Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Phase behaviour of new aqueous two-phase systems (ATPSs) composed by 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim]BF4) + copper sulfate (CuSO4) + water systems have been determined experimentally at T = (283.15, 298.15, and 313.15) K. The phase diagrams obtained at the different study temperatures describe the liquid-liquid equilibrium (LLE) and, in some cases, the liquid-liquid-solid equilibrium (LLSE) for different mixture compositions. The effect of the temperature, composition, and ion exchange in the formation this ATPS were available. The temperature had a remarkable effect on the position of phase diagrams. The decrease in temperature promoted phase separation indicating the exothermic character of formation of these ATPSs and further, at temperatures of 283.15 and 298.15K it was observed the occurrence of phase inversion for some mixture compositions. The extent of the ionic exchange of the original ionic pairs between the phases in equilibrium was evaluated considering the electroneutrality of the phases. It was observed experimentally that, in the liquid-liquid equilibrium condition established, there was no significant exchange of the ionic pairs. The ability of different cations, from different sulfate salts, to induce the formation of ATPSs in mixtures involving [Bmim]BF4 was evaluated. For this, thermodynamic data of hydration of different cations reported in the literature were used together with experimental data of saturation solubility to establish a scale. Thermodynamic parameters of transfer of components (cations, anions and water) between the phases were also calculated from the experimental data and indicated that the material transfer of the bottom phase to the top is not spontaneous and tends to be less spontaneous as the TLL value increases. Additionally, the equilibrium data and binodal curves were fitted to an empirical non-linear expression (Merchuk equation) and the salting out effect was explored using the type-Setschenow equation.