Arsenic removal using bagasse fly ash-iron coated and sponge iron char

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Journal of Environmental Chemical Engineering xxx (2014) xxx–xxx

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JECE 380 1–7

Arsenic removal using bagasse fly ash-iron coated and sponge iron char

Lallan Singh Yadav a, Bijay Kumar Mishra a, Arvind Kumar b,*, Kakoli Karar Paul c

a School of Chemistry, Centre of Studies in Surface Science and Technology, Sambalpur University, Jyoti Vihar, Orissa 768019, IndiabDepartment of Chemical Engineering, National Institute of Technology, Rourkela, Orissa 769008, IndiacDepartment of Civil Engineering, National Institute of Technology, Rourkela, Orissa 769008, India

A R T I C L E I N F O

Article history:Received 20 January 2014Accepted 23 June 2014

Keywords:ArsenicRemovalKineticIsotherm

A B S T R A C T

The present work reports the adsorption capacity of bagasse fly ash-iron coated (BFA-IC) and sponge ironchar (SIC) for arsenic removal. Different kinetic models were used to the kinetic data amongst whichpseudo-second order model was best fitted. Batch equilibrium adsorption was carried out to determinethe adsorption capacity of the BFA-IC and SIC. The adsorption data were fitted to the Langmuir,Freundlich, Tempkin and Redlich–Petersion isotherm adsorption model. The maximum adsorptioncapacity (qm) of both BFA-IC and SIC were also determined. The maximum uptake capacity (qm) of BFA-ICand SIC for As(III) was 39.53 and 27.85 mg/g, respectively, and for As(V) was only 25.82 and 28.58 mg/g,respectively. The surface area of the BFA-IC and SIC was determined to be 168 and 78.63 m2/g,respectively, using BET method. The zero point charge was determined using solid addition method. Inthe present work, it is found that the after substantial chemical modification of BFA and SIC havepotentials to be used as low cost adsorbents for arsenic removal from waste water.

ã 2014 Published by Elsevier Ltd.

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Journal of Environmental Chemical Engineering

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Introduction

Arsenicisawellknownelementfor itsnotoriety indrinkingwaterand giving several adverse impacts on health, and causing severaldiseases if its concentration is having more than 100 mg/l in drinkingwater [1]. Due to this reason, several agencies of the world have setthe limit of arsenic in various water bodies. World HealthOrganization (WHO) in 1993 and National Health and MedicalResearch Committee(NHMRC),Australia, in 1996had recommendedmaximum contaminant level (MCL)of arsenic indrinkingwateras 10and 7 mg/l, respectively [2,3]. The MCL of arsenic in drinking waterhas also been reduced from 50 to 10 mg/l by European Commission in2003 [4]. Environmental Protection Agency (EPA), USA, has decidedto move forward in implementing the same MCL of arsenic that isrecommended by WHO for drinking water in 1993. Japan and Canadahave reduced the MCL for arsenic in drinking water to 10 and 25mg/l,respectively [5]. The MCL for arsenic in countries like India,Bangladesh, Taiwan, China, Vietnam, etc. is also 50 mg/l. About40–60% of the people in Bangladesh have been estimated to beadversely affected by arsenic-contaminated drinking water. As aresult, the arsenic contamination of drinking water continues to be aproblem, with increasingly stringent standards making it more andmore important to find new technologies [6].

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54* Corresponding author. Tel.: +91 6612462268.E-mail address: [email protected] (A. Kumar).

http://dx.doi.org/10.1016/j.jece.2014.06.0192213-3437/ã 2014 Published by Elsevier Ltd.

Please cite this article in press as: L.S. Yadav, et al., Arsenic removal usingEng. (2014), http://dx.doi.org/10.1016/j.jece.2014.06.019

Literature revealed that oxidation and filtration, biologicaloxidation followed by removal for iron and manganese oxides, co-precipitation followed by coagulation, sedimentation and filtra-tion, ion exchange through suitable cation and anion exchangeresins, adsorption and membrane technology including reverseosmosis, nanofiltration and electrodialysis are the availabletechnologies for arsenic removal [7,8]. Among various treatmenttechnologies, adsorption is the most popular physico-chemicaltreatment process due to high removal efficiency, easy operation,low cost and sludge-free operation for the removal of organicpollutants/toxic metals from wastewaters. A number of non-conventional, low cost adsorbents have been tried for arsenicremoval [9]. Use of surface modified low cost adsorbents can be aviable option for arsenic removal from aqueous effluents. This hasled to a search for cheaper alternative materials as adsorbents suchas lignin, bagasse pith; saw dust, coal and bagasse fly ash, rice huskash, sponge iron char and other, etc. After modifying their surfaces,these materials have good potential for removing arsenic fromwastewaters.

The purpose of the present study is, therefore, to study theprocess of adsorption of arsenic onto indigenously prepared low-cost surface modified adsorbents from industrial waste such asbagasse fly ash (BFA) and sponge iron char (SIC), and to researchthe possibility of using them as low-cost adsorbents. Thisinvestigation also examines the influence of various processparameters for their optimal performance such as effect ofadsorbent dosage (w), pH, contact time (t) and initial concentration

bagasse fly ash-iron coated and sponge iron char, J. Environ. Chem.

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http://dx.doi.org/10.1016/j.jece.2014.06.019



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55 (C56 ad57 m

58 M

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74 1075 prQ276 sO77 Ar78 pr79 (C80 ex81 w

82 Ba

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85 tig86 a t87 sp88 w89 ga90 re91 ca

%

qt

92 w93 of94 co95 ad96 of97 w98 Si99 an

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Adsorbent dosage (g/l)

As(III )-(BFA-IC)As(V)-(BFA-IC)As(III )-SICAs(V)-SIC

Fig. 1. Variation of adsorbent dose on the removal of arsenic. pH natural, t = 6 h,T = ambient temperature, and C0 = 100 mg/l.

2 L.S. Yadav et al. / Journal of Environmental Chemical Engineering xxx (2014) xxx–xxx

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0) at ambient temperature. The adsorption capacity of bothsorbents BFA-IC and SIC were estimated using the Langmuirodel.

aterial and method

sorbent and its preparations

BFA (ash from bio fuel producer) and SIC (sponge iron industryaste) were obtained locally in the vicinity of Rourkela, Orissaashed with hot water (70 �C) and dried. Amount of iron content inAwas checked by soaking 1 g of BFA in 10 ml 65% nitric acid for 24 h

room temperature so as to dissolve the Fe from BFA. Ironncentration in the filtered solution was determined using atomicsorption spectrophotometer (AAS) [10]. No iron was detected ine BFA using this procedure. BFA (granular size 150 mm) was treatedith 2 M FeCl3 solution, the solution was decanted and dried at5 �C for 12 h and then used as an adsorbent. SIC, obtained fromonge iron industry was shredded using ball mill and sieved fortaining the particular granular size of 110 mm, and then used.

sorbate

All the chemicals used were of analytical reagent grade. A00 mg/l As(III) and As(V) individual stock solution wereepared by dissolving 0.1734 g NaAsO2 and 0.416 g Na2HA-4�7H2O in 1000 ml of double distilled water (DDW), respectively.senic bearing water was further diluted using DDW toepare the stock solution of 1000 mg/l. The initial concentration0 = 50–150 mg/l) was ascertained before the start of eachperimental run. pH of the different concentration solutionsere adjusted using 1 M HCl and/or NaOH.

tch experimental program

For each experiment, 50 ml of arsenic solution of known C0 andknown amount of the each adsorbent was taken in a 100 ml air-ht conical flask with a glass stopper. This mixture was agitated inemperature-controlled shaking water bath at a constant shakingeed of 250 rpm. After predetermined time of shaking, adsorbentas separated from the adsorbent–solution mixture by centrifu-tion of the slurry at 10,000 rpm for 5 min [11]. The percentmoval and uptake qt (mg/g) of arsenic at any time, t waslculated as:

R ¼ C0 � Ct

C0

� �� 100 (1)

¼ C0 � Ct

w

� �V (2)

here C0 is the initial arsenic concentration (mg/l), V is the volume the wastewaters in the flask (l), Ct is the adsorbate (arsenic)ncentration (mg/l) after time t, and w is the mass of thesorbent (g) used in the experiment. Reported results are average

two replicates. In study of each parameter, control experimentsere carried out without adsorbents (and with adsorbates only).milarly, experiments were also carried out with distilled waterd the adsorbents so as to check leaching of arsenic from thesorbents.

alytical measurements

The arsenic concentrations in the solutions were measured byDC (silver diethyldithiocarbamate) method having detectionit 1 mg/l [12].

Please cite this article in press as: L.S. Yadav, et al., Arsenic removal usinEng. (2014), http://dx.doi.org/10.1016/j.jece.2014.06.019

Error analysis

Marquardt’s percent standard deviation (MPSD) error function[13] was also employed in this study to find out the most suitablekinetic and isotherm model to represent the experimental data.MPSD error function is given as:

MPSD ¼ 100

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi1

n � p

Xni¼1

jqe;exp � qe;calqe;exp

jvuut

2

i

(3)

Adsorbent characterization

The Brunauer–Emmett–Teller (BET) method was used todetermine surface area for BFA-IC and SIC. The zero point charge(ZPC) of the materials is a tool to determine the surface charge,which is normally determined by potentiometric mass titrationmethod. PZC was determined by salt addition method.

Result and discussion

Adsorption study

Effect of adsorbent dosageTo optimize the minimum dosage required for bringing down

the arsenic level to the tolerance limit, a dosage of adsorbent(0.4–10 g/l) was varied. The percentage removal of arsenic withdifferent adsorbent dosage is shown in Fig. 1. The BFA-IC and SICwere found to be efficient for the removal of arsenic from 100 to2 mg/l and 0.5 mg/l, respectively, with 6 g/l dosage. The percentageremoval of arsenic significantly increased with sorbent dosage,which was obvious because of the increase in the number of activesites as the dosage increases [14]. Hence, in all the subsequentexperiments, 6 g/l of adsorbent was fixed as the optimum dosage togive reasonable dearsenification efficiency.

Effect of contact timeAs shown in Fig. 2, the effect of contact time between adsorbate

and sorbent on the sorption capacity of arsenic, it is followed thatthe adsorption of arsenic took place within 100 min. Subsequently,adsorption became slow and almost reached to equilibrium within180 min. With further increase in contact time up to 6 h, noappreciable removal of arsenic takes place, indicating thatcomplete adsorption occurred within 3 h. Therefore, t = 3 h istaken as equilibrium time for arsenic sorption. Thus, subsequentadsorption experiments were conducted for a period of 3 h.

g bagasse fly ash-iron coated and sponge iron char, J. Environ. Chem.


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As(III )-(B FA-IC)As(V)-(BFA-IC)

As(III )-SIC

As(V)-SIC

Fig. 4. Effect of pH on the percentage adsorption of arsenic. pH natural, w = 6 g/l,t = 3 h, T = ambient temperature, C0 = 100 mg/l.

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Fig. 2. Effect of contact time on arsenic adsorption. pH natural, t = 6 h, T = ambienttemperature, w = 6 g/l, and C0 = 100 mg/l.

L.S. Yadav et al. / Journal of Environmental Chemical Engineering xxx (2014) xxx–xxx 3

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Effect of initial concentrationFor the initial concentration of arsenic solutions up to 150 mg/l

and adsorbent dosage 6 g/l, more than 22% removal was observedwithin 3 h contact time. It was evident that at low initialconcentrations of arsenic, the adsorption was very fast. Theremoval of arsenic decreased with increase in initial concentrationand took longer time for 100% removal. With increase in arsenicconcentration, competition for the active adsorption sites in-creased and the adsorption process was gradually slowed down.The percentage of arsenic removal versus initial concentration isshown in Fig. 3.

Effect of pHThe effect of pH on the removal efficiency of sorbent was

studied with varying pH from 2 to 12 keeping all other parametersfixed as shown in Fig. 4. The As(III) removal onto BFA-IC was foundmore than 90% at pH 7. The arsenic removal onto SIC and As(V) ontoBFA-IC were found to be maximum at pH 12. These results clearlyshow that removal percentage of arsenic was higher in basic pHcompared to acidic one in contrast to As(III) onto BFA-IC. Thevariation in uptake with respect to the initial solution pH can beexplained on the basis of PZC of the adsorbent and complexformation between iron and arsenic.

Adsorption kinetics

The rate of adsorption was determined by studying theadsorption kinetics at three different initial arsenic concentrations

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Ini�a l concentra�on (m g/l)

As(III)-(BFA-IC)As(V)-(BFA-IC)As(III)-SICAs(V)-SIC

Fig. 3. Effect of initial arsenic concentration on adsorption efficiency. pH natural,w = 6 g/l, t = 3 h, T = ambient temperature, and C0 = 10–150 mg/l.


of 50, 100 and 150 mg/l at optimum adsorbent dose of 6 g/l. It wasnoticed that arsenic removal increased with the lapse of time andthe rate was initially fast, after which the rate reduced as theequilibrium approached. For evaluating, the adsorption kinetic twomodels are employed, the pseudo-first order [15] and the pseudo-second order models [16]. The pseudo-first order kinetic equationis expressed into linearized form as follows:

qt ¼ qe � exp ðln qe � kf tÞ (6)

where kf (min�1) is the rate constant of pseudo-first orderadsorption, qe and qt (mg/g) are the adsorbed amount atequilibrium and at time t, respectively.

The pseudo-second order model can be represented as givenbelow:

qt ¼ksq2et

1 þ ksqet(8)

The initial sorption rate, h (mg/g min) at t = 0 is defined as:

h ¼ ksq2e (9)

where ks is the pseudo-second order rate constant (g/mg/min). h, qeand ks can be determined from the non-linear regression of pseudo-second order equation with the experimental data using theMicrosoft Excel spread sheet for Windows. The best-fit values of h,qe and ks along with the correlation coefficients for the pseudo-firstorder and pseudo-second order models are shown in Table 1.

Table 1 shows that the experimental adsorption data fittedalmost equally well to the pseudo-first and pseudo-second orderkinetic models. Similar fact was also observed in the study ofbenzoic acid onto high specific area activated carbon cloth [17].However, in such a case, it is very difficult to decide which modelrepresents the experimental data best just on the basis ofregression coefficients. A better criterion is to evaluate theapplicability of each kinetic model for which the values of theerror functions MPSD was calculated. The higher the value of R2

and the lower the value of error function, the better will be thegoodness of fit [18]. Table 1 shows that the pseudo-second orderkinetic model best-fits to the experimental data. Therefore, thesorption kinetics can be represented by the pseudo-second orderkinetic model for the adsorption of arsenic onto BFA-IC and SIC. Thenon-linear plot of pseudo-second order for sorption of arsenic ontoadsorbents (BFA-IC and SIC) is presented through Figs. 5 and 6.

Adsorption isotherms

The adsorption isotherms are generally used to describe howadsorbate interacts with adsorbent at equilibrium and therefore it



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Table 1Pseudo-first order and pseudo-second order kinetic parameters for three different initial arsenic concentrations (C0).

C0 (mg/l) Pseudo-first order kinetic model Pseudo-second order kinetic model

qe,exp qe,cal kf R2 (non-linear) MPSD h qe,cal ks R2 (non-linear) MPSD

As(III)–(BFA-IC) 50 8.167 7.045 0.0382 0.9083 12.629 0.365 8.359 0.0052 0.9718 7.617100 15.167 15.153 0.0228 0.9949 6.578 0.456 18.606 0.0013 0.9971 4.017150 21.667 22.356 0.0193 0.9838 11.613 0.516 28.252 0.0006 0.9790 14.925

As(V)–(BFA-IC) 50 8.632 7.608 0.0714 0.9184 7.594 0.788 8.667 0.0105 0.9938 1.640100 16.00 14.597 0.0302 0.9526 13.773 0.644 17.349 0.0021 0.9746 10.089150 23.33 22.378 0.0223 0.9893 5.812 0.572 29.938 0.0006 0.9992 1.743

As(III)–SIC 50 8.167 8.171 0.0631 0.9597 4.386 0.7522 8.979 0.0093 0.9129 7.680100 16.330 16.211 0.0384 0.9855 7.116 1.0145 18.422 0.0030 0.9822 5.109150 23.667 23.243 0.0284 0.9901 5.806 0.7761 29.329 0.0009 0.9969 3.203

As(V)–SIC 50 8.169 8.165 0.0835 0.9517 3.654 1.225 8.647 0.0164 0.9373 4.7359100 16.550 15.992 0.0649 0.9429 7.007 1.556 17.497 0.0051 0.9735 5.5061150 23.00 23.223 0.0258 0.9614 19.920 0.618 28.998 0.0007 0.9565 16.168


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critical in optimizing the use of adsorbents. Four differenttherms have been adopted to understand the mechanism ofsorption for the removal of arsenic. Theoretical plots of eachtherm were tested for their correlation with the experimentalsults. Figs. 7 and 8 show the comparison of different isothermsudied at ambient temperature.

ngmuir isothermThe Langmuir adsorption isotherm is given by [19]:

¼ qmKLCe

1 þ KLCe(10)

here qe is the equilibrium quantity adsorbed (mg/g), qm is theaximum capacity of monomer adsorption (mg/g), Ce is theuilibrium concentration (mg/g), KL is the adsorption equilibriumnstant (l/mg) related to the energy of adsorption. The Langmuiruation is valid for homogeneous surface [20]. The experimentalsorption data and the values of the isotherm parameterslculated non-linearly are given in Table 2.

(a) As(III)–(BFA-IC)

0

5

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25

0 50 100 150 200Time (min)

150 µg/l 100 µg/l 50 µg/l

Fig. 5. Pseudo-second order adsorption kinetic model for (a) As(III)–(BFA-IC) an


Freundlich isothermThe Freundlich isotherm is employed to model the multilayer

adsorption based on sorption onto heterogeneous surface [21] andis given by:

qe ¼ KF C1=ne (11)

where KF (mg1�1/n l1/n/g) is Freundlich constant indicative of therelative adsorption capacity of the adsorbent and n is the empiricalparameter representing adsorption intensity of the adsorbent. Thevalues of KF and n calculated non-linearly are given in Table 2. Themagnitude of the exponent n gives an indication on the favorabilityof arsenic adsorption [22]. The conditions are found to be favorableas the value of 1/n lies between 0 and 1 and the value of ‘n’ isgreater than 1. A plot of the experimental data and non-linear formis shown.

Temkin isothermThe Temkin isotherm model assumes that the adsorption

energy decreases linearly with the surface coverage due to

(b) As(V)–(BFA-IC)

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150 µg/l100 µg/l50 µg/l

d (b) As(V)–(BFA-IC) adsorption systems. pH 8, T = 303 K, t = 3 h, and w = 6 g/l.



Fig. 8. Equilibrium isotherms for (a) As(III)–SIC and (b) As(V)–SIC adsorption systems.

As(V)–SIC(b)As(III)–SIC(a)

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0 50 10 0 15 0 20 0Time (min)

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Fig. 6. Pseudo-second order adsorption kinetic model for (a) As(III)–SIC and (b) As(V)–SIC adsorption systems. pH 12, T = 303 K, t = 3 h, and w = 6 g/l.

Fig. 7. Equilibrium isotherm for (a) As(III)–(BFA-IC) and As(V)–(BFA-IC) adsorption systems.


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Please cite this article in press as: L.S. Yadav, et al., Arsenic removal using bagasse fly ash-iron coated and sponge iron char, J. Environ. Chem.Eng. (2014), http://dx.doi.org/10.1016/j.jece.2014.06.019


235 ad236 so237 eq

qe238 wQ4239 Te240 (k241 va242 th

243 Re244

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qe

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Table 2Characteristic parameters of different isotherm models for the adsorption of arsenic.

Isotherm As(III)–(BFA-IC) As(V)–(BFA-IC)

Freundlich KF 1/n R2 MPSD KF 1/n R2 MPSD2.7656 0.6582 0.9871 5.00 6.7170 0.3843 0.9922 11.9629

Langmuir qm KL R2 MPSD qm KL R2 MPSD39.8336 0.0491 0.9828 7.41 25.8287 0.2045 0.9816 4.0203

Temkin KT BT R2 MPSD KT BT R2 MPSD0.4677 8.7212 0.9949 3.93 2.5873 5.1897 0.9699 8.4885

Redlich–Peterson KR aR b R2 MPSD KR aR b R2 MPSD1.9833 0.0689 0.8894 0.9716 5.4339 1.29 0.099 0.889 0.7784 8.6734

Isotherm As(III)–SIC As(V)–SIC

Freundlich KF 1/n R2 MPSD KF 1/n R2 MPSD5.6199 0.4257 0.9796 6.6462 7.8958 0.4173 0.9933 3.9084

Langmuir qm KL R2 MPSD qm KL R2 MPSD27.8532 0.1317 0.9562 13.9174 28.5857 0.2742 0.9753 12.0349

Temkin KT BT R2 MPSD KT BT R2 MPSD1.6304 5.6383 0.9464 11.7971 3.3070 5.8306 0.9671 9.3040

Redlich–Peterson KR aR b R2 MPSD KR aR b R2 MPSD14.184 1.7203 0.6854 0.9849 8.0097 121.4294 14.417 0.6045 0.9961 4.1870


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sorbent–adsorbate interactions indicating falling in the heat ofrption is linear rather than logarithmic [23]. The Temkinuation is given as:

¼ BT ln KT þ BT ln Ce (12)

here KT is the equilibrium binding constant (l/mg) and BT is themkin constant related to the variation of adsorption energyJ/mol) [24]. Values of KT and BT are presented in Table 2. Theriation of adsorption energy shows a positive value indicatingat the reaction is exothermic in nature [25].

dlich–Peterson isothermThe Redlich–Peterson isotherm contains three parameters anda special case model that incorporated the features of thengmuir and Freundlich isotherms into a single equation andesents general isotherms equation [26]. It can be described asllows:

¼ KRCe

1 þ aRCbe

(13)

here KR is the Redlich–Peterson constant (l/g), aR is the affinityefficient (l/mg As), b (0 < b < 1) is the heterogeneity coefficient,is the uptake at equilibrium (mg/l As), and Ce is the equilibriumncentration (mg/l As). The calculated b value in Table 2 indicatese heterogeneity surface of the adsorbents. This is also supported

R2 value.

oosing best isotherm model

Since error function produces a different set of isothermrameters, an overall optimum parameter set is difficult toentify directly. Thus, a normalization of each parameter isployed in order to have a better comparison between therameter set for the single isotherm model [27]. In thermalization process, MPSD error function was used and thesults for each parameter set were determined. Secondly, therors determined for a given error function was divided by theaximum error to obtain the normalized errors for each


parameter set. Lastly, the normalized error for each parameterset was summed up.

Langmuir, Freundlich, Temkin, and Redlich–Peterson isothermconstants were determined from the plots of 1/qe versus 1/Ce; ln qeversus ln Ce, qe versus ln Ce, and ln (KRCe/qe� 1) versus ln Ce,respectively, at 303 K using MS Excel for Windows. The isothermconstants and R2 values for all the isotherms studied are presentedin Table 2.

Comparison of R2 values for various isotherms for As(V)–BFAIC,As(III)–SIC, As(V)–SIC and As(III)–BFAIC systems show that thesevalues are closer to unity for Freundlich and Temkin isotherms. Bycomparing the results of the values for the error function MPSD(Table 2), it can be concluded that the Freundlich and Temkinisotherms generally best represent the equilibrium data of arsenic[27]. Comparable fit of various isotherm models for the adsorptionof arsenic onto BFAIC and SIC at ambient temperature have beenshown through Figs. 7 and 8. The adsorption process showed goodagreement with the Temkin and Freundlich isotherm for As(III) andAs(V) onto BFA-IC, respectively; Freundlich and Redlich–Petersonisotherm for As(III) and As(V) onto SIC, respectively. The adsorbentcapacity of the adsorbents used in the present study is comparedwith other low cost adsorbents reported in the literature [9]. It maybe seen that adsorbent capacity of the BFA-IC and SIC is better thansome adsorbents and lower than few other adsorbent. It may bedue to the difference in textural and other physico-chemicalcharacteristics of the adsorbents.

Characterization of adsorbents

The surface area of BFA-IC and SIC were determined by applyingisothermal BET. This methodology employs nitrogen adsorption atdifferent pressures at 77 K. The surface area determined for BETwas 168 m2/g for BFA-IC, while for SIC, it was 78.63 m2/g. Thecombined influence of all the functional groups of BFA-IC and SICwere determined using pHpzc. The zero point charge of anymaterials describes the condition when the electrical chargedensity on a surface is zero [28]. The point of zero charge (pHpzc)was determined as per the method presented by Faria et al. [29]. Inthe present study, pHpzc for BFA-IC was obtained 7 and 10 for SIC.



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321

322

323

324 Q6325

326

327

328

329330

331

332333

334

335336337338

339

340341

342343344

345346

347348

349350

351352

353

354355

356

357

358359

360361

362363

364365366

367368

369

370371

372373

374

375

376377378

Q7379

380381


G Model

JECE 380 1–7

Conclusions

Bagasse fly ash-iron coated (BFA-IC) and sponge iron char (SIC)were prepared in the present work and were further used for theirsuitability in the removal of both As(III) and As(V) by equilibriumand dynamic conditions at different pH. Pseudo-first order andsecond order kinetic models were used for their efficacy inrepresenting the kinetic data. Pseudo-second order model wasfound to best represent the kinetic data. The equilibrium data werefitted to Langmuir, Freundlich, Temkin and Redlich–Petersonisotherm adsorption models, and the various model parameterswere evaluated. The monolayer adsorption capacity from theLangmuir model for BFA-IC (25.82 mg/g for As(V) and 39.83 mg/gfor As(III)) and for SIC (28.58 mg/g for As(V); 27.85 mg/g for As(III)).The adsorption process showed good agreement with the Temkinand Freundlich isotherm for As(III) and As(V) onto BFA-IC,respectively; Freundlich and Redlich–Peterson isotherm for As(III) and As(V) onto SIC, respectively. The positive variation ofadsorption energy determined from Temkin isotherm for arseniconto BFA-IC and SIC showed that the reaction is exothermic innature indicating that the adsorption process was favorable andspontaneous in nature.

Acknowledgements

Arvind Kumar is thankful to Council of Scientific and IndustrialResearch (Scheme 24(306)09-EMR-II) for financial support to carryout this work. Lallan Singh Yadav is thankful to CSIR for seniorresearch fellowship.

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Arsenic removal using bagasse fly ash-iron coated and sponge iron char