Energy-Efficient Electrochemical Strategy for the Oxidative Sequestration of As(III) in Synthesized Anoxic Groundwater

In this study, a wave rectified alternating current (RAC) electrocoagulation process was developed for the oxidative sequestration of As­(III) via simultaneous generating Fe­(II) and O₂ in the synthesized anoxic groundwater. The optimal T_Fe‑anode/T_MMO‑anode:T_power‑off ratio (T is the time-taken in corresponding stage) and reaction period for As­(III) sequestration were 1:2:1 and 24 s, respectively. Elevating electric current applied on the alternate iron/MMO anodes (30–50 mA) and solution pH (6.0–9.0) promoted As­(III) sequestration, whereas the presence of HCO₃^– and PO₄^3– deteriorated As­(III) sequestration. The intermediate Fe­(IV) primarily accounted for the oxidation of As­(III) to As­(V), which can be readily sequestrated by the freshly generated Fe­(III) (oxyhydr)­oxides. The energy required for As­(III) sequestration in the RAC electrocoagulation process was only 0.11 kW·h m^–3, which is much less than those in the traditional DC/AC electrocoagulation processes. Generally, this study offers an energy-efficient strategy to improve access to safe groundwater for millions of people.