Measurement and Modeling of Phase Equilibrium in Aqueous Two-Phase Systems: L35 + Sodium Citrate + Water, L35 Sodium Tartrate + Water, and L35 + Sodium Hydrogen Sulfite + Water at Different Temperatures

Phase diagrams have been determined for aqueous two-phase systems containing (EO)11(PO)16(EO)11, notation L35 (50% EO), and sodium citrate, sodium tartrate, or sodium hydrogen sulfite at different temperatures. The influences of the temperature and anion on the behavior of these systems were also analyzed. The temperature effect on the position of the binodal curves for systems containing sodium citrate and tartrate was not relevant, indicating a small enthalpy contribution associated with the phase separation. However, an enthalpic contribution for the phase splitting of the systems formed by sodium hydrogen sulfite was observed. The ability of these three salts to induce the formation of a biphasic system with L35 followed the order sodium citrate > sodium tartrate > sodium hydrogen sulfite. In this work, the nonrandom two-liquid (NRTL) model was used to obtain new interaction energy parameters. The results were analyzed using root-mean-square deviations between experimental and calculated data in equil...