Liquid–Liquid Equilibria of Polyvinylpyrrolidone + Several Ammonium Salts + Water Aqueous Two-Phase Systems: Experimental and Correlation

Abstract

Phase equilibrium behaviors of polyvinylpyrrolidone (PVP) + (NH4)2HPO4, (NH4)2SO4, (NH4)2CO3, (NH4)2C4H4O6, and (NH4)2HC6H5O7 + H2O aqueous two-phase systems (ATPS's) were determined at 298.15 K. A series of common phase-forming ammonium salts and the corresponding anions were discussed. Meanwhile, the temperature effect on phase equilibrium behavior for PVP (K30) + (NH4)2HPO4 + H2O ATPS was investigated at (288.15, 298.15, and 308.15) K. It was found that phase-forming abilities of the salts are in the order: (NH4)2HPO4 > (NH4)2SO4 > (NH4)2C4H4O6 > (NH4)2HC6H5O7 > (NH4)2CO3. Furthermore, a third-order polynomial equation was used to correlate the binodal data, while a simple two-parameter equation along with the Othmer–Tobias and Bancroft equations was used to correlate the tie-lines data. All equations used above were proved to be valid for the experimental data. At last, the data of critical points were obtained by an extrapolation method.