Research ArticleAdsorption of Arsenate from Aqueous Solution onto ModifiedVietnamese Bentonite

Nguyen Le My Linh1 Duc Hoang Van1 Tran Duong1 Mai Xuan Tinh2

and Dinh Quang Khieu 2

1University of Education Hue University Hue 530000 Vietnam2University of Sciences Hue University Hue 530000 Vietnam

Correspondence should be addressed to Dinh Quang Khieu dqkhieuhueunieduvn

Received 15 January 2019 Accepted 13 March 2019 Published 11 April 2019

Academic Editor Frederic Dumur

Copyright copy 2019 Nguyen Le My Linh et al -is is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

In this study pillared layered clays were prepared by modifying Vietnamese bentonite with polymeric Al and Fe -e obtainedmaterials were characteristic of X-ray diffraction analysis thermal analysis and nitrogen adsorptiondesorption isotherms -eresults indicated that hydroxy-aluminum ([Al13O4(OH)24(H2O)12]7+) and poly-hydroxyl-Fe or polyoxo-Fe cations were intercalatedinto layers of clay resulting in an increase of d001 values and of the specific surface areas compared with those of initial bentoniteModified bentonites were employed to adsorb As(V) from aqueous solution -e adsorption of As(V) was strongly dependent onsolution pH and themaximum adsorption of modified bentonites was obtained in the pH 30 for Fe-bentonite and the pH 40 for Al-bentonite -e equilibrium adsorption study showed that the data were well fit by the Langmuir isotherm model -e maximummonolayer adsorption capacity of As(V) at 30degC derived from the Langmuir equation was 3571mgg for Al-bentonite and 1898mgg for Fe-bentonite Adsorption kinetics thermodynamics and reusability of modified bentonites have been addressed

1 Introduction

Arsenic is a potentially toxic metal that is said to be one ofthe most concerned contaminants in aquatic sources Manyapproaches have been reported for the removal of arsenicincluding membrane dialysis oxidationreductionprecipitationcoprecipitation filtration and adsorptionand ion exchange [1] Among them adsorption is recog-nized as one of the most promising method due to highefficiency and low cost Various materials such as dolomite[2] chitosan [3] zeolites [4] organic clays [1] pillaredinterlayered clay [5 6] activated carbon [7] metal oxides[8] and reduced metals [9] have been applied as adsorbentsto eliminate arsenic from aqueous solutions Many reportsdemonstrate that clays and modified clays have great po-tential to adsorb arsenic from contaminated water Amongthe modified clays pillared interlayered clays (PILCs) bymeans of the replacement of the exchangeable interlayercations with Al13 Fe13 Keggin ions have attracted extensive

attention [10ndash12] -e surface area and pore volume of thesePILCs are greatly enhanced so that they are used as effectiveadsorbents for arsenate removal Ramesh et al [5] reportedthat the maximum arsenate adsorption of AlFe-modifiedmontmorillonite was about 2123mgg (pH 30ndash60) Luengoet al [6] studied the arsenate adsorption on a Fe(III)-modified montmorillonite -e authors concluded thatboth monomericpolymeric Fe(III) species in the interlayerand on the external surface were responsible for arsenateadsorption Zhao et al [10] have proven that the adsorptioncapacity of the montmorillonites for As(V) was significantlypromoted with increasing Al13 content -e experimentalresults showed the important role of the high positive chargeof Al13 in the improvement of adsorption capacity of themodified montmorillonites However up to now less effortshave been paid on both mechanism kinetics and ther-modynamics of arsenate adsorption onto inorganic clay

In the present article the preparation of pillared layeredclays by modification of bentonite with polymeric Al and Fe

HindawiAdvances in Materials Science and EngineeringVolume 2019 Article ID 2710926 13 pageshttpsdoiorg10115520192710926

and the removal of As(V) from aqueous solution weredemonstrated

2 Experimental

21 Materials Bentonite was obtained from Vietnamesemining company and purified by the sedimentation com-bined with sonication and centrifugation Aluminumchloride (AlCl3middot6H2O 99) ferric nitrate nonahydrate(Fe(NO3)3middot9H2O 99) silver nitrate (AgNO3 98) andsodium hydroxide (NaOH 98) were obtained fromGuangzhou company China Stock solution of H3AsO4100mgL was purchased from Merck Chemical composi-tion in mass analyzed by EDX of SiO2 Al2O3 Fe2O3 TiO2MgO CaO K2O and Na2O in mass is 691 187 44 037419 293 025 and 007 respectively -e cation exchangecapacity (CEC) was found to be 075mmolg

22 Characterization X-ray diffraction (XRD) patterns wereobtained on D8-Advance Brucker Germany with CuKαradiation -ermogravimetric (TG) analysis was recorded onDTG-60H (Shimadzu) from 25 to 1000degC at a heating rate of10degCmin under air atmosphere Fourier transform infraredspectra (FTIR) were carried out on SHIMADZU FT-IR8010M Nitrogen adsorptiondesorption isotherms wereperformed on Tri Star 3000 Before adsorptionmeasurementsthe specimen of 125 gramwas outgassed for 5 h at 250degC BETspecific surface area was calculated from the nitrogen ad-sorption data with the relative pressure ranged from 004 to025 Scanning electron microscopy (Hitachi S-4500) wasused to analyze the morphology of the obtained samples ApH meter (Horiba F-52) was employed for pH measure-ments -e point of zero charge (pHPZC) of bentonite andpolymeric AlFe-modified bentonite was calculated by the pHdrift method Arsenate was analyzed by means of atomicabsorption spectroscopy (AAS SHIMADZU-6800)

23 Preparation of Fe-Bentonite and Al-Bentonite -e pu-rified bentonite was noted as B -e Fe pillaring solutionprepared from Fe(NO3)middot9H2O and NaOH with OHminusFe3+molar ratio of 03 was stirred for 2 h and then aged in 24 h atambient temperature-emixture of B (10 g) and 100mL ofdeionized water was vigorously stirred for 1 h After that theFe pillaring solution was added slowly into the suspensioncontaining the bentonite (the ratio of 10mmol Feg drybentonite) the mixture was stirred for 24 h at room tem-perature -e solid was separated by centrifugation anddried at 100degC for 10 h -e obtained polymeric Fe-modifiedbentonite was denoted as Fe-B -e Al pillaring solution wasprepared by adding 01M NaOH to 01M AlCl3 solutionwith vigorous stirring to obtain the [OHminus][Al3+] molar ratioof 24 -en the pillaring solution was vigorously stirred for7 h at 70degC and aged for 24 h at ambient temperature Afterthe aging process the solution was slowly dropped undervigorous stirring to bentonite suspension for 24 h (24mmolAlg of dry bentonite) -e final solid was obtained by fil-tration and washed with distilled water until free of chlorides(using the AgNO3 test)-e solid was dried at 100degC for 10 h

-e obtained polymeric Al-modified bentonite was denotedas Al-B

24 Adsorption Studies Batch adsorption experiments wereperformed in 100mL flask 005 g of modified bentonite wasadded into the 100mL flasks containing 50mL solution withvarious concentrations of As(V) -e pH solution was ad-justed to the desired value by adding amounts of 001MNaOH or 001M HCl and the bottles were shaken bymagnetic stirrer for 4 h to attain equilibrium -e adsorbentwas separated by centrifugation -en the concentration ofAs(V) was analyzed by the AAS method Blank control testswere carried out for the sake of comparison

-e adsorption capacity of arsenate was calculated byusing the following equation

qt Co minusCt

mmiddot V (1)

where qt is the adsorption capacity of arsenate at time t Co(mgL) is the initial arsenate concentration Ct (mgL) is theconcentration of arsenate at time t V (L) is the volume ofarsenate solution used and m (g) is the mass of the ad-sorbent used

-e effect of pH on arsenic adsorption was investigatedin the pH ranges from 2 to 9 at ambient temperature

For kinetic experiments 02 g of adsorbent was added to250mL of known initial concentration in the pH 30 (forthe Fe-B sample) or pH 40 (for the Al-B sample) and themixture was stirred at an identical stirring speed of 600 rpmAt given time intervals about 5mL of solution was with-drawn and then centrifuged and the equilibrium concen-trations of the adsorbate were analyzed by the AAS method-e adsorption kinetics experiments were conducted at10degC 20degC 30degC and 40degC

3 Results and Discussion

31 Characterization of the Adsorbents -e XRD patterns ofB Fe-B and Al-B samples are shown in Figure 1

-e XRD patterns of B Fe-B and Al-B samples are shownin Figure 1 -e basal spacing (d001) of B is 144 nm while therecorded basal spacings were 148 nm for the Fe-B and178 nm for the Al-B Changes in the basal spacing dependedon the charge size and hydration behavior of the ion ormolecule that was located in the interlayer and on interactionsbetween it and the phyllosilicate layers [12] For the Fe-Bsample a slight increase in d001 has contributed to thepresence of polymeric species of iron within the interlayer Inaddition from Figure 1 there was no characteristics re-flections peaks of phases α βndashFeOOH Fe2O3 and Fe3O4showing that the iron oxides and hydroxides were not formedin Fe-bentonite sample It was possible that iron oxides andhydroxides were forming very fine particles absorbed ontobentonite that could not be detected by XRD to destroy a partof crystal structure of bentonite which was reflected in thedecrease of intensity of d001 peak -e interlayer spacingdistance of Al-B was 174 nm this was a proof for the suc-cessful intercalation of hydroxyaluminum polycation into the

2 Advances in Materials Science and Engineering

bentonite layers According to Hao et al [13] the size ofhydroxyaluminum polycation ([AlO4Al12(OH)24(OH2)12]7+)was of about 09 nm and the basal spacing (d001) of bentonitewas 096 nm so if there was an intercalation of ion KegginAl13 into the interlayer space of bentonite the basal spacing(d001) of bentonite would be about of 186 nm Other authors[14 15] have observed that Al13 pillared bentonite gave basalspacings between 17 and 18 A-is was explained byQin et al[11] that the value of d001 could not attain 186 nm probablydue to the delamination of bentonite

-e FTIR spectra of the samples are depicted in Figure 2-e peak at 3549 cmminus1 of B sample was assigned to Al-

Fe-OH vibration [16] the peak at 3414 cmminus1 contributed toFe-Fe-OH vibration [16] and HO-H vibration of theadsorbed water and the peak at 1638 cmminus1 was due to thedeformation band (δ(O-H)) of physically adsorbed water-e peak at 1111 cmminus1 was assigned to Si-O vibration intetrahedral If the amount of iron (Fe) in clays was high thispeak would shift to the higher position According to otherreports [1 11 17] this peak was in the range of1033ndash1041 cmminus1 indicating that bentonite was iron-richclay -e peak at 964 cmminus1 was corresponded to Si-OHvibration [18] the peak at 816 cmminus1 was because of thedeformation vibration of Fe-Fe-OH [16] and the peak at675 cmminus1 was attributed to Al-Fe-OH vibration [19]

FT-IR spectra of the Fe-B and Al-B show that somecharacteristic bands of the initial bentonite were changedPeak related to the δ(O-H) deformation shifted from1638 cmminus1 (B) to 1630 cmminus1 (Fe-B) and to 1636 cmminus1 (Al-B)with lower intensity -is could be due to the decrease of theH2O content with replacing of the intercalated FeAl pol-ycations For Al-B the peak at 3441 cmminus1 and the intensitywas higher than that of B (3414 cmminus1) -e former wascontributed to the O-H stretching vibration in hydroxyl-Alcations while the latter was corresponded to the hydroxylgroups in water-water hydrogen bands [17] -e band of Si-O vibration shifted from 1111 to 1026 cmminus1 attributing to thestrong interactions of the hydroxyl Al and bentonite layers-e FTIR results were in accordance with those of XRD

TG and DTA curves of B Fe-B and Al-B samples arepresented in Figure 3

TG and DTA curves of B Fe-B and Al-B samples arepresented in Figure 3 -ere were three main mass losses inthe TG curve for the sample without modification -e firstone below 200degC was due to physical water adsorption -esecond mass loss being broadened from 200 to 600degC couldbe assigned to the interlayer water in bentonite structure-e third mass loss in the range of the temperatures over600degC corresponding to the DTA peak 778degC was contrib-uted to the dehydroxylation of bentonite layers -e TGcurves of Fe-B and Al-B samples were similar than that of Bsample -e mass loss in the range of 20ndash200degC (Loss 1) wasassigned to physically adsorbed water -is period of the Al-B sample corresponding to the DTA endothermic peak 75degCwas also attributed to the dehydration of oligomer Al cations[20] and the value was 141 which was higher than that ofthe unmodified one (35) -e mass loss in the range of200ndash400degC (Loss 2) was contributed to the dehydration ofbentonite layers and the decomposition of hydroxyl groupsin polymeric FeAl cations-e secondmass loss of Fe-B andAl-B samples at 200ndash400degC was 112 and 99 re-spectively which was higher than that of the B sample(81) -e mass loss above 600degC (Loss 3) was due to thedecomposition of hydroxyl groups in the octahedron layer ofbentonite

-e nitrogen adsorption and desorption isotherms of BFe-B and Al-B materials are shown in Figure 4

-e nitrogen adsorptiondesorption isotherms of thesamples were all of type III according to IUPAC classifi-cation which indicated that the samples possessed meso-porous structure -e shape of hysteresis loops around from04 to 09 of relative pressure was attributed to the slit-shapedpores and their sizes are not well proportioned [4] Table 1lists the textural properties of all the samples -e BETsurface area of pure bentonite was 11444m2g but it in-creased to 14607m2g (Fe-B) and 17013m2g (Al-B) aftermodification -is is probably due to the increase of mi-cropore volume (0057 cm3g) and micropore surface area

4000 3500 3000 2500 2000 1500 1000 500

100

1394

11111630

1026

Al-B

B

Fe-B

T

(arb

)

Wave number (cmndash1)

Figure 2 FTIR spectra of B Fe-B and Al-B

0 10 20 30 40 50 60

d001 = 179 nm

d001 = 148 nm

Inte

nsity

(CPS

)

2θ (degrees)

B

Fe-B

Al-B

d001 = 144 nm

Figure 1 XRD patterns of B Fe-B and Al-B

Advances in Materials Science and Engineering 3

(11961m2g) in the interlayer spaces of the modified ben-tonite -is result was similar to the report of Ramesh et al[5] Before inserting polymeric Al into interlayer spaces ofbentonite these spaces were full of hydrated cations -earrangement of these cations created the spaces betweenthem favoring the absorption of nitrogen When inter-calating polymeric Al into the bentonite there were morepores in the interlayer space of bentonite favoring the ab-sorption of nitrogen so the micropore surface area of Al-Bsample increased According to the other authors [21 22]the cation charge in the spaces of bentonite strongly affectedthe absorption of nitrogen -e decrease of external areas of

0 200 400 600 800 100050

55

60

Temperature (degC)

Mas

s (m

g)

ndash50

ndash40

ndash30

ndash20

ndash10

0

DTA

TG

Endo

hea

t flo

w (micro

V) e

xo

(a)

0 200 400 600 800 1000

39

42

45

48

51

DTA

TG

Temperature (degC)

Mas

s (m

g)

ndash50

ndash40

ndash30

ndash20

ndash10

0

10

Endo

hea

t flo

w (micro

V) e

xo

(b)

Endo

hea

t flo

w (micro

V) e

xo0 200 400 600 800

12

14

16

Temperature (degC)

Mas

s (m

g)

ndash20

ndash15

ndash10

ndash5

0

5

10

TG

DTA

(c)

Figure 3 TG and DTA curves of B (a) Fe-B (b) and Al-B (c)

00 02 04 06 08 10

30

60

90

120

150

Relative pressure (PPdeg)

Vol

ume a

dsor

bed

(cm

3 middotgndash1

SPT

)

BFe-BAl-B

Figure 4 N2 adsorptiondesorption isotherms of B Fe-B and Al-B

Table 1 Textural parameters of B Fe-B and Al-B samples

Adsorbent SBET(m2g)

Smicro(m2g)

Sext(m2g)

Vmicro(cm3g)

Vtotal(cm3g)

B 11444 4472 6972 0020 0187Fe-B 14607 4103 10504 0018 0159Al-B 17013 11961 5052 0057 0111

4 Advances in Materials Science and Engineering

Al-B sample was explained by the increase of the number ofmicropores

32 Adsorption Studies

321 Effect of pH -e pH effect on the arsenate adsorptioncapacity of polymeric AlFe-modified bentonite is shown inFigure 5

It was found that the best adsorption of As(V) ontomodified bentonite was in the range of pH 20ndash40 Whenincreasing pH from 40 to 90 the amount of arsenateadsorbed (qe) decreased -e point of zero charge (pHPZC) ofFe-B and Al-B samples was respectively found to be 31 and48 (Figure 6) At pHlt pHPZC the modified bentonite surfacewas positively charged so it favored for the adsorption ofarsenic species in the form of H2AsO4

minus anions by electrostaticinteraction However at a pHgtpHPZC the modified surfacewas negatively charged causing a repulsion force between theAs(V) anions and bentonite surface In addition the hydroxylions and arsenate species could compete for adsorption athigh pH causing a reduction in As(V) adsorption Experi-mental results showed that As(V) had amaximum adsorptionat pH 30 for Fe-B sample and pH 40 for the Al-B sample-erefore pH 30 and pH 40 were selected for further ex-periments respectively for Fe-B and Al-B samples

In order to get more understanding of mechanism forarsenate absorption onto modified bentonite the As(V)absorption at different pH was carried out -e pH valuesbefore and after the absorption are shown in Table 2

From Table 2 it can be observed that the values of the pHfor all of cases in the adsorption experiment changed -epH values decreased after the arsenate absorption onto Fe-B-is could be explained by the reaction between the ab-sorption sites Fe-OH(surface) and H3AsO4(solution) creatingthe surface complexes such as the followingFe-OH(surface) + H3AsO4(solution) Fe-HAsO4

minus+ H(solution)

+

+ H2O(2)

-e liberation of H+ ions decreased pH of the solution-e pH increased after the As(V) absorption onto Al-B

sample due to the following reaction

(FeAl)minusOH(surface) + H2AsO4(solution)minus

(FeAl)minusH2AsO4(surface) + OH(solution)minus (3)

-e liberation of OHminus ions increased pH of the solutionSo in this pH range the main adsorption mechanisms

could be considered as the electrostatic interactions and ionexchange

FTIR spectra of Fe-B before and after the As(V) ab-sorption are depicted in Figure 7

Figure 7 shows a band in the range of 3500ndash3700 cmminus1related to the stretching vibration of the structural hydroxylsgroup (AlAlOH AlMgOH) [5] a strong band at 3563 cmminus1related to the O-H stretching vibration of the silanol (Si-OH)groups and HO-H vibration of the water adsorbed silicasurface [5] -e adsorption band at 1635 cmminus1 was due to the

deformation band (δ(O-H)) of physisorbed water [17] AfterAs(V) adsorption these peaks were also observed with de-creased intensity -is should be assigned to the direct in-teractions between arsenate anions and Fe-OH and Al-OHgroups at corners of bentonite layers to create Fe-O-As(V) orAl-O-As(V) bonds which decreased intensity of these peaksIn addition a new peak with low intensity was observed at879 cmminus1 corresponding to As-O vibration inHAsO4

2minus anionindicating that there was the As(V) adsorption onto Fe-B

-e SEM images of Fe-B Fe-B after the As(V) ad-sorption Al-B and Al-B after the As(V) adsorption areshown in Figure 8

-e morphology of modified bentonite changed clearlyby the As(V) adsorption -e morphology of Fe-B includedplates with diameter of several μm around of which particlesof small sizes were located -is morphology might facilitatefor As(V) to adsorb onto modified bentonite After As(V)adsorption the lamellar structure of the Fe-B was left and alarge number of flakes appeared -is indicated that therewas a change in distance between the clay particles afterarsenate adsorption In addition the small-size particlesaround the clay plates disappeared suggesting that smallclusters of Fe(III) oxides and hydroxides were also ad-sorption sites on surfaces -e morphology of Al-B sampleconsisted of the aggregate of smectites with irregular shapeand partly a mass of flake shape After arsenate adsorptionthe modified clay surface was changed to an aggregatedmorphology and there were several clusters around the clayplates -is indicated that the As(V) adsorption had a stronginfluence on the structure and morphology of modifiedbentonites

322 Adsorption Kinetics Experimental kinetic data wereevaluated by using pseudo-first-order and pseudo-second-order kinetic models -e pseudo-first-order kinetic modelin linear form is presented in the following equation

1 2 3 4 5 6 7 8 9 10

8

10

12

14

16

18

q e (m

gmiddotgndash1

)

pH

Fe-BAl-B

Figure 5 Effect of pH on the adsorption capacity of As(V) ontoFe-B sample (Co(As) 1298mgL) and Al-B sample (Co(As)

1684mgL) (T 303K m 005 g t 4 h)

Advances in Materials Science and Engineering 5

ln qe minus qt( 1113857 ln qe minus k1 middot t (4)

where qe and qt are the adsorption capacity at equilibriumand at time t (mgg) and k1 is the pseudo-first-order rateconstant (minminus1)

-e pseudo-second-order kinetic model is given by[23 24]

t

qt

1

k2q2e

+1qe

middot t (5)

where k2 is the equilibrium rate constant of pseudo-second-order kinetic model (gmolmiddotmin)

-e goodness of fit for the compatible model is assessedbased on determination coefficient R2 for the regressionequation

-e plots of pseudo-first-order and pseudo-second-orderkinetic models are illustrated in Figures 9 and 10 respectively-eir parameters are summarized in Table 3 -e high de-termination coefficients (gt092) as well as the calculated qevalues close to the experimental ones indicated that pseudo-second-order kinetic model was more suitable for the de-scription of the adsorption kinetics of arsenate on modifiedbentonite (Table 3) -is implied that the adsorption processcould be chemisorption [23 24] -e values of qe at differenttemperatures for Al-B were greater than those for Fe-B in-dicating that the adsorption capacity of Al-B is larger than thatof Fe-B -e average diameter of H2AsO4

minus ions was about35 A meanwhile the pore diameter of studied materials wasabout 26ndash220 A so arsenate ions were easy to move inside themesopores of materials without being obstructed the geometry

Table 3 shows that the value of k2 increased with in-creasing temperature for both two samples (Fe-B 035310minus3ndash730110minus3 gmgmiddotmin Al-B 2810minus3ndash5810minus3 gmgmiddotmin)

-e activation energy can be computed by using theArrhenius equation

ln k2 minusEa

RT+ lnA (6)

where A is the Arrhenius constant (gmgmiddotmin) Ea the ac-tivation energy of adsorption (kJmol) R is the gas constant(8314 JmolmiddotK) and T is the absolute temperature (K) -eactivation energy (Ea) was obtained from the slope of thelinear plot of ln k2 versus 1T (Figure 11(a))

Besides calculating the activation energy the Gibbsenergy ΔG enthalpy ΔH and entropy ΔS of the activation

Table 2 pH of As(V) solution before and after the arsenate ab-sorption onto Fe-B (Co(As) 1298mgL) and Al-B (Co(As)

1684mgL) (T 303K m 005 g)

pH before the arsenateabsorption 20 30 40 50 60 70 80 90

pH after the arsenateabsorption onto Fe-B 20 29 33 mdash 40 48 70 72

pH after the arsenateabsorption onto Al-B 27 37 54 58 64 79 81 94

4500 4000 3500 3000 2500 2000 1500 1000 500

100

879

13841631

Fe-B-Abs

Fe-B

Wave number (cmndash1)

T

(Arb

)

Figure 7 FT-IR spectra of Fe-B before and after the As(V)adsorption

4 6 8 10

ndash6

ndash4

ndash2

0

NaCl 01 MNaCl 001 M

pH

∆pH

(a)

NaCl 01 MNaCl 001 M

4 6 8 10pH

ndash3

ndash2

ndash1

0

1

ΔpH

(b)

Figure 6 Point of zero charge plots of Fe-B (a) and Al-B (b)

6 Advances in Materials Science and Engineering

for As(V) adsorption kinetics can be computed by using theEyring equation [25]

lnk2

T ln

kb

h1113888 1113889minus

ΔG

R middot T minusΔH

Rmiddot1T

+ lnkb

h1113888 1113889 +

ΔS

R1113890 1113891

(7)

where kb (13807times10minus23 JK) is the Boltzmann constant h(6621times 10minus34 Jmiddots) is the Planck constant ΔG is the Gibbs

energy of activation ΔH is the activation enthalpy and ΔSis the activation entropy

-e linear plot of ln(kT) versus 1Tgives a straight line-e activation parameters could be derived from the slopeand intercepts of these lines (Figure 11(b))

-e values of the activation energy were found to be8029 kJmol and 4190 kJmol for the arsenate adsorptiononto Fe-B and Al-B respectively (Table 4)-emagnitude ofactivation energy can give information on whether the

(a) (b)

(c) (d)

Figure 8 SEM images of Fe-B (a) Fe-B after the As(V) adsorption (b) Al-B (c) and Al-B after the As(V) adsorption (d)

0 40 80 120 160 200

ndash2

ndash1

0

1

2

3

ln (q

e ndash qt)

Time (min)

283 K293 K

303 K313 K

(a)

283 K293 K

303 K313 K

0 100 200

0

5

10

15

tqt (

min

middotgmiddotm

gndash1)

Time (min)

(b)

Figure 9 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Fe-B at differenttemperatures

Advances in Materials Science and Engineering 7

283 K293 K

303 K313 K

ndash05

00

05

10

15

20

25ln

(qe ndash

qt)

Time (min)0 30 60 90 120 150 180

(a)

283 K293 K

303 K313 K

0

3

6

9

12

tqt (

min

middotgmiddotm

gndash1)

Time (min)0 50 100 150 200 250

(b)

Figure 10 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Al-B at differenttemperatures

Table 3 Parameters of pseudo-first-order and pseudo-second-order kinetic model of As(V) adsorption by Fe-B and Al-B at differenttemperatures

Adsorbent T (K) qe (experimental) (mgg)First-order kinetic model Second-order kinetic model

k1 (minminus1) qe (cal) (mgg) R2 k2 (gmgmiddotmin) qe (cal) (mgg) R2

Fe-B

283 1438 0010 1519 0942 035times10minus3 2114 0924293 1442 0013 1244 0977 068times10minus3 1980 0973303 1442 0027 980 0962 420times10minus3 1553 0999313 1444 0021 657 0992 730times10minus3 1497 0998

Al-B

283 1847 16times10minus3 1635 0956 10times10minus3 2222 0984293 2075 19times10minus3 1301 0948 29times10minus3 2222 0998303 2080 70times10minus3 856 0949 42times10minus3 2083 0992313 2105 90times10minus3 709 0752 58times10minus3 2128 0996

ndash8

ndash7

ndash6

ndash5

ln k 2

1T (Kndash1)

FendashB R2 = 0952AlndashB R2 = 0924

00032 00033 00034 00035

(a)

FendashB R2 = 0946AlndashB R2 = 0912

ndash14

ndash13

ndash12

ndash11

ndash10

1T (Kndash1)

ln (k

2T)

00032 00033 00034 00035

(b)

Figure 11 (a) Arrhenius plots and (b) Eyring plots of As(V) adsorption onto Fe-B and Al-B

8 Advances in Materials Science and Engineering

adsorption process is physical or chemical Ramesh et al [5]reported that the activation energy of physisorption wasnormally not more than 42 kJmol Hence the values ofactivation energy were found in this study suggesting thatthe adsorption of As(V) on Fe-B was a chemical adsorption-e smaller Ea for the adsorption of As(V) on Al-B was dueto the formation of weak chemical bond between absorbentand adsorbate According to the literature the rate constantincreased when decreasing the value of activation energy orincreasing the frequency factor A -e calculated A valueswere found to be 18times10minus11 and 80821 for the adsorption ofAs(V) on Fe-B and on Al-B respectively -ese results wereinteresting due to showing ldquothe compensation effectrdquo inheterogeneous adsorption

-e free energy of activation (ΔG) activation enthalpy(ΔH) and activation entropy (ΔS) are listed in Table 4-epositive value of ΔH for both samples confirmed an en-dothermic process -e magnitude and sign of ∆S can givean indication of whether the adsorption reaction is an as-sociative or dissociative mechanism [25] -e high negativevalues of ΔS manifested that the As(V) adsorption processwas an associative mechanism -is was additional evidencefor the analysis of adsorption mechanism as described inSection 321 -e large positive values of ΔG inferred thatthe adsorption reactions required energy to convert thereactants into products [26]

323 Adsorption Isotherms Equilibrium studies were car-ried out to obtain the adsorption capacity of modifiedbentonite at different temperatures Two adsorption iso-therms namely the Langmuir [23] and the Freundlich [23]isotherms were employed to analyze the adsorption data-e linear form of Langmuir isotherm is given by

Ce

qe

Ce

qm+

1KL middot qm

(8)

where qe is the equilibrium adsorption capacity (mgg) Ce isthe equilibrium arsenate concentration in solution (mgL)qm is the monolayer adsorption capacity of the adsorbent(mgg) and KL is the Langmuir constant (Lmg) which isrelated to the energy of adsorption respectively qm and KLcan be computed from the intercept and slope of the linearplot with Ceqe versus Ce

In addition a separation factor RL (also equilibriumparameter) is defined by the following equation

RL 1

1 + KLCi (9)

where Ci (mgL) is the initial dye concentration and KL(Lmg) is the Langmuir constant -e value of RL indicatesthe shape of the isotherms to be either unfavorable (RLgt 1)linear (RL 1) favorable (0ltRLlt 1) or irreversible (RL 0)

-e Freundlich isotherm was applied to the adsorptionon a heterogeneous surface with uniform energy -e linearform of this model can be expressed as follows

ln qe lnKF +1n

middot lnCe (10)

where qe and Ce are the equilibrium adsorption capacity(mgg) and equilibrium concentration in liquid phases (mgL) respectively KF and n are the Freundlich constants whichare related to adsorption capacity and intensity respectively-e linear plot with ln qe versus ln Ce can provide the valuesof KF and n from the slope and intercepts

-e plots for he Langmuir and Freundlich isothermmodels are shown in Figures 12 and 13

As seen from Table 5 the high values of R2 for theLangmuir isotherm model (R2gt 0920) as compared withthose for the Freundlich isotherm model (R2lt 0875) and thevalues of RL in the range 0 and 1 inferred that As(V) ad-sorption onto the modified bentonite was favorable for theLangmuir model Based on the maximum monolayer ad-sorption capacity of the adsorbent qm (mgg) specific area ofmodified bentonite can computed by the following expression

S qAsmaxMAs

middot NA middot σAs (11)

where qAsmax is the Langmuir monolayer adsorption capacityMAs is the molar masse of As NA is Avogadro number andσAs is the surface area of AsO4

3minus (σAs π middot r2 r 17 A)Specific surface area of modified bentonite was calcu-

lated at the temperature of 283K as follows

S(FeminusB) 177675

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

1296m2g

S(AlminusB) 294175

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

2146m2g

(12)

-e effective surface area values of the studied sampleswere less than SBET of Fe-B (14607m2g) and Al-B(17013m2g) indicating that the As(V) absorption ontostudied materials only occurred at the outer surfaces and inthe large pores of bentonite particles

-e maximum As(V) adsorption capacities (qm)computed from the Langmuir model at 303 K were1898mgg for Fe-B and 3571mgg for Al-B As can be seenfrom Table 6 the adsorption capacity for arsenate

Table 4 Activation energy and activation parameters of adsorptionprocess

T (K) Ea (kJmol) ∆H (kJmol) ΔS (kJmolK) ΔG (kJmol)Fe-B283 8029 7782 minus0037 8841293 8879303 8916313 8953Al-B

4190 3932 minus0162 8516867888409002

Advances in Materials Science and Engineering 9

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

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Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

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Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

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Hindawiwwwhindawicom Volume 2018

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Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

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Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

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BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

bentonite layers According to Hao et al [13] the size ofhydroxyaluminum polycation ([AlO4Al12(OH)24(OH2)12]7+)was of about 09 nm and the basal spacing (d001) of bentonitewas 096 nm so if there was an intercalation of ion KegginAl13 into the interlayer space of bentonite the basal spacing(d001) of bentonite would be about of 186 nm Other authors[14 15] have observed that Al13 pillared bentonite gave basalspacings between 17 and 18 A-is was explained byQin et al[11] that the value of d001 could not attain 186 nm probablydue to the delamination of bentonite

-e FTIR spectra of the samples are depicted in Figure 2-e peak at 3549 cmminus1 of B sample was assigned to Al-

Fe-OH vibration [16] the peak at 3414 cmminus1 contributed toFe-Fe-OH vibration [16] and HO-H vibration of theadsorbed water and the peak at 1638 cmminus1 was due to thedeformation band (δ(O-H)) of physically adsorbed water-e peak at 1111 cmminus1 was assigned to Si-O vibration intetrahedral If the amount of iron (Fe) in clays was high thispeak would shift to the higher position According to otherreports [1 11 17] this peak was in the range of1033ndash1041 cmminus1 indicating that bentonite was iron-richclay -e peak at 964 cmminus1 was corresponded to Si-OHvibration [18] the peak at 816 cmminus1 was because of thedeformation vibration of Fe-Fe-OH [16] and the peak at675 cmminus1 was attributed to Al-Fe-OH vibration [19]

FT-IR spectra of the Fe-B and Al-B show that somecharacteristic bands of the initial bentonite were changedPeak related to the δ(O-H) deformation shifted from1638 cmminus1 (B) to 1630 cmminus1 (Fe-B) and to 1636 cmminus1 (Al-B)with lower intensity -is could be due to the decrease of theH2O content with replacing of the intercalated FeAl pol-ycations For Al-B the peak at 3441 cmminus1 and the intensitywas higher than that of B (3414 cmminus1) -e former wascontributed to the O-H stretching vibration in hydroxyl-Alcations while the latter was corresponded to the hydroxylgroups in water-water hydrogen bands [17] -e band of Si-O vibration shifted from 1111 to 1026 cmminus1 attributing to thestrong interactions of the hydroxyl Al and bentonite layers-e FTIR results were in accordance with those of XRD

TG and DTA curves of B Fe-B and Al-B samples arepresented in Figure 3

TG and DTA curves of B Fe-B and Al-B samples arepresented in Figure 3 -ere were three main mass losses inthe TG curve for the sample without modification -e firstone below 200degC was due to physical water adsorption -esecond mass loss being broadened from 200 to 600degC couldbe assigned to the interlayer water in bentonite structure-e third mass loss in the range of the temperatures over600degC corresponding to the DTA peak 778degC was contrib-uted to the dehydroxylation of bentonite layers -e TGcurves of Fe-B and Al-B samples were similar than that of Bsample -e mass loss in the range of 20ndash200degC (Loss 1) wasassigned to physically adsorbed water -is period of the Al-B sample corresponding to the DTA endothermic peak 75degCwas also attributed to the dehydration of oligomer Al cations[20] and the value was 141 which was higher than that ofthe unmodified one (35) -e mass loss in the range of200ndash400degC (Loss 2) was contributed to the dehydration ofbentonite layers and the decomposition of hydroxyl groupsin polymeric FeAl cations-e secondmass loss of Fe-B andAl-B samples at 200ndash400degC was 112 and 99 re-spectively which was higher than that of the B sample(81) -e mass loss above 600degC (Loss 3) was due to thedecomposition of hydroxyl groups in the octahedron layer ofbentonite

-e nitrogen adsorption and desorption isotherms of BFe-B and Al-B materials are shown in Figure 4

-e nitrogen adsorptiondesorption isotherms of thesamples were all of type III according to IUPAC classifi-cation which indicated that the samples possessed meso-porous structure -e shape of hysteresis loops around from04 to 09 of relative pressure was attributed to the slit-shapedpores and their sizes are not well proportioned [4] Table 1lists the textural properties of all the samples -e BETsurface area of pure bentonite was 11444m2g but it in-creased to 14607m2g (Fe-B) and 17013m2g (Al-B) aftermodification -is is probably due to the increase of mi-cropore volume (0057 cm3g) and micropore surface area

4000 3500 3000 2500 2000 1500 1000 500

100

1394

11111630

1026

Al-B

B

Fe-B

T

(arb

)

Wave number (cmndash1)

Figure 2 FTIR spectra of B Fe-B and Al-B

0 10 20 30 40 50 60

d001 = 179 nm

d001 = 148 nm

Inte

nsity

(CPS

)

2θ (degrees)

B

Fe-B

Al-B

d001 = 144 nm

Figure 1 XRD patterns of B Fe-B and Al-B

Advances in Materials Science and Engineering 3

(11961m2g) in the interlayer spaces of the modified ben-tonite -is result was similar to the report of Ramesh et al[5] Before inserting polymeric Al into interlayer spaces ofbentonite these spaces were full of hydrated cations -earrangement of these cations created the spaces betweenthem favoring the absorption of nitrogen When inter-calating polymeric Al into the bentonite there were morepores in the interlayer space of bentonite favoring the ab-sorption of nitrogen so the micropore surface area of Al-Bsample increased According to the other authors [21 22]the cation charge in the spaces of bentonite strongly affectedthe absorption of nitrogen -e decrease of external areas of

0 200 400 600 800 100050

55

60

Temperature (degC)

Mas

s (m

g)

ndash50

ndash40

ndash30

ndash20

ndash10

0

DTA

TG

Endo

hea

t flo

w (micro

V) e

xo

(a)

0 200 400 600 800 1000

39

42

45

48

51

DTA

TG

Temperature (degC)

Mas

s (m

g)

ndash50

ndash40

ndash30

ndash20

ndash10

0

10

Endo

hea

t flo

w (micro

V) e

xo

(b)

Endo

hea

t flo

w (micro

V) e

xo0 200 400 600 800

12

14

16

Temperature (degC)

Mas

s (m

g)

ndash20

ndash15

ndash10

ndash5

0

5

10

TG

DTA

(c)

Figure 3 TG and DTA curves of B (a) Fe-B (b) and Al-B (c)

00 02 04 06 08 10

30

60

90

120

150

Relative pressure (PPdeg)

Vol

ume a

dsor

bed

(cm

3 middotgndash1

SPT

)

BFe-BAl-B

Figure 4 N2 adsorptiondesorption isotherms of B Fe-B and Al-B

Table 1 Textural parameters of B Fe-B and Al-B samples

Adsorbent SBET(m2g)

Smicro(m2g)

Sext(m2g)

Vmicro(cm3g)

Vtotal(cm3g)

B 11444 4472 6972 0020 0187Fe-B 14607 4103 10504 0018 0159Al-B 17013 11961 5052 0057 0111

4 Advances in Materials Science and Engineering

Al-B sample was explained by the increase of the number ofmicropores

32 Adsorption Studies

321 Effect of pH -e pH effect on the arsenate adsorptioncapacity of polymeric AlFe-modified bentonite is shown inFigure 5

It was found that the best adsorption of As(V) ontomodified bentonite was in the range of pH 20ndash40 Whenincreasing pH from 40 to 90 the amount of arsenateadsorbed (qe) decreased -e point of zero charge (pHPZC) ofFe-B and Al-B samples was respectively found to be 31 and48 (Figure 6) At pHlt pHPZC the modified bentonite surfacewas positively charged so it favored for the adsorption ofarsenic species in the form of H2AsO4

minus anions by electrostaticinteraction However at a pHgtpHPZC the modified surfacewas negatively charged causing a repulsion force between theAs(V) anions and bentonite surface In addition the hydroxylions and arsenate species could compete for adsorption athigh pH causing a reduction in As(V) adsorption Experi-mental results showed that As(V) had amaximum adsorptionat pH 30 for Fe-B sample and pH 40 for the Al-B sample-erefore pH 30 and pH 40 were selected for further ex-periments respectively for Fe-B and Al-B samples

In order to get more understanding of mechanism forarsenate absorption onto modified bentonite the As(V)absorption at different pH was carried out -e pH valuesbefore and after the absorption are shown in Table 2

From Table 2 it can be observed that the values of the pHfor all of cases in the adsorption experiment changed -epH values decreased after the arsenate absorption onto Fe-B-is could be explained by the reaction between the ab-sorption sites Fe-OH(surface) and H3AsO4(solution) creatingthe surface complexes such as the followingFe-OH(surface) + H3AsO4(solution) Fe-HAsO4

minus+ H(solution)

+

+ H2O(2)

-e liberation of H+ ions decreased pH of the solution-e pH increased after the As(V) absorption onto Al-B

sample due to the following reaction

(FeAl)minusOH(surface) + H2AsO4(solution)minus

(FeAl)minusH2AsO4(surface) + OH(solution)minus (3)

-e liberation of OHminus ions increased pH of the solutionSo in this pH range the main adsorption mechanisms

could be considered as the electrostatic interactions and ionexchange

FTIR spectra of Fe-B before and after the As(V) ab-sorption are depicted in Figure 7

Figure 7 shows a band in the range of 3500ndash3700 cmminus1related to the stretching vibration of the structural hydroxylsgroup (AlAlOH AlMgOH) [5] a strong band at 3563 cmminus1related to the O-H stretching vibration of the silanol (Si-OH)groups and HO-H vibration of the water adsorbed silicasurface [5] -e adsorption band at 1635 cmminus1 was due to the

deformation band (δ(O-H)) of physisorbed water [17] AfterAs(V) adsorption these peaks were also observed with de-creased intensity -is should be assigned to the direct in-teractions between arsenate anions and Fe-OH and Al-OHgroups at corners of bentonite layers to create Fe-O-As(V) orAl-O-As(V) bonds which decreased intensity of these peaksIn addition a new peak with low intensity was observed at879 cmminus1 corresponding to As-O vibration inHAsO4

2minus anionindicating that there was the As(V) adsorption onto Fe-B

-e SEM images of Fe-B Fe-B after the As(V) ad-sorption Al-B and Al-B after the As(V) adsorption areshown in Figure 8

-e morphology of modified bentonite changed clearlyby the As(V) adsorption -e morphology of Fe-B includedplates with diameter of several μm around of which particlesof small sizes were located -is morphology might facilitatefor As(V) to adsorb onto modified bentonite After As(V)adsorption the lamellar structure of the Fe-B was left and alarge number of flakes appeared -is indicated that therewas a change in distance between the clay particles afterarsenate adsorption In addition the small-size particlesaround the clay plates disappeared suggesting that smallclusters of Fe(III) oxides and hydroxides were also ad-sorption sites on surfaces -e morphology of Al-B sampleconsisted of the aggregate of smectites with irregular shapeand partly a mass of flake shape After arsenate adsorptionthe modified clay surface was changed to an aggregatedmorphology and there were several clusters around the clayplates -is indicated that the As(V) adsorption had a stronginfluence on the structure and morphology of modifiedbentonites

322 Adsorption Kinetics Experimental kinetic data wereevaluated by using pseudo-first-order and pseudo-second-order kinetic models -e pseudo-first-order kinetic modelin linear form is presented in the following equation

1 2 3 4 5 6 7 8 9 10

8

10

12

14

16

18

q e (m

gmiddotgndash1

)

pH

Fe-BAl-B

Figure 5 Effect of pH on the adsorption capacity of As(V) ontoFe-B sample (Co(As) 1298mgL) and Al-B sample (Co(As)

1684mgL) (T 303K m 005 g t 4 h)

Advances in Materials Science and Engineering 5

ln qe minus qt( 1113857 ln qe minus k1 middot t (4)

where qe and qt are the adsorption capacity at equilibriumand at time t (mgg) and k1 is the pseudo-first-order rateconstant (minminus1)

-e pseudo-second-order kinetic model is given by[23 24]

t

qt

1

k2q2e

+1qe

middot t (5)

where k2 is the equilibrium rate constant of pseudo-second-order kinetic model (gmolmiddotmin)

-e goodness of fit for the compatible model is assessedbased on determination coefficient R2 for the regressionequation

-e plots of pseudo-first-order and pseudo-second-orderkinetic models are illustrated in Figures 9 and 10 respectively-eir parameters are summarized in Table 3 -e high de-termination coefficients (gt092) as well as the calculated qevalues close to the experimental ones indicated that pseudo-second-order kinetic model was more suitable for the de-scription of the adsorption kinetics of arsenate on modifiedbentonite (Table 3) -is implied that the adsorption processcould be chemisorption [23 24] -e values of qe at differenttemperatures for Al-B were greater than those for Fe-B in-dicating that the adsorption capacity of Al-B is larger than thatof Fe-B -e average diameter of H2AsO4

minus ions was about35 A meanwhile the pore diameter of studied materials wasabout 26ndash220 A so arsenate ions were easy to move inside themesopores of materials without being obstructed the geometry

Table 3 shows that the value of k2 increased with in-creasing temperature for both two samples (Fe-B 035310minus3ndash730110minus3 gmgmiddotmin Al-B 2810minus3ndash5810minus3 gmgmiddotmin)

-e activation energy can be computed by using theArrhenius equation

ln k2 minusEa

RT+ lnA (6)

where A is the Arrhenius constant (gmgmiddotmin) Ea the ac-tivation energy of adsorption (kJmol) R is the gas constant(8314 JmolmiddotK) and T is the absolute temperature (K) -eactivation energy (Ea) was obtained from the slope of thelinear plot of ln k2 versus 1T (Figure 11(a))

Besides calculating the activation energy the Gibbsenergy ΔG enthalpy ΔH and entropy ΔS of the activation

Table 2 pH of As(V) solution before and after the arsenate ab-sorption onto Fe-B (Co(As) 1298mgL) and Al-B (Co(As)

1684mgL) (T 303K m 005 g)

pH before the arsenateabsorption 20 30 40 50 60 70 80 90

pH after the arsenateabsorption onto Fe-B 20 29 33 mdash 40 48 70 72

pH after the arsenateabsorption onto Al-B 27 37 54 58 64 79 81 94

4500 4000 3500 3000 2500 2000 1500 1000 500

100

879

13841631

Fe-B-Abs

Fe-B

Wave number (cmndash1)

T

(Arb

)

Figure 7 FT-IR spectra of Fe-B before and after the As(V)adsorption

4 6 8 10

ndash6

ndash4

ndash2

0

NaCl 01 MNaCl 001 M

pH

∆pH

(a)

NaCl 01 MNaCl 001 M

4 6 8 10pH

ndash3

ndash2

ndash1

0

1

ΔpH

(b)

Figure 6 Point of zero charge plots of Fe-B (a) and Al-B (b)

6 Advances in Materials Science and Engineering

for As(V) adsorption kinetics can be computed by using theEyring equation [25]

lnk2

T ln

kb

h1113888 1113889minus

ΔG

R middot T minusΔH

Rmiddot1T

+ lnkb

h1113888 1113889 +

ΔS

R1113890 1113891

(7)

where kb (13807times10minus23 JK) is the Boltzmann constant h(6621times 10minus34 Jmiddots) is the Planck constant ΔG is the Gibbs

energy of activation ΔH is the activation enthalpy and ΔSis the activation entropy

-e linear plot of ln(kT) versus 1Tgives a straight line-e activation parameters could be derived from the slopeand intercepts of these lines (Figure 11(b))

-e values of the activation energy were found to be8029 kJmol and 4190 kJmol for the arsenate adsorptiononto Fe-B and Al-B respectively (Table 4)-emagnitude ofactivation energy can give information on whether the

(a) (b)

(c) (d)

Figure 8 SEM images of Fe-B (a) Fe-B after the As(V) adsorption (b) Al-B (c) and Al-B after the As(V) adsorption (d)

0 40 80 120 160 200

ndash2

ndash1

0

1

2

3

ln (q

e ndash qt)

Time (min)

283 K293 K

303 K313 K

(a)

283 K293 K

303 K313 K

0 100 200

0

5

10

15

tqt (

min

middotgmiddotm

gndash1)

Time (min)

(b)

Figure 9 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Fe-B at differenttemperatures

Advances in Materials Science and Engineering 7

283 K293 K

303 K313 K

ndash05

00

05

10

15

20

25ln

(qe ndash

qt)

Time (min)0 30 60 90 120 150 180

(a)

283 K293 K

303 K313 K

0

3

6

9

12

tqt (

min

middotgmiddotm

gndash1)

Time (min)0 50 100 150 200 250

(b)

Figure 10 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Al-B at differenttemperatures

Table 3 Parameters of pseudo-first-order and pseudo-second-order kinetic model of As(V) adsorption by Fe-B and Al-B at differenttemperatures

Adsorbent T (K) qe (experimental) (mgg)First-order kinetic model Second-order kinetic model

k1 (minminus1) qe (cal) (mgg) R2 k2 (gmgmiddotmin) qe (cal) (mgg) R2

Fe-B

283 1438 0010 1519 0942 035times10minus3 2114 0924293 1442 0013 1244 0977 068times10minus3 1980 0973303 1442 0027 980 0962 420times10minus3 1553 0999313 1444 0021 657 0992 730times10minus3 1497 0998

Al-B

283 1847 16times10minus3 1635 0956 10times10minus3 2222 0984293 2075 19times10minus3 1301 0948 29times10minus3 2222 0998303 2080 70times10minus3 856 0949 42times10minus3 2083 0992313 2105 90times10minus3 709 0752 58times10minus3 2128 0996

ndash8

ndash7

ndash6

ndash5

ln k 2

1T (Kndash1)

FendashB R2 = 0952AlndashB R2 = 0924

00032 00033 00034 00035

(a)

FendashB R2 = 0946AlndashB R2 = 0912

ndash14

ndash13

ndash12

ndash11

ndash10

1T (Kndash1)

ln (k

2T)

00032 00033 00034 00035

(b)

Figure 11 (a) Arrhenius plots and (b) Eyring plots of As(V) adsorption onto Fe-B and Al-B

8 Advances in Materials Science and Engineering

adsorption process is physical or chemical Ramesh et al [5]reported that the activation energy of physisorption wasnormally not more than 42 kJmol Hence the values ofactivation energy were found in this study suggesting thatthe adsorption of As(V) on Fe-B was a chemical adsorption-e smaller Ea for the adsorption of As(V) on Al-B was dueto the formation of weak chemical bond between absorbentand adsorbate According to the literature the rate constantincreased when decreasing the value of activation energy orincreasing the frequency factor A -e calculated A valueswere found to be 18times10minus11 and 80821 for the adsorption ofAs(V) on Fe-B and on Al-B respectively -ese results wereinteresting due to showing ldquothe compensation effectrdquo inheterogeneous adsorption

-e free energy of activation (ΔG) activation enthalpy(ΔH) and activation entropy (ΔS) are listed in Table 4-epositive value of ΔH for both samples confirmed an en-dothermic process -e magnitude and sign of ∆S can givean indication of whether the adsorption reaction is an as-sociative or dissociative mechanism [25] -e high negativevalues of ΔS manifested that the As(V) adsorption processwas an associative mechanism -is was additional evidencefor the analysis of adsorption mechanism as described inSection 321 -e large positive values of ΔG inferred thatthe adsorption reactions required energy to convert thereactants into products [26]

323 Adsorption Isotherms Equilibrium studies were car-ried out to obtain the adsorption capacity of modifiedbentonite at different temperatures Two adsorption iso-therms namely the Langmuir [23] and the Freundlich [23]isotherms were employed to analyze the adsorption data-e linear form of Langmuir isotherm is given by

Ce

qe

Ce

qm+

1KL middot qm

(8)

where qe is the equilibrium adsorption capacity (mgg) Ce isthe equilibrium arsenate concentration in solution (mgL)qm is the monolayer adsorption capacity of the adsorbent(mgg) and KL is the Langmuir constant (Lmg) which isrelated to the energy of adsorption respectively qm and KLcan be computed from the intercept and slope of the linearplot with Ceqe versus Ce

In addition a separation factor RL (also equilibriumparameter) is defined by the following equation

RL 1

1 + KLCi (9)

where Ci (mgL) is the initial dye concentration and KL(Lmg) is the Langmuir constant -e value of RL indicatesthe shape of the isotherms to be either unfavorable (RLgt 1)linear (RL 1) favorable (0ltRLlt 1) or irreversible (RL 0)

-e Freundlich isotherm was applied to the adsorptionon a heterogeneous surface with uniform energy -e linearform of this model can be expressed as follows

ln qe lnKF +1n

middot lnCe (10)

where qe and Ce are the equilibrium adsorption capacity(mgg) and equilibrium concentration in liquid phases (mgL) respectively KF and n are the Freundlich constants whichare related to adsorption capacity and intensity respectively-e linear plot with ln qe versus ln Ce can provide the valuesof KF and n from the slope and intercepts

-e plots for he Langmuir and Freundlich isothermmodels are shown in Figures 12 and 13

As seen from Table 5 the high values of R2 for theLangmuir isotherm model (R2gt 0920) as compared withthose for the Freundlich isotherm model (R2lt 0875) and thevalues of RL in the range 0 and 1 inferred that As(V) ad-sorption onto the modified bentonite was favorable for theLangmuir model Based on the maximum monolayer ad-sorption capacity of the adsorbent qm (mgg) specific area ofmodified bentonite can computed by the following expression

S qAsmaxMAs

middot NA middot σAs (11)

where qAsmax is the Langmuir monolayer adsorption capacityMAs is the molar masse of As NA is Avogadro number andσAs is the surface area of AsO4

3minus (σAs π middot r2 r 17 A)Specific surface area of modified bentonite was calcu-

lated at the temperature of 283K as follows

S(FeminusB) 177675

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

1296m2g

S(AlminusB) 294175

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

2146m2g

(12)

-e effective surface area values of the studied sampleswere less than SBET of Fe-B (14607m2g) and Al-B(17013m2g) indicating that the As(V) absorption ontostudied materials only occurred at the outer surfaces and inthe large pores of bentonite particles

-e maximum As(V) adsorption capacities (qm)computed from the Langmuir model at 303 K were1898mgg for Fe-B and 3571mgg for Al-B As can be seenfrom Table 6 the adsorption capacity for arsenate

Table 4 Activation energy and activation parameters of adsorptionprocess

T (K) Ea (kJmol) ∆H (kJmol) ΔS (kJmolK) ΔG (kJmol)Fe-B283 8029 7782 minus0037 8841293 8879303 8916313 8953Al-B

4190 3932 minus0162 8516867888409002

Advances in Materials Science and Engineering 9

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

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ria

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Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

(11961m2g) in the interlayer spaces of the modified ben-tonite -is result was similar to the report of Ramesh et al[5] Before inserting polymeric Al into interlayer spaces ofbentonite these spaces were full of hydrated cations -earrangement of these cations created the spaces betweenthem favoring the absorption of nitrogen When inter-calating polymeric Al into the bentonite there were morepores in the interlayer space of bentonite favoring the ab-sorption of nitrogen so the micropore surface area of Al-Bsample increased According to the other authors [21 22]the cation charge in the spaces of bentonite strongly affectedthe absorption of nitrogen -e decrease of external areas of

0 200 400 600 800 100050

55

60

Temperature (degC)

Mas

s (m

g)

ndash50

ndash40

ndash30

ndash20

ndash10

0

DTA

TG

Endo

hea

t flo

w (micro

V) e

xo

(a)

0 200 400 600 800 1000

39

42

45

48

51

DTA

TG

Temperature (degC)

Mas

s (m

g)

ndash50

ndash40

ndash30

ndash20

ndash10

0

10

Endo

hea

t flo

w (micro

V) e

xo

(b)

Endo

hea

t flo

w (micro

V) e

xo0 200 400 600 800

12

14

16

Temperature (degC)

Mas

s (m

g)

ndash20

ndash15

ndash10

ndash5

0

5

10

TG

DTA

(c)

Figure 3 TG and DTA curves of B (a) Fe-B (b) and Al-B (c)

00 02 04 06 08 10

30

60

90

120

150

Relative pressure (PPdeg)

Vol

ume a

dsor

bed

(cm

3 middotgndash1

SPT

)

BFe-BAl-B

Figure 4 N2 adsorptiondesorption isotherms of B Fe-B and Al-B

Table 1 Textural parameters of B Fe-B and Al-B samples

Adsorbent SBET(m2g)

Smicro(m2g)

Sext(m2g)

Vmicro(cm3g)

Vtotal(cm3g)

B 11444 4472 6972 0020 0187Fe-B 14607 4103 10504 0018 0159Al-B 17013 11961 5052 0057 0111

4 Advances in Materials Science and Engineering

Al-B sample was explained by the increase of the number ofmicropores

32 Adsorption Studies

321 Effect of pH -e pH effect on the arsenate adsorptioncapacity of polymeric AlFe-modified bentonite is shown inFigure 5

It was found that the best adsorption of As(V) ontomodified bentonite was in the range of pH 20ndash40 Whenincreasing pH from 40 to 90 the amount of arsenateadsorbed (qe) decreased -e point of zero charge (pHPZC) ofFe-B and Al-B samples was respectively found to be 31 and48 (Figure 6) At pHlt pHPZC the modified bentonite surfacewas positively charged so it favored for the adsorption ofarsenic species in the form of H2AsO4

minus anions by electrostaticinteraction However at a pHgtpHPZC the modified surfacewas negatively charged causing a repulsion force between theAs(V) anions and bentonite surface In addition the hydroxylions and arsenate species could compete for adsorption athigh pH causing a reduction in As(V) adsorption Experi-mental results showed that As(V) had amaximum adsorptionat pH 30 for Fe-B sample and pH 40 for the Al-B sample-erefore pH 30 and pH 40 were selected for further ex-periments respectively for Fe-B and Al-B samples

In order to get more understanding of mechanism forarsenate absorption onto modified bentonite the As(V)absorption at different pH was carried out -e pH valuesbefore and after the absorption are shown in Table 2

From Table 2 it can be observed that the values of the pHfor all of cases in the adsorption experiment changed -epH values decreased after the arsenate absorption onto Fe-B-is could be explained by the reaction between the ab-sorption sites Fe-OH(surface) and H3AsO4(solution) creatingthe surface complexes such as the followingFe-OH(surface) + H3AsO4(solution) Fe-HAsO4

minus+ H(solution)

+

+ H2O(2)

-e liberation of H+ ions decreased pH of the solution-e pH increased after the As(V) absorption onto Al-B

sample due to the following reaction

(FeAl)minusOH(surface) + H2AsO4(solution)minus

(FeAl)minusH2AsO4(surface) + OH(solution)minus (3)

-e liberation of OHminus ions increased pH of the solutionSo in this pH range the main adsorption mechanisms

could be considered as the electrostatic interactions and ionexchange

FTIR spectra of Fe-B before and after the As(V) ab-sorption are depicted in Figure 7

Figure 7 shows a band in the range of 3500ndash3700 cmminus1related to the stretching vibration of the structural hydroxylsgroup (AlAlOH AlMgOH) [5] a strong band at 3563 cmminus1related to the O-H stretching vibration of the silanol (Si-OH)groups and HO-H vibration of the water adsorbed silicasurface [5] -e adsorption band at 1635 cmminus1 was due to the

deformation band (δ(O-H)) of physisorbed water [17] AfterAs(V) adsorption these peaks were also observed with de-creased intensity -is should be assigned to the direct in-teractions between arsenate anions and Fe-OH and Al-OHgroups at corners of bentonite layers to create Fe-O-As(V) orAl-O-As(V) bonds which decreased intensity of these peaksIn addition a new peak with low intensity was observed at879 cmminus1 corresponding to As-O vibration inHAsO4

2minus anionindicating that there was the As(V) adsorption onto Fe-B

-e SEM images of Fe-B Fe-B after the As(V) ad-sorption Al-B and Al-B after the As(V) adsorption areshown in Figure 8

-e morphology of modified bentonite changed clearlyby the As(V) adsorption -e morphology of Fe-B includedplates with diameter of several μm around of which particlesof small sizes were located -is morphology might facilitatefor As(V) to adsorb onto modified bentonite After As(V)adsorption the lamellar structure of the Fe-B was left and alarge number of flakes appeared -is indicated that therewas a change in distance between the clay particles afterarsenate adsorption In addition the small-size particlesaround the clay plates disappeared suggesting that smallclusters of Fe(III) oxides and hydroxides were also ad-sorption sites on surfaces -e morphology of Al-B sampleconsisted of the aggregate of smectites with irregular shapeand partly a mass of flake shape After arsenate adsorptionthe modified clay surface was changed to an aggregatedmorphology and there were several clusters around the clayplates -is indicated that the As(V) adsorption had a stronginfluence on the structure and morphology of modifiedbentonites

322 Adsorption Kinetics Experimental kinetic data wereevaluated by using pseudo-first-order and pseudo-second-order kinetic models -e pseudo-first-order kinetic modelin linear form is presented in the following equation

1 2 3 4 5 6 7 8 9 10

8

10

12

14

16

18

q e (m

gmiddotgndash1

)

pH

Fe-BAl-B

Figure 5 Effect of pH on the adsorption capacity of As(V) ontoFe-B sample (Co(As) 1298mgL) and Al-B sample (Co(As)

1684mgL) (T 303K m 005 g t 4 h)

Advances in Materials Science and Engineering 5

ln qe minus qt( 1113857 ln qe minus k1 middot t (4)

where qe and qt are the adsorption capacity at equilibriumand at time t (mgg) and k1 is the pseudo-first-order rateconstant (minminus1)

-e pseudo-second-order kinetic model is given by[23 24]

t

qt

1

k2q2e

+1qe

middot t (5)

where k2 is the equilibrium rate constant of pseudo-second-order kinetic model (gmolmiddotmin)

-e goodness of fit for the compatible model is assessedbased on determination coefficient R2 for the regressionequation

-e plots of pseudo-first-order and pseudo-second-orderkinetic models are illustrated in Figures 9 and 10 respectively-eir parameters are summarized in Table 3 -e high de-termination coefficients (gt092) as well as the calculated qevalues close to the experimental ones indicated that pseudo-second-order kinetic model was more suitable for the de-scription of the adsorption kinetics of arsenate on modifiedbentonite (Table 3) -is implied that the adsorption processcould be chemisorption [23 24] -e values of qe at differenttemperatures for Al-B were greater than those for Fe-B in-dicating that the adsorption capacity of Al-B is larger than thatof Fe-B -e average diameter of H2AsO4

minus ions was about35 A meanwhile the pore diameter of studied materials wasabout 26ndash220 A so arsenate ions were easy to move inside themesopores of materials without being obstructed the geometry

Table 3 shows that the value of k2 increased with in-creasing temperature for both two samples (Fe-B 035310minus3ndash730110minus3 gmgmiddotmin Al-B 2810minus3ndash5810minus3 gmgmiddotmin)

-e activation energy can be computed by using theArrhenius equation

ln k2 minusEa

RT+ lnA (6)

where A is the Arrhenius constant (gmgmiddotmin) Ea the ac-tivation energy of adsorption (kJmol) R is the gas constant(8314 JmolmiddotK) and T is the absolute temperature (K) -eactivation energy (Ea) was obtained from the slope of thelinear plot of ln k2 versus 1T (Figure 11(a))

Besides calculating the activation energy the Gibbsenergy ΔG enthalpy ΔH and entropy ΔS of the activation

Table 2 pH of As(V) solution before and after the arsenate ab-sorption onto Fe-B (Co(As) 1298mgL) and Al-B (Co(As)

1684mgL) (T 303K m 005 g)

pH before the arsenateabsorption 20 30 40 50 60 70 80 90

pH after the arsenateabsorption onto Fe-B 20 29 33 mdash 40 48 70 72

pH after the arsenateabsorption onto Al-B 27 37 54 58 64 79 81 94

4500 4000 3500 3000 2500 2000 1500 1000 500

100

879

13841631

Fe-B-Abs

Fe-B

Wave number (cmndash1)

T

(Arb

)

Figure 7 FT-IR spectra of Fe-B before and after the As(V)adsorption

4 6 8 10

ndash6

ndash4

ndash2

0

NaCl 01 MNaCl 001 M

pH

∆pH

(a)

NaCl 01 MNaCl 001 M

4 6 8 10pH

ndash3

ndash2

ndash1

0

1

ΔpH

(b)

Figure 6 Point of zero charge plots of Fe-B (a) and Al-B (b)

6 Advances in Materials Science and Engineering

for As(V) adsorption kinetics can be computed by using theEyring equation [25]

lnk2

T ln

kb

h1113888 1113889minus

ΔG

R middot T minusΔH

Rmiddot1T

+ lnkb

h1113888 1113889 +

ΔS

R1113890 1113891

(7)

where kb (13807times10minus23 JK) is the Boltzmann constant h(6621times 10minus34 Jmiddots) is the Planck constant ΔG is the Gibbs

energy of activation ΔH is the activation enthalpy and ΔSis the activation entropy

-e linear plot of ln(kT) versus 1Tgives a straight line-e activation parameters could be derived from the slopeand intercepts of these lines (Figure 11(b))

-e values of the activation energy were found to be8029 kJmol and 4190 kJmol for the arsenate adsorptiononto Fe-B and Al-B respectively (Table 4)-emagnitude ofactivation energy can give information on whether the

(a) (b)

(c) (d)

Figure 8 SEM images of Fe-B (a) Fe-B after the As(V) adsorption (b) Al-B (c) and Al-B after the As(V) adsorption (d)

0 40 80 120 160 200

ndash2

ndash1

0

1

2

3

ln (q

e ndash qt)

Time (min)

283 K293 K

303 K313 K

(a)

283 K293 K

303 K313 K

0 100 200

0

5

10

15

tqt (

min

middotgmiddotm

gndash1)

Time (min)

(b)

Figure 9 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Fe-B at differenttemperatures

Advances in Materials Science and Engineering 7

283 K293 K

303 K313 K

ndash05

00

05

10

15

20

25ln

(qe ndash

qt)

Time (min)0 30 60 90 120 150 180

(a)

283 K293 K

303 K313 K

0

3

6

9

12

tqt (

min

middotgmiddotm

gndash1)

Time (min)0 50 100 150 200 250

(b)

Figure 10 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Al-B at differenttemperatures

Table 3 Parameters of pseudo-first-order and pseudo-second-order kinetic model of As(V) adsorption by Fe-B and Al-B at differenttemperatures

Adsorbent T (K) qe (experimental) (mgg)First-order kinetic model Second-order kinetic model

k1 (minminus1) qe (cal) (mgg) R2 k2 (gmgmiddotmin) qe (cal) (mgg) R2

Fe-B

283 1438 0010 1519 0942 035times10minus3 2114 0924293 1442 0013 1244 0977 068times10minus3 1980 0973303 1442 0027 980 0962 420times10minus3 1553 0999313 1444 0021 657 0992 730times10minus3 1497 0998

Al-B

283 1847 16times10minus3 1635 0956 10times10minus3 2222 0984293 2075 19times10minus3 1301 0948 29times10minus3 2222 0998303 2080 70times10minus3 856 0949 42times10minus3 2083 0992313 2105 90times10minus3 709 0752 58times10minus3 2128 0996

ndash8

ndash7

ndash6

ndash5

ln k 2

1T (Kndash1)

FendashB R2 = 0952AlndashB R2 = 0924

00032 00033 00034 00035

(a)

FendashB R2 = 0946AlndashB R2 = 0912

ndash14

ndash13

ndash12

ndash11

ndash10

1T (Kndash1)

ln (k

2T)

00032 00033 00034 00035

(b)

Figure 11 (a) Arrhenius plots and (b) Eyring plots of As(V) adsorption onto Fe-B and Al-B

8 Advances in Materials Science and Engineering

adsorption process is physical or chemical Ramesh et al [5]reported that the activation energy of physisorption wasnormally not more than 42 kJmol Hence the values ofactivation energy were found in this study suggesting thatthe adsorption of As(V) on Fe-B was a chemical adsorption-e smaller Ea for the adsorption of As(V) on Al-B was dueto the formation of weak chemical bond between absorbentand adsorbate According to the literature the rate constantincreased when decreasing the value of activation energy orincreasing the frequency factor A -e calculated A valueswere found to be 18times10minus11 and 80821 for the adsorption ofAs(V) on Fe-B and on Al-B respectively -ese results wereinteresting due to showing ldquothe compensation effectrdquo inheterogeneous adsorption

-e free energy of activation (ΔG) activation enthalpy(ΔH) and activation entropy (ΔS) are listed in Table 4-epositive value of ΔH for both samples confirmed an en-dothermic process -e magnitude and sign of ∆S can givean indication of whether the adsorption reaction is an as-sociative or dissociative mechanism [25] -e high negativevalues of ΔS manifested that the As(V) adsorption processwas an associative mechanism -is was additional evidencefor the analysis of adsorption mechanism as described inSection 321 -e large positive values of ΔG inferred thatthe adsorption reactions required energy to convert thereactants into products [26]

323 Adsorption Isotherms Equilibrium studies were car-ried out to obtain the adsorption capacity of modifiedbentonite at different temperatures Two adsorption iso-therms namely the Langmuir [23] and the Freundlich [23]isotherms were employed to analyze the adsorption data-e linear form of Langmuir isotherm is given by

Ce

qe

Ce

qm+

1KL middot qm

(8)

where qe is the equilibrium adsorption capacity (mgg) Ce isthe equilibrium arsenate concentration in solution (mgL)qm is the monolayer adsorption capacity of the adsorbent(mgg) and KL is the Langmuir constant (Lmg) which isrelated to the energy of adsorption respectively qm and KLcan be computed from the intercept and slope of the linearplot with Ceqe versus Ce

In addition a separation factor RL (also equilibriumparameter) is defined by the following equation

RL 1

1 + KLCi (9)

where Ci (mgL) is the initial dye concentration and KL(Lmg) is the Langmuir constant -e value of RL indicatesthe shape of the isotherms to be either unfavorable (RLgt 1)linear (RL 1) favorable (0ltRLlt 1) or irreversible (RL 0)

-e Freundlich isotherm was applied to the adsorptionon a heterogeneous surface with uniform energy -e linearform of this model can be expressed as follows

ln qe lnKF +1n

middot lnCe (10)

where qe and Ce are the equilibrium adsorption capacity(mgg) and equilibrium concentration in liquid phases (mgL) respectively KF and n are the Freundlich constants whichare related to adsorption capacity and intensity respectively-e linear plot with ln qe versus ln Ce can provide the valuesof KF and n from the slope and intercepts

-e plots for he Langmuir and Freundlich isothermmodels are shown in Figures 12 and 13

As seen from Table 5 the high values of R2 for theLangmuir isotherm model (R2gt 0920) as compared withthose for the Freundlich isotherm model (R2lt 0875) and thevalues of RL in the range 0 and 1 inferred that As(V) ad-sorption onto the modified bentonite was favorable for theLangmuir model Based on the maximum monolayer ad-sorption capacity of the adsorbent qm (mgg) specific area ofmodified bentonite can computed by the following expression

S qAsmaxMAs

middot NA middot σAs (11)

where qAsmax is the Langmuir monolayer adsorption capacityMAs is the molar masse of As NA is Avogadro number andσAs is the surface area of AsO4

3minus (σAs π middot r2 r 17 A)Specific surface area of modified bentonite was calcu-

lated at the temperature of 283K as follows

S(FeminusB) 177675

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

1296m2g

S(AlminusB) 294175

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

2146m2g

(12)

-e effective surface area values of the studied sampleswere less than SBET of Fe-B (14607m2g) and Al-B(17013m2g) indicating that the As(V) absorption ontostudied materials only occurred at the outer surfaces and inthe large pores of bentonite particles

-e maximum As(V) adsorption capacities (qm)computed from the Langmuir model at 303 K were1898mgg for Fe-B and 3571mgg for Al-B As can be seenfrom Table 6 the adsorption capacity for arsenate

Table 4 Activation energy and activation parameters of adsorptionprocess

T (K) Ea (kJmol) ∆H (kJmol) ΔS (kJmolK) ΔG (kJmol)Fe-B283 8029 7782 minus0037 8841293 8879303 8916313 8953Al-B

4190 3932 minus0162 8516867888409002

Advances in Materials Science and Engineering 9

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

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Al-B sample was explained by the increase of the number ofmicropores

32 Adsorption Studies

321 Effect of pH -e pH effect on the arsenate adsorptioncapacity of polymeric AlFe-modified bentonite is shown inFigure 5

It was found that the best adsorption of As(V) ontomodified bentonite was in the range of pH 20ndash40 Whenincreasing pH from 40 to 90 the amount of arsenateadsorbed (qe) decreased -e point of zero charge (pHPZC) ofFe-B and Al-B samples was respectively found to be 31 and48 (Figure 6) At pHlt pHPZC the modified bentonite surfacewas positively charged so it favored for the adsorption ofarsenic species in the form of H2AsO4

minus anions by electrostaticinteraction However at a pHgtpHPZC the modified surfacewas negatively charged causing a repulsion force between theAs(V) anions and bentonite surface In addition the hydroxylions and arsenate species could compete for adsorption athigh pH causing a reduction in As(V) adsorption Experi-mental results showed that As(V) had amaximum adsorptionat pH 30 for Fe-B sample and pH 40 for the Al-B sample-erefore pH 30 and pH 40 were selected for further ex-periments respectively for Fe-B and Al-B samples

In order to get more understanding of mechanism forarsenate absorption onto modified bentonite the As(V)absorption at different pH was carried out -e pH valuesbefore and after the absorption are shown in Table 2

From Table 2 it can be observed that the values of the pHfor all of cases in the adsorption experiment changed -epH values decreased after the arsenate absorption onto Fe-B-is could be explained by the reaction between the ab-sorption sites Fe-OH(surface) and H3AsO4(solution) creatingthe surface complexes such as the followingFe-OH(surface) + H3AsO4(solution) Fe-HAsO4

minus+ H(solution)

+

+ H2O(2)

-e liberation of H+ ions decreased pH of the solution-e pH increased after the As(V) absorption onto Al-B

sample due to the following reaction

(FeAl)minusOH(surface) + H2AsO4(solution)minus

(FeAl)minusH2AsO4(surface) + OH(solution)minus (3)

-e liberation of OHminus ions increased pH of the solutionSo in this pH range the main adsorption mechanisms

could be considered as the electrostatic interactions and ionexchange

FTIR spectra of Fe-B before and after the As(V) ab-sorption are depicted in Figure 7

Figure 7 shows a band in the range of 3500ndash3700 cmminus1related to the stretching vibration of the structural hydroxylsgroup (AlAlOH AlMgOH) [5] a strong band at 3563 cmminus1related to the O-H stretching vibration of the silanol (Si-OH)groups and HO-H vibration of the water adsorbed silicasurface [5] -e adsorption band at 1635 cmminus1 was due to the

deformation band (δ(O-H)) of physisorbed water [17] AfterAs(V) adsorption these peaks were also observed with de-creased intensity -is should be assigned to the direct in-teractions between arsenate anions and Fe-OH and Al-OHgroups at corners of bentonite layers to create Fe-O-As(V) orAl-O-As(V) bonds which decreased intensity of these peaksIn addition a new peak with low intensity was observed at879 cmminus1 corresponding to As-O vibration inHAsO4

2minus anionindicating that there was the As(V) adsorption onto Fe-B

-e SEM images of Fe-B Fe-B after the As(V) ad-sorption Al-B and Al-B after the As(V) adsorption areshown in Figure 8

-e morphology of modified bentonite changed clearlyby the As(V) adsorption -e morphology of Fe-B includedplates with diameter of several μm around of which particlesof small sizes were located -is morphology might facilitatefor As(V) to adsorb onto modified bentonite After As(V)adsorption the lamellar structure of the Fe-B was left and alarge number of flakes appeared -is indicated that therewas a change in distance between the clay particles afterarsenate adsorption In addition the small-size particlesaround the clay plates disappeared suggesting that smallclusters of Fe(III) oxides and hydroxides were also ad-sorption sites on surfaces -e morphology of Al-B sampleconsisted of the aggregate of smectites with irregular shapeand partly a mass of flake shape After arsenate adsorptionthe modified clay surface was changed to an aggregatedmorphology and there were several clusters around the clayplates -is indicated that the As(V) adsorption had a stronginfluence on the structure and morphology of modifiedbentonites

322 Adsorption Kinetics Experimental kinetic data wereevaluated by using pseudo-first-order and pseudo-second-order kinetic models -e pseudo-first-order kinetic modelin linear form is presented in the following equation

1 2 3 4 5 6 7 8 9 10

8

10

12

14

16

18

q e (m

gmiddotgndash1

)

pH

Fe-BAl-B

Figure 5 Effect of pH on the adsorption capacity of As(V) ontoFe-B sample (Co(As) 1298mgL) and Al-B sample (Co(As)

1684mgL) (T 303K m 005 g t 4 h)

Advances in Materials Science and Engineering 5

ln qe minus qt( 1113857 ln qe minus k1 middot t (4)

where qe and qt are the adsorption capacity at equilibriumand at time t (mgg) and k1 is the pseudo-first-order rateconstant (minminus1)

-e pseudo-second-order kinetic model is given by[23 24]

t

qt

1

k2q2e

+1qe

middot t (5)

where k2 is the equilibrium rate constant of pseudo-second-order kinetic model (gmolmiddotmin)

-e goodness of fit for the compatible model is assessedbased on determination coefficient R2 for the regressionequation

-e plots of pseudo-first-order and pseudo-second-orderkinetic models are illustrated in Figures 9 and 10 respectively-eir parameters are summarized in Table 3 -e high de-termination coefficients (gt092) as well as the calculated qevalues close to the experimental ones indicated that pseudo-second-order kinetic model was more suitable for the de-scription of the adsorption kinetics of arsenate on modifiedbentonite (Table 3) -is implied that the adsorption processcould be chemisorption [23 24] -e values of qe at differenttemperatures for Al-B were greater than those for Fe-B in-dicating that the adsorption capacity of Al-B is larger than thatof Fe-B -e average diameter of H2AsO4

minus ions was about35 A meanwhile the pore diameter of studied materials wasabout 26ndash220 A so arsenate ions were easy to move inside themesopores of materials without being obstructed the geometry

Table 3 shows that the value of k2 increased with in-creasing temperature for both two samples (Fe-B 035310minus3ndash730110minus3 gmgmiddotmin Al-B 2810minus3ndash5810minus3 gmgmiddotmin)

-e activation energy can be computed by using theArrhenius equation

ln k2 minusEa

RT+ lnA (6)

where A is the Arrhenius constant (gmgmiddotmin) Ea the ac-tivation energy of adsorption (kJmol) R is the gas constant(8314 JmolmiddotK) and T is the absolute temperature (K) -eactivation energy (Ea) was obtained from the slope of thelinear plot of ln k2 versus 1T (Figure 11(a))

Besides calculating the activation energy the Gibbsenergy ΔG enthalpy ΔH and entropy ΔS of the activation

Table 2 pH of As(V) solution before and after the arsenate ab-sorption onto Fe-B (Co(As) 1298mgL) and Al-B (Co(As)

1684mgL) (T 303K m 005 g)

pH before the arsenateabsorption 20 30 40 50 60 70 80 90

pH after the arsenateabsorption onto Fe-B 20 29 33 mdash 40 48 70 72

pH after the arsenateabsorption onto Al-B 27 37 54 58 64 79 81 94

4500 4000 3500 3000 2500 2000 1500 1000 500

100

879

13841631

Fe-B-Abs

Fe-B

Wave number (cmndash1)

T

(Arb

)

Figure 7 FT-IR spectra of Fe-B before and after the As(V)adsorption

4 6 8 10

ndash6

ndash4

ndash2

0

NaCl 01 MNaCl 001 M

pH

∆pH

(a)

NaCl 01 MNaCl 001 M

4 6 8 10pH

ndash3

ndash2

ndash1

0

1

ΔpH

(b)

Figure 6 Point of zero charge plots of Fe-B (a) and Al-B (b)

6 Advances in Materials Science and Engineering

for As(V) adsorption kinetics can be computed by using theEyring equation [25]

lnk2

T ln

kb

h1113888 1113889minus

ΔG

R middot T minusΔH

Rmiddot1T

+ lnkb

h1113888 1113889 +

ΔS

R1113890 1113891

(7)

where kb (13807times10minus23 JK) is the Boltzmann constant h(6621times 10minus34 Jmiddots) is the Planck constant ΔG is the Gibbs

energy of activation ΔH is the activation enthalpy and ΔSis the activation entropy

-e linear plot of ln(kT) versus 1Tgives a straight line-e activation parameters could be derived from the slopeand intercepts of these lines (Figure 11(b))

-e values of the activation energy were found to be8029 kJmol and 4190 kJmol for the arsenate adsorptiononto Fe-B and Al-B respectively (Table 4)-emagnitude ofactivation energy can give information on whether the

(a) (b)

(c) (d)

Figure 8 SEM images of Fe-B (a) Fe-B after the As(V) adsorption (b) Al-B (c) and Al-B after the As(V) adsorption (d)

0 40 80 120 160 200

ndash2

ndash1

0

1

2

3

ln (q

e ndash qt)

Time (min)

283 K293 K

303 K313 K

(a)

283 K293 K

303 K313 K

0 100 200

0

5

10

15

tqt (

min

middotgmiddotm

gndash1)

Time (min)

(b)

Figure 9 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Fe-B at differenttemperatures

Advances in Materials Science and Engineering 7

283 K293 K

303 K313 K

ndash05

00

05

10

15

20

25ln

(qe ndash

qt)

Time (min)0 30 60 90 120 150 180

(a)

283 K293 K

303 K313 K

0

3

6

9

12

tqt (

min

middotgmiddotm

gndash1)

Time (min)0 50 100 150 200 250

(b)

Figure 10 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Al-B at differenttemperatures

Table 3 Parameters of pseudo-first-order and pseudo-second-order kinetic model of As(V) adsorption by Fe-B and Al-B at differenttemperatures

Adsorbent T (K) qe (experimental) (mgg)First-order kinetic model Second-order kinetic model

k1 (minminus1) qe (cal) (mgg) R2 k2 (gmgmiddotmin) qe (cal) (mgg) R2

Fe-B

283 1438 0010 1519 0942 035times10minus3 2114 0924293 1442 0013 1244 0977 068times10minus3 1980 0973303 1442 0027 980 0962 420times10minus3 1553 0999313 1444 0021 657 0992 730times10minus3 1497 0998

Al-B

283 1847 16times10minus3 1635 0956 10times10minus3 2222 0984293 2075 19times10minus3 1301 0948 29times10minus3 2222 0998303 2080 70times10minus3 856 0949 42times10minus3 2083 0992313 2105 90times10minus3 709 0752 58times10minus3 2128 0996

ndash8

ndash7

ndash6

ndash5

ln k 2

1T (Kndash1)

FendashB R2 = 0952AlndashB R2 = 0924

00032 00033 00034 00035

(a)

FendashB R2 = 0946AlndashB R2 = 0912

ndash14

ndash13

ndash12

ndash11

ndash10

1T (Kndash1)

ln (k

2T)

00032 00033 00034 00035

(b)

Figure 11 (a) Arrhenius plots and (b) Eyring plots of As(V) adsorption onto Fe-B and Al-B

8 Advances in Materials Science and Engineering

adsorption process is physical or chemical Ramesh et al [5]reported that the activation energy of physisorption wasnormally not more than 42 kJmol Hence the values ofactivation energy were found in this study suggesting thatthe adsorption of As(V) on Fe-B was a chemical adsorption-e smaller Ea for the adsorption of As(V) on Al-B was dueto the formation of weak chemical bond between absorbentand adsorbate According to the literature the rate constantincreased when decreasing the value of activation energy orincreasing the frequency factor A -e calculated A valueswere found to be 18times10minus11 and 80821 for the adsorption ofAs(V) on Fe-B and on Al-B respectively -ese results wereinteresting due to showing ldquothe compensation effectrdquo inheterogeneous adsorption

-e free energy of activation (ΔG) activation enthalpy(ΔH) and activation entropy (ΔS) are listed in Table 4-epositive value of ΔH for both samples confirmed an en-dothermic process -e magnitude and sign of ∆S can givean indication of whether the adsorption reaction is an as-sociative or dissociative mechanism [25] -e high negativevalues of ΔS manifested that the As(V) adsorption processwas an associative mechanism -is was additional evidencefor the analysis of adsorption mechanism as described inSection 321 -e large positive values of ΔG inferred thatthe adsorption reactions required energy to convert thereactants into products [26]

323 Adsorption Isotherms Equilibrium studies were car-ried out to obtain the adsorption capacity of modifiedbentonite at different temperatures Two adsorption iso-therms namely the Langmuir [23] and the Freundlich [23]isotherms were employed to analyze the adsorption data-e linear form of Langmuir isotherm is given by

Ce

qe

Ce

qm+

1KL middot qm

(8)

where qe is the equilibrium adsorption capacity (mgg) Ce isthe equilibrium arsenate concentration in solution (mgL)qm is the monolayer adsorption capacity of the adsorbent(mgg) and KL is the Langmuir constant (Lmg) which isrelated to the energy of adsorption respectively qm and KLcan be computed from the intercept and slope of the linearplot with Ceqe versus Ce

In addition a separation factor RL (also equilibriumparameter) is defined by the following equation

RL 1

1 + KLCi (9)

where Ci (mgL) is the initial dye concentration and KL(Lmg) is the Langmuir constant -e value of RL indicatesthe shape of the isotherms to be either unfavorable (RLgt 1)linear (RL 1) favorable (0ltRLlt 1) or irreversible (RL 0)

-e Freundlich isotherm was applied to the adsorptionon a heterogeneous surface with uniform energy -e linearform of this model can be expressed as follows

ln qe lnKF +1n

middot lnCe (10)

where qe and Ce are the equilibrium adsorption capacity(mgg) and equilibrium concentration in liquid phases (mgL) respectively KF and n are the Freundlich constants whichare related to adsorption capacity and intensity respectively-e linear plot with ln qe versus ln Ce can provide the valuesof KF and n from the slope and intercepts

-e plots for he Langmuir and Freundlich isothermmodels are shown in Figures 12 and 13

As seen from Table 5 the high values of R2 for theLangmuir isotherm model (R2gt 0920) as compared withthose for the Freundlich isotherm model (R2lt 0875) and thevalues of RL in the range 0 and 1 inferred that As(V) ad-sorption onto the modified bentonite was favorable for theLangmuir model Based on the maximum monolayer ad-sorption capacity of the adsorbent qm (mgg) specific area ofmodified bentonite can computed by the following expression

S qAsmaxMAs

middot NA middot σAs (11)

where qAsmax is the Langmuir monolayer adsorption capacityMAs is the molar masse of As NA is Avogadro number andσAs is the surface area of AsO4

3minus (σAs π middot r2 r 17 A)Specific surface area of modified bentonite was calcu-

lated at the temperature of 283K as follows

S(FeminusB) 177675

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

1296m2g

S(AlminusB) 294175

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

2146m2g

(12)

-e effective surface area values of the studied sampleswere less than SBET of Fe-B (14607m2g) and Al-B(17013m2g) indicating that the As(V) absorption ontostudied materials only occurred at the outer surfaces and inthe large pores of bentonite particles

-e maximum As(V) adsorption capacities (qm)computed from the Langmuir model at 303 K were1898mgg for Fe-B and 3571mgg for Al-B As can be seenfrom Table 6 the adsorption capacity for arsenate

Table 4 Activation energy and activation parameters of adsorptionprocess

T (K) Ea (kJmol) ∆H (kJmol) ΔS (kJmolK) ΔG (kJmol)Fe-B283 8029 7782 minus0037 8841293 8879303 8916313 8953Al-B

4190 3932 minus0162 8516867888409002

Advances in Materials Science and Engineering 9

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

ln qe minus qt( 1113857 ln qe minus k1 middot t (4)

where qe and qt are the adsorption capacity at equilibriumand at time t (mgg) and k1 is the pseudo-first-order rateconstant (minminus1)

-e pseudo-second-order kinetic model is given by[23 24]

t

qt

1

k2q2e

+1qe

middot t (5)

where k2 is the equilibrium rate constant of pseudo-second-order kinetic model (gmolmiddotmin)

-e goodness of fit for the compatible model is assessedbased on determination coefficient R2 for the regressionequation

-e plots of pseudo-first-order and pseudo-second-orderkinetic models are illustrated in Figures 9 and 10 respectively-eir parameters are summarized in Table 3 -e high de-termination coefficients (gt092) as well as the calculated qevalues close to the experimental ones indicated that pseudo-second-order kinetic model was more suitable for the de-scription of the adsorption kinetics of arsenate on modifiedbentonite (Table 3) -is implied that the adsorption processcould be chemisorption [23 24] -e values of qe at differenttemperatures for Al-B were greater than those for Fe-B in-dicating that the adsorption capacity of Al-B is larger than thatof Fe-B -e average diameter of H2AsO4

minus ions was about35 A meanwhile the pore diameter of studied materials wasabout 26ndash220 A so arsenate ions were easy to move inside themesopores of materials without being obstructed the geometry

Table 3 shows that the value of k2 increased with in-creasing temperature for both two samples (Fe-B 035310minus3ndash730110minus3 gmgmiddotmin Al-B 2810minus3ndash5810minus3 gmgmiddotmin)

-e activation energy can be computed by using theArrhenius equation

ln k2 minusEa

RT+ lnA (6)

where A is the Arrhenius constant (gmgmiddotmin) Ea the ac-tivation energy of adsorption (kJmol) R is the gas constant(8314 JmolmiddotK) and T is the absolute temperature (K) -eactivation energy (Ea) was obtained from the slope of thelinear plot of ln k2 versus 1T (Figure 11(a))

Besides calculating the activation energy the Gibbsenergy ΔG enthalpy ΔH and entropy ΔS of the activation

Table 2 pH of As(V) solution before and after the arsenate ab-sorption onto Fe-B (Co(As) 1298mgL) and Al-B (Co(As)

1684mgL) (T 303K m 005 g)

pH before the arsenateabsorption 20 30 40 50 60 70 80 90

pH after the arsenateabsorption onto Fe-B 20 29 33 mdash 40 48 70 72

pH after the arsenateabsorption onto Al-B 27 37 54 58 64 79 81 94

4500 4000 3500 3000 2500 2000 1500 1000 500

100

879

13841631

Fe-B-Abs

Fe-B

Wave number (cmndash1)

T

(Arb

)

Figure 7 FT-IR spectra of Fe-B before and after the As(V)adsorption

4 6 8 10

ndash6

ndash4

ndash2

0

NaCl 01 MNaCl 001 M

pH

∆pH

(a)

NaCl 01 MNaCl 001 M

4 6 8 10pH

ndash3

ndash2

ndash1

0

1

ΔpH

(b)

Figure 6 Point of zero charge plots of Fe-B (a) and Al-B (b)

6 Advances in Materials Science and Engineering

for As(V) adsorption kinetics can be computed by using theEyring equation [25]

lnk2

T ln

kb

h1113888 1113889minus

ΔG

R middot T minusΔH

Rmiddot1T

+ lnkb

h1113888 1113889 +

ΔS

R1113890 1113891

(7)

where kb (13807times10minus23 JK) is the Boltzmann constant h(6621times 10minus34 Jmiddots) is the Planck constant ΔG is the Gibbs

energy of activation ΔH is the activation enthalpy and ΔSis the activation entropy

-e linear plot of ln(kT) versus 1Tgives a straight line-e activation parameters could be derived from the slopeand intercepts of these lines (Figure 11(b))

-e values of the activation energy were found to be8029 kJmol and 4190 kJmol for the arsenate adsorptiononto Fe-B and Al-B respectively (Table 4)-emagnitude ofactivation energy can give information on whether the

(a) (b)

(c) (d)

Figure 8 SEM images of Fe-B (a) Fe-B after the As(V) adsorption (b) Al-B (c) and Al-B after the As(V) adsorption (d)

0 40 80 120 160 200

ndash2

ndash1

0

1

2

3

ln (q

e ndash qt)

Time (min)

283 K293 K

303 K313 K

(a)

283 K293 K

303 K313 K

0 100 200

0

5

10

15

tqt (

min

middotgmiddotm

gndash1)

Time (min)

(b)

Figure 9 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Fe-B at differenttemperatures

Advances in Materials Science and Engineering 7

283 K293 K

303 K313 K

ndash05

00

05

10

15

20

25ln

(qe ndash

qt)

Time (min)0 30 60 90 120 150 180

(a)

283 K293 K

303 K313 K

0

3

6

9

12

tqt (

min

middotgmiddotm

gndash1)

Time (min)0 50 100 150 200 250

(b)

Figure 10 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Al-B at differenttemperatures

Table 3 Parameters of pseudo-first-order and pseudo-second-order kinetic model of As(V) adsorption by Fe-B and Al-B at differenttemperatures

Adsorbent T (K) qe (experimental) (mgg)First-order kinetic model Second-order kinetic model

k1 (minminus1) qe (cal) (mgg) R2 k2 (gmgmiddotmin) qe (cal) (mgg) R2

Fe-B

283 1438 0010 1519 0942 035times10minus3 2114 0924293 1442 0013 1244 0977 068times10minus3 1980 0973303 1442 0027 980 0962 420times10minus3 1553 0999313 1444 0021 657 0992 730times10minus3 1497 0998

Al-B

283 1847 16times10minus3 1635 0956 10times10minus3 2222 0984293 2075 19times10minus3 1301 0948 29times10minus3 2222 0998303 2080 70times10minus3 856 0949 42times10minus3 2083 0992313 2105 90times10minus3 709 0752 58times10minus3 2128 0996

ndash8

ndash7

ndash6

ndash5

ln k 2

1T (Kndash1)

FendashB R2 = 0952AlndashB R2 = 0924

00032 00033 00034 00035

(a)

FendashB R2 = 0946AlndashB R2 = 0912

ndash14

ndash13

ndash12

ndash11

ndash10

1T (Kndash1)

ln (k

2T)

00032 00033 00034 00035

(b)

Figure 11 (a) Arrhenius plots and (b) Eyring plots of As(V) adsorption onto Fe-B and Al-B

8 Advances in Materials Science and Engineering

adsorption process is physical or chemical Ramesh et al [5]reported that the activation energy of physisorption wasnormally not more than 42 kJmol Hence the values ofactivation energy were found in this study suggesting thatthe adsorption of As(V) on Fe-B was a chemical adsorption-e smaller Ea for the adsorption of As(V) on Al-B was dueto the formation of weak chemical bond between absorbentand adsorbate According to the literature the rate constantincreased when decreasing the value of activation energy orincreasing the frequency factor A -e calculated A valueswere found to be 18times10minus11 and 80821 for the adsorption ofAs(V) on Fe-B and on Al-B respectively -ese results wereinteresting due to showing ldquothe compensation effectrdquo inheterogeneous adsorption

-e free energy of activation (ΔG) activation enthalpy(ΔH) and activation entropy (ΔS) are listed in Table 4-epositive value of ΔH for both samples confirmed an en-dothermic process -e magnitude and sign of ∆S can givean indication of whether the adsorption reaction is an as-sociative or dissociative mechanism [25] -e high negativevalues of ΔS manifested that the As(V) adsorption processwas an associative mechanism -is was additional evidencefor the analysis of adsorption mechanism as described inSection 321 -e large positive values of ΔG inferred thatthe adsorption reactions required energy to convert thereactants into products [26]

323 Adsorption Isotherms Equilibrium studies were car-ried out to obtain the adsorption capacity of modifiedbentonite at different temperatures Two adsorption iso-therms namely the Langmuir [23] and the Freundlich [23]isotherms were employed to analyze the adsorption data-e linear form of Langmuir isotherm is given by

Ce

qe

Ce

qm+

1KL middot qm

(8)

where qe is the equilibrium adsorption capacity (mgg) Ce isthe equilibrium arsenate concentration in solution (mgL)qm is the monolayer adsorption capacity of the adsorbent(mgg) and KL is the Langmuir constant (Lmg) which isrelated to the energy of adsorption respectively qm and KLcan be computed from the intercept and slope of the linearplot with Ceqe versus Ce

In addition a separation factor RL (also equilibriumparameter) is defined by the following equation

RL 1

1 + KLCi (9)

where Ci (mgL) is the initial dye concentration and KL(Lmg) is the Langmuir constant -e value of RL indicatesthe shape of the isotherms to be either unfavorable (RLgt 1)linear (RL 1) favorable (0ltRLlt 1) or irreversible (RL 0)

-e Freundlich isotherm was applied to the adsorptionon a heterogeneous surface with uniform energy -e linearform of this model can be expressed as follows

ln qe lnKF +1n

middot lnCe (10)

where qe and Ce are the equilibrium adsorption capacity(mgg) and equilibrium concentration in liquid phases (mgL) respectively KF and n are the Freundlich constants whichare related to adsorption capacity and intensity respectively-e linear plot with ln qe versus ln Ce can provide the valuesof KF and n from the slope and intercepts

-e plots for he Langmuir and Freundlich isothermmodels are shown in Figures 12 and 13

As seen from Table 5 the high values of R2 for theLangmuir isotherm model (R2gt 0920) as compared withthose for the Freundlich isotherm model (R2lt 0875) and thevalues of RL in the range 0 and 1 inferred that As(V) ad-sorption onto the modified bentonite was favorable for theLangmuir model Based on the maximum monolayer ad-sorption capacity of the adsorbent qm (mgg) specific area ofmodified bentonite can computed by the following expression

S qAsmaxMAs

middot NA middot σAs (11)

where qAsmax is the Langmuir monolayer adsorption capacityMAs is the molar masse of As NA is Avogadro number andσAs is the surface area of AsO4

3minus (σAs π middot r2 r 17 A)Specific surface area of modified bentonite was calcu-

lated at the temperature of 283K as follows

S(FeminusB) 177675

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

1296m2g

S(AlminusB) 294175

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

2146m2g

(12)

-e effective surface area values of the studied sampleswere less than SBET of Fe-B (14607m2g) and Al-B(17013m2g) indicating that the As(V) absorption ontostudied materials only occurred at the outer surfaces and inthe large pores of bentonite particles

-e maximum As(V) adsorption capacities (qm)computed from the Langmuir model at 303 K were1898mgg for Fe-B and 3571mgg for Al-B As can be seenfrom Table 6 the adsorption capacity for arsenate

Table 4 Activation energy and activation parameters of adsorptionprocess

T (K) Ea (kJmol) ∆H (kJmol) ΔS (kJmolK) ΔG (kJmol)Fe-B283 8029 7782 minus0037 8841293 8879303 8916313 8953Al-B

4190 3932 minus0162 8516867888409002

Advances in Materials Science and Engineering 9

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

for As(V) adsorption kinetics can be computed by using theEyring equation [25]

lnk2

T ln

kb

h1113888 1113889minus

ΔG

R middot T minusΔH

Rmiddot1T

+ lnkb

h1113888 1113889 +

ΔS

R1113890 1113891

(7)

where kb (13807times10minus23 JK) is the Boltzmann constant h(6621times 10minus34 Jmiddots) is the Planck constant ΔG is the Gibbs

energy of activation ΔH is the activation enthalpy and ΔSis the activation entropy

-e linear plot of ln(kT) versus 1Tgives a straight line-e activation parameters could be derived from the slopeand intercepts of these lines (Figure 11(b))

-e values of the activation energy were found to be8029 kJmol and 4190 kJmol for the arsenate adsorptiononto Fe-B and Al-B respectively (Table 4)-emagnitude ofactivation energy can give information on whether the

(a) (b)

(c) (d)

Figure 8 SEM images of Fe-B (a) Fe-B after the As(V) adsorption (b) Al-B (c) and Al-B after the As(V) adsorption (d)

0 40 80 120 160 200

ndash2

ndash1

0

1

2

3

ln (q

e ndash qt)

Time (min)

283 K293 K

303 K313 K

(a)

283 K293 K

303 K313 K

0 100 200

0

5

10

15

tqt (

min

middotgmiddotm

gndash1)

Time (min)

(b)

Figure 9 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Fe-B at differenttemperatures

Advances in Materials Science and Engineering 7

283 K293 K

303 K313 K

ndash05

00

05

10

15

20

25ln

(qe ndash

qt)

Time (min)0 30 60 90 120 150 180

(a)

283 K293 K

303 K313 K

0

3

6

9

12

tqt (

min

middotgmiddotm

gndash1)

Time (min)0 50 100 150 200 250

(b)

Figure 10 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Al-B at differenttemperatures

Table 3 Parameters of pseudo-first-order and pseudo-second-order kinetic model of As(V) adsorption by Fe-B and Al-B at differenttemperatures

Adsorbent T (K) qe (experimental) (mgg)First-order kinetic model Second-order kinetic model

k1 (minminus1) qe (cal) (mgg) R2 k2 (gmgmiddotmin) qe (cal) (mgg) R2

Fe-B

283 1438 0010 1519 0942 035times10minus3 2114 0924293 1442 0013 1244 0977 068times10minus3 1980 0973303 1442 0027 980 0962 420times10minus3 1553 0999313 1444 0021 657 0992 730times10minus3 1497 0998

Al-B

283 1847 16times10minus3 1635 0956 10times10minus3 2222 0984293 2075 19times10minus3 1301 0948 29times10minus3 2222 0998303 2080 70times10minus3 856 0949 42times10minus3 2083 0992313 2105 90times10minus3 709 0752 58times10minus3 2128 0996

ndash8

ndash7

ndash6

ndash5

ln k 2

1T (Kndash1)

FendashB R2 = 0952AlndashB R2 = 0924

00032 00033 00034 00035

(a)

FendashB R2 = 0946AlndashB R2 = 0912

ndash14

ndash13

ndash12

ndash11

ndash10

1T (Kndash1)

ln (k

2T)

00032 00033 00034 00035

(b)

Figure 11 (a) Arrhenius plots and (b) Eyring plots of As(V) adsorption onto Fe-B and Al-B

8 Advances in Materials Science and Engineering

adsorption process is physical or chemical Ramesh et al [5]reported that the activation energy of physisorption wasnormally not more than 42 kJmol Hence the values ofactivation energy were found in this study suggesting thatthe adsorption of As(V) on Fe-B was a chemical adsorption-e smaller Ea for the adsorption of As(V) on Al-B was dueto the formation of weak chemical bond between absorbentand adsorbate According to the literature the rate constantincreased when decreasing the value of activation energy orincreasing the frequency factor A -e calculated A valueswere found to be 18times10minus11 and 80821 for the adsorption ofAs(V) on Fe-B and on Al-B respectively -ese results wereinteresting due to showing ldquothe compensation effectrdquo inheterogeneous adsorption

-e free energy of activation (ΔG) activation enthalpy(ΔH) and activation entropy (ΔS) are listed in Table 4-epositive value of ΔH for both samples confirmed an en-dothermic process -e magnitude and sign of ∆S can givean indication of whether the adsorption reaction is an as-sociative or dissociative mechanism [25] -e high negativevalues of ΔS manifested that the As(V) adsorption processwas an associative mechanism -is was additional evidencefor the analysis of adsorption mechanism as described inSection 321 -e large positive values of ΔG inferred thatthe adsorption reactions required energy to convert thereactants into products [26]

323 Adsorption Isotherms Equilibrium studies were car-ried out to obtain the adsorption capacity of modifiedbentonite at different temperatures Two adsorption iso-therms namely the Langmuir [23] and the Freundlich [23]isotherms were employed to analyze the adsorption data-e linear form of Langmuir isotherm is given by

Ce

qe

Ce

qm+

1KL middot qm

(8)

where qe is the equilibrium adsorption capacity (mgg) Ce isthe equilibrium arsenate concentration in solution (mgL)qm is the monolayer adsorption capacity of the adsorbent(mgg) and KL is the Langmuir constant (Lmg) which isrelated to the energy of adsorption respectively qm and KLcan be computed from the intercept and slope of the linearplot with Ceqe versus Ce

In addition a separation factor RL (also equilibriumparameter) is defined by the following equation

RL 1

1 + KLCi (9)

where Ci (mgL) is the initial dye concentration and KL(Lmg) is the Langmuir constant -e value of RL indicatesthe shape of the isotherms to be either unfavorable (RLgt 1)linear (RL 1) favorable (0ltRLlt 1) or irreversible (RL 0)

-e Freundlich isotherm was applied to the adsorptionon a heterogeneous surface with uniform energy -e linearform of this model can be expressed as follows

ln qe lnKF +1n

middot lnCe (10)

where qe and Ce are the equilibrium adsorption capacity(mgg) and equilibrium concentration in liquid phases (mgL) respectively KF and n are the Freundlich constants whichare related to adsorption capacity and intensity respectively-e linear plot with ln qe versus ln Ce can provide the valuesof KF and n from the slope and intercepts

-e plots for he Langmuir and Freundlich isothermmodels are shown in Figures 12 and 13

As seen from Table 5 the high values of R2 for theLangmuir isotherm model (R2gt 0920) as compared withthose for the Freundlich isotherm model (R2lt 0875) and thevalues of RL in the range 0 and 1 inferred that As(V) ad-sorption onto the modified bentonite was favorable for theLangmuir model Based on the maximum monolayer ad-sorption capacity of the adsorbent qm (mgg) specific area ofmodified bentonite can computed by the following expression

S qAsmaxMAs

middot NA middot σAs (11)

where qAsmax is the Langmuir monolayer adsorption capacityMAs is the molar masse of As NA is Avogadro number andσAs is the surface area of AsO4

3minus (σAs π middot r2 r 17 A)Specific surface area of modified bentonite was calcu-

lated at the temperature of 283K as follows

S(FeminusB) 177675

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

1296m2g

S(AlminusB) 294175

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

2146m2g

(12)

-e effective surface area values of the studied sampleswere less than SBET of Fe-B (14607m2g) and Al-B(17013m2g) indicating that the As(V) absorption ontostudied materials only occurred at the outer surfaces and inthe large pores of bentonite particles

-e maximum As(V) adsorption capacities (qm)computed from the Langmuir model at 303 K were1898mgg for Fe-B and 3571mgg for Al-B As can be seenfrom Table 6 the adsorption capacity for arsenate

Table 4 Activation energy and activation parameters of adsorptionprocess

T (K) Ea (kJmol) ∆H (kJmol) ΔS (kJmolK) ΔG (kJmol)Fe-B283 8029 7782 minus0037 8841293 8879303 8916313 8953Al-B

4190 3932 minus0162 8516867888409002

Advances in Materials Science and Engineering 9

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

283 K293 K

303 K313 K

ndash05

00

05

10

15

20

25ln

(qe ndash

qt)

Time (min)0 30 60 90 120 150 180

(a)

283 K293 K

303 K313 K

0

3

6

9

12

tqt (

min

middotgmiddotm

gndash1)

Time (min)0 50 100 150 200 250

(b)

Figure 10 -e pseudo-first-order kinetic model (a) and pseudo-second-order kinetic model (b) of As(V) adsorption by Al-B at differenttemperatures

Table 3 Parameters of pseudo-first-order and pseudo-second-order kinetic model of As(V) adsorption by Fe-B and Al-B at differenttemperatures

Adsorbent T (K) qe (experimental) (mgg)First-order kinetic model Second-order kinetic model

k1 (minminus1) qe (cal) (mgg) R2 k2 (gmgmiddotmin) qe (cal) (mgg) R2

Fe-B

283 1438 0010 1519 0942 035times10minus3 2114 0924293 1442 0013 1244 0977 068times10minus3 1980 0973303 1442 0027 980 0962 420times10minus3 1553 0999313 1444 0021 657 0992 730times10minus3 1497 0998

Al-B

283 1847 16times10minus3 1635 0956 10times10minus3 2222 0984293 2075 19times10minus3 1301 0948 29times10minus3 2222 0998303 2080 70times10minus3 856 0949 42times10minus3 2083 0992313 2105 90times10minus3 709 0752 58times10minus3 2128 0996

ndash8

ndash7

ndash6

ndash5

ln k 2

1T (Kndash1)

FendashB R2 = 0952AlndashB R2 = 0924

00032 00033 00034 00035

(a)

FendashB R2 = 0946AlndashB R2 = 0912

ndash14

ndash13

ndash12

ndash11

ndash10

1T (Kndash1)

ln (k

2T)

00032 00033 00034 00035

(b)

Figure 11 (a) Arrhenius plots and (b) Eyring plots of As(V) adsorption onto Fe-B and Al-B

8 Advances in Materials Science and Engineering

adsorption process is physical or chemical Ramesh et al [5]reported that the activation energy of physisorption wasnormally not more than 42 kJmol Hence the values ofactivation energy were found in this study suggesting thatthe adsorption of As(V) on Fe-B was a chemical adsorption-e smaller Ea for the adsorption of As(V) on Al-B was dueto the formation of weak chemical bond between absorbentand adsorbate According to the literature the rate constantincreased when decreasing the value of activation energy orincreasing the frequency factor A -e calculated A valueswere found to be 18times10minus11 and 80821 for the adsorption ofAs(V) on Fe-B and on Al-B respectively -ese results wereinteresting due to showing ldquothe compensation effectrdquo inheterogeneous adsorption

-e free energy of activation (ΔG) activation enthalpy(ΔH) and activation entropy (ΔS) are listed in Table 4-epositive value of ΔH for both samples confirmed an en-dothermic process -e magnitude and sign of ∆S can givean indication of whether the adsorption reaction is an as-sociative or dissociative mechanism [25] -e high negativevalues of ΔS manifested that the As(V) adsorption processwas an associative mechanism -is was additional evidencefor the analysis of adsorption mechanism as described inSection 321 -e large positive values of ΔG inferred thatthe adsorption reactions required energy to convert thereactants into products [26]

323 Adsorption Isotherms Equilibrium studies were car-ried out to obtain the adsorption capacity of modifiedbentonite at different temperatures Two adsorption iso-therms namely the Langmuir [23] and the Freundlich [23]isotherms were employed to analyze the adsorption data-e linear form of Langmuir isotherm is given by

Ce

qe

Ce

qm+

1KL middot qm

(8)

where qe is the equilibrium adsorption capacity (mgg) Ce isthe equilibrium arsenate concentration in solution (mgL)qm is the monolayer adsorption capacity of the adsorbent(mgg) and KL is the Langmuir constant (Lmg) which isrelated to the energy of adsorption respectively qm and KLcan be computed from the intercept and slope of the linearplot with Ceqe versus Ce

In addition a separation factor RL (also equilibriumparameter) is defined by the following equation

RL 1

1 + KLCi (9)

where Ci (mgL) is the initial dye concentration and KL(Lmg) is the Langmuir constant -e value of RL indicatesthe shape of the isotherms to be either unfavorable (RLgt 1)linear (RL 1) favorable (0ltRLlt 1) or irreversible (RL 0)

-e Freundlich isotherm was applied to the adsorptionon a heterogeneous surface with uniform energy -e linearform of this model can be expressed as follows

ln qe lnKF +1n

middot lnCe (10)

where qe and Ce are the equilibrium adsorption capacity(mgg) and equilibrium concentration in liquid phases (mgL) respectively KF and n are the Freundlich constants whichare related to adsorption capacity and intensity respectively-e linear plot with ln qe versus ln Ce can provide the valuesof KF and n from the slope and intercepts

-e plots for he Langmuir and Freundlich isothermmodels are shown in Figures 12 and 13

As seen from Table 5 the high values of R2 for theLangmuir isotherm model (R2gt 0920) as compared withthose for the Freundlich isotherm model (R2lt 0875) and thevalues of RL in the range 0 and 1 inferred that As(V) ad-sorption onto the modified bentonite was favorable for theLangmuir model Based on the maximum monolayer ad-sorption capacity of the adsorbent qm (mgg) specific area ofmodified bentonite can computed by the following expression

S qAsmaxMAs

middot NA middot σAs (11)

where qAsmax is the Langmuir monolayer adsorption capacityMAs is the molar masse of As NA is Avogadro number andσAs is the surface area of AsO4

3minus (σAs π middot r2 r 17 A)Specific surface area of modified bentonite was calcu-

lated at the temperature of 283K as follows

S(FeminusB) 177675

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

1296m2g

S(AlminusB) 294175

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

2146m2g

(12)

-e effective surface area values of the studied sampleswere less than SBET of Fe-B (14607m2g) and Al-B(17013m2g) indicating that the As(V) absorption ontostudied materials only occurred at the outer surfaces and inthe large pores of bentonite particles

-e maximum As(V) adsorption capacities (qm)computed from the Langmuir model at 303 K were1898mgg for Fe-B and 3571mgg for Al-B As can be seenfrom Table 6 the adsorption capacity for arsenate

Table 4 Activation energy and activation parameters of adsorptionprocess

T (K) Ea (kJmol) ∆H (kJmol) ΔS (kJmolK) ΔG (kJmol)Fe-B283 8029 7782 minus0037 8841293 8879303 8916313 8953Al-B

4190 3932 minus0162 8516867888409002

Advances in Materials Science and Engineering 9

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

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Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

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Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

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Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

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Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

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BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

adsorption process is physical or chemical Ramesh et al [5]reported that the activation energy of physisorption wasnormally not more than 42 kJmol Hence the values ofactivation energy were found in this study suggesting thatthe adsorption of As(V) on Fe-B was a chemical adsorption-e smaller Ea for the adsorption of As(V) on Al-B was dueto the formation of weak chemical bond between absorbentand adsorbate According to the literature the rate constantincreased when decreasing the value of activation energy orincreasing the frequency factor A -e calculated A valueswere found to be 18times10minus11 and 80821 for the adsorption ofAs(V) on Fe-B and on Al-B respectively -ese results wereinteresting due to showing ldquothe compensation effectrdquo inheterogeneous adsorption

-e free energy of activation (ΔG) activation enthalpy(ΔH) and activation entropy (ΔS) are listed in Table 4-epositive value of ΔH for both samples confirmed an en-dothermic process -e magnitude and sign of ∆S can givean indication of whether the adsorption reaction is an as-sociative or dissociative mechanism [25] -e high negativevalues of ΔS manifested that the As(V) adsorption processwas an associative mechanism -is was additional evidencefor the analysis of adsorption mechanism as described inSection 321 -e large positive values of ΔG inferred thatthe adsorption reactions required energy to convert thereactants into products [26]

323 Adsorption Isotherms Equilibrium studies were car-ried out to obtain the adsorption capacity of modifiedbentonite at different temperatures Two adsorption iso-therms namely the Langmuir [23] and the Freundlich [23]isotherms were employed to analyze the adsorption data-e linear form of Langmuir isotherm is given by

Ce

qe

Ce

qm+

1KL middot qm

(8)

where qe is the equilibrium adsorption capacity (mgg) Ce isthe equilibrium arsenate concentration in solution (mgL)qm is the monolayer adsorption capacity of the adsorbent(mgg) and KL is the Langmuir constant (Lmg) which isrelated to the energy of adsorption respectively qm and KLcan be computed from the intercept and slope of the linearplot with Ceqe versus Ce

In addition a separation factor RL (also equilibriumparameter) is defined by the following equation

RL 1

1 + KLCi (9)

where Ci (mgL) is the initial dye concentration and KL(Lmg) is the Langmuir constant -e value of RL indicatesthe shape of the isotherms to be either unfavorable (RLgt 1)linear (RL 1) favorable (0ltRLlt 1) or irreversible (RL 0)

-e Freundlich isotherm was applied to the adsorptionon a heterogeneous surface with uniform energy -e linearform of this model can be expressed as follows

ln qe lnKF +1n

middot lnCe (10)

where qe and Ce are the equilibrium adsorption capacity(mgg) and equilibrium concentration in liquid phases (mgL) respectively KF and n are the Freundlich constants whichare related to adsorption capacity and intensity respectively-e linear plot with ln qe versus ln Ce can provide the valuesof KF and n from the slope and intercepts

-e plots for he Langmuir and Freundlich isothermmodels are shown in Figures 12 and 13

As seen from Table 5 the high values of R2 for theLangmuir isotherm model (R2gt 0920) as compared withthose for the Freundlich isotherm model (R2lt 0875) and thevalues of RL in the range 0 and 1 inferred that As(V) ad-sorption onto the modified bentonite was favorable for theLangmuir model Based on the maximum monolayer ad-sorption capacity of the adsorbent qm (mgg) specific area ofmodified bentonite can computed by the following expression

S qAsmaxMAs

middot NA middot σAs (11)

where qAsmax is the Langmuir monolayer adsorption capacityMAs is the molar masse of As NA is Avogadro number andσAs is the surface area of AsO4

3minus (σAs π middot r2 r 17 A)Specific surface area of modified bentonite was calcu-

lated at the temperature of 283K as follows

S(FeminusB) 177675

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

1296m2g

S(AlminusB) 294175

1113874 1113875 times 603 times 1023 times 314 times(17)2

times 10minus101113872 11138732

2146m2g

(12)

-e effective surface area values of the studied sampleswere less than SBET of Fe-B (14607m2g) and Al-B(17013m2g) indicating that the As(V) absorption ontostudied materials only occurred at the outer surfaces and inthe large pores of bentonite particles

-e maximum As(V) adsorption capacities (qm)computed from the Langmuir model at 303 K were1898mgg for Fe-B and 3571mgg for Al-B As can be seenfrom Table 6 the adsorption capacity for arsenate

Table 4 Activation energy and activation parameters of adsorptionprocess

T (K) Ea (kJmol) ∆H (kJmol) ΔS (kJmolK) ΔG (kJmol)Fe-B283 8029 7782 minus0037 8841293 8879303 8916313 8953Al-B

4190 3932 minus0162 8516867888409002

Advances in Materials Science and Engineering 9

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

283 K293 K303 K

2

1

C eq

e

00 10 20

Ce (mgI)30 40

(a)

25

30

lnq e

ln Ce

283 K293 K303 K

2 3 4

(b)

Figure 12 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Fe-B at several temperatures

283 K293 K303 K

00

04

08

12

16

C eq

e

Ce (mgmiddotLndash1)0 10 20 30 40 50

(a)

283 K293 K303 K

1 2 3 4

30

32

34

36

ln q e

ln Ce

(b)

Figure 13 Plots of Langmuir (a) and Freundlich (b) isotherms in linear form for the adsorption of As(V) onto Al-B at several temperatures

Table 5 -e parameters of isotherm models in linear form for the adsorption of As(V) onto modified bentonite

T (K)Langmuir model Freundlich model

qmax (mgg) KL (Lmg) R2 RL KF (mgg) n R2

Fe-B283 1776 108 0976 0016ndash0053 881 486 0561293 1805 518 0972 0003ndash0011 999 536 0391303 1898 787 0976 0002ndash0007 1069 544 0405Al-B283 2941 032 0984 0046ndash0111 21477 741 0795293 3259 041 0970 0037ndash0090 16912 610 0779303 3571 070 0984 0022ndash0055 14069 529 0875

10 Advances in Materials Science and Engineering

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

adsorption onto studied materials was greater than thosefor other adsorbents reported -erefore the modifiedbentonite showed a good capability for eliminating arse-nate from aqueous solution down to part per billion levelsmaking the present modified bentonite to be used com-mercially in future for adsorbing arsenate from aquaticsources contaminated with arsenic

324 Calculation of 8ermodynamic Parameters Gibbrsquosfree energy (∆Gdeg) entropy change (∆Sdeg) and enthalpychange (∆Hdeg) have been obtained from the following ex-pressions [28]

ΔGdeg minusRT lnKL (13)

where KL is the Langmuir constant

lnKL minusΔGdeg

RT minusΔHdeg

RT+ΔSdegR

(14)

-e values of ∆Hdeg and ∆Sdeg were computed from the slopeand intercept of the plot with ln KL versus 1T in Figure 14-e thermodynamic parameters for the As(V) adsorptionare presented in Table 7

For the both cases the obtained ∆Hdeg values were positivewhich manifested the endothermic nature of arsenate ad-sorption onto modified bentonite -e positive value of ∆Sdegindicated the entropy of the system increased during theadsorption -is result suggested that the arsenate adsorp-tion onto modified bentonite was promoted by entropy thanby enthalpy -e mechanism of the As(V) adsorption ontomodified bentonites might be ion exchange so the largevalue of entropy was corresponded to greater randomness-e values of ∆Gdeg were negative for both samples indicatingthe spontaneous adsorption in the investigated temperaturerange and the decrease of ∆Gdeg values with increasingtemperature inferred that the adsorption became more fa-vorable at higher temperature

33Reusability In the reusability test 05 g of usedmodifiedbentonites saturated with As(V) (initial Al-B or initial Fe-B)was added into thirty milliliters of 001M HCl solution -emixture was shaken at a temperature of 30degC using amagnetic stirrer for 24 h -e solids were centrifuged rinsedfor several times with distilled water dried at 100degC andinvestigated for As(V) adsorption capacity at the first run

Figure 15 represents the reusability of modified ben-tonite -e adsorption capacity of the adsorbents decreased

gradually during the repeated absorptiondesorption oper-ations -e adsorption capacity of Al-B decreased from2105mgg for initial adsorbent to 1466mgg for thirdcycle -e adsorption capacity for Fe-B decreased from1444mgg for initial adsorbent to 998mgg for third cycle

Table 6 Comparison of adsorption capacity with other adsorbents

Adsorbent Arsenate adsorptioncapacity (mgg) References

SMB3 0288 [1]Polymeric AlFe-modifiedmontmorillonite 21233 [5]

Al13-Mont 5008 [10]C-Fe-M 885 [27]Fe-M 1515 [27]Al-B 3571 Present studyFe-B 1898 Present study

00033 00034 0003510

11

12

13

1T (Kndash1)

ln K

L

Fe-B R2 = 0911Al-B R2 = 0940

Figure 14 Plot ln KL versus 1T for the determination of ther-modynamic parameters

Table 7 -ermodynamic parameters for the As(V) adsorptiononto Fe-B and Al-B materials

Adsorbent∆Gdeg (kJmol) ∆Hdeg

(kJmol)∆Sdeg

(kJmolK)283K 293K 303KFe-B minus2659 minus3135 minus3347 7123 0347Al-B minus2376 minus2516 minus2738 2734 0180

1 2 3 4 5 6 7 80

5

10

15

20

Fe-B

3rd

run

Fe-B

2nd

run

Fe-B

1st

run

Initi

al F

e-B

Al-B

3rd

run

Al-B

2nd

run

Al-B

1st

run

Initi

al A

l-B

Sample

Ads

orpt

ion

capa

city

(mg

g)

Figure 15 -e dependence of adsorption capacity through thereuse of adsorbent (Co(As) 2466mgL T 303K m 005 gt 4 h)

Advances in Materials Science and Engineering 11

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

-e adsorption capacity was reduced by 304 for Al-B andby 309 for Fe-B after four uses-e results showed that thepolymeric Al and polymeric Fe bentonite were good reusableadsorbents in removal of arsenate ions from aqueoussolution

4 Conclusions

In this study the polymeric Al- and Fe-modified bentoniteswere applied to remove arsenate ions from aqueous solution-e pseudo-second-order kinetic model fit well with thearsenate adsorption kinetic data for the two modifiedbentonites -e maximum monolayer adsorption capacitiesof As(V) at 303K derived from the Langmuir model were3571mgg for Al-bentonite and 1898mgg for Fe-bentonite which were higher than that compared to otheradsorbents reported previously -e negative values of ∆Gdeg

implied the spontaneity while the positive values of ∆Hdeg and∆Sdeg indicated the endothermic nature and increase in ran-domness of the process taking place respectively -e ac-tivation energies for the Fe-modified bentonite and Al-modified bentonite were found to be 8029 and 4190 kJmol respectively -e modified bentonites can be regen-erated and used effectively after four uses for adsorbingarsenate from aqueous solution

Data Availability

-e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

-e authors declare that they have no conflicts of interest

References

[1] J Su H-G Huang X-Y Jin X-Q Lu and Z-L ChenldquoSynthesis characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) fromaqueous solutionrdquo Journal of Hazardous Materials vol 185no 1 pp 63ndash70 2011

[2] Y Salameh N Al-Lagtah M N M Ahmad S J Allen andG M Walker ldquoKinetic and thermodynamic investigations onarsenic adsorption onto dolomitic sorbentsrdquo Chemical En-gineering Journal vol 160 no 2 pp 440ndash446 2010

[3] K C M Kwok L F Koong T Al Ansari and G McKayldquoAdsorptiondesorption of arsenite and arsenate on chitosanand nanochitosanrdquo Environmental Science and PollutionResearch vol 25 no 15 pp 14734ndash14742 2018

[4] P Chutia S Kato T Kojima and S Satokawa ldquoArsenicadsorption from aqueous solution on synthetic zeolitesrdquoJournal of Hazardous Materials vol 162 no 1 pp 440ndash4472009

[5] A Ramesh H Hasegawa T Maki and K Ueda ldquoAdsorptionof inorganic and organic arsenic from aqueous solutions bypolymeric AlFe modified montmorilloniterdquo Separation andPurification Technology vol 56 no 1 pp 90ndash100 2007

[6] C Luengo V Puccia and M Avena ldquoArsenate adsorptionand desorption kinetics on a Fe(III)-modified montmoril-loniterdquo Journal of Hazardous Materials vol 186 no 2-3pp 1713ndash1719 2011

[7] D Borah S Satokawa S Kato and T Kojima ldquoSorption ofAs(V) from aqueous solution using acid modified carbonblackrdquo Journal of Hazardous Materials vol 162 no 2-3pp 1269ndash1277 2009

[8] M Jang S-H Min T-H Kim and J K Park ldquoRemoval ofarsenite and arsenate using hydrous ferric oxide incorporatedinto naturally occurring porous diatomiterdquo EnvironmentalScience amp Technology vol 40 no 5 pp 1636ndash1643 2006

[9] S Bang G Korfiatis and X Meng ldquoRemoval of arsenic fromwater by zero-valent ironrdquo Journal of Hazardous Materialsvol 121 no 1ndash3 pp 61ndash67 2005

[10] S Zhao C Feng X Huang B Li J Niu and Z Shen ldquoRole ofuniform pore structure and high positive charges in the ar-senate adsorption performance of Al13-modified montmo-rilloniterdquo Journal of Hazardous Materials vol 203-204pp 317ndash325 2012

[11] Z Qin P Yuan J Zhu H He D Liu and S Yang ldquoInfluencesof thermal pretreatment temperature and solvent on theorganosilane modification of Al13-intercalatedAl-pillaredmontmorilloniterdquo Applied Clay Science vol 50 no 4pp 546ndash553 2010

[12] L Borgnino M J Avena and C P De Pauli ldquoSynthesis andcharacterization of Fe(III)-montmorillonites for phosphateadsorptionrdquo Colloids and Surfaces A Physicochemical andEngineering Aspects vol 341 no 1-3 pp 46ndash52 2009

[13] Y-F Hao L-G Yan H-Q Yu et al ldquoComparative study onadsorption of basic and acid dyes by hydroxy-aluminumpillared bentoniterdquo Journal of Molecular Liquids vol 199pp 202ndash207 2014

[14] F Bertella and S B C Pergher ldquoPillaring of bentonite claywith Al and Cordquo Microporous and Mesoporous Materialsvol 201 pp 116ndash123 2015

[15] M Altunlu and S Yapar ldquoEffect of OHminusAl3+ and Al3+clayratios on the adsorption properties of Al-pillared bentonitesrdquoColloids and Surfaces A Physicochemical and EngineeringAspects vol 306 no 1ndash3 pp 88ndash94 2007

[16] R L Frost and J T Kloprogge ldquoVibrational spectroscopy offerruginous smectite and nontroniterdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 56no 11 pp 2177ndash2189 2000

[17] W Xue H He J Zhu and P Yuan ldquoFTIR investigation ofCTAB-Al-montmorillonite complexesrdquo Spectrochimica ActaPart A Molecular and Biomolecular Spectroscopy vol 67no 3-4 pp 1030ndash1036 2007

[18] B A Goodman J D Russell and A R Frasera ldquoAMOssbauer and IR Spectroscopic study of the structure ofnontroniterdquoClays and ClayMinerals vol 24 no 2 pp 53ndash591976

[19] J D Russel and A R Fraser ldquoInfrared methodsrdquo in ClayMineralogy Spectroscopic and Chemical DeterminativeMethods M J Wilson Ed pp 11ndash67 Chapman amp HallLondon UK 1994

[20] M E R J Jalil R S Vieira D Azevedo M Baschini andK Sapag ldquoImprovement in the adsorption of thiabendazoleby using aluminum pillared claysrdquo Applied Clay Sciencevol 71 pp 55ndash63 2013

[21] H Faghihian and M H Mohammadi ldquoSurface properties ofpillared acid-activated bentonite as catalyst for selectiveproduction of linear alkylbenzenerdquo Applied Surface Sciencevol 264 pp 492ndash499 2013

[22] H Khalaf O Bouras and V Perrichon ldquoSynthesis andcharacterization of Al-pillared and cationic surfactant mod-ified Al-pillared Algerian bentoniterdquo Microporous Materialsvol 8 no 3-4 pp 141ndash150 1997

12 Advances in Materials Science and Engineering

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

[23] M E Pena G P Korfiatis M Patel L Lippincott andXMeng ldquoAdsorption of As(V) and As(III) by nanocrystallinetitanium dioxiderdquo Water Research vol 39 no 11pp 2327ndash2337 2005

[24] M Toor and B Jin ldquoAdsorption characteristics isothermkinetics and diffusion of modified natural bentonite for re-moving diazo dyerdquo Chemical Engineering Journal vol 187pp 79ndash88 2012

[25] K A Krishnan and T S Anirudhan ldquoUptake of heavy metalsin batch systems by sulfurized steam activated carbon pre-pared from sugarcane bagasse pithrdquo Industrial amp EngineeringChemistry Research vol 41 no 20 pp 5085ndash5093 2002

[26] H T M -anh T T T Phuong P L T Hang T T T ToanT X Mau and D Q Khieu ldquoComparative study of Pb(II)adsorption onto MILndash101 and FendashMILndash101 from aqueoussolutionsrdquo Journal of Environmental Chemical Engineeringvol 6 no 4 pp 4093ndash4102 2018

[27] X Ren Z Zhang H Luo et al ldquoAdsorption of arsenic onmodified montmorilloniterdquo Applied Clay Science vol 97-98pp 17ndash23 2014

[28] A Ozcan Ccedil Omeroglu Y Erdogan and A S OzcanldquoModification of bentonite with a cationic surfactant anadsorption study of textile dye Reactive Blue 19rdquo Journal ofHazardous Materials vol 140 no 1-2 pp 173ndash179 2007

Advances in Materials Science and Engineering 13

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom