Liquid–Liquid Phase Equilibrium and Ion-Exchange Exploration for Aqueous Two-Phase Systems of ([C 4 mim]Cl + K 2 CO 3 or K 3 C 6 H 5 O 7 + water) at Different Temperatures

Liquid–liquid equilibrium (LLE) data and phase diagrams for new aqueous two-phase systems (ATPSs) containing 1-butyl-3-methylimidazolium chloride ([C 4 mim]Cl) + tripotassium citrate or potassium carbonate + water were determined experimentally at T = (283.15, 293.15, 298.15, 308.15, and 313.15) K and p = 94 kbar. The effect of the temperature, anion, composition, and ion exchange were evaluated in the formation of these ATPSs. It was observed that decreasing the temperature promoted the phase separation in both ATPSs indicating the exothermic character of the process. The ability of different anions to induce phase separation was compared and the order for the strength of the salting out effect observed was PO_4^3->HPO_4^2->CO_3^2->C_6H_5O_7^3-≫HO^- . The extent of ion exchange between the equilibrium phases in the two different ATPSs was experimentally evaluated and found to be negligible. The binodal curves were fitted to an empirical non-linear expression and the salting out effect was explored using the type-Setschenow equation and the consistence of equilibrium data was evaluated theoretically using the Othmer–Tobias, Hand and Bancroft equations. Finally, the liquid–liquid equilibrium in the ATPSs evaluated in the present work were modelled by NRTL model. Graphical Abstract