(563c) Examining the Thermodynamic Properties of Ionic Systems Using the SAFT-VR+DE Approach. From Simple Aqueous Electrolyte to Polar Mixed-Solvent Electrolyte Systems | AIChE

(563c) Examining the Thermodynamic Properties of Ionic Systems Using the SAFT-VR+DE Approach. From Simple Aqueous Electrolyte to Polar Mixed-Solvent Electrolyte Systems

Authors 

Dos Ramos, M. C. - Presenter, Vanderbilt University
McCabe, C. - Presenter, Vanderbilt University


Knowledge of the thermodynamic behavior of electrolyte solutions are very important to industrial processes, such as biological, electrochemistry, corrosion and environmental processes. Thus, a predictive tool that can accurately describe the thermodynamic behavior of such systems is in high demand. 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 equation of state, such as the statistical associating fluid theory (SAFT), can be considered as a powerful tool that describes the thermodynamics of complex systems using adjustable physically based parameters. The SAFT approach was proposed by Chapman et al.1 based on Wertheim's thermodynamic perturbation theory for association2, and 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, which essentially correspond to different choices for the monomer fluid and/or different approaches to the calculation of the monomer free energy and structure. Some of the recent extensions to the theory 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 deal with pure fluids and mixtures of charged and polar fluids, such as electrolytes, mixed polar solvent electrolytes and ionic liquids.

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).

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