Aqueous strong electrolyte solution activity coefficients and densities from fluctuation solution theory

Abstract

A model based on direct correlation function integrals (DCFIs) has been completed and used to describe the thermodynamic properties of single-salt aqueous electrolyte solutions. The principal advance is that parameters fitted only to activity coefficients are able to predict solution densities and compressibilities up to saturation concentrations over wide ranges of temperature and pressure. Though the parameter set involves a total of eight quantities for each salt, three, and potentially others, can be found from ionic additivity relations. Further, the parameters are constants or have linear or quadratic temperature variations up to 300°C. The model has been applied to 15 salts of all charge types involving mono- and divalent species. Correlation of activity coefficient data is normally more accurate than current models, especially near saturation such as for lithium halides up to 20 molar. The predicted densities are commonly within experimental error even up to 100 MPa.