Phase equilibrium of aqueous two-phase systems composed by L35 triblock copolymer + organic and inorganic ammonium electrolytes + water at 298.2 and 313.2 K

Abstract

Liquid-liquid equilibrium data of aqueous two-phase systems (ATPS) composed by L35 triblock copolymer + ammonium electrolytes (nitrate, NO3−; tartrate, C4H4O62−; phosphate, HPO42−; acetate, C2H3O2−) + water, at different temperatures (298.2 and 313.2 K) are presented in this paper. The experimental ATPS data were correlated with the original and modified non-random two-liquid (NRTL) for predicting energetic parameters of the studied systems. The results were satisfactory with global root mean square deviations (33 tie-lines) of the 2.36% and 2.53% for the original and modified models, respectively. The effect of the temperature and electrolyte nature on the biphasic area position was investigated. The increase of the temperature promoted a slight increase in the two-phase region indicating the endothermic character of the phase splitting. The increase in the temperature also promoted a rise in the module of the slope of the tie-lines. The anions ability to promote phase separation followed the order: HPO42− > C4H4O62− > NO3− > C2H3O2−.