Thermodynamic modeling of electrolyte solutions by a hybrid ion-interaction and solvation (HIS) model

A novel hybrid ion-interaction and solvation (HIS) model was recently developed based on the work of Lin et al. [117]. This report presents the model formulations for calculating the mean activity coefficient, osmotic coefficient, solvent activity, vapor pressure, vaporization enthalpy, freezing point depression (FPD) and boiling point elevation (BPE) of electrolytes solutions. A critical evaluation of the model performance was conducted by investigating statistically the standard deviations of modeling results from measured data for a large number of systems, and comparing with the classical Pitzer equation which only considers ion-interactions, as well as the Bromley model. The model is proven to be valid for both aqueous and non-aqueous solutions across a wide concentration range, and it performs better than the Pitzer model for some specific systems; in particular, it behaves very well for a few highly concentrated systems, indicating the importance of solvation effect on properties of concentrated solutions. The model is successfully applied for calculating the mean activity coefficients and osmotic coefficients of a few sample systems. Estimated vapor pressures are fairly consistent with measured values, with an average error of 1.6% for aqueous solutions and 0.3% for non-aqueous solutions. Estimation of the vaporization enthalpies yields a mean error of 8.0%. Although only parameters obtained for systems at T=298.15 K are used, the model is also effective in the FPD and BPE predictions, with average errors of 4.0% and 8.7%, respectively.