Extension of the eSAFT-VR Mie equation of state from aqueous to non-aqueous electrolyte solutions
Nefeli Novak, Georgios M. Kontogeorgis, Marcelo Castier, Ioannis G. Economou
Abstract
In this work, the eSAFT-VR Mie equation of state (EoS) is extended to low relative permittivity, non-aqueous solutions. The effect of using different relative permittivity relations for the electrolyte solutions is studied, ranging from experimentally measured values to a salt-composition independent relative permittivity. Furthermore, the effect of using different approaches for the characteristic diameters in the Debye-Hückel and Born terms is presented. The eSAFT-VR Mie EoS is reparametrized using aqueous mean ionic activity coefficients, individual ion activity coefficients and densities with different relations for the relative permittivity. Afterwards, the performance of these models on non-aqueous solutions is evaluated based on the Mean Ionic Activity Coefficients of salts in non-aqueous solutions. The conclusion is that a mole fraction based mixing rule for the relative permittivity yields the best extrapolation from aqueous to non-aqueous solutions, and achieves quantitative predictions for the mean ionic activity coefficients of monovalent salts in methanol and ethanol without additional adjustable parameters.