Liquid–Liquid Equilibrium for the Ternary System Water + 1-Methylimidazole + Ionic Liquid ([Hmim][PF6], [Omim][PF6], or [Omim][BF4]) at 303.15 K

To evaluate the feasibility of extraction of 1-methylimidazole from its low-concentration aqueous solution by ionic liquids, the liquid–liquid equilibrium of the ternary system of water + 1-methylimidazole + ionic liquid ([Hmim][PF6], [Omim][PF6], or [Omim][BF4]) was determined at 303.15 K and atmospheric pressure. The distribution coefficient and selectivity were calculated in accordance with the experimental results. The effects of the anion and cation of ionic liquids on the separation ability were discussed. The results indicated that the extraction capacity increased with increasing cationic carbon chain length, and the change of anions significantly affected the distribution coefficient and selectivity. As expected, the three ionic liquids were feasible as extractants for separating 1-methylimidazole from water. It also indicated that [Omim][PF6] was a more suitable extractant than [Hmim][PF6] and [Omim][BF4] for the extraction. The highest distribution coefficient and selectivity of [Omim][PF6] could reach 1.71 and 111.92, respectively, indicating [Omim][PF6] as a good choice for extracting 1-methylimidazole from water. In addition, the non-random two-liquid model was employed to successfully correlate the experimental data with a root-mean-square deviation of less than 0.0188. Moreover, a GUI-MATLAB tool was used to verify the consistency of the correlated parameters.