Batch Adsorption Studies on the Removal of Lead(II) from Aqueous Solution Using Typha Angustata L.

Transcription

1 DOI:1.7598/cst Chmical Scinc Transactions ISSN: , 6(2), RESEARCH ARTICLE Batch Adsorption Studis on th Rmoval of Lad(II) from Aquous Solution Using Typha Angustata L. T. MOHANAPRIYA and P. E. KUMAR * PG and Rsarch Dpartmnt of Chmistry, Erod Arts and Scinc Collg (Autonomous), Erod, Tamilnadu, India mohanapriyachm@gmail.com Rcivd 21 Octobr 216 / Accptd 7 Novmbr 216 Abstract: Batch adsorption studis wr carrid out for th rmoval of lad using activatd carbon TiO 2 nanocomposit. Effct of various factors such as ph, adsorbnt dos, contact tim, initial concntration and tmpratur wr studid. Th kintics and quilibrium data for th adsorption of lad wr analysd by Langmuir and Frundlich isothrm of psudo first and scond ordr. Psudo scond ordr kintics providd th bst fit for kintic data. Kywords: Lad(II), Activatd carbon-tio 2 Nanocomposit, Adsorption, Kintics Introduction Lad is on such havy mtal which, if prsnt in watr, can caus many problms. In watr, lad is rlasd from lad tratmnt and rcovry industris, spcially from lad battry manufacturing units. Lad is toxic to living organisms and if rlasd into th nvironmnt can both accumulat and ntr th food chain. Lad is known to caus mntal rtardations, rducs hamoglobin production ncssary for oxygn transport and it intrfrs with normal cllular mtabolism 1. Lad has damaging ffcts on body nrvous systm. Many rsarchrs hav don th rsarch on using agricultural wast in adsorption of lad. Th rmoval of poisonous Pb(II) from wastwatr by diffrnt low-cost abundant adsorbnts was invstigatd by Ghani t al. 2 Rmoval of th poisonous lad ions from solutions was possibl using as adsorbnts th most ffctiv on. Th ffct of contact tim, initial mtal ion concntration and tmpratur on mtal ions rmoval had bn studid. It was found that adsorbnt for rmoval of havy mtals from wastwatr and this procss is potntially mor conomical than any othr currnt procss tchnology 3. Zuorro t al. 4 studid to provid som information on th adsorption proprtis of ta wast and valuatd th rmoval fficincy of lad ions by spnt lavs of grn and

2 294 Chm Sci Trans., 217, 6(2), black ta. Th rsults from this study indicatd that using adsorbnt may b an fficint and conomical mans for rmoving lad and prsumably, othr havy mtal ions from aquous solutions. Th ability of convrting a wast product, into an conomically chap adsorbnts hav bn invstigatd for Pb(II) and NO 3 - rmoval from aquous solution through adsorption. Th rsults from this study showd that th chmically modifid adsorbnt has considrabl potntials for th rmoval of nitrat and Pb(II) ions from aquous solutions ovr a wid rang of xprimntal conditions through adsorption 5. Many tratmnt mthods 6-16 hav bn rportd in litratur yt adsorption appars to offr th bst prospcts for ovrall tratmnt of wastwatr as th procss is usful for a broad rang of substancs and is normally xcptd to b rvrsibl so that rgnration of th adsorbnt with rsultant conomy of opration may b possibl. In most of th studis activatd carbon 17-2 has bn usd as adsorbnt. Intnsiv studis hav bn carrid out to dvlop mor ffctiv and inxpnsiv adsorbnts which was comparabl to that of activatd carbon. Thus, th sarch for good altrnativs of activatd carbon 21 is still on. Suitabl low cost 22 altrnativ adsorbnts ar ithr natural matrial such as wood, pat, coal, lignit, clays, sand, microorganisms, plant tc., or industrial wast by-products such as slug, fly ash, baggass, rd mud tc. Ths ar gnrally availabl fr of cost or at vry low cost as compard to activatd carbon. Th utilization of industrial wasts as adsorbnts mts to a small xtnt and bnficial for managmnt of wast disposal problm. Lignin, a byproduct from pulp mill, is a matrial known to xhibit adsorption proprtis. Thrfor, in th prsnt work, adsorption of most toxic lad mtal ion on to activatd carbon as an adsorbnt has bn invstigatd. Exprimntal Typha Angustata L. flowrs wr collctd from th Prundurai, at Erod (Dt) in Tamilnadu, India. Thy wr cut into small pics and drid for 25 days. Th flowrs wr drid and burnt th muffl furnac at 45-5 o C and kpt it for half an hour. Th collctd th carbonizd matrial was ground wll and sivd to a suitabl particls siz. Activatd carbon (AC) has bn stord in plastic vssls for th furthr studis. Th particl siz of.15 to.25 mm was usd. Prparation of AC- TiO 2 -Nanocomposit Activatd carbon (3 g) was allowd to swll in 15 ml of watr-fr alcohol and stirrd for 2 h at 25 o C to gt a uniform suspnsion. At th sam tim, th titanium dioxid (3 g) was disprsd into watr-fr alcohol 15 ml thn th dilutd titanium dioxid was slowly addd by dropping it into th suspnsion of AC and stirring continud for anothr 5 h at 25 o C. Thn 5 ml alcohol mixd with.2 ml dionizd watr was addd slowly and stirring continud for anothr 5 h at 25 o C. Th suspnsion was thn kpt ovrnight for 1 h at room tmpratur and th prcipitat obtaind was carfully dhydratd in a vacuum ovn for 6 h at 8 o C to a charactristic of th AC- TiO 2 -nanocomposit wr dtrmind. Adsorbat solution A stock solution of Pb 2+ was prpard by dissolving g of anhydrous PbNO 2 in watr, acidifid with 1 ml of con.nitric acid and 1L of lad solution. Working standards wr prpard by diluting diffrnt volums of th stock solution to obtain th concntration. Lad ions concntrations wr dtrmind at charactristic wav lngth (λ max = 52 nm) with a doubl bam UV- Visibl spctrophotomtr.

3 Chm Sci Trans., 217, 6(2), Charactrization of absorbnt Physicochmical charactristics of th adsorbnts wr studid as pr th standard tsting mthods. Th XRD pattrn of pur activatd carbon and that of AC-TiO 2 nano composition. λ λ 2θ Figur 1(a). X-Ray Diffraction pattrn of th activatd carbon Figur 1(b). X-Ray Diffraction pattrn of th activatd carbon TiO 2 Nanocomposit Figur 1(a & b) shows charactristics pak at 28 o and 3 o, which confirm th prsnc of A-C-TiO 2 phas in th nano composit. Th rcordd pattrns wr analyzd using to dtrmining pak position, width and intnsity. Full-width at half-maxima (FwHm) data was analyzd by Schrr s formula to dtrmin avrag particl siz.9λ t =. β cos Th surfac morphology of th adsorbnt was visualizd by scanning lctron microscopy (SEM) shown in Figur 2(a & b). Th diamtr of th composit rang is 1 µm to 1 µm. 2θ Figur 2(a). SEM imag of activatd carbon FT IR spctroscopy Figur 2(b). SEM imag of activatd carbon- TiO 2 Nanocomposit Th absorption bands ar du to th strtching and bnding vibration of th group. Th frquncy of carbon pak is cm -1 and typ of band N-H similarly cm -1 and typ of band C-H th frquncy of TiO 2 pak cm -1 is prsnt in C-H bonding. Batch absorption xprimnt Batch adsorption xprimnts wr also prformd by agitation.1 g of th adsorbnt with 5 ml of lad solution th ph containing diffrnt initial concntration form 1 to 4 mg/l

4 296 Chm Sci Trans., 217, 6(2), at 3 o C. Aftr th stablishd contact tim (2h) was attaind, th suspnsion was filtrd and suprnatant was analyzd for th mtal concntration of 1 to 4 mg/l and th adsorbnt dosag of.1 g was adjustd in th rang of 4-11 by using dil HCl and NaOH solution. Exprimnts wr carrid out by varying th adsorbnt amount from.1 to 1. g with Pb(ll) concntration ranging from 1 to 4 mg/l. Th concntration of Pb(ll) in th fflunt was dtrmind spctrophotomtr by dvloping a ros colour using.1% PAR ragnt, buffr solution as complxing agnt in acidic solution. (a) (b) Figur 3. (a) FT-IR Spctrum of activatd carbon and (b) FT-IR Spctrum of activatd carbon +TiO 2 Nanocomposit

5 Chm Sci Trans., 217, 6(2), Th prcntag rmoval of mtal and amount of mtal adsorbd on AC- TiO 2 Nanocomposit was calculatd by quation (1) and (2) rspctivly. 1( Co C) %%R Rmoval = (1) C [ Co C] v q = (2) w Whr q is th quantity of mtal adsorbd on th adsorbnt at th tim of quilibrium (mg/l), C and C ar th initial and quilibrium concntration (mg/l). V is th volum of solution, W is th wight of adsorbnt. Adsorption isothrm Th adsorption isothrm was analyzd using Langmuir, Frundlich and Tmpkin isothrm. Langmuir adsorption isothrm Th thortical Langmuir isothrm is oftn usd to dscrib adsorption of a solut from a liquid solution as C 1 C = + (3) q Q K Q L Whr q is th amount of mtal adsorbd pr unit mass of adsorbnt (mg/l) and C is th quilibrium concntration of th adsorbat (mg/l) and q and b is Langmuir constants rlatd to adsorption capacity and rat of adsorption rspctivly. As rquird by quation 3, plotting C /q against C gav a straight lin, indicating that th adsorption of havy mtal on th nanocomposit follow th Langmuir adsorption isothrm (Figur 4). Th Langmuir constant K L is valuatd from th slop and intrcpt of th graph. Th ssntial faturs of Langmuir isothrm can b xprssd in trms of a dimnsionlss constant sparation factor R L which is dfind by th following quation 1 RL = (4) 1+ K C Whr, C is th initial concntration of adsorbat (mg/l). K L is th Langmuir adsorption constant (L/mg). R L valu lis btwn and 1 indicats favorabl adsorption 28. Frundlich iothrm Th Frundlich isothrm 27 is gnrally usd for mathmatical dscription of adsorption in aquous systm and dscribs htrognous surfac nrgis. Th quation can b xprssd in logarithmic form as log q = log k + 1/ n logc (5) f Whr q is th amount of mtal adsorbd in mgl -1, C is th quilibrium concntration (mgl -1 ), K f and n wr Frundlich constant. (mg/g, L/mg) rlatd to adsorption capacity and adsorption intnsity of th sorbnt rspctivly. Th plot of logq vs. logc gav straight lins with good rgrssion cofficint indicating that th adsorption of havy mtal follow th Frundlich isothrm (Figur 5). Tmpkin isothrm Tmpkin isothrm is rprsntd by th following quation RT q = ln[ AC] b (6) Equation 6 can b xprssd in its linar form as q = B ln A + B ln C (7) L

6 298 Chm Sci Trans., 217, 6(2), Whr B is a constant rlatd to th hat of adsorption (J/mol) and A is th Tmpkin isothrm constant, corrsponding to th maximum binding nrgy (L/mg). A plot of q vs. InC is shown in Figur 6. Th valus of A and B calculatd from th slop and intrcpt of th graph ar givn in Tabl C/q 8 6 log q R 2 = R 2 = C Figur 4. Langumuir plot for th adsorption isothrm log C Figur 5. Frundlich plot for th adsorption isothrm q R 2 = In C Figur 6. Tmpkin plot for th adsorption isothrm Initial mtal concntration, mg/ L ppm 2ppm 3ppm 4ppm Tim Figur 7. plot of th psudo first ordr kintic modl by AC-TiO 2 -Nanocomposit Tabl 1. Rsults of isothrm plots for th adsorption of lad on AC-TiO 2 AC Q, mg/g Langmuir isothrm b, L/mg log q-qt Frundlich isothrm Tmpkin isothrm R 2 R L K f N R 2 A B R

7 Chm Sci Trans., 217, 6(2), Adsorption kintics Th kintics of adsorption of lad by th nano composit and th kintic modls of psudo first ordr, psudo scond ordr and intrapartid diffusion modl wr considrd. Psudo first ordr kintics Th psudo first ordr kintics modl can b rprsntd as log(q -q t )=logq -(k 1 /2.33) (8) Whr q is th amount of mtal adsorbd at quilibrium (g/mg). q t is th amount of mtal adsorbd at tim (mg/g) and k 1 is th psudo first ordr rat constant k 1 and q can b calculatd from th slop and intrcpt of th graph (Figur 7). Th q (cal) and q (xp) valu ar shown in Tabl 2. Th adsorption procss dos not follow first ordr kintics. Psudo-scond ordr kintic modl Th linar psudo scond ordr kintic quation is givn as. t/q t = 1/(k 2 q 2 ) + 1/q t (9) Whr k 2 is rat constant of scond ordr adsorption (g mg -1 min -1 ). As xpctd th plot of t/q t vs. t (Figur 8) was linar. Th valus of q and k 2 can b calculatd from th slop and intrcpt. Th q (cal) and q (xp) valus ar shown in Tabl 2. Th calculatd q (cal) valus ar in consonanc with q (xp) with high corrlation cofficint valus. Th adsorption of AC-TiO 2 Nanocomposit followd psudo-scond ordr kintics. Tabl 2. Th kintic paramtr for th adsorption of lad by AC-TiO 2 -NC adsorbnt Initial mtal concn Psudo first ordr Psudo scond ordr Intraparticl diffusion tration, mg/l k 1 q (xp) q (cal) R 2 k 2 q (xp) q (cal) R 2 K id C R Intraparticl diffusion Th intraparticl diffusion modl usd hr rfrs to th thory proposd by Wbr and Morris 28 basd an intraparticl diffusion cofficint K id is dfind by th quation, q t = k id t 1/2 + C (1) Whr K id is th intraparticl diffusion rat constant (mg/gmin 1/2 ), C is th intrcpt (mg/g) can b calculatd by plotting q t vs. t 1/2 and th rsults ar givn in Figur 9 and Tabl 2. Th linar portion of th plot dos not pass through th origin. Such a dviation from th origin indicats that por diffusion is th only controlling stp and not th film diffusion. Thrmodynamic paramtrs Th thrmodynamic paramtrs for th sorption procss could b dtrmind from th xprimntal data obtaind at various tmpraturs using th quation o o ln kc = S / R H / RT (11) G o = H T S (12) Whr k c is th Langmuir constant rlatd to th nrgy of adsorption, R is th gas constant and T is th absolut tmpratur (K). Th adsorption procss such as fr nrgy chang ( G o ), nthalpy chang ( H o ) and ntropy chang ( S o ), suggst that ndothrmic and spontanous.

8 t 3 Chm Sci Trans., 217, 6(2), ppm 2ppm 3ppm 4ppm qt ppm 2ppm 3ppm 4ppm t/qt Tim (t) Figur 8. Plot of th psudo scond ordr kintic modl byac-tio 2 -Nanocomposit Rsults and Discussion Effct of contact tim and initial mtal concntration Figur 9. Plot of th intraparticl diffusion kintic modl byac-tio 2 -Nanocomposit Th ffct of contact tim shows that quilibrium is achivd fastr 1 to 21 min with nano composit. It is obsrvd that in both cass th prcntag rmoval of Pb(II) ion incras with incras in mtal ion concntration Figur 1. Th rat of adsorption is vry fast initially with about 96% of th total lad bing rmoval within fw minuts followd by an incrasd rat with th approach of quilibrium. Th rmoval rat is high initially du to th prsnc of th binding sitd which gradually bcom saturatd with tim rsulting in incrass rat of adsorption as quilibrium approachd finally attain. t 1/2 1 1 % Rmoval of lad ppm 2ppm 3ppm 4ppm % Rmoval ppm 2ppm 3ppm 4ppm Tim Figur 1. Effct of agitation tim and initial mtal ion concntration Pb by AC- TiO 2 -Nanocomposit Effct of adsorbnt dosag on adsorption procss Absorbant dos Figur 11. Effct of th adsorbnt dosag for Pb by AC-TiO 2 -Nanocomposit Th ffct of dos adsorbnts undr study on th rmoval of lad is shown in Figur 11. This illustrats th adsorption of lad ion with chang of th adsorbnt dos from.1 to 1. g. Th rsults showd that within th amount incras in adsorbnt concntration thr is an incras adsorbd pr unit mass of th adsorbnt.

9 Chm Sci Trans., 217, 6(2), Effct of tmpratur Tmpratur studis shown in Figur 12 at diffrnt tmpraturs 3, 34, 38 and 4 o C. It is obsrvd that adsorption of lad ions incrass with incrasing tmpratur showing th procss to b ndothrmic % of Rmoval c 34 c 38 c 42 c % of Rmoval ppm 2ppm 3ppm 4ppm Tim Figur 12. Effct of Tmpratur for Pb by AC-TiO 2 -Nanocomposit Effct of ph Figur 13. Effct of ph for Pb by AC-TiO 2 - Nanocomposit on mtal ion Adsorption of Pb(ll) was studid at various ph valus and rsults ar dpictd in Figur 13. Th initial ph of solution was varid from 4 to 1 with th adsorbat various concntration of 1-4 mg/l maintaining th adsorbnt dos at.1 g and th contact tim at 2 hours for nanocomposit. Th rsidual Pb(II) ions wr analysd with atomic absorption spctrophotomtr. From this figurs it is clar that lad adsorption fficincy is highst at ph 8-11 with nanocomption ph ZPC for th nanocomposition was dtrmind as 9.. Adsorption isothrms Th capacity of th adsorption isothrm is fundamntal and plays an important rol in th dtrmination of th maximum capacity of adsorption. In ordr to adapt for th considrd systm, an adquat modl that can rproduc th xprimntal rsults obtaind, quations of Langumuir, Frundlich, Tmpkin hav bn considrd Adsorption kintics Th study of adsorption kintics is significant as it provids valuabl information about th raction pathways and th mchanism of th raction. Th kintics of Pd(II) on activatd carbon - TiO 2 nanocomposit was analyzd using psudo first ordr, psudo scond ordr, and intra particl diffusion modls. Thrmodynamic paramtr Thrmodynamic paramtrs provid in-dpth information of inhrnt nrgtic changs associatd with adsorption; thrfor, ths paramtrs should b accuratly valuatd. Th thrmodynamic valus wr calculatd from th graph plottd btwn lnk c vs, 1/T (Figur 14 & Tabl 3). Changs to G o, H o and S o wr calculatd to lucidat th procss of adsorption. Th low H o valu dpicts Pd ion ar chmisorption onto adsorbnt activatd carbon. TiO 2 nanocomposit th ngativ valus of G o shows th adsorption is highly favorabl and spontanous. ph

10 32 Chm Sci Trans., 217, 6(2), In kc C /T Figur 14. Eyring plot Tabl 3. Thrmodynamic paramtr valus G, kj/mol S, J/mol/K H, kj/mol 33K 37K 311K 314K Dsorption studis Dsorption studis with actic acid rvald that th rgnration of adsorbnt was not satisfactory, which confirm th chmisorptiv natur of adsorption. Conclusion Th adsorption isothrms valuatd that Ac- TiO 2 -NC can b usd as adsorbnt for rmoval of lad ion. Th amount of mtal adsorbd varid with initial mtal concntration, adsorbnt dos, ph and tmpratur. Adsorption isothrms of th adsorbnts undr study wr valuatd using Frundlich, Langmuir and Tmpkin isothrm. Th kintic rsults for th xprimntal data of adsorption th lad onto activatd carbon TiO 2 nanocomposit wr bttr follows psudo scond ordr quation. Dsorption studis rvals that satisfactory which confirms th chmisorptiv natur of adsorption. Th sorption procss was found to b ndothrmic and spontanous. Rfrncs 1. Qaisr S, Salm A R and Ahmd M M, Environmntal Biotchnol., 27, 1(3), Abdl Ghani N T, Hfny M and El-Chaghaby G A, Int J Environ Sci Tchnol., 27, 4(1), 67-73; DOI:1.17/BF Bulut Y and Zki T, J Environ Sci., 27, 19(2), ; DOI:1.116/S11-742(7) Zuorro A and Lavcchia R, Am J Appl Sci., 21, 7(2), ; DOI:1.3844/ajassp Goncharuk V V, Kuchruk D D, Kochkodan V M and Badkha V P, Dsalination, 22, 143(1), 45-51; DOI:1.116/S (2) Graham N J D, Brando C C S and Luckham P F, J Am Watr Works Asso., 1992, 84, Lin S.H. and Png C F, Watr Rs., 1996, 3(3), ; DOI:1.116/ (95)21-3

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