2025 AIChE Annual Meeting

Application of Association Enrtl Model for Prediction of Thermodynamic Properties of Aqueous Mixed-Electrolyte Systems

Accurate prediction of the thermodynamic properties of aqueous mixed-electrolyte systems is crucial for many industrial processes, including lithium brine extraction, desalination, and amine scrubbing for carbon capture. However, modeling these systems can be difficult due to the nonidealities caused by ion-ion and ion-solvent interactions. Recently, an innovative extension of the widely-used electrolyte-NRTL model was developed, incorporating a new term based on association theory to better capture the interactions between ions and between ions and solvents. This project investigates the predictive quality of the association eNRTL model for the activity coefficients and osmotic coefficients of aqueous mixed-electrolyte systems.

A set of tertiary and quaternary aqueous mixed-electrolyte systems were selected from existing literature, involving salts comprised of Li+, Na+, K+, Cs+, NH4+, and Mg2+ cations paired with Cl-, Br-, NO3-, and SO42- anions. For each system, predictions of the activity coefficients of each salt and the osmotic coefficient of the system were calculated through the association eNRTL model using recently regressed parameters, as well as the standard eNRTL model. Both models were compared against experimental data from the literature and analyzed for goodness of fit and reproduction of observed trends.

While the predictive quality varied based on system complexity and electrolyte composition, the results indicate that the association eNRTL model often outperformed the standard eNRTL model, particularly in systems with strong ionic associations or high-charge-density cations like lithium and sodium. However, in other cases, the models performed comparably. Overall, this work demonstrates the potential of the association eNRTL model to improve predictions of the thermodynamic behavior of aqueous mixed-electrolyte systems, valuable to the simulation and design of various electrolyte-based applications.