title: A New Mechanism in Electrochemical Process for Arsenic Oxidation: Production of H2O2 from Anodic O2 Reduction on the Cathode under Automatically Developed Alkaline Conditions.
abstract: Electrochemical cathodes are often used to reduce contaminants or produce oxidizing substances (i.e., H2O2). Alkaline conditions develop automatically around the cathode in electrochemical processes, and O2 diffuses onto the cathode easily. However, limited attention is paid to contaminant transformation by the reactive species produced on the cathode under oxic and alkaline conditions due to the inapplicability of pH for Fenton reaction. In this study, a new oxidation mechanism on the cathode is presented for contaminant transformation under automatically developed alkaline conditions. In an electrochemical sand column, 6.67 μM As(III) was oxidized by 36% when it passed through the cathode under the conditions of 30 mA current, an initial pH of 7.5 and a flow rate of 2 mL/min. Under the alkaline conditions (pH 10.0-11.0) that developed automatically around the cathode, the reduction potential of As(III) decreased greatly, allowing a pronounced oxidation by the small quantities of H2O2 produced from O2 reduction on the cathode. As(III) oxidation was further increased by the presence of soil pore water and groundwater solutes of HCO3-, Ca2+, Mg2+ and humic acid. The new oxidation mechanism found for the cathode under localized alkaline conditions supplements the fundamentals of contaminant transformation in electrochemical processes.
authors: †State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, P. R. China.|‡School of Environmental Studies, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, P. R. China.
authors: Ao
authors: A
authors: Qian
authors: †State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, P. R. China.|‡School of Environmental Studies, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, P. R. China.
authors: Songhu
authors: S
authors: Yuan
authors: †State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, P. R. China.
authors: Peng
authors: P
authors: Zhang
authors: †State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, P. R. China.|‡School of Environmental Studies, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, P. R. China.
authors: Man
authors: M
authors: Tong
mesh_terms: D000468:Alkalies / Q000737:chemistry*; D001151:Arsenic / Q000737:chemistry*; D002412:Cations; D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes; D004572:Electrolysis; D006812:Humic Substances / Q000032:analysis; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D012996:Solutions
chemical_list: D000468:Alkalies; D002412:Cations; D006812:Humic Substances; D012996:Solutions; D006861:Hydrogen Peroxide; D001151:Arsenic; D010100:Oxygen