Equilibrium and Kinetic Modeling of Heavy Metals Biosorption from Three Different Real Industrial Wastewaters Onto Ulothrix Zonata Algae

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1 Australian Journal of Basic and Applid Scincs, 5(12): , 2011 ISSN Equilibrium and Kintic Modling of Havy Mtals Biosorption from Thr Diffrnt Ral Industrial Wastwatrs Onto Ulothrix Zonata Alga 1 M. Malakootian, 2 A. Toolabi, 3 S Gh. Moussavi, 2 M. Ahmadian 1 Profssor of Environmntal Halth Rsarch Cntr and Environmntal Halth Enginring Dpartmnt, School of public Halth, Krman Univrsity of Mdical Scincs, Krman, Iran. 2 M.Sc of Environmntal Halth Enginring, School of Public Halth, Krman Univrsity of Mdical Scincs, Krman. 3 Associat Profssor of Environmntal Halth Enginring, School of Mdical Scincs, Tarbiat Modars Univrsity, Thran, Iran. Abstract: Biosorption can b an ffctiv procss for th rmoval of havy mtal from industrial wastwatrs. In this papr, th biosorption of coppr, zinc, lad, and cadmium from industrial wastwatrs by Ulothrix Zonata alga was invstigatd in batch xprimnts. Th influnc of algal dosag, initial concntration of havy mtals, sorption tim, particl siz, ph and tmpratur on rmoval fficincis of Ulothrix Zonata was studid. Frundlich and Langmuir modls wr applid to dscrib th biosorption isothrms. Th xprimntal data hav bn analyzd using first and scond ordr kintics. In 25 C, ph of 4 to 5, contact tim of 60 min and adsorbnt lvl of 1.5 g/l, rmoval lvl of coppr, zinc, lad and cadmium was 98.2%, 96%, 98.4% and 94.7% rspctivly. Among variabls studid hr, ph playd an important rol in absorption lvl of mtals so that in ph of 3 to 5, th highst absorption lvl was obsrvd. Kintic data of this study wr fittd to scond-ordr modls. Th adsorption quilibrium was rprsntd with Frundlich and Langmuir 2 adsorption isothrms. Isothrm paramtrs show that adsorbnt capacity for adsorbing lad is highr, whil adsorbing cadmium nds mor nrgy. Concrning high absorption fficincy, Ulothrix Zonata alga can ffctivly b usd to biosorption havy mtals from industrial wastwatr. Kywords: Kintic modling, biosorption isothrm, havy mtals, Ulothrix Zonata Alga, industrial wastwatr. INTRODUCTION Protcting nvironmnt from contamination causd by modrn industris and tchnologis is on of th concrns of today s world bcaus thy thratn humans public halth (Inghui and Caoc 2009). High tndncy of havy mtals to maintain, circulat and accumulat in food chain is on of th most important factors that show thir high importanc. Ths mtals ntr th nvironmnt du to various industrial procdurs including mlting, xtraction and purification. Prsnc of havy mtals and thir compounds, vn in small amounts, in industrial wastwatr is vry dangrous and must b rmovd (Hmtsarı 2008). Various mthods hav bn usd for rmoving havy mtals from wastwatr including ion xchang, chmical prcipitation, rvrs osmosis and adsorption. Physicochmical mthods rquir a rlativly high lvl of capital invstmnt compard to othr mthods (Lamaia, Kruatrachua t al. 2005). Som of ths mthods don t provid lgal ncssitis to rmov wastwatr in nvironmnt and also thy hav problms of rmoving sludg. On th othr hand, making us of low-cost mthods for rmoving havy mtals has bn takn into significant considration (Mhta and Gaur 2005; Hughs and Mcloughlin 2007). Concrning thir fficincy and asy application, adsorbnts ar considrd vry suitabl for rmoving havy mtals from industrial wastwatr. Sawdust, banana skin, huskd ric, ric bran, what bran, almond krnl, alga powdr, living alga and many othr things hav bn rportd by rsarchrs as adsorbnts (Ngah and Hanafiah 2008). In a study carrid out by Vitor t al in 2005 in Portugal, it was shown that among various mthods usd to rmov havy mtals in aquatic rsourcs including chmical prcipitation, mmbran procdurs and bio-absorption with th aid of Glidium rd alga, making us of bio-absorption mthod was bttr du to highr fficincy and lowr costs (Vitor and Pvilar 2008). In anothr study carrid out by Bayramolga t al in 2006 in Turky, bio-absorption of havy mtals by Chlamydomonas alga had high fficincy (Bayramoglu, Tuzun t al. 2006). In anothr study prformd by Gupta t al, it was shown that Spirogyra alga which xist in frsh and salty watrs has high potntial in adsorbing havy mtals undr thrmal changs and ph changs (Gupta and Rastogi 2008). Mchanism of adsorbing havy mtals by alga is as a rsult of som compounds lik polysaccharids, protins, groups lik amino, hydroxyl, carboxyl, acids, sulphat and othr compounds by which it bonds and thn it can adsorb thm (Jalali, Ghafourian t al. 2002; Vilar and Boavntura 2005). Although som rsarch has bn don in th fild of absorption lvl of havy mtals by diffrnt typs of alga in aquatic rsourcs, sinc typ of alga, aquatic Corrsponding Author: Krman, Haft Bagh Alavi Highway, Univrsity of Mdical Scincs School of Public Halth. m.malakootian@yahoo.com; Tl: , Fax:

2 rsourc, havy mtal as wll as mthods ar diffrnt, it is ncssary to carry out a comprhnsiv study rgarding bio-absorption of havy mtals in industrial wastwatr basd on analysis of information rsultd from adsorption isothrms in ordr to dvlop and dscrib th way how adsorbd matrial racts with adsorbnt as wll as to optimiz lvl of adsorbnt. In this cas, ral lvl of adsorbnt can b spcifid for vry matrial in th bst cas. Th aim of th prsnt study was to provid a kintic modling and bioabsorption isothrm of havy mtals from wastwatr rlatd to battry-making, lctroplating and coppr industris in Krman using Ulothrix Zonata grn alga. MATERIALS AND METHODS Biomass Prparation: Ulothrix Zonata grn alga was usd as biosorbnt for th biosorption of coppr, zinc, lad and cadmium ions. Ulothrix Zonata grn alga was collctd from Simarh Rivr in Kouhdasht, Iran. Sampls of th biomass wr washd svral tims using dionizd watr and drid in an ovn at 100 C for 24 h. Th powdrd biomass was passd through diffrnt standard sivs with msh of 20, 40, 60, 100 and 140. Wastwatr Sampling: In this priodic-dscriptiv study, clustr sampling was don from wastwatr of coppr, battry making and lctroplating industris in Krman for four continuous months. To dtrmin lvl of studid mtals and to study th ffct of grn alga on thm, 40 sampls wr takn from vry wastwatr. Totally, 120 sampls wr takn from th mntiond industrial wastwatr. Batch Adsorption Studis: First Cas: Ral Sampls: To find out th mtal biosorption capacity of th tratd biomass, 0.2, 0.4, 0.5, 1 and 1.5 g of drid Ulothrix Zonata alga was prpard. For wastwatr of vry industry (coppr, lctroplating and battry-making), th mntiond amounts wr xposd to th alga with contact tim of 80, 60, 45, 30 and 15 min in normal lab tmpratur (21 ±1 C) with 150 to 180 rpm using Jar dvic. Aftr dtrmining balancd contact tim, adsorption lvl of wastwatr of vry industry was studid in various phs of 3, 4, 5, 6 and 7 with mntiond amounts of drid alga and th optimum ph was spcifid for adsorbing lad, coppr, zinc and cadmium. In th nxt stp, wastwatr of various industris was studid in 10, 15, 20, 25 and 30 C undr ph and balancd xposur tim and th bst adsorption tmpratur was achivd for vry mtal. Thn, to dtrmin th optimum adsorption lvl, th achivd optimum variabls wr studid with 0.2, 0.4, 0.5, 1 and 1.5g of drid Ulothrix Zonata alga with th mntiond industrial wastwatr. Aftr th sampl was sivd, all mtals wr masurd by atomic absorption spctromtry (modl Shimadzu/AA-670). Scond Cas: Synthtic Sampls: To dtrmin maximum adsorption lvl of Lad, Coppr, Zinc and Cadmium by drid Ulothrix Zonata alga and to dtrmin th ffct of adsorbnt on adsorption lvl of mtals, synthtic solutions wr prpard for Coppr, Lad, Zinc and Cadmium in concntrations of 40, 60, 80, 100 and 120mg. To prpar synthtic solutions, Cd (NO3) 2.2H2O, ZnCl 2, CuCl 2, Pb (NO3) 2.4H 2 o (Mrck Company) wr usd. To adjust ph, HCl 0.1N and NaOH 0.1N solutions wr usd. Thn, concrning th optimum variabls, ral wastwatr sampls (ph, tmpratur, balancd contact tim and adsorbnt lvl) affct th abov solutions. Aftr th sampls wr sivd, mtals adsorption was spcifid using atomic adsorption apparatus (Cucarlla and Rnman 2009): Whr: RE: fficincy of studid mthod (%) C 0 : initial concntration of givn mtal (mg/l) C t : initial concntration of givn mtal in t tim (mg/l) (1) Study Th Effct of Adsorbnt Particl Siz: To dtrmin th ffct of particl siz of Ulothrix Zonata alga adsorbnt, 20, 40, 60, 100 and 140 mshs wr usd. To do this, 1.5g of adsorbnt was addd to a litr of vry solution with concntration of 120mg/L of lad, coppr, zinc and cadmium undr optimum ph, tmpratur of 25 ºC and balancd xposur tim of 60min. Thn, thir adsorption lvl was spcifid. 1031

3 Equilibrium Exprimnts: Adsorption isothrms ar usd to dscrib th mass adsorbd from th adsorbd matrial for adsorbnt mass unit. In this rsarch, to study concntration lvl of adsorbd matrial, th following isothrms ar usd (Tabl1): Tabl 1: Spcifications of studid isothrms. Linar form 1 log q log K f logc n C 1 1 C q K LQ m Q m q Q m KLQ m C 1 q q Qm K L C q K LQm K Lq C Equation f 1 n q K C QmK LC q 1 K C L Isothrm typ Frundlich Longmuir 1 Longmuir 2 Longmuir 3 Longmuir 4 Kintic Study: To undrstand dynamics of adsorption ractions, information rsultd from adsorption kintic can b xamind. Two normal kintic typs studid in this rsarch hav bn prsntd in tabl 2. Tabl 2: Equations and linar form of kintic studid hr. Linar form k1 logq qt logq t t 1 1 t qt k q q 2 2 Equation dqt k1( q qt ) dt dqt k dt 2 2 ( q qt ) kintic typ Psudo first ordr Scond ordr Rsults: Charactrizations of Wastwatr: Charactrizations of industrial wastwatr sampls including initial ph, avrag concntration of havy mtals and tmpratur wr spcifid (Tabl 3). Tabl 3: Charactrizations of wastwatr of lctroplating, coppr and battry-making industris. Industris Havy mtals Avrag concntration of havy mtals (mg/l) Avrag wastwatr ph Avrag tmpratur of wastwatr basd on C Elctroplating Zinc Battry-making Cadmium Lad Coppr industris Coppr Effcts of Contact Tim: Th contact tim was valuatd as on of th important factors affcting th biosorption fficincy. Fig. 1 shows th biosorption fficincy of diffrnt havy mtals by Ulothrix Zonata alga. As contact tim incrasd, adsorption fficincy incrasd too so that as contact tim incrasd from 15 to 60 min, rmoval fficincy of coppr, zinc, lad and cadmium incrasd to 20, 22, 15.5 and 14% rspctivly. Effct of ph: According to th rsults, highst rmoval of coppr and lad occurrd in ph 4 and highst rmoval of zinc and cadmium happnd in ph of 5. In ph of 5 to 7, rmoval lvl of all mtals dcrasd, that is, 32, 38, 23.5 and 26.7% for coppr, zinc, lad and cadmium rspctivly. Influnc of Biosorbnt Dos: To dtrmin th ffct of adsorbnt dos, diffrnt quantitis of Ulothrix Zonata alga wr suspndd in havy mtal solutions. Th ffct of adsorbnt dos on havy mtals rmoval is shown in Fig. 3. As dos of Ulothrix Zonata alga incrasd, rmoval lvl incrasd too so that as adsorbnt lvl incrasd, rmoval lvl of coppr, zinc, lad and cadmium incrasd to 94.2%, 96%, 94.2% and 94.4% rspctivly and adsorption lvl dcrasd to 37, 26, 36.5 and 13.5 mg g -1 rspctivly. 1032

4 Fig. 1: Effct of contact tim on th xtnt of biosorptions (Initial concntration of coppr=57 mg/l, zinc= 41.2 mg/l, lad=55.5 mg/l, cadmium= mg/l, ph=7 and adsorbnt dos=1.5 g/l). Fig. 2: Effct of ph on th xtnt of biosorptions (Initial concntration of coppr=57 mg/l, zinc= 41.2 mg/l, lad=55.5 mg/l, cadmium= mg/l, contact tim =60 min and adsorbnt dos=1.5 g/l). Fig. 3: Th ffct of adsorbnt dos on th xtnt of biosorptions (Initial concntration of coppr=57 mg/l, zinc= 41.2 mg/l, lad=55.5 mg/l, cadmium= mg/l, contact tim =60 min and ph= 4 and 5). 1033

5 Effct of Tmpratur: Th rsults of havy mtal adsorption on th biosorbnt, at diffrnt tmpraturs ar shown in Fig. 4. As tmpratur incrasd from 10 to 20 ºC, rmoval fficincy incrasd too. In 20 ºC to 30 ºC, no significant chang was obsrvd in rmoving mtals. In 10 to 30 ºC, rmoval lvl of coppr, zinc, lad and cadmium incrasd to 11, 9.6, 5.3 and 11.1 rspctivly. Fig. 4: Th ffct of tmpratur on th xtnt of biosorptions (Initial concntration of coppr=57 mg/l, zinc= 41.2 mg/l, lad=55.5 mg/l, cadmium= mg/l, contact tim =60 min, adsorbnt dos=1.5 g/l, ph= 4 and 5). Effct of Particl Siz: Rsults rlatd to th ffct of particl siz on adsorption capacity ar shown in Fig. 5. According to th rsults, as particl siz dcrasd, rmoval lvl incrasd so that in msh of 140, th rmoval lvl with initial concntration of 120mg/L was 93%, 93%.5, 91% and 86.9% for coppr, zinc, lad and cadmium rspctivly and it was 82%, 79%, 75% and 73% for msh of 20. Fig. 5: Th ffct of particl siz on th xtnt of biosorptions (Initial concntration of havy mtals= 120 mg/l, contact tim =60 min, adsorbnt dos=1.5 g/l, tmpratur is 25 ºC, ph= 4 and 5). Effct of Initial Concntration: Th rsults of havy mtal adsorption at diffrnt initial concntration ar shown in Fig. 6. Initial concntration of havy mtals had a grat ffct on biosorption procss and as initial concntration incrasd, biosorption capacity also dcrasd. In initial concntrations of 40 to 120 mg/l, rmoval fficincy of coppr, zinc, lad and cadmium dcrasd from 98.5%, 96%, 98% and 88% to 81%, 80%, 78% and 65% rspctivly. Isothrms Modling: Th quilibrium data showd in Tabl 4 and 5 wr applid to Frundlich and Langmuir isothrms quations. 1034

6 Fig. 6: Th ffct of initial concntration on th xtnt of biosorptions (contact tim =60 min, adsorbnt dos=1.5 g/l, tmpratur is 25 ºC, ph= 4 and 5). Tabl 4: Rsults of Longmuir Modl Absorption Isothrms** Havy mtals Cd +2 Pb +2 Zn +2 Cu +2 Isothrm typ Isomtric paramtr Longmuir typ Longmuir typ Longmuir typ Longmuir typ ** avrag initial concntration of mtals is 57, 41.2, 55.5 and mg/l rspctivly and adsorbnt lvl is 1.5 g/l and ph is 4 and 5 Tabl 5: Rsults of Frundlich modl absorption isothrms *. Havy mtal Cd 2+ Pb 2+ Zn 2+ Cu 2+ Adsorbnt dos g/l K f n R 2 K f n R 2 K f n R 2 K f n R * avrag initial concntration of mtals is 57, 41.2, 55.5 and mg/l rspctivly and ph is 4 and 5 Kintic Modling: Th psudo-first-ordr and scond-ordr modls wr applid to tst adsorption kintics data to study th mchanism of biosorption. In Tabl 6 th stimatd valus of th modl paramtrs ar rportd. Conclusions: As it is obvious, absorption capacity of coppr, zinc, lad and cadmium by Ulothrix Zonata was high and absorption occurrd in a rlativly lowr tim priod according to synthtic quations. Sinc absorption capacity of mtals (using this adsorbnt) dpnds highly on solution ph, tmpratur, initial concntration of mtallic ions, adsorbnt siz, xposur tim and adsorbnt lvl, thus it is rcommndd that optimum cass of th abov-mntiond variabls should b prpard to achiv highr rmoval fficincy of havy mtals from industrial wastwatr (using Ulothrix Zonata as a bio-adsorbnt). 1035

7 Tabl 6: Rsults of xamining th studid kintic. Kintic typ Kintic Mtal typ paramtr Cu +2 Zn +2 Pb +2 Cd +2 Psudo first dgr Scond grad Discussion: As contact tim of adsorbnt with solutions containing coppr, zinc, lad and cadmium incrasd, absorption fficincy incrasd too. Rason of this incrasd xposur is incrasd contact btwn adsorbnt and mtals (it was achivd in balanc tim of 60 min). Rsults match th study carrid out in 2005 in Poland by Chonjnacka t al (Chojnacka, Chojnacki t al. 2005). To prvnt prcipitation of mtal hydroxyl and to prvnt rrors in rading absorption lvl, tsts wr don in phs of 3 to 7. As ph incras from 3 to 5, adsorption lvl incrasd so that in ph of 4, w had th highst adsorption lvl for coppr and lad and in ph of 5 th highst adsorption lvl was rlatd to zinc and cadmium. In phs of 5 to 7, adsorption lvl dcrasd and that s bcaus of high adsorption fficincy of bio-adsorbnts in acidic nvironmnts; in this cas, mtallic ions ar adsorbd proprly on spcifid adsorbnt bonds which hav H +. Ths rsults match th study carrid out in 2005 in Iran by Nabizadh t al (Nabizadh and Naddafi 2005). According to rsults, as adsorbnt dos incrasd, rmoval fficincy incrasd but adsorption lvl dcrasd; that is bcaus of polysaccharid and fibr-lik componnts availabl in cll walls of alga, adsorbnt activ surfac and dynamic factors including incrasd lvl of contact and incrasd fr bonds on adsorbnt surfac which can b spcifid according to adsorption isothrms and synthtic quations (Kumar, King t al. 2006; Ozr and Ozr 2008). Similar study carrid out by Ozr t al (Ozr and Ozr 2008), as tmpratur incrasd, adsorption lvl incrasd too so that minimum and maximum adsorption lvl was obsrvd in 10 and 30 ºC rspctivly; that s bcaus of incrasd ionic intractions of forming activ complxs among mtallic ions and polysaccharid compounds along with slctiv proprty of alga cll walls which can b sn in highr tmpraturs (Kawsarn 2002; Sarı and Tuzn 2008). Also, as adsorbnt siz dcrasd, adsorption lvl incrasd, bcaus in smallr sizs, contact ara of adsorbnt with mtal is highr and thus adsorption lvl incrass. Ths rsults match thos prformd by Kumar t al in 2006 in India (Kumar, King t al. 2006). Concrning th rsults, thr is a rvrs linar rlationship btwn mtals initial concntration and rmoval prcntag; that is, as initial concntration incrasd, rmoval fficincy dcrasd and that is du to highr ionic xchang bonds in lowr initial concntrations (Vanssa, Hln t al. 2007). q m lvl obtaind from Longmuir modls rflcts absorption lvl of mtallic ions ncssary for singl-layr formation and this amount is highr in adsorbing lad than that in othr mtals; this rflcts th fact that highr lvls of lad is rquird for singl-layr formation thus adsorption capacity of lad is highr than that of othr mtals. Similar rsults wr achivd by Vitor t al in 2008 in Portugal (Vıtor and Boavntura 2008). n and k f in Frundlich modl show adsorption nrgy. According to rsults, highst lvl of k f is rlatd to coppr and th highst amount of n is rlatd to adsorbing cadmium. Concrning Longmuir modls, lvls of K l in th prsnt study (for th bst adsorption cas) was 0.09, 0.08, and for coppr, zinc, lad and cadmium rspctivly. Thrfor, Coppr was adsorbd with a highr nrgy compard to othr mtals studid hr. Rsults obtaind from Frundlich and Longmuir modls ar similar in this cas. Rsults obtaind from a kintic study, which was carrid out to prdict adsorption vlocity in ordr to dsign and modl th procss, show that kintic of scond ordr quation is th bst modl for dtrmining raction vlocity using this adsorbnt; that is, at balanc tim of 60 min, rmoval lvl of coppr, zinc, lad and cadmium was 97.4%, 96.2%, 95.5% and 96.5% rspctivly. In a study carrid out (to dtrmin kintic bhavior of mtals adsorption) by Chn t al in 2008 in china, it was shown that adsorbing havy mtals in aquatic solutions by Undaria Pinnatifida follows th scond ordr kintic curv too (Chn, Ma t al. 2008). ACKNOWLEDGMENT This study was supportd financially by rsarch dputy of Krman Univrsity of Mdical Scincs. Th authors would also lik to thank th Environmntal Halth Rsarch Cntr, krman, Iran, for approval of th rsarch. 1036

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