New local composition model for electrolyte solutions: multicomponent systems

The recently proposed model for single solvent, single electrolyte solutions has been modified and extended to multicomponent systems. Parameters for 22 electrolytes have been regressed to data on mean ionic activity coefficients and osmotic coefficients from the literature. A new assumption has made it possible to reduce the number of model parameters to two per electrolyte, and has also eliminated the need for a mixing rule to derive multicomponent parameters from binary parameters. In general, the model still compares favourably to the Electrolyte NRTL model according to Chen for binary electrolyte systems. A comparison between experimental and calculated osmotic coefficients has shown that the new model predicts osmotic coefficients of multicomponent electrolyte systems very well, using model parameters obtained by regressing data on only binary electrolyte systems. The regressed parameters were also used to calculate solubilities in some ternary and quaternary aqueous electrolyte systems at 298.15 K. The results show reasonable agreement with literature data. (C) 2000 Elsevier Science B.V. All rights reserved.