Adsorption Study of Cobalt on Treated Granular Activated Carbon

Transcription

1 ISSN: ; CODEN ECJHAO E- Chmistry , 9(1), Adsorption Study of Cobalt on Tratd Granular Activatd Carbon Y.V.HETE *, S.B.GHOLASE and R.U.KHOPE Dpartmnt of Chmistry, Laxminarayan Institut of Tchnology Nagpur Univrsity, Nagpur , India Dpartmnt of Chmistry, Shri Shivaji Scinc Collg Congrss Nagar, Nagpur , India Rcivd 19 Jun 2011; Accptd 13 August 2011 Abstract: This study is carrid out for th rmoval of cobalt from aquous solution using granular activatd carbon in combination with p-nitro bnzoic acid at tmpratur 25±1 0 C. Th adsorption isothrm of cobalt on granular activatd carbon has bn dtrmind and th data fittd rasonably wll to th Langmuir and Frundlich isothrm for activatd carbon. Kywords: Adsorption, Cobalt, Granular activatd carbon, p-nitro bnzoic acid Introduction Th rapid industrialization has causd srious rprcussions such as th pollution of natural rsourcs lik groundwatr. Sinc groundwatr movs through rocks and subsurfac soil, it has a lot of opportunity to dissolv substancs as it movs. As a rsult of this pollution of watr bodis bcoms a major nvironmntal problm of th modrn world. Thrfor, in last dcads, th prsnc of mtals in aquatic cosystms has rcivd widsprad attntion du to thir potntial human halth risks and harmful ffct to living organisms. As cobalt is widly disprsd in th nvironmnt humans may b xposd to it by brathing air, drinking watr and ating food that contains cobalt. Skin contact with soil or watr that contains cobalt may also nhanc xposur. It is not oftn frly availabl in th nvironmnt, but whn cobalt particls ar not bound to soil or sdimnt particls th uptak by plants and animals is highr and accumulation in plants and animals may occur. It is an animal carcinogn producing cancr at various sits. Exposur to cobalt is xtrmly irritating to th skin both on contact and by provoking an allrgic raction which snsitizs th skin to furthr contact. It is also irritating to th ys and mucous mmbran, causing svr discomfort in th nos, oftn lading to prforation of th nasal sptum. High concntrations

2 336 Y. V. HETE t al. of cobalt may damag human halth. Whn w brath in too high concntrations of cobalt through air w xprinc lung ffcts, such as asthma and pnumonia. Th thrshold limit valu for cobalt fum and dust xposurs is 0.1 mg/m 3 in th U.S Tratabl amount of cobalt wasts ar growing nd in th industrial sctor to try and find ways to rcovr a mtal through solutions using granular activatd carbon In this work, cobalt was scavngd using F 200 D and F 300 D containing adsorbd ligands. For this purpos p-nitro bnzoic acid has bn chosn as a organic ligand. Exprimntal Bituminous coal basd Fitrasorb 200D,300D granular activatd carbons wr first subjctd to siz fractionation. Both carbons wr sivd using a siv shakr whrin th siz corrsponding to msh siz 16x25 (M/s Jayant Tst Sivs, Mumbai) wr collctd for us. Th sivd GAC was first stirrd in boiling distilld watr carfully without lading to any attrition svral tims until a clar lachat was obtaind and thn drid in an ovn at a tmpratur of 110 O C for 24 h and latr coold in a dsiccators containing anhydrous CaCl 2 to nsur complt rmoval of moistur from th carbon. A stock solution of cobalt ions was obtaind by using a solution of cobalt sulphat (E. Mrck). Br s law calibration curv was stablishd for Co 2+ spctophotomtrically 13 to calculat concntration of xprimntal solutions and rgrssion analysis of th data showd that th rgrssion cofficint was around All th chmicals usd wr of AR grad. A sampl of p-nitro bnzoic acid (E.Mrck) was rcrystallizd by standard mthod. Th xprimntal mlting point of p-nitro bnzoic acid (241 o C) was chckd from th litratur valu (242 o C) 14. Th sampl was also charactrizd through dtrmination of molcular wight by th tchniqu of ph titration against standard alkali. For dtrmining th adsorption isothrm of cobalt ion on diffrnt grads of carbon containing adsorbd ligand such as p-nitro bnzoic acid, it was first ssntial to fix th amount of ligand on th GAC. This procss of fixing of ligand on GAC was dnotd as loading of GAC. For this purpos 0.5 g of th GAC was takn in clan shaking bottls and 200 ml of th ligand solution of a spcifid concntration was shakn for about six hours on a mchanical shakr (Eltk Motor, Typ M 56.Elktrocrats India, PVT LTD Mumbai.). Th solution was thn filtrd off and th carbon was washd thoroughly with distilld watr. This carbon was thn transfrrd to a on litr round bottom flask and thn 200 ml of cobalt solution at a ph = 5 wr addd to it. Th contnts wr stirrd for 6 hours at 25±1 0 C. Th initial and final concntrations of th cobalt ion in mg/l was thn dtrmind spctrophotomtrically (Systronics). Th concntrations of Co 2+ ion wr calculatd using following quation obtaind from calibration curv. A C = (1) Whr, A = Absorbanc and C = Concntration of cobalt. Th xprimnts wr rpatd to nsur rproducibl rsults. Rsults and Discussion Equilibrium adsorption isothrms for q vs C was plottd for diffrnt grads of granular activatd carbon and ar shown in Figur 1 and 2.

3 Adsorption Study of Cobalt on Tratd Granular Activatd Carbon 337 Q, mg/mmol C, mg/l Figur 1. Adsorption isothrm systm: F 200 D - p-nitro bnzoic acid-co 2+ Figur 2. Adsorption isothrm systm: F 300 D - p-nitro bnzoic acid-co 2+ Th amount of cobalt on th ligand adsorbd on th GAC was dtrmind using th quation: V q = (Co - C ) x (2) W Whr, q = Concntration of cobalt on th ligand loadd GAC in mg/millimols of ligand, C o = Initial concntration cobalt in solution in mg/l, C = Final concntration of cobalt in solution in mg/l, V = Volum of solution in litrs, W= Millimols of th ligand actually prsnt on GAC (0.5 g). It is obsrvd from th rsult in Tabl 1 that cobalt adsorption follows th trnd F 300 D > F 200 D Data of quilibrium isothrms was tstd for adhrnc to both Langmuir and Frundlich modls. As pr Langmuir thory, th saturatd valu is that byond which no furthr sorption can tak plac. Th saturatd monolayr can thn b rprsntd by Th linarisd form of Langmuir isothrm is 0 C q = Q bx (3) 1+ bc 1 q = x + (4) 0 0 Q b C Q Whr Q o and b ar Langmuir constants. Frundlich quation is on th othr hand rprsntd by q = k (5) 1/n C Th abov quation may b linarisd as log q 1 = log k + β log (6) n C C, mg/l Whr k and 1/n ar Frundlich constants. Figur 3 to 6 illustrats th plot of Langmuir and Frundlich isothrms for F 200 D and F 300 D. Th plots of 1/q vs 1/C wr found to b linar indicating th applicability of Langmuir modl. Th paramtrs Q o and b ar Langmuir constants rlating to th sorption capacity and adsorption nrgy rspctivly. Th intrcpt and slop of th linr plots of log q vs log C and of 1/q vs 1/C undr givn st of xprimntal conditions provid valus of k, 1/n, Q o and b rspctivly. Th corrsponding Frundlich and Langmuir constants obtaind ar listd in Tabl 1. Th valus of k and Q o for F 300 D carbon- p-nitro bnzoic acid-co 2+ systm wr gratr than thos for F 200 D carbon- p-nitro bnzoic acid-co 2+ systm, indicating th supriority of th formr for this sorption procss.

4 338 Y. V. HETE t al. 1/q 1/q 1/C 1/C Figur 3. Langmuir adsorption isothrm Systm: F 200 D - p-nitro bnzoic acid- Co 2+ Figur 4. Langmuir adsorption isothrm Systm: F 300 D - p-nitro bnzoic acid- Co 2+ log q log q log C log C Figur 5. Frundlich adsorption isothrm Systm: F 200 D - p-nitro bnzoic acid-co 2 S.No 1 2 Systm Tabl 1. Isothrm constants Langmuir Q o Figur 6. Frundlich adsorption isothrm Systm: F 300 D - p-nitro bnzoic acid-co 2+ Constants b Frundlich k Constants 1/n q max mg/m.mol F 200 D- p-nitro bnzoic acid-co F 300 D - p-nitro bnzoic acid-co Plot of log q vs log C was fairly linar showing validity of Frundlich quation also ovr a rang of concntrations mployd for th ligands as shown in Tabl 2 all xprimntal solutions wr analyzd using th quation found by rgrssion analysis of absorbanc concntration data. In prsnt work ordr of adsorption followd th trnd, GAC- F 300 D > GAC - F 200 D. Tabl 2. Rgrssion analysis data S.No. Systm Typ of adsorption Equation Rg Coff 1 F 200 D - p-nitro Langmuir adsorption y = x bnzoic acid-co 2+ isothrm F 300 D - p-nitro Langmuir adsorption y = x bnzoic acid-co 2+ isothrm F 200 D - p-nitro bnzoic acid-co 2+ Frundlich adsorption isothrm y = x F 300 D - p-nitro bnzoic acid-co 2+ Frundlich adsorption isothrm y = x

5 Adsorption Study of Cobalt on Tratd Granular Activatd Carbon 339 Conclusion From th abov studis, it is clar indicatd that granular activatd carbon could function vry ffctivly in scavnging mtal ions from aquous solution. Th adsorption isothrms of th cobalt on diffrnt grads of carbon loadd with p-nitro bnzoic acid clarly shows that F 300 D carbon adsorbs cobalt to a gratr xtnt as compard to F 200 D carbon. Adsorption was found to b in good agrmnt with Langmuir isothrm which indicats mono layr adsorption. Howvr ths mthods can b optimizd furthr by using oxidizing agnts, study of which is in progrss. Rfrncs 1. Mukharj A.G, Envirinmntal Pollution and Halth Hazards; Causs and Control, in: Galgotia S, (Ed), Nw Dlhi, Dara S S, A txt book of nvironmntal chmistry and pollution control, in: Chand S, Company Ltd (Ed), Nw Dlhi, 2002, Paajann A, Lhto J, Sataapakka T and Mornau J P, Sp Sci Tchnol., 1997, 32, Ntzr A and Hughs D E, J Watr Rs., 1984, 18(8), Corupioglu M O and Huang C P, J Watr Rs., 1987, 21(9), Rivra, Utrilla J and Garcia M A F, Carbon, 1987, 25, Yupng Guo, Jurui Qi, Shaofng Yang, Kaifng Yu, Zichn Wang and Hongding X U, 2003, 78(1), Khop R U, Halmar S S and Natarajan G S, Asian J Chm., 2004, 16(2), Abiola Olusgun K and Otaigh J O E, Int J Elctrochm Sci., 2008, 3, Islam M and Patl R K, J Hazardous Matr., 2007, 143, Daifullah A A M, Yakout S M and Elrfy S A, J Hazardous Matr., 2007, 62, Mna A K, Rajagopal C, Kiran C R and Mishra G K, J Sci Ind Rs., 2010, 69, Vogl A I, Quantitativ inorganic analysis, 4 th Ed., Longman Group Ltd., England, 1978, Rodd E H, Chmistry of Carbon Compounds, Elsvir Publishing Company, N.Y.3B, 1956, 769.

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