Experimental Determination and Correlation of Liquid–Liquid Equilibria Data for a System of Water + Ethanol + 1‑Butyl-3-methylimidazolium Hexafluorophosphate at Different Temperatures

Over the past few years, interest has increased regarding the application of ionic liquids (ILs) as extraction solvents for separating azeotropic mixtures. Following this trend, this work presents the experimental data of liquid–liquid equilibria (LLE) of the system envolving water, ethanol, and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]­[PF6]) at different temperatures. The LLE data of the system was measured between 283.2 and 323.2 K to determine the temperature influence on the system. In the literature, reports of systems involving ILs that present type II behavior are scarce compared with those that present type I behavior; the system presented here also displays two immiscibility zones in the ternary system. The universal quasichemical (UNIQUAC) and nonrandom two-liquid (NRTL) models were applied to correlate the ternary system. Both of the models obtained fit the equilibrium compositions and showed type II behavior; nevertheless, UNIQUAC presented a better result. Finally, the solvent ability of the IL for the purpose of separating the mixture formed by ethanol and water was evaluated and compared with other ionic liquids studied in the literature.