Chemical free pH control for efficient lithium recovery via redox-couple mediated bipolar membrane electrodialysis

A novel redox couple mediated bipolar membrane electrodialysis (redox-BMED) system was developed and optimized to enable chemical free pH control in CO 2 based lithium precipitation. Unlike conventional methods that rely on alkaline reagents such as NaOH, this system utilizes in situ water dissociation through a bipolar membrane (BPM) and reversible redox mediation (Fe(CN) 6 4− /Fe(CN) 6 3− ), thereby avoiding additional chemical inputs. The effects of operating conditions such as applied voltage (0.6–1.2 V), flow rates (2–10 mL/min) and electrodes stacking were investigated. Maximum performance was achieved with a lithium ion flux of 13.82 g-Li + /m 2 d and energy consumption of 1.33 Wh/g. A techno-economic analysis was conducted to evaluate the cost-effectiveness of the redox-BMED system compared to conventional BMED. The redox-BMED system demonstrated over 70 % reduction in total annual cost, primarily due to simplified stacking design and lower membrane usage. Overall, these findings indicate that redox-BMED offers a viable alternative for lithium recovery in CO 2 based precipitation processes. Its ability to combine chemical free pH control, high purity product formation, and competitive economic returns underscores its potential for large-scale lithium recycling and resource utilization. • A novel redox-BMED was developed for chemical-free pH control in Li recovery. • The system achieved high Li + ion flux and low energy consumption. • Multi-electrode stacking enhanced the performance and scalability of redox-BMED • Long-term stability confirms redox-BMED's potential for sustainable Li recovery. • Techno-economic analysis shows the economical benefit of redox-BMED.