Studies on removal of malachite green from aqueous solution by sorption method using water hyacinth - Eichornia crassipes roots

Transcription

1 Journal of Biodivrsity and Environmntal Scincs (JBES) ISSN: (Print) (Onlin) Vol. 2, No. 1, p. 1-8, ESEAH PAPE OPEN AESS Studis on rmoval of malachit grn from auous solution by sorption mthod using watr hyacinth - Eichornia crassips roots Gopinath 1*, Karthiyan 1, Sivaumar 1, Magsh 1, MohanaSundaram 1, Poongodi 1, amsh 2, ajamohan 2 1 Dpartmnt of Biotchnology, Karpaga Vinayaga ollg of Enginring and Tchnology, Maduranthagam , TamilNadu, India 2 Dpartmnt of hmical Enginring, Annamalai Univrsity, Tamil Nadu, India civd: 05 Dcmbr 2011 visd: 19 January 2012 Accptd: 21 January 2012 Ky words: Watr hyacinth roots, malachit grn, sorption, intics. Abstract Dy containing wast watr can caus srious watr pollution problms by hindring light pntration and photo synthsis and toxicity from havy mtals associatd with dys. In this rsarch study, batch xprimnts wr conductd using thrmally activatd Eichornia crassips roots as an adsorbnt for th rmoval a basic dy, malachit grn, from auous solutions. Effct of oprating variabls i.. ph, sorbnt dosag, dy concntration and contact tim was studid in an agitatd batch adsorbr. sults showd that maximum dy upta was obsrvd at an optimum ph 7.Thr was no significant diffrnc in dy concntration rmaining whn th ph incrasd from Dy rmoval was influncd by initial dy concntration and th sorption procss followd first ordr intics. Among th thr isothrms tstd dlich Ptrson and Langmuir isothrms fittd rasonably wll to th data. Th ngativ valu of th fr nrgy chang indicats th spontanous natur of biosorption. From th abov findings, it was obsrvd that th biosorption procss obyd th first ordr adsorption intics. Th ngativ valu of th fr nrgy chang calculatd indicats th spontanous natur of th sorption and confirms th affinity btwn th sorbnt and th dy cations. * orrsponding Author: Gopinath mpgopinath1980@gmail.com 1 Gopinath t al.

2 Introduction Dys ar important watr pollutants which ar gnrally prsnt in th fflunts of th txtil, lathr, food procssing, dying, cosmtics, papr, and dy manufacturing industris. Thy ar synthtic aromatic compounds which ar mbodid with various functional groups (Bhatnagar t al., 2005). Ths colourd compounds ar not only asthtically displasing but also inhibiting sunlight pntration into th stram and rducing th photosynthtic raction. Som dys ar also toxic and vn carcinognic. Thrfor, it is highly ncssary to rduc dy concntration in th wastwatr (Wang t al., 2005). Th stability of dys towards light and oxidizing agnts also crat a problm for thir rmoval by diffrnt wast tratmnt procdurs. Hnc, thir rmoval mthods ar slctd with a grat dal of car and thoughtfulnss. Formrly, convntional mthod adoptd by txtil industris for rmoval of coloration from thir disposd wast includs froth flotation, flocculation, coagulation tc. Howvr, all such mthods wr found infficacious and incomptnt (Gupta t al, 2004). Som of th dys and pigmnts prsnt in ths fflunts rsist biological oxidation and ruir trtiary tratmnt (Bhattacharyya t al, 2005). ytoplasmic azo rducats play an important rol in th anarobic biodgradation of azo dys to produc colourlss aromatic amins. Although complt minralization is difficult, th rsulting aromatic amins producd during anarobic dgradation may b toxic and carcinognic. Ths amins ar rsistant to furthr anarobic minralization. During th last 10 yars, th attntion has bn shiftd towards adsorption tchniu, which has mrgd as on of th widly accptd mthods for th rmoval of all such contaminants (Gupta t al, 2004). Granular or powdrd activatd carbon is th most widly usd adsorbnt bcaus it has an xcllnt adsorption capability for organic compounds, but its us may b limitd du to its high cost (Bhattacharyya t al, 2005). This has ld many worrs to sarch for chapr sourcs to prpar activatd carbons or chapr substituts li fly ash, silica gl, wool wasts, blast furnac sludg, and clay matrials (bntonit, aolinit, montmorillonit, tc.). Th ability of watr hyacinth (Eichornia crassips) to rmov havy mtals in solution is wll documntd (Low t al, 1995). It was found that th mtals wr mostly concntratd at th roots of th plant and translocation appard to b slow. This mans that th root systm could act as a biosorbnt for various matrials, which ar solubl in watr. This study also aimd to rmov th dy malachit grn from th auous solution using thrmally activatd watr hyacinth roots as adsorbnt and to study th ffcts of procss variabls li activation tmpratur, initial ph, sorbnt dosag and initial dy concntration on amount of dy upta with uilibrium and intics of sorption mchanism. Matrials and mthods Prparation of adsorbnt Th watr hyacinth roots usd in this study wr obtaind from a pond situatd bhind th Dpartmnt of hmical nginring, Annamalai Univrsity, Annamalai nagar, Tamilnadu, India. Th collctd plant biomatrial was xtnsivly washd with tap watr to rmov soil and dust and slicd into pics manually. Th slicd matrial was drid by xposur to th sunlight for 3 days and subsuntly at 80º for 4 h in a hot air ovn. Th drid matrial was milld into fin powdr and allowd to pass through a + 65 to 80 msh opning siz siv. Th sivd powdr was thrmally activatd at diffrnt tmpraturs for various tims in an inrt atmosphr and coold to room tmpratur. Th activatd sorbnts wr stord in dsiccators bfor us. Prparation of Malachit grn solution Th cationic dy malachit grn was obtaind from DH hmicals, Nw Dlhi and usd without furthr purification. Th dy stoc solution of 100 mg/l was prpard using distilld watr. Th xprimntal solution was prpard by diluting th stoc solution with distilld watr whn ncssary. 2

3 Effct of thrmal activation Th ffct of thrmal activation on th uilibrium upta of malachit grn was stimatd at maximum concntration of stoc solution (100 mg/l). In th prsnt study watr hyacinth roots wr subjctd to four diffrnt tmpraturs and tim li 500º for 2 hr, 400 º for 3 hr, 300º for 3.5 hr and 200 º for 4hr. In th prliminary studis, it was showd that th highr activation tmpratur dcrasd th amount of dy adsorbd by th adsorbnt and th adsorption capacity of th untratd watr hyacinth roots was also rportd. During this study, th dy solution was usd as such and no ph altrations wr mad. Th uilibrium upta capacity was dtrmind by agitating 50mL of auous solution with 0.1 g of sorbnt dosag at th constant spd of 200rpm, bfor starting th xprimnts all th bars wr covrd with aluminum foil in ordr to prvnt hat loss du to vaporation. Agitation was prformd using magntic stirrrs for 6 hrs, which is mor than sufficint to rach th uilibrium. Sampls wr thn cntrifugd and dy concntrations in th suprnatant wr analyzd using UV spctrophotomtr by monitoring th absorbanc changs at a wav lngth of maximum absorbanc. Effct of ph Th ffct of ph on th dy upta was studid by agitating 100mg/L Malachit grn solution with 0.1g of watr hyacinth roots in th ph rang of Th dy solutions wr adjustd to th ruird initial ph valus by adding Hl or NaOH. Effct of sorbnt dosag In ordr to find out th ffct of sorbnt dosag on th dy upta a st of trials wr carrid out with thrmally activatd watr hyacinth roots, whos dosag rangs from 0.1 to0.5 g pr 50 ml of auous dy solution through out this st of xprimnts, dy concntration was maintaind constant at 100 mg/l. Aftr shaing, th sampls wr analyzd for color rduction in th UV spctrophotomtr. Effct of contact tim Thrmally activatd watr hyacinth roots wr shan with 50 ml of auous dy solution whos concntration varid in th rang of 25 to 100 mg/l. Twlv magntic stirrrs running at diffrnt contact tim intrvals wr usd to prform intic studis. Each stirrr was switchd off at rgular tim intrvals and dy concntrations in sampls wr analyzd using UV spctrophotomtr. sults and discussion Effct of thrmal activation Fig.1. shows th amount of dy adsorbd at diffrnt thrmal activation tmpraturs. (mg/g) was obtaind from a simpl mass balanc E (1) as shown blow; V ( o ) M (1) (mg/g) is th amount of dy adsorbd at uilibrium, V (L) is th volum of th solution tratd, o (mg/l) is th initial dy concntration, and M (g) is th adsorbnt dosag. It was obsrvd that th watr hyacinth roots activatd at 200º for 4 hrs showd th maximum upta capacity of malachit grn. Th upta capacity of sorbnt was found to dcras with incras in tmpratur abov 200º. As a rsult, 200º was found as th suitabl activation tmpratur. Th ffct of thrmal activation was provd to b vital as allow dy upta capacity of mg/g was attaind with 100mg/L malachit grn solution whn th watr hyacinth roots wr usd without any activation. Tabl 1. Euilibrium isothrm constants at 30º. Frundlich isothrm K F (mg/g) (L/g) n 1/ n 2 L L/mg Langmuir isothrm o mg/g h L/g

4 Tabl 2. constants at 30º. dlich- Ptrson uilibrium isothrm dlich-ptrson isothrm a b Effct of ph Bcaus initial ph of solution can significantly influnc sorption of dys, th ffct of ph on dy sorption by th watr hyacinth roots was studid. Th valu of ph usd rang from 2 to 11.As lucidatd in Fig.2, th maximum dy upta was at th initial ph 5.0. Th dy adsorbd incrasd as th initial ph was incrasd from 2 to 5.Whn th ph varid from 5 to 10 th amount of dy adsorbd rmaind narly constant. Prviously, a numbr of studis hav rportd that thr xist a linar rlation btwn ph and th amount of dy (basic) adsorbd (Vasanth Kumar t al, 2005).At lowr ph, th sorbnt surfac might hav bcom ngativly chargd attracting mor of th basic dy molculs. 2 It is lily that chargs dvlop on th surfac of an adsorbnt in an acidic mdium, rsulting in a highr adsorption of anionic dys than in cationic dys. If this is th cas, th sorption of cationic dy should dcras at a lowr ph (Low t al, 1990). As rsult of this study, th optimal ph was shown to b 7. Tabl 3. Kintic constants for sorption of Malachit grn onto watr hyacinth roots. o mg/l 1 min-1 Effct of sorbnt dosag From Fig 3., it was obsrvd that th dy upta on th watr hyacinth roots was dcrasd with incrasing amount of sorbnt dosag whras, th ffct of sorbnt dosag on th % color rmoval 1 2 d mg/g. min 1/ incrass with incrasing sorbnt dosag. This may b du to th fact that th amount of solut sorbd onto unit wight of sorbnt gts splittd with incrasing sorbnt concntration (Waranusantigul t al, 2003). Th rlation btwn and sorbnt dosag was found to fit th uation with th highr corrlation cofficint of (2) Biosorption uilibrium Th Langmuir, Frundlich and dlich and Ptrson isothrms ar th most fruntly usd two paramtr modls in th litratur dscribing th non-linar uilibrium btwn amount of dy adsorbd on th acid tratd watr hyacinth roots ( ) and uilibrium concntration of ( ) at a constant tmpratur( 30º). solution Th Langmuir uation, which is valid for monolayr sorption onto a homognous surfac with a finit numbr of idntical sits, is givn by E. (3). o L (3) 1 L whr paramtrs o and L ar Langmuir constants rlatd to maximum adsorption capacity (monolayr capacity) and bonding nrgy of adsorption, rspctivly, which ar functions of th charactristics of th systm as wll as tim. Th valus of linar plot of o and L can b dtrmind from th / vrsus. Th Langmuir uation usd for homognous surfacs is, h L o (4) 1 (5) h o Th Langmuir adsorption isothrm assums that th adsorbd layr is on molcul in thicnss. Th Frundlich isothrm modl assums nithr homognous sit nrgis nor limitd lvls of sorption. Th Frundlich modl is th arlist nown rlationship dscribing th sorption uilibrium and is xprssd by th blow mntiond E (6): 4

5 Whr 1/ n KF (6) K F and n ar th Frundlich constants rlatd to adsorption capacity and adsorption intnsity. E (6) can b linarizd in logarithmic form and Frundlich constants can b dtrmind. log 1 log KF log (7) n Fig 1. Effct of ph on uilibrium on upta of malachit grn (M:0.1G;V:50ML;O:100MG/L;TEMP:30O). Th Frundlich uation prdicts that th dy concntration on th adsorbnt will incras so long as thr is an incras in th dy concntration in th liuid. Jossns and co-worrs modifid th thrparamtr isothrm first proposd by dlich and Ptrson to incorporat faturs of both th Langmuir and Frundlich uations. dscribd as follows: K (8) b 1 a It can b At low concntrations th dlich-ptrson isothrm approximats to Hnry s law and at high concntrations its bhavior approachs that of th Frundlich isothrm. Th linarizd form of th E (8): K ln 1 b ln ln a (9) Th dlich-ptrson isothrm constants and K, a b th cofficints of corrlation ar prsntd in Tabl 2. Th bst fit uilibrium modl was dtrmind basd on th corrlation cofficint. dlich-ptrson isothrms xhibit xtrmly high valu of corrlation cofficint (0.9997) followd by th Langmuir and Frundlich isothrms with corrlation cofficint of and rspctivly. Also th highr valus of adsorption capacity, o (45.75) indicat th prsnc of strong lctrostatic forc of attraction (Vasanth Kumar t al, 2005). Th valu of Frundlich xponnt ( n ) lying in th rang of 1-10, indicats favourabl adsorption. Kintic modling Psudo-First ordr modl In ordr to invstigat th mchanism of biosorption and potntial rat controlling stps, such as mass transport and chmical raction procsss, intic modls hav bn usd to tst th xprimntal data. Whn th biomass is mployd as a fr and smallsizd thrmally tratd watr hyacinth roots suspnsion in a wll-agitatd batch systm, all th watr hyacinth roots binding sits ar mad radily availabl for mtal upta. Hnc, th ffcts of xtrnal film diffusion and intraparticular diffusion on biosorption rat can b assumd not significant and ignord in any nginring analysis. Th intic modls including th psudo first-ordr, psudo scond-ordr and saturation typ can b usd in this cas assuming that masurd concntrations ar ual to adsorbnt surfac concntrations. Th firstordr rat xprssion of Lagrgrn is basd on whr d 1( ) dt (10) and ar th amounts of adsorbd dy on th biosorbnt at uilibrium and at tim t rspctivly, and 1 is th rat constant of first-ordr biosorption. Aftr intgration and applying boundary conditions, t =0 to t = t and =0 to = ; th intgratd form of E. (9) bcoms: log( 1 ) log t (11) A straight lin of log( ) vrsus t suggsts th applicability of this intic modl. Th first ordr rat 5

6 constant 1 valus wr calculatd from th slop of th lin in Fig.5. Th calculatd 1 valus and thir corrsponding linar rgrssion corrlation cofficint valus wr shown in th Tabl 2. Th corrlation cofficints wr found to xist in th rang of to with an avrag of , which shows that this modl can b applid to prdict th sorption intics. obtaind from th slops of th linar portion of th plots vrsus t 1/2 from Fig.7. Various valus of d at diffrnt initial dy concntration ar listd in Tabl 3. From Fig.7.it, may b sn that thr ar two sparat rgions. Th initial portion is attributing to th bul diffusion and th linar portion to intra particl diffusion (Alln t al, 1989). Th dviation of straight lin from th origin indicats that th por diffusion is not th sol rat controlling stp (Mall t al, 2005). It is obsrvd th rat constant for intraparticl diffusion incrasd with incrasing dy concntration. Similar rsult was obtaind by Low K.S., and L..K, 1995 in thir study on rmoval of mthln blu by sorption on watr hyacinth roots. Fig 2. Effct of ph on uilibrium upta of Malachit grn (M:0.1g;V:50ml;o:100mg/L;Tmp:30o). Diffusion modl Th intraparticl diffusion modl prsntd hr rfrs to th thory proposd by Wbr and Morris who concludd that th upta is proportional to th suar root of contact tim during th cours of adsorption. Th amount of dy sorbd at diffrnt initial concntrations on watr hyacinth roots was plottd against th suar root of tim of upta (t 1/2 ). t 0.5 d (12) Fig 4. Langmuir plot for sorption of Malachit grn onto watrhyacinth roots (M:0.1g;V:50mL;pH:7.0;Tmp:30º ). Fig 5. Frundlich plot for sorption of Malachit grn onto watr hyacinth roots (M:0.1g;V:50mL;pH:7.0;Tmp:30º ) Fig 3. Effct of sorbnt dosag on upta of Malachit grn (o:100mg/l;v:50ml;ph:7). All th plots had th sam gnral faturs, an initial curv portion followd by linar portion. Th rat Fig 6. dlich-ptrson plot for sorption of Malachit grn onto watr hyacinth roots (M:0.1g;V:50mL;pH:7;Tmp:30º). constants for intraparticl diffusion ( d ) ar 6

7 Fig 7. Lagrgrn plot for sorption of malachit grn onto watr hyacinth roots (M:0.1g;V:50mL;pH:7.0;Tmp:30º ). raw watr hyacinth roots possss som capacity to upta mg/g at th dy concntration of 100 mg/l. Th optimal ph for bttr sorption of th dy was found to b 7. Th isothrmal data of biosorption fittd vry wll to both dlich Ptrson and Langmuir modls. Th biosorption procss obyd th first ordr adsorption intics. Th ngativ valu of th fr nrgy chang calculatd indicats th spontanous natur of th sorption and confirms th affinity btwn th sorbnt and th dy cations. Thrmodynamic study Thrmodynamic data such as adsorption nrgy can b valuatd from Langmuir uation (Alam, 2004 and Vasanth Kumar t al, 2005). frncs Alam, Biosorption of Basic Dys Using Swag Tratmnt Plant Biosolids, Biotchnology 3, G T ln (13) * ads L * Whr, G ads is th fr nrgy chang (KJ/mol), T is th absolut tmpratur (K), gas constant 8.314(J mol/k) and is univrsal L is th Langmuir constant. Using Langmuir isothrm, th fr nrgy valu was valuatd as KJ/mol. Thrfor adsorption will b most favord on watr hyacinth roots. Alln G, Mcay KY, Knadr H Intra particl diffusion of a basic dy during adsorption onto sphagnum pat, Environmntal pollution 56, Bhatnagar AK, Jain A comparativ adsorption study with diffrnt industrial wasts as adsorbnts for th rmoval of cationic dys from watr, Journal of olloid and Intrfac Scinc 281, Bhattacharyya, Sharma A Kintics and thrmodynamics of Mthyln Blu adsorption on Nm (Azadirachta indica) laf powdr, Dys and Pigmnts 65, Fig. 8. Intraparticl diffusion plot (M:0.1g;V:50mL;pH:7.0;rpm:200;Tmp:30 ). onclusion Th prsnt study shows that th thrmally activatd watr hyacinth root is a potntial adsorbnt for th rmoval of malachit grn from auous solution, sinc th raw matrial is asily availabl in larg uantity. Watr hyacinth roots activatd thrmally at 200º possssd a highr sorption capacity of mg/g confirming that th roots activatd undr ths conditions can b ffctivly usd as biosorbnt. Th Gupta, Mittal A, Krishnan L, Gajb V Adsorption intics and column oprations for th rmoval and rcovry of malachit grn from wastwatr using bottom ash,sparation and Purification Tchnology 40, Low, L K, Tan K Biosorption of basic dys by watr hyacinth roots, Biorsourc Tchnology 52, Low, L K moval of arsnic from Biosorption of basic dys by watr hyacinth roots 7

8 (Eichhornia crassips (Mart) Solms). Ibid 13, Mall V, Srivastava, Agarwal NK, Mishra IM moval of congo rd from auous solution by bagass fly ash and activatd carbon: Kintic study and uilibrium isothrm analyss, hmosphr 61, Vasanth K, amamurthi V, Sivansan S Adsorption of malachit grn, a cationic dy onto Pithophora sp., a frsh watr alga: Euilibrium and intic modling, Procss biochmistry 40, Wang Y, Boyjoo A, houib A comparativ study of dy rmoval using fly ash tratd by diffrnt mthods. hmosphr 60, Waranusantigul P, Pothitiyoo M, Kruatrachu, Upatham ES Kintics of basic dy (mthyln blu) biosorption by giant ducwd (Spirodla polyrrhiza) Environmntal Pollution 125,