Adsorption of Humic Acid from Aqueous Solution on Single-Walled Carbon Nanotubes

Transcription

1 Asan Journal of Chmstry; Vol. 5, No. 1 (13, Adsorpton of Humc Acd from Auous Soluton on Sngl-Walld Carbon Nanotubs S.P. MOUSSAVI 1, M.H. EHRAMPOUSH, A.H. MAHVI 3, M. AHMADIAN 4 and S. RAHIMI 4,* 1 Faculty of Publc Halth, Intrnatonal Branch of Shahd Sadough Unvrsty of Mdcal Scncs and Halth Srvcs, Yazd, Iran Profssor of Envronmntal Halth Engnrng, Faculty of Publc Halth, Shahd Sadough Unvrsty of Mdcal Scncs, Yazd, Iran 3 Assstant Profssor of Envronmntal Halth Engnrng, Faculty of Publc Halth, Thran Unvrsty of Mdcal Scncs, Thran, Iran 4 Socal Dvlopmnt & Halth Promoton Rsarch Cntr, Krmanshah Unvrsty of Mdcal Scncs, Krmanshah, Iran *Corrspondng author: Fax: ; Tl: ; E-mal: sj.rahm@yahoo.com (Rcvd: 7 Jun 1; Accptd: 1 Aprl 13 AJC Humc acd s on of th most mportant componnts of humc substancs. Its prsnc n watr dosn't drctly caus toxcty but can ndrctly caus undsrabl ffcts on apparanc and tast of watr. It can also rsult n producton of undsrabl and hazardous products known as dsnfctant by-products. In ths rsarch, adsorpton of humc acd was xamnd usng sngl-walld carbon nanotubs (SWCNTs. Also, th ffct of ffctv paramtrs on adsorpton procss ncludng adsorbnt dos, ntal concntraton of humc acd, contact tm and ntal soluton ph wr valuatd. Accordng to rsults, as ph ncrass, humc acd adsorpton ncrass too. Also, as adsorbnt dos and contact tm ncras, th absorpton of humc acd ncrass too. Rsults obtand from ths study rvald that sngl-walld carbon nanotubs ar abl to rmov humc acd compltly n dffrnt concntratons. Thrfor, t can b concludd that sngl-walld carbon nanotubs ar consdrd powrful adsorbnts for rmovng humc acd from auous solutons. Ky Words: Humc acd, Sngl-walld carbon nanotubs, Adsorpton, Auous soluton. INTRODUCTION Contamnaton of surfac watr and ncssty of accssng nw watr rsourcs s on of th bggst problms of most dvlopng countrs. Ths has allocatd most natonal and ntrnatonal plans to tslf. Most watr rsourcs throughout th world spcally surfac and groundwatr hav hug amounts of natural organc mattrs (NOMs. Natural organc mattrs ar a product of dgradaton of auous plants and alga avalabl n surfac watr rsourcs 1. Ths mattrs ar a complx and htrognous mxtur of varous organc compounds wth dffrnt molcular sz and proprts; thy ar dvdd nto two man humc and non-humc componnts. Rato of humc mattrs to non-humc mattrs vars dpndng on th sasons of th yar. Th man NOMs ar humc substancs (HSs whch nclud humc acd, fulvc acd and humns -5. Humc substancs ar th most mportant actv componnts of NOMs whch can b found n sols, sdmnts, surfac watr and groundwatr. Prsnc of HSs can caus a lot of problms n natural watrs 6-8. Not only dos thr prsnc n watr affct smll, colour and tast of watr but also t affcts svral procsss n purfcaton of drnkng watr. Durng chlornaton, HSs caus th formaton of carcnognc compounds lk trhalomthans (THMs. Thy also ncras th formaton of boflm n watr purfcaton and dstrbuton systms and caus mmbran obstructon. Ths compounds consum chmcals whch ar usd for watr purfcaton and wll consuntly ncras purfcaton xpnss. Thrfor, rmovng HSs s consdrd on of th most ssntal nvronmntal ssus 9-1. Humc acds (HAs ar th man HSs compounds whch xst n surfac watrs. Humc acds ar usually solubl n alkaln solutons, whl thy ar nsolubl n acdc solutons (ph <,3. Prsnc of HAs n watr dosn't drctly caus toxcty but can (aftr dsnfcton procss rsult n th producton of undsrabl and dangrous products calld dsnfctant by-products (DBPs. Humc acd s th man prcursor of formaton of DBPs n natural watrs Convntonal tratmnt procsss of drnkng watr rmov only -5 % of HSs from watr. Thrfor, t s vry crtcal to mak us of a sutabl procss to rmov th rmanng humc acd from drnkng watr wth hgh amounts of HAs pror to dsnfcton procss 5,1. Snc rmoval of HSs from watr s ssntal, svral mthods (.g. chmcal coagulaton, mmbran sparaton, adsorpton and advancd oxdaton hav bn dvlopd to rmov thm 4,14. Among thm, adsorpton mthod has bn takn nto hghr consdraton and makng us of ffctv adsorbnts n rmovng humc acd from drnkng watr has bn rgardd as a sutabl mthod 1. Varous adsorpton mthods (.g., makng us of actv carbon, zolt and clay hav bn xamnd n

2 53 Moussav t al. Asan J. Chm. ths rgard 7,15,16. Carbon nanotubs (CNTs ar a nw typ of carbon nanomatrals whch wr dscovrd n 1991 by Ijama. Carbon nanotubs ar dvdd nto two catgors ncludng sngl-walld carbon nanotubs (SWCNTs and mult-walld carbon nanotubs (MWCNTs Carbon nanotubs, as nw adsorbnts, hav bn takn nto hug account. Thy ar consdrd powrful adsorbnts for rmovng organc and norganc contamnants from watr bcaus of thr unu proprts lk thr small sz, larg spcfc surfac and ara, hallow and tub-lk structur, hgh mchancal strngth and lctrc conducton. Carbon nanotubs ar also consdrd nw adsorbnts for prcondnsaton and purfcaton of rado-nuclotd mattrs n hug volums of wastwatr. Many rsarchrs hav rportd that applcaton of ths nano-mattrs s most sutabl and postv n rmovng and purfyng contamnants lk mcro-pollutants, havy mtals, rado-nuclotds, chmcal organc compounds and dangrous matrals from gas flows -3. Carbon nanotubs ar formd from carbon pur macromolculs; carbon atom flm s bond n hxagonal arrays and form cylndrcal shaps. Fg. 1 shows ntrnal structur of a SWCNT 3-5. Fg.. SEM photograph of SWCNTs Fg. 3. TEM mags of SWCNTs (Htach-Japan, Modl S-37N and transmsson lctron mcroscopy (TEM (Htach-Japan, modl H-7 of SWCNT ar shown, rspctvly. BET of th sngl-walld carbon nanotubs whch usd n ths study s prsntd n Tabl-1. Fg. 1. Dffrnt adsorpton sts on a homognous bundl of partally opn-ndd SWCNTs: (1 ntrnal, ( ntrsttal channl, (3 xtrnal groov st and (4 xtrnal surfac 5 Th am of th prsnt rsarch s to study th ffct of paramtrs such as adsorbnt dos, ntal concntraton of humc acd, contact tm and ntal ph of soluton on humc acd adsorpton ffcncy by sngl-walld carbon nanotubs (SWCNTs. EXPERIMENTAL Sampl prparaton: Humc acd was purchasd from Aldrch Chmcal Company and SWCNT was purchasd from Industral Rsarch Cntr of Iran Ol Company n Thran. Sngl-walld nanotubs wth outr damtr of 1- nanomtrs, nnr damtr of nanomtrs, surfac ara of 7 m /g, lngth of 1 µm and purty of 95 % wr usd n ths rsarch as an adsorbnt. Stock soluton usd hr was prpard synthtcally from dssoluton of humc acd powdr n dstlld watr wth concntraton of mg/l. All solutons wr prpard n.1 M NaCl, whch was th background lctrolyt usd n th xprmnts. Charactrzaton of SWCNTs: Ths rsarch was undrtakn n laboratory scal and SWCNTs wr usd to rmov humc acd from auous solutons. In Fgs. and 3, pcturs rlatd to scannng lctron mcroscopy (SEM TABLE-1 BET OF THE SINGLE-WALLED CARBON NANOTUBES Surfac Outr Innr Avrag Purty Sorbnt ara damtr damtr lngth (m (% /g (nm (nm (µm SWCNT Batch adsorpton xprmnts: Exprmnts wr don n a batch systm usng crtan concntratons of humc acd and crtan concntratons of SWCNTs. All compounds bng suspndd n.1 M NaCl mdum as background lctrolyt. Exprmnts wr carrd out at 3.3 ºC n a closd 5 ml glass pyramd bottl whch contand ml of humc acd soluton. Glass pyramd bottl wr placd n an ncubator orbtal shakr (ncubator shakr GFL137 at 1 rpm. Th ph of ach suspnson was adjustd to th approprat valu usng.1 N HCl or NaOH and ph was masurd by ph mtr. In ach cas, a blank that usd to valuat th adsorpton background was prpard usng th sam xprmntal condtons. At th nd of th ulbrum prod, thn th suspnsons wr fltrd usng by. µm actat cllulos fltr papr (Cartrus, Grmany for ultmat analyss of th acd humc concntraton. Th adsorpton of humc acd was dtctd usng a UV-VIS spctrophotomtr (SP-3 Puls-Japan at 54 nm. Absorbanc masurmnts wr carrd out n a 1 cm uartz cll on a SP-3 Puls-Japan spctrophotomtr.

3 Vol. 5, No. 1 (13 Adsorpton of Humc Acd from Auous Soluton on Sngl-Walld Carbon Nanotubs 531 Calbraton curvs wr obtand as th sampls and blanks undr th sam xprmntal condtons. Each xprmnt was prformd thr tms and xprmntal rsults wr avrag valus. Th amount of humc acd adsorbd pr unt mass of SWCNTs at ulbrum (mg/g, was calculatd from th followng uaton: (C C V = W whr V s th volum of humc acd soluton n ltrs, C and C ar th ntal and ulbrum concntratons, rspctvly, of th humc acd solutons n mg/l and W s th mass of adsorbnt usd (g. Effct of ph and contact tm on adsorpton procss: To xamn th ffct of ph on adsorpton procss, humc acd solutons wth ntal concntratons of 5 mg/l wr prpard. ph of solutons wr adjustd by.1 N HCl or.1 N NaOH n thr acdc, nutral sand alkaln condtons (4, 7 and 1, rspctvly..6 g of adsorbnt was addd to ml of vry soluton and wr strrd for 3 h; samplng was don n tm ntrval of.5 h and n 6 dffrnt contact tms. Fnally, suspnson was fltrd usng. µm actat cllulos papr fltr and thn th lvl of th rmanng humc acd was valuatd. Effct of ntal humc acd concntraton on adsorpton procss: To xamn th ffct of dffrnt ntal humc acd concntraton on adsorpton procss, humc acd solutons wth volum of ml and ntal concntratons of 5, 1, and 3 mg/l wr prpard. Thn, thr ph was adjustd at 4 by HCl or NaOH..4 g of adsorbnt was addd to vry soluton and wr strrd for 1 mn; samplng was don n tm ntrval of.5 h. Fnally, suspnson was fltrd usng. µm actat cllulos papr fltr and thn th lvl of th rmanng humc acd was valuatd. Effct of adsorbnt dosag on adsorpton procss: To xamn th ffct of adsorbnt dos on absorpton procss, humc acd solutons wth volum of ml and ntal concntraton of mg/l wr prpard. Thn varous amounts of adsorbnt (.,.4,.6,.8 and.1 g wr addd to th mntond solutons and wr strrd for 4 h. Thr ph was mantand at 4 usng HCl or NaOH. Fnally, suspnson was fltrd usng. µm actat cllulos papr fltr and thn th lvl of th rmanng humc acd was valuatd. RESULTS AND DISCUSSION Effct of ph and contact tm: Th ffct of ph on adsorpton procss of HA was analyzd usng SWCNT. Gnrally, adsorpton of HA dpnds on ph of soluton. Soluton ph s an mportant paramtr n adsorpton procss bcaus t affcts th ntracton btwn functonal groups of adsorbnt and adsorbat. Soluton ph s also an mportant control paramtr whch affcts adsorpton lvl of humc acd molculs on adsorbnt surfac. To study th ffct of ph on adsorpton of HA, batch xprmnts wr carrd out n dffrnt phs (Fg. 4. As shown hr, as ph dcrass from 1-4, adsorpton lvl of humc acd ncrass and th hghst adsorpton lvl s obsrvd n ph of 4. Anothr sgnfcant proprty of humc acd s ts sz and molcular strucutr whch HA Rmoval (% Fg. 4. ph: 4 ph: 7 ph: Tm (mn Effct to ph soluton and contact tm on HA rmoval by SWNT (HA: mg/l, SWNT dos:.6 g/ml changs to a sphrcal shap n low phs and to a lnar or xtndd structur n hgh phs; t may dcras adsorpton of humc acds n hghr phs 1,3,6,7. Thus, sz of humc acd macromolculs can b anothr factor whch s rlatd to dcrasd adsorpton capacty n low ph. Th ffct of contact tm on adsorpton procss has bn shown n Fg. 4. Accordng to ths fgur, as contact tm ncrass from -1 mn, adsorpton capacty of humc acd ncrass too. Accordng to rsults obtand from contact tm curv, th hghst adsorpton lvl occurs n th frst 1 h. As tm of contact ncrass mor than 1 h, adsorpton lvl dosn't chang sgnfcantly and stablzs; thus, th optmum lvl can b achvd at 1 h. Ths rsults show that adsorpton procss of humc acd s vry fast usng SWCNTs and ths phnomnon s rlatd to a larg numbr of vacant surfac sts avalabl on adsorbnt surfac n ntal stags of adsorpton procss. As tm passs, th rmanng vacant surfac sts ar toughly occupd by adsorbat du to rpulsv forcs among molculs of solut on sold and bulk phass 1-5. Effct of HA ntal concntraton: Th adsorpton capacty of HA s a functon of humc acd ntal concntraton. To study th ffct of HA ntal concntraton on adsorpton procss, solutons wth ntal concntratons of 5, 1, and 3 mg/l wr usd (Fg. 5. Th ntal HA concntratons provd an mportant drvng forc to ovrcom th mass transfr rsstanc of th HA btwn th auous phass and th sold phass, so ncrasng ntal concntratons would nhanc th adsorpton capacty of humc acd. It s logcal n ths mattr that actv adsorpton sts avalabl on adsorbnt ar lowr n ntal concntratons du to vry hgh ratos,4,5. Th ulbraton tm for th adsorpton of HA at dffrnt concntratons rangd btwn 15 and 1 mn. Wth dcrasng ntal humc acd concntratons, adsorpton rat ncrasd. Effct of adsorbnt dos: Adsorbnt dos s on of th most mportant paramtrs n adsorpton procss whch s as a rsult of ffctv rol of adsorbnt capacty for adsorbng pollutants on ts surfac. In ths rsarch, th ffct of adsorbnt dos on HA adsorpton procss was analyzd usng SWCNT (Fg. 6. As shown n ths fgur, as adsorbnt lvl ncrass, HA adsorpton procss ncrass too. It s as a rsult of ncrasd numbr of adsorpton sts for a crtan lvl of adsorbat or HA. Intally, rapd ncras n adsorpton wth th ncras n adsorbnt dos can b attrbutd to gratr surfac ara and avalablty of mor adsorpton sts 5,1,13.

4 53 Moussav t al. Asan J. Chm. HA Rmoval (% 1 Fg (mg/l 1 (mg/l (mg/l 3 (mg/l 5 15 Tm (mn Effct of ntal HA concntratons on HA adsorpton (SWNT dos:.4 g/l, ph: 4 Isothrm adsorpton curvs of humc acd (usng SWCNTs ar shown n Fg. 7. Accordng to ths fgurs, xprmnt rsults can b dscrbd and dfnd by Langmur and Frundlch sothrm modl. Th Frundlch sothrm dscrbs rvrsbl adsorpton and s not rstrctd to th formaton of th monolayr. Th Frundlch uaton prdcts that th HA concntraton on th adsorbnt wll ncras so long as thr s an ncrasd n th HA concntraton n th lud. Summary of th paramtr stmats for HA adsorpton on SWCNTs ar shown n Tabls 3 and 4. Th rsult shows that Frundlch sothrm bst-ft th ulbrum data for adsorpton of HA on SWCNTs. BET Frundlch F-P Langmur GLF Exp (mg/g 1 Rmoval SWNT dos (g/l Fg. 6. Effct of SWNT dos on adsorpton of HA (HA: mg/l, ph: 4 and 4 h contact tm Adsorpton sothrm xprmnts: Applcaton of adsorpton sothrms, whch ar usd for dscrpton of ntracton btwn adsorbnt and adsorbat n varous systms, s vry usful. Th sothrm uatons usd n ths study ar prsntd n Tabl-. TABLE- ISOTHERM EQUATIONS FOR HA ADSORPTION ON SWNT Isothrm Euaton Rf. Lnar = KpC 8 Brunaur-Emmtt- QbC = 9 Tllr (BET (S C [1 + (b 1(C /S ] Frundlch Frundlch wth lnar parttonng (F-P Gnralzd Langmur-Frundlch (GLF Langmur Langmur wth lnar parttonng (L-P Polany Polany wth lnar parttonng (P-P w (1/ nf f w = K C 3 (1/n f f = K C + K C 31 p (1/ ng (1/ ng Q(bC = 3 1+ (bc QbC = bc QbC = + KpC bc B A[log(S w / C ] Q1 = 35 B A[log(S w / C ] + = Q 1 K C 35 QbC Toth = n t (1/ n t [1 + (bc ] p 36 HA rmoval (% (mg/g (mg/g C (mg/l L-P Lnar Polany P-P Toth Exp C (mg/l Fg. 7. Isothrms for th adsorpton of HA onto th SWCNTs Adsorpton kntc xprmnts: Th uaton and lnar form of kntcs usd n ths study ar prsntd n Tabl- 5. Adsorpton of HA on SWCNTs showd smlar kntc bhavours for th dffrnt HA concntraton. Kntc adsorpton curvs of humc acd (usng SWCNTs ar shown n Fg. 8. At frst, humc acd s adsorbd rapdly and aftr 1 h th hghst adsorpton lvl for varous concntratons of 5, 1, and 3 mg/l was 95 %. Eulbrum tm n adsorpton xprmnts was fxd to dtrmn kntc (3 h to guaranty ulbrum adsorpton. Psudo-scond-ordr kntc modl was mor sutabl for rmovng HA on SWCNTS and was bttr than psudo-frst-ordr modl. Thus, kntc constants wr calculatd accordng to psudo-scond-ordr kntc modl. It s rasonabl to conclud that th ractvty of th SWCNTs hav sgnfcantly hghr dnsty of actv sts du to ts trmndous SWCNTs and thus xhbt strongr affnty to th HA. Th paramtrs obtand from varous kntcs modls ar prsntd n Tabl-6.

5 Vol. 5, No. 1 (13 Adsorpton of Humc Acd from Auous Soluton on Sngl-Walld Carbon Nanotubs 533 TABLE-3 SUMMARY OF PARAMETER ESTIMATES FOR HUMIC ACID ADSORPTION ON SWCNTs Isothrm Paramtr Estmat Cl Low Cl Hgh Isothrm Paramtr Estmat Cl Low Cl Hgh b Q b Q BET b.76 n/a n/a b L-P 6 Q n/a n/a Q n/a n/a Frundlch K f K p n/a n/a 1/n f Q K f Polany A F-P 1/n f B K p Q Q A P-P GLF b B (1/n g K p 4.6 n/a n/a b Q b Q Langmur b B Toth Q n/a n/a Q n/a n/a Lnar K p n T TABLE-4 SUMMARY OF SELECTED DIAGNOSTICS FOR HUMIC ACID ADSORPTION ON SWCNTS Paramtr Isothrm AICc R y R N M Lnarty Assssmnt BET Uncrtan Frundlch Uncrtan F-P Non-Lnar GLF Non-Lnar Langmur Non-Lnar Lnar Lnar L-P Non-Lnar Polany Non-Lnar P-P Non-Lnar Toth Non-Lnar Log log ( t (-t t/t ph: 4 ph: 7 ph: 1 ph: 4 ph: 7 ph: t t ph: 4 ph: 7 ph: 1 ph: 4 ph: 7 ph: 1 t t t t ph: 4 ph: 7 ph: 1 ph: 4 ph: 7 ph: Fg. 8. Ln t ph: 4 ph: 7 ph: 1 ph: 4 ph: 7 ph: Concluson t.5 Adsorpton kntcs of humc acd on SWCNTs and psudo-scondordr modl Rsults of ths study rvld that as ph dcrass from 1-4, adsorpton lvls of humc acd ncras and th hghst adsorpton lvl s obtand n ph of 4. Whn lvls of adsorbnt dos s fxd n.6 g pr ml of soluton, as contact tm ncrass from 15-1 mn, adsorpton lvl of humc acd ncrass; th hghst adsorpton lvl occurs n th frst 1 h. As lvl of adsorbnt dos ncrass, adsorpton lvl of humc acd also ncrass. Sngl-walld carbon nanotubs can compltly rmov dffrnt concntratons of humc acd n ph of 4 and n contact tm of 3 h. Rsults also showd that Sngl-walld carbon nanotubs ar consdrd a powrful adsorbnt n rmovng humc acds and can b ffctvly usd to rmov ths organc mattrs.

6 534 Moussav t al. Asan J. Chm. TABLE-5 EQUATION AND LINEAR FORM OF KINETICS Kntc Euaton Lnar form Rfrnc dt Psudo frst ordr k1( t dt Psudo scond ordr dt Elovch αxp( βt dt k1 log t.33 = ( = log( t d t = k( t dt t 1 1 = + t t k 1 β 1 β = = ln( αβ + lnt.5 t df + Intrapartcl dffuson = K t C 37 TABLE-6 THE PARAMETERS OBTAINED FROM VARIOUS KINETICS MODELS USING DIFFERENT HA CONCENTRATIONS Kntc Paramtr ph: 4 ph: 7 ph: 1 Psudo frst ordr Psudo scond ordr Elovch Intrapartcl dffuson Nomnclatur k 1 cal R k cal h R α β R K df C R R y : Corrlaton btwn masurd and smulatd data AICc : Corrctd Akak Informaton Crtron R N : Normal probablty corrlaton coffcnt M : Lnssn ndx A T : Tmkn constant (L/g B T : constant rlatd to hat of adsorpton (mg/l C : thcknss of th boundary layr (mg/g C : ntal concntraton (mg/l C : ulbrum concntraton n soluton (mg/l C s : saturaton concntraton n soluton (mmol/l C t : ulbrum concntraton n soluton at tm t (mg/l h : ntal sorpton rat (mg/g mn k 1 : Psudo frst-ordr rat constant (L/ mn k : Psudo scond-ordr rat constant (mg/g mn K B : BET constant K df : Intrapartcl dffuson rat constant (mg/g mn.5 K D-R : adsorpton nrgy (mol /kj K f : Frundlch sothrm constants (L/g K G : saturaton constant (mg/l K L : Langmur sothrm constants (L/mg n : adsorpton ntnsty N b : coopratv bndng constant : ulbrum adsorbnt concntraton on adsorbnt (mg/g cal : calculatd valus of (mg/g Q m : maxmum monolayr capacty (mg/g t : adsorbd concntraton at tm t (mg/g R : unvrsal gas constant, J/mol K R : corrlaton coffcnts : dmnsonal sparaton factor R L T α β ε : absolut tmpratur (K : ntal adsorpton rat (mg/g mn : dsorpton constant (g/mg : Polany potntal REFERENCES 1. H.C. Km, S.J. Park, C.G. L, Y.U. Han, J.A. Park and S.B. Km, Envron. Eng. Rs., 14, 41 (9.. Y. Zhan, J. Ln, Y. Qu, N. Gao and Z. Zhu, Front. Envron. Sc. Engn. Chna, 5, 65 ( M.N. Moura, M.J. Martín and F.J. Burgullo, J. Hazard. Matr., 149, 4 (7. 4. Y. Zhan, Z. Zhu, J. Ln, Y. Qu and J. Zhao, J. Envron. Sc. (Chna,, 137 (1. 5. C.E. Gokc, S. Gunysu, S. Aydn and S. Arayc, Opn Envron. Pollut. Toxcol. J., 1, 43 (9. 6. L. Lang, L. Luo and S.Z. Zhang, Collod. Surf. A, 384, 16 ( L. Zhao, F. Luo, J.M. Waskwcz, H. Mtomo, N. Nagasawa, T. Yag, M. Tamada and F. Yosh, Borsour. Tchnol., 99, 1911 (8. 8. S. Dng and R. Ba, J. Collod Intrf. Sc.,, 36 (4. 9. C. Lu and F. Su, Sp. Purf. Tchnol., 58, 113 (7. 1. AAM. Dafullah, B.S Grgs and H.M.H Gad, Collod. Surf. A, 35, 1 ( R.P. Lu, Y.L. Yang, G.B. L, W.J. H and H.D. Han, Front. Envron. Sc. Engn. Chna, 1, (7. 1. S. Vrysn and A. Mas, Appl. Clay Sc., 38, 37 ( Sh. Maghsoodloo, B. Norooz, A.K. Hagh and G.A. Soral, J. Hazard. Matr., 191, 3 ( T. Hartono, S.B. Wang, Q. Ma and Z.H. Zhu, J. Collod Intrf. Sc., 333, 114 ( C.P. Schulthss and C.P. Huang, Sol Sc. Soc. Am. J., 55, 34 ( M. Khrashh, M.A. Al-Ghout and C.A. Stanford, Chm. Eng. J., 161, 114 ( L.M. Ravlo-Pérz, J. Hrnándz-Borgs and M.Á. Rodríguz-Dlgado, J. Chromatogr. A, 111, 33 ( K.L. Strong, D.P. Andrson, K. Lafd and J.N. Kuhn, Carbon, 41, 1477 ( F. Yu, J. Ma and Y.Q. Wu, J. Hazard. Matr., 19, 137 (11.. C.-H. Wu, J. Hazard. Matr., 144, 93 (7. 1. K. Yang and B. Xng, Envron. Pollut., 157, 195 (9.. N.V. Prz-Agular, P.E. Daz-Flors and J.R. Rangl-Mndz, J. Collod Intrf. Sc., 364, 79 ( Z. Yu and J. Economy, J. Nanopartcl Rs., 7, 477 (5. 4. Q.H. Fan, D.D. Shao, J. Hu, C.L. Chn, W.S. Wu and X.K. Wang, Radochm. Acta, 97, 141 (9. 5. X.M. Rn, C.L. Chn, M. Nagats and X.K. Wang, Chm. Eng. J., 17, 395 ( J.H. Wang, X.J. Han, H.R. Ma, Y.F. J and L.J. B, Chm. Eng. J., 173, 171 ( L.H. A, C.Y. Zhang, F. Lao, Y. Wang, M. L, L.Y. Mng and J. Jang, J. Hazard. Matr., 198, 8 ( S. Brunaur, P.H. Emmtt and E. Tllr, J. Am. Chm. Soc.,, 39 ( H.M.F. Frundlch, J. Phys. Chm., 57, 385 ( W.J. Wbr Jr., P.M. McGnly and L.K. Katz, Envron. Sc. Tchnol., 6, 1955 ( F. Kano, I. Ab, H. Kamaya and I. Uda, Surf. Sc., 467, 131 (. 33. I. Langmur, J. Am. Chm. Soc., 38, 1 ( B. Xng, J.J. Pgnatllo and B. Gglott, Envron. Sc. Tchnol., 3, 43 ( G. Xa and W.P. Ball, Envron. Sc. Tchnol., 33, 6 ( J. Toth, Acta Chm. Acad. Hung., 69, 311 ( M. Ahmadan, N. Yosf, A. Toolab, N. Khanjan, S. Rahm and A. Fathzadh, Asan J. Chm., 4, 394 (1.