Biosorption of Heavy Metals from Aqueous Solutions Using Water Hyacinth as a Low Cost Biosorbent

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1 Biosorption of Havy Mtals from Auous Solutions Using Watr Hyacinth as a Low Cost Biosorbnt Achanai Buasri 1,2* Nattawut Chaiyut 1,2 Kssarin Tapang 1 Supparok Jaronsin 1 Suthra Panphrom 1 1. Dpartmnt of Matrials Scinc and Enginring, Faculty of Enginring and Industrial Tchnology, Silpakorn Univrsity, Nakhon Pathom 73000, Thailand 2. National Cntr of Excllnc for Ptrolum, Ptrochmicals and Advancd Matrials, Chulalongkorn Univrsity, Bangkok 10330, Thailand * of th corrsponding author: [email protected] Abstract In this study, biosorption of Cu(II) and Zn(II) ions from auous solutions by watr hyacinth fibr was invstigatd as a function of initial solution concntration, initial biomass concntration and tmpratur. Solutions containing coppr and zinc ions wr prpard synthtically in singl componnt and th tim ruird for attaining adsorption uilibrium was studid. Th optimum sorption conditions wr studid for ach mtal sparatly. Th adsorption uilibrium data wr aduatly charactrizd by Langmuir, Frundlich, Tmkin and Dubinin-Radushkvich uations. Th uilibrium biosorption isothrms showd that watr hyacinth possss high affinity and sorption capacity for Cu(II) and Zn(II) ions, with sorption capacitis of mg Cu 2+ and mg Zn 2+ pr 1 g biomass, rspctivly. All rsults showd that watr hyacinth fibr is an altrnativ low cost biosorbnt for rmoval of havy mtal ions from auous mdia. Kywords: biosorption, low cost biosorbnt, wastwatr tratmnt, havy mtal 1. Introduction Many industrial procsss, such as mining, mtal pigmnt, rfining ors, frtilizr industris, tannris, battris manufacturing, papr industris and psticids, rsult in th rlas of havy mtals to auatic cosystms. Havy mtals ar toxic pollutants, which can accumulat in living tissus causing various disass and disordrs. Th major toxic mtal ions hazardous to humans as wll as othr forms of lif ar Cr, F, S, V, Cu, Co, Ni, Cd, Hg, As, Pb, Zn tc. Rmoval of toxic contaminants from wastwatrs is on of th most important nvironmntal issus. Sinc all havy mtals ar non-biodgradabl, thy must b rmovd from th pollutd strams for th nvironmntal uality standards to b mt (Witk-Krowiak t al. 2011). Svral mthods hav bn mployd to rmov havy mtal ions from wastwatr, which includ chmical prcipitation, chmical oxidation/rduction, flotation, rvrs osmosis, ion xchang, mmbran-rlatd procss, ultra filtration, lctrochmical tchniu and biological procss (Dursun 2006; Satapathy & Natarajan 2006; Vijayaraghavan t al. 2007; Wang t al. 2006; Dng t al. 2007; Hanif t al. 2007; Prtha & Viruthagiri 2007). Adsorption is th most attractiv mthod du to its simplicity, convninc and high rmoval fficincy. In common sorption procsss, activatd carbon and synthtic rsins ar usually usd to gain high rmoval fficincy. Howvr, du to thir high production cost, watr dcontamination by using ths two sorbnts is rathr xpnsiv (Southichak t al. 2006; Choi & Jang 2008; Francsca t al. 2008; Zhng t al. 2009). Sinc 1990 s th adsorption of havy mtal ions by low cost rnwabl organic matrials has gaind momntum (Viira & Volsky, 2000; Rao & Parwat 2002). Th utilization of sawds, moulds, yasts, and othr dad microbial biomass and agricultural wast matrials for rmoval of havy mtals has bn xplord (Sudha & Abraham 2003). Agricultural matrials particularly thos containing cllulos shows potntial mtal biosorption capacity. Th basic componnts of th agricultural wast matrials biomass includ hmicllulos, lignin, xtractivs, lipids, protins, simpl sugars, watr hydrocarbons, starch 17

2 containing varity of functional groups that facilitats mtal complxation which hlps for th sustring of havy mtals (Hashm t al. 2005; Hashm t al. 2007). Agricultural wast matrials bing conomic and cofrindly du to thir uniu chmical composition, availability in abundanc, rnwabl, low in cost and mor fficint ar sm to b viabl option for havy mtal rmdiation (Sud t al. 2008). Watr hyacinth (Eichhornia crassips) is a noxious wd that has attractd worldwid attntion du to its fast sprad and congstd growth, which lad to srious problms in navigation, irrigation, and powr gnration. On th othr hand, whn lookd from a rsourc angl, it appars to b a valuabl rsourc with svral uniu proprtis. As a rsult, rsarch activity concrning control (spcially biological control) and utilization (spcially wastwatr tratmnt or phytormdiation) of watr hyacinth has boomd up in th last fw dcads (Malik 2007). Th objctiv of this study was to invstigat th potntial of watr hyacinth for absorbing coppr (II) and zinc (II) from auous solution. Also th influnc of various paramtrs such as initial solution concntration, initial biomass concntration and tmpratur on biosorption potntial of agricultural wast matrial was studid in dtail. 2. Exprimntal 2.1 Biosorbnt Prparation Raction of cllulos with phosphoric acid was prformd according to th mthod dscribd in th prvious rsarch (Suflt t al. 2006). In a 500 ml, thr-nckd flask uippd with a nitrogn inlt, a condnsr, a thrmomtr, and a stirrr, 224 g ura was addd, hatd at 140 o C and flushd with nitrogn. 30 g watr hyacinth and 168 ml phosphorous acid wr addd altrnativly portionwis to th moltn ura in ordr to rduc th foaming. Th raction was allowd to procd at 150 o C for 2 h. Th fibr was washd with distilld watr and acton. A sampl of fibr was tratd with 0.5 M hydrochloric acid for 24 h undr slow stirring. Th modifid cllulos was washd svral tims with dionizd watr to rmov xcss acid from biosorbnt. It was drid for 24 h at 60 o C in an ovn bfor starting th xprimnts. 2.2 Mtal Solution Prparation All chmicals usd wr analytical grad ragnts (Mrck, >99 %purity). Stock solutions of mtals wr prpard in a concntration of 2,000 ppm using nitrat salts dissolvd in dionizd watr with a rsistivity valu of 17 MΩ. Th chmicals usd in th batch xprimnts wr nitrat solutions of Cu(NO 3 ) 2 and Zn(NO 3 ) Isothrm Exprimnts Batch mod adsorption isothrm was carrid out at o C. Amount of g modifid cllulos wr introducd into conical flasks with 100 ml of havy mtal solution. Th flasks wr placd in a thrmostatic shakr and agitatd for 150 min at a fixd agitation spd of 700 rpm. Sampls wr takn priodically for masurmnt of auous phas of havy mtal concntrations. Adsorption isothrms wr prformd for initial havy mtal concntrations of 250-1,250 ppm. Th Cu (II) and Zn (II) concntration of th sampls wr dtrmind by using a Varian Librty 220 inductiv coupld plasma mission spctromtr (ICP-ES). Th amount of adsorbd Cu 2+ and Zn 2+ ions (mg mtal ions/g biomass) wr calculatd from th dcras in th concntration of mtal ions in th mdium by considring th adsorption volum and usd amount of th biosorbnt: C ( i 18 C) V m (1)

3 whr is th amount of mtal ions adsorbd into unit mass of th biosorbnt (mg/g) at uilibrium, C i and C ar th initial and final (uilibrium) concntrations of th mtal ions in th solution (ppm), V is th volum of mtal solution (L) and m is th amount of biosorbnt usd (g). 2.4 Adsorption Isothrm Modls Batch Adsorption isothrms for coppr and zinc ions rmoval by watr hyacinth in trms of Langmuir, Frundlich, Tmkin and Dubinin-Radushkvich modls wr xprssd mathmatically. Th obtaind xprimntal data hr ar xpctdly wll fittd with th linarizd form of four two-paramtr isothrm modls. Th Langmuir modl assums a monolayr adsorption of soluts onto a surfac comprisd of a finit numbr of idntical sits with homognous adsorption nrgy. This modl (Langmuir 1916; Langmuir 1918) is xprssd as follows: 1 + K LaLC alc (2) whr K L and a L ar th Langmuir constants rlatd to th adsorption capacity (mg/g) and nrgy of adsorption (L/mg), rspctivly. Th thortical maximum monolayr adsorption capacity, m (mg/g), is givn by K L /a L. Th Frundlich isothrm is an mpirical xprssion that taks into account th htrognity of th surfac and multilayr adsorption to th binding sits locatd on th surfac of th sorbnt. Th Frundlich modl (Frundlich 1906) is xprssd as follows: K whr K F and n ar indicativ isothrm paramtrs of adsorption capacity (mg/g) and intnsity, rspctivly. Tmkin isothrm assums that dcras in th hat of adsorption is linar and th adsorption is charactrizd by a uniform distribution of binding nrgis. Tmkin isothrm (Tmkin & Pyzhv 1940) is xprssd by th following uation: F C 1/ n (3) RT b ln ( K T C) (4) whr K T is uilibrium binding constant (L/g), b is rlatd to hat of adsorption (J/mol), R is th gas constant (8.314 x 10-3 kj/k mol) and T is th absolut tmpratur (K). Dubinin-Radushkvich isothrm is applid to find out th adsorption mchanism basd on th potntial thory assuming htrognous surfac (Dabrowski 2001). Dubinin-Radushkvich isothrm (Dubinin & Radushkvich 1947; Dubinin 1960; Kalavathy & Miranda 2010) is xprssd as follows: 2 ( ) xp Kε m whr m is th maximum adsorption capacity (mg/g), K is a constant rlatd to th man fr nrgy of adsorption and ε is th Polanyi potntial. (5) 3. Rsults and Discussion Biosorption of havy mtal ions onto th surfac of a biological matrial is affctd by svral factors, such as initial solution concntration, initial biomass concntration and tmpratur. 19

4 3.1 Effct of Initial Solution Concntration Figur 1 illustrats th adsorption of Cu(II) and Zn(II) ions by watr hyacinth as a function of initial mtal ion concntration. This incras continus up to 1,000 for Cu 2+ and 750 ppm for zn 2+ and byond this valu, thr is not a significant chang at th amount of adsorbd mtal ions. This platau rprsnts saturation of th activ sits availabl on th biosorbnt sampls for intraction with mtal ions. It can b concludd that th amount of mtal ions adsorbd into unit mass of th watr hyacinth at uilibrium (th adsorption capacity) rapidly incrass at th low initial mtal ions concntration and thn it bgins to a slight incras with incrasing mtal concntration in auous solutions in th lngth btwn 1,000 and 1,250 ppm for coppr, but 750 and 1,250 ppm for zinc. Ths rsults indicat that nrgtically lss favorabl sits bcom involvd with incrasing mtal concntrations in th auous solution. Th mtal uptak can b attributd to diffrnt mchanisms of ion xchang and adsorption procsss as it was concrnd in much prvious work (Bktas & Kara 2004; Buasri t al. 2007). 3.2 Effct of Initial Biomass Concntration Exprimnts conductd with diffrnt initial biomass concntrations show that th mtal ions uptaks incras with th biosorbnt concntration (Figur 2). Th numbr of sits availabl for biosorption dpnds upon th amount of th biosorbnt. Th mtal ions uptak was found to incras linarly with th incrasing concntration of th biosorbnt up to th biomass concntration of 2 and 3 g/100 ml for Cu(II) and Zn(II), rspctivly. Byond this dosag, th incras in rmoval fficincy was lowr. Incrasing th biosorbnt dosag causd a wis in th biomass surfac ara and in th numbr of potntial binding sits (Witk-Krowiak t al. 2011). 3.3 Effct of Tmpratur From Figur 3, th amounts of adsorbd coppr and zinc ions onto th watr hyacinth incras with an incras in th tmpratur of havy mtal solution. Th maximum adsorption capacitis was calculatd as mg Cu 2+ and mg Zn 2+ pr 1 g biomass for initial concntration of 500 ppm at 70 o C, showd that this biosorbnt was suitabl for havy mtals rmoval from auous mdia. Concrning th ffct of tmpratur on th adsorption procss, th mtals uptak is favord at highr tmpraturs, sinc a highr tmpratur activats th mtal ions for nhancing adsorption at th coordinating sits of th minrals. Also, it is mntiond that cations mov fastr with incrasing tmpratur. Likly xplanation for this is that rtarding spcific or lctrostatic, intractions bcom wakr and th ions bcom smallr, bcaus solvation is rducd (Babl & Kurniawan 2003; Inglzakis t al. 2004). 3.4 Effct of Initial Biomass Concntration In addition to th xprimntal data, th linarizd forms of Langmuir, Frundlich, Tmkin and Dubinin-Radushkvich isothrms using Es. (2), (3), (4) and (5), ar compard. Th rlationship btwn th adsorbd and th auous concntrations at uilibrium has bn dscribd by four two-paramtr isothrm modls. Th isothrm constants and corrsponding corrlation cofficints for th adsorption of Cu(II) and Zn (II) ar prsntd in Tabl 1. Th corrlation cofficints dmonstrat that Langmuir, Frundlich and Tmkin modls aduatly fittd th data for Cu adsorption. Howvr, th cofficint of dtrmination (R 2 ) valus ar highr in th Langmuir modl for coppr and Frundlich modl for zinc adsorption whn compard to othr modls. Th Tmkin isothrm shows a highr corrlation cofficint for both mtal (R for Cu 2+ and R for Zn 2+, which may b du to th linar dpndnc of hat of adsorption at low or mdium covrags. This linarity may b du to rpulsion btwn adsorbat spcis or to intrinsic surfac htrognity (Kalavathy & Miranda 2010; Caliskan t al. 2011). Th xprimntal data for both havy mtal ions fit wll with th linarizd Langmuir, Frundlich, Tmkin and 20

5 Dubinin-Radushkvich isothrms. R 2 valus rangd from to and to for adsorption of Cu 2+ and Zn 2+, rspctivly. Ths rsults indicatd that th uilibrium adsorption data of coppr and zinc conformd rasonably wll to th four two-paramtr isothrm modls uations. 4. Conclusion Watr hyacinth is an nvironmntally frindly potntial biosorbnt for havy mtals. This work xamind th fficincy of this sorbnt in rmoval of Cu(II) and Zn(II) ions from auous nvironmnt. Th rsults indicatd that svral factors such as initial solution concntration, initial biomass concntration and tmpratur affct th biosorption procss. Th physico-chmical charactristics of wastwatrs from varying sourcs can b much mor complx compard to th auous mtal solution usd in this study. Bcaus of this, th ffcts of othr componnts of wastwatrs on commrcial mtal adsorption procss should b dtrmind. Howvr, this work can b considrd a prliminary study to conclud that watr hyacinth is suitabl and fficint matrial for th adsorption of Cu 2+ and Zn 2+ from auous solution. Th xprimntal rsults wr a good fit with th adsorption isothrm modls. Acknowldgmnts Th authors acknowldg sincrly th Dpartmnt of Matrials Scinc and Enginring (MSE), Faculty of Enginring and Industrial Tchnology, Silpakorn Univrsity (SU) and National Cntr of Excllnc for Ptrolum, Ptrochmicals, and Advancd Matrials (PPAM), Chulalongkorn Univrsity (CU) for supporting and ncouraging this invstigation. Rfrncs Babl, S. & Kurniawan, T.A. (2003), Low-cost adsorbnts for havy mtals uptak from contaminatd watr, Journal of Hazardous Matrials 97, Bktas, N. & Kara, S. (2004), Rmoval of lad from auous solutions by natural clinoptilolit: Euilibrium and kintics studis, Sparation and Purification Tchnology 39, Buasri, A., Chaiyut, N., Ponpatcharasakul, N., Artsal, P. & Potisook, S. (2007), Factors affcting th rmoval of coppr(ii) and zinc(ii) from auous solutions with clinoptilolit, Journal of Rsarch in Enginring and Tchnology 4, Caliskan, N., Kul, A.R., Alkan, S., Sogut, E.G. & Alacaby, I. (2011), Adsorption of Zinc(II) on diatomit and mangans-oxid-modifid diatomit: A kintic and uilibrium study, Journal of Hazardous Matrials 193, Choi, M. & Jang, J. (2008), Havy mtal ion adsorption onto polypyrrol-imprgnatd porous carbon, Journal of Colloid and Intrfac Scinc 325, Dabrowski, A. (2001), Adsorption-from thory to practic, Advancs in Colloid and Intrfac Scinc 93, Dng, L., Zhu, X., Wang, X., Su, Y. & Su, H. (2007), Biosorption of coppr (II) from auous solutions by grn alga Cladophora fascicularis, Biodgradation 18, Dubinin, M.M. & Radushkvich, L.V. (1947), Euation of th charactristic curv of activatd charcoal, Chmischs Zntralblatt 1, Dubinin, M.M. (1960), Th potntial thory of adsorption of gass and vapours for adsorbnts with nrgtically non-uniform surfacs, Chmical Rviws 60, Dursun, A.Y. (2006), A comparativ study on dtrmination of th uilibrium, kintic and thrmodynamic paramtrs of biosorption of coppr(ii) and lad(ii) ions onto prtratd Asprgillus nigr, Biochmical Enginring Journal 28,

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7 Witk-Krowiak, A., Szafran, R.G. & Modlski, S. (2011), Biosorption of havy mtals from auous solutions onto panut shll as a low-cost biosorbnt, Dsalination 265, Zhng, J.C., Fng, H.M., Lam, M.H., Lam, P.K., Ding, Y.W. & Yu, H.Q. (2009), Rmoval of Cu(II) in auous mdia by biosorption using watr hyacinth roots as a biosorbnt matrial, Journal of Hazardous Matrials 171, Figur 1. Effct of initial solution concntration on th rmoval of Cu(II) and Zn(II) by watr hyacinth (amount of biosorbnt 2.0 g, tmpratur 30 o C and contact tim 150 min) 23

8 Figur 2. Effct of initial biomass concntration on th rmoval of Cu(II) and Zn(II) by watr hyacinth (initial solution concntration 500 ppm, tmpratur 30 o C and contact tim 150 min) Figur 3. Effct of tmpratur on th rmoval of Cu(II) and Zn(II) by watr hyacinth (initial solution concntration 500 ppm, amount of biosorbnt 2.0 g and contact tim 150 min) Tabl 1. Isothrm constants for th biosorption of Cu(II) and Zn(II) on watr hyacinth Isothrm constants Coppr Zinc Langmuir modl K L (mg/g) a L (L/mg) R 2 R 2 Tmkin modl K T (L/g) b R 2 Dubinin-Radushkvich modl m (mg/g) K R Frundlich modl K F (mg/g) n

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