No abstract

Mean activity coefficient values for NaCl in the mixture (water + ionic liquid) (IL) as solvent (IL being 1-ethyl-3-methyl-imidazolium methanesulfonate, [Emim][MeSO 3 ] or 1-ethyl-3-methyl-imidazolium ethyl sulfate, [Emim][EtSO 4 ]) were determined from the electrode potential measurements of the cell: Na−(ISE) | NaCl (m A ), ILs (w), H 2 O (1 − w) | Cl−(ISE) (ISE means ion selective electrode) at total ionic strengths ranging from 0.10 to 3.20 mol•kg −1 and at 298.15 K. Different weight fractions (w) of ILs (w = 0.01, 0.05, 0.1, 0.2, 0.3 and 0.4) were used. Data were fitted to the Pitzer model and the ion interaction parameters β 0 , β 1 , and C γ were calculated. The osmotic coefficients of the solvent (water + IL), the solvent activity, the excess Gibbs free energy for the system were calculated. The negative sign in the excess free energy for the NaCl + IL+ H 2 O solvent mixture at 298.15 K suggests a spontaneous aggregation of {[Emim][MeSO 3 ] + H 2 O} or {[Emim][EtSO 4 ] + H 2 O}.

The main objective of this work is to continue with a series of electrochemistry studies of mixtures of ionic liquids and water as a solvent to provide accurate data for future particular applications [J. Chem. Eng. Data201762752]. The mean activity coefficients for NaCl in [2-hydroxyethylammonium butyrate (2-HEAB) + H2O] as a solvent mixture were determined by cell potential measurements: Na–ion selective electrode (ISE)|NaCl (m), 2-HEAB (w), H2O (1 – w)|Cl–ion selective electrode (ISE) at molalities from 0.10 to 3.20 mol·kg–1 at 298.15 K. Different weight fractions (w) of 2-HEAB with w = 0.01, 0.05, 0.1, 0.2, 0.3, and 0.4 were used. At higher concentrations of w = 0.40, NaCl is salting out by 2-HEAB in water. The Pitzer ion interaction parameters β0, β1, and C γ were used to find the values of osmotic coefficients, solvent activity, and the excess Gibbs free energy for the mixed electrolyte system. The results may be interpreted by the clathrate-like formation of 2-HEAB + water. A qualitative description of the relation between water and the 2-HEAB was done using the general AMBER force field (GAFF).