Thermodynamic properties of ternary aqueous solutions of {Li/Cl/NO 3/SO 4}(aq) mixtures at T = 298.15 K

Abstract

In this investigation, ternary aqueous solutions of chloride, nitrate or sulphate with a common lithium cation have been studied using the hygrometric method at 298.15 K. The water activities of the systems { yLiCl + (1 − y)Li 2SO 4}(aq), { yLiCl + (1 − y)LiNO 3}(aq) and { yLiNO 3 + (1 − y)Li 2SO 4}(aq) are measured at total molalities from 0.20 mol kg −1 to saturation for different ionic-strength fractions ( y) of LiCl for {Li/Cl/NO 3}(aq) and {Li/Cl/SO 4}(aq), or of LiNO 3 for {Li/NO 3/SO 4}(aq), with y = 0.20, 0.50 and 0.80. The obtained data allow the deduction of osmotic coefficients. From these measurements, ionic mixing parameters are determined and used to predict the solute activity coefficients in these mixtures, using Pitzer's ionic interaction model. The ternary parameters θ and ψ are evaluated for these systems. The excess Gibbs energies are also determined. The results of the ternary systems of nitrate, chloride, or sulphate with a common lithium cation {Li/Cl/NO 3/SO 4}(aq) are compared. The behaviour of aqueous electrolyte solutions of nitrate, chloride, sulphate, with a common lithium cation is correlated and shows that the ionic interactions in these solutions is essentially manifested by the hydration of the ions solute LiCl, LiNO 3, Li 2SO 4 in the aqueous solutions.