Ionic liquids as entrainers for the separation of the ethanol/water system

• VLE measurements of ethanol/water and ethanol/water/IL mixtures at 101.3 and 66.6 kPa.
• Introduction of the entrainers to the ethanol/water system resulted to the successful elimination of the azeotropic point.
• Successful thermodynamic modeling with UNIQUAC and NRTL.
• The ILs can be recycled and reused.
• The ability of the ILs to biodegrade was found to be relatively low.

Isobaric vapor–liquid equilibrium measurements of the ethanol/water binary mixture and ethanol/water/ionic liquid ternary mixtures were performed using an ebuliometer at 101.3 and 66.6 kPa. The ionic liquids (ILs) synthesized and examined as entrainers for the ethanol/water azeotropic mixture were 1-butyl-3-methylimidazolium bromide ([BMIM][Br]) and 1-ethyl-3-methylimidazolium bromide ([EMIM][Br]). For both ILs, the initial concentrations for the ternary mixtures were 5%, 10% and 15% w/w. The entrainers were also tested for their recoverability and biodegradability. Analysis with 1H NMR proved that the ionic liquids can be recycled and reused while their ability to biodegrade was found to be relatively low.Introductionof the entrainers to the ethanol/water system resulted in an increase of the relative volatility, due to the salting-out effect on ethanol, leading to the successful elimination of the azeotropic point. The effect on the relative volatility follows the order [EMIM][Br] > [BMIM][Br], which corresponds to the order of increasing affinity of water to the specific entrainers.Finally, the thermodynamic modeling of the ethanol/water/IL mixtures was investigated with the UNIQUAC and NRTL models. The results for both models were found to be in good agreement with the experimental data.

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