Electrolyte-UNIQUAC-NRF Model Based on Ion Specific Parameters for the Correlation of Mean Activity Coefficients of Electrolyte Solutions

The Electrolyte-UNIQUAC-NRF excess Gibbs function was applied to estimate ion specific adjustable parameters of various salts by global optimization of the experimental activity coefficients of 54 electrolyte solutions. Twenty-three ion specific parameters were obtained for water and several cations and anions. The estimated individual ion parameters have been used to predict osmotic coefficient of electrolyte solutions. By using only the specific values for ions, the anion-cation and ion-water interaction parameters of different salts can be precisely estimated. Consequently, the interaction parameters of sparingly insoluble salts without experimental activity data can be easily calculated. For a case study, the solubility of CaSO4 was predicted in relatively good agreement with experimental values over a wide range of temperatures up to 473.18 K.