Energy-Efficient Oxidation and Removal of Arsenite from Groundwater Using Air-Cathode Iron Electrocoagulation

Arsenic contamination of groundwater has affected many countries, especially in Southeast Asia. Although aerated electrocoagulation (EC) provides an effective way to remove arsenite, this process is energy-intensive because of aeration and relatively poor cathode performance. To overcome these disadvantages, a novel EC system was proposed using an air cathode to generate H₂O₂ <i>in situ</i> for improved energy efficiency of As­(III) removal. With the air cathode, the H₂O₂ production rate was 3.7 ± 0.1 mg L^–1 h^–1, which indirectly promoted As­(III) oxidation by interaction with Fe­(II). At a current density of 4 A m^–2, the average cell voltage during air-cathode electrocoagulation (ACEC) was 1.0 V, compared to 1.9 V in the EC and aerated EC systems. Energy consumption in the ACEC system was 17.0 ± 0.7 Wh log^–1 m^–3, much lower than those in the EC (67.8 ± 0.9 Wh log^–1 m^–3) and aerated EC (65.1 ± 0.8 Wh log^–1 m^–3) systems, which can be attributed to effective As­(III) oxidation, no need for aeration, and improved cathode performance with the air cathode. These results showed that the ACEC system is a promising technology for energy-efficient removal of arsenite from contaminated groundwater