Optimization of Electrode and Channel Stack Architecture for Enhanced Na2SO4 Valorization Performance in Redox-Mediated Bipolar-Membrane Electrodialysis

Abstract Redox-mediated bipolar-membrane electrodialysis (redox-BMED) is an emerging electrochemical platform for sustainable resource recovery that replaces conventional water-splitting reactions with reversible redox chemistry and employs non-precious, porous carbon electrodes. This approach is particularly promising for valorizing industrial sodium sulfate (Na2SO4) wastewater generated from spent lithium-ion battery recycling. However, practical deployment requires optimization of multi-electrode and channel stack architectures to reduce mass-transport limitations and ohmic losses. Here, we investigate the effects of electrode- and channel-stack configurations on energy efficiency and treatment throughput in redox-BMED. Independent evaluation shows that electrode stacking mainly enhances energy efficiency by lowering polarization losses, whereas channel stacking increases treatment throughput by expanding the number of parallel ion-transport pathways. Optimization of combined architectures identifies a 12 electrode/2 channel configuration as the favorable balance architecture, achieving a ∼42% reduction in specific energy consumption relative to the 1 electrode/1 channel configuration (2.91 to 1.69 kWh kg–1 Na2SO4) while preserving near-quantitative charge efficiency (∼99%). These results indicate that electrode and channel stacks play complementary roles, jointly minimizing energy losses and sustaining efficient ion transport. Overall, this work provides practical design principles for balancing electrode and channel configurations for scalable, energy-efficient redox-BMED-based Na2SO4 valorization.