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Title: Development of the SAFT-γ Mie equation of state for predicting the thermodynamic behaviour of strong and weak electrolyte solutions
Author: Lazarou, Georgia
ISNI:       0000 0004 7223 6071
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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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.
Supervisor: Galindo, Amparo ; Jackson, George ; Adjiman, Claire Sponsor: Pfizer Ltd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral