Exposed redox-active iron enables electrochemically highly selective capture and conversion of arsenic from water

Trace amounts of highly toxic arsenic, particularly arsenite (As(III)), in urban and agricultural water present a significant challenge to ensuring water safety. Existing separation processes have significant limitations, mainly due to poor selectivity and insufficient oxidation of As(III). In this study, we introduce a redox-active iron coordination electrode with exposed iron active sites (FePc-CNTS), designed for the selective electrochemical removal and oxidation of As(III) from water. At a cell voltage of 1.2 V, the FePc-CNTS electrode effectively remediated arsenic at concentrations as low as 150 μg L^-1 with a removal rate of 92.3 %, even in the presence of more than 1000-fold excess of competing anions. More than 93 % of the captured As(III) is converted and released in a less harmful pentavalent form. The high affinity (-18.96 kcal mol^-1) and strong electron transfer capability of the exposed iron active sites for As(III) enables the synergistic selective capture and conversion of As(III). The exposed iron active sites-based electrode exhibits high selectivity, remediating arsenic-contaminated water with low energy consumption (0.08 kWh m^-3). This study elucidates the advantages of exposing metal sites for the efficient electrochemical removal and conversion of pollutants, offering a new strategy for design and optimization of electrochemical separation technologies.