An exergy-guided thermodynamic framework for the optimization of electro-membrane-based coupled process

Electrically driven membrane separation processes are extensively utilized in water treatment due to their remarkable flexibility, which facilitates seamless integration with a wide range of other processes. However, optimizing complex coupled systems, where transport phenomena are intertwined with chemical reactions, remains a grand challenge. Conventional performance metrics and existing thermodynamic models often fail to deconvolute the distinct sources of energy loss, hindering targeted improvements. To address this, we introduce a novel diagnostic framework that, for the first time, integrates transmembrane ionic exergy analysis with the exergy accounting of a coupled, multiphase reaction network. This allows for the explicit quantification of previously lumped thermodynamic irreversibility. Applying this framework to a bipolar membrane electrodialysis (BMED) system for flue-gas treatment, we identified and quantified two dominant, yet distinct, energy loss pathways: (1) proton (H⁺) leakage across the anion exchange membrane, a transport-related loss, and (2) the inherent irreversibility of the gas-liquid-solid reaction chain, a chemistry-related loss. Pinpointing these specific bottlenecks provides clear targets for optimization. The framework facilitates multi-objective optimization, identifying an operational region that balances performance with thermodynamic efficiency. Experimental results validate the model's ability to predict key operational trends with good quantitative accuracy. With its high adaptability, this exergy-guided diagnostic approach offers a powerful and generalizable tool for analyzing and optimizing complex electrochemical systems.