Ionic liquids (ILs) are playing an increasingly important role in separation science. In this account, the application of ILs in all areas of separation including extraction, gas chromatography, and supported liquid membrane processes is highlighted. 1,3-Dimethylimidazolium methyl Sulfate [MMIM] [MeSO4] is Suitable for use as solvent in the petrochemical extraction process for the removal of ethanol from its mixture with hexane. The knowledge of liquid-liquid equilibria (LLE) is essential for the design of the separation technique applied. For this reason, the experimental LLE for the ternary system hexane + ethanol + [MMIM] [MeSO4] has been determined at 298.15 K. The solvent capacity of the [MMIM] [MeSO4] is compared with other ILs. Extraction process with this solvent is simulated using conventional software and the obtained results are shown. Experimental data are obtained in a laboratory-scale packed column extraction system for the separation of this azeotropic mixture using [MMIM] [MeSO4]. IL could be recycled and then the separating process reduces the energy consumption greatly. (C) 2009 Elsevier B.V. All rights reserved