Electrochemically switched ion separation technologies: A review on electroactive ion exchange materials and system architectures

[Display omitted] •ESIS techniques for selective ion extraction are comprehensively reviewed.•Faradaic redox principles and categories of EIXMs are summarized.•Various system architectures are classified and highlighted.•Ion selective mechanisms in the ESIS process are evaluated. Efficient and selective ion separation from complex aqueous solutions is highly relevant for resource recovery, energy storage, and environment protection. The emerging electrochemically switched ion separation (ESIS) technologies have attracted widespread attention due to their high selectivity, energy efficiency, and environmental friendliness. Basic research on ESIS focuses primarily on the design of electroactive ion exchange materials (EIXMs) and the innovation of electrochemical system architectures. The well-tailored EIXMs for film/membrane electrodes rely on Faradaic redox reactions to capture ions selectively. Significant advancement has been achieved in the transition from intermittent operation in electrochemically switched ion exchange (ESIX) to continuous running in electrochemically switched ion permselective membrane (ESIPM) with the regarding of system architectures. This review systematically outlines the research and development of ESIS technologies from four key aspects: EIXMs development, system architectures, ion selectivity mechanisms, and prospects. First, the principles and categories of EIXMs are summarized. Next, the evolutions of system architectures in terms of cell designs, driving mode optimization, and practical application are emphasized. Then, the ion selectivity mechanisms explored with the aid of experimental and computational approaches are elucidated. Finally, the challenges and prospects of ESIS including ion separation mechanisms, film/membrane electrodes, module development, and process intensification and scaling up are discussed.