Cloud point extraction is a versatile method aimed at separating compounds from complex mixtures and arouses great technological interest, particularly among the biochemical industries. However, one must have deep knowledge of the liquid–liquid equilibrium behavior of systems to properly use the method. Thus, we used thermodynamic parameters to evaluate the effect of citrate, sulfate, and tartrate anions on the phase separation of water + Triton X-114^® mixtures at 283.2 K, 293.2 K, and 303.2 K. In these systems, increasing the temperature and the anion molar fraction expanded the biphasic region in the following order: ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{O}}_7^{3-}$> ${\mathrm{SO}}_4^{2-}$ > ${ \mathrm{C}}_4{\mathrm{H}}_4{\mathrm{O}}_6^{2-}$. Unlike other studies based on the Hofmeister series, the Gibbs free energy of micellization correlated the anion effect on the biphasic region with the spontaneity of the micelle formation. The water molecules structured around these anions were evaluated according to the shell volume of the immobilized water by electrostriction, volume of water around the hydration shell, Gibbs free energy of hydration, and Gibbs free energy of electrostriction ($\Delta {\mathrm{G}}_{\mathrm{el}12}$). The citrate anion presented a higher $\Delta {\mathrm{G}}_{\mathrm{el}12}$ of −1781.49 kJ mol⁻¹, due to the larger number of electrons around it. In addition, the partition coefficient of the surfactant in the two liquid phases revealed a linear dependence upon the anion mole fractions by following the previous anion sequence and temperature in the phase separation.

Two-phase aqueous systems have replaced and simplified steps in extraction and purification processes, especially for biocompounds. Thus, this study evaluated the liquid-liquid equilibrium behavior of Pluronic L64 + water + sodium salts at pH 5.0, 7.5, and 10.0. Sodium sulfate demonstrated the greatest phase separation, followed by sodium citrate and sodium tartrate. Higher pH values resulted in larger biphasic regions. The polymer distribution coefficients increased with the addition of salt. As pH increased, there was a tendency for Pluronic L64 to migrate to the polymer-rich phase. The Gibbs energy of micellization between −11,000 and −25,000 kJ mol⁻¹ indicated the spontaneity of the process micellization for all systems, showing lower values for the systems with sodium sulfate. This parameter was related to the anion speciation at each pH. Besides, the effects of water structuring around ions and ion-polymer interaction influenced the phase separation.