Modeling electrolyte solutions with the SAFT-VR equation using Yukawa potentials and the mean-spherical approximation

An equation of state based on the statistical associating fluid theory for potentials of variable range (SAFT-VR) is used to model 7 hydrogen-bonding solvents and 23 electrolyte solutions. Solvent-solvent hydrogen bonding interactions are explicitly taken into account as in other versions of the SAFT approach. In addition, long-range Coulombic interactions between ionic species are accounted for using the non-restricted mean-spherical approximation, while solvent-solvent and solvent-ion dispersion interactions are included and are treated using Yukawa potentials. Previously a similar approach had been proposed in which the dispersion interactions were treated using square-well potentials. In this work a comparison is made between the two models. Vapour pressure, solution densities and activity coefficients are examined using both salt-specific parameters as well as ion-specific parameters. The salt-specific model is especially useful in terms of considering solutions at very high concentrations (molalities of the order of 20 and above). The model is also used to predict the vapour pressure of a mixed salt system.