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Kinetic study of oil extraction from olive foot cake

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GRASAS Y ACEITES, 57 (2), ABRIL-JUNIO, , 2006, ISSN: Kintic study of oil xtraction from oliv foot cak By S. Mzian, H. Kadi 1 * and O. Lamrous 2 1 Laboratoir d Chimi Appliqué t d Géni Chimiqu,
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GRASAS Y ACEITES, 57 (2), ABRIL-JUNIO, , 2006, ISSN: Kintic study of oil xtraction from oliv foot cak By S. Mzian, H. Kadi 1 * and O. Lamrous 2 1 Laboratoir d Chimi Appliqué t d Géni Chimiqu, Faculté ds Scincs, Univrsité Mouloud Mammri, Tizi-Ouzou, Algéri. 2 Laboratoir d Physiqu t d Chimi Quantiqu, Faculté ds Scincs, Univrsité Mouloud Mammri, Tizi-Ouzou, Algéri. *Corrsponding author: H.Kadi, B.P 70, Post Annan, TIZI-OUZOU, ALGERIA. -mail: RESUMEN Estudio cinético d la xtracción d acit d orujo La cinética d xtracción d acit d orujo pud sr xplicada por un modlo basado n dos tapas. La primra tapa corrspond a un simpl lavado dl acit d la suprfici d las partículas. En la sgunda tapa, la xtracción sta controlada por dos mcanismos: difusión lnta dsd las células rotas y difusión muy lnta dsd las células intactas. Los coficints cinéticas d st modlo matmático s calculan usando los rsultados xprimntals obtnidos con hxano y alcohol tílico comrcial para difrnts tamaños d partícula. PALABRAS-CLAVE: Acit d orujo - Difusión - Extracción - Solvnt. SUMMARY Kintic study of oil xtraction from oliv foot cak Th kintics of oil xtraction from oliv foot cak can b xplaind by a modl basd on two stags. Th first stp corrsponds to a simpl washing of th oil from th particl surfac. In th scond stp, th xtraction is controlld by two mchanisms: slow diffusion from brokn clls and vry slow diffusion from intact clls. Th kintic cofficints of this mathmatical modl ar calculatd using th xprimntal rsults obtaind from hxan and commrcial thyl alcohol for diffrnt particl sizs. KEY-WORDS: Diffusion - Extraction - Oliv foot cak oil - Solvnt. 1. INTRODUCTION Th oil of oliv foot cak is of important conomic intrst. For this rason, much work has bn don to improv th yild of this oil rcovrd by solvnt (Cana Munoz t al., 1976; Kmiciak t al., 1991; Kadi and Fllag, 2001). Numrous thoris hav bn proposd to xplain th mchanism of oil rcovry by solvnt from oil caks and oilsds. So, th ffct of th natur of th solvnt (Hnsarling and Jack, 1983; Kmiciak t al., 1991), particl siz (Othmr and Agarwal, 1955; Bckr and McK, 1978; Patriclli t al., 1979; So and Macdonald, 1986; Wis and Snydr, 1987; Schnbrgr t al., 1988), tmpratur (Bckr and McK, 1978; Patriclli t al., 1979; So and Macdonald, 1986; Schnbrgr t al., 1988) and moistur (Cana Munoz t al., 1976, Patriclli t al., 1979) on th yild has bn dmonstratd. Howvr, it is worth mntioning that th molcular diffusion dos not corrspond to xprimntal rsults (Othmr and Agarwal, 1955; Patriclli t al., 1979; So and Macdonald, 1986). On th contrary, Schnbrgr t al. (1988) showd that th kintics of oil xtraction by solvnts in hazlnut clls which ar not dtrioratd is controlld by diffusion kintics. It sms that th bst mchanism adaptd to oil caks is dscribd in two stags. Th first is rlativ to th oil bing at th grain surfac and rcovrd by a simpl washing and th scond stag corrsponds to a diffusion procss which is abl to tak plac in on or two phass. Although many studis hav bn dvlopd on oil xtraction from oliv foot cak, not on of thm is basd on th quations of mass transfr. Our objctiv in this papr is to prsnt a study of th kintics of solvnt xtraction of this rsidual oil in an agitatd isothrm ractor working in a discontinuous rgim. 2. MATERIAL AND METHODS Th oliv foot cak usd was takn from a continuous cntrifugation systm. Its initial moistur contnt was 48.0% which was rducd by drying to an intrval ranging btwn 5 and 10%. Th oil contnt of th sampl was 6.50%. It was dtrmind by an xhaustiv xtraction using hxan in a soxhlt apparatus. Th sampl was ground using an lctric cral mill with millstons S.A.M.A.P typ F100. Avrag 175 S. MEZIANEA, H. KADI AND O. LAMROUS particl sizs obtaind wr: 1.69; 1.03 and 0.69 mm. Th rsults ar summarizd in tabl 1. Th batch xtraction was carrid out in a cylindrical ractor of 600 ml ( r = 85 mm; h = 106 mm) supplid with a mchanical agitator. Th agitation turbin in stainlss stl was quippd with 4 blads tiltd to 45 ( b = 51 mm). Th solidliquid sparation was prformd undr rducd prssur. Th misclla was distilld by mans of a rotary vaporator. Th xtractions hav bn carrid out undr th following conditions: L kintic study: solvnt-to-solid ratio, = 4; S xtraction tmpratur, T = 25 C; agitation spd, V a = 800 rpm; xtraction tim, t: from 0 to 60 min L study at quilibrium: = 4; T = 25 C; t = 150 hours S Th wight of th cak submittd to xtraction was always 50 g. Each yild valu calculatd was th avrag of thr tsts for th kintic study and fiv tsts for th quilibrium study. Th HPLC grad hxan and thyl alcohol 96.0 % (v/v) purity wr usd in all oil xtraction xprimnts. Thir avrag dnsitis wr and 0.806, rspctivly. Ths solvnts ar Prolabo products. 3. MATHEMATICAL MODEL Th mchanism of oil xtraction from olaginous sds assums that th oil transfr from th solid phas to th liquid phas is carrid out in two simultanous procsss: a prdominant washing procss and a diffusion procss. Patriclli t al. (1979), working on unintrruptd oil xtraction from sunflowr sds, proposd a modl whr th concntration C t at any tim is givn by th quation: C t = C w (1 xp (-k w t)) + C d (1 xp (-k d t)) whr, C w : oil concntration to quilibrium in th solvnt du to th washing stp C: d oil concntration at quilibrium in th solvnt du to th diffusion stp k w : mass transfr cofficint for th washing stp k d : mass transfr cofficint for th diffusion stp Th final oil concntration in misclla at tim qual to infinity: C = C w + C d Th modl applid by So and Macdonald (1986) for th oil xtraction from canola (rapsd) drivs from th prcding modl. It considrs th possibility of two distinct stps of diffusion insid th sd. slow, unhindrd diffusion of oil hld in th rupturd clls of th sd a vry slow, hindrd diffusion of oil hld within unrupturd clls of th sd. Th transfr quation is thn writtn: C t = C w (1 xp (-k w t)) + C d1 (1 xp (-k d1 t)) + + C d2 (1 xp (-k d2 t)) at quilibrium C = C w + C d1 + C d2 Th valu C corrsponds to th concntration at quilibrium. It has bn dtrmind xprimntally. In this study, w hav thn trid to dtrmin th applicability of ths two mathmatical modls to th oil xtraction from oliv foot cak by studying th xtraction yild according to tim for diffrnt particl sizs and solvnts. This yild ρ t, calculatd on a dry basis, can b xprssd by th quation: Modl I: ρ t = ρ t - ρ w xp (-k w t) - ρ d xp (-k d t) with ρ = ρ w + ρ d Modl II: ρ t = ρ - ρ w xp (-k w t) - ρ d1 xp (-k d1 t) - ρ d2 xp (-k d2 t) with ρ = ρ w + ρ d1 + ρ d2 whr, ρ : oil yild of th xtraction to quilibrium ρ w : oil yild to quilibrium for th washing stp ρ: d oil yild to quilibrium for th diffusion stp 1 and 2: rlativ indxs at th first and th scond diffusion Th oil yilds at quilibrium according to th particl siz and natur of th solvnt (ρ ) hav bn dtrmind xprimntally. Th kintic cofficints k w, k d1 and k d2 as wll as th oil yilds at quilibrium ρ w, ρ d1 and ρ d2 hav bn calculatd numrically with a non-linar last squars fitting mthod using program Origin 7.0. Tabl 1 Charactristics of sampls and yilds of xtraction at quilibrium Avrag diamtr of sampl (mm) Moistur (%) Oil contnt Hxan 5.82 at quilibrium (%)* Ethyl alcohol 96.0% 5.22 * calculatd on dry basis 176 GRASAS Y ACEITES, 57 (2), ABRIL-JUNIO, , 2006, ISSN: KINETIC STUDY OF OIL EXTRACTION FROM OLIVE FOOT CAKE 4. RESULTS AND DISCUSSION 4.1. Study at quilibrium Tabl 1 prsnts th oil yild at quilibrium according to granulomtry and th natur of th solvnt. Ths rsults obtaind aftr a contact tim of 150 hours show that th yild is indpndnt of th particl siz. This conclusion is in agrmnt with that of So and Macdonald (1986) who studid th oil xtraction from canola (rapsd). Ths authors showd that th quilibrium is rachd aftr about 3 days for 0.06 mm thicknss and aftr 6 days for 0.76 mm thicknss. As shown in Tabl 1, hxan appars to b th solvnt that givs th bst yild. It xtracts approximatly 10.3% mor fat mattr than thyl alcohol 96.0%. Figur 1a Fit of modl I to th xtraction with thyl alcohol 96.0% showing th ffct of particl siz 4.2. Kintic Study Th data from our xprimnts ar first fittd with mathmatical modl I basd on a washing stag and a singl diffusion. Figurs 1a and 1b show th xtraction graphs with thyl alcohol 96.0% and hxan according to th contact tim and for diffrnt particl sizs. A first visual analysis spcially indicats a good fit for th low granulomtris. Modl II, which implis two diffusion stags, givs bttr rsults as shown in figurs 2a and 2b. Ths curvs also show that th oil yild incrass vry quickly with tim at th bginning of th xtraction. This rapid incras could b xplaind by th fact that this first stag which in gnral lasts 3 to 11 min for modl I and on halfminut to 6 min for modl II corrsponds to th washing procss from th grain surfac. Th scond stag is charactrizd by a yild which incrass lss and lss rapidly. Thn, th xtraction is only assurd by diffusion which is an incrasingly slow procss. Tabls 2 and 3 giv th calculatd valus of th kintic cofficints of th washing and diffusion stags for diffrnt particl sizs and diffrnt Figur 1b Fit of modl I to th xtraction with hxan showing th ffct of particl siz solvnts. On can obsrv that xtraction by washing is mor ffctiv than that rsulting from diffusion. Th dtrmination cofficints r 2 indicat a good fit for modl I (0.987 r ) and a vry good fit for modl II (0.991 r ). In th cas of modl I, th kintic cofficints of washing ar 33 to 126 tims gratr than for th diffusion stag. For modl II, th washing cofficints ar 9 to 151 tims gratr than thos of th first diffusion and thos for diffusion 1 ar 7 to 47 tims gratr than for diffusion 2. It should b notd that all th cofficints of washing and diffusion of modl II ar highr than thos of modl I, for a givn solvnt and granulomtry. Tabl 2 Cofficints of mass transfr and yilds at quilibrium of modl I MODEL I Avrag Cofficints of Yilds at Cofficints of Solvnt diamtr mass transfr (min -1 ) quilibrium (%) dtrmination (mm) k w k d ρ w ρ d r 2 Ethyl alcohol % Hxan GRASAS Y ACEITES, 57 (2), ABRIL-JUNIO, , 2006, ISSN: S. MEZIANEA, H. KADI AND O. LAMROUS Tabl 3 Cofficints of mass transfr and yilds at quilibrium of modl II MODEL II Avrag Cofficints of Yilds at Cofficints of Solvnt diamtr mass transfr (min -1 ) quilibrium (%) dtrmination (mm) k w k d1 k d2 ρ w ρ d1 ρ d2 r 2 Ethyl alcohol % Hxan Figurs 1a, 1b, 2a and 2b also indicat that th particl siz has a grat influnc on th xtraction; th yild incrass whn th particl siz dcrass. This fact is confirmd by th gnral incras in all kintic cofficints givn in tabls 2 and 3. Th rsults prsntd in ths tabls show that th natur of th solvnt has an ffct on transfr cofficints. In th cas of both modls, hxan givs th bst transfr cofficints in all th stps of washing and diffusion for th sam particl siz. This is confirmd by figurs 3a, 3b and 3c rprsntd by modl II which show that, for a givn granulomtry, hxan always xtracts mor oil than thyl alcohol 96.0%. Figur 3a Fit of modl II to xtraction with 1.69 mm diamtr showing th ffct of solvnt natur Figur 2a Fit of modl II to th xtraction with thyl alcohol 96.0% showing th ffct of particl siz Figur 3b Fit of modl II to xtraction with 1.03 mm diamtr showing th ffct of solvnt natur Figur 2b Fit of modl II to th xtraction with hxan showing th ffct of particl siz Figur 3c Fit of modl II to xtraction with 0.69 mm diamtr showing th ffct of solvnt natur 178 GRASAS Y ACEITES, 57 (2), ABRIL-JUNIO, , 2006, ISSN: KINETIC STUDY OF OIL EXTRACTION FROM OLIVE FOOT CAKE 5. CONCLUSION Th study of oil xtraction at quilibrium showd that th yild aftr 150 hours of contact is indpndnt of th particl siz for a givn solvnt. It also appars that hxan is th solvnt which xtracts th most fat mattr. Th rsults producd by modl I and spcially by modl II ar in agrmnt with th xprimntal rsults. Howvr, modl I sms mor adquat bcaus it is asir to us: it rquirs lss paramtrs that modl II. In both modls, th prdominant mchanism in th xtraction procss is th washing of oil from th particl surfac. This washing which allows th rcovry of a significant quantity of oil is finishd in about 11 minuts for modl I and 6 minuts for modl II. Th xtraction is thn assurd by th diffusion procss only. It is important to point out as wll that th xtraction is influncd by particl siz and by th natur of th solvnt. Hxan givs th highst kintic cofficints in all cass. Ths cofficints incras in both modls whn th particl siz dcrass. W notic that th amount of xtractd oil during th washing stag incrass with th dcras of particl siz. For xtraction with hxan, th dcras in siz from 1.69 to 0.69 mm lads to an incras in oil yild from 42.0 to 80.0%. This variation is lss significant (25.0 to 51.0 %) in th cas of thyl alcohol. Both modls, whil giving good rsults, do not dscrib th xtraction procss such as it occurs sinc thy considr that th stps of washing and diffusion happn simultanously. Howvr, in rality, th diffusion procss of oil in a solvnt can only bgin whn th washing stp is finishd. NOMENCLATURE C t : oil concntration in th solvnt at any tim (g oil / 100 g misclla) C : oil concntration to quilibrium aftr th xtraction procss has bn compltd (g oil / 100 g misclla) C w : oil concntration to quilibrium in th solvnt du to washing stag (g oil / 100 g misclla) C d : oil concntration at quilibrium in th solvnt du to diffusion stp (g oil / 100 g misclla) h: hight of ractor (mm) k d : cofficint of mass transfr for diffusion stp (min -1 ) k w : cofficint of mass transfr for washing stp (min -1 ) S L : solvnt-to-solid ratio (ml solvnt / g solids) r 2 : cofficint of dtrmination t: xtraction tim (min) T: xtraction tmpratur ( C) V a : agitation spd (rpm) ρ t : oil yild of th xtraction at any tim (g oil / 100 g solids) ρ : oil yild of th xtraction to quilibrium (g oil ρ w : oil yild to quilibrium for washing stag (g oil ρ d : oil yild to quilibrium for diffusion stag (g oil b : diamtr of agitator blad (mm) r : diamtr of ractor (mm) 1 and 2: rlativ indxs aftr first and th scond diffusions REFERENCES Bckr W, McK AG Solvnt xtraction IV: th ffct of tmpratur on xtraction rat. J. Amr. Oil Chm. Soc. 55, Cana Munoz G, Hrmida Bun JR, Ascanio Hidalgo E Extraccion d orujos d acituna. Influncia d factors qu afctan al rndiminto n acit. Grasas y Acits 27 (5) Hnsarling TP, Jack TJ Solvnt xtraction of lipids from soybans with acidic hxan. J. Amr. Oil Chm. Soc. 60 (3) Kadi H, Fllag H Modling of oil xtraction from oliv foot cak using hxan. Grasas y Acits 52 (6) Kmiciak S, Mzian S, Kadi H, Moussaoui R Oil xtraction from oliv foot cak with acidic hxan. Grasas y Acits 42 (1) Othmr DF, Agarwal JC Extraction of soybans. Chmical Enginring Progrss 51 (8) Patriclli A, Assogna A, Casalaina A, Emmi E, Sodini G Fattori ch influnzano l strazion di lipidi da smi dcorticati di girasol. La Rivista Italiana Dll Sostanz Grass 56, Schnbrgr R, Villarrol M, Drapla N, Cair F, Castillo M Cinética d xtraccion d acit d avllana. Grasas y Acits 39 (3) So GC, Macdonald DG Kintics of oil xtraction from Canola (Rapsd). Th Candian Journal Of Chmical Enginring 64, Wis L, Snydr HE Analysis of th oil xtraction progrss in soybans: a nw continuous procdur. J. Amr. Oil Chm. Soc. 64 (3) Rcibido: Novimbr 2004 Acptado: Octubr 2005 GRASAS Y ACEITES, 57 (2), ABRIL-JUNIO, , 2006, ISSN:
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