Adsorption of Water and Ethanol by Canola Meal in a Batch Liquid System

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1 Th Canadian Socity for Bionginring Th Canadian socity for nginring in agricultural, food, nvironmntal, and biological systms. La Société Canadinn d Géni Agroalimntair t d Bioingéniri La société canadinn d géni agroalimntair, d la bioingéniri t d l nvironnmnt Papr No. CSBE Adsorption of Watr and Ethanol by Canola Mal in a Batch Liquid Systm Zakih Ranjbar a Nan Sun a Cathrin H. Niu* a Ajay Dalai a a Dpartmnt of Chmical and Biological Enginring, Univrsity of Saskatchwan, 57 Campus Driv, Saskatoon, SK, S7N 5A9 Canada * Corrsponding author Writtn for prsntation at th CSBE/SCGAB 2013 Annual Confrnc Univrsity of Saskatchwan, Saskatoon, Saskatchwan 7-10 July 2013 ABSTRACT In this papr, adsorption of watr and thanol from liquid phas using canola mal basd adsorbnts was invstigatd. Th rsarch is important as thr is an intrst in using biothanol as a sustainabl nrgy sourc. Th convrsion of carbohydrats to biothanol through frmntation gnrally lads to a broth that contains 5-12 wt% of thanol mixd with watr and som othr organics. In th thanol industry, th rcovry of thanol from th frmntation broth to ful grad is nrgy intnsiv and costly. Adsorption using biosorbnts attracts incrasingly intrst du to low costs and non-toxicity to th nvironmnt. Canola mal is abundantly producd as a by-product in canola industry. Th objctiv of this work is to dtrmin th capability of canola mal basd adsorbnts for adsorption of watr from liquid thanol mixtur. Th ffcts of canola mal particl siz, contact tim, tmpratur and watr/thanol concntration on watr as wll as thanol uptak wr xamind. Sparation factor of watr ovr thanol was also dtrmind. Watr uptak is constantly highr than that of thanol whil both watr and thanol uptak wr fast and compltd ovr 90% of th quilibrium valus within th first 30 min. Th rsults dmonstratd that canola mal basd adsorbnts ar abl to slctivly adsorb watr from thanol mixtur to concntrat thanol. Frundlich quation providd rasonably fit to th psudo-quilibrium watr and thanol adsorption data. Th rsults providd Paprs prsntd bfor CSBE/SCGAB mtings ar considrd th proprty of th Socity. In gnral, th Socity rsrvs th right of first publication of such paprs, in complt form; howvr, CSBE/SCGAB has no objctions to publication, in condnsd form, with crdit to th Socity and th author, in othr publications prior to us in Socity publications. Prmission to publish a papr in full may b rqustd from th CSBE/SCGAB Scrtary, 2028 Calico Crscnt, Orlans, ON, K4A 4L7 or contact scrtary@biong.ca. Th Socity is not rsponsibl for statmnts or opinions advancd in paprs or discussions at its mtings.

2 pionr information on dvloping cost biosorbnts for purifying thanol and rducing th production costs of ful thanol. Kywords: Biosorption, watr adsorption, thanol dhydration, adsorption kintics and quilibrium, sparation factor. INTRODUCTION Protction of th global nvironmnt and dpltion of th convntional hydrocarbon ful supplis hav motivatd rsarchrs to dvlop altrnativ fuls. Ethanol basd biofuls, which can b usd as blnding componnts with hydrocarbon-basd fuls, hav bn considrd mor xtnsivly during th last two dcads. With a high octan numbr and low missions of carbon monoxid, volatil organic compounds and particulats, biothanol maks an xcllnt gasolin blnding componnt (Kumar t al. 2010; Frolkova and Rava 2010). Biothanol is gnrally producd through th frmntation of carbohydrats. Th product of frmntation is a mixtur containing 5-12 wt% of thanol in watr and som organics (Sun t al. 2007). Th prsnc of watr in thanol is undsirabl whn blnding with hydrocarbons. Consquntly, thr is a grat intrst to obtain anhydrous thanol in ordr to us it as a ful (Frolkova and Rava 2010). Howvr, sparation of thanol from th larg amount of watr is nrgy intnsiv procss (Jong t al. 2009). In ordr for thanol to b considrd as a substitut ful, th nrgy consumd in th thanol production industry should b rducd (Kumar t al. 2010). Th currnt mthod usd in th industrial thanol dhydration consists of distillation of frmntation strngth thanol to obtain a wt% thanol-watr product which is blow th azotrop (95.6 wt% thanol), followd by watr adsorption using molcular sivs to obtain ful grad thanol (Sun t al. 2007). Howvr, th commrcial 3-A molcular sivs which ar usd in thanol dhydration hav low watr uptak of 0.25 g /g dry adsorbnt (Simo t al. 2009; Carmo and Gubulin 2006). Thy also nd high tmpratur in th rang of C for rgnration (Fahmi t al. 1999). Thrfor, thr has bn a grat intrst in dvloping cost ffctiv tchnology for thanol dhydration procss. A varity of starchy and cllulosic matrials was usd as adsorbnts to rmov watr from thanol-watr vapor mixturs (Baylak t al. 2012; Chang t al. 2006; Chang t al. 2004; Chang 2001; Hong t al. 1982; Ladisch and Dyck 1979). It has bn rportd that corn grits hav bn usd in th thanol dhydration industry, which shows that biosorbnts hav th potntial to b commrcializd (Bry and Ladisch 2001). Howvr, th watr uptak of corn grit is as low as 0.2 g/g dry adsorbnt and us of this biomatrial as an adsorbnt can plac prssur on food consumption. Attmpts hav bn mad using othr typs of biomatrials such as barly straw and what straw (Sun t al. 2007) and saw dust (Bnson and Gorg 2005). A potntial biomatrial which can b usd as an adsorbnt for thanol dhydration is canola mal. A larg amount of canola mal is producd in th canola industris du to oil xtraction and biodisl production. Th commrcial pric of canola mal is about $0.24 /kg, much chapr than that of molcular sivs ($3-120 /kg). Th immdiat bnfits of canola mal commrcialization as an adsorbnt in th thanol dhydration industry includ low thanol production cost and nhancmnt of agricultural industry by slling thir wast products. Furthrmor, incras in th thanol production rat will bnfit th nvironmnt. Prliminary rsults of using canola mal basd adsorbnt to rmov watr from watr-thanol vapor mixtur was rportd rcntly by our rsarch tam (Baylak t al. 2012). Howvr, no rsults hav bn rportd to lucidat th capacity of such biomatrial for watr and thanol adsorption dirctly from th liquid phas which is th product of frmntation for biothanol production. 2

3 Th objctiv of this work is to dtrmin th capability of canola mal basd adsorbnts for adsorption of watr from liquid thanol mixtur. To that nd, watr and thanol uptaks by canola mal wr dtrmind and usd to optimiz th conditions for slctiv watr uptak in thanolwatr mixturs. Th ffcts of particl siz of canola mal, tmpratur, contact tim, and adsorption isothrm wr studid. EXPERIMENTAL SECTION Biosorbnts Th canola mal usd as an adsorbnt was obtaind from Co-op Fds Saskatoon, Saskatchwan Canada. Canola mal was sivd in fiv particl siz groups of mm, mm, mm, mm, and > 3.35mm, rspctivly. Th biosorbnt particls wr thn ovn drid at 105 C for 24 hrs. Fd solutions Ethanol watr solutions with diffrnt concntrations wr prpard by mixing anhydrous thanol (ragnt grad, Commrcial Alcohols Inc., Canada) and dionizd watr. Adsorption Procdur Sampls wr prpard by mixing 4 g dry canola mal and 150 g watr, thanol or a mixtur of watr and thanol in 250 ml Erlnmyr flasks on an orbital shakr at 130 rpm for a crtain amount of tim. Th shaking spd was chosn by providing sufficint mixing but liminating biomass ruptur bcaus of shar forc. To dtrmin th watr and thanol uptak of canola mal in pur watr or thanol solution, th wight diffrnc of wt and dry biosorbnt was dividd by th wight of th dry biosorbnt; whil, th following quation which is basd on th mass balanc of watr and thanol in th systm was usd to dtrmin th watr and thanol uptak in thanol-watr mixtur. q xp = (C 0 W 0 -C t W t ) /w (1) Co and Ct ar th thanol or watr concntrations in liquid phas at th bginning and at tim t, rspctivly, (wt %). W 0 and W t ar th initial wight of solution and that at tim t (g). w and q xp rprsnt th dry nt biosorbnt wight (g) and xprimntal uptak (g/ g dry biosorbnt), rspctivly. Analyss Watr and thanol contnt wr dtrmind by a Karl Fishr coulomtr (Mttlr Toldo DL32) and a Chmical Analyzr (Analox GM8), rspctivly. RESULTS AND DISCUSSION Effct of Particl Siz Th ffcts of biosorbnt particl siz on th uptak of watr and thanol was don by varying th particl sizs of canola mal as follows: : mm, mm, mm, and mm. Each sampl consistd of 4 g of canola mal and 150 g pur watr or pur thanol shakn at 130 rpm on th shakr for 30 min. Th rsults ar shown in Figur 1. Th data ar xprimntal rsults and th rror bars rprsnt 95% confidnc intrvals. Th xprimntal rsults dmonstratd that both thanol and watr uptak wr incrasd as th particl sizs wr dcrasd. This is bcaus th smallr th particl siz of canola mal, th highr th surfac ara availabl for adsorption, th fastr th adsorption. 3

4 Figur 1. Effct of particl sizs of canola mal on watr/thanol uptak All xprimnts wr run at 25 o C for 30 min. Each sampl containd 4 g dry adsorbnts and 150 g pur watr or thanol solution. Error bar stands for 95% confidnc intrval. Optimum particl siz dos not only nsur high watr uptak but also high ratio of watr ovr thanol uptak. Though watr uptak incrasd at smallr particl sizs, th ratio of th watr to thanol uptak dcrasd, which is not dsirabl. For instanc, watr uptak is 2.08 g/g at th particl sizs of mm, and ratio of watr to thanol uptak is Whn th particl sizs wr dcrasd to mm, watr uptak incrasd to 2.34 g/g but th ratio was dcrasd to This is bcaus thanol uptak was incrasd as wll at dcrasd particl sizs. Th rsults ar similar to watr-thanol uptak by cllulosic matrial barly straw (Sun t al. 2007). As a rsult, canola mal with particl sizs in th rang of mm wr slctd for th following invstigation considring both highr watr uptak and th ratio of watr to thanol uptak. Dynamic Study Tmpratur has a significant ffct on adsorption capacity of an adsorbnt (Sljko 1985). Th dynamic study of watr or thanol uptak was don by varying tmpratur from 5 60 C. Each sampl containd 4 g of canola mal mixd in 150 g of pur watr or pur thanol solutions. Th watr and thanol uptaks of canola mal wr dtrmind at spcific tim intrval. Th rsults of watr uptak at diffrnt tmpratur ar shown in Figur 2. It was dtrmind that th watr uptak at all th tstd tmpraturs incrasd rapidly with tim, achivd ovr 90% of th quilibrium uptak during th first 30 min, and rachd quilibrium at about 2 hrs. Th rsults ar quit similar to watr uptak by cllulosic barly straw (Sun t al. 2007). Canola mal contains 20% nutral dtrgnt fibr consisting of cllulos, hmicllulos and lignin (Canola Council of Canola 2009). Watr uptak occurs btwn watr molculs and polar groups in canola mal. This physical adsorption is fast. In addition, by incrasing th tmpratur from 5 to 60 o C, watr adsorption was rapidly incrasd for th first 30 min. Howvr, highst 4

5 quilibrium watr uptak was achivd at 25 o C among th tstd tmpraturs. Th quilibrium watr uptak dcrasd as follows: 25 o C > 40 o C > 60 o C > 5 o C, indicating th watr uptak at o C may b xothrmic. Figur 2. Dynamic study of watr adsorption at diffrnc tmpratur Each sampl containd 4 g dry adsorbnts and 150 g pur watr solution. Th particl sizs of canola mal adsorbnts wr mm. Th rsults ar also similar to that obtaind in thanol-watr liquid systm using barly straw as biosorbnt (Sun t al. 2007) in which watr uptak was favord at 25 o C among th tstd tmpratur rang of 5 60 o C. At 5 o C, th structur of cllulosic componnts in canola mal is dns which maks it difficult for watr molculs to accss th sits in canola mal, thus uptak is low. Th ffct of tmpratur on thanol uptak is shown in Fig. 3. Similarly, as th tmpratur incrasd th thanol uptak incrasd for th first 30 min. Howvr, 5

6 Figur 3. Dynamic study of thanol adsorption at diffrnc tmpratur Each sampl containd 4 g dry adsorbnts and 150 g pur thanol solution. Th particl sizs of canola mal adsorbnts wr mm. quilibrium thanol uptak almost rachd th sam valu at 25 o C, 40 o C, and 60 o C, whil bing lowr at 5 o C. Again ovr 90% of quilibrium thanol uptak was achivd at th first 30 min and rachd quilibrium at about 2 hrs. Th mchanism of thanol uptak by canola mal is not clar. It might b causd by diffusion of th rlativly larg thanol molcul into th pors of th biomatrial particls followd by physical ntrapmnt. Again thanol molcul was not abl to succssfully accss th adsorption sit bcaus of dns structur of canola mal at 5 o C. Watr uptak by canola mal is constantly highr than thanol uptak at th tstd tmpratur rang, dmonstrating canola mal has highr watr adsorption capacity ovr thanol. Sinc ovr 90 % of quilibrium watr or thanol uptak was achivd within th first 30 min and th uptak incrasd at a slow rat bfor raching quilibrium, contact tim of 30 min was tchnically considrd for th following psudo-quilibrium xprimnts. Psudo-Equilibrium Isothrm To study th capacity of canola mal to adsorb watr from a watr-thanol mixtur, watr and thanol uptaks of canola mal wr dtrmind in watr solution containing 0 100% thanol at 25 o C for 30 min which was considrd as psudo-quilibrium. Th rsults ar shown in Figur 4. It was found that watr uptak by canola mal particls incrasd by incrasing watr concntration in th thanol-watr mixtur. This dmonstrats th ability of canola mal biosorbnt to adsorb watr from thanol-watr mixtur with a wid rang of watr concntration (4-100 wt %). Fig.4 also shows that canola mal particls ar abl to adsorb thanol in a mixtur containing wt% thanol. Howvr, th maximum thanol uptak (0.68 g/g) is much lowr than that of watr (2.08 g/g). Th watr uptak is constantly highr than that of thanol in th tstd rangs. 6

7 Canola mal consists of multi-componnts (Canola Council of Canola 2009). For a htrognous surfac, a classical isothrm is th Frundlich isothrm (Prry t al. 2008). Th isothrm corrsponds approximatly to an xponntial distribution of hats of adsorption. Although it lacks th rquird linar bhavior in th Hnry s law rgion, it can oftn b usd to corrlat data on htrognous adsorbnts ovr wid rangs of concntration. Frundlich quation was dfind as follows: q f n = K C (2) whr q and solution (wt%), rspctivly. C ar quilibrium sorbat concntration on th adsorbnt surfac (g/g) and in th K f is th Frundlich constant rlatd to th binding capacity of sorbnt for sorbat (g/g) and n th affinity. In this work, K f and n ar dtrmind by nonlinar rgrssion of Equation (2). Th optimal combination of paramtr sts in th abov modl was obtaind by minimizing th objctiv function rror: whr (g/g). rr = q q q q xp and q ar th xprimntally obtaind and th modl calculatd uptaks, rspctivly Th modl rsults ar shown in Figur 4 and Tabl 2. It can b sn that Frundlich quation providd accptabl simulation to both watr and thanol isothrms. Th cofficints of dtrmination r 2 wr abov 0.97, and th standard rrors of th stimat wr lss than Eithr Langmuir modl or Langmuir-Frundlich did not provid satisfid rsults. Th obtaind watr adsorption isothrm bing convx upward throughout indicats that watr adsorption is favorabl and th thanol adsorption isothrm is concav upward throughout indicats thanol adsorption is unfavorabl.(prry t al. 2008) Th rsults ar diffrnt from watr / thanol adsorption by barly straw, in which Langmuir-Frundlich modl gav th bst fit to watr isothrm, and non of abov modls fit th thanol isothrm. Sinc th composition of canola mal is diffrnt from that of barly straw, thir adsorption bhaviors ar diffrnt. Th watr uptak of 2.08 g/g dry canola mal achivd in this liquid systm is much highr than that of th 3A molcular sivs (MS) ( g watr/g MS), which is commonly usd in industrial thanol dhydration procss (Simo t al. 2009; Carmo and Gubulin 2006). It is also highr than watr uptak by canola mal (0.16 g/g) from an thanol-watr vapor mixtur in a prssur swing adsorption procss (Baylak t al. 2012) which was affctd by th procss paramtrs such as tmpratur, prssur, and fd flow rat. Barly straw has a watr uptak of 6.66 g/g and thanol uptak of 2.81 g/g (Sun t al. 2007) in thanol-watr liquid mixtur at th similar xprimntal conditions, which ar rspctivly highr than that of canola mal (2.08 g watr/g and 0.66 g thanol/g). As a rsult, th molar ratio of watr to thanol uptak by canola mal of 8.1 is highr than that of barly straw 6.1. In ordr to quantify th slctivity of watr ovr thanol uptak, a sparation factor was dfind as (Baylak, t al., 2012), X / X xp xp 2 w α = (4) Yw / Y (3) 7

8 Uptak (g/g) Watr Watr-modl Ethanol Ethanol-modl Concntration in Ethanol-Watr Mixtur (wt%) Figur 4. Psudo-quilibrium adsorption isothrms of watr and thanol Sampls wr run at 25 o C for 30 min. Each sampl containd 4 g dry adsorbnts and 150 g solution. Error bars rprsnt 95% confidnc intrval. whr Xw and Yw ar th mass fraction of watr in th adsorbd phas and liquid phas, rspctivly, and X and Y ar th corrsponding thanol mass fraction. Th sparation factors wr dtrmind to b in th rang of 5-16 according to spcific quilibrium watr-thanol concntration in th liquid phas. Th valus ar highr than that obtaind by canola mal for thanol-watr vapor adsorption bing 2-3 (Baylak t al. 2012). No rsults on sparation factors of othr adsorbnts undr th sam xprimntal conditions wr rportd. Thus furthr comparison was not mad. Th watr saturatd canola mal was rgnratd by ovn drid at 105 o C for 24 hrs and was rusd for adsorption. CONCLUSION Canola mal was abl to slctivly adsorb watr from thanol-watr liquid mixtur in a wid rang of watr concntration from 4 to 100 wt%. Watr uptak is constantly highr than that of thanol. Ovr 90% of quilibrium watr or thanol uptak was achivd within th first 30 min. Watr and thanol uptak wr associatd with th spcific surfac ara of th canola mal particls. Optimum watr uptak was achivd at 25 o C. Th psudo-quilibrium isothrms of watr or thanol uptak wr rasonably wll fit by Frundlich quation. Th watr saturatd canola mal was asily ovn drid and rusabl. Th rsults dmonstratd that canola mal has a potntial for thanol dhydration. ACKNOWLEDGEMENTS This work was supportd by National Scinc and Enginring Rsarch Council of Canada Discovry Grant, Saskatchwan Canola Dvlopmnt Commission, Saskatchwan Agricultur Dvlopmnt Fund, Univrsity of Saskatchwan Tri-Council Bridg Funding, and Agricultur Bioproducts Innovation Program of Canada. 8

9 NOMENCLATURE C 0 Initial concntration of sorbat in liquid phas ( wt %) C t Concntration of sorbat in liquid phas at tim t (wt %) C K f Equilibrium sorbat concntration in liquid phas (g/g solution) Frundlich constant rlatd to th binding capacity of sorbnt for sorbat n q q xp X Xw Y Yw w W 0 W t Frundlich constant rlatd to affinity of sorbnt to sorbat Calculatd quilibrium sorbat uptak by Frundlich modl (g/g dry adsorbnt) Exprimntal sorbat uptak (g/g dry adsorbnt) Mass fraction of thanol in th adsorbd phas Mass fraction of watr in th adsorbd phas Mass fraction of thanol in th liquid phas Mass fraction of watr in th liquid phas Dry nt biosorbnt wight (g) Wight of solution at initial condition (g) Wight of solution at tim t (g) REFERENCES Baylak, T., Kumar, P., Niu, C. H., and A. Dalai Ethanol dhydration in a fixd bd using canola mal. Enrg. Fuls. 26: Bry, K. E., and M. R. Ladisch Adsorption of watr from liquid-phas thanol - Watr mixturs at room tmpratur using starch-basd adsorbnts. Ind. Eng. Chm. Rs. 40(9): Bnson, T. J., and C. E. Gorg Cllulos basd adsorbnt matrials for th dhydration of thanol using thrmal swing adsorption. Adsorpt J. Intr. Adsorpt. Soc. 11: Canola Council of Canola Canola Mal Fd Industry Guid. Availabl at Accssd on 24 May Carmo, M. J., and J. C. Gubulin Ethanol-watr adsorption on commrcial 3a zolit: kintics and thrmodynamic data. Braz. J. Chm. Eng. (onlin). Chang, H., Yuan, X., Tian, H., and A. Zng Exprimnt and prdiction of brakthrough curvs for packd bd adsorption of watr vapor on cornmal. Chm. Eng. Procss. 45(9): Chang, H., Yuan, X., and A. Zng Adsorption capability of biomass for thanol dhydration. Huagong Xubao. 55(2): Chang, X Progrss of study on conomical procss for thanol dhydration. Niangjiu. 28(5): Fahmi, A., Banat, F. A., and R. Jumah Vapor-liquid quilibrium of thanol-watr systm in th prsnc of molcular sivs. Sp. Sci.& Tchnol. 34(12): Frolkova, A. K., and V. M. Rava Biothanol dhydration: stat of th art. Thor. found. Chm. Eng. 44(4):

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