Wu, Po ChangPo ChangWuViet Cuong, DinhDinhViet CuongWu, Jhen CihJhen CihWuYa Hsuan Liou, SofiaSofiaYa Hsuan LiouCHIA-HUNG HOU2023-09-262023-09-262023-10-1513858947https://scholars.lib.ntu.edu.tw/handle/123456789/635803Limited electrocatalytic oxidation of As(III) to As(V) constrains the potential of capacitive deionization (CDI) for achieving efficient arsenic removal. In this study, we present a novel approach to incorporate cobalt oxide (CoOx) nanoparticles with activated carbon (AC), referred to as a bifunctional nanocomposite CoOx/AC electrode, and thereby achieve the simultaneous in-situ electrocatalytic oxidation of As(III) and the efficient electrosorption of As(V). The electrochemical measurements of the CoOx/AC electrode, which had a high specific surface area of 540.2 m2 g−1, demonstrated good electrical conductivity and electrocatalytic activity toward the As(III) oxidation reaction. Asymmetric CDI experiments with the CoOx/AC electrodes were performed at 1.2 V in batch-mode for different pH values. It is indicated that elevated pH can enhance the As(III) removal efficiency. Compared to the AC electrode, the CoOx/AC electrode had a considerably higher electrosorption capacity of 0.75 mg g−1 with a low energy consumption of 0.12 kWh m−3 at pH 10. To obtain insight into the mechanisms, the As(III)/As(V) concentrations and distribution were investigated in a charging–discharging cycle. When the CoOx/AC electrode was used as the anode, the electrocatalytic conversion of As(III) into As(V) was significantly enhanced from 43% to 67%, and then the generated As(V) could be electroadsorbed by electrical double-layer charging, thereby achieving an improvement in As(III) removal. Finally, the single-pass asymmetric CDI operated at ten consecutive charging–discharging cycles further demonstrated the great feasibility of using the CoOx/AC electrode to promote the in-situ electrocatalytic oxidation of As(III) for remediation of arsenic-contaminated groundwater.As(III) oxidation | Capacitive deionization | Cobalt oxide | Electrocatalytic oxidation | Electrosorption[SDGs]SDG6journal article10.1016/j.cej.2023.1458872-s2.0-85170570362https://api.elsevier.com/content/abstract/scopus_id/85170570362