Representation of activity and osmotic coefficients of electrolyte solutions using non-electrolyte Wilson-NRF model with ion-specific parameters

• A non-electrolyte activity coefficient model with ion-specific parameters has been used for calculations of activity and osmotic coefficients of binary aqueous electrolytes.
• The results are comparable with electrolyte models.
• The extension of the model for several ternary aqueous electrolytes has been carried out successfully.

The non-electrolyte Wilson-NRF (NWN) model for electrolyte solutions that is composed of a local composition expression and the Pitzer–Debye–Hückel equation has been used for electrolyte solutions using ion specific parameters. The interaction energy parameters of the NWN model have been reported for water, seven cations including Na+, Li+, K+, Cs+, Rb+, Ca2+ and Mg2+ and eight anions including Cl−, Br−, OH−, NO3−, Ac−, I−, F− and SO42−. These parameters have been obtained by correlation of the mean activity coefficients of the related binary aqueous electrolyte solutions, i.e., forty five possible salt/water systems. The fitting results were in good agreements with the experimental data of the mean activity coefficients of the electrolytes. The calculations of osmotic coefficients of the binary electrolyte solutions were represented by the model with good accuracy. Also the experimental data of solubility, activity coefficient and water activity of NaCl–KCl–H2O ternary electrolyte solution can be predicted by the model satisfactorily. Moreover, it has been shown that the model can be well used to predict the osmotic coefficients of a number of ternary systems.