A Critical Comparative Study of Boron Removal from Synthetic Single-Stage Seawater Reverse Osmosis Permeate by BPM- and AEM-Assisted Electrosorption

Abstract

Membrane-assisted electrosorption, particularly the utilization of anion exchange membrane (AEM)- and bipolar membrane (BPM)-assisted systems, has garnered increasing interest as an effective technology for boron removal from a single-stage reverse osmosis (RO) permeate. In this study, we systematically examine the key factors─supporting electrolyte composition, charging voltage, and discharging voltage─that impact boron removal performance in both setups, with the insights provided aiding both process optimization and full-scale application. Our results indicate that, while the BPM-assisted system operates at a relatively lower cell voltage and consumes approximately 67% the amount of the energy used by the AEM-assisted system, the requirement for additional salt for sufficient conductivity and water dissociation is impractical for removal of boron from the RO permeate. Furthermore, due to the high cost of BPMs, the overall operational cost of the BPM-assisted system is ∼5-fold higher than that of the AEM-assisted system. Our results further show that applying a reverse potential (−1 V) during discharge desorbs only ∼60–65% of the boron, suggesting that electrode/membrane replacement is needed to maintain activity. Overall, while membrane-assisted electrosorption shows promise for boron removal from RO permeate, significant advancements are needed for both configurations to improve boron removal rates, reduce electrode and membrane costs, and decrease energy demands.