Mean Activity Coefficients and Phase Equilibria of the NaBr–Na₂SO₄–H₂O Ternary System at 278.2 and 288.2 K

Abstract

In this paper, the cell potential method is used to determine the activity coefficients of the NaBr−Na 2 SO 4 −H 2 O ternary system at 278.2 and 288.2 K. The cell potentials of NaBr− H 2 O solutions are measured using a cell without a liquid junction composed of ion-selective electrodes. According to the measured cell potentials of NaBr-H 2 O solutions, the response curve can be obtained by combining the Nernst equation. The measured cell potentials of NaBr−Na 2 SO 4 −H 2 O mixed solutions are combined with the Nernst equation to determine the activity coefficients, and the mixed ion interaction parameters θ Br,SOd 4 and ψ Na,Br,SOd 4 of the Pitzer model are obtained by applying the activity coefficients and the programming solver. Then, other thermodynamic parameters are calculated using Pitzer equations, such as the activity coefficient of Na 2 SO 4 (γ Nad 2 SOd 4 ), the osmotic coefficient ( ), water activity (a w ), and excess Gibbs free energy (G E ). In addition, the phase equilibria of the NaBr−Na 2 SO 4 −H 2 O ternary system at 288.2 K were investigated using the isothermal dissolution equilibrium method, and phase equilibrium predictions were made for the NaBr− Na 2 SO 4 −H 2 O ternary system at 278.2 and 288.2 K. The experimental values of the system at 288.2 K are in good accordance with the predictions, and therefore, the fitted parameters have good applicability.