) species in aqueoussolutionsrdquo Journal of Colloid and Interface Science vol 268 no1 pp 266ndash269 2003

[15] F Cavani and F Trifiro ldquoHydrotalcite-type anionic clayspreparation properties and applicationsrdquo Catalysis Today vol11 no 2 pp 173ndash301 1991

[16] M Bellotto B Rebours O Clause J Lynch D Bazin andE Elkaım ldquoA reexamination of hydrotalcite crystal chemistryrdquo

Journal of Physical Chemistry vol 100 no 20 pp 8527ndash85341996

[17] K Chibwe andW Jones ldquoIntercalation of organic and inorganicanions into layered double hydroxidesrdquo Journal of the ChemicalSociety Chemical Communications no 14 pp 926ndash927 1989

[18] K Ravikumar K Pakshirajan T Swaminathan and K BaluldquoOptimization of batch process parameters using responsesurface methodology for dye removal by a novel adsorbentrdquoChemical Engineering Journal vol 105 no 3 pp 131ndash138 2005

[19] Y Yasin A H Abdul Malek and F H Ahmad ldquoResponsesurface methodology study on removal of humic acid fromaqueous solutions using anionic clay hydrotalciterdquo Journal ofApplied Sciences vol 10 no 19 pp 2297ndash2303 2010

[20] Y Yus Azila M D Mashitah and S Bhatia ldquoProcess opti-mization studies of lead (Pb(II)) biosorption onto immobilizedcells of Pycnoporus sanguineus using response surfacemethod-ologyrdquo Bioresource Technology vol 99 no 18 pp 8549ndash85522008

[21] S H Hasan P Srivastava and M Talat ldquoBiosorption of Pb(II)from water using biomass of Aeromonas hydrophila centralcomposite design for optimization of process variablesrdquo Journalof Hazardous Materials vol 168 no 2-3 pp 1155ndash1162 2009

[22] Y Zheng and A Wang ldquoRemoval of heavy metals usingpolyvinyl alcohol semi-IPNpoly(acrylic acid)tourmaline com-posite optimizedwith response surfacemethodologyrdquoChemicalEngineering Journal vol 162 no 1 pp 186ndash193 2010

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properties of layered double hydroxides towardmetal cationscan be improved by intercalating layered double hydroxideswith metal chelating agents such as tartrate [5] Recentlyseveral studies on the intercalated compounds of layereddouble hydroxides which can be used as an adsorbent forthe removal of heavy metals have been reported Magne-sium aluminium layered double hydroxides intercalated withethylenediaminetetraacetate (EDTA) have been reported tohave successfully taken up heavy metals such as Cu2+ andCd2+ from aqueous solution and the formation of EDTA-metal complex in the interlayer of layered double hydroxidewas to be believed as the principalmechanism for the removal[9] Similar study was also reported in the use of intercalatedEDTA-zinc-aluminium layered double hydroxides for theremoval of heavy metals of Cu2+ Cd2+ and Pb2+ [10]

Response Surface Methodology (RSM) is an effective sta-tistical technique which provides an investigative approachtowards optimization In addition it is a collection ofmathematical and statistical techniques used in significanceof several affecting factors in an optimum manner evenin the presence of complex interactions [12] The mainreason for implementing RSM is to determine the optimumoperational conditions for the process or to determine aregion that satisfies the operating specifications [13] Thelimitations posed by conventional analytical optimizationmethod can be eliminated by optimizing all the affectingparameters collectively using RSM In our present studyRSM comprises of a four-level four-factor Central CompositeRotatable Design (CCRD) which was used to evaluate theinteractive effects and to obtain the optimum conditions forlead ions removal from aqueous solutions using intercalatedtartrate-Mg-Al layered double hydroxide

2 Experimental

21 Synthesis of Tartrate-Mg-Al Layered Double Hydrox-ide (Tartrate-Mg-Al) All chemicals used in this synthesiswere of analytical grade and used without any purifica-tion The coprecipitation method was adapted to synthesizetartrate-Mg-Al layered double hydroxides in this work Inthe preparation of Mg-Al solution an aqueous solutionof Mg(NO

3)2sdot6H2O and Al(NO

3)3sdot9H2O was dissolved in

deionized water to give Mg2+Al3+ ratio of 4 The tartratesolutions were prepared by dissolving the required amountof organic salt of tartrate in deionized water according to thestoichiometric quantities defined by the following equation[5]

02Mg2+ + 005Al3+ + 01C4H4O6

2minus+ 2OHminus

997888rarr Mg02Al005(OH)2(C4H4O6)

01

(1)

An aqueous solution of Mg-Al-NO3at a ratio of 4 was

then added dropwise to a solution of tartrate under nitrogenatmosphere with vigorous stirring The solution mixture waskept under nitrogen atmosphere throughout the synthesisprocess to minimize the effects of dissolved carbon dioxideThe pH of the solution mixture was kept constants at a pHof 10 by adding a sodium hydroxide solution The resulting

Table 1 The level and range of independent variables chosen forremoval of lead from aqueous solution using tartrate-Mg-Al layereddouble hydroxide

Factor Variable UnitRange and level of actual and

coded valuesLow actual (minus1) High actual (+1)

119860 Time hour 6 10119861 pH mdash 1 3119862 Dosage mg 006 01119863 Concentration mgL 10 30

slurry was aged at 70∘C for 24 hours in an oil batch shaker andwas then filtered and washed with deionized water to removefree ions and excess organic salt The material was then driedin an oven at 60∘C for 24 hours andwas kept in sample bottlesfor further use and characterizations



Hydroxide (Tartrate-Mg-Al) The X-ray Diffraction (XRD)patterns of Mg-Al-NO

3and tartrate-Mg-Al layered dou-

ble hydroxide before and after removal experiments wereobtained by PANlytical Xrsquopert Pro using Ni-filtered Cu

120572

radiation 60KV and 60mA The basal spacing (119889-spacing)of the compounds was determined via powder technique Allsolid samplesweremounted onPW18xx sample holder seriesand the scans were done at 5∘ndash90∘ over 2120579min at 0003∘ steps

23 Experimental Design A four-level four-factor CCRDdesignwas employed in this study leading to a set of 15 exper-imentsThe variables and their levels selected for the study ofthe removal of lead ions using tartrate-Mg-Al layered doublehydroxide were contact time (6ndash10 h) adsorbent dosage(006ndash01 g) solution pH (1ndash3) and lead ion concentrations(10ndash30mgL) based on the preliminary experiments usingconventional optimization method as shown in Table 1 Thevariables and their respective levels are presented in Table 2which represents the actual experiments (in triplicate) carriedout for developing themodelThe data obtainedwere fitted toa second-order polynomial equation

119910 = 120573

0+

4

sum

119894=1

120573

119894119909

119894+

4

sum

119894=1

120573

119894119894119909

2+

3

sum

119894=1

4

sum

119895=1+1

120573

119894119895119909

119894119895 (2)

where 119884 is percentage of lead ions removed 1205730 120573

119894 120573

119894119894 120573

119894119895

are constant coefficients 119909119894are the uncoded independent

variables Subsequent regression analyses analyses of vari-ance (ANOVA) and response surfaces were performed usingthe Design Expert Software (Version 604) from Stat-EaseInc (Minneapolis MN USA) Optimal reaction parametersfor maximum removal were generated using the softwarersquosnumerical optimization function

24 Batch Adsorption and Analysis Batch method wasemployed in the removal experiment of lead ions from aque-ous solution using tartrate-Mg-Al layered double hydroxides



Run 119860 119861 119862 119863

Actual( Removal)

Predicted( Removal)



119862

0minus 119862

119905

119862

0

times 100 (3)




5 10 15 20 25 30 35 40 45 50 55 60 65 70

Inte

nsity

(a)

(b)

(c)

(d)

bull 003

bull 006

bull 110

bull 009

bull009

2120579 (degrees)

802 A

838 A803 A

304 A399 A

154 A

398 A

4 A

258 A

256 A

315 A

154 A

153 A

152 A

762 A381 A


3-




















3layered





Sum ofsquares





Removal () = 9922 + 060119860 + 2079119861 + 1372119862

minus 090119863 minus 075119860

2minus 1256119861

2

minus 383119862

2minus 173119863

2minus 036119860119861

minus 014119860119862 + 130119860119863 minus 1750119861119862

+ 057119861119863 + 069119862119863

(4)



6416

7508

86

9692

10784

Rem

oval

()

8 9

10 11

12

15 2

25

3 35

A time

B pH




1and

119909





8018

8743

9468

10192

10917

8 9

11 10

12

006 007

008

009 01

A time

C dosage

Rem

oval

()





9393

9529

9665

98

9936

Rem

oval

()

8 9

10 11

12

20

25

30

35

40

A tim

e

D concentration


6267

7396

8525

9654

10783

Rem

oval

()

15 2

25

3 35

20

25

30

3540

B pH

D concentration





3082

5044

7006

8968

10931

Rem

oval

()

15 2

25 3

35

006 007

008

009

01

B pH C dosage


7834

8603

9373

10142

10911

Rem

oval

()

006 007

008 009

01

2025

30

3540

C dosag

e

D concentration






4 Conclusion


Nomenclature

119862


(mgL)119862




Greek Letters

120573

0 Offset term120573


119894119894 Squared effect120573


Acknowledgment



References




























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











Run 119860 119861 119862 119863

Actual( Removal)

Predicted( Removal)



119862

0minus 119862

119905

119862

0

times 100 (3)




5 10 15 20 25 30 35 40 45 50 55 60 65 70

Inte

nsity

(a)

(b)

(c)

(d)

bull 003

bull 006

bull 110

bull 009

bull009

2120579 (degrees)

802 A

838 A803 A

304 A399 A

154 A

398 A

4 A

258 A

256 A

315 A

154 A

153 A

152 A

762 A381 A


3-




















3layered





Sum ofsquares





Removal () = 9922 + 060119860 + 2079119861 + 1372119862

minus 090119863 minus 075119860

2minus 1256119861

2

minus 383119862

2minus 173119863

2minus 036119860119861

minus 014119860119862 + 130119860119863 minus 1750119861119862

+ 057119861119863 + 069119862119863

(4)



6416

7508

86

9692

10784

Rem

oval

()

8 9

10 11

12

15 2

25

3 35

A time

B pH




1and

119909





8018

8743

9468

10192

10917

8 9

11 10

12

006 007

008

009 01

A time

C dosage

Rem

oval

()





9393

9529

9665

98

9936

Rem

oval

()

8 9

10 11

12

20

25

30

35

40

A tim

e

D concentration


6267

7396

8525

9654

10783

Rem

oval

()

15 2

25

3 35

20

25

30

3540

B pH

D concentration





3082

5044

7006

8968

10931

Rem

oval

()

15 2

25 3

35

006 007

008

009

01

B pH C dosage


7834

8603

9373

10142

10911

Rem

oval

()

006 007

008 009

01

2025

30

3540

C dosag

e

D concentration






4 Conclusion


Nomenclature

119862


(mgL)119862




Greek Letters

120573

0 Offset term120573


119894119894 Squared effect120573


Acknowledgment



References




























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












Sum ofsquares





Removal () = 9922 + 060119860 + 2079119861 + 1372119862

minus 090119863 minus 075119860

2minus 1256119861

2

minus 383119862

2minus 173119863

2minus 036119860119861

minus 014119860119862 + 130119860119863 minus 1750119861119862

+ 057119861119863 + 069119862119863

(4)



6416

7508

86

9692

10784

Rem

oval

()

8 9

10 11

12

15 2

25

3 35

A time

B pH




1and

119909





8018

8743

9468

10192

10917

8 9

11 10

12

006 007

008

009 01

A time

C dosage

Rem

oval

()





9393

9529

9665

98

9936

Rem

oval

()

8 9

10 11

12

20

25

30

35

40

A tim

e

D concentration


6267

7396

8525

9654

10783

Rem

oval

()

15 2

25

3 35

20

25

30

3540

B pH

D concentration





3082

5044

7006

8968

10931

Rem

oval

()

15 2

25 3

35

006 007

008

009

01

B pH C dosage


7834

8603

9373

10142

10911

Rem

oval

()

006 007

008 009

01

2025

30

3540

C dosag

e

D concentration






4 Conclusion


Nomenclature

119862


(mgL)119862




Greek Letters

120573

0 Offset term120573


119894119894 Squared effect120573


Acknowledgment



References




























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










8018

8743

9468

10192

10917

8 9

11 10

12

006 007

008

009 01

A time

C dosage

Rem

oval

()





9393

9529

9665

98

9936

Rem

oval

()

8 9

10 11

12

20

25

30

35

40

A tim

e

D concentration


6267

7396

8525

9654

10783

Rem

oval

()

15 2

25

3 35

20

25

30

3540

B pH

D concentration





3082

5044

7006

8968

10931

Rem

oval

()

15 2

25 3

35

006 007

008

009

01

B pH C dosage


7834

8603

9373

10142

10911

Rem

oval

()

006 007

008 009

01

2025

30

3540

C dosag

e

D concentration






4 Conclusion


Nomenclature

119862


(mgL)119862




Greek Letters

120573

0 Offset term120573


119894119894 Squared effect120573


Acknowledgment



References




























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










3082

5044

7006

8968

10931

Rem

oval

()

15 2

25 3

35

006 007

008

009

01

B pH C dosage


7834

8603

9373

10142

10911

Rem

oval

()

006 007

008 009

01

2025

30

3540

C dosag

e

D concentration






4 Conclusion


Nomenclature

119862


(mgL)119862




Greek Letters

120573

0 Offset term120573


119894119894 Squared effect120573


Acknowledgment



References




























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










References




























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









Documents

Research Article The Application of Response Surface ...Research Article The Application of Response Surface Methodology for Lead Ion Removal from Aqueous Solution Using Intercalated