Equilibrium sorption of divalent metal ions onto groundnut (Arachis hypogaea) shell: kinetics, isotherm and thermodynamics

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1 ISSN: Babarind Chmisry and Onyiaocha Inrnaional / Chmisry 2(1) (2016) Inrnaional (1) (2016) iscinic.org. Equilibrium sorpion of divaln mal ions ono groundnu (Arachis hypogaa) shll: kinics, isohrm and hrmodynamics Adsola Babarind 1 and Gloria Ogonna Onyiaocha 2 1 Dparmn of Chmical Scincs, Olabisi Onabanjo Univrsiy, Ago- Iwoy, Nigria 2 Applid Scinc Laboraory, Fdral Collg of Fishris and Marin Tchnology, Lagos, Nigria *Corrsponding auhor s E. mail: adsola.babarind@oouagoiwoy.du.ng, solababarind@yahoo.com, Tl: A R T I C L E I N F O A B S T R A C T Aricl yp: Rsarch aricl Aricl hisory: Rcivd July 2015 Accpd Augus 2015 January 2016 Issu Kywords: Groundnu shll Pb(II) Cd(II) Zn(II) Biosorpion Isohrm Kinics Thrmodynamics Th quilibrium, kinics, and hrmodynamics of h biosorpion of Pb(II), Cd(II) and Zn(II) ono groundnu (Arachis hypogaa) shll wr invsigad undr various physicochmical paramrs. Opimisaion sudis wr carrid ou using bach biosorpion sudis. Th xn of h mal ion biosorpion incrasd wih incras in soluion ph, iniial mal ion concnraion, dosag of biosorbn and conac im bu dcrasd wih h mpraur of h sysm. Th biosorpion of ach of h mal ions was found o b ph-dpndn. Kinic sudy showd ha h mal ions biosorpion procss followd h psudo-scond-ordr kinic modl. Th sorpion of ach mal ion was analysd wih Frundlich and Langmuir isohrm modls, in ach cas, h quilibrium daa wr br rprsnd by Frundlich isohrm modl. Thrmodynamically, paramrs such as sandard Gibbs fr nrgy ( G ), sandard nhalpy ( H ), sandard nropy ( S ) and h acivaion nrgy (A) wr calculad. Th biosorpion of ach mal ion was sponanous and h ordr of sponaniy of h biosorpion procss bing Cd(II) > Zn(II) > Pb(II). Similarly, chang in nropy was obsrvd for ach and h ordr of disordr is Cd(II) > Zn(II) > Pb(II) Inrnaional Scinific Organizaion: All righs rsrvd. Capsul Summary: Groundnu shll was invsigad for h sorpion of Pb(II), Cd(II) and Zn(II), procss variabls wr opimizd, sorpion daa was subjcd o kinic and isohrm modls and hrmodynamic sudis wr also prformd. Rsuls showd ha groundnu shll has high fficincy in h sorpion of Pb(II), Cd(II) and Zn(II) and could possibly b usd for raing waswar conaining hs mal ions. Ci This Aricl As: Adsola Babarind and Gloria Ogonna Onyiaocha Equilibrium sorpion of divaln mal ions ono groundnu (Arachis hypogaa) shll: kinics, isohrm and hrmodynamics. Chmisry Inrnaional 2(1) INTRODUCTION Havy mal polluion in aquaic nvironmn has bcom a sourc of gra concrn. In naural aquaic cosysms, mals occur in low concnraions bu in rcn ims, h occurrnc of mals in xcss of naural loads has bcom a problm of incrasing concrn. This siuaion has arisn as a rsul of indusrializaion and urbanizaion (Hanan al., 2010). Th incrasd indusrializaion rsuls in h rlas of varid yps and amouns of indusrial wass ino h nvironmn. Ths indusrial wass consis of svral classs of polluans including havy mals. Apar from indusrial aciviis, ohr sourcs of havy mals ino h nvironmn includ unrad domsic ffluns, agriculural wass, discharg from swag ramn works, urban sorm-war run-off, laching of mals from garbag and solid wass dump (Bilal al., 2014; Iqbal al., 2013; Iqbal and Bhai, 2014, 2015; Iqbal and Khra, 2015; Iqbal 37

2 and Nisar, 2015; Manzoor al., 2013; Qurshi al., 2015; Ullah al., 2013). Havy mals ar imporan sourc of polluion no jus bcaus hy ar oxic abov a rlaivly low concnraion bu also bcaus hy ar prsisn, rmaining in h nvironmn long afr h sourc of polluion has bn rmovd ha is, hy do no biodgrad ino harmlss nd produc. Biosorpion, a procss whrby crain yps of inaciv, dad biomass may bind and concnra havy mals from aquous soluions is considrd an alrnaiv chnology for rmoval of oxic havy mals from was war and indusrial ffluns (Kawsam and Yu, 2001; Romro-Gonzalz al., 2001; Yu al., 2001; Al- Subu, 2002; Skhar al., 2004; Naja al., 2005; Sad al., 2005; Wankasi al., 2005; Doyurum and Clik, 2006; Dng al., 2007; Uluozolu al., 2007, 2008, 2010; Babarind al., 2008; Qaisr al., 2009; Opolu al., 2010). Th main advanag of using biosorpion chnology is h cos ffcivnss of h biosorbns, sinc hy may b drivd from various chap and abundanly availabl biological raw marials. Ohr advanags includ compiiv prformanc, havy mal slciviy, no sludg gnraion, rusabiliy of biomarial, improv slciviy of spcific mals of inrs and shor opraion im (Babarind al., 2009; Sari al., 2007). In his sudy, groundnu shll was invsigad as a biosorbn for h upak of Pb(II), Cd(II) and Zn(II) from soluion. Groundnu (Arachis hypogaa) is a plan ha is grown across h world for is high nuriional valu. I is widly us as mal and snacks bcaus of is high proin conn. Howvr, h shll is unuilizd, hrby bcoming nvironmnal nuisanc. I is found o conain abundan funcional groups such as hydroxyl, amin and carboxyl groups which conain lon pairs of lcrons ndd for biosorpion of caionic polluans in soluion. I was on his basis ha his radily availabl agriculural was was invsigad for is ponial in raing fflun conaining Pb(II), Cd(II) and Zn(II). Prvious sudis on groundnu biomass includ valuaion of h adsorpiv capaciy of panu hull plls for havy mals in soluion (Brown al., 2000) and h rmoval of havy mals from soluion using groundnu husk (Okiimn al., 1991). Ohr sudis includ biosorpion of Pb(II) and Cr(VI) on groundnu hull (Qaisr al., 2009), h us of acivad carbon prpard from groundnu shll for h sorpion of malachi grn dys (Malik al., 2007). W hav rcnly invsigad h biosorpion of Ni(II), Cr(III) and Co(II) wih groundnu shll (Babarind al., 2012) and found h sorbn vry ffciv hnc h nd o xnd h sudy o ohr mal ions ha conamina h nvironmn. Thrfor, in prsn invsigaion, groundnu shll fficincy for h adsorpion Pb(II), Cd(II) and Zn(II) was valuad. Prparaion of soluion All chmicals (BDH, England) usd in his sudy wr of analyical ragn grad and wr usd wihou furhr purificaion. Sandard soluions of Pb(II), Cd(II) and Zn(II) usd for h sudy wr prpard from Pb(NO 3 ) 2, 3CdSO 4.8H 2 O and Zn(NO 3 ) 2.6H 2 O, rspcivly. Th working soluions wih diffrn concnraions of h mal ions wr prpard by appropria diluions of h sock soluion prior o hir us wih disilld war. Th iniial ph of h soluion was adjusd accordingly wih a ph mr (Horiba F-11) o bwn 1.0 and 6.0. Thrmosad war bah (AdvancLB240) was usd as h mdium for h procss. Th concnraion bfor and afr biosorpion of ach mal ion was drmind using a Prkin- Elmr Analys 700 flam aomic absorpion spcrophoomr. Characrizaion of biomass Fourir ransform infrard (FT-IR) spcra of drid unloadd biomass and mal loadd biomass wr rcordd a 400 o 4000 cm -1 using a Shimadzu FT-IR modl 8400S spcrophoomr. Biosorpion xprimns Bach quilibrium biosorpion sudis wr carrid ou by conacing 0.5 g of h groundnu shll wih 25 ml of h mal ion soluion undr diffrn condiions for a priod of im in a boiling ub. Th biosorpion sudis wr conducd a 28 C using hrmosad war bah (AdvancLB240) o drmin h ffc of ph, biomass dosag, conac im, iniial mal ion concnraion and mpraur on h biosorpion. Th iniial ph of h soluion was adjusd accordingly wih a ph mr (Horiba F-11). Th amoun of mal ion biosorbd from soluion was drmind by diffrnc and h man valu was calculad. Effc of ph on biosorpion Th ffc of ph on h biosorpion of h mal ion was carrid ou wihin h rang ha would no b influncd by h mal prcipiad. This was don by conacing 0.5 g of groundnu shll wih 25 ml of 100 mgl -1 mal ion soluion in a boiling ub wihin h ph rang of 1 o 6. Th ph of ach soluion was adjusd o h dsird valu by drop wis addiion of 0.1 M HNO 3 and/or 0.1 M NaOH. Th boiling ubs conaining h mixur wr mainaind in a war bah for 2 h. Th biomass was rmovd from h soluion by dcanaion. Th rsidual mal ion concnraion in h soluion was analyzd. Th opimum ph was drmind as h ph wih h highs biosorpion of ach mal ion. MATERIALS AND METHODS Prparaion of biosorbn Groundnu (Arachis hypogaa) was obaind from Kuj mark, Abuja, Nigria. Th shlls wr proprly rinsd wih war, sun drid immdialy and kp dry in an air igh polyhn bag unil im of usag. Effc of biosorbn dosag Effc of biosorbn dosag was invsigad using an iniial mal ion concnraion of 100 mgl -1. Biosorbn masss usd for h sudy wr wihin h rang g. Th sudy was carrid ou a h mpraur of 28 C and a ph 5. Th conac im for his xprimn was 2 h. 38

3 Effc of conac im on biosorpion Th biosorpion of h mal ions by groundnu shll was sudid a various im inrvals (0-300 min) and a a concnraion of 100 mg/l. This was don by conacing 2 g of groundnu shll wih 25 ml of 100 mgl -1 of mal ion soluion in a boiling ub a ph 5 and mpraur of 28 C. Th shll was lf in h soluion for diffrn priods of im. Th soluion in h boiling ub was dcand a diffrn im inrvals from h firs o h las ub. Each aliquo was analysd for rsidual mal ion concnraion using aomic absorpion spcrophoomr. Th amoun of mal ions biosorbd was calculad for ach sampl. Effc of iniial concnraion on biosorpion Bach biosorpion sudy of mal ion was carrid ou using a concnraion rang of 10 o 100 mgl -1. This was don by inroducing 2 g of h groundnu shll ino 25ml mal ion soluion in h boiling ubs mployd a ph 5. Th ubs wr mainaind in a hrmosad war bah mainaind a 28 C for 2 h. Th groundnu shll was rmovd from h soluion by dcanaion and h concnraion of rsidual mal ion in ach soluion was drmind. Effc of mpraur on biosorpion Th bach biosorpion procss was sudid a diffrn mpraurs of 20 o 50 C in ordr o invsiga h ffc of mpraur on h biosorpion procss. This was don by conacing 2 g of groundnu shll wih 25 ml of 100 mgl -1 of mal ion soluion a h ph 5. Th biosorpion of mal ion may involv chmical bond formaion and ion xchang sinc h mpraur is a main paramr affcing hm. Saisical Analysis Th curv fiings of h daa obaind wr prformd using Microcal Origin 6.0 sofwar. RESULTS AND DISCUSSION FT-IR sudis of h fr and mal-bound groundnu shll Th FT-IR spcra of drid unloadd, Pb-loadd, Cd-loadd and Zn-loadd groundnu shll wr akn wih FT-IR spcrophoomr. Th spcra giv informaion on h naur of possibl inracions bwn h funcional groups of groundnu shll biomass and h mal ions as prsnd in Figurs 1. Th IR spcra parn of h biomass showd disinc and sharp absorpions indicaiv of h xisnc of h OH, -NH, and -C- O- groups. Ths bands ar du o h funcional groups of groundnu shll ha paricipad in h biosorpion of Pb(II), Cd(II) and Zn(II). On comparison, hr ar clar band shifs and dcras in innsiy of bands as rpord in Tabls 1. Th FT-IR spcra of h groundnu shll biomass indicad sligh changs in h absorpion pak frquncis du o h fac ha h binding of h mal ions causs rducion in absorpion frquncis. Ths shifs in absorbanc obsrvd imply ha hr wr mal binding procsss aking plac on h aciv sis of h biomass. Analysis of h FT-IR spcra showd h prsnc of ionizabl funcional groups which ar abl o inrac wih caions (Pradhan al., 2007; Buno al., 2008; Sun al., 2008; Erugay and Bayhan, 2008; Uluozlu al., 2008). This implis ha hs funcional groups would srv in h rmoval of posiivly chargd ions from soluion. Effc of soluion ph on mal ion biosorpion Th ph of h soluion has bn sablishd o b a vial paramr in biosorpion procss (Sun al., 2008; Babarind al., 2009). Th n charg of h sorba and ha of h sorbn ar dpndn on h ph of h soluion. A low ph, h mal ion upak is inhibid by n posiiv charg on h sorbn and h compiion bwn h mal ions and hydrogn ions in soluion. Th xprimns wr no conducd abov ph 5.0 o avoid possibl prcipiaion of hydroxid, spcially wih Pb(II). As h ph incrass, h ngaiv charg dnsiy on biomass incrass as a rsul of dproonaion of h mal binding sis on h shll, consqunly, h biosorpion of h mal ions incrass. Th biosorpion capaciy incrasd wih incrasing ph and h ffc of ph was in h ordr Pb(II) > Zn(II) > Cd(II). A similar ordr has bn rpord for h sorpion of Pb(II), Cu(II) and Cd(II) by brwry biomass ( Kim al., 2005). This ffc of ph on h biosorpion capaciy can b xplaind as h rsul of compiion of h hydronium ions and mal ions for h availabl binding sis. Figur 2 shows h variaion of h mal ion biosorbd on groundnu shll a various soluion ph valus. In ach cas, h biosorpion incrasd sadily as h ph incrasd from ph 1. Th incras in biosorpion wih incras in ph implis ha ion-xchang procss is involvd. Th racion involvd h biosorpion of mal ion (rprsnd as M x+ for a mal ion) from h liquid phas o h solid phas, h biosorbn wih lon pair of lcrons (rprsnd as Ä), and can b considrd as a rvrsibl racion wih an quilibrium bing mad bwn h wo phass as schmaically shown in Equaion 1 for a divaln mal ion in h soluion: Ä + M 2+ A-M (1) Th rvrsibiliy of h biosorpion procss is obsrvd whn h mal-bound biomass is rad wih dilu HNO 3 which is a dsorpion procss. I was obsrvd in ach cas ha opimum ph was obaind a ph5, his was hn usd as h opimum ph for subsqun sudis in h invsigaion of h ffc of ohr physicochmical paramrs. Effc of biomass dosag on biosorpion Th ffc of h biomass dosag on h biosorpion of h mal ions was invsigad. Th rsuls ar prsnd in Figur 3. Th rsuls show ha biosorpion of ach mal ion incrasd wih incras in biomass dosag, which implis ha mor aciv si wr availabl for h biosorpion of ach mal ion. Consqunly, h biomass dosag of 2g was usd for subsqun sudis. Th gnral rnd of incras in mal ion biosorbd wih incras in biomass dosag indicas an incras in upak du o mor binding sis on h biomass availabl for biosorpion. Such 39

4 Tabl 1: FT-IR spcra characrisics of groundnu shll bfor and afr biosorpion of Pb(II), Cd(II) and Zn(II) for 2 h Mal ion Absorpion bands (cm -1 ) Assignmn Iniial final diffrnc Pb(II) alcohol & carboxyl srching Cd(II) alcohol &carboxyl srching Zn(II) alcohol &carboxyl srching Pb(II) Srching C=O Cd(II) C=O srching Pb(II) bondd OH, -NH srching Cd(II) bondd OH, -NH srching Zn(II) bondd OH, -NH srching Tabl 2: Paramrs of h psudo scond-ordr kinic modl for h biosorpion of Pb(II), Cd(II) and Zn(II) by groundnu shll Mal ion k 2 (g.mg -1 min -1 ) q (mg g -1 ) R 2 S.D. Pb(II) Cd(II) Zn(II) Tabl 3: Frundlich isohrm paramrs for h biosorpion of Pb(II), Cd(II) and Zn(II) by groundnu shll Mal ion 1/n K f R 2 S.D. Pb(II) x10-14 Cd(II) x , Zn(II) x Tabl 4: Thrmodynamic paramrs for biosorpion of Pb(II), Cd(II) and Zn(II) by groundnu shll Mal ion ΔH o (kj mol -1 ) ΔS o (J mol -1 K -1 ) A(kJ mol -1 )@298K A(kJ mol -1 )@308 K Pb(II) Cd(II) Zn(II) rnd has bn rpord for ohr biosorbns (Babarind al., 2009). Biosorpion kinics Th rsuls of h ffc of conac im on h biosorpion of h mal ions ar prsnd in Figur 4. In ach cas i is obsrvd ha biosorpion incrasd wih incras in conac im unil sauraion occurrd. Th opimum im of 2 h was usd for subsqun sudis in h invsigaion of h ffc of ohr physicochmical paramrs. Figur 4 illusras h dynamic biosorpion procss of h mal ions on groundnu shll. I is obsrvd ha h biosorpiv quaniis of h mal ions on groundnu shll incrasd wih incrasing conac im. In ach cas, bipahsic kinics is obsrvd: an iniial rapid sag (fas phas) whr biosorpion is fas and conribus o quilibrium upak and a scond sag (slow phas) whos conribuion o h mal ion biosorpion is rlaivly smallr. Th fas phas is h insananous biosorpion sag, i is assumd o b causd by xrnal biosorpion of mal ion o h shll surfac. Th scond phas is a gradual 40

5 Fig. 1: FT-IR-spcra of h fr and mal-bound groundnu (Arachis hypogaa) shll biosorpion sag, which is diffusion ra conrolld. Finally, h biosorpion sis ar usd up, h upak of h mal ion rachd Equilibrium. This phas mchanism has bn suggsd o involv wo diffusion procsss, xrnal and inrnal, rspcivly (Wu al., 2010). Th biosorpion of ach of h mal ions achivs quilibrium wihin 2 h, alhough, hir ras of upak ar diffrn. This migh b du o h diffrncs in hydrad ionic sizs of h mal ions (Killand, 1937; Babarind al., 2012). Th daa obaind from h sudy on h ffc of im on biosorpion was subjcd o kinic modls in ordr o sablish h mchanism of h biosorpion procss. Svral kinic modls ar ndd o sablish h mchanism of a biosorpion procss (Okasha and Ibrahim, 2010). In ordr o invsiga h kinics of h biosorpion of hs mal ions on groundnu shll, psudo-firs-ordr and psudo-scond-ordr kinic modls wr mployd. On of such modls is h Lagrgrn psudo-firsordr modl which considrs ha h ra of occupaion of h biosorpion sis is proporional o h numbr of h unoccupid sis (Erugay and Bayhan, 2008): ra d[a] k [A] n d (2) Which can also b wrin as d q k 1 q q d (3) 41 Ingraing bwn h limis q = 0 a =0 and q = q a =, w obain q k1 log q q (4) This can b rarrangd o obain a linar form: k1 logq q log q (5) Whr k 1 is h Lagrgrn ra consan of h biosorpion (min - 1 ); q and q ar h amouns of mal ions sorbd (mg g -1 ) a quilibrium and a im, rspcivly. Th plo of Log(q -q ) vrsus for h biosorpion of mal ions on h biomass a iniial concnraion of 100 mgl -1 should giv a sraigh lin for a procss ha follows firs-ordr kinic modl. Th daa was qually subjcd o h psudo-scond-ordr kinic modl. Th psudo-scond-ordr kinic modl is rprsnd in Eq. 6. d d q k q q 2 2 (6) On ingraing bwn boundary condiions, w hav q 1 q 1 q k On rarrangmn, w hav 2 (7)

6 mal ion biosorbd (%) (%) % mal ion biosorbd ISSN: Babarind and Onyiaocha / Chmisry Inrnaional 2(1) (2016) iscinic.org Pb(II) Cd(II) Zn(II) Whr k 2 is h quilibrium ra consan of psudo-scond-ordr biosorpion procss (g mg -1 min -1 ). In h mal ions undr sudy, h sraigh lin plos of vrsus /q show br finss of xprimnal daa wih h scond-ordr kinic modl han ha of h psudo-firs-ordr kinics as prsnd in Figur 5. Th corrlaion cofficin wr found o b highr for h psudo-scond-ordr kinic modl in ach cas i was abov 0.99 as rpord in Tabls 2. Th psudo-scond-ordr kinic modl is hrfor br o prdic h dynamic biosorpion of Pb(II), Cd(II) and Zn(II) ono groundnu shll. Fig. 2: ph-dpndnc profil of h biosorpion of Pb(II), Cd(II), and Zn(II) by groundnu (Arachis hypogaa) shll a 28 C, 100 mgl ph Pb(II) Cd(II) Zn(II) Biosorpion isohrms Th biosorpion daa wr analysd wih Frundlich and Langmuir isohrms. In ach cas, h Fundlich isohrm br rprsns h biosorpion procss as indicad by h valus of h corrlaion cofficin. Figur 6 illusras h Frundlich isohrm for h biosorpion of Pb(II), Cd(II) and Zn(II) ono groundnu shll. Th quilibrium biosorpion incrass wih incras in mal ion concnraion. Th Frundlich and Langmuir isohrms wr mployd o calcula h biosorpion capaciy. Th Frundlich isohrm is an mpirical quaion dscribing adsorpion ono a hrognous surfac. Th Frundlich isohrm is xprssd in Eq log log C log K f n whr K f and ar h Frundlich consans rlad o h biosorpion capaciy and biosorpion innsiy of h biosorbn, rspcivly. Th linar form of h Langmuir quaion is xprssd as: (9) b C m m (10) Whr Γ, Γ m and bm ar h Langmuir paramrs. Biosorpion fficincy Biomass dosag (g) Th rsul of h sudy on h ffc of iniial mal ion concnraion on biosorpion fficincy is as shown in Figur 7. Th plos show ha h biosorpion fficincy of h biomass incrass wih incras in h iniial mal ion concnraion for all h mal ions which migh b du o incras in ffciv collision bwn h mal ions and h aciv sis. Th biosorpion fficincy (E) for ach mal ion was calculad as shown in Eq. 11. Fig. 3: Effc of biomass dosag on h biosorpion of Pb(II), Cd(II) and Zn(II) by groundnu (Arachis hypogaa) shll a 28 C, 100 mgl -1, ph 5 Ci C E 100 Ci (11) q 1 k q q (8) 42 Whr C i and C ar h iniial and h quilibrium mal ion concnraion (mgl -1 ), rspcivly.

7 Fig. 4: Tim cours for h biosorpion of Pb(II), Cd(II) and Zn(II) by groundnu shll a 28 C, 100 mgl -1, ph 5 Fig. 6: Frundlich isohrm plo for biosorpion of Pb(II), Cd(II) and Zn(II) by groundnu shll a 28 C, ph 5 Fig. 5: Th psudo-scond-ordr kinic plo for h biosorpion of Pb(II), Cd(II) and Zn(II) by groundnu shll a 28 C, 100 mgl -1, ph 5 Fig. 7: Effc of iniial concnraion on biosorpion of Pb(II), Cd(II) and Zn(II) on groundnu shll a 28 C, ph 5 Thrmodynamic ramn of h biosorpion procss Thrmodynamic paramrs ( G, H, S ) associad wih h biosorpion procss wr calculad using quaions Th variaion of mpraur affcs h biosorpion of mal ions ono solid surfacs of biomass sinc h biosorpion procss is a rvrsibl on. Th naur of ach sid of h quilibrium drmins h ffc ha mpraur has on h posiion of quilibrium. Th sid ha is ndohrmic is favourd by incras in mpraur, whil h conrary holds for h xohrmic sid. Th corrsponding fr nrgy chang was calculad from h rlaion (Sun al., 2008; Karhik and Mnakshi, 2014): G RT ln K c (12) whr T is h absolu mpraur, (K) and R is h univrsal gas consan (8.314 Jmol -1 K -1 ). Th biosorpion disribuion cofficin (quilibrium consan), K c, was calculad from h rlaionship shown in Eq. 13. K c C C a (13) 43

8 Fig. 8: Thrmodynamic plos for biosorpion of Pb(II), Cd(II) and Zn(II) by groundnu shll Whr C and C a ar h quilibrium concnraions of mal ions (mgl -1 ) in soluion and on biosorbn, rspcivly. Consqunly, h hrmodynamic bhaviour of h biosorpion of Pb(II), Cd(II) and Zn(II) ono groundnu shll was valuad hrough h chang in fr nrgy (ΔG ), nhalpy (ΔH ) and nropy (ΔS ). Th chang in fr nrgy is rlad o ohr hrmodynamic propris (Eq. 14) G H TS (14) Th biosorpion disribuion cofficin can b prssd in rms of ΔH and ΔS as a funcion of mpraur (Eq. 15). ln K c S R RT (15) Whr T is h absolu mpraur (K); R is h gas consan (8.314 Jmol -1 K -1 ). ΔH is h sandard nhalpy chang (Jmol -1 ) and ΔS is h sandard nropy chang (Jmol -1 K -1 ) wr calculad from h slop and inrcp of h linar plo of ΔG vrsus T, rspcivly. Th plos shown in Figur 8 ar linar ovr h nir rang of mpraur invsigad. Th ngaiv valus of ΔG indica sponaniy of ach biosorpion procss. Th hrmodynamic paramrs (fr nrgy ( G ), nhalpy ( H ) and nropy ( S )) for h biosorpion of h mal ions wr calculad as sad abov ar prsnd in Tabl 5. In gnral, h chang of sandard fr nrgy for physiosorpion is in h rang of 20 o 0 kj mol -1 and for chmisorpion varis bwn 80 and 400 kjmol -1 (Vimonss al., 2009; Sn al., 2011). In h prsn sudy, h ovrall G has valus ranging from 4.0 o 0 kjmol -1. Ths rsuls corrspond o a sponanous physical adsorpion of h mal ions, indicaing ha his sysm dos no gain nrgy from xrnal rsourc 44 (Vimonss al., 2009; Arias and Sn, 2009). Th incras in G wih incras in mpraur indicas lss fficin biosorpion a highr mpraur. Th ngaiv valus of H for h biosorpion of h hr mal ions suggs an xohrmic naur of ach biosorpion procss. This is also suppord by h dcras in h valu of biosorpion capaciy of h biosorbn wih ris in mpraur. Similarly, h S valus ar ngaiv indicaing dcras in randomnss during h biosorpion procss for hs hr mal ions. Ths ngaiv valus of S obsrvd for h biosorpion of hs mal ions showd a dcras in randomnss a h solid/soluion inrfac during ach biosorpion procss (Vimonss al., 2009). Furhrmor, h magniud of acivaion nrgy (A) givs an ida abou h yp of adsorpion which is mainly diffusion conrolld procss (no diffusiviy of solu hrough micropor wall surfac of a paricl) or chmical racion procsss (Abd EI-Laif al., 2010). Enrgis of acivaion, A, blow 42 kjmol -1 indica diffusion-conrolld procsss, and highr valus giv chmical racion-basd procsss. Thrfor, nrgy of acivaion, A, has bn calculad as pr h following rlaion (Eq. 17). A H RT (17) Th valus of A a wo diffrn mpraurs ar prsnd in Tabl 5. In his sudy, h acivaion nrgy (A) valus wr lss han 42 kjmol 1 indicaing diffusion-conrolld adsorpion procsss. CONCLUSION Th biosorpion of Pb (II), Cd(II) and Zn(II) by groundnu shll undr various condiions was sudid in his work. Th ph has much ffc on h biosorpion of hs mal ions from aquous soluions. Th ra of h biosorpion of hs mal ions followd psudo-scond-ordr kinics. Th sorpion isohrms of hs mal ions ono h biosorbn ar wll dscribd by Frundlich isohrm modls. Th hrmodynamic sudy showd ha h biosorpion of ach of Pb(II), Cd(II) and Zn(II) was sponanous. This sudy shows ha groundnu (Arachis hypogaa) shll has high ponial for raing indusrial ffluns conaining Pb(II), Cd(II) and Zn(II). REFERENCES Abd EI-Laif, M. M., Ibrahim, A.M., EI-Kady, M.F., Adsorpion quilibrium, kinics and hrmodynamics of mhyln blu from aquous soluions using biopolymr oak sawdus composi. Journal of Amrican Scinc 6(6), Al-Subu. M.M., Th Inracion ffcs of cyprss (Cuprssu smprvirns), Cinchona (Eucalypus longifolia) and pin (Pinus halpnsis) lavs on hir fficincis for lad rmoval from aquous soluions. Advancs in Environmnal Rsarch 6(4),

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