Thermodynamic Modeling of Mixed Solvent Electrolyte Solutions: Challenges and Practical Guide

Electrolyte systems are characterized by their (i) strong nonideal behavior requiring advanced thermodynamic models, (ii) reactive components necessitating knowledge of formation properties, and (iii) multiphase nature, which demands robust reactive algorithms. These complexities are crucial in industrial applications, leading to the creation of the Joint Industry Project (JIP) EleTher, which aims to promote further academic exploration and provide recommendations for parametrizing such systems. To better understand interactions in electrolyte systems, the study focuses on quaternary systems comprising water, an acid, a base, and a cosolvent. This approach isolates pH effects from the dielectric constant influences. Due to limited data, only ternary subsystems were analyzed. The study evaluated the accuracy of three approaches: full dissociation (FD), no dissociation (ND), and partial dissociation (PD). While FD and ND approaches performed adequately for vapor–liquid equilibrium, they failed when speciation became significant. The PD approach, though more accurate, revealed challenges with parameter optimization as multiple local minima resulted in varying species distributions. A hybrid approach combining FD, ND, and PD models is recommended for achieving the most physically meaningful results. The study utilized the eNRTL method CPA equation of state within in-house tools (Carnot and ATOUT) to conduct the analysis.