Measurement and Correlation of Liquid–Liquid Equilibria of Water (1) + 1-Methylimidazole (2) + [Bmim][PF6] (3) Ternary Systems between 303.15 and 323.15 K

To obtain the basic data for the recovery of 1-methylimidazole from wastewater by extraction, the ternary liquid–liquid phase equilibrium data of the water (1) + 1-methylimidazole (2) + 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) (3) system were determined using an equilibrium autoclave at the temperatures of 303.15 to 323.15 K and 101.32 kPa. The solute distribution coefficient (D) and the selectivity (S) of the ternary system were calculated in accordance with the experimental data. Their values were up to 1.39 and 41.17, respectively, which showed that the ionic liquid can extract 1-methylimidazole effectively. The experimental results showed that the temperature had a slight effect on the liquid–liquid equilibrium behavior. Meanwhile, the calculated results revealed that the selectivity coefficient decreased with the enhancing concentration of 1-methylimidazole in the ternary system and the increasing temperature. In addition, the nonrandom two liquid (NRTL) model was used for correlation of the ternary systems. The root-mean-square deviation value of 0.0218 indicated that the calculated results using the model were in good agreement with the experimental data and were reliable to apply to practice.