COD removal from industrial wastewater using activated carbon prepared from animal horns

Transcription

1 African Journal of Biochnology Vol. 7 (2), pp. 37-3, 5 Novmbr, 2008 Availabl onlin a hp:// ISSN Acadmic Journals Full Lngh Rsarch Papr COD rmoval from indusrial waswar using acivad carbon prpard from animal horns Emmanul O. Aluyor and Olalkan A. M. Badmus Dparmn of Chmical Enginring, Univrsiy of Bnin, Bnin Ciy, Nigria. Accpd 4 Augus, 2008 Th prsn sudy was undrakn o compar h adsorpion fficincy of acivad carbon prpard from animal horns (), which is boh a was and a polluan and a commrcial acivad carbon () wih rspc o upak of h organic componns rsponsibl for h chmical oxygn dmand (COD) of indusrial waswar. Th adsorpion procss was xamind in rms of is uilibria and is kinics. Th ffc of ph, conac im and adsorbn dos wr invsigad. Th mos ffciv ph was found o b 5 for and 6 for. Th uilibrium daa for COD rmoval fid h Linar, Langmuir and h Frundlich modls. Th mchanisms of h ra of adsorpion of COD wr analysd using h psudo-scond-ordr modl. Th modl providd a vry high dgr of corrlaion of h xprimnal adsorpion ra daa suggsing ha his modl could b usd in dsign applicaions. Ky words: Adsorpion, bach, kinics, Langmuir, Frundlich, adsorbn. INTRODUCTION Polluion of war by organic and inorganic chmicals is of srious nvironmnal concrn. Indusrial waswar diffrs in characrisics from h domsic waswar. Indusrial waswars rsul from spills, laks, and produc washing and war rsuling from cooling procsss. Th organic conn of waswar is radiionally masurd using lumpd paramrs such as biological oxygn dmand (BOD), chmical oxygn dmand (COD), oal suspndd solids (TSS) and oal organic carbon (TOC). Ths paramrs as such do no show any chmical idniy of organic mar. In rcn yars, incrasing awarnss of h nvironmnal impac of COD has prompd a dmand for h purificaion of indusrial waswars prior o discharg ino naural wars. This has ld o h inroducion of mor sric lgislaion o conrol war polluion, such as h Environmnal Qualiy (Schduld Wass) Rgulaion 9 in Malaysia (Quk al., 998). This ffc is likly o b vn pronouncd for small and mdium scal indusris whr profi is small and xpris on waswar ramn is unlikly o b availabl. *Corrsponding auhor. oaluyor@yahoo.com. Tl: , A numbr of convnional ramn chnologis hav bn considrd for ramn of waswar conaminad wih organic subsancs. Among hm, adsorpion procss is found o b h mos ffciv mhod. Adsorpion as a waswar ramn procss has arousd considrabl inrs during rcn yars. Commrcial acivad carbon is rgardd as h mos ffciv marial for conrolling h organic load. Howvr, du o is high cos and abou 0-5% loss during rgnraion, unconvnional adsorbns lik fly ash, pa, ligni, bagass pih, wood, saw dus, priwinkl shlls, c. hav aracd h anion of svral invsigaions and adsorpion characrisics hav bn widly invsigad for h rmoval of rfracory marials (Pandy al., 985; Badmus al., 2007; Mall al., 9) for varying dgr of succss. This sudy is aimd a analyzing h adsorpion capaciy of acivad carbon prpard from animal horns on indusrial waswar fflun using a brwing indusry as a cas sudy; and also o dmonsra h us of acivad carbon prpard from animal horns as an alrnaiv mdia ovr convnional acivad carbon. This papr dals wih h rsuls of h bach adsorpion ss o sablish adsorpion isohrms and adsorpion capaciy of h acivad carbon prpard from animal horns () for h rmoval of COD in waswar.

2 38 Afr. J. Biochnol. MATERIALS AND METHODS Th waswar sampl usd was collcd a h poin of discharg from h indusry. Marials usd for sampl collcion wr prrad by washing h conainr wih dilu hydrochloric acid and lar rinsd wih disilld war. Th conainrs wr lar drid in an ovn for h a 0 ± 5 o C and allowd o cool o ambin mpraur. A h collcion poin, conainrs wr rinsd wih sampls hric and hn filld wih sampl, corkd ighly and akn o h laboraory for ramn and analysis. Th mhod of analysis was consisn wih h sandard mhods (APHA, 985; Golrmann, 978). Th ph of h sampl was masurd on h si and ohr paramrs wr masurd in h laboraory. Sampls wr sord a a mpraur blow 3 o C o avoid any chang in physic-chmical characrisics. Th COD of h sampls wr simad bfor and afr adsorpion giving diffrn ramn Adsorpion sudis All h xprimns wr carrid ou a ambin mpraur in bach mod. Bach mod was slcd bcaus of is rlaiv simpliciy. Th bach xprimns wr run in diffrn glass flask of 250 ml capaciy using avrag spd shakr. Prior o ach xprimn, a prdrmind amoun of adsorbn was addd o ach flask. Th sirring was kp consan for ach run hroughou h xprimn nsuring ual mixing. Th dsird ph was mainaind using dilu NaOH/HCl soluions. Each flask was filld wih a known volum of sampl having dsird ph commncd h sirring. Th flask conaining h sampl was wihdrawn from h shakr a h prdrmind im inrval, filrd hrough whamann No. 44 filr papr. Th xprimns wr carrid ou undr diffrn xprimnal condiions. Adsorbn dos Th sudis wr conducd by varying h amoun of adsorbn. 00 ml of waswar sampl was rad wih diffrn doss of prpard priwinkl carbon, g/l. Th sampls wr agiad for 60 min, filrd and hn analyzd. Conac im Ths sudis wr conducd by agiaing 00 ml sampl wih bs adsorbn dos in and agiaing i for diffrn im priod, min. Afr h prdrmind im inrvals, h sampls wr wihdrawn, filrd and analyzd. ph ph ffc was prformd aking a spcific concnraion, adsorbn dos, and conac im and varying h ph valus from - 8 using dilu NaOH/HCl soluions. Th sampls wr agiad for spcific im, filrd and hn analysd. RESULTS AND DISCUSSION Th waswar sampl was characrizd in rms of h paramrs ph, COD and BOD (Tabl ). Effc of adsorbn dos Figur shows h ffc of adsorbn dos on COD r- % Rmoval Tabl. Sampl waswar characrizaion. Paramr Valu ph 8.7 BOD 5 (mg/l) 2.49 COD (mg/l) 6.57 TSS (mg/l) 44 BOD, Biological oxygn dmand; COD, chmical oxygn dmand; TSS, oal suspndd solids Adsorbn dos (g/l). Figur. Effc of adsorbn dos on COD rmoval using acivad carbon prpard from animal horns () and commrcial acivad carbon (). moval. Th rsul shows ha opimum dosag of adsorbns for COD was and 60 g/l of waswar for acivad carbon prpard from animal horns () and commrcial acivad carbon (), rspcivly. Abou.62 and.45% rmoval was achivd for and, rspcivly. Effc of ph Figur 2 dpics h ffc of ph on prcn rmoval of COD. For, a ph 5, h COD rmoval was %, which hn dcrasd as h ph was incrasd. Th sam rnd was obsrvd for. Abou % COD rmoval was achivd for a ph 6. Th rason for h br adsorpion capaciy obsrvd a ph 5 and ph 6 may b aribud o h largr numbr of H+ ions prsn, which in urn nuraliz h ngaivly chargd adsorbn surfac, hrby rducing hindranc o h diffusion of organics a highr ph. A highr ph, h capaciy of h adsorbn rcssd. Th rducion in adsorpion may b possibl du o h abundanc of OH -

3 Aluyor and Badmus % Rmoval 9 % Rmoval ph Figur 2. Effc of ph on COD rmoval acivad carbon prpard from animal horns () and commrcial acivad carbon (). ions, causing incrasd hindranc o diffusion of organics conribuing o COD) ions. Similar obsrvaions hav also bn rpord by h workrs (Mohan and Karhikyan, 997; Liskowiz al., 980; Mo and Wbr, 9; Pandy al., 985). Effc of conac im Th rsul obaind shows ha h mixing im had grar impac on COD rmoval (Figur 3). A an opimum im of 50 min, abou.67% COD rmoval was achivd for, whil abou 96. 4% COD rmoval was achivd for a 80 min. Th smooh and indpndn naur of curv indicas formaion of monolayr covr of h adsorba on h our surfac of h adsorbns. Adsorpion isohrms Two imporan physiochmical aspcs for h valuaion of h adsorpion procss as a uni opraion ar uilibria of h adsorpion and h kinics. Euilibrium sudis giv h capaciy of h adsorbn. Th uilibrium rlaionships bwn adsorbn and adsorba ar dscribd by adsorpion isohrms, usually h raio bwn h uaniy adsorbd and ha rmaining in soluion a a fixd mpraur a uilibrium. Th uaions for h hr yps of adsorpion isohrms ar xprssd by: Linar isohrm Langmuir isohrm x = = k pc () m C C = + (2) k o o Conac im (min.) Figur 3. Effc of conac on COD rmoval acivad carbon prpard from animal horns () and commrcial acivad carbon (). Whr C is h uilibrium concnraion of COD in war sampl (mg/l), x/m is h amoun of COD adsorbd pr uni of adsorbn (mg/g), o is a consan rlad o h ara occupid by a monolayr of adsorba, hus rflcing h adsorpion capaciy (mg/g), k is a dirc masur of h innsiy of h adsorpion procss, nrgy of adsorpion (l/mg). x Frundlich isohrm log = log k + m n logc Whr k is h uaniy of COD adsorbd in mg/g adsorbn for a uni uilibrium concnraion of h sampl, ha is, C = and /n is a masur of h adsorpion innsiy. For n =, h pariion bwn h wo phass is indpndn of h concnraion. In his cas, k k p (linar isohrm). A valu of /n < shows a normal Langmuir isohrm, whil /n > is indicaiv of a coopraiv adsorpion (Akins, 970; Mohan and Karhikyan, 997; Badmus, al., 2007). In ordr o dcid which yp of isohrm fis br h adsorpion xprimnal daa, a plo of x/m vs C was mad for h linar isohrm (Figur 4); C/ vs C was mad for h Langmuir isohrm (Figur 5) and log (x/m) vs log C for h Frundlich isohrm (Figur 6). Th r 2 valus (goodnss fi cririon) wr compud using linar rgrssion for h hr yps of isohrms. Th rsuls obaind show ha h hr yps of adsorpion isohrms ar bs suid for adsorpion of COD. Th cofficins of drminaion (r 2 ) and h isohrm consans ar givn in Tabl 2. Th high valus of r suard (> %) for h hr isohrms indica ha h adsorpion of COD could b wll dscribd by h Linar, Langmuir and Frundlich isohrms. (3)

4 38 Afr. J. Biochnol. Tabl 2. Adsorpion isohrm consans and cofficin of drminaion for diffrn adsorbns. Langmuir isohrm consans Frundlich isohrm consans Adsorbn o (mg/g) k (l/mg) r 2 k (mg/g) /n r x/m (mg/g) LOG(x/m) C (mg/l) Figur 4. Adsorpion isohrm of COD on acivad carbon prpard from animal horns () and commrcial acivad carbon () LOGC Figur 6. Comparison of Frundlich isohrms of acivad carbon prpard from animal horns () and commrcial acivad carbon (). 4 C/ C (mg/l) Figur 5. Comparison of Langmuir isohrms of acivad carbon prpard from animal horns () and commrcial acivad carbon (). Adsorpion kinics Th sudy of h adsorpion kinics is h main facor for dsigning an appropria adsorpion sysm and uanifying h changs in adsorpion wih im ruirs ha an appropria kinic modl is usd. In ordr o considr h kinics ffcs, h following Lagrgrn psudo-firs ordr uaion can b usd o drmin h ra consans (Mohan al., 2002; Badmus al., 2007). log K, ad ( ) = log ( ) (4) Whr is h amoun of COD adsorbd a uilibrium (mg/g); is h amoun of COD adsorbd a im (mg/g); K,ad is h psudo-firs ordr ra consan (min - ); and is h im (min). In many cass, h Euaion 4 can no b usd o dscrib h kinics of h adsorpion procss. In such cass, a psudo-scond ordr xprssion may b usd and his is mor appropria for dscribing his yp of adsorpion. Hnc, his modl rducs o: K 2, ad 2 + ( ) = (5) Whr K 2,ad is h psudo scond ordr ra consan (gmg - min - ). In his sudy, scond ordr kinics modl was considrd for h adsorpion procss of COD. Figur 7 shows h linarisd form of h psudo-scond ordr modl for h adsorpion of COD ono and. Th corrlaion cofficins, R 2, and h psudo-scond ordr ra paramrs ar shown in Tabl 3. Th agrmn bwn h ss of daa rflcs h xrm high corrlaion cofficin obaind and shown

5 Aluyor and Badmus 3 Tabl 3. Psudo-scond ordr paramrs and cofficin of drminaion for diffrn adsorbns. Psudo-scond ordr uaion Adsorbn k r / (min.g/mg) Tim (min.) Figur 7. Psudo-scond ordr adsorpion kinics of COD on acivad carbon prpard from animal horns () and commrcial acivad carbon (). in Tabl 3. In ordr words, h daa also show good complianc wih h proposd psudo-scond ordr uaion. Indd, h rgrssion cofficins for h linar plos wr highr han for boh sysms in hs sudis. Du o h corrlaion of h xprimnal rsuls wih h psudo-scond ordr modl, h main adsorpion mchanism is probably a chmisorpion racion. REFERENCES Amrican Public Halh Associaion (APHA) (985). Sandard Mhods for Examinaion of Waswar, 7 h Ed., Nw York. Akins P (970). Physical Chmisry, Oxford Univrsiy Prss, Oxford, UK. Badmus MAO, Audu TOK, Anyaa BU (2007). Rmoval of Coppr from Indusrial Waswars by Acivad Carbon Prpard from Priwinkl Shlls. Koran J. Chm. Eng. 24: Golrmann HL (978). Mhod for Physical and Chmical Analysis of Frsh War, Wll scinific publicaions, 2 nd Ed., Black wll Scinific Publicaions. Liskowiz JW, Chan PC, Tranr R, Shih M (980). Proc. of Naional confrnc on hazardous and oxic was managmn, Nw Jrsy 2: Mall ID, Mishra N, Mishra IM (9). Rmoval of organic mars from sugar mill fflun using bagass fly ash acivad carbon. Rs. Ind. 39: 5-9. Mohan S, Karhikyan J (997). Rmoval of lignin and annin colour from auous soluion by adsorpion ono acivad charcoal. Environ. Pollu. 97: Mohan SV, Rao NC, Karhikyan J (2002). Adsorpiv appl pomac and wha sraw. War Rs., 36: Mo HV, Wbr WJ (9). Sorpion of low molcular wigh organic conaminans by fly ash: considraion for h nhancmn of cuoff barrir prformanc. Environ. Sci. Tchnol. 26: Pandy KK, Prasad G, Singh VN (985). Coppr rmoval from auous soluions by fly ash. War Rs. 9: Quk SY, Was DAJ, Forsr CF (998). Th us of sago was for h sorpion of lad and coppr. War SA 24(3): Conclusion Th following conclusions wr drawn from h prsn sudy. Acivad animal horn carbon compd favourably wih commrcial acivad carbon. Th rsuls obaind showd ha can b usd in h rmoval of COD from indusrial waswars. Trnd of COD rmoval by,.67%, is comparabl o ha of wih 96.34% fficincy. Ths rsuls show ha granular acivad carbons mad from agriculural was (animal horn) can b usd wih grar ffcivnss for organic mar rmoval from indusrial waswar. This would b of bnfi no only o h manufacuring indusry in rms of minimising cos of COD ramn, bu also o minimis h impac on h nvironmn. Th adsorpion daa followd boh Langmuir and Frundlich isohrms. In addiion, a psudo-scond ordr kinics appars o modl h ra of adsorpion.