Environmental Science An Indian Journal

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1 Novmbr 6 Volum Issus 4-6 Trad Inc. Currnt nt Rsarch Papr ESAIJ, (4-6), 6 [87-9] Adsorption f Dirct Rd From Aquous Solution Using Ric Husk Activatd By Citric Acid Corrsponding Author Ahmd El Nmr Dpartmnt of Pollution, Division, National Institut of canography and Fishris, Kayt Bay, El-Anfushy, Alxandria, (EGYPT ) Tl./Fax: ahmdmoustafalnmr@yahoo.com Rcivd: th April, 6 Accptd: th July, 6 Wb Publication Dat : 4 th Novmbr, 6 Co-Authors Azza Khald, la Abdlwahab, Amany El Sikaily Dpartmnt of Pollution, Division, National Institut of canography and Fishris, Kayt Bay, El-Anfushy, Alxandria (EGYPT) ABSTRACT Th goal of this rsarch is to dvlop a nw and fficint adsorbnt of dirct dys. Thus, ric husk, a commonly availabl agricultur wast in Egypt, was invstigatd as viabl matrials for tratmnt of synthtic Dirct Rd containing industrial wastwatr. Activation of ric husk with citric acid was studid in ordr to incras its capacity to rmov th dy. Th rsults obtaind from th batch xprimnts rvald th ability of th ric husk in rmoving th Dirct Rd and ar dpndnt on th dy and ric husk concntrations. Kintics of adsorption was invstigatd as wll as quilibrium isothrm of Dirct Rd using angmuir modl, which rprsntd a corrlation cofficint >.96. Th maximum adsorption capacity was g of dy pr kilogram of dry ric husk. This study showd that th ric husk could b mployd as low-cost for th rmoval of Dirct Rd from aquous solution. 6 Trad Inc. - INDIA KEYWRDS Adsorption; Ric husk; Dirct Rd-; Isothrms; Kintics; angmuir modl. INTRDUCTIN Efflunt from dying and finishing procsss is an important sourc of watr pollution. Th rlas of th colord dys into th cosystm is a dramatic sourc of pollution, of utrophication, and of pr- turbations in aquatic lif. Som azo dys and thir dgradation products such as aromatic amins ar highly carcinognic. Propr tratmnt of th dy plant fflunt is thus, a mattr of concrn bfor discharg. Diffrnt tratmnt mthods ar dscribd in th litratur, including filtration, flocculation,

2 88 Adsorption of. Dirct Rd ESAIJ, (4-6) Novmbr 6 chmical prcipitation, ion xchang, mmbran sparation, and adsorption [,]. Nw approachs basd on th us of natural, inxpnsiv sorbnt matrials for fflunt tratmnt hav also bn rportd [-7]. Th adsorption procss is on of th fficint mthods to rmov contaminant from fflunt [6,8]. Th procss of adsorption has an dg ovr th othr mthods du to its sludg fr clan opration and complt rmoval of dy vn from dilut solutions. Activatd carbon is th most widly usd adsorbnt bcaus of its xtndd surfac ara, microporous structur, high adsorption capacity and high dgr of surfac ractivity. Howvr, commrcially availabl activatd carbons ar xpnsiv and its manufacturing problms such as combustion at high tmpratur por blocking, and hydroscopicity. Ric husk, an agricultur mass rsidu, is a byproduct of th ric milling industry. It rprsnts about % of th whol ric producd, on wight basis [9]. Traditionally, ric husks hav bn usd in manufacturing block mployd in civil construction as panls and was usd by ric industry itslf as a sourc of nrgy for boilrs. It was chosn for an adsorption rsarch bcaus of its granular structur, chmical stability and low production costs. Th main constitunts of ric husk ar: 64.% volatil mattr and 5.9% fixd carbon and 9.8% ash [9]. Th ric husk composition is: % cllulos, % hmicllulos, % lignin,.8% xtractivs, 8% watr and 5% minral ash []. Howvr, th rportd composition of ric husk diffrs widly, as affctd by paddy typ and climat []. Th purpos of this work is to invstigat th adsorption capacity of th untratd and activatd ric husk on adsorption of dirct dys from aquous solution. Dirct Rd (DR-) dy was slctd for th adsorption xprimnt du to its prsnc in svral industrial fflunts such as txtil, tannry, papr, soap, cosmtics, polishs, wax tc. DR- is toxic and carcinognic and its biodgradation may lad to primary amins. MATERIAS AND METHDS Ric husk was obtaind from local ric mills and was washd svral tims with distilld watr followd by filtration. Th washd ric husk was ovn drid at 5 C for 4 hrs, thn coold and sivd to 5-5 µm siz, and usd without furthr tratmnt. Anothr part of sam siz fraction of ric husk was xposd citric acid-activation [], which g of ric husk wr soakd in.6m citric acid and allowd to ract for h at C. It was drid at 5 C, followd by hating to C, washd rpatdly with distilld watr to rmov xcss of th acid and thn ovn drid at C for 48 hrs. Dirct Rd- was obtaind from ASMA Company and was usd without furthr purification. Its molcular formula is C 5 H 5 N 7 Na S and its color indx C.I. 96 (Figur ). A stock solution of DR- was prpard by dissolving. g of dy in m distilld watr to mak a stock solution of mg - concntration []. Th xprimntal solutions wr prpard by diluting th stock solution with distilld watr to gt th dsird concntration. UV- VIS spctrophotomtr (Milton Roy, Spctronic D) was mployd for adsorbanc masurmnts using silica clls of path lngth cm. Th maximum wavlngth λ max for th DR- was dtrmind at 57 nm. Chang in ph ( to 7) of DR- solution has no ffct on its color concntration. Concntrations during xprimntal work wr dtrmind from calibration curv. Equilibrium adsorption isothrms for th untratd and activatd ric husk wr dtrmind by doing th xprimnts at agitation rat of 5 rpm at room tmpratur and at diffrnt concntrations of dy and ric husk. Adsorbnt (.5-. g) was addd in a st of 5-ml Erlnmyr flasks and ml at various initial dy concntrations (5,, 5,, 5 mg l - ). Th contnts wr shakn for appropriat tim and th suprnatant was analyzd for dy contnts using UV-VIS spctrophotomtr [Concntration = 8.4 Absorption (SD = ±.~.) obtaind from standard curv]. Th adsorption bhaviors of th sampls wr studid by valuating th rmoval fficincy of DR-, in trms of prcntag from th rlation Rmoval fficincy C C = C () Whr C is th initial concntration of DR-

3 ESAIJ, (4-6) Novmbr 6 Ahmd El Nmr t al. 89 H N CH N H H N N N Na S N N S H H Na Figur : Structur of Dirct F.scarlt (Dirct Rd or Dirct F.orang) and C is th solution concntration aftr adsorption. Effct of tim on th dy rmoval at various prdtrmind intrvals was monitord by analyzd th solution for th dy contnt at th nd of ach contact tim. Kintics of adsorption was dtrmind by analyzing adsorptiv uptak of th dy color from aquous solution at diffrnt tim intrvals. Th amount of dy adsorbd onto th ric husk q (mg l - ) was calculatd according to th following mass balanc quation q (C C ) V = () w Whr C o and C ar th initial and quilibrium concntrations of dy, rspctivly (mg l - ), V is th solution volum (l), and W is th wight (g) of th ric husk usd. RESUTS AND DISCUSSIN Ct, mg/l Figur : Influnc of contact tim and wight of untratd ric husk on rmoval of DR- using dy concntration of mg - Ct, mg/l g/l 5. g/l. g/l Tim, min.5 g/l 5. g/l. g/l Tim, min Figur : Influnc of contact tim and wight of activatd ric husk on rmoval of DR- using dy concntration of mg - Th adsorption of DR- on ric husk and citric acid tratd ric husk wr studid for its possibl importanc in th rmdiation of industrial fflunts. Th ffct of agitation tim, sorbnt and dy concntrations on rmoval of DR- wr studid and rprsntd in figurs and. Th prcntag of rmoval was incrasd with incras of th contact tim and biomass concntration and bcom narly constant aftr rading quilibrium. As shown in figurs and, th rat of rmoval of colour was rapid at first min and attaind narly constant valu byond which thr was no significant incras in color rmoval. Th tim rquird to attain quilibrium was minuts for untratd and 9 minuts for activatd ric husk. Th curvs dpicting rmoval ar singl, smooth and continuous lading to saturation. Howvr, th dy color rmoval pattrn showd that incras in th biomass concntration indicatd incras dy rmoval capacity, which may b attributd to th incras of biomass of ric husk givs mor surfac ara for adsorption of th dy molcul

4 9 Adsorption of. Dirct Rd ESAIJ, (4-6) Novmbr 6 TABE : angmuir constants for th adsorption of DR- using untratd and modifid ric husk Adsorbnt R (mg g - ) ( mg - ) r- valu Untratd ric husk.4.7 < R <.99 Activatd ric husk < R <.97 on th surfac (Figurs and ) [8]. Th incrmntal incras of % was obsrvd for incras of biomass from.5 to 5. g l - and anothr % for incras of biomass from 5. to. g - for untratd ric husk. Whil for citric acid tratd ric husk, an incrmntal incras of % was obsrvd for vry.5 g l - incras of biomass. It can also follow from th abov discussion that th ric husk biomass uptak was dpndnt on th dy concntration and ric husk biomass. Adsorption data wr analyzd according to angmuir modl for both untratd and citric acid tratd ric husk. Th angmuir modl was originally formulatd basd on thortical assumptions: () th adsorption raction can b rprsntd as a coordination raction with : stoichiomtry (i.. monolayr adsorption); () th activitis of th surfac sits ar proportional to thir concntration and () th numbr of adsorption sits is fixd [4-6]. It is basd on th physical hypothsis that th maximum adsorption capacity consists of a monolayr adsorption. It is assumd that onc a dy molcul occupis a sit, no furthr adsorption can tak plac at that sit [7]. Thortically, a saturation valu is rachd byond which no furthr adsorption can occur. Th angmuir quation, which has bn succssfully applid to many adsorption systms [6,8], is givn by (K Sm C ) q = ( + K C ) () Whr K is th quilibrium adsorption cofficint (l mg - ), S m is th maximum adsorption capacity (mg g ), C th adsorbat quilibrium concntration. Eq. () can b writtn in th following linar form C q C = + (K S ) S (4) m S m m Th dy adsorption data wr plottd according to linar angmuir isothrms. A linarizd plot of C /q vrsus C was obtaind for th untratd and K C/q C (mg/) Figur 4: Fitting adsorption data with angmuir using sorbnt concntration of g - activatd ric husk as shown in figur 4. Rgrssion data and adsorption paramtrs obtaind ar indicatd in TABE. n advantag of th angmuir quation in its linar form is that th adsorption maximum can b calculatd from th rgrssion. Th data for adsorption of DR- onto untratd and citric acid tratd ric husk wr fittd to th angmuir modl (r=.99 and.97, rspctivly). Th fitnss of th angmuir modl for this adsorption systm indicats th monolayr covrag of dy on th outr surfac of biosorbnt, in which th adsorption of dy molcul occurs uniformly on th activ part of th surfac. Th fits ar quit wll for both sorbnts, which suggstd th applicability of th angmuir modl for th invstigatd systm. S m and K, angmuir constants, ar th masurs of maximum adsorption capacity and nrgy of adsorption, rspctivly. Th valus of angmuir paramtrs along with th corrlation cofficints wr computd from th intrcpt and th slop of th fittd angmuir quation. Activatd ric husk is obsrvd to hav highr adsorption capacity than th untratd ric husk in th rmoval of DR-. Th ssntial charactristic of angmuir isothrm can b xprssd in trms of a dimnsionlss constant, R, which is dfind as follows [6,9,] : R activatd ric husk = [ + (K C )] (5) Untratd ric husk Whr C is th initial concntration and R indicats th shap of th isothrm. Th typs of qui-

5 ESAIJ, (4-6) Novmbr 6 Ahmd El Nmr t al. 9 log(q-q) Tim (min) Figur 5: agrgrn plots for th rmoval of DR- by adsorption on untratd ric husk and sorbnt concntration of 5g - librium isothrm ar rlatd with th R valus as R > for unfavorabl, R = for linar, < R > for favorabl and R < for irrvrsibl. In this work, th valus of R wr found to b lss than and gratr than zro indicating th favorabl adsorption of DR- on ric husk. Th kintics of adsorption of DR-, on both untratd and activatd ric husk, was studid by applying th agrgrn first ordr rat quation [-4] as follows: og(q 5 mg/ mg/ 5 mg/ mg/ 5 mg/ K q) = ogq t (6). Whr q (mg g - ) is th amount of dy adsorbd at tim t, q (mg g - ) is th amount of dy adsorbd at quilibrium, and K is th quilibrium rat constant of adsorption. Th straight lin plots of log (q log(q-q).4 5 mg/ mg/ 5 mg/ mg/. 5 mg/ Tim (min) Figur 6: agrgrn plots for th rmoval of DR- by adsorption on activatd ric husk and adsorbnt concntration of 5g - q) vrsus t for dy at diffrnt biomasss undr usd conditions indicat th validity of Eq. 6 and th procss follows first ordr kintics (Figurs 5 and 6). Rat constants wr calculatd from th slop of th straight-lin curvs. In batch stirring ractors, th transport of adsorbat from bulk solution to th intrior surfac of th pors is oftn th rat limiting stp of th adsorption procss [5,6]. Th rat paramtrs controlling intra-particl diffusion for DR- with both typs of adsorbnts ar dtrmind using th following quation [8,7] : q t = K p t.5 (7) Whr q t (mg g - ) is th amount of dy adsorbd at tim t; and K p is th intra-particl diffusion rat constant (mg g - min.5 ). Plotting th amount sorbd pr unit wight of sorbnt (q t ) vrsus t.5 as dscribd.5 5 mg/ 5 mg/ mg/.5 5 mg/ 5 mg/ mg/.5.5 qt qt t.5 Figur 7: Intra-particl diffusion plots for th rmoval of DR- using untratd ric husk t.5 Figur 8: Intra-particl diffusion for th rmoval of DR- on citric acid tratd ric husk

6 9 Adsorption of. Dirct Rd ESAIJ, (4-6) Novmbr 6 by Eq. (7), indicats th intra-particl diffusion rat, K p, valus, which wr obtaind from th slops of th linar plots for ach initial concntration for both typs of adsorbnts. Intra-particl diffusion plots ar shown in figurs 7 and 8. It was found that th plots of diffrnt dy concntrations wr linar and pass through th origin for both untratd and citric acid tratd ric husk, which indicats that th rat dtrmining stp may b controlld by intra-particl diffusion. Th rsults obtaind from th prsnt invstigation rvald th ability of ric husk in trating azo dy fflunts. Adsorption is highly dpndnt on th contact tim, dy concntration and adsorbnt dos. Th angmuir isothrm modl dscribs th adsorption isothrm of DR- onto ric husk biomass. Kintics of adsorption follows agrgrn first ordr kintic modl with film diffusion bing th constitutiv rat-controlling stp. Th monolayr adsorption capacity obtaind from angmuir isothrms for DR- was found to b rlativly highr for th citric acid tratd ric husk in comparison to th ons obtaind without chmical tratmnt. Th rsults obtaind using ric husk wr comparabl to that obtaind using orang pl adsorbnt for rmoval of DR- from aquous solution [8]. Howvr, it can b said that, ric husk is vry chap biomass, mor abundant than orang pl and can b usd as potntial biosorbnt in rmoval of DR- from aquous solution. CNCUSIN Th data from batch studis on th adsorption of DR- on citric acid activatd ric husk providd fundamntal information in trms of mass of sorbnt and DR- initial concntration. This study indicatd that th uptak of DR- was gratly affctd by th initial dy concntration and mass of adsorbnt matrial. angmuir modls fit th isothrm data wll for both untratd and tratd ric husk. Th data obtaind may b hlpful for dsigning and stablishing a continuous tratmnt plant for watr and wast watr nrichd in DR-. Th cost of rmoval is xpctd to b quit low, as th adsorbnt is chap and asily availabl in larg quantitis. REFERENCES [] C.R.T.Tixira, M.A.Z.Arruda; Chmosphr, 54(), , rfrnc citd thrin (4). [] M.M.Mohamd; Journal Colloidal Intrfac and, 7, 8-4, rfrnc citd thrin (4). [] W.Wafwoyo, C.W.So, W.E.Marshall; Journal Chmistry Tchnology and Biotchnology, 74, 7- (999). [4] V.Dushnkov, P.B.A.N.Kumar, H.Motto, I.Raskin; and Tchnology, 9, 9-45 (995). [5] T.Vaughan, C.W.So, W.E.Marshall; Biorsourc Tchnology, 78, -9 (). [6] P.K.Malik; Dys and Pigmnts, 56, 9-49 (). [7] S.Vnkata Mohan, Y.Vijay Bhaskar, J.Karthikyan; Int. J.of Environmnt and Pollution, - (). [8] D.Mohan, K.P.Singh, S.Sinha, D.Gosh; Carbon, 4, 49-4 (). [9] A.A.M.Daifullah, B.S.Girgis, H.M.H.Gad; Matrial ttr, 57(), 7-7 (). [] W.Nakbanpot, P.Thiravtyan, C.Kalambahti; Minrals Enginring,, 9-4, rfrnc citd thrin (). [] N.M.H.Govindararo; Journal Industrial Rsarch, 9, (98). [] W.E.Marshall,.H.Wartll; Industrial Crops and Product, 8, 77-8 (). [].Abdlwahab, A.El Nmr, A.El Sikaily, A.Khald; Intrnational Confrnc on Aquatic Rsourcs of th Arab Rgion, 7-9 th May 5, Shraton El Montazah, Alxandria, EGYPT. [4] I.angmuir; Journal of th Amrican Chmical Socity, 4(9), 6-4 (98). [5] F.M.M.Morl, J.G.Hring; Principls and Applications of Aquatic Chmistry, Nw York, Wily, (99). [6] Y.S.Ho, C.T.Huang, H.W.Huang; Procss Biochmistry, 7(), 4-4 (). [7] M.M.Broholm, K.B.Erik Arvin; Journal Contamination Hydrology, 9, 8- (999). [8] P.Waranusantigul, P.Pokthitiyook, M.Kruatrachu, E. S.Upatham; Pollution,, 85-9 (). [9] S.M.Mohan, N.C.Rao, K.K.Prasad, J.Karthikyan; Wast Managmnt,, (). [] K.R.Hall,.C.Eaglton, A.Acrivos, T.Vrmuln; Industrial and Enginring Chmistry Fundamntals, 5(), - (966). [] C.K., K.S.ow, S.W.Chow; Tch-

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