Abstract
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 ({g}_{22}) and between the ionic liquid and water molecules ({g}_{12}) 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 ({g}_{12}) was found to be in the range of 45~49 kJ/mol, which was about 20% larger than that between the water molecules ({g}_{11}) in the [EMIM][MeSO3]/water system. The large ({g}_{12}) 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.
Highlights
The macroscopic thermodynamic properties of the [EMIM][MeSO3]/water binary system have been extensively investigated, the molecular thermodynamic properties of this binary system are not comprehensive
[MeSO3]/water system, which was in good agreement with those calculated from the Clausius-Clapeyron Equation
The effect of the ionic liquid on the non-ideality of the aqueous solutions can be expressed by the activity coefficients of water γH2O, which was calculated by Eq [1]
Summary
The macroscopic thermodynamic properties of the [EMIM][MeSO3]/water binary system have been extensively investigated, the molecular thermodynamic properties of this binary system are not comprehensive. The interaction energy or bonding energy between the ionic liquid molecules, and between the ionic liquid and water molecules are extremely scarce for the ionic liquid [EMIM][MeSO3]/water systems. These molecular interaction energy properties are related to many macroscopic thermodynamic properties such as heat of desorption, heat capacity, hygroscopicity, and water vapor pressure. The Non-Random Two-Liquid (NRTL) model was used to determine the interaction energies between different molecule pairs inside the [EMIM][MeSO3]/water binary system from the measured water. These interaction energies were used to determine the heat of desorption of the [EMIM].
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