Phase Equilibria and Salt Effect on the Aqueous Two-Phase System of Polyoxyethylene Cetyl Ether and Sulfate Salt at Three Temperatures

Abstract

Polyoxyethylene(20) cetyl ether (C56H114O21, POELE20) and three sulfate salts (Li2SO4, ZnSO4, and MgSO4) were used as phase-forming material of the aqueous two-phase system, and the binodal data was measured at the three temperatures (288.15, 298.15, 308.15 K). Three classic experienced formulas were used to fit the binodal data, and they had better performance in data association. The tie-line data of studied systems were measured and fitted by the empirical formulas, i.e., Othmer–Tobias and Bancroft equations. It has better performance in data association. For the investigated systems, the influence of the salt type on the binodal curves was studied by the Gibbs free energy of ions hydration and effective excluded volume, and the influence of temperature on the tie-lines and binonal curves was also discussed. First, as it is confirmed, when the salts are of the same anion, salts with higher cation valence will have stronger abilities of salting out; the salting out abilities of salts strengthen with the...