Novel Reuse Strategy in Flow-Electrode Capacitive Deionization with Switch Cycle Operation To Enhance Desalination Performance

Flow-electrode capacitive deionization (FCDI) is a promising electrochemical desalination system because of its superior desalination capacity during a continuously operating process. However, FCDI suffers from a lack of an effective reuse step for charged flow-electrodes for conducting continuous desalination despite several approaches such as mixing charged flow-electrodes [short-circuit cycle (SCC) operation] and applying a reverse voltage. Herein, we report a novel strategy termed switch cycle operation in which the charged flow-electrodes from positively and negatively biased electrode channels are swapped and supplied to oppositely biased electrode channels for the next sequential desalination step. The major results include switch cycle operation achieving the effective reuse of charged flow-electrodes for the next desalination step. The desalination performance, expressed in terms of salt removal efficiency and system current in FCDI, significantly improved by approximately 1.7 times compared with that of the SCC. This enhanced performance is attributed to the release of ions from the charged flow-electrodes that cause additional ion flux to achieve charge neutrality during the sequential desalination steps.