A SAFT-VR+DE equation of state based approach for the study of mixed dipolar solvent electrolytes

The SAFT-VR+DE approach was developed by combining the statistical associating fluid theory for potentials of variable range (SAFT-VR) with integral equation theory and the generalized mean spherical approximation using a non-primitive model, in order to explicitly describe the solvent in electrolyte solutions. Subsequently, the theory was applied to study nineteen different aqueous electrolyte solutions and a range of thermodynamic properties across different temperatures and salt concentrations were successfully predicted. Here, the theory is applied to study several model mixed dipolar solvent electrolytes in order to validate a simple one-fluid-like approximation that is proposed to describe the interactions between ions and dipolar solvents of arbitrary size and dipole moment. Before application to real fluids the approach is extensively tested through comparison with isothermal-isobaric ensemble (NPT) Monte Carlo simulations for a number of model mixed dipolar solvent electrolyte systems. Simulations have been performed for different ionic concentrations, solvent compositions, cation, anion, and solvent segment diameters, and solvent polarity. The results show that the SAFT-VR+DE equation provides a good description of the PVT behavior of the model mixed solvent electrolyte systems studied, with some over-prediction of the PVT behavior observed only at higher ionic concentrations. Additionally, comparisons are made between predictions from the non-primitive and primitive models for electrolytes and the importance of capturing the effect of ions on the solvent dielectric is demonstrated.