USE OF AN ELECTROLYTE EQUATION OF STATE FOR THE CALCULATION OF VAPOR-LIQUID-EQUILIBRIA AND MEAN ACTIVITY-COEFFICIENTS IN MIXED-SOLVENT ELECTROLYTE SYSTEMS

In a previous paper [W. Furst, 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 Furst [Y.-X. Zuo, W. Furst, Flui d Phase Equilibria 138 (1997) 87-104.] extended it to predict vapor pr essures and mean ionic activity coefficients for various non-aqueous e lectrolyte systems. In this work, the model has been extended to mixed -solvent electrolyte systems. This has been done by deducing most of t he ionic parameters from experimental solvation properties and by deve loping mixing rules to represent preferential solvations in mixed-solv ents, the aim being to minimize the number of adjustable parameters. V apor-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 devia tions for VLE are similar to those obtained by other authors, but with less adjustable parameters. Furthermore, it could represent mean ioni c activity coefficients as well. Finally, the model has been used to p redict VLE for 12 other mixed-solvent electrolyte systems with satisfa ctory results. (C) 1998 Elsevier Science B.V. All rights reserved.