Measurement and correlation of liquid–liquid equilibria of the aqueous two-phase system polyvinylpyrrolidone–sodium dihydrogen phosphate

Liquid–liquid equilibrium (LLE) data of the aqueous polyvinylpyrrolidone (PVP)–sodium dihydrogen phosphate system has been determined experimentally at 293.15, 298.15 and 303.15 K. Furthermore, the extended form of the Flory–Huggins and the Chen-NRTL equations with an electrostatic term (the Debye–Hückel and the Pitzer–Debye–Hückel) were used to correlate the phase behavior of this system. For temperature dependency of the parameters of the Flory–Huggins model a simple equation was assumed. Good agreement was obtained with the experimental data with both models, specially using the model of Chen-NRTL with PDH equation.