Review of flow electrode capacitive deionization technology: Research progress and future challenges

Flow-electrode capacitive deionization (FCDI) couples flow electrode and ion exchange membrane to bridge the technical bottleneck of limited adsorption capacity and long-term continuous operation of traditional CDI technology. After nearly a decade of extensive research, FCDI technology has made positive progress in the research of charge transport theory and operation mechanism, material development, and engineering applications, and has shown good application prospects. This paper summarizes and compares the mechanism, energy consumption and cost of FCDI technology with other deionization technologies (including Reverse Osmosis, Electrodialysis, Multi-stage Flash and Fixed Capacitive deionization). Furthermore, we introduce the flow electrode materials (including carbon materials and faraday materials) and the application of FCDI in the environmental field (including desalination, resource recovery and contaminant removal). Finally, the possible problems of FCDI technology (such as expansion design, energy recovery and technology coupling) are presented and the main challenges in the future full-scale applications are presented.