Composite electrodes for selective bromide recovery using membrane capacitive deionization: Optimizing selectivity and performance

Efficient bromide recovery from seawater and desalination brine is increasingly critical for renewable energy storage and industrial applications, yet conventional electrochemical systems struggle with selectivity in chloride-dominated matrices. We report bromide-selective composite electrodes (BrSCE) that integrate anion-exchange resin particles within activated carbon matrices, creating a dual-pathway architecture where ion selectivity enhances electrochemical separation. The composite design positions resin microspheres throughout the porous carbon network, enabling simultaneous capacitive deionization and selective ion exchange under applied voltage. Systematic parameter optimization identified critical performance factors: resin loading (20–50%), feed solution Cl − : Br − ratios (1: 1 to 5:1), and applied voltage (0.8–1.6 V ), yielding quadratic predictive models (R 2 > 0.97, p < 0.0001) for both selectivity and desalination efficiency. The optimized BrSCE (43.6 wt% resin content, 1.2 V) achieved Br − /Cl − selectivity of 2.83 in challenging 5:1 Cl − : Br − molar ratio solutions, directly addressing the primary limitation in halide separation from real brines. Notably, the system demonstrated exceptionally rapid bromide recovery kinetics with 45% desorption within 2 min and 97% total recovery, representing a substantial acceleration compared to conventional ion-exchange processes. The BrSCE simultaneously delivered 60% TDS reduction, enabling dual-function operation for both selective resource recovery and water purification. These performance characteristics position the composite electrode approach as a viable strategy for valorizing low-concentration bromide sources previously considered uneconomical, advancing circular economy principles in industrial water treatment, and critical resource recovery.