Thermodynamic investigation of KCl in the ternary KCl/LiCl/ H 2 O mixed electrolyte system based on potentiometric method

Abstract

The results of a thermodynamic investigation of KCl salt in the ternary KCl+LiCl+H 2O electrolyte system by potentiometric method are reported in this work. The experimental potentiometric data were obtained from a galvanic cell by combining a solvent polymeric (PVC) potassium-selective membrane electrode (K + ISE), containing Valinomycin as ionophore, and an Ag/AgCl electrode. The measurements were performed, at similar constant ionic strengths, in different series of mixed salt solutions, each characterized by a fixed salt molal ratio r (where r = m 1 / m 2 = 0.1 , 0.2 , 1 , 5 , 10 , and m 1 , m 2 are the molalities of KCl and LiCl, respectively). The non-ideal behaviour of the system was described on the base of the Pitzer ion-interaction model for mixed salts, over the ionic strength ranging from 0.01 up to about 5 mol/kg, at 298.15 K. Based on the obtained Pitzer ion-interaction parameters, the osmotic coefficients, solvent activities, and excess Gibbs free energies were determined for these investigated ternary electrolyte systems.