Predicting Thermodynamic Properties of Ions in Single Solvents and in Mixed Solvents Using a Modified Born Term within the ePC-SAFT Framework

Abstract

In this work, the EoS ePC-SAFT was further developed by modifying the Born term and introducing a new mixing rule for the dielectric constant of electrolyte solutions. The modified Born term considers the solvent solvation-shell volume of ions and accounts for the radial dependence of the dielectric constant near a central ion. This required one additional parameter per ion and one per solvent, while other pure-component parameters were inherited from the literature. The performance of ePC-SAFT was validated against experimental literature data: Gibbs energies of solvation and of transfer and MIACs in pure water, methanol, ethanol, and in their mixtures. The new modeling approach improves the accuracy of Gibbs energies at infinite dilution while retaining the ability to model properties of concentrated electrolyte systems. Additionally, ePC-SAFT parameters for V³⁺ and VO²⁺ ions were fitted to density and osmotic-coefficient data of VCl₃ and VOSO₄ in water using the new approach.