Simultaneous electrodialytic recovery of HCl and LiOH from LiCl: Modeling, optimization and experimental validation

The growing demand for lithium-ion batteries (LIBs) highlights the need for sustainable recycling technologies. Electro-electrodialysis (EED) has emerged as a promising alternative for regenerating chemical reagents and recovering lithium-based salts from hydrometallurgical leachates. This study investigates the electrodialytic production of HCl and LiOH from LiCl solutions using a four compartment EED cell. A mathematical model was developed to describe ions transports, acid and base regeneration and energy consumption, incorporating electrochemical and mass transport parameters. The model was validated through five batch-mode EED experiments under different operating conditions. Experimental results validated the model's accuracy in predicting the concentrations of Li⁺, Cl⁻, H⁺ and OH⁻ over time, as well as the voltage and specific energy consumption, with R² values above 0.99. The optimal performance was achieved under conditions of high initial LiOH concentration (0.5 M) and low electrode distance (8 cm), which minimized the energy consumption while maintaining high product yields. Conversely, higher initial acid concentrations reduced ion recovery, likely due to increased ionic competition and membrane transport resistance. Under the optimal conditions, specific energy consumption reached value8.3 kWh·kg⁻¹ HCl and 13.7 kWh·kg⁻¹ LiOH. The validated model provides a reliable tool for optimizing EED performance and reducing experimental effort. This work demonstrates the feasibility of using EED to selectively generate acid and base from LiCl-rich solutions and supports the development of more efficient approaches for LIB recycling.