Equilibrium Thermodynamic Properties of Aqueous Solutions of Ionic Liquid 1-Ethyl-3-Methylimidazolium Methanesulfonate [EMIM][MeSO3].

The ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MeSO3]) has been considered as a promising alternative desiccant to triethylene glycol and lithium bromide commonly used in the industry. In this paper, the water activity coefficient of this binary system was measured from 303 K to 363 K with water concentration from 18% to 92%. The interaction energies between the ionic liquid molecules ([Formula: see text]) and between the ionic liquid and water molecules ([Formula: see text]) for the [EMIM][MeSO3]/water binary system were determined from the water activity coefficient data using the Non-Random Two-Liquid (NRTL) model. The magnitude of the interaction energy between the [EMIM][MeSO3] and water molecules ([Formula: see text]) was found to be in the range of 45~49 kJ/mol, which was about 20% larger than that between the water molecules ([Formula: see text]) in the [EMIM][MeSO3]/water system. The large ([Formula: see text]) can explain many observed macroscopic thermodynamic properties such as strong hygroscopicity in the ionic liquid [EMIM][MeSO3]. These interaction energies were used to determine the heat of desorption of the [EMIM][MeSO3]/water system, and the obtained heat of desorption was in good agreement with that calculated from the conventional Clausius-Clapeyron Equation.