Modeling acid–base equilibria and phase behavior in mixed-solvent electrolyte systems

A comprehensive thermodynamic framework for mixed-solvent electrolyte systems has been applied to the simultaneous computation of phase behavior and acid–base equilibria. The computational approach combines an excess Gibbs energy model with a formulation for standard-state properties of individual species and an algorithm for speciation calculations. Using this framework, a consistent methodology has been established to calculate the pH of mixed-solvent solutions using a single, aqueous reference state. It has been shown that solid solubilities, vapor–liquid equilibria, solution pH and other properties can be reproduced for mixed solvents ranging from pure water to pure non-aqueous components and for solutes ranging from infinite dilution to the fused salt limit. In particular, the model has been shown to be accurate for mixtures containing hydrogen peroxide and ethylene glycol as solvents and various salts, acids and bases as solutes.