Effect of temperature on the salting-out effect and phase separation in aqueous solutions of sodium di-hydrogen phosphate and poly(propylene glycol)

Phase diagrams and liquid–liquid equilibrium (LLE) data of the aqueous poly(propylene glycol) (PPG) + sodium di-hydrogen phosphate have been determined experimentally at 298.15, 303.15, 308.15, 313.15 and 318.15 K. The effect of temperature on the binodal curves and tie-lines has been studied and it was found that, an increase in temperature caused the expansion of two-phase region. It was also found that, at higher temperatures, the lower concentration of salt is in equilibrium with a certain concentration of PPG. The effect of temperature on the phase-forming ability in the investigated system has been studied based on a salting-out coefficient obtained from fitting the tie-line data to a Setschenow-type equation for each temperature.