Use of an electrolyte equation of state for the calculation of vapor–liquid equilibria and mean activity coefficients in mixed solvent electrolyte systems

Abstract

In a previous paper [W. Fürst, H. Renon, AIChE J. 39 (1993) 335–343], a new electrolyte equation of state has been developed and applied to aqueous strong electrolyte solutions. One of the original features of this equation was that all ionic parameters could be determined using correlations related to experimental solvation properties which leads to a predictive model. Later, Zuo and Fürst [Y.-X. Zuo, W. Fürst, Fluid Phase Equilibria 138 (1997) 87–104.] extended it to predict vapor pressures and mean ionic activity coefficients for various non-aqueous electrolyte systems. In this work, the model has been extended to mixed-solvent electrolyte systems. This has been done by deducing most of the ionic parameters from experimental solvation properties and by developing mixing rules to represent preferential solvations in mixed-solvents, the aim being to minimize the number of adjustable parameters. Vapor–liquid equilibrium data relative to 26 water–alcohol–salt systems and mean ionic activity coefficients relative to eight water–alcohol–salt systems have been represented using only 18 parameters. The deviations for VLE are similar to those obtained by other authors, but with less adjustable parameters. Furthermore, it could represent mean ionic activity coefficients as well. Finally, the model has been used to predict VLE for 12 other mixed-solvent electrolyte systems with satisfactory results.