Liquid−Liquid Equilibrium of Aqueous Two-Phase Systems of PPG₄₀₀ and Biodegradable Salts at Temperatures of (298.15, 308.15, and 318.15) K

Abstract

Liquid−liquid equilibrium data for the PPG 400 (poly(propylene glycol)) + salt (potassium citrate, potassium tartarate, potassium oxalate) + water systems have been determined experimentally at T = (298.15, 308.15, and 318.15) K. The effects of temperature on the binodal curves and tie-lines were studied, and it was observed that an increase of the temperature generally led to an increase of the biphasic area. Furthermore, the binodal curves were fitted to a five-parameter equation relating the concentrations of PPG 400 and salt. The effective excluded volume (EEV) values obtained from the binodal model were determined, and the salting-out ability of the anions follows the ordering citrate 3− > tartarate 2− ≈ oxalate 2− . Finally, the Setschenow-type and Othmer−Tobias and Bancroft equations have been successfully used to correlate the tie-line compositions.