Thermodynamic modeling of aqueous and mixed solvent electrolyte systems

Electrolyte systems are ubiquitous and play critical roles in a wide variety of industrial and natural processes, including basic chemical manufacturing, pharmaceutical processing, nuclear waste processing, etc. This chapter describes key thermodynamic relationships for electrolyte systems and advances in electrolyte thermodynamic models, as well as three examples of how to apply these models to aqueous and mixed solvent electrolytes. Various thermodynamic properties of electrolyte systems, such as vapor pressure, osmotic coefficient, mean ionic activity coefficient, solution enthalpy, heat capacity, and salt solubility, are integral to process simulation of natural and industrial processes. These properties are all derived from the activity coefficients of chemical species in the system, and, therefore, accurate calculation of activity coefficients as functions of temperature and solution composition has become the focus of electrolyte thermodynamic models. The chapter summarizes the Pitzer and the electrolyte nonrandom two-liquid model.