Abstract
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•Ion removal performance of FCDI was greatly enhanced via cathodic iodide redox couple.•A similar positive effect noticed during desorption upon polarity reversal.•The system exhibited a stable behavior over multi-cycle consecutive runs.•The approach holds great promise in treatment of iodide-containing saline wastewater.
Flow-electrode capacitive deionization (FCDI) is attracting growing attention owing to its advantages such as effective ion removal capacity and easy management of the electrodes. Optimization of the flow-electrode comprising carbon materials and aqueous electrolyte is always a research hotspot aimed at improving FCDI performance. Herein, we innovatively introduced appropriate amount of KI3 into the cathodic flow-electrode to provide a highly efficient means of enhancing FCDI desalination performance with a stable behavior in salt electrosorption and desorption over multi-cycle consecutive runs. The accelerated salt removal rate originated from the reversible redox reaction of I3−/I− and the maintenance of the electro-neutrality of the global electrolyte. Although possible minor release or leakage of I−/I3− through the cation-exchange membrane and into the treated water occurred, which makes the proposed approach not quite suitable for potable water production, we demonstrated that this system has great application prospects in treatment of iodide-containing saline wastewater without causing secondary pollution.