Electrocatalytic Oxidation Processes for Treatment of Halogenated Organic Pollutants in Aqueous Solution: A Critical Review

Halogenated organic pollutants (HOPs) are a class of organic substances that are difficult to degrade, easily bioaccumulate, and are stable in the environment. Compared with biological, physical, and chemical methods, electrocatalytic oxidation technology has the advantages of a strong oxidation ability, high efficiency, mild reaction conditions, and high automation. The direct and indirect electrochemical oxidation mechanisms in electrocatalytic oxidation processes are discussed. The generation processes and properties of oxidative species in indirect electrochemical oxidation processes, including hydroxyl radicals, active chlorine, sulfate radicals, O3, H2O2, carbonate radicals, and 1O2, are summarized. The cell designs involved in the flow-by, flow-through, and three-dimensional configurations are outlined. The removal ratios, intermediate products, and electrocatalytic oxidation mechanisms of halogenated pollutants, including perfluorinated, polyfluorinated, chlorinated, brominated, and iodinated organic compounds, are reviewed. The oxidative and mineralization ability, detoxification ability, and energy consumptions of electrocatalytic oxidation compared with other technologies are comprehensively evaluated. This Review are intended to introduce some effective strategies for lowering energy consumption in electrocatalytic oxidation processes. Finally, the current deficiencies and development trends in electrocatalytic oxidation are discussed.