Liquid-Liquid Equilibrium Data, Viscosities, Densities, Conductivities, and Refractive Indexes of Poly (vinyl pyrrolidone)+ tri-sodium Citrate + Urea Aqueous Two-Phase Systems at Different pH

Abstract The present study investigated liquid-liquid equilibria of polyvinylpyrrolidone (PVP) K30 + tri-sodium citrate + urea (5% and 10% mass) aqueous two-phase systems at 25°C and pH values of 6.2, 7.4, and 10.0. Results showed that the binodal was displaced toward higher concentrations as the urea concentration increased. The effect of pH, polymer/salt (w/w) ratio, urea concentration, tie line length, and slope of tie line on the partition behavior of urea was examined. The viscosity, density, electrical conductivity, and refractive index of PVP (K30) + tri-sodium citrate + urea + water two-phase systems were measured versus pH value. The relation between tie line length and the density and viscosity of the aqueous two-phase systems was also examined.