Chemically Modified Cornulaca monacantha Biomass for Bioadsorption of Hg (II) from Contaminated Water: Adsorption Mechanism

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1 Journal of Environmnal Procion, 3, 4, 8-89 hp://dx.doi.org/.436/jp Publishd Onlin March 3 (hp:// Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: A. Hashm,*, Khalid A. Al-Khraij Faculy of Scinc and Ars a Shaqra, Shaqra Univrsiy, Shaqra, KSA; Naional Rsarch Cnr, Txil Rsarch Division, Cairo, Egyp. * ashm@yahoo.com, alihashm@su.du.sa Rcivd January 3 rd, 3; rvisd Fbruary 4 h, 3; accpd Fbruary 6 h, 3 ABSTRACT Cornulaca monacanha (CM) a dsr plan has bn uilizd as adsorbn marial for h rmoval of Hg (II) ions from conaminad war afr ramn wih acrylamid in alkalin mdium o form carbamoylhylad Cornulaca monacanha (CECM). Thr lvls of CECM having diffrn nirogn conn wr prpard. Th CECM sampls wr characrizd by simaing h nirogn conn. Th abiliy of CECM o adsorb Hg (II) was invsigad by using bach adsorpion procdur. Th daa of h adsorpion isohrm was sd by h Langmuir, Frundlich and Tmkin modls. Th rmoval of Hg (II) ono CECM paricls could b wll dscribd by h psudo-scond ordr modl. Th adsorpion ra of mrcury was affcd by h iniial Hg (II) ion concnraion, iniial ph, adsorbn concnraion and agiaion im as wll as xn of modificaion. Th adsorpion xprimns indicad ha h CECM paricls hav gra ponial for h rmoval of Hg (II) from conaminad war. Th maximum adsorpion capaciy, Q max of h CECM owards Hg (II) ions was found o b mg/g a 3 C. Similarly, h Frundlich consan, n was found o b.3 a 3 C. Kywords: Cornulaca monacanha; Carbamoylhylaion; Adsorpion Isohrm; Hg (II) Rmoval; Conaminad War. Inroducion Th indusrial aciviy is rsponsibl o gnra a larg volum hazardous conaining ffluns [,]. Ths hazardous ffluns nd o b rad bfor bing dlivrd ino h nvironmn. Mrcury can b found in significan amouns in wass from chloro-alkali manufacuring plans, lcrical and lcronics manufacuring, and sulfid or roasing opraions. Mrcury is h mos harmful o humans, plans and animals. Exposur o mrcury can hav oxic ffcs on rproducion, h cnral nrvous sysm, livr, and kidny, and caus snsory and psychological impairmns [3]. Thrfor, all counris hav akn masurs o rduc mrcury xposur hrough comprhnsiv prvnion sragis including nvironmnal sandards ha rquir rmoval of mrcury from indusrial ffluns. Thr ar various sablishd mhods for h rmoval of havy mals. Gnrally, h chniqus mployd includ rducion and prcipiaion [4], coagulaion, floaion [5], adsorpion on acivad carbon [6,7], ion-xchang and rvrs osmosis or lcro dialysis [8]. Ths * Corrsponding auhor. mhods, howvr, ar lss fficin and cra sludg. Ion-xchang and rvrs osmosis, vn hough ffciv and fficin, and xpnsiv, hnc only fw indusris hink of i. Th adsorpion procss [9] is on of h mos ffciv mhods usd o rmov havy mals from aquous soluion. Acivad carbon is h mos widly usd adsorbn for his purpos bcaus of is xndd surfac ara, microporous srucur, high adsorpion capaciy and high dgr of surfac raciviy. Thrfor, commrcially acivad carbons ar vry xpnsiv []. This ld o sarch for chapr adsorbn. Consqunly, numrous low-cos alrnaiv adsorbn hav bn proposd including lingo-cllulosic wass. Naural cllulosic marials ar abundanly availabl, vry chap and can b modifid vry asily. Som chmical modificaions of cllulos or lignocllulosic marials can improv h adsorbn bhavior of hs marials. Modificaion racions, including crosslinking and/or funcionalizaion, hav bn rid o nhanc h adsorbn sabiliy and/or adsorpion capaciy. In our laboraory, w hav bn involvd for qui som im in dvloping various yps of agriculural wass for h rmoval of havy mal

2 Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: 8 ions from waswar [-4]. Th prsn work was dircd a improving h capabiliy of CM rsidus for rmoving Hg (II) ions from aquous soluions. To achiv his goal, h following sudis wr undrakn: ) prparaion of hr lvls of CECM wih various nirogn conn using acrylamid in alkalin mdium; ) sablishmn of h condiions undr which h maximum adsorpion of Hg (II) ions ono CECM occur and 3) valuaion of h kinics for Hg (II) ion adsorpion ono CECM.. Exprimnal.. Marials Bio-dsorbn, Cornulaca monacanha, a dsr plan is widly sprad in Kingdom of Saudia Arabia. Thr is no prvious rpor usd, Cornulaca monacanha as adsorbn marial for rmoval of havy mals. Th roos wr sparad from h sms and lavs, washd wih disilld war svral ims o rmov h surfac adhrd paricls and war solubl paricls and drid in an lcric ovn for 4 h and ground using a mixr, and sivd o pass hrough a - mm. Th roos wr chosn bcaus hy conain h highs prcnag of h cllulos conn... Ragns Mrcuric aca, EDTA, hanol, sodium carbona, and acic acid wr of analyical ragn grad supplid by Mrck Company, Grmany..3. Mhods.3.. Prparaion of CECM Thr lvls of CECM wih various nirogn conns wr prpard by kping ohr racion condiions consan and varying h amoun of acrylamid according o a rpord mhod [5] as shown in Tabl. Th racion was carrid ou as follows: To a 4 ml bakr conaining g of CM wih paricl sizs in h rang - mm was addd a know wigh of acrylamid (dissolvd in h las amoun of war). Dfini volum of sodium hydroxid soluion of known concnraion was addd o h racion mixur undr coninuous sirring wih a spaula unil a homognous pas was obaind. Th pas was hn ransfrrd o a Erlnmyr flask and placd in a shaking war-bah a 6 C for h. Th rad sampl was subsqunly coold o room mpraur. Th solubl by-producs and any un-racd acrylamid and xcss alkali wr rmovd by washing h sampl svral ims wih a war:hanol (:8) mixur, and finally drid a 5 C for h. Tabl. Th characrisics of sampls of CECM. Cod sampl Unmodifid CM Acrylamid (mmol/l) NaOH mmol/l N% Adsorpion capaciy(mg/g) A B C Adsorpion Sudis A volum of ml of Hg (II) soluion wih a concnraion in h rang - 7 mg/l was placd in a 5 ml Erlnmyr flask. An accuraly wighd adsorbn sampl.5 g was hn addd o h soluion. A sris of such Erlnmyr flasks wr hn shakn a a consan spd of 5 rpm in a shaking war bah wih mpraurs 3 C. Afr shaking h flasks for h, h adsorbn was sparad by filraion. Th filra was analysd for h rmaining mal ion concnraion by iraion agains sandard EDTA soluion. Th amoun of adsorbd mal, q (mg/g) on adsorbn wr calculad according o h following quaion: q C C V l () W whr, C o and C ar h iniial and final concnraions of mal ion, mg/l. V is h volum of mal ion (l), W is h wigh of adsorbn (g)..4. Analyss.4.. Drminaion of Nirogn Conn (%) Th nirogn conn of CM and CECM sampls was drmind using h micro-kjldahl mhod [6]. Accuraly. g of h sampl was inroducd in Kjldahl digsion ub. 5 g K SO g CuSO 4 and ml conc. H SO 4 wr addd o h sampl. Th sampl was digsd for on h. ml of dionizd war was addd o h sampl afr allowing i o cool. Afr adding 5 ml of 4% NaOH, h sampl was hn disilld in Kjldahl apparaus and h ammonia librad was collcd in N boric acid and irad wih.3 N HCl. Th nirogn conn of CM or CECM was calculad as follows:.4 N% V N () W g whr, V is h volum of HCl consumd; N is h normaliy of sandard HCl; W is h wigh of h sampl (g)..4.. Saisical Error Analysis In h singl-componn isohrm sudis, h opimiza-

3 8 Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: ion procdur rquirs an rror funcion o b dfind o valua h fi of h isohrm o h xprimnal quilibrium daa. Th common rror funcions for drmining h opimum isohrm paramrs wr, avrag rlaiv rror (ARE), sum of h squars of h rrors (ERRSQ), hybrid fracional rror funcion (HYBRID), Marquard s prcn sandard dviaion (MPSD) and sum of absolu rrors (EABS) [7]. In h prsn sudy, h avrag rlaiv rror (ARE) was usd o drmin h bs fi in isohrm modl as: n i q q q xp. calc. ARE (3) 3. Rsuls and Discussion CECM was prpard by racing CM wih acrylamid in alkalin mdium. On racing CM wih acrylamid in alkalin mdium o obain carbamoylhylad Cornulaca monacanha (CECM), h following racion will occur: CH CH CO NH CM OH Acrylamid CM (4) CM CH OH CH CO NH CECM CECM sampls wr prpard in h form of a brown powdr having a paricl siz rang of 5 - mm as shown in Tabl. 3.. Facors Affcion Adsorpion of Hg (II) ono CECM 3... Effc of ph Earlir sudis hav indicad ha h ph of adsorba is an imporan paramr affcing bioadsorpion of havy mals. Figur shows h bioadsorpion capaciy of Hg (II) as a funcion of ph ( - 6) a fixd adsorbn concnraion, fixd agiaion im, fixd adsorba concnraion a 3 C. I is clar from his figur ha h adsorpion capaciy of Hg (II) ono CECM incrass by incrasing h ph from o 6. Undr highly acidic condi- xp. i ions (ph ) h adsorpion od Hg (II) on CECM is h lows bcaus mal binding sis on h adsorbn wr closly associad wih H 3 O + and rsric h approach of mal caions as a rsul of h rpulsion forcs. Howvr, adsorpion incrasd wih incrasing h ph of soluion sinc h adsorbn surfac could b xposd wih ngaiv charg wih subsqun aracion wih posiiv charg occurring ono h adsorbn surfac. A a ph valu highr han 6, h adsorpion xprimn could no b carrid ou du o prcipiaion of Hg (II) as Hg(OH) Effc of Adsorbn Concnraion Th ffc of adsorbn concnraion on adsorpion capaciy of Hg (II) by CECM is shown in Figur. Th adsorpion capaciy (q ), or h amoun of Hg (II) adsorbd pr uni mass of adsorbn (mg/g), dcrass by incrasing h concnraion of adsorbn. Th dcras in adsorpion capaciy wih incrasing h adsorbn concnraion is mainly du o ovrlapping of h adsorpion sis as a rsul of ovrcrowding of h adsorbn paricls and is also du o h compiion among Hg (II) ions for h surfac sis [4]. 3.. Effc of Exn of Modificaion Tabl shows h ffc of % N of h CECM on hir adsorpion capaciy of Hg (II) from conaminad war. Evidnly, incrasing h xn of modificaion is accomplishd by an incras in h adsorpion capaciy of CECM. I is logical ha h CECM wih h highr xn of modificaion has mor nirogn conn, which incrass h adsorpion abiliy oward Hg (II) hrough srongr complxaion. Currn daa suggs ha h carbamoyhyl groups inroducd in h molcular srucur of cllulos componn of h CM via hrificaion racion using acrylamid play a mor ffciv rol in h Hg (II) adsorpion procss han hos in h unmodifid CM as shown in Tabl Effc of Adsorba Concnraion Th quilibrium adsorpion isohrm is fundamnal 5 q (mg/g) ph Figur. Effc of ph on adsorpion capaciy of Hg (II) ono CECM a 3 C.

4 Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: 83 q (mg/g) Adsorbn Concnraion (g/l) Figur. Effc of adsorbn concnraion on adsorpion capaciy of Hg (II) ono CECM a 3 C. in dscribing h inraciv bhavior bwn solus and adsorbn, and is imporan in h dsign of adsorpion sysm. Figur 3 shows quilibrium disribuion of Hg (II) ions bwn h liquid phas, C (mg/l) and solid phas, q (mg/g). Th quilibrium curv plaau indicas h maximum adsorpion capaciy of Hg (II) ions on CECM a 3 C. As shown in Figur 3 h adsorpion capaciy of Hg (II) ono CECM incrass wih h incrasing concnraion of adsorba and approachs h quilibrium a highr concnraion of h adsorba. To simula h adsorpion isohrm, hr modls ar commonly usd, h Langmuir, Frundlich, and Tmkin isohrms Langmuir Isohrm Langmuir quaion [8] was applid for adsorpion quilibrium of Hg (II) ions by CECM. Th assumpion of his modl is basd on h maximum adsorpion corrsponds o a saurad monolayr of adsorba molculs on h adsorbn surfac and h nrgy of adsorpion is consan as wll as hr is no ransmigraion of adsorba in h plan surfac. Th linar form of Langmuir isohrm is givn by h following quaion: kl C q (5) a C whr, a L is Langmuir isohrm consan (l/mg), K L is h Langmuir consan (l/g) and a L /K L rprsns h adsorpion capaciy, Q max. Th linar quaion of his modl could b rprsnd by: L C a L C q KL KL Th linar plos (Figur 4) of C /q vs C giv sraigh lins wih h slop a L /K L and inrcp /K L. Th Langmuir consans of adsorpion of Hg (II) ions ono CECM ar lisd in Tabl. Th quilibrium consan K L may b usd o drmin h nhalpy of adsorpion, H. Th (6) q (mg/g) C (mg/l) Figur 3. Equilibrium adsorpion isohrm of Hg (II) ono CECM a 3 C..5 C /q (g/l).5 y =.x +.49 R² = C (mg/l) Figur 4. Langmuir adsorpion plo of Hg (II) ono CECM a 3 C.

5 84 Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: Tabl. Consans of adsorpion modls and h avrag rlaiv rror (ARE) for Hg (II) ono CECM a 3 C. Langmuir Consans Frundlich Consans Tmkin Consans Q max b R L valus R ARE n k F R ARE A T B T R ARE rlaion bwn K L and Q max is givn by h following quaion: kl Q whr, b is rlad o h nrgy of adsorpion (l/mg). Th valu of consan b and corrlaion cofficin, R ar also lisd in Tabl. Th ssnial faurs of Langmuir isohrm can b xprssd in rms of a dimnsionlss consan sparaion facor or quilibrium paramr, R L, which xprssd by h following quaion: R L max b bc whr C o is h iniial concnraion of Hg (II) and b is mniond bfor. Th R L valu of Hg (II) ono CECM a 3 C is givn in Tabl. I has bn rpord ha h ffc of isohrm shap wih a viw o prdicing if an adsorpion sysm is favourabl or unfavorabl [9]. I is known ha h valu of R L < rprsns favorabl adsorpion and valu of R L > rprsns unfavorabl adsorpion. In our cas h valu of R L for iniial Hg (II) concnraions in h rang of of was found o b ( < R L < ). This val indicas ha h adsorpion is favorabl. Th valus of h corrlaion cofficins, R of Langmuir plo was ovr.98 Hg (II) on CECM indica ha h adsorpion of Hg (II) ono CECM is fid wll on h Langmuir isohrm (oby h Langmuir isohrm) Frundlich Isohrm Th Frundlich quaion [] is mployd o dscrib hrognous sysms and rvrsibl adsorpion and is no rsricd o h formaion of monolayr. Th adsorpion daa of Hg (II) is analyzd also by Frundlish modl. Th logarihmic form of Frundlich modl is givn by h following quaion: n F (7) (8) q K C (9) whr, q is h quilibrium concnraion mrcury on CECM (mg/g), C h quilibrium concnraion of mrcury in soluion (mg/l) and K F (mg/g) and n ar h Frundlich consans characrisic of h sysm, indicaors of adsorpion capaciy and adsorpion innsiy, rspcivly. Th linar form of Frundlich quaion is: log q log KF log C () n whr q is h amoun of Hg (II) ions adsorbd pr uni mass of adsorbn (mg/g), C is h quilibrium concnraion of Hg (II) ions, mg/l. Linar plos of log q vs log C a a 3 C (Figur 5) suggs h applicabiliy of adsorpion procss of Hg (II) ono CECM on Frundlich isohrm. Th valus of K F and n wr valuad from h inrcp and h slop of h plo and hir numrical valus ar lisd in Tabl. Th n valu givs an indicaion o favorabiliy of adsorpion. Th valus of n was.3 a 3 C ( < n < ) showing ha h adsorpion of Hg (II) ions ono CECM is favourabl. Th corrlaion cofficin, R valu (Tabl ) of Hg (II) by CECM was ovr.98 indicaing ha h adsorpion of Hg (II) ions on CECM is fid wll also on Frundlish isohrm (oby h Frundlish isohrm) Tmkin Isohrm Th Tmkin isohrm [] has bn usd in h following form: RT q ln ATC () b T whr R is h univrsal gas consan (8.344 J mol K ), T is h absolu mpraur (K), A T is h Tmkin isohrm consan (g/mg) and b T is Tmkin consan. Th sorpion daa wr analyzd according o h linar form of h Tmkin isohrm as: RT RT q ln AT ln C () bt bt Linar plos of q vs lnc a 3 C (Figur 6) suggs h applicabiliy of adsorpion procss of Hg (II) ono CECM on Tmkin isohrm. Th valus of A T and b T wr valuad from h inrcp and h slop of h plo and hir numrical valus along wih R ar lisd in Tabl. R valu of Hg (II) by CECM was ovr.94 indicaing ha h adsorpion of Hg (II) ions on CECM is fid wll also on Tmkin isohrm (oby h Tmkin isohrm). Th comparison bwn h xprimnal daa and h horical daa obaind from isohrm modls of Hg (II) ono CECM ar shown in Figur 7 and Tabl which illusras ha h Langmuir isohrm fid h xpri-

6 Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: 85 log q y =.49x +.34 R² = log C Figur 5. Frundlich adsorpion plo of Hg (II) ono CECM a 3 C. q y = 43.8x R² = lnc Figur 6. Tmkin adsorpion plo of Hg (II) ono CECM a 3 C. Figur 7. Comparison bwn diffrn isohrm modls of Hg (II) ono CECM a 3 C. mnal daa br han ohr isohrms Error Analysis Th us of R is limid o solv linar forms of isohrm quaion, which masurs h diffrnc bwn xprimnal and horical daa in linarizd plos only, bu no h rrors in non-linar form of isohrm curvd. For his rason w us avrag rlaiv rror (ARE) o drmin h bs fi in isohrm modls. For all isohrm modls, h valu of ARE for adsorpion of Hg (II) ono CECM ar calculad and prsnd in Tabl. Th mos obvious conclusions from hs rsuls ar ha h Langmuir isohrm modl has h lows valus for ARE and hrfor fis h daa br han h rs of isohrm modls Effc of Iniial Mal Concnraion and Conac Tim Figur 8 shows h ffc of agiaion im on adsorpion capaciy of Hg (II) ono CECM by using h concnraion of 4 and 5 mg/l a fixd adsorbn concnraion and a 3 C. Th amoun of Hg (II) adsorbd (mg/g) incrass wih h incras in agiaion im and rachd h quilibrium afr min for boh Hg (II) concnraions. I is clar ha h adsorpion capaciy dpnds on h concnraion of h Hg (II) ions. Th adsorpion

7 86 Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: Figur 8. Effc of conac im and iniial concnraion on adsorpion capaciy of Hg (II) CECM a 3 C. curvs ar singls and coninuous lading o sauraion Adsorpion Kinics Psudo-Firs-Ordr Modl Th psudo-firs-ordr quaion [] is: dq d k q q (3) whr q is h amoun of adsorba adsorbd a im (mg/g), q is h adsorpion capaciy a quilibrium (mg/g), k is h psudo-firs-ordr ra consan (min ), and is h conac im (min). Th ingraion of Equaion (3) wih h iniial condiion, q = a =, h following quaion is obaind: log k q qlog q (4).33 In ordr o obain h ra consans, h sraigh lin plos of log(q q ) agains for Hg (II) ono CACM hav bn sd. Th inrcp of his plo should giv logq. Howvr, if h inrcp dos no qual o h quilibrium upak of mal ions, h racion is no likly o b firs ordr vn if his plo has high corrlaion cofficin (R ) wih h xprimnal daa [3]. For h daa obaind in h prsn sudy, h plos of log (q q ) vrsus as rquird by Equaion (3) for h adsorpion of Hg (II) ions a iniial concnraions of 4, and 5 mg/l by CECM (figur no show) gav corrlaion cofficins, R, which had low valus for h wo plos concrnd. This indicas ha h adsorpion of Hg (II) ono CECM is no accpabl for his modl Psudo-Scond-Ordr Modl Th psudo-scond-ordr modl [4] is rprsnd as: dq d k q q (5) whr k is h psudo-scond-ordr ra consan (g/mg min). Ingraing Equaion (5) wih h iniial condiion, q = a =, h following quaion is obaind: q k q q (6) whr, k is h psudo-scond-ordr adsorpion ra consan. This quaion prdics ha if h sysm follows psudo-scond-ordr kinics, h plo of /q vrsus should b linar. Ploing h xprimnal daa obaind for h adsorpion Hg (II) ions a iniial concnraions of 4 and 5 mg/l ono CECM according o h rlaionship givn in Equaion (6) gav linar plos wih corrlaion cofficins, R, of.9999 and.9998 for Hg (II) concnraions of 4 and 5 mg/l, rspcivly, as shown in Figur 9 and lisd in Tabl 3, hrby indicaing h applicabiliy of h psudo-scond-ordr kinic quaion o h xprimnal daa. Th xprimnal and calculad adsorpion capaciis for h wo Hg (II) concnraions as wll as h valus of k, and R ar also prsnd in Tabl 3. Th firs-ordr and psudo-scondordr modls canno idnify h diffusion mchanism and h kinic rsuls wr hn subjcd o analyz by h inra-paricl diffusion modl. 3.. Inra-Paricl Diffusion Th inra-paricl diffusion modl [5] can b xprssd by h following quaion: P q k C (7) whr, k p is h inra-paricl diffusion ra consan (mg g min / ) and q is h amoun of solu adsorbd pr uni mass of adsorbn. Th daa of solid phas mal concnraion agains im a h iniial concnraions of 4 and 5 mg/l of Hg (II) wr furhr procssd for sing h ra of diffusion in h adsorpion procss. Adsorpion procss incorporas h ranspor of adsorba from h bulk soluion o h inrior surfac of h pors in CECM. Th ra paramr for inra-paricl diffusion, k p for h wo concnraions of Hg (II) ar masurd according o Equaion (7). Th plos of q vrsus / for h concnraions of 4 and 5 mg/l of Hg (II) ar shown in Figur. Th plos for wo concnraions of mal ions hav h sam faurs, h iniial porion (curvd) followd by linar porion and plaau. Th iniial curvd porion is aribud o h bulk diffusion and h linar porion o h inra-paricl diffusion, whil h plaau corrsponding o quilibrium. Th dviaion of sraigh lins from h origin (Figur ) may b bcaus of h diffrnc bwn h ra of mass ransfr in h iniial and final sags of adsorpion. Furhr, such dviaion of sraigh lin from h origin indicas ha h por diffusion is no h ra-conrolling sp [6]. Th valus of k p (mg g min ) obaind from h slop of h sraigh lins (Figur ) ar lisd in

8 Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: 87 Figur 9. Psudo-scond ordr racion of Hg (II) ono CECM using diffrn adsorba concnraions a 3 C. q / Figur. Inra-paricl diffusion of Hg (II) ono CECM using wo diffrn adsorba concnraions a 3 C. q (mg/g) y =.67x R² =.99 y =.565x + 5. R² = / Figur. Ts of inra-paricl diffusion of Hg (II) ono CECM using wo diffrn adsorba concnraions a 3 C. Tabl 3. Kinic paramrs for adsorpion of Hg (II) ono CECM a 3 C. Ini. Conc. Psudo-scond ordr Inra-paricl diffusion (mg/l) k q (xp.) q (calc) R k p C R Tabl 3. Th valus of R for h wo plos ar lisd also in Tabl 3. Ths valus indica ha h adsorpion of Hg (II) ono CECM may b follow h inra-paricl diffusion mchanism. Th valus of inrcp, C (Tabl 3) giv an ida abou h boundary layr hicknss, i.., h largr h inrcp, is h grar h boundary layr ffc [7]. 3.. Mchanism of Adsorpion Th CECM can b considrd o b microporous biopolymr; hrfor, pors ar larg nough o l Hg (II) ions hrough. Th mchanism of Hg (II) adsorpion on porous adsorbns may involv four sps: ) diffusion of ions o h xrnal surfac of h adsorbn; ) diffusion of ions ino h pors of h adsorbn; 3) adsorpion of h ions on h inrnal surfac of h adsorbn; 4) chlaion bwn h lcron donaing naur of O- and N-conaining groups in h CECM and h lcronaccping naur in h Hg (II) as shown in Schm. 4. Conclusion Cornulaca monacanha (CM) a dsr plan has bn uilizd as adsorbn marial for h rmoval of Hg (II) ions from conaminad war afr ramn wih acry-

9 88 Chmically Modifid Cornulaca monacanha Biomass for Bioadsorpion of Hg (II) from Conaminad War: Schm. Schmaic prsnaion of proposd complx srucur bwn CECM and Hg (II) ions. lamid in alkalin mdium o form carbamoylhylad Cornulaca monacanha (CECM). Thr lvls of CECM having diffrn nirogn conn wr prpard. Th CECM sampls wr characrizd by simaing h nirogn conn. Th abiliy of CECM o adsorb Hg (II) was invsigad by using bach adsorpion procdur. Th daa of h adsorpion isohrm was sd by h Langmuir, Frundlich and Tmkin modls. Th rmoval of Hg (II) ono CECM paricls could b wll dscribd by h psudo-scond ordr modl. Th adsorpion ra of mrcury was affcd by h iniial Hg (II) ion concnraion, iniial ph, adsorbn concnraion and agiaion im as wll as xn of modificaion. Th adsorpion xprimns indicad ha h CECM paricls hav gra ponial for h rmoval of Hg (II) from conaminad war. Th maximum adsorpion capaciy, Q max of h CECM owards Hg (II) ions was found o b mg/g a 3 C. Similarly, h Frundlich consan, n was found o b.3 a 3 C. REFERENCES [] S. E. Manaham, Environmnal Chmisry, 7h Ediion, CRC Prss, Boca Raon,. [] M. H. Yu, Environmnal Toxicology Biological and Halh Effcs of Polluans, nd Ediion, CRC Prss, Boca Raon, 5. [3] A. Hashm, A. M. Azzr and A. Ayoub, Rmoval of Hg (II) Ions from Laboraory Waswar ono Phosphorylad Haloxylon Ammodndron: Kinic and Equilibrium Sudis Polymr-Plasics, Tchnology and Enginring, Vol. 49, No. 4,, pp [4] O. J. Esalah, M. E. Wbr and J. H. Vra, Rmoval of Lad, Cadmium and Zinc from Aquous Soluions by Prcipiaion wih Sodium Di-(n-ocyl) Phosphina, Th Canadian Journal of Chmical Enginring, Vol. 78, No. 5,, pp doi:./cjc [5] A. I. Zouboulis, K. A. Mais, B. G. Lanara and C. L. Nskovic, Rmoval of Cadmium from Dilu Soluions by Hydroxyapai. II. Floaaion Sudis, Sparaion Scinc and Tchnology, Vol. 3, No., 997, pp doi:.8/ [6] V. Ravindran, M. R. Svns, B. N. Badriyha and M. Pirbazari, Modling h Sorpion of Toxic Mals on Chlan-Imprgnad Adsorbn, AIChE Journal, Vol. 45, No. 5, 999, pp doi:./aic [7] C. A. Tols and W. E. Marshall, Coppr Ion Rmoval by Almond Shll Carbons and Commrcial Carbons: Bach and Column Sudis, Sparaion Scinc and Tchnology, Vol. 37, No.,, pp doi:.8/ss-358 [8] L. Can, M. Ilpid and P. Sa, Efficin Faciliad Transpor of Lad, Cadmium, Zinc and Silvr across a Fla Sh-Suppord Liquid Mmbran Mdiad by Lasalocid A, Sparaion Scinc and Tchnology, Vol. 37, No. 8,, pp doi:.8/ss-347 [9] M. M. Nassar and M. S. El-Gundi, Comparaiv Cos of Color Rmoval from Txil Effluns Using Naural Adsorbns, Journal of Chmical Tchnology & Biochnology, Vol. 5, No., 99, pp doi:./jcb.85 [] G. McKay, Adsorpion of Dysuffs from Aquous Soluions wih Acivad Carbon, Par I: Equilibrium and Bach Conac-Tim Sudis, Journal of Chmical Tchnology & Biochnology, Vol. 3, No. 7-, 98, pp doi:./jcb [] A. Hashm and K. A. El-Khraij, Biosorpion of Pb (II) ono Anhum gravolns from Conaminad Waswar: Equilibrium and Kinic Sudis, Journal of Environmnal Procion, Vol. 4, No., 3, pp [] A. Hashm, H. A. Hussin, M. A. Sanousy, E. Adam and E. E. Saad, Modifid Monomhylolad Thioura Sawdus as a Nw Adsorbn for Rmoval of Hg (II) from Conaminad War: Equilibrium Kinic and Thrmodynamic Sudis, Polymr Plasics Tchnology and Enginring, Vol. 5, No.,, pp. -3. doi:.8/ [3] A. Al Ohman Zid, M. A. Habila and A. Hashm, Rmoval of Zinc (II) from Aquous Soluions Using Modifid Agriculural Wass: Kinics and Equilibrium Sudis, Arabian Journal of Goscincs, Vol. 5,, pp. -. [4] A. A. Khalil, H. H. Sokkr, A. Al-Anwar, A. Abd El- Zahr and A. Hashm, Prparaion, Characrizaion and Uilizaion of Amidoximad Poly (AN/MAA)-Grafd Alhagi Rsidus for h Rmoval of Zn (II) from Aquous Soluion, Adsorpion Scinc& Tchnology, Vol. 7, No. 4, 9, pp doi:.6/ [5] A. Raghb, R. Rfai, I. Abd El-Thalouh and A. Hbish, Th Combind Effc of Oxidaion and Carbamoylhylaion on h Rhological Propris of Maiz and Ric Sarchs, Sarch, Vol. 4, No., 99, pp

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