Removal of Malachite Green from Aqueous Solutions by Adsorption on to Timber Waste

Transcription

1 Intrnational Journal of Environmntal Enginring and Managmnt. ISSN , Volum 4, Numbr 6 (2013), pp Rsarch India Publications ijm.htm Rmoval of Malachit Grn from Aquous Solutions by Adsorption on to Timbr Wast Dpartmnt of Applid Chmistry, Indian Institut of Tchnology, Banaras Hindu Univrsity, Varanasi , India. Abstract Sawdust a timbr wast has bn usd as a bio-sorbnt for th rmoval of a cationic dy, malachit grn from aquous solutions. Th procss of rmoval has bn optimizd for diffrnt paramtrs lik initial concntration of dy solution and contact tim, ph, adsorbnt dos, and tmpratur. phzpc of th adsorbnt was dtrmind. Elmntal analysis of th adsorbnt was carrid out. FTIR was prformd to dtrmin various functional groups attachd to th adsorbnt surfac. Th xprimntal rsults indicat that 5g/L g of sawdust was abl to rmov 93% of dy from an initial concntration of 20 mg L -1. Equilibrium was achivd in 100 min. Th rmoval of dy xhibitd dcrasing trnd with incrasing tmpratur and it shows xothrmic natur of adsorption. Adsorption data wr modlld by Langmuir and Frundlich isothrms. Th data was bttr fittd in Frundlich isothrm modl. Th maximum adsorption capacity of adsorbnt was found to b mgg 1 at 298 K. Th dy adsorption followd th psudoscond-ordr kintics. Th rsults show that saw dust can b a bttr altrnat for th rmoval of MG from aquous solutions and fflunts. Kywords: Adsorption, sawdust, malachit grn, isothrm. 1. Introduction Today many dys ar bing widly usd in diffrnt industris which discharg larg volums of wastwatr. Th wastwatr contains larg amount of dissolvd dystuff and othr products. Th disposal of dy wastwatr is a big challng and it causs harm to th aquatic nvironmnt (Arulkumar t al., 2011; Wu and Tsng,2008). Som

2 632 of th dys prsnt in wastwatr vn dcompos into carcinognic aromatic amins undr anarobic conditions and caus srious halth problms to human bings as wll as othr animals. Du to th complx molcular structur, dys ar usually vry difficult to b biodgradd, and is too hard to liminat thm undr natural aquatic nvironmnt (McKay t al.,1996). Sawdust is a by-product of timbr industry and it is a common sourc of cllulos and lignin. Sawdust is mainly usd in animal fd and papr production, but othrwis it is discardd as a wast matrial. This polysaccharid has th potntial us in a wid varity of applications, such as food and foddr of animals, pharmacutical and cosmtics industris adhsivs and mulsifirs (Asadullah t al., 2010). Among biological matrials, agricultural matrials usually play an important rol du to bing widly and asily producd. Diffrnt crops ar bing cultivatd all ovr th world such as ric, what, sugar can, corn, tc. ar availabl for dvlopmnt of activatd carbon or itslf a good adsorbnt for diffrnt pollutants lik havy mtals or dys for adsorption xprimntation (Sharma and Uma, 2010). 2. Matrials and Mthods Biomass sawdust, collctd from a local saw mill, Varanasi, was ovn drid at 105 C for 24 h, and thn sivd to kp avrag particl siz in 150 μm rang. Th sivd matrial was collctd in dsiccator for furthr studis without any modification. All th ragnts usd wr of analytical ragnt grad chmicals and wr obtaind from Mrck, Mumbai, India. Stock solution of th dy (malachit grn) was mad by dissolving thm in dionizd watr. Th chmical formula of MG: C 23 H 25 N 2 Cl, molcular wight: 365, λmax ; 618 nm. Th structur of th dy (MG), C.I. No Batch mod xprimnts 50 ml of dy solution of diffrnt concntrations wr takn in 125 ml of cappd ragnt bottls g of adsorbnt was addd in ach ragnt bottl containing 50ml of MG solution and thn agitatd at 100 rpm on tmpratur controlld shakr for various tim intrvals to obsrv th saturation tim. Aftr saturation tim, adsorbnt was sparatd from adsorbat solutions by cntrifugation. Analysis of rsidual concntration of MG in ach sampls was carrid out by Spctrophotomtr(Baush and Lomb. USA). Amount adsorbd pr unit mass of adsorbnt was calculatd by following quation. q = V (1) Whr C i and C ar th initial and quilibrium concntrations of MG rspctivly (mgl -1 ), q is th amount adsorbd pr unit mass of th adsorbnt (mgg -1 ); W is th amount of adsorbnt (gl -1 ).

3 Rmoval of Malachit Grn from Aquous Solutions by Adsorption on to Timbr Rsult and Discussions 3.1Charactrization of sawdust Th surfac charactristics of th sawdust wr dtrmind. Point zro charg of raw sawdust indicats th lctrical nutrality of th adsorbnt surfac at a particular valu of ph. Dtrmination of ph zpc was don to invstigat th surfac bhaviour of sawdust (Mall t al.,2005). Point zro charg of raw sawdust was calculatd by titrimtric mthod and that was FTIR of sawdust wr idntifid in th rang cm _1 using a Fourir transform infrard spctromtr (Simadzu, Japan/8400S). For th spctra, ratio of sampl and KBr is 4 mg of sampls was mixd with 200 mg of spctroscopically pur KBr to prpar pallt of th sampl. Prsnc of diffrnt functional groups shown in figur 2, th main paks for th sampls ar at , , , and cm _1, surfac hydroxyl groups - OH str 1, can b attributd to th strtching vibrations of C-H bonds in alkans indicativ of aldhydic group prsnt on th surfac, th siloxan band appars, larg amounts of cllulos and th porosity of surfac dmand that such a matrial should b usd for adsorption studis. 3.2Effct of initial dy concntration and contact tim Th ffct of diffrnt initial concntration of slctd dy, malachit grn onto saw dust powdr is prsntd in figur 1. Th prcntag rmoval of dy dcrasd with incras in initial dy concntration and showd littl dcras by incrasing concntrations. This can b xplaind that all adsorbnts hav a limitd numbr of activ sits, which bcom saturatd aftr crtain concntration (Snthil Kumar t al., 2010) % Rmoval Contact tim(min -1 ) 20mg/l 30mg/l 40mg/l Figur 1: Effct of initial dy concntration on adsorption of malachit grn by saw dust.

4 634 % Rmoval g/l 5g/l 7g/l Contact tim(min -1 ) Figur 2: Effct of adsorbnt dos on adsorption of malachit grn by saw dust 3.3Effct of adsorbnt dos Figur 2 shows th adsorption profil of malachit grn vrsus diffrnt saw dust dos in th rang of g L 1. It was obsrvd that prcntag of dy rmoval incrasd with incras of adsorbnt dos. Such a trnd is mostly attributd to an incras in th adsorptiv surfac ara and th availability of mor activ adsorption sits (Ghadi t al., 2011). 3.3 Effct of ph ph has bn rcognizd as on of th most important paramtrs that affcts any adsorption procss. Thus th ffct of ph on th rmoval fficincy of malachit grn was studid at diffrnt ph ranging from 4.0 to 8.0. Th maximum adsorption of malachit grn occurrd in th highr (alkalin) ph rang. Th incras in dy rmoval capacity at highr ph may also b attributd to th rduction of H + ions 4. Adsorption Kintics 4.1Psudo first ordr and psudo scond ordr kintics For valuating th adsorption kintics of malachit grn, th psudo-first-ordr kintic modls hav bn usd and found fit to th xprimntal data: log (q - q) = K lo g ( a d q ) t (2) = k (q q) 2 (3) h = k 2 q 2

5 Rmoval of Malachit Grn from Aquous Solutions by Adsorption on to Timbr 635 Th log (q q t ) vrsus t plot (figur7) wr linar with R Howvr, quilibrium adsorption capacitis, q obtaind from ths plots varid widly, Th plot of t/qt against t at diffrnt tmpraturs is shown in Figur 3. Contrary to th psudofirst-ordr quation, th fitting of th kintic data in th psudo-scond-ordr quation showd xcllnt linarity with high corrlation cofficint (R 2 > 0.99) ovr th tmpratur rang of K. Th valu of q and k 2 can b dtrmind by th slop and intrcpt of th straight lin of th plot of t/q t vrsus t. k 2 (gmg 1 min 1 ) is th rat constant of psudo-scond ordr raction. (Ho and McKay,2009) log( q-q) t /q (min g/mg) (298K) (308K) (318K) Tim(min) (298K) (308K) (318K) Contact tim(min) Figur 7: Psudo-first-ordr kintic for adsorption of malachit grn onto sawdust at diffrnt tmpraturs. 5. Equilibrium Sothrm 5.1 Langmuir isothrm Th linar form of Langmuir isothrm assums monolayr adsorption onto a surfac containing a finit numbr of adsorption sits of uniform stratgis of adsorption without intraction btwn adsorbd molculs commonly xprssd as (Uma t al., 2013;Hamd,2009): C q Q b Q C 1 o o (4) whr q (mg g 1 ) and C (mg L 1 ) ar th solid phas concntration and th liquid phas concntration of adsorbat at quilibrium rspctivly, Q o and b ar Langmuir paramtrs rlatd to th capacity and nrgy of adsorption rspctivly. Th constants b and Q o can b dtrmind from th slop and intrcpt of th plot btwn C /q and

6 636 C and at diffrnt tmpratur showing th formation of monolayr covrag of th adsorbat at th outr surfac of adsorbnt. Valus ar prsntd in Tabl 1. Tabl 1: Valus of constants of Langmuir and Frundlich, adsorption isothrm for adsorption of malachit grn on sawdust. Isothrms Tmpratur(K) Paramtrs Langmuir Qo (mg/g) b(l/mg) R Frundlich Kf(l/g) 1/n (l/g) Frundlich isothrm Th Frundlich isothrm is applicabl to non-idal adsorption on htrognous surfacs rsult of th assumption that th adsorption occurs and non-uniform distribution of th hat of adsorption ovr th adsorbnt surfac taks plac (Frundlich,1885). Th linar form of th isothrm can b rprsntd as: 1 lo g q lo g K f lo g C n whr q is th quilibrium dy concntration on adsorbnt (mg g 1 ), C is th quilibrium dy concntration in solution (mg L 1 ), K f (mg g 1 ) (Lg 1 ) 1/n is th Frundlich constant rlatd to sorption capacity and n is th htrognity factor. K f and 1/n ar calculatd from th intrcpt and slop of th straight lin of th plot log q vrsus log C. Highr corrlation cofficint (R 2 ) valus of th straight lins obtaind at ach tmpratur confirm th validity of Frundlich adsorption isothrm for both adsorbnts on th basis of corrlation factor ar dpictd and valus ar prsntd in Tabl 1. (4) 6. Conclusions Saw dust was charactrizd by diffrnt tchniqus. Rmoval fficincy of adsorbnt was found to b quit significant. It was obsrvd that dy rmoval dcras with incrasing concntrations of dy solution. Maximum rmoval for ach concntration rangs can b achivd within 100 minuts only. Rmoval procss was ndothrmic in natur. Psudo scond ordr modl fittd bst in this systm. Various isothrm modls wr applid to invstigat th rmoval procss and it was found that Frundlich isothrm is th most suitabl isothrm for this procss. Th isothrmal data of

7 Rmoval of Malachit Grn from Aquous Solutions by Adsorption on to Timbr 637 Langmuir modl indicat that th adsorption capacity mg/g of this biomatrial is significant. On th basis of this study it can b concludd that application of low cost adsorbnt for th rmoval of malachit grn from aquous solutions. 7. Acknowldgmnt Th authors ar thankful to Dpartmnt of Scinc and Tchnology (Projct M- 48/108), Govrnmnt of India, for providing financial assistanc to Uma. Rfrncs [1] B H Hamd, (2009), J. Hazard. Matr. 15, pp [2] F C Wu, R L Tsng (2008), J. Hazard. Matr. 152, pp [3] G McKay, E Ei-Gundi, M M Nassar (1996). Environ. Prot. 74, pp [4] H Frundlich (1906), J. Phys. Chm. 57, pp [5] I D Mall, V C Srivastva, N K Agarwal, I M Mishra (2005), Chmosphr, 61 (4), pp [6] M Arulkumar, P Sathishkumar, T Palvannan (2011), J.Hazard. Matr. 186, pp [7] M Asadullah, M Asaduzzaman, M S Kabira, M G Mostofa, T Miyazawa (2010), J. Hazard. Matr. 174, pp [8] M Ghadi, H Hossainian, M Montazrozohori, A Shokrollahi, F Shojaipour, M Soylak, M K Purkait, (2011), Dsalination 281, pp [9] P Snthil Kumar, S Ramalingam, C Snthamarai, M Niranjana, P Vijayalakshmi, S Sivansan (2010), Dsalination 261, pp [10] Uma, S. Banrj, Y C Sharma(2013), J.Indust and Engin. Chm. 19,pp [11] Y C Sharma, Uma,(2010). J. Chmical & Enginring Data, 55, pp

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