Liquid−liquid equilibria (LLE) of the poly(ethylene glycol) dimethyl ether 2000 (PEGDME2000) + dipotassium oxalate + H 2 O system have been determined experimentally at T = (298.15, 303.15, 308.15, and 318.15) K. The effect of temperature on the binodal curves and tie-lines has also been studied. The Graber et al., Merchuk, and empirical equations were used to correlate the binodal data of this system with the temperature dependence expressed in the linear form with (T − T 0 ) K as a variable. Furthermore, we used the Othmer−Tobias and Bancroft and a temperature-dependent Setschenow-type equation for the correlation and prediction of the liquid−liquid phase behavior of the studied system. The effective excluded volume (EEV) values obtained from the binodal model for this system and other aqueous PEGDME2000−salt systems were determined, and the relation between these values and salting-out ability of different salts was discussed. Also, the effects of type of the polymers PEGDME2000 and PEG2000 on LLE are discussed. Finally, the free energies of cloud points for this system were calculated. According to the results it was concluded that the increase of the entropy is a driving force for the formation of the studied aqueous two-phase system (ATPS).
Curcumin is a natural product traditionally used as a spice that has a great potential for being used as a drug of natural origin. The partitioning of curcumin in an aqueous two-phase system composed of the aqueous solutions of poly(vinylpyrrolidone) 10000 (PVP 10000 ) and trilithium citrate was studied at T = 298.15, 308.15, and 318.15 K. The binodal and tie-line compositions were measured and modeled. The tie-line compositions were modeled successfully using osmotic virial and especially e-Wilson and e-NRTL models, where the deviation percent between the calculated and the experimental tie-line mass fractions was found to be in the range of 0.005−0.03 for the e-Wilson model and 0.02−0.05 for the e-NRTL model, which are in the range of the experimental uncertainties. The high values of the partition coefficient (D) showed the high tendency of curcumin to be extracted from a salt-rich to a polymer-rich phase. The minimum and maximum D values of 11.7 and 21.2 were found at T = 318.15 and 298.15 K, respectively. Moreover, the minimum and maximum extraction efficiencies (E%) of ∼81 and 90% were shown at T = 318.15 and 298.15 K, respectively. Both obtained D and E% values decreased by increasing the temperature, and the best partitioning results were obtained for the tie-lines presented in the middle range of the tie-line compositions.
The liquid−liquid equilibrium data of the ternary systems containing 1-propanol/2-propanol + dipotassium tartrate/potassium sodium tartrate + water have been measured at T = 298.15 K. To fit the binodal data an empirical equation was used. The length of the alcohol chain, polarity of the alcohol, and the type of salt are the parameters that have influence on the phase behavior of these systems have been studied. In addition, the obtained experimental tie-line data were fitted using the Setschenow-type equation. Finally, the plait points of these systems were calculated.
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