Part I: Thermodynamic analysis of volumetric properties of concentrated aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate,and ethylammonium nitrate based on pseudo-lattice theory

This study concerns volumetric behaviour of mixtures between water and three ionic liquids: 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄), 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (bdmimBF₄), and ethylammonium nitrate (EAN). We report that the pseudo-lattice theory proposed by Bahe and recently supplemented by Varela et al. can suitably describe the partial molar volume of ionic liquids throughout the composition scale from the infinitely dilute state to the pure room temperature molten salt. In this approach, the ions of 1:1 electrolytes in concentrated solutions are supposed to be distributed in a face-centred-cubic structure. The main advantage of this approach is that, contrary to Debye–Hückel approach, it widens the range of composition that can be described to high concentration salt solutions (several times molar) and also the most diluted salt solutions.