Removal of Nickel(II) from Aqueous Solutions by Adsorption with Modified ZSM- 5 Zeolites

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1 ISSN: ; CODEN ECJHAO E-Journal of Chmistry , 6(3), Rmoval of Nickl(II) from Aquous Solutions by Adsorption with Modifid ZSM- 5 Zolits P. PANNEERSELVAM *, V. SATHYA SELVA BALA, N. THINAKARAN, P. BASKARALINGAM, M. PALANICHAMY and S. SIVANESAN Environmntal Managmnt Laboratory, Dpartmnt of Chmical Enginring, A. C. Tchnology, Anna Univrsity, Chnnai , Tamilnadu, India. Dpartmnt of Chmistry, Anna Univrsity, Chnnai-25, India. sivansh@yahoo.com Rcivd 15 Novmbr 2008; Accptd 12 January 2009 Abstract: Th sorptiv rmoval of nickl ion from aquous solutions using modifid ZSM-5 zolits was invstigatd. Exprimnts wr carrid out as a function of solut concntration and diffrnt tmpraturs. Msoporous matrial of ZSM-5 zolit was modifid with phosphoric acid by wt mthod. Th modifid zolit was convrtd to Na + form using aquous NaHCO 3 solution. Th Na + form of modifid zolit, rprsntd as PNa 2- -ZSM-5 was charactrizd by XRD, BET, SEM and AAS tchniqus. It was thn tstd for ion xchang with aquous Ni(SO 4 ) solution. Th Ni 2+ contnt of th solution was analyzd by AAS. Phosphoric acid modifid PNa 2- -ZSM-5 zolit shows highr adsorption capacity than th parnt Na-Y zolit. Equilibrium modling data wr fit to linar Langmuir modl thn th Frundlich modl. Ths paramtr confirmd that sorption of Ni 2+ is fasibl spontanous and ndothrmic. Kywords: Nickl rmoval, Modifid zolits, Ion xchang, Isothrms. Introduction Svral nvironmntal and halth problms, associatd with th mtal contamination of th natural systms (soil and watr) ar arising from mining industris, smlting, brass, mtal coating, silvr rfinris, lctroplating and svral othr industrial activitis 1-2. Th main symptoms of nickl causs hadach, dizzinss, nausa and vomiting, chst pain, tightnss of th chst, dry cough and shortnss of brath, rapid rspiration, cyanosis and xtrm waknss 3. Among th mthods such as prcipitation, oxidation, ultrafiltration, rvrs osmosis and lctrodialysis, ion xchang on natural zolits sms to b mor attractiv mthod. Zolits hav bn intnsivly studid rcntly bcaus of thir applicability in rmoving trac quantitis of havy mtal ions from aquous solution by utilizing th ion xchang phnomnon 4-6.

2 730 P. PANNEERSELVAM t al. Zolits ar naturally occurring hydratd alumino silicat minrals. Thy blong to th class of minrals known as tctosilicats. Th structur of zolits consists of thr dimnsional framworks of SiO 4 and AlO 4 ttrahdra. Th aluminum ion is small nough to occupy th position in th cntr of th ttrahdron of four oxygn atom, whil th isomorphous rplacmnt of Si 4+ by Al 3+ producs a ngativ charg in th lattic 7. But hithrto only unmodifid zolits hav bn xamind for ion xchang capacity, in which on mol of sodium ion is xchangd for vry mol of Al 3+ prsnt in th framwork of zolit. Thr hav bn rports of modification of zolit with H 3 PO 4, for catalytic application. In th prsnt study, ZSM-5 zolit has bn modifid for rmoval of Ni 2+ ion from aquous solution. Each mol of phosphoric acid introducd into th zolit provids two mols of xchangabl protons, which can b rplacd by Na + ions using mild bas lik NaHCO 3 8. Th rsults obtaind from this study ar important for ion xchang and watr softning applications. Exprimntal HZSM-5 zolit was purchasd from Sud-Chmi India Ltd, Mumbai, India. Nickl Sulphat was obtaind from Qualigns Fin Chmicals Ltd., Mumbai, India. All othr chmicals usd wr of analytical ragnt grad, procurd from Rankm Fin Chmicals Ltd, Nw Dlhi, India. Prparation of modifid zolit About 4 g of HZSM-5 zolit in 40 ml of doubl distilld watr was mixd with g of phosphoric acid. Th mixtur was kpt undr vigorous stirring at 60 C for 3 h and thn vaporatd to drynss in an air ovn at 120 C. Phosphoric acid modifid zolit was contactd with 30 ml of aquous NaHCO 3 solution undr vigorous stirring at 60 C for 3 h to obtain th disodium form of an PNa 2- -ZSM-5 zolit. It was thn filtrd, washd with watr and drid in air ovn at 120 C ovrnight bfor us. Figur 1 illustrats th squnc of occurrncs in th abov tratmnt. Th Na- ZSM-5 zolit was prpard by adding NaHCO 3 solution dirctly with H ZSM-5 zolit. H 3PO C 3 h stirring Zolit-ZSM-5 Phosphat modifid 60 0 C 3 h stirring NaHCO 3 Saturatd Solution 2Na + + Watr + Ni 2+ Na - foam Figur 1. Raction schms illustrating modification of PNa 2- -ZSM-5 zolits.

3 Rmoval of Nickl(II) from Aquous Solutions by Adsorption 731 Ion- xchang quilibrium xprimnts Th ion xchang capacity of Ni 2+ ion with modifid Na-ZSM-5 and PNa 2- -ZSM-5 zolits wr studid using a batch mthod. Th batch xprimnts wr carrid out with 20 ml of 50 m mol Ni 2+ solution. About 65 mg of th adsorbnt was addd and th uptak of th zolit was dtrmind. Th ph of th solution was masurd using a ph mtr (Elico Modl LI-120, Hydrabad, India). Adjustmnts of ph wr mad with 0.1 M HCl and 0.1 M NaOH solutions. Th scrw cap bottl containing th adsorbat and adsorbnt wr placd in th thrmostatic orbital shakr (Nolab, Mumbai, India) and wr shakn at a constant spd of 200 rpm. Aftr quilibrium tim, th sampls wr cntrifugd and th filtrats wr analyzd. Th kintic studis wr carrid out in magntic stirrr 50 m mol Ni 2+ solutions. About 50 mg of th adsorbnt was addd. Th sampls wr withdrawn from th stirrr at a rgular tim intrvals and th sampls wr cntrifugd. Th absorbanc of suprnatant solution was masurd using Atomic absorption spctrophotomtr (SHIMADZU, AA-6300). Th uptak and th amount of Ni 2+ ion xchangd by th modifid zolits wr computd using th following quations. ( Co C) R moval fficincy (%) = X 100 (1) Co ( Co C) V q = (2) m Whr, q is th amount of xchangd Ni 2+ ions (m mol/g), C o and C ar th initial and quilibrium concntration of Ni 2+ ion in solution (m mol/l) rspctivly V is th solution volum and m is mass of th adsorbnt (g). Rsults and Discussion Charactrization of modifid zolit Th BET surfac aras of both modifid Na-ZSM-5 and PNa 2- -ZSM-5 zolits wr masurd using Smart Sorbs 92 Surfac ara analyzr whr N 2 gas was usd as adsorbat. Th surfac aras of modifid Na-ZSM-5 and PNa 2- -ZSM-5 zolits wr 385 and 422 m 2 /g rspctivly. Th XRD analysis of th modifid Na-ZSM-5 and PNa 2- -ZSM-5 zolits was masurd using D-Max / 111 VC Modl with nickl filtrd and Cu Kα radiation (λ= Ǻ). Th X-ray analysis rvals th absncs of structural dgradation during modification ar shown in Figur 2. Intnsity, a.u 2 Thta Figur 2. X-ray powdr diffraction pattrns of (a) Na-ZSM-5 (b) PNa 2 -ZSM-5 zolits.

4 732 P. PANNEERSELVAM t al. Scanning lctron microscop (SEM) imags wr takn to study th surfac morphology of zolit particls using a Jol Jsm-6360 scanning lctron microscop. Th SEM picturs of th parnt H- ZSM-5, Na-ZSM-5 and PNa 2- -ZSM-5 zolits ar shown in Figur 3 (a, b and c) rspctivly. Th modification of PNa 2- -ZSM-5 zolit might not hav rsultd any structural dgradation of th parnt zolit. a b c Figur 3. SEM imag of (a) H- ZSM-5, (b) Na-ZSM-5 (c) PNa 2- - ZSM-5 zolits. Effct of ph Th ffct of ph of th suspnding mdium on nickl rmoval was studid by prforming quilibrium sorption xprimnts at diffrnt ph valus. Th rsults ar illustratd in Figur 4. For th PNa 2 -ZSM-5 zolit th uptak fficincy gradually incrass as th ph incrass from 3 to 4 in Ni 2+. But abov ph 4 Ni 2+ uptak was obsrvd which could b attributd to prcipitation. Th Na-ZSM-5 zolit also xhibitd similar th bhavior. Hnc optimum ph rang for th rmoval of Ni 2+ was found to b 4. Th PNa 2 -ZSM-5 zolit showd highr uptak than th Na-ZSM-5 zolits as shown in Figur 4 as it contains mor xchangabl Na + ions than lattr.

5 Rmoval of Nickl(II) from Aquous Solutions by Adsorption Uptak in Ni (%) Uptak 2+, % in Ni Na-Zsm-5 PM-ZSM ph Figur 4. Effct of ph in Ni 2+ ions from aquous solutions onto ( ) Na-ZSM-5 and ( )PNa 2 - ZSM-5 zolits. Sorption isothrms Th sorption isothrms for th rmoval of Ni 2+ at diffrnt tmpraturs wr studid. It provids information on uptak capabilitis and rflcts th usual quilibrium procss bhavior. Th Langmuir isothrm could b writtn 9 as: C q = 1 + (3) Q b o C Q whr Q o is th monolayr adsorption capacity (m mol/g) and b is th constant rlatd to th fr nrgy of adsorption. Th logarithmic form of Frundlich quation is givn 10 as: 1 log q = log K f + logc (4) n whr K f is th rlativ adsorption capacity of th adsorbnt (m mol/g) and 1/n is th constant indicativ of th intnsity of th adsorption procss. Th Langmuir isothrm corrctly fittd than th Frundlich. Th Langmuir as shown in Figur 5. Th corrsponding Langmuir and Frundlich paramtrs along with thir corrlation cofficints ar givn in Tabl 1. Th Langmuir constants Q o and b ar incrass with incras of tmpratur showing that th sorption capacity and intnsity of th sorption ar nhancd at highr tmpraturs. Hnc, th activ surfac availabl for sorption has incrasd with incras of tmpratur. Rcntly thr hav bn many rports on th sorption of Ni 2+ with diffrnt adsorbnts and th rsults ar prsntd in Tabl 2. o

6 734 P. PANNEERSELVAM t al. C/q m mol/g C/q m mol/g C, m mol/g C, m mol/g Figur 5. Langmuir isothrm plots for th sorption of Ni 2+ ions from aquous solutions onto (a) Na-ZSM-5 (b) PNa 2 -ZSM-5 zolits. Tabl 1. Langmuir and Frundlich isothrm plots for th sorption of Ni 2+ ions from aquous solutions onto Na-ZSM-5 and PNa 2 -ZSM-5 zolits. Tmp (K) Langmuir isothrm Frundlich isothrm Q o, m mol/g b, L/m mol R 2 L 1/n K f, m mol/g R 2 F Na-Y PNa 2 -Y Tabl 2. Adsorption capacitis Q o (mg/g) for som zolit matrials Adsorbnt Ni(II), mg/g Kaolinit Ball Clay Kaolinit Na-Montmorillonit Exfoliatd Clay Clay tratd with HC l Natural zolit Clay tratd with NaC l Natural zolit Modifid Na-ZSM-5 zolit a H 3 PO 4 - modifid ZSM-5zolit a ( a Prsnt study)

7 Rmoval of Nickl(II) from Aquous Solutions by Adsorption 735 Kintic studis Psudo-first ordr kintic modl Th linar form of Lagrgrn s first ordr xprssion 15 is writtn as: k1 log( q qt ) = log q t (5) whr, k 1 (min -1 ) is th first ordr adsorption rat constant, q is th amount of mtal adsorbd at quilibrium and q t is th amount adsorbd at tim t. Th first ordr quation of Lagrgrn dos not fit wll with th whol rang of contact tim and is gnrally applicabl ovr th initial stag of th sorption procsss 16. Th first ordr rat constant is givn in Tabl 3. Psudo scond ordr kintic modl Th linar form of psudo- scond -ordr rat modl and 17 is xprssd as: t q t 1 1 = + t (6) 2 k q q 2 Whr, plotting t/q t against t for Ni 2+ rmoval at diffrnt tmpraturs is prsntd in Figur 6. Th rlationship is linar, and th corrlation btwn th paramtr also xplains that th procss of sorption of ach ion follows psudo scond ordr kintics. Th product k 2q 2 is th initial sorption rat rprsntd as h = k 2q 2 from Tabl 3. It can b shown that th valus of th initial sorption rat h and th rat constant k 2 incras with in incras in tmpratur. t/q min / g. mol t/q min / g. mol Tim, min Tim, min Figur 6. Psudo-scond-ordr kintics plots for th sorption of Ni 2+ ions from aquous solutions onto (a) Na-ZSM-5 (b) PNa 2 - ZSM-5 zolits. Th corrlation cofficint R 2 has an xtrmly high valu, and its calculatd quilibrium sorption capacity q is consistnt with th xprimntal data. Th rsults suggst that th psudo-scond ordr sorption mchanism is prdominant and that th ovr all rat constant of ach ion appars to b controlld by th chmisorption procss 17.

8 736 P. PANNEERSELVAM t al. Tabl 3. Th calculatd paramtrs of th psudo-first ordr and psudo-scond ordr kintic modls of Ni 2+ ions from Na-ZSM-5and PNa 2 -ZSM-5 zolits. Psudo-first ordr Psudo-scond ordr Tmp, K k 1, q, min -1 R 2 q, h, k 2, 1 m mol/g m mol /g m mol /g g/m mol min 2 R 2 Na-Y PNa 2 -Y Conclusions From this study it is concludd that phosphoric acid modifid ZSM-5 zolit can b a bttr adsorbnt than th parnt zolit. Th modification can also b xtndd to othr zolits for nhancd sorption proprtis. Th rmoval fficincy incrass with th incras in tmpratur and hnc sorption procss is ndothrmic in natur. Th adsorption isothrm data fit wll with Langmuir isothrm whil th kintic data wr rprsntd by psudoscond ordr kintic modl. This study forcasts that tratmnt of wastwatr, particularly havy mtal ion rmoval and softning of hardwatr, could b bttr carrid out with th modifid zolit. Th rsults of this study clary nvisag that such modifid zolits can vry wll b rcommndd for wastwatr tratmnt and control of nvironmntal pollution. Rfrncs 1. Howari F M, Abu-Rukah Y and Gooddll P C, Int J Environ Pollut., 2004, 22, Kadirvlu K, Thamarislvi K and Namasivayam C, Sp Purif Tchnol., 2001, 24, Parkr P, Encyclopdia of Environmntal Scincs, 2 nd Ed., McGraw Hill, Nw York, Shanablh A and Kharabshh A, J Hazard Matr., 1996, 45, Misalids P, Godlitsas A, Charistos V, Ioannou D and Charistos D, J Radioanal Nucl Chm., 1994, 183(1), Stylianou M A, Inglzakis V J, Moustakas K G, Dsalination, 2007, 215, Dyr A, Introduction to Zolit Molcular sivs, John Wily & Sons, Chichstr, Zhuang J, Ma D and Yang G, J Catalysis, 2004, 228, Langmuir I, J Am Chm Soc., 1918, 40, Frundlich H M F, Zitschrift fur physcikalisch Chmi (Lipzig), 1906, 57A, Chantawong V, Harvy N W and Bashkin V N, Watr Air Soil Pollut., 2003, 148, Kurniawan T A and Chan Y S, Sci Total Environ., 2006, 366, Abollino O, Acto M and Maiandrino M. Watr Rs., 2003, 37, Hawash S, Farash J Y and El-Gundi M S, Adv Sci Tchnol.,1994, 9, McKay G and Ho Y S, Watr Rs., 1999, 33, McKay G and Ho Y S, Procss Biochm., 1999, 34, Ho Y S, J Colloid Intrfac Sci., 2003, 262,

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