Indian Journal of Advances in Chemical Science. Adsorption of Lead and Zinc on Curcuma longa Leaf Powder from Aqueous Solutions

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1 Availabl onlin at Adsorption of Lad and Zinc on Curcuma longa Laf Powdr from Aquous Solutions K. Subbarayudu 1, R. Prathibha 1, C. Narasimha Rao 1, K. Sivakumar 2, P. Vnkatswarlu 1 * 1 Dpartmnt of Chmistry, S. V. Univrsity, Tirupati , Andhra Pradsh, India. 2 Dpartmnt of Chmistry, S. V. Arts Collg, Tirupati , Andhra Pradsh, India. Rcivd 09 th January 2017; Rvisd 19 th March 2017; Accptd 20 th March2017 ABSTRACT In this papr, adsorption of lad and zinc on Curcuma longa laf powdr from solutions with nvironmntally rlvant concntrations of mtals was studid. Th kintics of adsorption of mtal ions was analyzd. Optimum ph valus for maximum mtal ion adsorption wr dtrmind. Adsorption isothrms wr xprssd by Langmuir and Frundlich modls. Langmuir adsorption modl fits th xprimntal data rasonably wll than Frundlich modl. Th thrmodynamic paramtrs - such as standard Gibb s fr nrgy chang ( G ), standard nthalpy chang ( H ), and standard ntropy chang ( S ) - wr valuatd, which indicatd that this systm was spontanous and ndothrmic. Th studis showd that this low-cost matrial could b usd as an fficint adsorbnt for th rmoval of lad and zinc from aquous solutions. Ky words: Curcuma longa laf powdr, Adsorption, Lad, Zinc, Kintics, Thrmodynamics. DOI: /IJACS Indian Journal of Advancs in Chmical Scinc 1. INTRODUCTION Havy mtals ar usd in svral industrial applications du to thir usful tchnological attributs. Although many havy mtals ar ncssary in small amounts for th normal dvlopmnt of th biological cycls, most of thm bcom toxic at high concntration [1]. Th wast watr dischargd from ths industris caus toxic mtal concntration of surfac, sa and ground watr rsourcs, and ntr th food chain of humans and othr forms of lif. Havy mtals bing non-biodgradabl tnd to accumulat in living organisms, thus bcoming a prmannt sourc of hazard to halth and lif [2-5]. Havy mtals in aquous solutions ar usually rmovd by various rmdial tchnologis such as adsorption, ion xchang, coagulation, floatation, chmical prcipitation, and rvrs osmosis [6-9]. Biosorption is a biological mthod and can b an altrnativ to convntional wastwatr tratmnt facilitis [10,11]. In this work, Curcuma longa laf powdr is utilizd as biosorbnt to rmov lad and zinc ions from aquous solutions. C. longa is a rhizomatous hrbacous prnnial plant blongs to Zingibraca family and nativ to Indian subcontinnt. Its rhizom is usd as hrbal mdicin and its lavs ar almost do not hav any conomic *Corrsponding Author: pvprofvnkat51@gmail.com Phon: valu aftr sparating from plant. Hnc, in this study, a biosorption mthod for th rmoval of lad and zinc ions using C. longa laf powdr as low-cost biosorbnt has bn dvlopd. 2. EXPERIMENTAL 2.1. Prparation of C. longa Laf Powdr Th lavs wr washd thoroughly with tap watr followd by dionizd watr, and th lavs wr sundrid and crushd to fin powdr by a high-spd rotary cutting mill. A wighd amount (50 g) of C. longa laf powdr was transfrrd into 1000 ml glass bakr and addd 500 ml of dionizd watr. Th rsulting mixtur was stirrd for 1 h and th biosorbnt was sparatd from th solution by filtration, washd with distilld watr svral tims until no color was dtctd in th filtrat. Aftrward, it was drid in an ovn at 70 C for 24 h and kpt in a dsiccator until it rachs room tmpratur and packd in polythn covr for furthr studis. Th rsulting biomass was dsignatd as Curcuma longa laf powdr (CLLP) for furthr rprsntation Prparation of Solutions Lad and zinc solutions of dsird concntration wr prpard by dissolving th appropriat amounts of Pb(NO 3 ) 2 and ZnSO 4.7 H 2 O (Mrck) in distilld watr. Th ph of ach tst solution was adjustd to th 76

2 rquird valu with 0.1 N NaOH or 0.1 N HCl. All th chmicals usd in this study wr of analytical grad Batch Adsorption Exprimnts Adsorption capacity of CLLP was studid by adding g of adsorbnt in 100 ml of lad and zinc solutions at diffrnt concntrations. Th flasks wr sald with glass stoppr and kpt on oscillating shakr; thy ar shakn for 140 min at 160 rpm. To study th ffct of diffrnt factors that ar affcting th adsorption such as of lad and zinc, ffct of ph, ffct of contact tim, a sris of batch xprimnts wr conductd with diffrnt initial concntration of lad and zinc solutions (50, 75, 100, 125 mg L 1 ). Thn, th conical flasks wr put on to th oscillating shakr for 140 min to rach adsorption quilibrium at th fixd shaking spd (160 rpm), thn th concntration of lad and zinc in th filtrat was dtrmind. 3. RESULTS AND DISCUSSION 3.1. Scanning Elctron Microscop (SEM) Analysis Figur 1 shows th SEM micrographs of CLLP bfor and aftr adsorption. From ths imags, it is clar that CLLP has porous and rough surfac txtur, whr thr is a good possibility for th adsorption of lad and zinc. Howvr, it is clarly shown that th surfac of CLLP is covrd with a layr of lad and zinc aftr adsorption Effct of Contact Tim Th ffct of contact tim on th xtnt of adsorption of lad and zinc at diffrnt initial concntration of mtal ions was invstigatd. Th biosorption yild of lad and zinc incrasd considrably until th contact tim rachd 140 min. Furthr incras in contact tim did not nhanc th adsorption. Hnc, th optimum contact tim was slctd as 140 min for furthr xprimnts. a b c Figur 1: (a) Scanning lctron microscop (SEM) imag of Curcuma longa laf powdr bfor adsorption, (b) SEM imag of C. longa laf powdr aftr adsorption of lad, (c) SEM imag of C. longa laf powdr aftr adsorption of zinc Effct of ph Th ffct of ph on th adsorption of lad and zinc by th CLLP was studid in th ph rang Th maximum bioadsorption was obsrvd at ph 6.0 and 5.5 for lad and zinc, rspctivly. Th adsorption could not b carrid out byond ph 6.0 du to prcipitation of Pb(OH) 2 and Zn(OH) 2. At low ph, th hydronium ions concntration is mor hnc ths ar bound to th adsorbnt laving th mtal ions unbound. Whn ph valu is incrasd, th concntration of hydronium ions dcrasd and th mtal ions ar adsorbd on th adsorbnt Kintic Studis Kintic studis wr carrid out to study psudo-first ordr and psudo-scond ordr and intraparticl diffusion modls. Th psudo-first ordr rat quation is [12], K1 log( q qt) = log q t (1) Whr, q and q t ar th amount of mtal ion adsorbd on adsorbnt (mg/g) at quilibrium and at t tim, rspctivly, and K 1 is th rat constant of first-ordr adsorption (min 1 ). Psudo-scond-ordr rat quation can b xprssd as [13,14], t q = 1 t 2 Kq + q (2) t 2 Whr, K 2 is th rat constant of scond ordr adsorption (g/mg min). Th plots ar shown in Figurs 2 and 3. Th quation corrsponds to intraparticl diffusion modl is xprssd as [15], q t =K id t 0.5 +C (3) In Figurs 4 and 5, th initial covrd rgion corrsponds to th xtrnal surfac obtaind, th scond rgion rlats th gradual uptak indicating intraparticl diffusion as th rat limiting stp and final rgion indicats th quilibrium uptak. Th valus of rat constants and corrlation cofficints of kintic studis ar shown in Tabl 1. Compard to psudo-first ordr and intraparticl diffusion kintic modl, a good corrlation cofficint was obtaind for psudo-scond ordr, which indicats that th biosorption follows psudo-scond ordr rat xprssion Equilibrium Studis Th mpirical Frundlich quation basd on adsorption on a htrognous surfac is [16], q K C f 1 n = ( ) (4) Whr, q is th amount adsorbd at quilibrium (mg/g), C th quilibrium concntration (mg/l), K f and 77

3 Figur 2: Psudo scond ordr kintic plots at diffrnt initial concntrations of lad on Curcuma longa laf powdr. Figur 3: Psudo scond ordr kintic plots at diffrnt initial concntrations of zinc on Curcuma longa laf powdr. Figur 4: Wbr-Morris plots at diffrnt initial concntrations of lad on Curcuma longa laf powdr. Figur 5: Wbr-Morris plots at diffrnt initial concntrations of zinc on Curcuma longa laf powdr. Tabl 1: Adsorption rat constants of psudo-first ordr, psudo-scond ordr modl and Wbr-Morris modl for lad and zinc on CLLP. Psudo first-ordr modl Psudo-scond ordr modl Wbr-Morris modl Pb(II) Zn(II) Pb(II) Zn(II) Pb(II) Zn(II) Initial concntration of mtal ion (mg/l) K 1 (min 1 ) R 2 K 1 (min 1 ) R 2 K 2 ([g/mg] min) R 2 K 2 ((g/mg)min) R 2 K id ([mg/g] min 0.5 ) R 2 K id ([mg/g] min 0.5 ) R CLLP=Curcuma longa laf powdr 78

4 Tabl 2: Paramtrs of Langmuir and Frundlich isothrms and thrmodynamic paramtrs for adsorption of lad and zinc onto CLLP. Mtal ion Tmpratur (K) Langmuir constants Frundlich constants ΔG Q (kj/mol) 0 (mg/g) K L (L/mg) R 2 K f (mg/g) 1/n R 2 ΔS (J/mol K) ΔH (kj/mol) Pb(II) Zn(II) CLLP=Curcuma longa laf powdr n ar quilibrium constants indicating th adsorption capacity and adsorption intnsity, rspctivly. Equation (4) can b linarizd in logarithmic form as givn blow, logq = log Kf + 1 log C (5) n Th Langmuir quation has th form [17], C q 1 Qb + C = (6) Q 0 0 Whr, q is th amount adsorbd at quilibrium (mg/g), C th quilibrium concntration (mg/l). Q 0 and b ar Langmuir constants indicating adsorption capacity and nrgy, rspctivly. By plotting 1/C vrsus 1/q, th valu of b can b dtrmind from th straight lin obtaind. Th constants Q 0 and K L ar tabulatd in Tabl 1. From th corrlation cofficint valus of Langmuir and Frundlich modls, it is found that th adsorption of lad and zinc bst fits to Langmuir modl Thrmodynamic Studis Th ffct of tmpratur was studid in th rang of K. Th Gibbs fr nrgy (ΔG ), nthalpy (ΔH ), and ntropy (ΔS ) for th adsorption procss wr obtaind using th following quations. ΔG = RTl n K c (7) ΔG =ΔH TΔS (8) ln K c 0 0 S H = (9) R RT Whr, T is th tmpratur in Klvin, R is th gas constant (8.314 J/mol K), K c is th quilibrium constant. Th nthalpy chang (ΔH ) and th ntropy chang (ΔS ) can b calculatd from a plot of ln K c vrss 1 T (not shown), and th valus ar prsntd in Tabl 2. Valus of fr nrgy changs ΔG ar ngativ confirming that adsorption is spontanous and thrmodynamically favorabl. Th mor ngativ valus of ΔG indicat a highr driving forc to th adsorption procss. Th positiv valus of ΔH indicat that th adsorption procss is ndothrmic in natur. Th positiv valus of ΔS indicat th stability of adsorption procss without any structural chang at solid-liquid intrfac. 4. CONCLUSION Th rsults of this study show that th C. longa laf powdr has suitabl adsorption capacity with rgard to th rmoval of lad and zinc from aquous solution. Th adsorption procss follows psudo-scond-ordr kintics and obyd Langmuir adsorption isothrm. Th ngativ valus of G indicat adsorption is spontanous and positiv valus of H and S wr calculatd and concludd th adsorption procss was ndothrmic. 5. REFERENCES 1. A. Dursun, K. Yudrakok, S. S. Yalcin, G. Tkinalp, O. Aykut, G. Orhan, G. Morgil, (2016) Matrnal risk factors associatd with lad, mrcury and cadmium lvls in umbilical cord blood, brast milk and nwborn hair, Th Journal of Matrnal-Ftal and Nonatal Mdicin, 29(6): P. B. Tchounwou, C. G. Ydjou, A. K. Patlolla, D. J. Sutton, (2012) Havy mtal toxicity and th nvironmnt, EXS, 101: J. E. Saundrs, B. G. Jastrzmbski, J. C. Bucky, D. Enriquz, T. A. MacKnzi, M. R. Karagas, (2013) Haring loss and havy mtal toxicity in a Nicaraguan mining community: Audiological rsults and cas rports, Audiology and Nurotology, 18(2): S. Y. J. Mrcury, R. S. Hoffman, M. A. Howland, N. A. Lwin, L. S. Nlson, L. R. Goldfrank, (2015) Goldfrank s Toxicologic Emrgncis, 10 th d. Nw York, NY: McGraw-Hill Education. p P. A. Myr, M. J. Brown, H. Falk, (2008) Global 79

5 approach to rducing lad xposur and poisoning, Mutation Rsarch, 659(1-2): O. S. Ayanda, F. A. Adkola, A. A. Baba, B. J. Ximba, O. S. Fatoki, (2013) Application of cyanx xtractant in cobalt/nickl sparation procss by solvnt xtraction, Intrnational Journal of Physical Scincs, 8(3): G. J. Rincon, E. J. L. Motta, (2014) Simultanous rmoval of oil and gras, and havy mtals from artificial bilg watr using lctro coagulation/ flotation, Journal Environtal Managmnt, 144: F. Fu, L. Xi, B. Tang, Q. Wang, S. Jiang, (2012) Application of a novl stratgy-advancd fnton-chmical prcipitation to th tratmnt of strong stability chlatd havy mtal containing wastwatr, Chmical Enginring Journal, : Z. Liu, F. Liu, S. Wu, X. Wang, Y. Li, (2013) Rmoval of Phosphorous and Nickl from an Automobil Wast Watr by Coagulation/ Flocculation Combind with Magntit, Intrnational Confrnc on Rmot Snsing, Environmnt and Transportation Enginring (RSETE). 10. T. A. H. Nguyn, H. H. Ngo, W. S. Guo, J. Zhang, S. Liang, Q. Y. Yu, Q. Li, T. V. Nguyn, (2013) Applicability of agricultural wast and byproducts for adsorptiv rmoval of havy mtals from wastwatr, Biorsourc Tchnology, 148: R. Gowda, A. G. Nataraj, N. M. Rao, (2012) Coconut lavs as a low cost adsorbnt for th rmoval of nickl from lctroplating fflunts, Intrnational Journal of Scintific and Enginring Rsarch, 2: S. Lagrgrn, (1898) About th thory of so-calld adsorption of solubl substancs, Handlingar, 24(4): Y. S. Ho, (2004) Citation rviw of lagrgrn kintic rat quation on adsorption ractions, Scintomtrics, 59(1): Y. S. Ho, G. McKay, (1998) Sorption of dy from aquous solution by pat, Chmical Enginring Journal, 70(2): W. J. Jr. Wbr, J. C. Morris, (1963) Kintics of adsorption on carbon from solution, Journal of th Sanitary Enginring Division, ASCE, 89(2): H. M. F. Frundlich, (1906) Frundlich, (1906) Ovr th adsorption in solution, Journal of Physical Chmistry, 57A: I. Langmuir, (1918) Th adsorption of gass on plan surfacs of glass, mica and platinum, Journal of Amrican Chmical Socity, 40(9): *Bibliographical Sktch Prof. P. Vnkatswarlu has mor than 30 yars of taching and rsarch xprinc in th Dpartmnt of Chmistry, S. V. Univrsity, Tirupati. H guidd 15 Ph.D. studnts. H has mor than 115 publications in intrnationally rputd journals which ar indxd in Scinc Citation Indx. H is th rviwr for many Elsvir journals. 80