Sorption Isotherm Model of Zinc (II) onto Thermally Treated Rice Husk

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1 ORIENTAL JOURNAL OF CHEMISTRY An Intrnational Opn Fr Accss, Pr Rviwd Rsarch Journal ISSN: X CODEN: OJCHEG 206, Vol. 32, No. (5): Pg Sorption Isothrm Modl of Zinc (II) onto Thrmally Tratd Ric Husk AHMAD FARHAN AHMAD TARMIZI, KEAT KHIM ONG 2 *, WAN MD ZIN WAN YUNUS, ANWAR FITRIANTO 3, MOHD LIP JABIT 4, ABDUL GHAPOR HUSSIN and CHIN CHUANG TEOH 5 Dpartmnt of Dfnc Scinc, Faculty of Dfnc Scinc and Tchnology, Univrsiti Prtahanan Nasional Malaysia, Km Sungai Bsi, Kuala Lumpur, Malaysia. 2 Dpartmnt of Chmistry and Biology,Cntr for Dfnc Foundation Studis, Univrsiti Prtahanan Nasional Malaysia, Km Sungai Bsi, Kuala Lumpur, Malaysia. 3 Dpartmnt of Mathmatics, Faculty of Scinc, Univrsiti Putra Malaysia, Malaysia. 4 Tchnical Srvics Cntr, Malaysian Agricultural Rsarch and Dvlopmnt Institut (MARDI) Hadquartr, G. P.O. Box 230, Kuala Lumpur, Malaysia. 5 Enginring Rsarch Cntr, Malaysian Agricultural Rsarch and Dvlopmnt Institut, (MARDI) Hadquartr, G. P.O. Box 230, Kuala Lumpur, Malaysia. *Corrsponding author ongkhim@upnm.du.my (Rcivd: Jun 0, 206; Accptd: Augsut 04, 206) ABSTRACT Various modifications wr usd to convrt wast matrials into havy mtal sorbnts. In this study, simpl thrmal tratmnt was applid on ric husk and its sorption potntial to rmov Zn (II) ions from aquous solution was invstigatd. Equilibrium sorption data wr valuatd with two commonly usd isothrms i.. Langmuir and Frundlich isothrms. Cofficint of dtrmination (R 2 ) of th modls wr usd to dtrmin th bst fittd isothrm. Th corrlation cofficints wr and for Langmuir and Frundlich isothrms, rspctivly, showing that th sorption was bttr dscribd by Langmuir isothrm. In addition, th sorption procss is found to b favourabl as indicatd by th sparation factor (R L ) valu btwn 0 and. Th potntial of thrmally tratd ric husk as a sorbnt for th rmoval of Zn (II) ions from aquous solution is rcognisd. Kywords: Isothrm Modl, Thrmally Tratd Ric Husk, Zn (II) Ions. INTRODUCTION Havy mtals ar toxic and hazardous pollutants in watr du to thir non-biodgradabl and prsistnt bhaviours in th nvironmnt. Zinc is on of th havy mtals dischargd from industrial fflunts. Its harmful halth ffcts including mtalfum fvr, nausa, diarrhoa, dprssion, lthargy,

2 2798 TARMIZI t al., Orint. J. Chm., Vol. 32(5), (206) sizurs, and ataxia 2. Consquntly, th maximum accptabl concntration of Zn (II) in drinking watr prmittd by World Halth Organization (WHO) is 0.05 mg/l 3. Diffrnt chmical and physical mthods such as prcipitations, ion xchang, filtration, and solvnt xtraction hav bn applid to rmov havy mtals from wastwatr. Howvr, ths mthods hav som drawbacks for xampls high oprational cost, low rmoval fficincy at low concntration, and producing toxic sludg that nds furthr tratmnt 4. Nvrthlss, adsorption is an altrnativ approach to trat toxic havy mtals sinc this mthod is widly usd as it is cost ffctiv procss 5. Various wast matrials hav bn usd as adsorbnts for xampls rapsd wast 6, coff husks 7, corn cob 8, alum sludg wast 9, and ric husk 0. Undrstand adsorption mchanism by adsorption isothrm study is important as it can shows th distribution of adsorbat molculs btwn th liquid phas onto th solid phas. Langmuir and Frundlich modls ar th common isothrm modls usd to corrlat th adsorption quilibrium of havy mtals onto adsorbnts 2. Paduraru t al. 6 and Olivira t al. 7 hav shown that quilibrium data fittd wll with Langmuir isothrm modl compard to Frundlich in thir invstigations on adsorption of Zn (II) ions onto rapsd and coff husks, rspctivly. According to Abdolali t al., pr-tratmnt of adsorbnts can improv physical and chmical proprtis of adsorbnts, which can nhanc th adsorption capacity and prvnt organic laching. Hnc, in this work, a simpl tratmnt was applid on ric husk to produc thrmally tratd ric husk for sorption of Zn (II) ions from aquous solution. Equilibrium isothrm of th sorption was invstigatd. MATERIALS AND METHODS Chmicals Sodium hydroxid pllts,.0 M hydrochloric acid and 000 mg/l of zinc nitrat standard solutions wr of analytical grad and obtaind from Mrck Company (Grmany). Ultrapur watr (rsistivity of 8.2 M&!.cm) usd for rinsing glasswar, dilutions and prparation of solutions was obtaind from a Milli-Q watr purification systm (Millipor, Grmany). Prparation of sorbnt Ric husk collctd from a local ric mill was groundd and washd with ultrapur watr svral tims to liminat impuritis and to obtain constant ph bfor drid in an ovn at 05 C for 24 h. Th drid ric husk was sivd to obtain particls siz btwn 300 to 600 µm and thn hatd in a furnac at 800 C for two hours. Th thrmally tratd ric husk was thn put in a dsiccator for cooling bfor kpt in a containr for th adsorption xprimnts. Prparation of solutions Various concntrations of Zn (II) working solutions (30-80 mg/l) usd for sorption xprimnts wr prpard by dilutions of 000 mg/l of Zn(NO 3 ) 2 standard solution with th ultrapur watr. In ordr to adjust th ph of Zn (II) working solutions, 0. M of HCl solution was prpard by diluting.0 M of HCl solution, whras.0 M NaOH solution was prpard by dissolving an accurat amount of sodium hydroxid pllt with th ultrapur watr. Sorption study On hundrd ml of 30 mg/l of Zn (II) solution which was adjustd to ph 6 with.0 M NaOH and /or 0. M HCl solutions, was mixd with 2 g of µm particl siz of thrmally tratd ric husk. Th mixtur was agitatd at 50 rpm for 80 minuts at 30 o C. Aftr th contact tim, th mixtur was filtrd using a 0.45 µm cllulos nitrat mmbran filtr. Th contnt of Zn (II) ions in th filtrat was analyzd using an inductivly coupld plasma optical mission spctromtry (ICP-OES) (Prkin Elmr, OPTIMA 5300 DV). Th sorption xprimnts wr conductd in duplicats and rpatd using 60, 90, 20, 50 and 80 mg/l of Zn (II) working solutions. Th sorption capacity, q t, was dtrmind using quation ():...() whr C o and C wr initial and final concntrations (mg/l) of Zn (II) ions, rspctivly, m is th mass of sorbnt (g) and V is th volum of solution (L).

3 TARMIZI t al., Orint. J. Chm., Vol. 32(5), (206) 2799 RESULTS AND DISCUSSION Adsorption isothrm modls ar applid to dtrmin th intraction btwn adsorbnt and adsorbat spcially Langmuir and Frundlich isothrm modls 3. Hnc, in this study, th quilibrium data wr valuatd with ths isothrm modls. Th cofficint of dtrmination (R 2 ) of th modls wr usd to dtrmin th bst fittd isothrm modl. Langmuir isothrm modl Langmuir adsorption isothrm is widly usd to dscrib th adsorption of organic and inorganic pollutants, such as dys and havy mtals from aquous solutions. It suggsts that th adsorption onto th adsorbnt surfac is homognous, whr th adsorption of solut from aquous solution onto th adsorbnt surfac occurs as monolayr adsorption on th homognous numbr of xchanging sits 4. Langmuir adsorption isothrm is xprssd as blow: C q = q b + C q max max...(2) whr q is th amount of mtals adsorbd on th sorbnt (mg/g) at quilibrium, C is th concntration of mtal solution at quilibrium, q max Fig. : Langmuir plot for sorption of Zn (II) ions Fig. 2: Frundlich plot for sorption of Zn (II)ions

4 2800 TARMIZI t al., Orint. J. Chm., Vol. 32(5), (206) Tabl : Langmuir and Frundlich sorption isothrm constants for Zn (II) ions Langmuir constants Frundlich constants q max (mg/g) K f ((mg/g)/(mg/l) /n ) 3.28 b (L/mg) n R R is th maximum sorption capacity dscribing a complt monolayr sorption (mg/g) and b is sorption quilibrium constant (L/mg) that is rlatd to th fr nrgy of sorption. Th valus of q max and b wr dtrmind from th linar plot of C /q vrsus C. Figur shows th Langmuir plot for sorption of Zn (II). Th data obtaind with th cofficints of dtrmination (R 2 ) was prsntd in Tabl. Equilibrium paramtr, R L is a dimnsionlss constant sparation factor to xprss th ssntial faturs and charactristics of Langmuir isothrm 5,6. R L can b dfind as:...(3) whr b is sorption quilibrium constant (L/mg) that is rlatd to th fr nrgy of sorption and C o is initial concntration of Zn (II) ions (mg/l). Th valu of R L shows th sorption ithr unfavourabl if R L >, linar if R L =, favourabl if 0 < R L <, or irrvrsibl if R L = 0. Th R L valus for th sorption of Zn (II) ions onto thrmal tratd ric husk using th lowst initial concntration (30 mg/l) and th highst initial concntration (80 mg/l) wr and , rspctivly. Th rsults provd that th sorption of Zn (II) ions using thrmally tratd ric husk is a favourabl procss. Frundlich isothrm modl Frundlich isothrm modl assumd that th adsorption procss occurs from th intraction of th pollutant molculs on th htrognous surfacs. Whn th occupid binding sits incrasd, th nrgy of adsorption dclind logarithmically 4. Frundlich isothrm modl usd to valuat th xprimntal was xprssd by th following quation 7. log q = log K + logc f n...(4) whr K f is th Frundlich isothrm constant (mg/g) rlatd to th bonding nrgy. K f and n ar constants and dtrmind from th log q vrsus log C plot. Th constants K f and n wr calculatd using Frundlich plot as shown in Figur 2. Th valus for Frundlich constants and cofficint of dtrmination (R 2 ) for th sorption procss ar prsntd in Tabl. Th valu of n btwn and 0 (/n lss than ) indicats favourabl adsorption 6. From Tabl, th valu of n is indicating that th sorption of Zn (II) is favourabl. From Tabl, th rsults showd that th sorption of Zn (II) onto thrmally tratd ric husk was bttr fittd to Langmuir isothrm modl (R 2 = ) compard to Frundlich isothrm modl (R 2 = ). Ths rsults provd that th sorption is monolayr with an qual activation nrgy and no intraction btwn sorbats on th adjacnt activ sits. Study by Elham t al. 3 found that adsorption bhaviour of Zn (II) onto ric husk was wll dscribd by Langmuir isothrm modl, whil sorption of Zn (II) by chmically prpard ric husk also follow Langmuir isothrm modl 0. CONCLUSION In this work, mchanisms of Zn (II) ions sorption wr proposd basd on quilibrium data obtaind. Th sorption was bttr dscribd by Langmuir isothrm compard to Frundlich isothrm which suggsts that th sorption of Zn (II) ions onto th sorbnt surfac is on monolayr. Th sorption procss was favourabl as indicatd by th sparation factor (R L ) valu. Thrmally tratd ric

5 TARMIZI t al., Orint. J. Chm., Vol. 32(5), (206) 280 husk can b a candidat of cost ffctiv sorbnt to rmov Zn (II) ions from wastwatr. This approach also might hlp to solv th problm of agricultural wast managmnt. ACKNOWLEDGMENT Th authors ar gratful to Univrsiti Prtahanan Nasional Malaysia for th support to conduct this rsarch work. REFERENCES. Bilal, M.; Shah, J. A.; Ashfaq, T.; Gardazi, S. M. H.; Tahir, A. A.; Prvz, A.; Haroon, H.; Mahmood, Q.; Journal of Hazardous Matrials. 203, 263, Malamis, S.; Katsou, E.; Journal of Hazardous Matrials. 203, , Mali, A.; Pandit V.; Majumdr, D. R.; Intrnational Journal of Tchnical Rsarch and Applications. 204, 2, Matouq, M.; Jildh, N.; Qtaishat, M.; Hindiyh M.; Syouf, M. Q. A.; Journal of Environmntal Chmical Enginring. 205, 3, Rgina, M. Y.; Saraswathy, S.; Kamal, B.; Karthik, V.; Muthukumaran, K.; Journal of Chmical and Pharmacutical Scincs. 205, 8, Paduraru, C.; Tofan, L.; Todosiu, C.; Bunia, I.; Tudorachi, N.; Toma, O.; Procss Safty and Environmntal Protction. 205, 94, Olivira, W. E.; Franca, A. S.; Olivira, L. S.; Rocha, S. D.; Journal of Hazardous Matrials. 2008, 52, Buasri, A.; Chaiyut, N.; Tapang, K.; Jaronsin, S.; Panphrom, S.; APCBEE Procdia. 202, 3, Ong, K. K.; Md Nor, M. A; Mohamad, S; Ahmad Nasaruddin, N; Jamari, N. A.; Wan Yunus, W. M. Z.; AIP Conf. Proc. 205, 660, El-Shafy, E. I.; Journal of Hazardous Matrials. 200, 75, Abdolali, A.; Ngo, H. H.; Guo, W.; Zhou, J. L.; Du, B.; Wi, Q.; Wang, X. C.; Nguyn, P. D.; Biorsourc Tchnology. 205, 93, Sadk, S. A.; Ngm, N. A.; Hfni, H. H. H.; Wahab, M. M. A.; Intrnational Journal of Biological Macromolculs. 205, 8, Elham, A.; Hossin, T.; Mahnoosh, H.; J. Appl. Sci. Environ. Manag. 200, 4, Safa, Y.; Biosorption of Dirct Dys from Aquous Solution Using Ric (oryza sativa) Husk, Vol. Doctor of Philosophy Univrsity of Agricultur, Faisalabad, Dada, A. O.; Ojdiran, J. O.; Olalkan, A. P.; Advancs in Physical Chmistry. 203, 203, Naiya, T. K.; Bhattacharya, A. K.; Mandal, S.; Das, S. K.; Journal of Hazardous Matrials. 2009, 63, Frundlich, H.; Phys. Chm. Soc. 906, 40,