Measurement and Correlation of Equilibrium Data for Aqueous Two-phase System Ethanol+Water+K2HPO4

CHEM. RES CHINESE U. 2004, 202),195--199Measurement and Correlation of equilibriumData for Aqueous Two-phase SystemEthanol Water+ K2HPO4LiN Jin-qing, TAN Ping-hua JIN Chun-ying and LI Ming-chunCollege of Material Science and Engineering Huaqiao University, Quanzhou 362011, P.R. ChinaReceived Nov. 22 2003The isothermal solubility data of aqueous two-phase system ethanol water +K, HPO4 were determined withthe turbidity titration method at 303. 2 K. The binodal curves were described by using the Mistry equation verywell. An experimental procedure for measuring the liquid-liquid equilibrium data of the aqueous two-phase systemwas proposed in which the concentrations of the coexisting phases were determined with the corresponding densitiesof the solution. The tie lines were satisfactorily described by using the Othmer-Tobias and Bancroft equationKeywords Aqueous two-phase system, Solubility Turbidity titration LLE Ethanol, K,HPO4Article|D1005-9040(2004)02-19505IntroductionSome of the systems have proved to be efficient inThe aqueous two-phase partitioning method of partitioning processes both with biomaterials and withseparating materials of different biological origins is a metal ions. Therefore it has received more and moremethod by which two liquid phases are created from a attention from researchers. Wang 5] provided partialsingle homogeneous aqueous phase to which one or information for the systems of aqueous solutionsmore compounds are added. The additives are usually ethanol, propanol or acetone with NaCl, Mg2 SO 4either two structurally different hydrophilic polymers, Na2 SO4, (NH )SO4, and K2 HPO4 Cheluget 6 pre-such as dextran and polyethylene glyco PEG ) or a sented the system of 1-propanol with NaCl at 298Knd a salt, such as PEG and potassium phos- Zafarani-Moattar MT 78 presented the systems of Iphate. It has been observed that many solutes of large propano or 2-propanol )+ NH4 )HPO4 +H,O andmolecular weights including biomolecules such as 2-propanol+ NHH, PO4 water at 25 C. Greve 93proteins and enzymes, are distributed unevenly in presented some systems of aliphatic alcohols +salts+such systems with different components being prefer- water. Several other studies have been carried out onentially retained in one of the phases l-3. This pro- the separation of biological materials 10-12,metalvides a basis for the separationIons13-15] and other compoAlthough the phase forming agents originallyAlthough most of the published studies have beenem-focused on the partitioning distribution of the separatployed in aqueous two-phase systems are polymersed materials the equilibrium phase diagrams are inother solutes with lower molecular weights which pos- complete and the theoretical and empirical models aresess hydrogen bonds such as aliphatic alcohols and scarce. Herein we report the results of the experimenboth neutral and charged surfactants, may form tal study on an aqueous two-phase system ethanolbiphasic systems with inorganic salts. The major adwater+ K,HPO4 and the correlation of the solubilityandd om.l:L-.um data at temperaturevartages of the systems formed by aqtof 30中国煤化工ethanol and inorganic salts is low inCNMHGnoninflammable, nonemulsive and easy to handle].1MaterialsSupported by Naturd Science Foundation of Fujian Province( No. E0210022), Japan Science and Technology Corporation(.石点数揭 dence should be addressed196CHEM. RES CHINESE UVol 20Ethanol and K,HPO4 were purchased fromFor the determination of the tie lines, differentShanghai Chemical Co. ethanol. A.R. grade, 99. mixtures of known concentrations within the two-7%K,HPO4, A.R. grade, 99%). The ethanol phase area in the phase diagram were prepared. Thesewas used without further purification. K,HPO4 was mixtures were kept in the vessel at the temperature ofdried in an oven at about 383 K for 24 h and stored in (303. 2+0.1)K, stirred for 2 h, and then kept ina desiccater before use, double distilled and deionized the same water bath to allow the formation of twowater was usedaqueous phases. Having been settled for over 24 h2 Apparatus and procedurethe densities of the top and bottom phases were deter2.1 Binodal Curvemined by using 10 mL pycnometers, respectivelyThe experimental apparatus employed is essenAccording to the analysis of the phase rule of thetially similar to the one used in the literature 51. A system in the previous section, we have concludedglass vessel with a volume of 0. 05 L was used to carry that the density of the saturated solution is a singleout the phase equilibrium determination. Thefunction of the composition of any one of the threevessel was provided with an external jacket in wlcomponents and vice versa( the composition of anywater was circulated at a constant temperatureone of the three components is a single function of the(303.2+0. 1)k by using a thermostatdensity ) Thus based on the relation equations beThe binodal curve was determined by the turbidi- tween p and w; obtained with the method describedtitration method. A salt solution of a known con- in the previous section, the concentrations of thecentration was titrated with ethanol until the solution existing phases can be determined easily with the denbecame turbid which indicated the presence of a sec- sities. Furthermore the calculated concentrations ofond liquid phase. The composition of the mixture was the tie lines were verified by performing the mass badetermined by using an electric analytical balance with ances to determine if the amounts of k, HPO4 anda precision of +0 0001 from Sartorius Company ) ethanol used to create the feed phase correspondedof the mixture was determined by using a 10 mL pyc- below 0.75 relai and bottom phases. The resultThe relative error is below 0. 25 %( against the solu- thethetion net weight of 30 g ) The corresponding density shows that the error of the mass balances isnometer. The feasibility of the apparatus and the ac- Experimental Data and Correlationcuracy of this method have been confirmed previously 1 Solubility Data and Binodal Curve Correlationin our laboratory 171. For the phase diagram of theTable 1 presents the experimental data obtainedbinodal curve the Gibbs phase rule can be used to de- for the binodal curves of the ethanol+H,O+K,HPOAtermine the number of degrees of freedom. Since the system. These data were fitted by using the followingnumber of components C=3, and the numbernonlinear expression of mistry et al.[ 181phases presents P=2 when the solution was saturatedlne3=a+b√1+cvo(3)on the binomal curve, we havewhere w3 represents the mass fraction of C2HsOhF=C-P+2=3-2+2=3(1)w, represents the mass fraction of k HPOa/ The emBecause the pressure was fixed at 1 atmosphered for theand the temperature was kept constant the numberbinodal curves of 1-propanol or 2-propanol)+of degrees of freedom of the saturated solution was leftonly one and it may be the composition of any one of(NH )HPO4 +H,O systems by Zafarani-Moattas 7Jthe three components. Thus we can conclude that and PEG Na2CO3 H2o by Taboada et al. [191the density of the saturated solution is a single funcThe parameters of equation 3 along with the corre-tion of the composition of any one of the three compo-nents, that isthe investigated systems are given in Table 2. theP=fw1corrOn t中国煤化 quation(1)is0.99where p represents the density of the solution w; isdeviations, it is shownthe composition of any one of the three components. that ICNMHtorily used to correlateThe exact relation between p and w, will be given inthe binodal curves of the system. Fig. 1 shows thecorrelation between the experimental data and the fitth方级LiN Jin-qing et al197Table 1 Binodal Data of mass fractions for system K,HPO 1 ) H,a2)+Chs oh 3 )at 303.2K0.85890.00091.06620.14290.66370.85620.00100.30040.66650.18330.87510.00300.37220.62481.0840.66400.87390.00320.36120.66520.88120.59971.096116990.6660.16360.88620.40660.58801.11500.66720.14681.11670.18870.009645751.133419820.66580.00990.45650.53361.13500.6660.91160.01390.49541.154521580.91780.01640.50711.18260.92370.01980.527324330.66290.09380.92550210.53350.44530.66120.93260.02510.54980.657807580.93510.02610.55220.4211.219827270,65620,0710.94690.03450.5780.38741.30310.34070.62580.03360.95490.03790.58510.37700.606302410.96290.045535220.37320.60440.02250.97110.05180.61220.33601.35140.98770.06400.62780.30820.59880.99280.07770.64120.28111.37560.09510.254138440.40330.58221.03390.11140.2310.56591.06060.1353Where w. w and w are the mass fractions of K HPO4, H,o and ChS OHTable 2 The parameter values of equation 1ParametersCorrelation coefficien R)Erro SD)0.269883.5587423.01820.999The coefficients of equation(4) along with thecorresponding deviations for the investigated systemsare given in Tables 3 and 4. On the basis of the obtained deviations it is shown that equation(4)canbe satisfactorily used to correlate the relation betweenthe density and the composition of the components ofthe system. Fig. 2 and Fig 3 show the correlation between the experimental data and the fitting equationThus once the density of the solution is measuredFig. 1 The binodal curves for ethanol K2 HPO4 H,Othe concentration of the mixture can be calculatedsystem at 303. K.2 Density Curves and CorrelationThe relation between the density and the composition of the components is described by an empiricallinear equation as follo=a+bl(p^)+1(p)+1(p)+l(p)中国煤化工(4)CNMHGwhere w represents a conversion of the mass fractionof C2HSOH or K,HPO4 that is w=100w'P is aFig. 2 The curves of the densities of the system againstconversion density of the corresponding system thatK HPO4 at 303. K.isp=10方数据e Experimental : -calculated from equation ( 4)198CHEM. RES CHINESE UVol 20Table 3 The parameter values of equation( 4)Parameter715190.13412184385.38053513.698821324.84002531631.8534447395,19195039.25975Table 4 The values of correlation coefficients and errors of equation (4)Correlation coefficien (R)Ip0.479060.24081100.10.0ln(102P)Fig 3 The curves of densities against CH OH forFig 4 The plot of the tie lines for system ethanolthe system at 303.2 KKHPO H,O system at 303.2 K.Experimental ; -calculated from equation (4)3 LLE Data and Correlation(6)According to the experimental procedure pro-posed by the authors in the previous section thee denwhere k, n, kI and r represent the parameters ofsities of the top and bottom phases were measured and the empirical equations. Superscripts"t"and"bthe liquid-liquid equilibrium data of the system were stand for the top( ethanol-rich phase and the bottomobtained. The densities and lle data of the tie lines water-rich)phase respectivelyat 303. 2 K are shown in Table 5 and the plot of theThese equations have been used for the assess-tie lines is shown in Fig 4. The correlation equations ment and correlation of the tie line compositions of 1given by Othmer Tobias equation( 5 ) and Bancroft propanol or 2-propanol)+(NH )HPO4+H,0,1I equation (6)] were used to correlate the tie line propanol+ NHH, PO4+H, 07] and PEG+Na, COcompositions+H2(19(5)Table 5 The tie line data of the mass fractions for the K2 HPOK 1)+H2a2 )+ C2h oh 3 )system at 303. 2 KInitial compBottom phase0.24800.20650.90950.01270.48940.49790.396258800.01580.20030.22910.02130.52970.4400.36980.2170.20020.93170.54301.33310.36l10.17850.93900.02980.55760.35310.61680300.20550.94480.03380.56831.31540.34720.62020.03260.18220.95250.0.3940.58130.37941.30490.33900.62470.03630.97730.05900.3151063640.0485The plots of the linear dependences ofaH中国煤化工 ata and thee equations.TablCNMHGfor equations(5)andagainst(6, and the coefficient of linear correlation R. It1-xshows that equations (5)and(6) provide useful emare shown in Fig. 5 and Fig. 6, respecpirical mathematical models for the analysis of the e-tively,w数搪 cates an adequate consistency bquilibrium data of the aliphatic alcohols h,o+LiN Jin-qing et al199It systems studithe system can be satisfactorily described by Mistry sequation and the tie lines for the system can be satisfactorily described by Othmer-Tobias and Bancroft e1.7quaReference1 J Vernau J., Kula M. R., BiotechnoL. Appl. Biochem.,199012(3):3972 Greve A and Kula M. R., Fluid Phase Equilibria, 1991, 621.8):53lg[(1-w)/wI 3] Berlo M,, Gude M. T. and Wielen L,A. M,,etEng.Chem.Res.,1997,36(6):2473Fig. 5 The lines for lg( 1-w2 yw2 against4 Louwrier A., Biotechnology Techniques, 1998, 12(05), 363ld (1 -w3yw3 ][5] Wang Zhihua, Ma Huimin, Ma Quanli et al. Chinese Jour● Experimental dal of Applied Chemistry, 2001, 18(3),173[6] Cheluget E. L., Marx S. Weber M. 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M. et al., MicrochemicalJournal,1998,60(02),143lgkn or r[14] Li Quan-Min Zhang Zhi-jie, Geng Xin-hua et al., chineseOthmer tobias0.72400.417340.9990.00641Journal of Applied Chemistry, 2001, 18(3), 2410.79170.308240.9990.00544[15] Gao Yun-tao, Wu Li-sheng Wang Wei, Chemical Journal ofConclusionsAnalytical Chemistry, 2001, 29(8)90116] Gao Yun-tao, Wang Wei, Chemical Research and AppliactionFor system ethanol water K HPO4 system202,14(3),320the binodal curves and the tie line data have been de- 17 Zeng Ying, Lin Jing-qing, Deng Jun-fang, Journal of huaqiaotermined at 303. 2K by following an experimentalUniversity, Natural Science edi2002,23(1),87procedure proposed by the authors in which the con18 Mistry S. L, Kaul J. A, Merchuk J. Cal of chromatography A,1996,741(2),151centrations of the[19] Taboada M. E., Asenjo J. A.. Andrews B. A., Fluid Phasewith the corresponding densities of the solution. ItEquilib,2001,180,273was found that the binodal curve for中国煤化工CNMHG