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

Abstract

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 TFe-anode/TMMO-anode:Tpower-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 PO43– 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.