A new NRTL-based local composition model for thermodynamic modeling of electrolyte solutions

Abstract

A new local composition model for the expression of excess Gibbs energies and activity coefficients in binary and multicomponent electrolyte solutions is presented in this work. The model is based on the nonrandom two-liquid (NRTL) theory and is developed assuming the random contribution of ions and molecules around central species at reference state. The new model provides a completely new formulation for the expression of short-range interactions in electrolyte solutions. The accuracy of developed equations is examined using the available experimental data for several aqueous electrolyte systems at vast ranges of concentration and temperature. The results are compared with those obtained from eNRTL model. Two binary interaction parameters of the model are adjusted for numerous binary salt-water systems through the accurate correlation of the mean ionic activity coefficient data. Adjusted parameters are then successfully used for the prediction of osmotic coefficients in binary systems. When compared to the eNRTL model, the new model is more accurate. That superiority is very significant for the systems which are highly non-ideal. To examine the adequacy of the model for multicomponent systems, available experimental solubility and osmotic coefficient data of different ternary aqueous electrolyte systems are compared to the values predicted by the model. Using only the previously adjusted binary interaction parameters, the predicted values are in very good agreement with the experimental data.