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A Comparative Kinetic Study of Acidic Hydrolysis of Wastes Cellulose from Agricultural Derived Biomass

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JASEM ISSN All rights reserved Full-text Available Online at and J. Appl. Sci. Envirn. Manage. Dec, 2011 Vl. 15 (4) A Cmparative Kinetic Study f Acidic
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JASEM ISSN All rights reserved Full-text Available Online at and J. Appl. Sci. Envirn. Manage. Dec, 2011 Vl. 15 (4) A Cmparative Kinetic Study f Acidic Hydrlysis f Wastes Cellulse frm Agricultural Derived Bimass AJANI, A O; * AGARRY, S. E; AGBEDE, O. O Bichemical Engineering Research Labratry, Department f Chemical Engineering, Ladke Akintla University f Technlgy, Ogbms, Nigeria ABSTRACT: Bicnversin f agricultural waste prducts t prduce value-added fuels and chemicals ffers ptential ecnmical, envirnmental and strategic advantages ver traditinal fssil-based prducts. The kinetics f acid hydrlysis f cellulse islated frm banana skin, cwpea shells, maize stalks and rice husk (agricultural waste) were studied at temperature ranging between C in a stirred cnical flask which served as a batch reactr. The effect f acid cncentratin n cellulse hydrlysis was als investigated. The results shwed that the rate f hydrlysis by virtue f glucse yield generally increased with increase in temperature and acid cncentratin fr all the fur agricultural wastes used. The experimental data were fitted t integrated first rder rate kinetics and the results btained suggested a first rder rate f glucse frmatin frm fur agricultural wastes cellulse used. The activatin energies estimated frm Arrhenius equatin are KJ/mle, KJ/mle, KJ/mle and KJ/mle fr banana skin, cwpea shells, maize stalks and rice husk cellulse, respectively. These values suggests the ease with which hydrlysis can ccur between the fur agricultural wastes Keywrds: Agricultural wastes; cellulse; acid hydrlysis; first-rder rate kinetics; activatin energy, Arrhenius equatin The agricultural activities f man have resulted in the prductin f large quantities f agricultural waste bimass that tends t dminate and pllute the envirnment. Many f these agr-wastes are allwed t rt away nt utilized (Obt et al., 2008). These wastes bimass cnsist f cellulse, hemicellulse, lignin and ther materials called extractive (Ghse, 1956, Aberuagba, 1997). Amng all the cnstituents f agricultural wastes bimass, cellulse cnstitutes the highest percentage because it is a strng elastic material that frms the cell wall f nearly all plants (Aberuagba, 1997). The cellulse can be hydrlyzed t prduce glucse fr human needs, which can further be used as substrates fr fermentative prductin f useful prducts like alchls (Jhn et al., 2007; Benkun et al., 2008). Bicnversin f agricultural wastes bimass t prduce value-added fuels and chemicals ffers ptential ecnmical, envirnmental and strategic advantages ver traditinal fssil-based prducts (Anex et al., 2007). Generally, agricultural wastes frm different surces have different physical prperties such as surface area, lignificatins, crystallinity and ther different chemical cmpsitins that culd hinder the accessibility susceptibility f cellulse fr hydrlysis (Aberuagba, 1997; Caritas and Humphrey, 2006). Hwever, they may be mdified t enhance their susceptibility t hydrlysis thrugh pretreatment prcesses. The pretreatment prcess (physical, chemical and/r micrbial) alters the structure and cmpsitins f the agricultural wastes bimass and this remves extractives, lignin and hemi-cellulse, reduce cellulse crystallinity and increase prsity (Aberuagba, 1997; Ander and Ericsn, 1983; Sun and Cheng, 2002). Over the last decades, the hydrlysis f cellulse and ligncellulsic materials has been a subject f intensive research fr the develpment f large scale cnversin prcesses that wuld be f benefit t mankind (Patel and Bhatt, 1992; Niclettal et al., 2002; Hahn-Hagerdal et al., 2006; Qu et al., 2006). These prcesses wuld amng ther things help t slve mdern dispsal prblems, reduce pllutin f the envirnment and reduce man s dependence n fssil fuels by prviding a cnvenient and renewable surce f energy in the frm f biethanl (Cwling et al., 1976). Cnversin f cellulse and ligncellulsic bimass t glucse and ther mnmeric sugars can be achieved by acid and enzyme hydrlysis (Badger, 2002; Benkun, et al, 2008, Megawati et al., 2010; Wu et al., 2010). The relative advantages f enzyme and acid hydrlysis f cellulse is a subject f cntinuing research study. The enzymatic prcess is believed t be the mst prmising technlgy because enzymatic hydrlysis is milder and mre specific and des nt prduce by prducts (Wen et al., 2004; Benkun et al, 2008). Hwever, enzymatic hydrlysis f cellulse have been bserved nt t be ecnmically viable because f high cst f enzymes, slw rate f deplymerizatin and high enzyme lading t realize reasnable rates and yields (Laykun, 1981; Aberuagba, 19997; Grhmann and Baldwin, 1995; Wyman, 1999). The advantages f acid hydrlysis fr * Crrespnding authr: A Cmparative Kinetic Study.. peel liquefactin and releasing carbhydrates prir t enzymatic treatment have been studied (Vaccarin et al; 1989; Grhmann et al., 1995; Talebnia et al., 2008). Acid hydrlysis f cellulsic bimass is relatively fast and f lw cst (Palmqvist and Hagerdal, 2000; Megawati et al., 2010). The key variables that might have impacts n the rate and extent f cellulse and ligncellulsic bimass by acid hydrlysis are temperature, acid cncentratin (r ph), ttal slid fractin (TS) and time duratin (Grhmann, et al., 1995; Talebnia et al., 2008). Several studies have been made n cellulse hydrlysis using purified raw materials especially cmmercial cellulse, but very few studies using cellulse derived frm agricultural wastes (Aberuagba, 1997; Talebnia et al., 2008; Benkun et al., 2008; Megawati et al., 2010). The bjective f this study is t examine the effects f sulfuric acid cncentratin and temperature n the hydrlysis f cellulse that is naturally ccurring in banana skin (peels), cwpea shells, maize stalks and rice husk which abund as agricultural wastes in many part f the wrld and t evaluate their kinetics. MATERIALS AND METHODS Materials: Banana skin (peels), cwpea shells, maize stalks and rice husk were btained frm farmers in Ogbms, Nigeria. Sulfuric acid (specific gravity 1.8; 98% purity) and Diethyl ether which are prducts f E. Merck (Darmstadt Germany) were purchased frm a chemical stre in Ibadan, Nigeria. These were used fr the remval f extractives. Other chemicals used were f analytical r bichemical grade. Pretreatment f Agricultural Waste: Samples f each agricultural waste (i.e. banana skin, cwpea shells, maize stalks and rice husk) were sun dried and then reduced t very small sized particles by grinding, using a serrated disk grinder. The particles were then sieved t btain an average particle size f 300 µm fr each sample. Islatin f Cellulse frm Agricultural Waste: Cellulse was islated frm each sample f agricultural waste using the mdified prcedure described by Laykun (1981). Diethyl ether (20 ml) was added t each sample (10 g) f agricultural waste in a 250 ml Erlenmeyer cnical flask s as t remve the extractives. The resultant residue (free f extractives) was filtered and washed thrughly with sterile distilled water. T the washed residue was added 20 ml f 14M sulfuric acid which then disslved the cellulse and hemi cellulse leaving lignin as a hard precipitate. Lignin was filtered ff 532 and 8M sdium hydrxide slutin was added t the filterate t btain a residue that was predminantly cellulse, while hemi cellulse remained in slutin. The slutin was filtered and the resultant cellulse residue was then washed thrughly with sterile distilled water until a neutral ph was btained. The cellulse residue was then dried at 80 C in an ven until a cnstant weight was btained fr subsequent hydrlysis. Experimental Design fr Acid Hydrlysis f Cellulse:T each sample f the cellulse (5 g) btained frm the agricultural wastes (banana skin, cwpea shells, maize stalks and rice husk) was added 50 ml f cncentrated sulfuric acid (1.5 mles/dm 3 ) in a 250 ml cnical flask which served as a batch reactr and placed in a gyratry shaker set at a temperature f 70 C with an agitatin speed f 150 rpm. This peratin was carried ut fr 2 h, and at intervals f 30 min, samples were withdrawn t determine the glucse cncentratin. The experiment was cnducted at ther temperatures f 80, 90,100 C and sulfuric acid cncentratins f 2.5, 3.5 and 4.5 mles/ dm 3, respectively. Determinatin f Glucse Cncentratin: The reducing sugar cntent (glucse) was determined by the DNS methd with glucse as standard (Miller, 1959; Marsden et al., 1982). Absrbance was measured at 540 nm. Hwever, the DNS reagent was mdified accrding t Mwesigye (1988). Tw hundred grams f ptassium sdium tartarate (Rchelle salt) were disslved in 200 ml f sterile distilled water. Ten grams f sdium hydrxide was als disslved separately in 200 ml f sterile distilled water in a 500 ml beaker. T the sdium hydrxide slutin was added 10 g f DNS (3, 5- dinitrsalicyclic acid) and 2.52 ml (2 g) f 80% (w/v) phenl simultaneusly. After stirring t cmplete disslutin, the mixture was added t the Rchelle salt slutin. The resultant slutin was then made up t ne litre with sterile distilled water. This mixture gave the stck f the mdified DNS reagent cntaining 1% (w/v) DNS acid, 0.2% (w/v) phenl, 1% (w/v) sdium hydrxide and 20% (w/v) Rchelle salt (Mwesigye, 1988). The DNS reagent was then stred under refrigeratin in an amber clured bttle. Kinetics f Acid Hydrlysis: The change in the cncentratin f waste cellulse either psitively r negatively at a cnstant temperature ver a perid f time can be described by a relatinship as given in equatin (1): C X C exp(kt) (1) = A Cmparative Kinetic Study.. WhereC, the ttal initial waste cellulse cncentratin, k, specific rate cnstant (min -1 ), C X, waste cellulse cncentratin at time t (g/l), X, glucse cntent (g/l), and t, time (min). On the basis f a first-rder reactin fr the hydrlysis, equatin (1) becmes: C ln( = kt C X ) (2) Thus, equatin (2) allws the natural lgarithmic C plts f experimental values f versus C X prcess time (t ) in which straight lines btained are indicatins f the validity f first-rder reactin kinetics fr the waste cellulse acid hydrlysis. The intensity f heat n hydrlysis f waste cellulse can be described by the Arrhenius mdel such that temperature dependence f k clsely fllws the equatin: k k E exp[ ( 1 ) t] R T = a R (3) Where k, pre-expnential cnstant (min -1 ); R 533 E a, activatin energy (KJ/ml); R, ideal gas cnstant (8.314 J/ml.K); T, actual temperature (K) and t, time (min). The regressin f the natural lgarithm f the degradatin rate cnstant ( k ) against ( 1 ) in which a straight line curve is btained indicates that the Arrhenius mdel was fulfilled and slpe f this E curve (Arrhenius plt) is equal t a and allwed calculatin f the activatin energy. RESULTS AND DISCUSSION The percentage cellulse yield frm each f the agricultural waste are 28.4%, 37.2%, 56.7% and 31.5% fr banana skin, cwpea shells, maize stalks and rice husk, respectively. Benkun et al. (2009) btained 60.12% cellulse frm the acid hydrlysis f wheat straw. The effect f temperature n glucse yield frm acid hydrlysis f wastes cellulse frm banana skin, cwpea shells, maize stalks and rice husk is shwn in Fig.1. R T Frm Fig 1, it is seen that the glucse yield frm each f the agricultural waste cellulse increased with increase in temperature. A similar bservatin has been reprted (Aberuagba, 1997). Talebnia et al. (2008) reprted that in the acid hydrlysis f range peels at lw temperature range, sugar yield increased with increase in temperature and at very high temperature range, sugar yield declines. Hwever, Megawati et al. (2010) reprted that in the acid hydrlysis f rice husk, at high temperature range ( C), ttal sugar cncentratins increased with increase in temperature. Laykun (1981) has als bserved an increase in glucse yield with temperature fr acid hydrlysis f saw dust. Furthermre, the yields f glucse frm wastes cellulse f banana skin ( %) and maize stalks ( %) are relatively cmparable at the temperature f C. Hwever, they are bth lwer than the glucse yield frm wastes cellulse f cwpea shells and rice husk, respectively. Als, the glucse yield btained frm wastes cellulse f cwpea shells (0.64%) and rice husk (0.57%) are relatively cmparable at lwer temperature range f 70 C, hwever, the yields frm wastes cellulse f A Cmparative Kinetic Study.. cwpea shells ( %) are higher than the yields frm rice husk ( %) at higher temperature range f C. Aberuagba (1997) reprted a glucse yield f % frm wastes cellulse f maize cbs and % frm grundnut shells in an acid hydrlysis at a temperature range f C and 2.5M sulfuric 534 acid cncentratin. Megawati et al (2010) reprted a sugar yield f 12.70% at a temperature f 220 C. Fig 2 shw the effect f acid cncentratin n glucse yield frm the acid hydrlysis f waste cellulse btained frm banana skin, cwpea shells, maize stalks and rice husk, respectively. The results revealed that in all the different waste cellulse cnsidered, there was a general increase in glucse yield as the acid cncentratin increased in the range mle/dm 3. Hwever, there was a decline in yield frm an acid cncentratin f 3.5 t 4.5 mles/dm 3. A similar bservatin has been reprted fr the acid hydrlysis f cellulse frm maize cbs and grundnut shells (Aberuagba, 1997). This bservatin culd be attributed t the fact at high acid cncentratin and relatively high temperature; glucse can be cnverted t rganic acid which led t a decrease in glucse cncentratin (Aberuagba, 1997). This suggests that maximum glucse yield culd be btained at lw t mderate acid cncentratin. Talebnia et al. (2008) reprted that at lw acid cncentratin and lw temperature, sugar yield increases with increase in dilute acid cncentratin. The glucse yield btained frm wastes cellulse f banana skin (0.20%) and maize stalks (0.20%) at acid cncentratin f 1.5 mles/dm 3 are relatively cmparable. Hwever, the yield btained at 2.5 t 4.5 mle/dm 3 sulfuric acid cncentratin frm wastes cellulse f maize stalks ( %) is higher than that frm banana skin ( %). The yields f bth wastes cellulse at an acid cncentratin range f mles/dm 3 are generally lwer than that frm bth cwpea shells and rice husk, respectively. The glucse yield frm wastes cellulse f cwpea shells (0.64%) and rice husk (0.57%) at 1.5 mle/dm 3 sulfuric acid cncentratin are relatively cmparable. Hwever, at an acid cncentratin range f mles/dm 3, the yield frm wastes cellulse f cwpea shells ( %) is higher than that frm rice husk ( %). Aberuagba (1997) reprted a glucse yield f % frm wastes cellulse f maize cbs and % frm grundnut shells in an acid hydrlysis with a sulfuric acid cncentratin range f M, respectively. Rahman et al. (2006) als reprted that the acid hydrlysis f il palm empty fruit bunch with acid cncentratin f 2-6% prduced a sugar yield f 31.74%. An integrated pseud first- rder rate kinetics (equatin 1) was applied t the experimental result data btained fr banana skin, cwpea shells, maize stalks and rice husk, respectively, at a temperature range f C and acid cncentratin f 1.5 C mles/dm 3. The plt f ln ( ) versus C X time (t) gave a straight line fr each f the agricultural waste cellulse as shwn in Figs 3 6, with the specific rate cnstant k estimated frm the slpe. The straight line btained in Figs 3-6 fr temperature ( C) investigated suggests a first rder rate f glucse frmatin frm banana skin, A Cmparative Kinetic Study.. cwpea shells, maize stalks and rice husk hydrlysis by sulfuric acid. The specific rate cnstant values btained frm Figs. 3-6 were fitted t Arrhenius equatin (equatin 3) and the activatin energies were estimated frm the slpe f the plt f ln k versus ( 1 ) as shwn in Fig.7. A value f T KJ/gmle, KJ/gmle, KJ/gmle and KJ/gmle were btained fr banana skin, cwpea shells maize stalks and rice husk, respectively. The difference in the activatin energies between these fur agricultural wastes cellulse can be attributed t difference in their degree f plymerizatin and crystallinity (i.e. structural features). Crystallinity values have been reprted t vary widely with a value f 73% in cttn linters and 29% in maize cbs (Ghse, 1956, Aberuagba, 1997). Furthermre, it has been reprted 535 that even when the ultimate chemical cmpsitin f tw cellulsic materials is apprximately the same, their respnse t cellulse attack can be surprisingly different (Ghse, 1956, Aberuagba, 1997). The activatin energy values fr the fur agricultural waste cellulse suggests that the ease with which hydrlysis can ccur between the fur agricultural waste can be arranged in this rder: Rice husk cwpea shells Banana skin maize stalks. Activatin energies f 26.6 KJ/mle, 45 KJ/mle, KJ/mle, KJ/mle, KJ/mle KJ/mle and KJ/mle have crrespndingly been btained fr the acid hydrlysis f sawdust, maize cbs, grundnut shells, sunflwer seed hull, crn cb, crn fiber (a c-prduct f crn wetmilling) and rice husk (Laykun, 1981; Aberuagba, 1997; Saracglu et al., 1998; Msier et al., 2002; Megawati et al., 2010). A Cmparative Kinetic Study Cnclusin: The kinetics f cncentrated acid hydrlysis f banana skin, cwpea shells, maize stalks and rice husk can be quantitatively described by a pseud first-rder rate f hmgenus reactin. Kinetic cnstant can be expressed by Arrhenius equatin with activatin energies f 39.60, 37.83, and KJ/mle fr sulfuric acid hydrlysis f cellulse frm banana skin, cwpea shells, maize stalks and rice husk, respectively. Temperature and acid cncentratin strngly influences the rate f cellulse hydrlysis and thus the glucse yield. Thus, frm this wrk cupled with results f ther researchers, it seems pssible t ttally cnvert agricultural wastes int useful prducts fr the benefit f mankind. REFERENCES Aberuagba, F. (1997). The kinetics f acid hydrlysis f wastes cellulse frm maize cbs and grundnut shells. Prceedings f the 27 th annual cnference f the Nigerian sciety f chemical Engineers Nv 13-15, 1997.Pp Ander, P. and Ericsn, K.E. (1983). Micrbial delignificatin f ligncellulsic materials, Prceedings f a cst wrkshp, Zurich, Switzerland (Ferranti, M.P and Fichter, A. Eds) Pp Anex, R., Lynd, L., Laser, M., Heggenstaller, A; Liebman, M. (2007). Ptential fr enhanced nutrient cycling thrugh cupling f agricultural and bienergy systems. Crp Sci. 47:1327. Badger, P.C. (2002). Ethanl frm cellulse: a general review in Trends in New crps and New uses, Janick, J. and Whipkey, A., (Ed) Alexandria, VA: ASHS Press. Pp Benkun, QJ Xiangrng, C., Fei, S.. Yi, S. and Yinhua, W. (2009). Optimizatin f enzymatic hydrlysis f wheat straw pretreated by alkaline perxide using respnse surface methdlgy. Ind. Eng. Chem. Res. 48: Caritas, U.O. and Humphrey C.N (2006). Effect f acid hydrlysis f Garcina Kla (bitter kla) pulp waste n the prductin f CM-cellulse and β- glucsidase using Aspergillus niger. Afri J. Bitechnl. 5: Cwling, E.B and Kirk, T.K. (1976). Prperties f cellulse and ligncellulsic materials as substrate fr enzymatic cnversin prcesses. Bitechnlgy and Biengineering sympsium series, New Yrk, 6: Ghse, T.K. (1956). Cellulse bisynthesis and hydrlysis f cellulsic substances. Advances in Bichem. Eng. 6:39-76 Grhmann, K. and Baldwin, E.A. (1992). Hydrlysis f range peel with pectinase and cellulase enzymes. Bitechnl Lett. 14: Grhmann, K., Camern, R.G and Buslig, B.S. (1995). Fractinatin and pretreatment f range peel by dilute acid hydrlysis. Biresur. Technl 54: Hahn-Hagerdal, B., Galbe, M., Grwa-Gruslund M.F., Liden, G. and Zacchi, G. (2006). Biethnl-the fuel f tmrrw frm the residues f tday Trends Bitechnl. 24:549. Jhn, R.P., Nampthiri, K.M., and Panday, A. (2007) fermentative prductin f lactic acid frm bimass: an verview n prcess A Cmparative Kinetic Study.. develpments and future perspectives. Appl Micrbil. Bitechnl. 74:524. Laykun, S.K (1981). Kinetics f acid hydrlysis f cellulse frm saw dust, Prceedings f the 11 th annual cnference f the Nigerian sciety f chemical Engineers. Pg Lynd, I.R., Weimer, P.J., Van Zyl, W.H., and Pretrius, I.S. (2002). Micrbial cellulse utilizatin: fundamentals and bitechnlgy. Micrbil Ml. Bil Rev. 66:506. Marsden, W., Gray, P., and Quinlan, M. (1982). Evaluatin f the DNS methd fr analyzing ligncellulsic hydrlysate. J. Chem. Tech. Bitechnl. 32: Megawati, W.B., Hary, S. and Muslikhin, H. (2010). Pseud-Hmgenus kinetic f di
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