Electrolyte-UNIQUAC-NRF model for the correlation of the mean activity coefficient of electrolyte solutions

The new electrolyte-UNIQUAC-NRF excess Gibbs function is obtained for calculation of the activity coefficient of the binary electrolyte solutions. The excess Gibbs energy of the model consists of the Pitzer–Debye–Hückel equation, describing the long-range electrostatic contribution and the electrolyte-UNIQUAC-NRF model to account for the short-range contributions. With two adjustable parameters per electrolyte, the new model is applied to correlation of the mean activity coefficients of more than 130 binary aqueous electrolyte solutions at 25 °C. Also the binary parameters, obtaining from regression of mean activity data, are used for prediction of osmotic coefficient data for the same electrolytes. The results are compared with various local composition models such as the electrolyte-NRTL, electrolyte NRF-Wilson, electrolyte-NRTL-NRF, N-Wilson-NRF models. The comparison of the results with experiment demonstrates that the new model can correlate the experimental activity coefficient data and predict the osmotic coefficient data of binary electrolytes accurately.