Abstract
The degradation of organic contaminants is typically achieved by exposure of hydrogen peroxide (H2O2) containing influent to ultraviolet (UV) lamps as the source of radiation that can convert H2O2 to hydroxyl radicals (·OH), which oxidize organic pollutants. However, two factors prevent this process from being scaled down: the need to introduce H2O2, which requires special handling, and the use of bulky UV lamps, which have a high electric power consumption. In this work, an electrochemical cell was developed for the efficient in situ generation of H2O2 from water and atmospheric oxygen in a process called a two-electron oxygen reduction reaction (2e-ORR), so that the external addition of H2O2 is no longer needed. Moreover, the electrochemical cell was equipped with ultraviolet light-emitting diodes (UV-LEDs) to convert H2O2 to ·OH. The reactor exhibited a current efficiency of ∼90% for the H2O2 production at a flow rate of 50 mL min−1. The degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) was studied at 277 nm based on different operational parameters, such as UV fluence rate, initial concentration, and initial pH. A high degradation of >70% was obtained at a UV output of 900 mW. Our approach, the first of its kind, has novel features applied, including: optimal radiation distribution in the reactor by applying a new UV source, UV-LEDs that offer much more control for the radiation profile in the reaction system compared to traditional UV lamps, controlled hydrodynamics by implementing special flow channels to provide a more uniform residence time and offer enhanced mixing, and integrating UV reactor and electrochemical cell in a single unit which could lead to superior performance and space efficiency of the device. These features make the device very suitable for point-of-use (POU) water treatment applications to eliminate both microbial and chemical contaminants.
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