KKU Engineering Journal

Transcription

1 KKU ENGINEERING JOURNAL July Sptmbr 2015;42(3): Rsarch Articl KKU Enginring Journal Rmoval of grn 40 from aquous solutions by adsorption using organo-corn straw Chakkrit Umpuch* Dpartmnt of Chmical Enginring, Faculty of Enginring, Ubon Ratchathani Univrsity, Ubon Ratchathani 34190, Thailand. Rcivd Fbruary 2015 Accptd April 2015 Abstract Th objctiv of this study was to invstigat th adsorption charactristics of grn 40 on organo-corn straw which was prpard by mans of adsolubilization in batch tsts and fixd bd column xprimnts. Th batch tsts wr studid as functions of contact tims (t), initial ph solutions (ph0), and initial dy concntrations (C). Th adsorption rachd quilibrium within 5 h and th amount of th dy adsorbd dcrasd with incrass in ph0. Th adsorption isothrm followd Langmuir and Frundlich isothrms and th kintic data obyd th psudo-scond ordr kintic modl. Th fixd bd xprimnts wr carrid out as functions of inlt dy concntrations, liquid flow rats, and bd hights. Th brakthrough point appard fastr with incrass in liquid flow rats and inlt dy concntrations, but prsntd mor slowly with incrass in bd hights. It was found that th highst adsorption capacity of mg/g was obtaind undr th condition of inlt dy concntration of 200 mg/l, bd hight of 16 cm, and flow rat of 3.5 ml/min. Th adsorption data wr fittd to thr wll-stablishd fixdbd adsorption modls, Adams-Bohart, Thomas, and Yoon-Nlson modls with good cofficints. Th rsults showd that organo-corn straw can b usd as an ffctiv biosorbnt for th rmoval of grn 40 from wastwatr. Kywords : Grn 40, Adsolubilization, Organo-corn straw, Adsorption, Batch tsts, Fixd-bd column 1. Introduction Local fabric products such as hand-wovn silk and handwovn cotton producd in many rural aras in Thailand hav rcivd attntion from many customrs around th world. Villagrs arn incom in addition to that from thir agricultural activitis from th sal of thir fabric products. According to high product dmand, villagrs group thmslvs into houshold-scal txtil industris to incras thir production capacitis. Thr ar ovr a hundrd txtil industris at th houshold scal in Ubon Ratchathani provinc. Dying th fabric is an important stp to mak it attractiv. Organic dys ar normally usd du to thir bright colors, xcllnt color fastnss, and as of application [1]. Ths dys ar highly solubl in watr and do not biodgrad wll in natural stram conditions bcaus of thir high rsistanc to hat, light, and structural complx. Accumulation of organic dys in natur causs a rduction of th pntration of light into th watr body, rsulting in pollutd watr which is unsightly and strong smlling. Furthrmor, many organic dys ar contaminatd with toxic havy mtals and may caus dirct harm to humans and organisms via natural strams. Tratmnt of colord fflunt is difficult by convntional physical, chmical, and biological tratmnt mthods [2]. Tratmnt that is chap, fficint, and simpl is what is rquird. Biosorption is an mrging tchniqu for watr tratmnt that involvs th binding of contaminants on th surfac with asily availabl biomatrials. Th capacity of biosorbnts can b nhancd by various tratmnts [3-4]. Adsolubilization tchnology, which is a procss to form admicll of surfactant on th xtrnal surfac of adsorbnt for altring surfac proprtis from hydrophilic to organophilic, has bn provn to b ffctiv [3]. As biosorption mainly taks plac on th biomass surfac, surfactant adsolubilizd on th biosorbnt surfac is an ffctiv approach for nhancing th biosorption capacity to organic molculs including organic dys [5]. Grn 40 is an organic dy manufacturd in Thailand and its major constitunts ar carbon and hydrogn which ar vry chap and availabl in many local markts nar Ubon Ratchathani Univrsity. It is on of th most usd organic dys in th dying procss in this rgion. This rsarch usd corn straw in th prparation of organo-corn straw by mans of adsolubilization. Corn is on of th major agricultural products in Thailand and thr is a plntiful, inxpnsiv, and rnwabl supply of its straw lft in th filds aftr th harvsting sason ach yar. Batch adsorption tsts ar usually carrid out to invstigat adsorption capacity and adsorption bhavior of organic dys on th modifid biosorbnt. Factors affcting biosorption includ contact tims, initial ph solutions, and initial dy concntrations. In practical uss, immobilization of th cationic surfactant on a supporting or immobilizing matrial is also tstd to rmov dys from fflunts [6]. Th immobilization systms provid advantags ovr fr-form biosorbnts. Ths includ as of rgnration and rus of th biomass, asir solid-liquid sparation, and minimal *Corrsponding author. Tl.: ; fax: addrss: chakkrit.u@ubu.ac.th doi: /kkunj

2 251 KKU ENGINEERING JOURNAL July Sptmbr 2015;42(3) clogging of continuous flow systms [7]. Batch adsorption takn placs in a closd systm containing a dsird amount of adsorbnt contacting with a crtain volum of adsorbat solution, whil dynamic adsorption usually occurs in an opn systm whr adsorbat solution continuously passs through a column packd with adsorbnt. For column adsorption, th brakthrough curv is a vry important bcaus it provids prdominant information for th dsign of a column adsorption systm for practical application [8]. Factors affcting adsorption in fixd-bd column includ initial dy concntrations, bd hights and fd flow rats [9]. Th objctiv of this rsarch was to study th biosorption potntial of organo-corn straw in batch tsts and fixd bd columns. In th batch tsts, biosorption was invstigatd as functions of contact tims, initial ph solutions, and initial dy concntrations and adsorption isothrm and kintic modls wr also conductd for data corrlation. In th fixd bd xprimnts, th important dsign paramtrs such as inlt concntrations of grn 40 solutions, flow rats of fluid, and column bd hights wr invstigatd. Th brakthrough charactristics of th biosorption of grn 40 on th organo-corn straw wr analyzd using Adams-Bohart, Thomas, and Yoon-Nlson modls. 2. Matrial and mthods 2.1. Dy solutions Th organic dy, grn 40 was purchasd from a local markt nar Ubon Ratchathani Univrsity [10]. Th IRspctra of grn 40 dy showd that th dy contains two catgoris of activ functional groups which ar carboxyl and hydroxyl groups which ar hydrophilic part and long chain alkyl group which is hydrophobic part which has bn rportd in prvious study [11]. Th dy stock solution was prpard by dissolving accuratly wighd grn 40 in distilld watr to obtain 1 g/l of th dy solution. Th dy solutions studid wr prpard by dilution of th dy stock solution in accurat proportions to th dsird initial concntrations Prparation of organo-corn straw Raw corn straw which was also purchasd from a local markt nar Ubon Ratchathani Univrsity was prpard by washing with distilld watr svral tims to rmov dust and othr impuritis. It was thn drid at a tmpratur of 40 C in an air circulating ovn until its wight was constant. Th corn straw was crushd and shrddd in a blndr for about 15 min and sivd (50 msh) to obtain a particl siz blow 297 µm [12]. Th organo-corn straw was prpard by trating 1.0 g of th corn straw with 100 ml of 1000 mg/l ttradcyltrimthyl ammonium bromid surfactant (C17H38NBr) purchasd from th Mrck Chmical Company (Grmany). Th cationic surfactant structur was shown in Figur 1. Mixing took plac at 200 rpm for 15 min at room tmpratur using an orbital shakr. Aftrwards, th organocorn straw particls wr filtratd with GF80 filtr (Whatman, UK), washd with distilld watr svral tims to rmov suprficially rtaind surfactant, and drid in an ovn at 40 C until th wight was constant (approximatly 48 hr). To obtain mor rproducibl data, th organo-corn straw particls wr sivd (50 msh) bfor its us for th adsorption studis. Furthrmor, all adsorbnts wr packd in plastic bags and stord in dsiccators for furthr us. Figur 1 TMDA-Br structur 2.3. Batch tsts Sinc th prcntags of grn 40 rmoval of th corn straw and th organo-corn straw wr 25.62% and 95.61%, rspctivly, which wr obtaind undr a condition: 100 ml of solution volum, 200 mg/l dy solution, 0.1 g of adsorbnt, 200 rpm agitation spd, and 24 hr shaking duration. Thus, only th organo-corn straw was usd as biosorbnt for furthr xprimnts. Batch adsorption tsts wr conductd as functions of contact tims, initial ph solutions, and initial dy concntrations. First, to invstigat th ffct of contact tims, a sris of 250 ml Erlnmyr flasks containing 100 ml of 200 mg/l dy solution was mixd with 0.1 g of th organo-corn straw. Ths flasks wr pluggd with parafilm to avoid vaporation and thn horizontally shakn at 200 rpm. Th sampls wr masurd at intrvals btwn 5 and 360 min. Scond, to invstigat th ffct of initial ph solutions, 100 ml of 200 mg/l dy solution was mixd with 0.1 g of th organo-corn straw and placd in a 200 ml Erlnmyr flask. Th initial ph solution was adjustd btwn 2.0 and 10.0 by 0.01N NaOH and/or 0.01N HCl and thn horizontally shakn at 200 rpm for 24 hours. Finally, to invstigat th ffct of initial dy concntrations, 0.1 g of th organo-corn straw was loadd into 100 ml of 50 to 250 mg/l initial dy solution and thn horizontally shakn at 200 rpm for 24 hours to achiv quilibration (quilibrium tim was obtaind from th study of contact tim). All sampls wr masurd in th quilibrium condition. Th dy concntration of all sampls was analyzd by using UV-Vis-Spctrophotomtr at a maximum absorbanc wav lngth of 409 nm. Th xprimnts wr carrid out at a tmpratur of 25±1 C without ph adjustmnt Fixd bd column xprimnts Exprimnts in fixd bd columns (Figur 2) wr thn compltd as functions of initial dy concntrations, flow rats, and bd hights. Fixd bd columns wr prpard by insrting glass wool in an nd of a glass column (1.2 cm innr diamtr and 40 cm hight) until 10 cm of glass wool hight was obtaind and thn organo-corn straw was loadd into th othr nd of th glass column. Th factors affcting includ initial dy concntration ( mg/l), flow rat (1.4-7 ml/min) and bd hight (8-24 cm) ar invstigatd. First of all, distillatd watr was pumpd into th column by a diaphragm pump to masur th watr prmability and thn th dy solutions wr fd into th column. Th sampls from th fflunts from th columns wr masurd vry 5 min until th fflunts rachd 90% of th initial dy concntration. Brakthrough charactristics and man liquid flow rats wr intrprtd from th xprimntal data. Th brakthrough tim (tb), brakthrough volum (Vb), and th shap of th brakthrough curv ar vry important charactristics for dtrmining th opration and th dynamic rspons of biosorption in th fixd bd columns. Th brakthrough curv shows th shap of mass transfr

3 KKU ENGINEERING JOURNAL July Sptmbr 2015;42(3) 252 Pump Adsorbnt rat in th latr stag can b xplaind as th dy molculs bing diffusd into th intrior of th admicll covring on th adsorbnt surfac. To nsur quilibrium, furthr xprimnts in th batch tsts wr lft for 24 hours. Glass wool Dy solution Dcolorizd solution Figur 2 Column xprimntal st-up zon occurring in th fixd bd columns and adsorption capacity is usually in trms of adsorbd dy concntration (Cad), th initial dy concntration (C0), outlt dy concntration (Ct) or normalizd concntration dfind as th ratio of outlt dy concntration to inlt dy concntration (Ct/C0) as a function of tim or volum of fflunt for a givn bd hight. Th fflunt volum can b calculatd by multiplying total flow rat (Q: ml/min) and total flow tim (ttotal: min). Th total adsorbd dy quantity (maximum column capacity) or qtotal was dtrmind by intgrating th ara undr curv of th plot btwn Cad (mg/l) vrsus t (min) multiplid by th man flow rat vlocity (ml/min). Th ara undr th brakthrough curv (A) obtaind by intgrating th adsorbd concntration (Cad: mg/l) vrsus t (min) plot can b usd to find th total adsorbd dy quantity (maximum column capacity). Th total adsorbd dy quantity qtotal (mg) in th column for a givn fd concntration and flow rat is calculatd as: q total Q 1000 tt total t0 C ad dt Th quilibrium uptak q (mg/g) or maximum capacity of th column is dtrmind by division of th total amount of adsorbd (qtotal) pr gram of adsorbnt (w) at th nd of total flow tim. A plot btwn th fflunt volums against tim was constructd. Th charactristic paramtrs obtaind from brakthrough curvs also prsntd in Tabl 1. It was found that th plot of distillatd watr flow rat vrsus tim was linar with corrlation cofficints of R showing no blocking of liquid transfrrd through organo-corn straw in th column. 3. Rsarch rsults and discussion 3.1. Effct of contact tim Th ffct of contact tim on th dy uptak from th aquous solution is dpictd in Figur 3. Th adsorption capacity of grn 40 dy on th organo-corn straw rapidly incrasd in th first 10 min and maintaind a slowr incras until constant at 300 min (quilibrium tim). Th fast adsorption rat in th initial stag coms from th fact that thr was a plntiful availability of activ sits on th xtrnal surfac of admicll coatd on th organo-corn straw surfac so that dy molculs wr solubilizd on th admicll surfac asily and quickly. Th slowr sorption (1) Figur 3 Effct of contact tim on adsorption capacity of grn 40 on organo-corn straw, C0: 200 mg/l, ph 5.0 Figur 4 Effct of initial ph solution on th sorption of grn 40 on organo-corn straw, C0: 200 mg/l, ph: , Contact tim: 24 hrs 3.2. Effct of initial ph solution Th adsorption capacity of grn 40 on th organo-corn straw stadily dcrasd with incrass in th ph solution as dpictd in Figur 4. Th high dcras is probably attributd to th dissociation of functional groups in th alkali mdium. Grn 40 contains thr functional groups including carboxyl, hydroxyl and long chain alkyl groups involving th adsorption [11]. Th carboxyl and hydroxyl groups of th grn 40 intracts with at th positivly fixd chargs of xtrnal surfac of admicll du to lctrostatic intractions so that th incras of hydroxid ions portion causs highr comptition of conjugatd bass (dissociatd functional groups) and th activ sits of adsorbnt. On th othr hand, th dy molculs and th conjugatd bass ar of diffrnt hydrophobicity. Th two hypothtical xplanations could b sufficintly givn for th dcras of dy uptak at high solution ph. Th hypothtical schmatic diagram which purposd intractions btwn grn 40 and organo-corn straw purposd is shown in Figur 5. Thrfor, th dy adsorbd by th organo-corn straw should b highly ph dpndnt. Furthrmor, ths rsults also show that grn 40 can b rmovd from th dy-loadd adsorbnt in an alkali mdium aftr th adsorption at low solution ph trminatd.

4 253 KKU ENGINEERING JOURNAL July Sptmbr 2015;42(3) Figur 5 Schmatic diagram for intractions btwn grn 40 and organo-corn straw 3.3. Kintic studis Th kintic data ar usually fittd by wll-known stablishd kintic modls such as th psudo-first ordr kintic modl and psudo-scond ordr kintic modl. Th psudo-first ordr modl proposd by Lagrgrn [13] is xprssd in th form dq dt k ( q q ) (2) 1 t whr q and qt ar th adsorption capacity (mg/g) of dy at quilibrium and at a tim t rspctivly, and k1 is th constant rat for psudo-first ordr adsorption (L/min). Aftr intgration and application of initial condition qt = 0 at t = 0, quation (2) bcoms ln( q q ) ln q k t t 1 ) (3) Th bst fit to kintic data to quation (3) rvaling that th xtrnal mass transfr through a boundary layr is th rat of limiting stp. Th psudo-scond ordr quation proposd by Ho [14] can b writtn as dqt dt k (4) 2 2 ( q qt ) whr k2 is th constant rat for psudo-scond ordr adsorption (g/(mg.min)). For th initial condition qt = 0 at t = 0, th intgratd form of quation (4) bcoms t q t 1 1 t 2 (5) k q q 2 Th bst fit to kintic data to quation (5) indicating that th formation of intraction btwn adsorbat and adsorbnt on th xtrnal surfac of adsorbnt is th rat of limiting stp. Tabl 1 Kintic modl paramtrs and corrlation cofficints Modl Paramtr Valu Psudo-first ordr modl Psudo-scond ordr modl q(xp) (mg/g) k1 (1/min) q(cal) (mg/g) R k2 (g/(mg.min)) q(cal) (mg/g) R Th paramtrs of th kintic modls ar givn in Tabl 1. Th xprimntal adsorption capacity q (xp) is th highst on at quilibrium stag obtaind dirctly from th Fig. 3. Poor corrlation of th kintic data with th psudofirst ordr kintic quation was obsrvd. Normally, th psudo-first ordr quation was wll fittd for th data obtaind at th initial stag of th batch xprimnt. A good corrlation btwn th kintic data and th psudo-scond ordr quation was found. Th formation of hydrophobichydrophobic intraction btwn dy molculs and th adsorbnt wr found on th xtrnal surfac of th biosorbnt. Th hydrophobic-hydrophobic intraction is a phnomnon in which nonpolar substancs to aggrgat in aquous solution and xclud watr molculs. This stp taks th longst tim compard to othr stps, also known as th rat of limiting stp. Th rsults showd that th kintic data wr wll dscribd by th psudoscond ordr (R 2 = ) indicating chmical sorption could b involvd in th adsorption procss. C q C 1 q ( k. q ) (6) m L m

5 KKU ENGINEERING JOURNAL July Sptmbr 2015;42(3) Adsorption isothrms Th adsorption isothrm is th plot of adsorption capacity vrsus dy concntration at th quilibrium stag. Adsorption isothrms dvlopd by Langmuir and Frundlich [15] wr commonly usd to fit th quilibrium data. Langmuir isothrm is rlatd to th sorption taking plac at spcific homognous sits within th adsorbnt. Frundlich isothrm is basd on th assumption of a htrognous surfac with a non-uniform hat distribution of th sorption along th surfac. Th linar quations of Langmuir isothrm is shown blow whr qm is monolayr capacity or limiting sorption (mg/g) and kl is Langmuir constant (L/mg). Th paramtrs can b valuatd from th slop and intrcpt of th linar plat of C/q against C. Th linar quation of Frundlich isothrm is ln q 1 ln kf ln C (7) n whr kf is Frundlich charactristic constant (mg/g)(l/g) 1/n and 1/n is th htrognity factor of adsorption. Th paramtrs can b obtaind from th intrcpt and slop of th linar plat of ln q against ln C rspctivly. Th adsorption isothrms of grn 40 which ar a rlationship btwn q and C ar shown in Figur 6. Th adsorption capacity of th grn 40 incrasd with quilibrium concntration. Th quilibrium data obtaind wr fittd to th Langmuir and Frundlich modls. Th isothrm constants and corrlation cofficints for th adsorption of grn 40 on th organo-corn straw ar listd in Tabl 2. According to th corrlation cofficints r 2, it can b sn that th systm followd both th Langmuir and th Frundlich isothrms. This suggsts that th monolayr and/or multilayr covrag on th adsorbnt surfac took plac Fixd bd column adsorptions Figur 7 shows th ffct of inlt grn 40 concntrations of 50 to 200 mg/l on th brakthrough curvs in a fixd bd with a bd hight of 16 cm and a flow rat of 3.5 ml/min. It was obsrvd that th normalizd concntration (Ct/C0) initially incrasd with tim t and thn rmaind constant. Th brakthrough tim of 50 mg/l initial dy concntration was th longst compard to that of 100 mg/l and 200 mg/l rspctivly. This may b bcaus th lowr inlt concntration causd a smallr driving forc so that th mass transfr rat from th liquid phas to th solid surfac was small. Highr inlt dy concntrations hav highr mass transfr and th fastr brakthrough tim is bcaus of th fastr saturation rat. This rsults in a shortr mass transfr zon lngth [16-18]. Thrfor, th fastr brakthrough point apparanc was a rsult of incrasd inlt dy concntration. Figur 8 shows th brakthrough curv of grn 40 adsorption on th organo-corn straw with diffrnt bd hights of 8, 16, and 24 cm (0.2, 0.4, and 0.6 g) and an inlt dy concntration of 100 mg/l and a flow rat of 3.5 ml/min. Th brakthrough tim incrasd with an incras in th bd hight du to a highr bd hight that gav a highr amount of organo-corn straw and mor binding sits for th adsorption. This rsultd in a broadnd mass transfr zon. Highr adsorption capacity was obsrvd at th highr bd hight du to an incras in th surfac ara in th fixd bd column. Figur 6 Adsorption isothrm of th sorption of grn 40 on organo-corn straw, C0: mg/l, ph 5.0 Tabl 2 Isothrm constants and corrlation cofficints Modl Paramtr Valu Langmuir isothrm Frundlich isothrm qm (mg/g) kl(l/g) r kf ((mg/g)(l/g) 1/n ) n 3.46 r Brakthrough curvs of grn 40 adsorbd on th organocorn straw in fixd bds at diffrnt flow rats of 1.4, 3.5, and 7.0 ml/min wr invstigatd with an inlt dy concntration of 100 mg/l and bd hight of 16 cm as dpictd in Figur 9. It was obsrvd that th brakthrough tim appard fastr with incrasd flow rats. At a lowr flow rat, th inlt dy molculs had a longr tim in contact with th fixd bd in th column rsulting in closr quilibrium adsorption stag. At a highr flow rat, th adsorption capacity was lowr du to shortr contact tim in th column and th dy molculs laving th fixd bd column bfor raching th quilibrium stag. Tabl 3 shows not only th xprimntal conditions in fixd bd columns but also th brakthrough charactristics, total adsorption capacity (qtotal), and quilibrium dy uptak (q) of grn 40 in th organo-corn straw undr diffrnt conditions. Th brakthrough point (th position at Ct/C0 = 0.05) appard fastr with an incras in liquid flow rat and initial dy concntration, but slowr with an incras in bd hight. Th highst of brakthrough tim (tb) and brakthrough volum wr 220 min and 308 ml obtaind undr th conditions of an inlt dy concntration of 100 mg/l, bd hight of 16 cm, and flow rat of 1.4 ml/min. Th quilibrium bd capacity (q) was mg/g obtaind undr th conditions of 200 mg/l grn 40 concntration, 16 cm bd hight, and flow rat of 3.50 ml/min. It was considrd that inlt dy concntration was a main factor that causd th adsorption to rach th narst quilibrium stag. It was ncssary to fit th adsorption data using stablishd modls and subsquntly dtrmin noticabl paramtrs associatd with two modls to dtrmin thir influnc for optimization of th fixd bd adsorption procss.

6 255 KKU ENGINEERING JOURNAL July Sptmbr 2015;42(3) Figur 7 Effct of inlt dy concntration on brakthrough curv of th sorption of grn 40 on organo-corn straw, Flow rat: 3.5 ml/min and Bd hight: 16 cm Figur 8 Effct of bd hight on brakthrough curv of th sorption of grn 40 on organo-corn straw, C0: 100 mg/l and Flow rat: 3.5 ml/min Tabl 3 Exprimntal conditions and charactristic paramtrs obtaind from brakthrough curvs and Adams-Bohart, Thomas and Yoon-Nlson modl constants C 0 (mg/l) Conditions Hight (cm) Flow rat (ml/min) V b (ml) Brakthrough t b (ml) paramtrs q total (mg) q (mg/g) Adams-Bohart modl k AB (L/mg.min) N 0 (mg/l) r , , , , , , , k Th (ml/min/mg) Thomas modl q 0 (mg/g) ,030 1, r Yoon-Nlson modl k YN (1/min) τ (min) r In this work, thr modls wr usd namly Adams- Bohart, Thomas, and Yoon-Nlson modls for kintic studis in fixd bd columns. Th Adams-Bohart modl is usd for th dscription of th initial part of th brakthrough curv. Th xprssion is xprssd as [19]: Ct ln C0 k AB C t k 0 AB N whr kab is th kintic constant (L/mg.min), F is th linar flow rat (ml/min), Z is th bd dpth of column (cm), N0 is 0 Z F (8) th saturation concntration (mg/l), and t is tim (min). Paramtrs dscribing th charactristic oprations of th column (kab and N0) wr calculatd using linar rgrssion analysis according to quation (8). From a linar plot of ln (Ct/C0) against tim (t), valus of kab and N0 wr dtrmind from th intrcpt and slop of th plot (figur not shown). Aftr applying th Adams-Bohart modl to xprimntal data, a linar rlationship btwn ln (Ct/C0) and tim (t) according to quation (8) was obsrvd. Th paramtrs N0, and kab wr intrprtd from th plot which ar prsntd in Tabl 4 togthr with corrlation cofficints (R 2 > ). Th valus of kab dcrasd with incrass in dy

7 KKU ENGINEERING JOURNAL July Sptmbr 2015;42(3) 256 adsorption for ach adsorbat molcul is proportional to th probability of th adsorbat adsorption and th adsorbat brakthrough on th adsorbnt. Th linarizd Yoon-Nlson quation rgarding to a singl componnt systm is xprssd as: C0 ln Ct 1 k YN k YN t (10) Figur 9 Effct of flow rat on brakthrough curv of th sorption of grn 40 on organo-corn straw, C0: 100 mg/l and Bd hight: 16 cm concntration and flow rat, but incrasd with incrass in bd hight. This showd that th ovrall kintics systm was dominatd by xtrnal mass transfr in th initial part of adsorption in th column [20]. Although th Adams-Bohart modl provids a simpl and comprhnsiv approach to running and valuating sorption-column tsts, its validity is limitd to th rang of conditions usd. Th Thomas modl is known as th bd-dpth-srvictim (BDST) modl [21]. Th BDST approach is basd on th irrvrsibl isothrm modl by Bohart and Adams [16]. This simplifid-dsign modl ignors both th intraparticl (solid) mass transfr rsistanc and th xtrnal (fluid-film) rsistanc dirctly. This mans that th rat of adsorption is controlld by th surfac raction btwn th adsorbnt and th unusd capacity of th adsorbnt. This xprssion of Thomas modl for an adsorption column is givn as follows: C ln Ct kthq0m kthc0 V (9) Q Q 0 1 whr kth is th Thomas rat constant (ml/min/mg), q0 is th maximum adsorption capacity (mg/g), M is th total mass of th adsorbnt (g), Q is volumtric flow rat (ml/min), and V is th throughput volum (ml). Paramtrs dscribing th charactristic oprations of th column (kth and q0) wr calculatd using linar rgrssion analysis according to quation (9). From a linar plot of ln[(ct/c0)-1] against volum (V), valus of kth and q0 wr dtrmind from th slop and intrcpt of th plot (figur not shown). Th kintic cofficint kth and th adsorption capacity q0 ar givn in Tabl 4. Thomas rat constant kth is dpndnt on flow rat, initial dy concntration, and bd hight. Th maximum adsorption capacity q0 dcrasd with an incras in flow rat and initial dy concntration but dcrasd with an incras in bd hight. Th rsults indicat that valus of kth dcrasd with th incrass in initial dy concntrations and flow rats and bd hights. This showd that th ovrall kintics systm was dominatd by th surfac raction btwn th adsorbnt and th unusd capacity of adsorbnt in th initial part of adsorption in th column [16]. High valus of corrlation cofficints (r 2 > ) indicatd that th Thomas modl fittd wll to th xprimntal data. Yoon and Nlson [22] dvlopd a modl basd on th assumption that th rat of dcras in th probability of whr kyn (1/min) is th rat constant, τ (min) is tim rquird for 50% grn 40 brakthrough, C0 (mg/l) is initial dy concntration, C (mg/l) is quilibrium dy concntration in solution, and t (min) is tim. A linar plot of ln [(C0/Ct)-1] against tim (t) was mployd (figur not shown) to dtrmin valus of kyn and τ from th intrcpt and slop of th plot. Th Yoon and Nlson modl was fittd to invstigat th brakthrough bhavior of grn 40 on organo-corn straw. A plot of ln[(c0/ct)-1] vrsus t gav a straight lin with a slop of kyn, and intrcpt of τkyn. Th valus of kyn and τ obtaind ar also listd in Tabl 4. Th rsults showd that th rat constant, kyn dcrasd with an incras in inlt dy concntration, but incrasd with an incras in flow rat and bd hight. Also, th tim rquird for 50% brakthrough τ dcrass with an incras in bd hight and liquid flow rat but incrass in initial dy concntration. High valus of corrlation cofficints (r 2 > ) indicatd that Yoon and Nlson modl fittd wll to th xprimntal data. Th dcras of kyn with th incrass in dy concntration, but incrasd with th incrass in bd hight and flow rat. This showd that th incras in initial dy concntration incrass th comptition btwn adsorbat molculs for th adsorption sits, which ultimatly rsults in incrasd uptak rat [16]. 4. Conclusion Adsolubilization of corn straw with cationic surfactant altrs th solubility of th biosorbnt surfac from hydrophilic to organophilic. Batch adsorption rsults showd that th adsorption capacity rapidly incrasd in th first 10 min and rachd quilibrium within 5 h. Th amount of th dy adsorbd dcrasd with incrass in ph0. Th adsorption isothrm followd Langmuir and Frundlich isothrms. Th kintic data obyd th psudo-scond ordr kintic modl indicating that th forming rat of hydrophobic-hydrophobic intractions on th biosorbnt surfac was th rat of limiting stp. Th rsults of fixd bd column xprimnts showd that th brakthrough point appard fastr with incrass in liquid flow rat and bd hight but wr slowr with incrass in inlt grn 40 concntrations. Th highst bd capacity of mg/g was obtaind undr th conditions of 200 mg/l inlt grn 40 concntration, 16 cm bd hight, and 3.6 ml/min flow rat. Th column xprimntal data wr analyzd by th Adams- Bohart, Thomas, and Yoon-Nlson modls. For grn 40 adsorption, th column data wr fittd wll to th Thomas and Yoon-Nlson modls. Th rsults xhibitd that th organo-corn straw is ffctiv in th rmoval of grn 40 from aquous solutions. 5. Acknowldgmnts Th rsarch was financially supportd by th Nation Rsarch Council of Thailand in 2013 and Th authors xprss thir sincr gratitud to Bob Trmayn from th

8 257 KKU ENGINEERING JOURNAL July Sptmbr 2015;42(3) Offic of Intrnational Rlations at Ubon Ratchathani Univrsity for assistanc with English. 6. Rfrncs [1] Yang XY, Al-Duri B. Application of branchd por diffusion modl in th adsorption of ractiv dys on activatd carbon. Chm Eng J 2001;83:1523. [2] Chrn JM, Huang SN. Study of nonlinar wav propagation thory-1-dy adsorption thory-1-dy adsorption by activatd carbon. Ind Eng Chm Rs 1998;37: [3] Wibulswas R. Batch and fixd bd sorption of mthyln blu on prcursor and QACs modifid montmorillonit. Spar Purif Tchnol 2004;39:3-12. [4] Charuwong P, Kiattikomol R. Rmoval of organic compounds from aquous solution by using montmorillonit clays and Oragno-clays. Suranar J Sci Tchnol 2004;11: [5] Jaruwong P, Aumpush J, Kiattikomol, R. Uptak of cationic and azo dys by montmorillonit in batch and column systms. Thammasat Int J Sci Tchnol 2005;10(1): [6] Tng MY, Lin SH. Rmoval of mthyl orang dy from watr onto raw and acid-activatd montmorillonit in fixd bds. Dsalination 2006;201: [7] Wang L, Wang A. Adsorption charactristics of congo rd onto th chitosan/ montmorillonit nanocomposit. J Hazard Matr 2007;147: [8] Xu Z, Cai JG, PAN BC. Mathmatically moding fixdbd adsorption in aquous systms. J Zhjiang Univ- Sci A (Appl Phys & Eng) 2013;14(3): [9] Sivakumar P, Palanisamy PN. Packd bd column studis for th rmoval of Acid blu 92 and Basic rd 29 using non-convntional adsorbnt. Indian J Chm Tchnol 2009;16: [10] Umpuch C, Jutarat B. Adsorption of organic dys from aquous solution by surfactant modifid corn straw. Int J Chm Eng Appl 2013;4(3): [11] Umpuch C. Batch adsorption of organic dys by Organo-bagass: Carbon contnt, ph influnc, kintics and isothrms. IJE Transactions A: Basics 2015;28(4): [12] Kuo KK, Acharya R. Fundamntals of Turbulnt and Multiphas Combustion. Nw Jrsy: John Wily & Sons, Inc; [13] Lagrgrn S, Svnska BK. About th thory of socalld adsorption of solubl substancs. Vatrnskapsakad Handlingar 1898;24(4):1-39. [14] Ho YS, McKay G. Sorption of dy from aquous solution by pat. Chm Eng J 1998;70: [15] Umpuch C, Sakaw S. Rmoval of mthyl orang from aquous solutions by adsorption using chitosan intrcalatd montmorillonit. Songklanakarin J Sci Tchnol 2013;35(4): [16] Ahmad AA, Hamd BH. Fixd-bd adsorption of ractiv azo dy onto granular activatd carbon prpard from wast. J Hazard Matr 2010;175: [17] Umpuch C, Sakaw S. Adsorption charactristics of ractiv black 5 chitosan intrcalatd montmorillonit. Dsalin Watr Trat 2015;53: [18] Umpuch C, Jutarat B. Adsorption bhavior of ractiv black 5 on activatd carbon prpard from sugarcan bagass. UBU nginring journal 2012:5(2):10-21 [19] Umpuch C, Sakaw S. Rmoval of mthyl orang from synthtic wastwatr onto chitosan-coatdmontmorillonit clay in fixd-bds. GMSARN Intrnational Journal 2012;6: [20] Aksu Z, Gönn F. Biosorption of phnol by immobilizd sludg in a continuous packd bd: prdiction of brakthrough curvs. Procss Biochm 2004;39: [21] Thomas HC. Htrognous ion xchang in flowing systm. J Am Chm Soc 1944;66: [22] Yoon YH. Application of gas adsorption kintics. Part 1. A thortical modl for rspirator cartridg srvic tim. Am Ind Hyg Assoc J 1984;45: