Prediction of vapor-liquid equilibria in mixed-solvent electrolyte systemsusing the group contribution concept

The LIQUAC model is widely used to predict reliably vapor-liquid equilibria (VLE), osmotic coefficients and mean ion activity coefficients for electro lyte systems. It consists of a Debye-Huckel term, the UNIQUAC term and the osmotic virial equation for the middle-range contribution. The aim of this work is to provide a model based on the group contribution concept that can be used to predict phase equilibria in mixed-solvent electrolyte systems. Therefore, in the LIQUAC model the UNIQUAC equation has been substituted by the original UNIFAC equation and group interaction parameters have been in troduced into the middle-range term. With the help of a large data base, 23 4 group interaction parameters for seven solvent groups, 13 cations and sev en anions have been fitted. The model parameters have been used to calculat e the VLE behavior, osmotic coefficients and mean ion activity coefficients for a large number of systems with high accuracy. (C) 1999 Elsevier Scienc e B.V. All rights reserved.