The thermodynamic modelling of fluid mixtures containing electrolytes using the SAFT-γ
Mie equation of state is addressed in detail in this thesis. The SAFT-γ Mie approach
allows the implementation of heteronuclear molecules using a group-contribution formalism,
and offers a versatile framework for developing models to describe molecules of varying
chemical functionality for a broad range of physical properties. In the present work, the
SAFT-γ Mie equation of state is extended to electrolyte mixtures with the incorporation
of the primitive unrestricted mean spherical approximation (MSA-PM) for describing the
Coulombic ion–ion interactions, and the Born solvation free energy to implicitly treat ion–
solvent polar interactions. Novel reformulations of the MSA-PM and Born theories within a
group-contribution framework are proposed in order to enable ionic species of any size and
chemical structure to be modelled, from small inorganic ions to large non-spherical charged
molecules. Taking carboxylate anions in linear alkyl chain molecules as an illustrative case
study, the proposed theory is shown to effectively account for localised charge effects arising
from the structural topology of the charged species. A holistic description of electrolyte
solutions is employed in this work; in addition to the short-range dispersion forces and
the long-range Coulombic interactions which are pertinent to such mixtures, the models
developed here also account for the formation of hydrogen bonds, ion-pairing phenomena,
and electrolyte dissociation equilibria. The proposed SAFT-γ Mie equation of state is used to
model aqueous solutions of strong electrolytes including alkali halide salts, hydrogen halide
acids, and alkali hydroxide bases. Aqueous solutions of sulphuric acid and nitric acid are
studied in detail by modelling these as speciating weak electrolytes. Finally, the treatment of
ion-pairing phenomena is investigated through a consideration of aqueous alkali nitrate salt
solutions. This work presents a new theoretical formulation and SAFT-γ Mie group models
for twenty species in total.Open Acces
