Development of intermolecular potential models for electrolyte solutions using an electrolyte SAFT-VR Mie equation of state

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Title: Development of intermolecular potential models for electrolyte solutions using an electrolyte SAFT-VR Mie equation of state
Authors: Eriksen, DK
Lazarou, G
Galindo, A
Jackson, G
Adjiman, CS
Haslam, AJ
Item Type: Journal Article
Abstract: We present a theoretical framework and parameterisation of intermolecular potentials for aqueous electrolyte solutions using the statistical associating fluid theory based on the Mie interaction potential (SAFT-VR Mie), coupled with the primitive, non-restricted mean-spherical approximation (MSA) for electrolytes. In common with other SAFT approaches, water is modelled as a spherical molecule with four off-centre association sites to represent the hydrogen-bonding interactions; the repulsive and dispersive interactions between the molecular cores are represented with a potential of the Mie (generalised Lennard-Jones) form. The ionic species are modelled as fully dissociated, and each ion is treated as spherical: Coulombic ion–ion interactions are included at the centre of a Mie core; the ion–water interactions are also modelled with a Mie potential without an explicit treatment of ion–dipole interaction. A Born contribution to the Helmholtz free energy of the system is included to account for the process of charging the ions in the aqueous dielectric medium. The parameterisation of the ion potential models is simplified by representing the ion–ion dispersive interaction energies with a modified version of the London theory for the unlike attractions. By combining the Shannon estimates of the size of the ionic species with the Born cavity size reported by Rashin and Honig, the parameterisation of the model is reduced to the determination of a single ion–solvent attractive interaction parameter. The resulting SAFT-VRE Mie parameter sets allow one to accurately reproduce the densities, vapour pressures, and osmotic coefficients for a broad variety of aqueous electrolyte solutions; the activity coefficients of the ions, which are not used in the parameterisation of the models, are also found to be in good agreement with the experimental data. The models are shown to be reliable beyond the molality range considered during parameter estimation. The inclusion of the Born free-energy contribution, together with appropriate estimates for the size of the ionic cavity, allows for accurate predictions of the Gibbs free energy of solvation of the ionic species considered. The solubility limits are also predicted for a number of salts; in cases where reliable reference data are available the predictions are in good agreement with experiment.
Issue Date: 25-Oct-2016
Date of Acceptance: 8-Sep-2016
ISSN: 1362-3028
Publisher: Taylor & Francis
Start Page: 2724
End Page: 2749
Journal / Book Title: Molecular Physics
Volume: 114
Issue: 18
Copyright Statement: © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Qatar Petroleum
Engineering & Physical Science Research Council (EPSRC)
Pfizer Incorporated
Funder's Grant Number: GR/T17595/01
8500208599 / 1400
Keywords: Chemical Physics
0202 Atomic, Molecular, Nuclear, Particle And Plasma Physics
0306 Physical Chemistry (Incl. Structural)
0307 Theoretical And Computational Chemistry
Publication Status: Published
Open Access location:
Appears in Collections:Faculty of Engineering
Chemical Engineering

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