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 in situ 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.