Adsorption of Ni (II) from Wastewater using Low Cost Activated Carbon Prepared from Prosopis Juliflora- A Kinetics and Equilibrium Studies

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1 Chmical Scinc Transactions DOI:.7598/cst , 3(3), RESEARCH ARTICLE Adsorption of Ni (II) from Wastwatr using Low Cost Activatd Carbon Prpard from Prosopis Juliflora- A Kintics and Equilibrium Studis M. THILAGAVATHI, S. ARIVOLI 2* andv. VIJAYAKUMARAN 3 Dpartmnt of Chmistry, Pattukkottai Polytchnic Collg, Pattukkottai-64 6, India 2 Dpartmnt of Chmistry, Thiru Vi Ka Govrnmnt Arts Collg, Thiruvarur-6 3, India 3 Anna Univrsity, Univrsity Collg of Enginring, Pattukkottai -64 7, India vijayakumaran_66@yahoo.com Rcivd 6 Fbruary 24 / Accptd 2 Fbruary 24 Abstract: Th optimum paramtrs affcting th adsorption of Ni(II) using Prosopis Juliflora bark carbon (PJBC) wr dtrmind. Th adsorption of Ni(II) was strongly dpndnt on ph, tmpratur and initial adsorbat concntration. Th quilibrium adsorption data follows Langmuir and Frundlich isothrms. Th optimum ph for Ni(II) ions rmoval was found out to b 5.5. Th quilibrium data shows th xothrmic natur of adsorption. Kintic studis shows psudo scond ordr and intra-particl diffusion quations succssfully dscrib th adsorption procss. Kywords: Adsorption, Kintics, Nickl, PJBC, Thrmodynamic Introduction Du to toxic havy mtals contamination watr pollution has bn a major problms in nvironmnt, which causs objctionabl ffcts, impairing th wlfar of th nvironmnt, rducing th quality of lif and may vntually caus dath. Such a substanc has to b prsnt in th nvironmnt byond a st or tolranc limit, which could b ithr a dsirabl or accptabl limit. Th industrial and domstic wastwatr is rsponsibl for causing svr damags to th nvironmnt and advrsly affcting th halth of th popl and aquatic lif. Mtals can b distinguishd from othr toxic pollutants, sinc thy ar non-biodgradabl and can accumulat in living organism. A varity of industris ar rsponsibl for th rlas of havy mtals into th nvironmnt through its wastwatr. Ths includ iron and stl production, lctroplating, th non-frrous mtal industry, mining and minral procssing, paint and pigmnt industris, lathr procssing, dying, txtil and photographic industris. Th main tchniqus usd to rduc th havy mtal ion concntration in th industrial fflunts such as lim prcipitation, ion xchang, adsorption using activatd carbon 2,

2 28 Chm Sci Trans., 24, 3(3), mmbran filtration and lctrolytic mthods. Evry mthods hav crtain limitation, sinc thos includs high capital and oprational costs and also th gnration of scondary wast during th tratmnt procss. Adsorption has advantags ovr othr mthods bcaus it is simpl, low cost and hazardous fr to nvironmnt 3. Activatd carbon was found to b highly ffctiv adsorbnt for th rmoval of havy mtal ion from th concntratd and dilut mtal baring fflunts 4. But th procss was not usd by small and mdium scal industris for th tratmnt of thir mtal baring fflunts, bcaus of its high manufacturing cost. For this rason, th us of low cost matrials as adsorbnt for th rmoval of mtal ion from th wastwatr has bn invstigatd. Howvr, fforts hav bn contributd to dvlop nw adsorbnt and improving th xisting adsorbnts to hav an altrnativ to activatd carbon. Th locally availabl Prosopis juliflora bark carbon is an altrnativ to commrcial activatd carbon. Exprimntal Prparation of Prosopis Juliflora Bark Carbon (PJBC) adsorbnt Prosopis Juliflora bark (PJB) was collctd from local markt. Th collctd PJB matrials wr finly powdrd with grinding machin. Thn th powdr was tratd with con. sulphuric acid for 2 hours thn filtrd and thn washd with watr. Th black product was kpt in a furnac for about 24 hours and th tmpratur was maintaind at 8 o C. Th rsulting powdr was usd for adsorption xprimnt. All othr chmicals usd for th xprimnts wr highly pur. Nickl(II) ions solution NiSO 4. 6H 2 O purchasd from Mrk company. Th stock solution was prpard by dissolving 4.78 g of nickl sulphat in ml of distilld watr. Batch mthod Batch mthod 4 was usd for adsorption and kintic studis. Th tst solutions such as adsorbnt, adsorbat wr takn in 25 ml conical flasks. Th solution ph was adjustd using a.n HCl or.n NaOH solution. Th solution tmpratur was monitord using thrmostatic watr bath with constant stirring. Th rsidual concntration of mtal ions wr masurd using spctrophotomtr at 455 nm. Th quilibrium paramtrs wr usd for th adsorption and kintic studis. Th amount of adsorption q t (mg/g) at tim t, amount of adsorption at quilibrium, q (mg/g) and prcntag rmoval wr calculatd by (C -C )V q O t () t W (C -C )V q O (2) W % Rmoval Co -Ct X (3) Co Whr C o, C t (mg/l) and C (mg/l) ar th liquid phas concntrations of nickl ions at initial, at tim and quilibrium rspctivly.v (L) is th volum of th solution. W (g) is th mass of dry adsorbnt usd. Rsults and Discussion Effct of contact tim Th ffct of contact tim for th rmoval of th mtal ions using PJBC adsorbnt was dtrmind by kping th concntration mtal ions, adsorbnt dos, tmpratur and ph

3 Chm Sci Trans., 24, 3(3), wr constant. Th ffct of contact tim using 25 mg/l of mtal ions, ph is 6 and 25 mg/5 ml of adsorbnt at 3 o C shown in Figur. This indicats 6 minuts is nough to rach mor than 8% rmoval of Nickl ions. 9 8 % Rmoval of Ni(II) ions Contact tim in minuts Figur. Effct of contact tim for th adsorption of Ni(II) ions [Ni(II)]=25 mg/l: Tmp=3 o C; Adsorbnt dos=25 mg/5 ml Effct of adsorbnt dos Th various doss consisting of th PJBC adsorbnt wr mixd with th fixd initial concntration of mtal ions solution without changing th ph and tmpratur. Th mixturs wr agitatd in a thrmostatic watr bath with mchanical shakr. Th prcntag rmoval of mtal ions for diffrnt doss of adsorbnt wr dtrmind. Th ffct of adsorbnt dos was studid using 25 mg/l of mtal ions, ph is 6, 3 o C and adsorbnt dos in th rang of 5 mg to 25 mg/5 ml as shown Figur 2. This indicats 25 mg to 5 mg/5 ml of adsorbnt dos wr sufficint for this xprimntal concntration % Rmoval of Ni(II) ions Absorbnt dos in mg Figur 2. Effct of adsorbnt dos for th rmoval of Ni(II) ions [Ni(II)]=25 mg/l; ph=6.5; Tmp=3 o C; Contact tim=6 minut Effct of solution ph Th mchanism of adsorption at th PJBC surfac rflcts th natur of physicochmical intraction of th mtal ions in th solution and th activ sits of th PJBC. Th ph of th solution was varid from 2 to during study. Th ffct of solution ph using 25 mg/l of

4 2 Chm Sci Trans., 24, 3(3), mtal ions and 25 mg/5 ml of adsorbnt at 3 o C shown in Figur.3. Th uptak capacity of PJBC is found maximum at ph of 5.5. It can b sn from th figur that th rmoval of mtal ions is dpndnt on th ph of th solution. 9 8 % Rmoval of Ni(II) ions Initial ph Figur 3. Effct of initial ph for th adsorption of Ni(II) ions using PJBC [Ni(II)]=25 mg/l; Tmp=3 C; Adsorbnt dos=25 mg/5 ml; Contact tim=6 minut Adsorption isothrms Th Frundlich and Langmuir isothrm quations wr usd to calculat th adsorption capacity and nrgy of adsorption or intnsity of adsorption. Th linar form of Frundlich 5 isothrm is rprsntd by th quation log q log K logc (4) f n Whr q (mg/g) is th amount of mtal ions adsorbd pr unit wight of th adsorbnt and C (mg/l) is th quilibrium concntration of th adsorbat, K f (mg/g) is masur of adsorption capacity and /n is th adsorption intnsity. Th valu of K f and n ar calculatd from th intrcpt and slop of th plot of log q vs. log C rspctivly. Th linar form of th Langmuir 6 isothrm is givn by C q Q b m Whr C (mg/l) is th quilibrium concntration of th adsorbat, q (mg/g) is th amount of adsorbat pr unit mass of adsorbnt at quilibrium. Th Q m (mg/g) and b (L/mg) ar Langmuir constants rlatd to adsorption capacity and nrgy of adsorption. Th Q m and b ar calculatd from th intrcpt and slop of th plot C /q vs. C. Th isothrm paramtrs wr shown in Tabl.. Tabl. Langmuir and Frundlich paramtr for nickl(ii) ions using PJBC Tmp, o C Langmuir Frundlich Q m b k f n C Q m (5)

5 Chm Sci Trans., 24, 3(3), From th adsorption data, it was clar that Langmuir adsorption capacity (Q m ) valu linarly incrass up to 5 o C aftr that slightly dcrass with incras in tmpratur. Th incras in tmpratur crats mor activ sits on adsorbnt surfac. Hnc monolayr adsorption and pors diffusion of Ni(II) ions wr possibl. Abov 5 o C th monolayr was disturbd, but adsorption intnsity linarly dcrass up to 5 o C and thn incrass with rais in tmpratur. Th Frundlich isothrm indicats that th adsorption capacity incrass with incras in tmpratur and th n valus indicats that th adsorption was highly favorabl procss. Equilibrium paramtr Th favorability of th Langmuir adsorption procss xprssd in trms of dimnsionlss sparation factor or quilibrium paramtr (R L ) which is dfind as R L bc (6) Whr b is th Langmuir constant and C (mg/l) is th initial concntration of th mtal ions. Th R L valus indicat th natur of th adsorption isothrm is ithr linar or favorabl or unfavorabl or irrvrsibl. Th R L valus at diffrnt tmpratur wr calculatd and givn in Tabl 2. Th R L valus btwn and indicats favorabl adsorption for all th initial Ni(II) ions concntrations wr usd. Tabl 2. Equilibrium paramtr (R L ) C Tmpratur 3 o C 4 o C 5 o C 6 o C Thrmodynamic paramtrs Th standard fr nrgy chang (ΔG ), standard nthalpy chang (ΔH ) and standard ntropy chang (ΔS ) wr calculatd using th valu of adsorption quilibrium constants (K ) and tmpratur. Th quilibrium constant K for th adsorption raction was dtrmind from th plot of ln(q /C ) against C at diffrnt tmpraturs suggstd by Khan and Singh 7. Th valu of ΔH and ΔS can b calculatd from th slop and intrcpt of th plot of lnk against /T. Th fr nrgy of adsorption procss rlatd to th quilibrium constant K (L/mol) is givn by th quation G RT ln K (7) Whr ΔG is th fr nrgy chang of adsorption (J/mol), T is th tmpratur in Klvin and R is th univrsal gas constant (8.34 J K - mol - ). Th quilibrium constant, ΔH and ΔS is rlatd to th following quation H S ln K (8) RT R Whr ΔH is th standard hat chang of adsorption (kj/mol) and ΔS is standard ntropy chang (J K - mol - ). Ths paramtrs wr givn in Tabl 3. Th ngativ ΔG valu confirmd th fasibility of th adsorption procss and th spontanous natur of

6 22 Chm Sci Trans., 24, 3(3), adsorption. Th ngativ valu ΔH obtaind indicatd th xothrmic natur of th procss. Th positiv ΔS valu indicats th incras in th randomnss of th Ni(II) ions on PJBC surfac. In this condition th adsorbd watr molculs gain mor translational ntropy du to th displacmnt of th Ni(II) ions, thus allowing th incras in th randomnss in th systm. Th magnitud of ΔS suggsts that th procss was physical adsorption. Tabl 3. Thrmodynamic paramtrs ΔG C 3 o C 4 o C 5 o C 6 o C ΔH ΔS Adsorption kintics Th adsorption kintics dscribs th solut uptak rat. Th kintic modls such as psudo scond ordr and Intra-particl diffusion wr usd to fit th xprimntal data using linar fit analysis mthod. Th psudo scond ordr quation xplaind by Ho and McKay 8,9 is t t (9) 2 qt k q q 2 Whr k 2 is th psudo scond ordr rat constant (g mg - min - ). Th plot of (t/q t ) against tim should giv a linar rlationship from which q and k 2 can b dtrmind from th slop and intrcpt of th plot, rspctivly. Th corrlation cofficints (R 2 ) wr also calculatd. Th intra-particl diffusion modl proposd by Wbr and Morris is q t 2 k t id Whr k id is th intra-particl diffusion rat constant (mg g - min -/2 ) and C is constant. Th slop of th plot of q t against t /2 will giv th valu of th intra-particl diffusion constant. Th kintic data is shown in Tabl.4. Th corrlation cofficints (R 2 ) wr also calculatd. From th kintic data, th q valu calculatd from th psudo scond ordr is almost qual to th xprimntally calculatd q valu. Th rat constant valu is narly sam at particular initial nickl ions concntration with high R 2 valu. In th intra-particl diffusion modl, th por diffusion dcrass with tmpratur raiss from 3 to 6 o C and R 2 valu is gratr than.9. Sinc ths two modl xplain th mchanism of th nickl ions adsorption. C 25 5 C Tabl 4. Kintic paramtrs Tmp, o C Psudo scond ordr Intra-particl diffusion q K 2 x -3 R 2 K id R ()

7 Chm Sci Trans., 24, 3(3), Conclusion Th adsorption of Ni(II) ions from wast watr using a low cost adsorbnt PJBC was invstigatd undr diffrnt xprimntal conditions in batch procss. Th maximum uptak for Ni(II) ions rmoval was found at ph of 5.5. Th adsorption data fittd with both Frundlich and Langmuir adsorption isothrm. Th thrmodynamic paramtrs wr found to b thrmodynamically favourabl physical adsorption procss. Th kintic data fit with th psudo scond ordr and intra-particl diffusion modls. Th rsults of th prsnt studis indicats that th PJBC could b usd for th rmoval of Ni(II) ions from wast watr. Rfrncs. Braukmann B M, Industrial Solution Amnabl to Biosorption; In Biosorption (Editd by Volusky B), CRC Prss, Boca Raton, FL, Dan J G, Bosqui F L and Lanoutt K H, Environ Sci Tchnol., 972, 6(6), ; DOI:.2/s665a7 3. Viraraghavan T and Dronamraju M M, J Environ Sci Halth Part A, 993, 28(6), ; DOI:.8/ Hamd B H, Krishni R R and Sata S A, J Hazard Matr., 29, 62(), 35-3; 5. Frundlich H, Z Phys Chm., 96, 57, Langmuir I, J Amrican Chm Soc., 98, 4(9), 36-43; DOI:.2/ja2242a4 7. Khann A A and Singh R P, Colloids Surfacs, 987, 24(), 33-42; DOI:.6/ (87) Ho Y S and McKay G, Watr Rs., 2, 34(3), ; DOI:.6/S43-354(99) Ho Y S and McKay G, Chm Eng J., 998, 7(2), 5-7; DOI:.6/S (98)76-. Wbr W J and Morris J C, J Sanit Eng Div., 964, 9, 79-7.