New local composition model for modeling of thermodynamic and transport properties of binary aqueous electrolyte solutions

A new local composition model, which is an NRF–modified-NRTL (NRF–mNRTL) model, is developed for the representation of the excess Gibbs energy of electrolyte solutions. In this model for excess Gibbs energy the sum of a long-range and a short-range term is used. The contribution of the long-range excess Gibbs energy is represented by the Pitzer–Debye–Hückel model. A new expression based on the local composition concept has been developed to account for the contribution of the short range excess Gibbs energy. The model is applied to correlate the mean ionic activity coefficients and osmotic coefficients of more than respectively 150 and 290 binary aqueous electrolyte solutions at 25 °C. The fitting quality of the new model has been favorably compared with the electrolyte NRTL, Wilson, modified NRTL, NRTL–NRF, NRF–Wilson, UNIQUAC–NRF, Pitzer and TCPC models. Viscosity values of the binary aqueous solution of electrolytes have also successfully been correlated with the proposed local composition model by considering the Eyring absolute rate theory. The validity of the proposed model is specially demonstrated for multivalent electrolyte binary solutions encompassing the entire range of composition.