Cd(II) ADSORPTION FROM AQUEOUS SOLUTION BY ACTIVATED CARBON FROM SUGAR BEET PULP IMPREGNATED WITH PHOSPHORIC ACID

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1 Volum No. 9 REPRINT pp Cd(II) ADSORPTION FROM AQUEOUS SOLUTION BY ACTIVATED CARBON FROM SUGAR BEET PULP IMPREGNATED WITH PHOSPHORIC ACID Ahm Özr - Fikr Tümn Angrsr. 855 Frising - Grmany Phon: () 86-8 Fax: () mail: info@psp-parlar.d hp://

2 by PSP Volum No 9. Frsnius Environmnal Bullin Cd(II) ADSORPTION FROM AQUEOUS SOLUTION BY ACTIVATED CARBON FROM SUGAR BEET PULP IMPREGNATED WITH PHOSPHORIC ACID Ahm Özr and Fikr Tümn Dparmn of Chmical Enginring, Univrsiy of Fõra, 79-Elazõğ, TURKEY SUMMARY Th adsorpion of Cd(II) ions from aquous soluions ono acivad carbon obaind by carbonising sugar b pulp imprgnad wih % phosphoric acid was sudid. By incrasing h mpraur of carbonisaion, h rmoval fficincy of Cd(II) ions incrasd. Th maximum rmoval (95.8%) was aaind by acivad carbon sampls obaind by carbonising acid-imprgnad sugar b pulp a 5 C for 9 min. Th rmoval fficincy of Cd(II) ions is, o a larg xn, dpndn on ph of mdium. Th rsuls of xprimns carrid ou a various mpraurs wr applid o Langmuir and Frundlich isohrm quaions. Th valus of Langmuir consan (q max ) a C wr calculad as 68., 7.99 and 7.99 mg/g for acivad carbons obaind a, and 5 C, rspcivly. Th adsorpion procss was found o b xohrmic and Langmuir isohrm daa wr valuad o drmin h hrmodynamic paramrs for h adsorpion procss. I was found ha h valus of qmax and K f dcrasd wih incrasing mpraur. Th daa ar br fid by h scond-ordr kinic modl as compard o firs-ordr kinic modl. KEYWORDS: Sugar b pulp, Acivad carbon, Cd(II) ions rmoval, Phosphoric acid. INTRODUCTION Thr ar various polluans rlasd o h aquaic nvironmn from wass producd as a rsul of many indusrial aciviis playing an imporan rol in h chnological dvlopmn. Th mos imporan groups of hs polluans ar havy mals ha do no dgrad ino harmlss nd-producs by naural physiological mchanisms, bu accumula in h living bodis by h food chain, spcially during h us of surfac war []. Cadmium is gnrally considrd o b on of h mos oxic mals found in h nvironmn. Mining and mallurgy of cadmium, cadmium lcroplaing, bary and accumulaor manufacuring, pigmns, cramics, xil prining indusry waswars and lad min drainag [, ], bu also swag sludg [] conain various amouns of Cd(II) ions. Th main ramn procsss for h rmoval of Cd(II) ions from was srams includ is prcipiaion as hydroxid [, 5] and carbona [6], vaporaion, adsorpion, ion xchang, mmbran procssing, solvn xracion c. []. Adsorpion and ion xchang procsss hav significan bnfis h rad war is ofn sufficinly pur o b rcycld and rusd, and adsorbd mals can b ofn rcovrd and purifid in wll dsignd rgnraion procsss [7]. Acivad carbon is h mos widly sudid adsorbn for h rmoval of Cd(II) ions from aquous soluion. Sinc acivad carbon producion is oo xpnsiv for larg-scal us, various alrnaiv sourcs hav bn usd in is producion. Thrfor many sudis hav bn focusd on prparaion of acivad carbons from chapr and radily availabl marials such as coirpih [8], coconu r sawdus [9], almond shlls, oliv and pach sons [], oil palm sons [] and plum krnls []. On h ohr hand som cllulosic marials such as coconu shll and raw ric husk [], war hyacinh [], nu and walnu shlls, was a [5], pin bark [6], pinus pinasr bark [7] and biosorbns [8-] hav bn usd in h adsorpion of Cd(II) ions from aquous soluions. Bu, acivad carbon adsorpion appars o b a paricularly compiiv and ffciv procss for h rmoval of Cd(II) ions and ohr oxic mals a rac quaniis. In his conx, w hav sudid Cd(II) ion adsorpion by acivad carbon prpard from sugar b pulp, which is an abundan and chap marial producd in sugar indusry as a by-produc. Th objciv of h prsn sudy was o invsiga h ffcs of carbonisaion mpraur, conac im, iniial ph and conac mpraur on h adsorpion of 5

3 by PSP Volum No 9. Frsnius Environmnal Bullin Cd(II) ions by acivad carbon prpard from sugar b pulp imprgnad wih phosphoric acid. Equilibrium isohrm daa wr wll fid o Langmuir and Frundlich isohrm quaions and h isohrm consans wr drmind. Also, adsorpion kinics of Cd(II) ions wr analysd by applying h psudo firs-ordr and psudo scond-ordr kinic modls o h daa. MATERIALS AND METHODS Marial Sugar b pulp was providd from a local sugar facory in Elazõğ, Turky. Th convrsion of sugar b pulp o acivad carbon was carrid ou as following: Raw sugar b pulp was drid on a polyhyln layr and sord in a closd jar. A sampl of 5 g of drid sugar b pulp was rad wih ml phosphoric acid ( %) for hours. Th phosphoric acid-rad biomass was hn filrd by sucion, washd wih 5 ml disilld war o rmov xcss acid from sugar b pulp and drid o minimiz humidiy. Th carbonisaion procss was carrid ou by haing h phosphoric acid-rad sampls in a fixd bd a diffrn mpraurs (, and 5 C) in a consan flow ra of N for 9 min. Sinc h acivad carbon sampls had a jlly srucur, hy wr washd wih dionisd war o rmov h xcss phosphoric acid and filrd unil h ph of h suprnaans rmaind consanly a around.. Th acivad carbons wr drid a 5 C, ground and sivd o obain h msh fracion. This fracion was sord in dsiccaors filld wih CaCl during h xprimnal sudy. Th BET surfac ara of acivad carbons was drmind by N gas adsorpion chniqu using a Quanachrom Monosorb Dirc Surfac Analysr apparaus. Th iodin numbr (IN) of acivad carbons was drmind by shaking.5 g of ach sampl wih ml aquous soluion of iodin (.7 g I /l) a 5 ºC. Afr a shaking priod of 5 min, h suspnsion was filrd and h concnraion of rsidual iodin was drmind by iraing h suprnaan wih. N sodium hiosulpha soluion. Th gram amoun of iodin adsorbd pr gram carbon was akn as iodin numbr. Fixd carbon and acidinsolubl mar conns of h acivad carbons wr drmind by h mhod dscribd in []. Prparaion of soluions Working soluions of Cd(II) ions wr prpard by diluing a mg/l sock Cd(II) soluion which was obaind by dissolving analyical grad cadmium sulpha (CdSO.8H O) supplid by Ridl-d Han Chmicals. Ohr ragns usd in his sudy wr of analyical grad. Th ph of ach soluion was adjusd o h rquird valu by using. M NaOH or. M HCl soluion. All diluions and soluions wr mad by using disilld war. Adsorpion Exprimns Adsorpion xprimns wr carrid ou by shaking 5 ml of a mg/l Cd(II) soluion wih.5 g of acivad carbon obaind a diffrn mpraurs in ml flasks wih conac ims ranging from 5 o min. Th flasks wr shakn a consan ra using a flask shakr (Clifon) wih hrmosaic war bah. To obain diffrn iniial ph valus for ach working soluion, 5 ml sock Cd(II) soluion was addd o a 5 ml glass bol and dilud up o h mark wih dionisd war and NaOH or HCl soluion. For isohrm sudis, a sris of flasks conaining 5 ml Cd(II) soluion in h rang of 5-5 mg/l wr prpard..5 g acivad carbon was addd o ach vial and h mixurs wr agiad a consan mpraur. Ths xprimns wr carrid ou a consan ph 6. for a conac priod of min. A h nd of h conac priod rquird, h aquous phas was sparad from acivad carbon by cnrifugaion a 5 rpm for min and h concnraion of rsidual Cd(II) ions in h suprnaans was drmind by aomic absorpion spcrophoomry (Prkin Elmr 7 modl). Th amoun of adsorbd Cd(II) ions was calculad by h diffrnc of iniial and final concnraion. All xprimns, xcp for isohrm sudis, wr conducd a C in duplica and avrag valus wr rpord. RESULT AND DISCUSSIONS Characrisaion of acivad carbons Som propris of acivad carbons usd in his sudy ar prsnd in Tabl. Th yild of acivad carbons dcrass dpnding on h ris in mpraur of carbonisaion. Th rmoval fficincy of volail subsancs from phosphoric acid-imprgnad sugar b pulp dpnds, o a larg xn, on h carbonisaion mpraur, which causs a dcras in fracion of fixd carbon in carbonisaion producs. I can b sn ha BET surfac aras of acivad carbons do no show a rgular chang wih carbonisaion mpraur. Th valu of BET surfac ara of acivad carbon obaind a C is highr han hos of ohr acivad carbons. Th lowr valu of surfac ara of acivad carbon producd a 5 C may b aribud o h convrsion of micropors o msopors or macropors, rsuling in lowr surfac ara. On h ohr hand, h iodin numbr incrasd from 56. o 9. mg/g whn carbonisaion mpraur incrasd from C o 5 C. I is clar ha hr is no rgular rlaion bwn h iodin adsorpion capaciis of acivad carbons and hir surfac ara. Th adsorpion of iodin molculs by acivad carbon may b xprssd in wo ways; h binding of iodin molculs on h aciv sis by chmical bonds and h physical adsorpion of 5

4 by PSP Volum No 9. Frsnius Environmnal Bullin TABLE Som characrisics of acivad carbons from sugar b pulp imprgnad wih phosphoric acid. Carbonisaion mp. ( C) 5 Yild (%) BET surfac ara (m /g) Iodin numbr (mg I /g) Carbon conn (%) Acid-insolubl mar (%) hs molculs in h pors. I is probably ha a lowr mpraurs h numbr of aciv sis is no sufficin o upak h iodin molculs chmically. In his cas, a ris in carbonisaion mpraur may lad o an nhanc in h numbr of aciv sis and incrass h adsorpion yild of iodin molculs. Alhough i is xpcd ha h carbon conn of acivad carbons incrass wih incrasing carbonisaion mpraur, an opposi bhaviour was obsrvd. This siuaion is causd by oxygn. Oxygn is prsn as impuriy in nirogn gas passing ovr sugar b pulp during h carbonisaion procdur. This causs a dcras in carbon conn of carbonisd marials as a rsul of C-O racion fficinly aking plac a highr mpraurs. In addiion, oxygn in compounds may conribu o his carbon loss by a dcarboxylaion. Th amouns of acid-insolubl mars, which is a masur of undissolvd inorganic compounds such as mal oxids and silicas, wr drmind as 6.%, 6.9% and 8. % for acivad carbons obaind a C, C and 5 C, rspcivly. Ths compounds form h ash conn of acivad carbons. Th fracion of inorganic compounds incrasd rlaivly wih incrasing carbonisaion mpraur, whil h amoun of carbon in h rsuling producs dcrasd a highr mpraur. Cadmium adsorpion Effc of iniial ph Th soluion ph affcs h surfac charg of adsorbn, h dgr of ionisaion and h spciaion of h surfac funcion groups []. For ha rason, in many sudis carrid ou o rmov havy mals from aquous soluions, i has bn poind ou ha h soluion ph is on of h mos imporan paramrs affcing adsorpion yild. Th ffc of iniial ph on h adsorpion of Cd(II) ions was sudid by conacing.5 g acivad carbon from sugar b pulp wih 5 ml Cd(II) soluion ( mg/l) for min a C. Th iniial phs of h working soluions ar varid from. o.8. Th rsuls of hs xprimns ar givn in Fig.. Th rmoval prcnag of Cd(II) ions incrasd sharply wih ph valus up o 6., and afr ph 9. i ndd o dcras, as is vidn in Fig.. Th maximum rmoval prcnags wr found o b 9.6 %, 9. % and 95.8 % a iniial ph 6. for acivad carbons obaind a, and 5 C, rspcivly. As can b sn from Fig. h adsorpion yild is vry low in srongly acidic mdium. This has alrady bn noicd by svral workrs [-5]. Th lowr adsorpion prcnag obsrvd a low phs may b xplaind on h basis of lcrosaic rpulsion forcs bwn posiivly chargd H O + and Cd + ions. A low ph valus, h concnraion of H O + is highr han ha of Cd(II) ions and, hnc, hs ions ar adsorbd on h aciv sis of acivad carbons, laving Cd(II) ions fr in h soluion. Whn h ph incrasd, Cd(II) ions would rplac H O + ions bcaus of comping ffcs, which incrasd h adsorpion yild of h Cd(II) ions. Cd(II) adsopion, % C C 5 C ph b FIGURE - Effc of iniial ph on h adsorpion of Cd(II) ions by acivad carbons from sugar b pulp (Condiions: 5 ml of mg/l Cd(II) soluion;.5 g acivad carbon obaind a diffrn mpraurs; conac im min.; conac mpraur C). Th hydrolysis and prcipiaion of mal ions affc adsorpion by changing h concnraion and forming of solubl mal spcis availabl for adsorpion. Th hydrolysis of Cd(II) ions may b rprsnd by h following racion: Cd + +nh O Cd(OH) n -n + nh O + () As suggsd by Rd and Masumoo [6], various spcis of cadmium can b formd as a funcion of ph (Fig. ). Th hydrolysis xnd of Cd(II) ions is no imporan up o approximaly ph 7.5. I can b clarly sn ha h concnraion of Cd(OH) + ions rachs a maximum a around ph 9.5. A ph valus > 8. h rmoval aks plac by adsorpion as wll as prcipiaion of Cd(II) ions in h form of Cd(OH). Prcipiaion of Cd(II) ions bgins horically a ph valus of 8. for h 5

5 by PSP Volum No 9. Frsnius Environmnal Bullin concnraion of mg/l. Thrfor opimum ph for Cd(II) ions adsorpion was slcd as 6.. A his ph valu h adsorpion of Cd(II) ions was no maskd by prcipiaion. Th opimum ph for Cd(II) ions adsorpion from aquous soluions by acivad carbons from almond shlls, oliv and pach son has bn rpord as 5. []. In ohr sudis carrid ou wih acivad carbon from coirpih, maximum rmoval was aaind a ph. [8]. Opimum ph for adsorpion of Cd(II) ions by acivad carbon from bagass was rpord as.5 [5]. Cimino al. [7] hav rpord ha maximum rmoval in h adsorpion of Cd(II) ions by carbon from hazlnu shll rad wih sulphuric acid was obsrvd in h ph rang from. o 6.. In our prvious sudy [] rlad o Cd(II) ions adsorpion, opimum ph has bn found o b 6.. In anohr sudy using Girdih coal o rmov Cd(II) ions from aquous soluions, h maximum rmoval prcnag was obsrvd a ph 6.6 []. Ths rsuls show ha h adsorpion yild of Cd(II) ions by various adsorbns is dpndn on ph of soluion. Th dcras in adsorpion yild a ph > 9. can b aribud o h formaion of Cd(OH) ions aking plac as a - rsul of dissoluion of Cd(OH), du o is amphor characrisic. Sinc cadmium is prsn in h form of Cd + ions a opimum ph 6., h adsorpion mchanisms can b xplaind on h basis H O + - Cd + xchang racion which was a funcion of soluion ph. Fracion of oal cadmium,8,6,, Cd + Cd(OH) ph FIGURE Spciaion of Cd(II) as a funcion of ph. Cd(OH) Cd(OH) - Effc of conac im Th influnc of conac im on h rmoval of Cd(II) ions by acivad carbon sampls producd a diffrn mpraurs is illusrad in Fig.. Th rmoval prcnag of Cd(II) ions by acivad carbons incrasd wih incrasing conac im and aaind an quilibrium afr min for h iniial concnraion of mg/l. Alhough h adsorpion yild of acivad carbon obaind a 5 C is highr han ha of h ohr xprimns, hr is no rmarkabl diffrnc among hir adsorpion yilds. I can b sn ha h majoriy of Cd(II) ions is adsorbd wihin h firs 5 min. For his im,. %, 66. % and 7.7 % of oal Cd(II) ions wr rmovd from h soluion by acivad carbons obaind a, and 5 C, rspcivly. Afr quilibraion im, i was obsrvd ha hr was only a small incras in h rmoval yild by incrasing h conac im. Cd(II) adsorpion, % Conac im, min. C C 5 C FIGURE - Effc of conac im on h adsorpion of Cd(II) ions by acivad carbons from sugar b pulp (Condiions: 5 ml of mg/l Cd(II) soluion;.5 g acivad carbon obaind a diffrn mpraurs; iniial ph 6.; conac mpraur C). Th quilibrium ims for h adsorpion of Cd(II) ions on h diffrn adsorbns hav bn rpord in a wid rang of conac im. Th paramrs such as sirring ra of suspnsion, physical and chmical propris of adsorbn (porosiy, surfac ara, h srucur of funcional groups, aciv adsorpion sis), and adsorba (aomic and ionic radius, polariy and lcronic charg) hav an imporan influnc on h quilibrium im. Th quilibrium ims rquird for h rmoval of Cd(II) ions by acivad carbons from sugar b pulp ar qui low, which can b valuad as an advanag from h poin of viw of procss conomy. Adsorpion isohrms and hrmodynamic paramrs In quilibraion xprimns, a fixd amoun of acivad carbons (.5 g) and 5 ml Cd(II) soluion wih various concnraions (5-5 mg/l ) was placd in a ml glass sopprd flask and shakn in a hrmosaic shakr bah for min a consan ph. Th quilibrium bwn adsorbd Cd(II) ions on h acivad carbons and Cd(II) ions rmaining in soluion was dscribd by using Langmuir and Frundlich modls. Th linar form of Langmuir isohrm can b wrin as C q = K q max C + q max whr C is h quilibrium concnraion of h adsorba (mg/g), q is h amoun adsorbd pr uni mass of adsorbn (mg/g), q max is h maximum adsorpion capaciy (mg/g), K (l/mg) is a consan rlad o h affiniy of binding sis or bonding nrgy and q max rprsns a pracical limiing adsorpion capaciy whn h surfac of adsorbn is complly covrd wih adsorba. () 5

6 by PSP Volum No 9. Frsnius Environmnal Bullin C/(x/m), g /l 5 5 o C o C 5 o C C C C C C C C, mg /l C C C ln(x/m),5,5,5,5,5,5,5,5,5 o C C C C o C C C C 5 o C C C C,5,5,5,5,5 5 5,5 6 lnc FIGURE - Langmuir plo of Cd(II) ions adsorpion by acivad carbons from sugar b pulp (Condiions: conac im min.,.5 g acivad carbon obaind a diffrn mpraurs; iniial ph 6.). FIGURE 5 - Frundlich plo of Cd(II) ions adsorpion by acivad carbons from sugar b pulp (Condiions: conac im min.,.5 g acivad carbon obaind a diffrn mpraurs; iniial ph 6.). TABLE - Langmuir isohrm consans for adsorpion of Cd(II) ions on acivad carbon from sugar b pulp imprgnad wih phosphoric acid. Carbonisaion mp. ( C) 5 Isohrm Langmuir consans mp. ( C) q max (mg/g) K (l/mg) R TABLE - Frundlich isohrm consans for adsorpion of Cd(II) ions on acivad carbon from sugar b pulp imprgnad wih phosphoric acid. Carbonisaion mp. ( C) 5 Isohrm Frundlich consans mp. ( C) K f n R

7 by PSP Volum No 9. Frsnius Environmnal Bullin Hnc, a plo of C /q vs. C should b a sraigh lin wih a slop /q max and inrcps /Kq max (Fig. ), indicaing ha h adsorpion of Cd(II) ions on h acivad carbons from sugar b pulp follows h Langmuir modls. Th paramrs rlad for h fiing o Langmuir quaion a diffrn mpraurs for hr acivad carbon sampls ar summarizd in Tabl. Th quilibrium daa for Cd(II) ions also fid o Frundlich modl. This modl dals wih mulilayr adsorpion of h subsancs on h adsorbns. Th logarihmic form of his modl is givn by h following quaion: lnq = lnkf + lnc () n whr K f and n ar h Frundlich consans. Th valus of K f and n may b calculad from h slops and inrcps of h lins by ploing lnq agains lnc, as dpicd in Fig. 5. Th calculad valus of K f and n for acivad carbons obaind a, and 5 C ar prsnd in Tabl. Th valus of rgrssion cofficins (r ) in Tabls and showd ha Langmuir and Frundlich modls adqualy dscribd h quilibrium daa, bu h daa fid br o Langmuir isohrm han o ha of Frundlich for adsorpion of Cd(II) ions on acivad carbon sampls. Th maximum adsorpion capaciis (q max ) dcrasd from 68. o 57.8, 7.99 o 6.89 and 7.99 o 65.6 mg/g wih ris in mpraur from o C for Cd(II) ions upak on acivad carbons obaind a, and 5 C, rspcivly. Whil h valus of q max and K incras wih a ris in carbonisaion mpraur, hir valus also xhibi a dcrasing rnd dpnding on h isohrm mpraur. Alhough various kinds of adsorbns ar usd o rmov Cd(II) ions, h rsuls obaind in hs sudis rval major diffrncs in hir adsorpion capaciis. For adsorpion of Cd(II) ions by acivad carbon drivd from bagass, Mohan and Singh [5] found q max valu as 8.8 mg/g and maximum Cd(II) upak by carbon from hazlnu shll was 5. mg/g [7]. In a sudy carrid ou wih sugar b pulp, h maximum adsorpion capaciy has bn found o b.9 mg/g for Cd(II) ions adsorpion []. Th maximum cadmium adsorpion capaciy was.5 mg/g for almond shll carbon, 5.9 mg/g for oliv son carbon,.7 mg/g for pach son carbon [], 7.87 mg/g for granulad acivad carbon [8],. mg/g for aprico son carbon,. mg/g for coconu shll carbon, 9.8 mg/g for ligni coal carbon [9] and.7 mg/g for granular and powdrd acivad carbons []. Th adsorpion capaciy (q max ) of acivad carbons usd in h prsn sudy was highr han hos of h adsorbns mniond abov. I mus b nod ha h dirc comparison of rmoval capaciis of acivad carbons from sugar b pulp wih hos of ohr adsorbns is difficul du o diffrn xprimnal condiions applid in h sudis cid. Th valus of K f (a C), assumd as masur of adsorpion capaciy, incrasd from 6.9 o.9 wih incrasing carbonisaion mpraur from o 5 C. On h ohr hand, h valus of K f dcrasd wih incras of h mpraur a which h isohrms wr consrucd (Tabl ). As can b sn from his abl, h valus of n ar highr han, indicaing ha h Cd(II) ions ar favourably adsorbd by h acivad carbons a all h mpraurs sudid. Th siuaion n > is mos common and may b du o a disribuion of surfac sis or any facors ha caus a dcras in adsorbn-adsorba inracion wih incrasing surfac dnsiy [6]. Th valus of n in h rang of - rprsn good adsorpion []. Changs of hrmodynamic paramrs, such as nhalpy ( H ), fr nrgy ( G ) and nropy ( S ), wr also calculad using quaions (), (5) and (6). o ' H lnk = lnk () R T ln K S o G = R o T (5) o o ( Η G ) = (6) T Th nhalpy changs of h procss drmind from h slop of h lin obaind by ploing lnk vs. /T (Fig. 6) wr found o b.8, -. and kj/mol for h acivad carbons prpard a, and 5 C, rspcivly. Th ngaiv valus of H confirm h xohrmic naur of h procss for all hr acivad carbons. Th valus of ohr hrmodynamic paramrs ar givn in Tabl. Th ngaiv valus of G a diffrn mpraurs ar du o h fac ha h procss is sponanous wih high prfrnc of Cd(II) ions for acivad carbon sampls. Th fr nrgy chang incrass wih incrasing mpraur showing ha h adsorpion fasibiliy dcrass a highr mpraurs. Th nropy chang for h adsorpion procss has a posiiv sign, which rflcs h affiniy of acivad carbons for Cd(II) ions in h soluion. LnK 9 8,8 8,6 8, 8, 8 7,8 7,6,,,,, Tmpraur, /K FIGURE 6 - Plo of lnk vs. /T for h nhalpy chang of h adsorpion procss. C C 5 C 55

8 by PSP Volum No 9. Frsnius Environmnal Bullin TABLE - Thrmodynamic paramrs for h adsorpion of Cd(II) ions on acivad carbons from sugar b pulp imprgnad wih phosphoric acid. Tmp. ( C) - G (kj/mol).. 9. Carbonisaion mpraur ( C) 5 S - G S - G S (kj/mol K) (kj/mol) (kj/mol K) (kj/mol) (kj/mol K) Adsorpion kinics In ordr o drmin h adsorpion ra consan, psudo-firs ordr and psudo-scond ordr kinic modls wr applid o h xprimnal daa. Th firs ordr kinic modl known as Lagrgrn ra quaion was h firs ra quaion for h adsorpion of liquid/solid sysms basd on h solid capaciy [], and is gnrally xprssd as follows: dq d = k (q q ) (7),ad Th psudo scond-ordr modl is also basd on h adsorpion capaciy of a liquid/solid sysm. If h ra of adsorpion is a scond-ordr mchanism, h kinic ra quaion can b wrin as follows: dq d k (q q ) =,ad (8) whr q (mg/g) is h amoun of adsorba a quilibrium, q is h amoun of adsorba a any im, k,ad (l/min) and k,ad (g/mg min) ar h ra consans of psudo firs-ordr and psudo scond-ordr adsorpion, rspcivly. Ingraing of h quaion 7 for h boundary condiions = o = and q = o q =q, givs: log(q q ) = k log(q ) -. (9) and h ingrad form of quaion 8 for h sam condiions is a linar form of scond-ordr ra quaion q = + () k q q,ad Fig. 7 shows a plo of log(q -q ) vs. for hr acivad carbons a C. Th firs-ordr ra consan (k,ad ) calculad from h slop of h plos and h corrlaion cofficins ar givn in Tabl 5. Th valus of k,ad wr found o b.6,.56 and.567 l/min for acivad carbon sampls obaind a, and 5 C, rspcivly. Also h horical q c valus, which should b qual o h valus of q in idal condiions, calculad from h inrcp of plos ar abulad (Tabl 5). Alhough h corrlaion cofficins (R ) drmind for acivad carbons obaind a diffrn mpraurs wr found o b high, h diffrnc bwn h valus of q and q c did no giv rasonabl valus. This suggss ha his procss do no oby wll o h firs-ordr ra xprssion of Lagrgrn. Log(q-q) /q,8,6,, -, -, C C 5 C 5 Tim, min. FIGURE 7 - Lagrgrn plo of Cd(II) ions adsorpion by acivad carbons from sugar b pulp (Condiions: 5 ml of mg/l Cd(II) soluion;.5 g acivad carbons obaind a diffrn mpraurs; iniial ph 6.; conac mpraur C).,5,5,5,5 5 7 Tim, min. C C 5 C FIGURE 8 - Scond-ordr kinic modl plo of Cd(II) ions adsorpion by acivad carbons from sugar b pulp (Condiions: 5 ml of mg/l Cd(II) soluion;.5 g acivad carbons obaind a diffrn mpraurs; iniial ph 6.; conac mpraur C). 56

9 by PSP Volum No 9. Frsnius Environmnal Bullin Carbonisaion mp. ( C) 5 k,ad (/min) TABLE 5 - Kinic paramrs for h adsorpion of Cd(II) ions on acivad carbons from sugar b pulp imprgnad wih phosphoric acid. Firs ordr kinic modl R q c (mg/g) q (mg/g) k,ad (g/mg min)..6.6 Scond ordr kinic modl R q c (mg/g) q (mg/g) To drmin h valus of k,ad and q c, /q was plod agains a C for ach acivad carbon (Fig. 8). Th valus of k,ad and q c calculad from h slop and inrcp of h plos, rspcivly, ar also prsnd in Tabl 5. Th rsuls indicad ha an incras in carbonisaion mpraur incrasd h ra consan for scondordr kinic. Th corrlaion cofficins for h scondordr kinic modl ar approximaly qual o. Thr ar no rmarkabl diffrncs bwn h valus of horical q c and xprimnal q, showing h bs corrlaion of daa for h scond-ordr kinic modl and h applicabiliy of quaion for h adsorpion of Cd(II) ions by acivad carbons. CONCLUSIONS In ordr o xamin h availabiliy and ffcivnss of acivad carbon from sugar p pulp a diffrn mpraurs for h rmoval of Cd(II) ions, i was obsrvd ha h rmoval prcnag was incrasd wih incrasing conac im and rachd an quilibrium sa wihin min. Th opimum ph was drmind as 6., a which h maximum rmoval prcnags wr 9.6 %, 9. % and 95.8 % for acivad carbons obaind a, and 5 C, rspcivly. In Cd(II) ions rmoval by acivad carbons from sugar b pulp, h applicaion of Langmuir isohrm modl was mor appropria han ha of Frundlich. Th adsorpion capaciis for Cd(II) of acivad carbons wr found o b rlaivly high whn compard wih hos of many ohr adsorbns rpord in h liraur. I was noicd ha h isohrm consan dcrasd wih incrasing mpraur. Ngaiv valus of H indica h xohrmic naur of h adsorpion procss. Ohr hrmodynamic paramrs rflc h fasibiliy and sponanous naur of h procss using acivad carbons from sugar b pulp wr usd as adsorbns for Cd(II) ions rmoval. Th applicabiliy of h firs and scond-ordr kinic modls for h adsorpion of Cd(II) ions on acivad carbons was also xamind. Th kinic rsuls showd ha h adsorpion of Cd(II) ions ono acivad carbons fid vry wll o h scond-ordr kinic modl compard o h firs-ordr on. ACKNOWLEDGEMENTS This sudy was suppord by h Sa Planning Organisaion (DPT), Turky. REFERENCES [] PEAVY H.S, ROWE D.R & TCHOBANOGLOUS G., Environmnal Enginring, McGraw Hill, Nw York, pp. 8. (985). [] ECKENFELDER W.W., Indusrial War Polluion Conrol, h Ed., McGraw Hill, Nw York, pp.. (989). [] PATTERSON J.W, Waswar Tramn Tchnology, Ann Arbor, USA (977). [] BARROW M.L & WEBER W.J., Trac Elmns in Swag Sludg, J. Sci. Food Agriculur, :,9-. (97). [5] SITTIG M., Polluan Rmoval Handbook, Noys Daa Corparaion, Nw Jrsy, pp (97). [6] PATTERSON P.J., ALLEN H.E. & SCALA J.J., Carbona prcipiaion for havy mal polluans. J War Pollu. Con. Fd., 9, 97-. (977). [7] McKAY G., Us of adorbns for h rmoval of polluans from waswars, CRS Prss, Boca Raon, FL (995). [8] KADIRVELU K., THAMARAISELVI C. & NAMA- SIVAYAM C., Rmoval of havy mals from indusrial waswars by adsorpion ono acivad carbon prpard from an agriculural solid was, Biorsourc Tch., 76, (). [9] KADIRVELU K., PALANIVAL M., KALPANA R. & RA- JESVARI S., Acivad carbon from an agriculural byproduc, for h ramn of dying indusrial waswar, Biorsourc Tch., 7, (). [] FERRO-GARCIA M.A., ULTRILLA-RIVERA J., RODRI- GUEZ-GORDILLO J. & BAUTISTA-TOLEDO I., Adsorpion of zinc, cadmium and coppr on acivad carbons obaind from agriculural by-producs, Carbon, 6, 6-7. (988). [] LUA A.C. & GUO J., Acivad carbon prpard from oil palm son by on-sp CO acivaion for gasous polluan rmoval, Carbon, 8, (). 57

10 by PSP Volum No 9. Frsnius Environmnal Bullin [] WU F.C., TSENG R.L. & JUANG R.S, Por srucur and asorpion prformanc of h acivad carbons prpard from plum krnls, J Hazard. Mar., B69, 87-. (999). [] BHATTACHARY A.K. & VENKOBACHAR C., Rmoval of cadmium by low cos adsorbns, J. Environ. Eng.,, -. (98). [] PRAKASH O., MEHROTRA I. & KUMAR P., Rmoval of cadmium from war by war hyacinh, J. Environ. Eng.,, (987). [5] ORHAN Y. & BÜYÜKGÜNGÖR H., Th rmoval of havy mals by using agriculural wass, War Sci. Tch., 8, 7-5. (99). [6] AL-ASHEH S., BANAT F., AL-OMARI R. & DUVNJAK Z., Prdicion of Binary Sorpion Isohrms for h Sorpion of Havy Mals by Pin Bark Using Singl Isohrm Daa, Chmosphr,, (). [7] VAZQUEZ G., GONZALEZ-ALVAREZ J., FREIRE S., LOPEZ-LORENZO M. & ANTORRENA G., Rmoval of cadmium and mrcury ions from aquous soluion by sorpion on rad Pinus pinasr bark: kinic and isohrms, Biorsourc Tch., 8, 7-5.(). [7] CIMINO G., PASSERINI A. & TOSCANO G., Rmoval of Toxic Caions and Cr(VI) from Aquous Soluion by Hazlnu Shll, Wa. Rs.,, (). [8] RAMOS R.L., MENDEZ J.R.R., BARRON J.M., RUBIO L. & CORANADO R.G.M., Adsorpionof Cd(II) from aquous soluions ono acivad carbon, War Sci. Tch., 5, 5-. (997). [9] BUDINOVA T.K., GERGOVA K.M., PETROV N.V. & MINKOVA V.N., Rmoval of mal ions from aquous soluions by acivad carbon from diffrn raw marials, J. Chm. Tch. Biochnol.,, 7-8. (99). [] AN H.K., PARK B.Y. & KIM D.S., Crab shll for h rmoval of havy mals from aquous soluõon, Wa. Rs., 5, (). [] MCKAY G., OTTERBURN M.S. & SWEENEY A.G., Th rmoval of colour from fflun using various adsorbns. III Silica ra procss, Wa. Rs.,, -. (98). [] HO Y.S. & McKAY G., Th sorpion of lad(ii) ions on pa. Wa. Rs., : (999). [8] WILLIAMS C.J, ADERHOLD D. & EDYVEAN R.G.J., Comprison bwn biosorbns for h rmoval of mal ions from aquous soluions, Wa. Rs.,, 6-. (998). [9] MATHEICKAL J.T., YU Q. & WOODBURN G.M., Biosorpion of cadmium(ii) from aquous soluions by prrad biomass of marin alga durvillaa poaorum, Wa. Rs.,, 5-. (999). [] KAEWSARN P. & YU Q., Cadmium(II) rmoval from aquous soluions by pr-rad biomass of marina alga Padina sp, Environ. Pollu.,, 9-. (). [] SNELL F.D. & ETTRE L.S., (Ediors), Encyclopdia of indusrial chmical analysis, inrscinc puplicaion, John Wily and Sons, Nw York Vol:, pp. -5. (969). [] REDDAD Z., GERENTE C., ANDRES Y. & CLOIREC P.L., Adsorpion of svral mal ions ono a low cos biosorbn: Kinic and quilibrium sudis, Environ. Sci. Tch., 6, (). [] LOW K.S., LEE C.K. & LIEW S.C., Sorpion of cadmium and lad from aquous soluions by spn grain, Procss Biochm., 6, (). [] ÖZER A., TANYILDIZI M.S. & TÜMEN F., Sudy of cadmium adsorpion from aquous soluion on acivad carbon from sugar b pulp, Environ. Tch., 9, 9-5. (988). [5] MOHAN D. & SINGH K.P., Singl-and muli-componn adsorpion of cadmium and zinc using acivad carbon drivd from bagass-an agriculural was, Wa. Rs. 6, -8. (). [6] REED B.E. & MATSUMOTO M.R., Modling cadmium adsodrpion by acivad carbon using Langmuir and Frundlich xprssions, Spar. Sci. Tch., 8, (99). Rcivd for publicaion: Novmbr, Accpd for publicaion: April, CORRESPONDING AUTHOR Ahm Özr Dparmn of Chmical Enginring Univrsiy of Fõra 79 Elazõğ - TURKEY Phon: +97 x. 6 Fax: mail: aozr@fira.du.r FEB/ Vol / No 9/ pags