Equilibrium phase behavior of aqueous two-phase system formed by triblock copolymer þ sulfate salt þ water at different temperatures.

Abstract

Equilibrium data for the ternary liquid-liquid system formed of a triblock copolymer (L64 or F68), sulfate salts (Cu(II) or Fe(III)) and water were investigated in this work. The effects of temperature (278.15, 288.15 and 298.15 K), the nature of the cation and the copolymer molar mass on the phase diagram of the aqueous two-phase system were investigated. An increase in temperature decreased the biphasic region for the entire system. Cu(II) and F68 were better able to induce phase separation compared to Fe(III) and L64. The nature of the cation and the copolymer molar mass effect are discussed as a function of the formation of aqua acids through the reaction between the cation and water (Brønsted acids) and in relation to Flory-Huggins theory for macromolecule solutions, respectively. The consistencies of the tie line and binodal curve experimental compositions were evaluated by applying the Othmer-Tobias and Merchuk correlations, respectively.