Bioresource Technology 100 (2009) 634–637

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Bioresource Technology

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Biosorptive removal of arsenic from drinking water

Piyush Kant Pandey a,*, Shweta Choubey a, Yashu Verma a, Madhurima Pandey a, K. Chandrashekhar b

a Centre for Environmental Science and Engineering, Department of Engineering Chemistry, Bhilai Institute of Technology, Durg 491002, CG, Indiab Analytical Chemistry Group, Defence Metallurgical Research Laboratory (DMRL), Hyderabad 500058, AP, India

a r t i c l e i n f o

Article history:Received 16 May 2007Received in revised form 8 July 2008Accepted 12 July 2008Available online 21 September 2008

Keywords:ArsenicAdsorptionBiomassMomordica charantia

0960-8524/$ - see front matter � 2008 Elsevier Ltd. Adoi:10.1016/j.biortech.2008.07.063

* Corresponding author. Tel.: +91 94252 45309; faxE-mail address: drpiyush_pandey@yahoo.com (P.K

a b s t r a c t

A biomass derived from the plant Momordica charantia has been found to be very efficient in arsenic(III)adsorption. An attempt was made to use this biomass for arsenic(III) removal under different conditions.The parameters optimized were contact time (5–150 min), pH (2–11), concentration of adsorbent (1–50 g/l), concentration of adsorbate (0.1–100 mg/l), etc. It was observed that the pH had a strong effecton biosorption capacity. The optimum pH obtained for arsenic adsorption was 9. The influence of com-mon ions such as Ca2+, Mg2+, Cd2+, Se4+, Cl�, SO2�

4 , and HCO�3 , at concentrations varying from 5 to1000 mg/l was investigated. To establish the most appropriate correlation for the equilibrium curves, iso-therm studies were performed for As(III) ion using Freundlich and Langmuir adsorption isotherms. Thepattern of adsorption fitted well with both models. The biomass of M. charantia was found to be effectivefor the removal of As(III) with 88% sorption efficiency at a concentration of 0.5 mg/l of As(III) solution, andthus uptake capacity is 0.88 mg As(III)/gm of biomass. It appears that this biomass should be used as apalliative food item. Further it also appears that the dietary habits may play a role in the toxic effectsof ingested arsenic.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

Arsenic is highly toxic and has historically been used as a poi-son. Acute poisoning has a mortality rate of 50–75%, and deathusually occurs within 48 h. The arsenic contamination has beenacknowledged as a ‘‘major public health issue” (WHO, 1999). Ar-senic is classified as a group A and category 1 human carcinogenby the US Environmental Protection Agency (US EPA, 1997) andthe International Association For Research on Cancer (IARC,2004), respectively. The WHO provisional guideline of 10 ppb(0.01 mg/l) has been adopted as the drinking water standard. How-ever, many countries have retained the earlier WHO guideline of50 ppb (0.05 mg/l) as their standard or as an interim target includ-ing Bangladesh and China. In 2001, US EPA published a new 10 ppb(0.01 mg/l) standard for arsenic in drinking water, requiring publicwater supplies to reduce arsenic from 50 ppb (0.05 mg/l).

Pandey et al. (1999, 2000, 2001) first reported arsenic contam-ination and human affliction at places far away from the BengalDelta Plains in erstwhile Madhya Pradesh. The majority of arsenicin natural water is a mixture of arsenate and arsenite, with arse-nate usually predominating. High concentration of arsenic ingroundwater has been reported from the Bengal Delta Plains inWest Bengal and Bangladesh (Bhattacharya et al., 1997). Arsenicis the twentieth most abundant element in the earth (ATSDR,

ll rights reserved.

: +91 788 2210163.. Pandey).

1998). Symptoms of arsenicosis are primarily manifested in theforms of different types of skin disorders such as skin lesions,hyperkeratosis, and melanosis.

Many scientists have been trying to remove arsenic from thedrinking water as well as industrial effluents using adsorptive re-moval technique (Chakravarty et al., 2002; Dambies, 2004; Kamalaet al., 2005; Zeng, 2003). Existing methods of arsenic removal in-clude oxidation (Chiu and Hering, 2000), ion-exchange, precipita-tion (Chow, 1997), adsorption (Elizalde, 2001; Dambies, 2004;Gregor, 2001), and ultra filtration.

The process of adsorption is a good alternative because it canremove the disadvantages of the classical chemical destabilization.Numerous biological materials have been tested for the removal oftoxic metal ion from aqueous solution over the last two decades.However, only a limited number of studies have been investigatedon the use of adsorbents derived from biological sources, e.g. chito-san (Mcafee et al., 2001; Dambies et al., 2002), orange waste (Ghi-mire et al., 2002, 2003), fungal biomass (Say et al., 2003a,b;Loukidou et al., 2003), activated carbon (AC) produced from oathulls (Chuang et al., 2005), coconut husk carbon (CHC) (Manjuet al., 1998), a low-cost ferruginous manganese ore (FMO) (Suzukiet al., 2000), Garcinia cambogia (Kamala et al., 2005), alkaganeite(Solozhenkin et al., 2003), oxisol (Ladeira and Ciminelli, 2004),shirasu-zeolite (Xu et al., 2002), synthetic hydrotalcite (Kisoet al., 2005), lignite, peat chars (Allen et al., 1997; Mohan andChander, 2006), bonechar (Sneddon et al., 2005), to remove arsenicfrom aqueous solution.

P.K. Pandey et al. / Bioresource Technology 100 (2009) 634–637 635

This communication reports the removal of As(III) from con-taminated drinking water using a novel plant biomass of Momor-dica charantia. Batch experiments were performed to evaluate theadsorption characteristics of the biomass for As(III) in a syntheticsolution.

2. Methods

2.1. Plant collection and preparation of the biomass

The M. charantia plants were collected from the different siteslocated in the region of Durg, Chattisgarh, India. After the collec-tion, an appropriate body part was plucked and washed withdeionized water, then cut into small pieces and subsequently driedin an electric oven at 60 �C for 3 days. The dried biomass wasground and sieved through 100-mesh Tyler screen and the fine bio-mass obtained was used in the adsorption experiments.

2.2. Adsorption study biosorption experiment

Experiments to determine the contact time required for equilib-rium sorption experiments were performed in Erlenmeyer flasks,using 1 l of metal solution and approximately 5 g of biomass (drymatter). The flasks were maintained at 28 �C. Samples were re-moved at different time intervals, filtered and analyzed by hydridegeneration atomic absorption spectrophotometer (Chemito-302).

Batch equilibrium sorption experiments were carried out in125 ml Erlenmeyer flasks with 50 ml of metal solution and 0.25 gof biomass for 45 min. These experiments were done at pH 2, 3,4, 6, 8, 9, 10, and 11 at 28 �C. Solutions of 0.1 M NH3 and H2SO4

were used to adjust the pH. After the sorption equilibrium wasreached (�45 min), the solution was separated from the biomassby filtration.

The initial and equilibrium arsenic concentrations in each flaskwere determined by AAS.

The amount of metal ion adsorbed by the biomass was calcu-lated by

qe ¼ Ci � Ce=m;

where Ci is the initial concentration of metal ion (mg/l), Ce is theequilibrium concentration of metal ion (mg/l), m is the mass ofadsorbent (g/l) and qe is the amount of metal ion adsorbed per gramof adsorbent.

Experiments were carried out in triplicate to ascertain the repro-ducibility and the results with mean, standard deviation (SD) andstandard error (SE) are reported here. Experiments done with blankindicate that no precipitation of metal ions occurred under the con-ditions selected. Experiment done with control biomass indicates norelease of metal by the biomass. The effects of process variables suchas pH (2–11), biosorbent dosage (1–50 g/l), initial metal ion concen-tration (0.1–100 mg/l), contact time, and background ions which arecommonly present in drinking water and some ions which are toxicto living organisms such as Ca2+, Mg2+, HCO�3 , Cl�, SO2�

4 , Cd2+, Se4+ (5–1000 mg/l), on As(III) uptake were investigated. Quality controlchecks were carried out by interlaboratory test using ICP-OES (Var-ian, Australia) at DMRL, Hyderabad.

2.3. Desorption of the adsorbed metal ions

In order to remove the bound metal ions from the biomass, aknown amount of biomass was taken into a 250 ml beaker. Batchkinetic studies were first conducted using the biomass to deter-mine the time needed for the As(III) binding process to reach theequilibrium state. After the biosorption tests, the biomass waswashed with deionised water for 15 min and left in 15 ml different

eluting agents for 30 min at room temperature in a beaker. The bio-mass was separated from the solution by filtration and washedwith deionized water until the pH of the filtrate reached 7. Thenthe recovered biomass was dried in an electric oven at 60 �C andthe capacity to biosorb metal was determined. Batch experimentwas conducted to desorb bound As(III) from the biomass using dif-ferent eluting agents such as NaOH, NaCl, Na2CO3, HCl, and HNO3

at predetermined concentrations.

2.4. Batch interference studies

The metal binding capacity experiments were repeated withsolution containing the binary mixture of different common ionsusually present in water with As(III) solution. The effect of calcium,magnesium, cadmium, selenium, chloride, sulphate, and bicarbon-ate concentrations varying from 5 to 1000 mg/l was investigated.

2.5. FT-IR method

The FT-IR study of fresh biomass and metal loaded biomass ofM. charantia using the detector DTGS KBr, Beam splitter KBr, infra-red source was done with Branch Thermo Nicolet Nexus 670 Spec-trometer. This FT-IR study was done in Indian Institute of ChemicalTechnology, Hyderabad.

3. Results and discussion

3.1. Effect of pH on biosorption

The pH of the aqueous solution is an important controllingparameter in the adsorption process. The effect of pH (2–10) onthe removal of As(III) for a constant biosorbent dosage of 5 g/l,standing time 45 min and metal ion concentration of 0.5 mg/lwas studied. It was found that pH had a marked effect on the metaluptake in this experiment. The percentage adsorption of metal ionwas found to increase with an increase in pH upto 9.5 and then itdecreased with a further increase of pH. The optimum pH for theremoval of As(III) was found to be 9. It could be related to the factthat with the increase of alkalinity (pH) the value of redox poten-tial (Eh) of arsenic (As3+, As5+, As0, and As3�) steadily decreases.Aqueous solution of arsenic acid (H3As5+O4) is formed in a stronglyacidic environment at high Eh. The most common species in natu-ral water is HAsO2�

4 which is stable under neutral to mildly alkalinewater at a negative Eh value. The common aqueous solution of As3+

is arseneous acid (H3AsO3), which is stable in the range of alkalin-ity, pH 8–10.

3.2. Time dependence studies for metal binding

The variation in percentage removal of As(III) with time was stud-ied using the solution of As(III) with initial concentration of 0.5 mg/l,adsorbent dosage 5 g/l at pH 9. The time was varied from 5 to 60 min.On increasing the contact time, the percentage removal (SD 1.41 andSE 1) was found to gradually increase till 45 min. Further increase intime decreased the removal of As(III). Hence, the optimum contacttime for As(III) removal was 45 min at pH 9.

3.3. Effect of adsorbent dosage on metal adsorption

To achieve the maximum adsorption capacity of As(III), theexperiment was conducted under optimum conditions (fixed con-tact time of 45 min, initial concentration of metal 0.5 mg/l at pH 9).The effect of biosorbent dosage (1–50 g/l) on the percentage re-moval of As(III) was studied. The adsorption was found to increasefrom 66% to 88% with increasing adsorbent dosage from 1 to 5 g/l.

0

20

40

60

80

100

120

5 10 50 100 200 500 1000Concentration of co-ionsmg/L

Per

cen

tag

e R

emo

val

Ca Mg Cd Se

Fig. 1. Effects of calcium, magnesium, cadmium, and selenium ions on thebiosorption of As(III).

5 10 50 100 200 500 1000Concentration of co-ionsmg/L

0

10

20

30

40

50

60

70

Per

cen

tag

e R

emo

val

Cl- So4 HCO3-

Fig. 2. Effects of chloride, sulphate, and bicarbonate ions on the biosorption ofAs(III).

636 P.K. Pandey et al. / Bioresource Technology 100 (2009) 634–637

Further increase in dosage showed a decrease in the percentage re-moval of As(III). Hence, the optimum biosorbent dosage is reportedas 5 g/l.

3.4. Effect of initial metal ion concentration

The effect of adsorbate concentration was studied by varyingAs(III) concentration from 0.1 to 100 mg/l, while keeping the adsor-bent dosage fixed at 5 g/l, contact time 45 min and the pH 9. The re-sults indicate that the percentage removal gradually decreased withincreasing initial concentration of As(III). This is due to lack of avail-able active sites on the adsorbent surface. The percentage removalwas 99–20% from 0.1 to 100 mg/l of As(III) solution.

3.5. Adsorption isotherm

The quantity of adsorbate that can be taken up by an adsorbentis a function of both the characteristics and concentration of adsor-bate and the temperature. Generally, the amount of material ad-sorbed is determined as a function of the concentration at aconstant temperature, and the resulting function is called anadsorption isotherm. The Freundlich and Langmuir isotherms areused most commonly to describe the adsorption characteristics.The Freundlich isotherm is widely used to describe adsorption ona surface having heterogeneous energy distribution. The Langmuirisotherm is applicable to monolayer chemisorption. The equilib-rium data for the removal of As(III) by adsorption at pH 9 wereused with Freundlich and Langmuir isotherms.

The linear form of Freundlich isotherm is

log S ¼ log KF þ ð1=NÞ log Cs;

where S is the moles sorbed at equilibrium per mass of sorbent (mg/g), i.e. (Ce/m), KF is the Freundlich isotherm constant (l/g), N is theFreundlich isotherm constant; N P 1, and Cs is the sorbate concen-tration in solution at equilibrium (mg/l). The constant KF is the mea-sure of adsorption capacity and 1/N is the measure of adsorptionintensity.

The linear form of Langmuir isotherm is

S ¼ ðK�LA�MCÞ=ð1þ KLCÞ;

where S is the moles sorbed at equilibrium /mass of sorbent (mg/g),i.e. Ce/m, AM is the maximum sorption capacity of the sorbent (mg/g), KL is the Langmuir sorption constant, related to binding energy ofthe sorbate (l/mg), Cs is the sorbate concentration in solution atequilibrium (mg/l), AM is the maximum sorption capacity of the sor-bent, and K is the Langmuir adsorption constant.

For Freundlich isotherm plot of log Ce/m against log Cs provides astraight line with a slope of 1/N and an intercept of log KF. And forLangmuir isotherm using the equation, sorption data Cs/Ce/m vs. Cs

are plotted to produce a line with a slope of 1/AM and an interceptof 1/(KL AM) Freundlich constant and Langmuir constant were calcu-lated. Results shows that the R2 value is 0.9275 for Freundlich iso-therm, which was slightly greater than the R2 value of Langmuirisotherm, i.e. 0.9027, so the results indicate that both models, Lang-muir and Freundlich, fit reasonably well with the experimental data.

3.6. Elution tests

One of the objective of this work is not only the removal ofAs(III) from water, but also the recovery of metal as well as reus-ability of biomass. Reusing of biomass required that the bound spe-cies be eluted from the biomass. Elution tests were conductedusing the batch technique to select an eluting agent that could des-orb all the bound As(III) from biomass. Different eluting agentssuch as 0.1 M of HCl, HNO3, NaOH, Na2CO3, and NaCl were used.It is evident that the acids HNO3 and HCl performed poorly over

the range of concentrations tested. On the other hand 97% elutionof the bound As(III) could be achieved using NaOH. Na2CO3 andNaCl show 85% and 72% recovery, respectively. By using NaOH,Na2CO3, and NaCl as the eluting agents the removal of arsenic fromthe loaded biomass was maximum, which could be due to the for-mation of sodium arsenate.

3.7. Studies of influencing co-occurring inorganic solutes

The influences of co-ions on arsenic biosorption by the biomasswere evaluated. Effect of initial metal ion concentration on theadsorption process of various co-ions Ca2+, Mg2+, Cd2+, Se4+,HCO�3 , SO2�

4 , and Cl� are shown in Figs. 1 and 2. Results clearlyshows that the percentage removal of As(III) were less than 70%with the presence of a very low concentration of various ions suchas SO2�

4 , Cl�, HCO�3 , Ca2+, and Mg2+. However, in the presence ofselenium and cadmium, the removal efficiency was found to in-crease from 85% to 100%. The decrease of percentage removal inthe presence of calcium and magnesium ions may be explainedbased on the ionic radii. All these ions are bigger than As(III) andthat is why in their presence the percentage removal decreases.On the other hand the ionic radii of Cd2+ and Se4+ are nearly thesame, so there was no decreasing effect.

3.8. FT-IR studies

The interpretation of infrared spectra involves the correlation ofabsorption bands in the spectrum of an unknown compound withthe known absorption frequencies for the types of bonds. The iden-tification of the source of an absorption band are intensity (weak,medium or strong), shape (broad or sharp), and position (cm�1) inthe spectrum. FT-IR study of fresh biomass and metal loaded

P.K. Pandey et al. / Bioresource Technology 100 (2009) 634–637 637

biomass show a major difference in the region 3400–2800 and1700–1200 cm�1 indicating chelation of As(III) with the –OH groupsfor fresh biomass of M. charantia. The peak around 2940–2920 cm�1

is assigned to –OH group of the organic constituents in differentparts of the biomass. The FT-IR results of this study showed the shiftfrom 1640 to 1680 cm�1. This shift corresponds to the C@O grouppresent in the organic acid (Padmarathy et al., 2003). An absorptionin the region between 1350 and 1470 cm�1 indicates the presence ofC–H bonding in alkane, C–O stretching is confirmed by the peak ob-served in the region between 1080 and 1300 cm�1, this indicatesthat the biomass contains acidic groups. The Biomass also containsamine groups, which is confirmed by the absorption in the regionof 1020–1340 cm�1 (Ashkenazy et al., 1997).

Hence, based on FT-IR spectrum analysis it can be inferred thatthe metal binding in the biomass of M. charantia takes place by thesubstitution of amine and carboxylic groups by the As(III).

3.9. Application of biomass for the removal of arsenic from drinkingwater and as dietary supplement

The studies conducted using synthetic metal ion solution (mul-ti-component) revealed the effectiveness of the biomass as a po-tential sorbent for the removal of As(III) from contaminatedground water. The metal ions and the range of concentrations cho-sen are representative of contaminated drinking water. In a set ofexperiments the biomass demonstrated that 0.5 mg/l of arsenicpresent in the contaminated drinking water could be removed to85% at pH 9 (adjusted). Reuse of the biomass could be possibleby desorbing the metals by the method mentioned in the regener-ation experiment.

We have also conducted a limited research on the efficacy ofthis biomass as a dietary supplement to the arsenicosis patientsin the Rajnandgaon district of Chhattisgarh state and very encour-aging results are being obtained towards the amelioration of theproblem. Palliative properties of the biomass have been observedbeyond any doubt.

4. Conclusion

The biomass of the edible plant of M. charantia demonstrated agood capacity of arsenic biosorption, highlighting its potential forthe drinking water treatment process.

The biomass was successfully used as biosorbent of As(III) fromaqueous solution with 88% sorption efficiency from 0.5 mg/l As(III)solution. pH had a strong effect on biosorption capacity and theoptimum pH deduced is 9. The biosorption was rapid and equilib-rium achieved within 45 min. The uptake capacity of metal wasfound to be 0.88 mg/g for 0.5 mg/l of As(III). Adsorption isothermconstant was calculated and the results indicate that both models,Langmuir and Freundlich sorption models, were in good agreementwith the experimental results. The influences of various commonions present in drinking water were investigated. No significantinfluence on removal of As(III) by the biomass was observed inthe presence of SO2�

4 , Cl�, HCO�3 , Ca2+, and Mg2+. And in the pres-ence of selenium and cadmium the removal efficiency was foundto be 85–100%.

References

Allen, S.J., Whitten, L.J., Murray, M., Duggan, O., 1997. The adsorption of pollutantsby peat, lignite and activated chars. J. Chem. Technol. Biotechnol. 68, 442–452.

Ashkenazy, R., Gottlieb, L., Yannai, S., 1997. Characterization of acetone washedyeast biomass functional groups, involved in lead biosorption. Biotechnol.Bioeng. 55 (1), 1–10.

ATSDR (Agency for Toxic Substances and Disease Registry), 1998. DraftToxicological Profile for Arsenic. Prepared for the US Department of Healthand Human Services, ATSDR, by the Research Triangle Institute. August 1998.

Bhattacharya, P., Chatterjee, D., Jacks, G., 1997. Occurrence of as-contaminatedgroundwater in alluvial aquifers from Delta Plains, Eastern India: options forsafe drinking water. Water Res. Dev. 13, 79–92.

Chakravarty, S., Dureja, V., Bhattacharyya, G., Maity, S., Bhattacharjee, S., 2002.Removal of arsenic from groundwater using low cost ferruginous manganeseore. Water Res. 36 (3), 625–632.

Chiu, V.Q., Hering, J.G., 2000. Arsenic adsorption and oxidation at manganitesurfaces. 1. Method for simultaneous determination of adsorbed and dissolvedarsenic species. Environ. Sci. Technol. 34 (10), 2029–2034.

Chow, W., 1997. Removing traces elements from power plant wastewater. Pollut.Eng. 19, 54–55.

Chuang, C.L., Fan, M., Xu, M., Brown, R.C., Sung, S., Saha, B., Huang, C.P., 2005.Adsorption of arsenic(V) by activated carbon prepared from oat hulls.Chemosphere 61 (4), 478–483.

Dambies, L., 2004. Existing and prospective sorption technologies for the removal ofarsenic in water. Separation Sci. Technol. 39, 603–627.

Dambies, L., Vincent, T., Guibal, E., 2002. Treatment of arsenic containing solutionusing chitosan derivatives: uptake mechanism and sorption performances.Water Res. 36, 3699–3710.

Elizalde, M.P., 2001. Sorption on natural solids for arsenic removal. Chem. Eng. J. 81,187–195.

Ghimire, K.L., Inoue, K., Yamaguchi, H., Makino, K., Miyajima, T., 2003. Adsorptiveseparation of arsenate and arsenite anions from aqueous medium by usingorange waste. Water Res. 37, 4945–4953.

Ghimire, KN., Inoue, K., Makino, K., Miyajima, T., 2002. Adsorptive removal ofarsenic using orange juice residue. Separation Sci. Technol. 37, 2785–2799.

Gregor, J., 2001. Arsenic removal during conventional aluminium based drinkingwater treatment. Water Res. 35 (7), 1659–1664.

IARC, 2004. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans.Some Drinking-Water Disinfectants and Contaminants, including Arsenic, vol.84. IARC Press, Lyon (192 IARC Monographs, vol. 86).

Kamala, C.T., Chu, K.H., Chary, N.S., Pandey, P.K., Ramesh, S.L., Sastry, A.R.K.,Chandrashekhar, K., 2005. Removal of As(III) from aqueous solution using freshand immobilized biomass. Water Res. 39, 2815–2826.

Kiso, Y., Jung, Y.J., Yamada, T., Nagai, M., Min, K.S., 2005. Removal properties ofarsenic compounds with synthetic hydrotalcite compounds. Water Sci. Technol.Water Supply 5 (5), 75–81.

Ladeira, A.C.Q., Ciminelli, V.S.T., 2004. Adsorption and desorption of arsenic on anoxisol and its constituents. Water Res. 38 (8), 2087–2094.

Loukidou, M.X., Matis, K.A., Zouboulis, A.I., Liakopoulou-Kyriakidou, M., 2003.Removal of As(V) from wastewater by chemically modified fungal biomass.Water Res. 37, 4544–4552.

Manju, G.N., Raji, C., Anirudhan, T.S., 1998. Evaluation of coconut husk carbon, forthe removal of arsenic from water. Water Res. 32 (10), 3062–3070.

Mcafee, B.J., Gould, W.D., Nadeau, J.C., da Costa, A.C.A., 2001. Biosorption of metalions using chitosan, chitin and biomass of Rhizopus oryzae. Separation Sci.Technol. 36, 3207–3222.

Mohan, D., Chander, S., 2006. Removal and recovery of metal ions from acid minedrainage using lignite—a low cost sorbent. J. Hazard. Mater. 137 (3), 1545–1553.

Padmarathy, V., Vasudevan, P., Dhingra, S.C., 2003. Thermal end spectroscopicstudies on sorption of Ni(II) ion on protonated bakers yeast. Chemosphere 52(10), 1807–1817.

Pandey, P.K., 2000. Who should be credited for the discovery and first reporting ofarsenicosis in Kaudikasa in Madhya Pradesh? Curr. Sci. 78, 1412.

Pandey, P.K., Khare, R.N., Sharma, S., Pandey, M., 1999. Arsenicosis and deterioratingground water quality: unfolding crisis in central East Indian region. Curr. Sci. 77,686–693.

Pandey, P.K., Yadav, S., Nair, S., Sar, S., Pandey, M., 2001. Holistic theory of arseniccontamination. In: 3rd International India/Bangladesh Symposia on Reducingthe Impact of Toxic Chemicals in the Bengal Basin, Kolkata, India. 10–12February. Available from: <http://www/ghosh_research/abstracts2001/>.

Say, R., Yilmaz, N., Denizli, A., 2003a. Biosorption of cadmium, lead and arsenic ionsby the fungus Penicillium purpurogenum. Separation Sci. Technol. 38, 2039–2059.

Say, R., Yilmaz, N., Denizli, A., 2003b. Removal of heavy metal ions using the fungusPenicillium canescens. Adsorption Sci. Technol. 21, 643–650.

Sneddon, R., Garelick, H., Valsami-Jones, E., 2005. An investigation into arsenic(V)removal from aqueous solutions by hydroxylapatite and bonechar. Mineral.Mag. 69 (5), 769–780.

Solozhenkin, P.M., Deliyanni, E.A., Bakoyannakis, V.N., Zouboulis, A.I., Matis, K.A.,2003. Removal of As(V) ions from solutions bt akaganeite_FeO(OH)nanocrystals. J. Mining Sci. 39 (3), 287–296.

Suzuki, T.M., Bomani, J.O., Matsunaga, H., Yokoyama, T., 2000. Preparation of porousresin loaded with crystalline hydrous zirconium oxide and its application to theremoval of arsenic. React. Funct. Polym. 43 (1–2), 165–172.

US EPA (US Environmental Protection Agency), 1997. IRIS (Integrated RiskInformation System) On-line Database Maintained in Toxicology DataNetwork (TOXNET) by the National Library of Medicine, Bethesda,Maryland.

WHO (World Health Organization), 1999. Arsenic in Drinking Water, Fact Sheet No.210, Geneva.

Xu, Y.-H., Nakajima, T., Ohki, A., 2002. Adsorption and removal of arsenic(V) fromdrinking water by aluminum-loaded shirasu-zeolite. J. Hazard. Mater. 92 (B),275–287.

Zeng, L., 2003. A method for preparing silica-containing iron(III) oxide adsorbent forarsenic removal. Water Res. 37, 4351–4358.