(676f) Predicting the Thermodynamic Properties of Mixed Solvent Electrolytes Using the SAFT-VR+DE Approach

One of the main problems in the development of predictive approaches for electrolyte solutions is the complexity of the interactions and the need to describe the long-range charge-charge and charge-polar interactions. Several theoretical models have been developed to specifically deal with these interactions in electrolyte solutions, which traditionally have been obtained through macroscopic theories based on phenomenological equations containing adjustable parameters that lack physical meaning. In this regard, a molecular-based equations of state, such as the statistical associating fluid theory (SAFT), are attractive as they can describe the thermodynamics of complex systems using physically based parameters. The SAFT approach, proposed by Gubbins and co-workers¹ based on Wertheim’s thermodynamic perturbation theory for association,² explicitly takes into account the effects of molecular non-sphericity and association interactions. Within the SAFT framework, many extensions of the original equations have been proposed to expand the accuracy and applicability of the theory. Some of the recent extensions by McCabe and coworkers³, have incorporated the different electrostatic interactions (ion-ion, ion-dipole and dipole-dipole) using the mean spherical approximation of Blum et al.⁴ and the non-primitive model to account for the solvent molecules explicitly, in the so-called SAFT-VR+DE equation. In this work, we apply the SAFT-VR+DE approach to study the thermodynamic properties and phase behavior of mixed solvent electrolytes.

¹       W. G. Chapman, K. E. Gubbins, G. Jackson, and M. Radosz, Fluid Phase Equilibria 52, 31 (1989); W. G. Chapman, G. Jackson, and K. E. Gubbins, Molecular Physics 65 (5), 1057 (1988).

²       M. S. Wertheim, Journal of Statistical Physics 35 (1-2), 19 (1984); M. S. Wertheim, Journal of Statistical Physics 35 (1-2), 35 (1984); M. S. Wertheim, Journal of Statistical Physics 42 (3-4), 459 (1986); M. S. Wertheim, Journal of Statistical Physics 42 (3-4), 477 (1986).

³       H. Zhao and C. McCabe, Journal of Chemical Physics 125, 104504 (2006); H. Zhao, Y. Ding, and C. McCabe, Journal of Chemical Physics 127, 084514 (2007); H. Zhao, M. C. dos Ramos, and C. McCabe, Journal of Chemical Physics 126, 244503 (2007).

⁴       D. Wei and L. Blum, Journal of Chemical Physics 87 (5), 2999 (1987); L. Blum and D. Q. Wei, Journal of Chemical Physics 87 (1), 555 (1987).