Biosorption of Cr (III) from Aqueous Solutions Using Bacterium Biomass Streptomyces rimosus

Transcription

1 In. J. nviron. Rs., 3():9-38, Spring 009 ISSN: Biosorpion of Cr (III) from Aquous Soluions Using Bacrium Biomass Srpomycs rimosus Sahmoun, M.N. *, Louhab, K. and Boukhiar, A. Laboraoir Maériaux, rvêmn nvironnmn (LMR), Faculy of Scinc of h nginr, Univrsiy of Boumrds, Boumrds, Algria Déparmn chnologi alimnair, Faculy of Scinc of h nginr, Univrsiy of Boumrds, Boumrds, Algria Rcivd 6 April 008; Rvisd 5 Oc 008; Accpd 5 Dc 008 ABSTRACT: In h prsn invsigaion, dad bacrium biomass Srpomycs rimosus was usd as an inxpnsiv and fficin biosorbn for Cr (III) rmoval from aquous soluion. Th bacrial biomass was rad wih 0. M NaOH. Sorpion lvl of 65 mg/g was obsrvd a ph 4.8 whil prcipiaion ffc augmnd his valu a highr ph rang. Chromium dsorpion incrasd wih dcrasing dsorpion agns ph (including HCl and H ) o a maximum valu of 95% a approximaly zro ph. Langmuir, Frundlich and Tmkin modls wr applid o dscrib h biosorpion isohrm of h mal ions by Srpomycs rimosus biomass. Langmuir modl fid h quilibrium daa br han h Frundlich isohrm. Maximum mal upak q max was obsrvd as mg g indica good biosorbns han ohr biomass. xprimnal daa wr also sd in rms of biosorpion kinics using fracional powr, lovich, psudo-firs ordr and psudo-scond ordr ra xprssions. Th rsuls showd ha h biosorpion procsss followd wll psudoscond-ordr kinics and h inra-paricl diffusion is no h ra-limiing sp for h whol racion. Ky words: Biosorpion, Chromium (III), Isohrms, Kinics, Srpomycs rimosus INTRODUCTION Trivaln chromium is vacuad o h nvironmn by h ffluns of a larg numbr of indusris such as mining, iron sh claning, chrom plaing, lahr anning and wood prsrvaion (Krishna & Philip, 005). Th maximum lvls prmid in waswar ar 5 mg/l for rivaln and 0.05 mg/l for hxavaln chromium (Richard and Bourg, 99). Alhough chromium (III) is an ssnial lmn, i can b oxic a lvad concnraions in h nvironmn. Cr (III) is slcd insad of Cr (VI) bcaus of following facs Cr (III) is oxic if xcss quaniy is akn and caus abnormaliis in organisms. Chromium (III) sulpha sals ar mainly usd in anning (Man al., 005). *Corrsponding auhor -mail:sahmoun63@yahoo.fr Th rmoval of chromium mploying convnional mhodologis (Tiranvani al., 997) lik ion xchang, chmical prcipiaion or rvrs osmosis suffr from limiaions lik high opraing cos, incompl prcipiaion, sludg gnraion, c. On h ohr hand biosorpion is rciving incrasing anion as an mrging chnology for h rmoval of havy mals from conaminad ffluns (Kumari al., 006). Th procss is basd on h adsorpion bhaviour of crain biological marials owards organic or inorganic subsancs from hir soluion. Fungal biomass and sawd biomass hav bn found o b xclln biosorbns for squsring havy mals (Lwis and Kiff 988, Holan and Volsky 994, Volsky and Holan 995). 9

2 Sahmoun, M.N. al. Fungal biomass has bn usd o squsr coppr, lad, zinc, nickl, cadmium, gold, silvr and various acinid lmns, such as horium, uranium and pluonium (Tszos and Volsky 98, Gadd and Whi 989, Luf al., 99, Kapoor and Viraraghavan 995, Myr and Wallis 997, Kapoor and Virraghavan 998). Srpomycs rimosus, myclial bacrium is classifid Gram-posiiv. In gnral, Gram-posiiv bacria hav a grar sorpiv capaciy du o hir hickr layr of ppidoglycan which conains numrous sorpiv sis (Van Hullbusch al., 003).Mal rmoval ramn sysms using micro-organisms is a chap and pracical alrnaiv o convnional procsss, sinc low cos sorbn marials ar usd. Micro-organisms basd chnologis mus comp wih boh opraional and conomical rms in xising mal rmoval ramn sysms. Non-living biomass appars o prsn spcific advanags in comparison o h us of living micro-organisms (Özürk al., 004). Th objciv of h prsn work is o invsiga h biosorpion ponial of Srpomycs rimosus biomass in h rmoval of Cr (III) ions from aquous soluion. An opimum biosorpion condiion was drmind as a funcion of ph. Th Langmuir, Frundlich and Tmkin modls wr usd o dscrib quilibrium isohrms. Various kinic modls wr sd o dscrib h sorpion daa and dsorpion procsss wr also invsigad o facilia mal rcovry.th sudy of adsorpion dynamics dscribs h solu upak ra. This ra conrols h rsidnc im of adsorba upak a h solid soluion inrfac. Th kinics of chromium biosorpion on dad biomass wr analyzd using Fracional powr (Basha, and Murhy, 007), psudo-firs-ordr (Ho, 004)., lovich (Ho, 006), psudo-scond-ordr (Ho, 006), and inra-paricl diffusion (Wbr and Morris, 963) kinics modls.th sorpion kinics is dscribd by powr funcion modl as follows: q = k ν () Whr q is h amoun of chromium mg/g sorbd a im and ν h ra consan of powr funcion (min - ). k is consan of powr funcion modl (mg/g).quaion () can b rarrangd o obain quaion (), which has a linar form: ln q = ln k + ν ln () Th plo ln q and ln should giv linar rlaionship from which ν and k can b drmind from h slop and inrcp of h plo, rspcivly.th psudo-firs ordr kinic ra quaion is xprssd as: dq = k ( q q) (3) d Whr k is h ra consan of psudo firs ordr adsorpion (min - ), q is h amoun of chromium sorbd a quilibrium (mg/g) and q h amoun of chromium sorbd a im (mg/g). Ingraing quaion (3) for h boundary condiions =0 o = and q =0 o q = q and rarranging yilds h linar im-dpndn funcion. k log ( q q) = log q (4).303 Th inrcp of h sraigh-lin plos of log ( q q) agains should quallog q. Howvr, if h inrcp dos no qual q, hn h racion is no likly o b firs-ordr, irrspciv of h magniud of h corrlaion cofficin.th psudo-scond- ordr kinic ra quaion is xprssd as: dq = k ( ) q q d (5) Whr k is h ra consan of psudo scond ordr adsorpion (g.mg -.min - ). Taking ino accoun, h boundary condiions =0 o = and q =0 o q = q. Th ingrad form of quaion (5) can b rarrangd o obain quaion 6. = + (6) q k q q Th iniial adsorpion ra h (mg.g -.min - ) is xprssd as: h= k q (7) 30

3 In. J. nviron. Rs., 3():9-38, Spring 009 Th plo of (/ q ) and of quaion (6) should giv a linar rlaion ship from which q and k can b drmind from h slop and inrcp of h plo, rspcivly.th lovich modl quaion is gnrally xprssd as: dq = axp( βq) (8) d Whr a is h iniial adsorpion ra (mg/g.min - ). β is h dsorpion consan (g.mg - ) during any on xprimn. To simplify h lovich quaion h auhors (Chin and. Clayon, 980) assumd aβ >> and by applying h boundary condiion q = 0 a =0 and q = q a =. quaion (8) bcoms: ln a q = β ln β + (9) β If Chromium biosorpion fis h lovich modl, a plo of q vrsus ln should yild a linar rlaionship wih a slop of / β and an inrcp of ln a β / β.th inra-paricl diffusion modl prsnd hr rfrs o h hory proposd by h auhors (Wbr and Morris, 963), who concludd ha h upak is proporional o h squar roo of conac im during h cours of adsorpion. Accordingly: q 0.5 = Kp (0) Whr K p is h inra-paricl diffusion ra consan (mg/g.min 0.5 ) quilibrium daa, commonly known as adsorpion isohrms, ar h basic rquirmn for h dsign of adsorpion sysms. Classical adsorpion modls, such Langmuir (96), Frundlich (906) and Tmkin (940) modls wr usd o dscrib h quilibrium bwn adsorbd chromium on h biomass and chromium in soluion ( C ) a consan mpraur.th Frundlich isohrm is a non linar sorpion modl. This modl proposs a monolayr sorpion wih a hrognous nrgic disribuion of aciv sis, accompanid by inracion bwn adsorbd molculs. Th gnral form of his modl is: q n KFC = () () Whr K F is h xn of h adsorpion and n h dgr of non-linariy bwn chromium concnraion and adsorpionquaion () can b linarizd in logarihmic form and h Frundlich consans can hn b drmind: ln q = ln KF + ln C () () n Th Langmuir quaion which is valid for monolayr sorpion on a surfac wih a fini numbr of idnical sis, is givn by: C C = + (3) q bq q max max q max is aribuabl o h maximum mal upak upon compl sauraion of h sorbn, and b is a cofficin aribud o h affiniy bwn h sorbn and sorba. q max and b can b drmind from h linar plo C / q vrsusc.th ssnial characrisic of h Langmuir isohrm can b xprssd in rms of dimnsion lss consan sparaion facor for quilibrium paramr R L (Hall and. Vrmylm, 966), which is dfind by: R = L b C (4) + 0 Hall and Vrmylm (966) show, using mahmaical calculaion, ha h paramr R L indicas h shap of isohrm as follows (Tabl ). Tabl. Consan paramr R L R L Valu Typ of isohrm R L f unfavourabl R L = linar R L = 0 Irrvrsibl 0 p R L p favourabl Tmkin (940) modl was also usd. This isohrm was firs dvlopd by Tmkin and Pyzhv, and i is basd on h assumpion ha h ha of adsorpion would dcras linarly wih h incras of covrag of adsorbn [30]. 3

4 Biosorpion of Cr (III) from Aquous Soluions q RT = ln( ac ) (5) b Whr R is h gas consan, T h absolu mpraur in Klvin, b h consan rlad o h ha of adsorpion and a is h Tmkin isohrm consan. quaion (5) can b rarrangd o obain quaion (6): RT ln a RT q = ln C b + b (6) MATRIALS & MTHODS Th dad Srpomycs rimosus biomass was obaind from h SAIDAL-complx manufacuring uni of anibioics Mda-Algria Th biomass was washd wih dionisd war, drid a 50 C for 4 h in a drying ovn, hn h acivad biomass was prpard by raing h raw biomass wih 0. N NaOH soluion for 30 min a ambin mpraur, a onc again washd, drid and hn scrnd hrough a s of sivs o g gomrical siz µm. Th fflun usd in h xprimn was h dp blu colour characrisic of Cr (III) and had a ph of 4. Chromium conn, as drmind by aomic absorpion spcroscopy, was found o b.4 g/l. No Cr(VI) was prsn in h fflun as indicad by phnylcarbazid sing. Sodium concnraion was 30 g/l. Conrol xprimns confirmd ha no signal inrfrnc occurrd bwn h wo mals. Chromium upak srial diluions of h anning fflun wr prpard using dionisd disilld war o giv soluion ranging in concnraion from full srngh o in 40 diluions. Aliquos of 00 ml wr conacd wih 0.3 g quaniis of Srpomycs rimosus biomass. Sampls wr filrd (0.45 µm filrs) and h filras wr analysd for rmaining mals using a Prkin lmr 380 aomic absorpion spcromr. Th amoun of Chromium accumulad by biomass was calculad as h diffrnc bwn h amoun prsn in h iniial soluion and ha in h final soluion afr quilibraion wih biomass using h following formula (Holan and Volsky, 994). q ( C ) V C 0 = (7) m All xprimns wr conducd a a consan mpraur of 0 ± C o b rprsnaiv of nvironmnally rlvan condiions. Kinic xprimns wr conducd on a roary shakr wih consan agiaion spd of 300 rpm; using conical flasks (50 ml) conaining 00 ml of soluion and 0.3 g of biomass and an iniial ph 4.8 wih iniial concnraion of 400 mg l for 80 min. To avoid shifs in ph du o biomass addiion, h ph was adjusd wih 0.N HCl or N NaOH afr h soluion had bn in conac wih h biosorbn. For sorpion isohrm xprimns, flasks wr agiad on a roary shakr (300 rpm) unil no addiional mal was rmovd (5 h). Th sampls wr filrd hrough 0.45 µm millipor filrs and wr akn priodically o analys h chromium concnraion.to mak h biosorpion procss mor conomical, i would b ncssary o rgnra h spn biosorbn.to valua h dsorpion fficincy h Chromium loadd biomass was drid a 60 C for 4 h afr quilibrium sorpion a ph 4.8. Th drid biomass was conacd wih M H or M HCl for 4 h o allow chromium o b rlasd from h biomass, hr afr, h dsorbd chromium was analysd and dsorpion fficincy was calculad as follows (Choi. and Yun, 004): Dsorpion fficincy (%) = rlasd chromium (mg) *00 (8) iniially sorbd chromium (mg) All h modl paramrs wr valuad by non-linar rgrssion using xcl 007 sofwar. Th opimizaion procdur rquirs an rror funcion o b dfind in ordr o b abl o valua h fi of h quaion o h xprimnal daa (Ho al., 00, Kundu, and Gupa, 006). Apar from h corrlaion cofficin (R ), h rsidual roo man squar rror (RMS) and h chi-squar s wr also usd o masur h goodnss-of-fi. RMS can b dfind as: m RMS = ( q ) i qi m (9) i= Whr h obsrvaion from h bach xprimn is q i, q i is h sima from h isohrm for corrsponding q i and m is h numbr of obsrvaions in h xprimnal isohrm. Th 3

5 In. J. nviron. Rs., 3():9-38, Spring 009 smallr RMS valu indicas h br curv fiing Tsai and Juang, 000). Th chi-squar s can b dfind as: m ( ) qi qi χ = (0) i= qi If daa from modl ar similar o h xprimnal daa, χ will b a small numbr (Ho al., 005). RSULTS & DISCUSSION Th ph of h mal soluion usually plays an imporan rol in h biosorpion of mals (Vijayaraghavan al., 005). As can b sn in (Fig. ). h upak of Cr 3+ by Srpomycs rimosus biomass was obaind by varying h iniial concnraion of chromium. Whn h ph valu was raisd from o 4.8, h adsorpion capaciy was nhancd significanly from 7 o 64 mg/g biomass. Upak was nhancd, probably bcaus of proon compiion o Cr 3+ binding (Yun and Volsky, 003),Adsorpion a ph 5.5 markd prcipiaion ffcs augmnd h biosorpion rmoval of chromium, from soluion rsuling in apparn squsraion lvls of in xcss of 93 mg/g as illusrad in fig.. As can b sn in h figur, whn h prcipiaion componn is subracd h n biosorpion valus ar in good agrmn wih ach ohr and hos obsrvd a ph 4.8 (Tobin and Roux, 998). If h biosorpion aks plac undr condiions ha chromium may prcipia, a chmical sludg is gnrad which should b rad via appropria solid was managmn mhods. From a pracical poin of viw, hrfor, chromium biosorpion procss is br oprad a ph Upak (mg/g) Final chromium concnraion(mg/l) Fig.. ffc of ph and influnc of prcipiaion on upak (* indica whr prcipiaion ffcs hav bn subracd) Th bach xprimnal daa, shown in (Figs. & 3) on kinic and quilibrium sudis for h biosorpion of Cr (III) on Srpomycs rimosus wr sd o fi h various kinic and quilibrium modls, rspcivly As shown in (Fig. ). h rmoval of chromium incrass rapidly in h bginning (firs 30 min) and han mor slowly unil h quilibrium (min) Fig.. Kinic (biosorpion capaciy vs. im) of Cr (III) on Srpomycs rimosus (mg/g) q (mg/g) q C (mg/l) Fig. 3. Biosorpion isohrm for Cr (III) on Srpomycs rimosus As sn in (fig.3). i radily appars ha, isohrm is somwha curvd and h quilibrium is sablishd bwn chromium ions and h biomass Th mal-binding propris of Gramposiiv bacria ar largly du o h xisnc of spcific anionic polymrs in h cll wall srucur, consising mainly of ppidoglycan, ichoic acids (Hancock, 986, Hughs and Pool, 989, Rmacl al., 99). Du o his high fixd anionic conn of h cll forms which ar obviously prsn in Srpomycs rimosus, hy may xhibi high sorpion capaciis ha would b vry imporan aspc in fuur bcaus of is indusrial applicaion as biosorbn for h mal 33

6 Sahmoun, M.N. al. caions.a simpl kinic analysis of biosorpion of Cr (III) on Srpomycs rimosus has bn sd according o fracional powr modl (Basha, and Murhy, 007) and Tabl shows h simad paramrs of h modl. Th rsuls indica ha h powr funcion modl dscribd h imdpndn Cr (III) on sorbn as h valu of consan v was lss han (Basha, and Murhy, 007). Th chromium biosorpion daa do no corrla wll wih fracional powr modl and his confirmd by high RMS and chi-squar valus (Tabl ). Th kinic consan, k,, of h psudo-firsordr quaion (Ho, 004) for h biosorpion of Cr (III) on o biomass is givn in (Tabl ). Th rsuls dmonsrad ha Lagrgrn modl (Ho, 004) is no applicabl in h prsn cas as high RMS and chi-squar valus wr obsrvd. Th kinic consans obaind from h lovich quaion (Ho, 006) ar lisd in (Tabl ). Th rsuls dmonsra a significan rlaionship bwn Cr (III) sorbd, q and in his sudy wih accpabl rgrssion cofficin 0.95 and low valus of RMS and chi-squar. Th low valus of sandard rror rflc agrmn bwn h ss of daa sudid. In ohr words, h daa also show saisfacory complianc wih h lovich quaion.th rsuls in (Tabl ) show h biosorpion ra consan, k, iniial biosorpion ra, h, and quilibrium biosorpion capaciy, q, of h psudo-scond-ordr modl (Ho, 006). Ths rsuls show a vry good complianc wih h psudo-scond-ordr quaion wih high rgrssion cofficins (>0.99).Th ra of a biosorpion racion nonlinarly dcrasd wih im. For xampl, h insananous ras a 50 and 90% of Cr (III) biosorpion (SR 50 and SR 90, rspcivly) can b calculad from psudoscond ordr ra quaion as follows: kq h SR50 = k q ( 0.5 q) = = () ( ) 4 4 kq h SR90 = k q ( 0.9 q) = = () ( ) Thrfor, SR 50 and SR 90 valus ar onfourh and on-hundrdh of iniial biosorpion ra, h, rspcivly (s Tabl5), and comparisons rpord hr basd on h valus can b xndd o h nir xprimn duraion.basd on h psudo-scond-ordr kinic modl h half-lif of Cr (III) biosorpion (h im a which half of h biosorpion procss is compld) dircly dpnds on h biosorpion capaciy of h biosorbn and invrsly rlas o h iniial biosorpion ra: q = = (3) kq h Biosorpion capaciy of h biosorbn drmind from h fid psudo-scond-ordr kinic modl was comparabl o h maximum biosorpion capaciy calculad from h Langmuir isohrm as can b sn lar. Tabl. Kinic modl paramrs for Cr (III) biosorpion on Srpomycs rimosus Modls Fracionalp owr lovich psudofirs-ordr psudoscondordr Paramrs ν ( k ( - min ) mg.g ).434 R 0.96 RMS χ.09 k ( min ) mg. g ) 4.5 R q ( a ( RMS χ 6 - mg. g min ) g.mg ) β ( R RMS 3.4 χ.06 - k ( g.mg min ) q ( h ( mg.g ) mg.g ). - SR ( mg.g ) SR 90 ( mg.g ) 0. ( min ) 6.43 R RMS.035 χ

7 In. J. nviron. Rs., 3():9-38, Spring 009 Th inraparicl diffusion cofficin for h biosorpion of Cr (III) was calculad from h slop of h plo (Fig.4). bwn h amouns of Cr (III) sorbd, q (mg/g) vs. / (min / ). Basd on his plo, h biosorpion procss of h Cr (III) is comprisd by wo phass, suggsing ha h inraparicl diffusion is no h ra-limiing sp for h whol racion (Ho and Ofomaja,, 005), h iniial porion of h plo indicad an xrnal mass ransfr whras h scond linar porion is du o inraparicl or por diffusion. Similar rsuls wr rpord by h auhors (Aguilar- Carrillo al., 006). Th inrcp of h plo provids an simaion of h hicknss of h boundary layr (Oubagaranadin al., 007).Th slop of h scond linar porion of h plo has bn idnifid as h inra-paricl diffusion ra consan (K P =,90 mg/g min -/ ). Th high valu of K p corrspondd o low valu of psudoscond ordr ra consan, k (Tabl ), indicaing ha h inra-paricl diffusion rards h biosorpion procss. This also indicas, h biosorpion procss is rahr complx and involvs mor han on diffusiv mchanism. (mg/g) q / (min / ) Fig. 4. Inra-paricl diffusion plos for h biosorpion of Cr (III) on Srpomycs rimosus Analysis of quilibrium daa is imporan for dvloping an quaion ha can b usd o dsign and opimiz an opraing procdur. To xamin h rlaionship bwn biosorpion and aquous concnraion a quilibrium, various biosorpion isohrm modls ar widly mployd for fiing h daa.th Tmkin modl paramrs ar compard wih valu for h Langmuir and Frundlich modl in (Tabl 3). Th Frundlich isohrm is originally mpirical in naur (Frundlich,906), bu was lar inrprd as biosorpion o hrognous surfacs or surfacs supporing sis of varid affiniis and has bn usd widly o fi xprimnal daa (Aksu and Kusal, 99). Th valu of n, of his modl, falling in h rang of 0 indicas favourabl biosorpion (Aksu, 00). Th numrical valu of /n < indicas ha adsorpion capaciy is only slighly supprssd a lowr quilibrium concnraions. This isohrm dos no prdic any sauraion of h adsorbn by h adsorba. Thus infini surfac covrag is prdicd mahmaically, indicaing mulilayr adsorpion on h surfac (Hasany al., 00).Th prsn sudy rsuls indica ha h Frundlich modl dos no fi h xprimnal daa wll. I is no h suiabl modl for dscribing hs biosorpion procsss, as RMS and χ valus ar highr han 0. Tmkin modl is unabl o dscrib h daa, as low corrlaion cofficins and high RMS and chi-squar valus wr obsrvd.th adsorpion daa providd an xclln fi o h Langmuir isohrm wih high valus of h R (s Tabl3). Th sparaion facor (R L ) valu indicas ha Cr (III) biosorpion of biosorbn in his sudy is favourabl.comparisons of maximum xprimnal biosorpion capaciis of Cr (III) for som biomasss wr also givn in (Tabl 4). I can b sn from h abl, Srpomycs rimosus usd in his sudy has high biosorpion capaciy. To mak h adsorpion procss mor conomical i is ncssary o rgnra h spn adsorbn. In his sudy, h chromium baring biomass was conacd wih hydrochloric acid or sulphuric acid (Fig. 5).Whn a low ph was usd h dsorpion fficincy was 95 %. A ph valus of 0.5 and.0 only 66 and 5 % chromium was rcovrd rspcivly.chromium dsorpion incrasd wih dcrasing dsorpion agns ph (including HCl and H ) o a maximum valu of Cr 95% a approximaly zro ph.variaion of h hydrochloric acid or Sulphuric acid causd nondiffrnc in dsorpion ovr h xprimnal rang invsigad as shown in (fig.5). 35

8 Biosorpion of Cr (III) from Aquous Soluions Tabl 3. Isohrm consans for Cr (III) biosorpion on Srpomycs rimosus quilibrium modls Frundlich Tmkin Langmuir Paramrs - KF ( lg ).74 n.443 R RMS χ.69 - a T (lg ) b ( jmol ) 97.7 T R RMS χ 5.97 q (. ) max mgg b ( l.mg ) R L 0.3 R 0.99 RMS.009 χ.067 Tabl 4. Comparison of biosorpion capaciy of Srpomycs rimosus biomass wih ha of diffrn biomasss Biosorbn q ph Rfrnc Chlorlla miniaa Carro rsidus Parmlina iliaca Sphroidal cllulos spirogyra spcis Sargassum SP Srpomyc s rimosus max Han al., (006) Nasrnjada al., (005) Uluozlu al., (008) Liu al., (00) Bishnoi al., (007) Cossich al., (004) h prsn sudy Dsorplon Dsorbn H Dsorbn HCl ph Fig. 5. ffc of dsorpion agns (H, HCl) ph on dsorpion fficincy CONCLUSIONS Th prsn sudy showd ha Srpomycs rimosus a biological sorbn of myclial bacria origin can find an applicaion as a biological sorbn of Cr (III) ions from aquous soluion. Th procss kinics was found o follows h psudo-scond ordr ra quaion. Langmuir modl prsns good fis of h xprimnal daa. Th applicaion of his modl o complx biological sysm may no o xplain h biosorpion bhaviour. Hnc, conclusion drivd only from good fi of h modl should b avoidd. Th mal ion could b srippd by addiion of HCl or H a low ph, making h adsorbn rgnraion and is ruilizaion possibl. RFRNCS Aguilar-Carrillo, J., Garrido, F., Barrios, L.and Garcýa- Gonzalz, M.T. (006). Biosorpion of As, Cd and Tl as influncd by indusrial by-producs applid o an acidic soil: quilibrium and kinic xprimns, Chmosphr, 65, Aksu, Z. (00). Drminaion of h quilibrium, kinic and hrmodynamic paramrs of h bach biosorpion of nickl (II) ions ono Chlorlla vulgaris Proc. Bio., Aksu, Z.and Kusal, T. (99).A biosparaion procss for rmoving lad(ii) ions from was war by using C. vulgaris, J. Chm. Tchnol. Biochnol., 5, Basha, S. and Murhy, Z.V.P. (007).Kinic and quilibrium modls for biosorpion of Cr (VI) on chmically modifid sawd cysosir indica. Proc.bio., 4(),

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