Ozonation combined with ultraviolet irradiation (UV/O3) has been applied to degrade recalcitrant pollutants with the OH radical-based strong oxidation power. In this work, electrochemical UV/O3 process (E-UV/O3) was developed, where the conventional O3 production by corona discharge is replaced with the O3 electro-synthesis via water-splitting with silica-coated Ni-Sb-SnO2 (NSS/SiOx), the leading-edge O3 generating anode. The E-UV/O3 showed outstanding synergetic effect with 2.5 to 3.5-fold faster removal rate of 2,6-dinitrotoluene than sum of that under electrolysis and UV radiation alone, upon wide pH range (0.4–10). The complex oxidation mechanisms during E-UV, including homogenous oxidation (by O3 and OH radical) and heterogeneous oxidation (by adsorbed active oxygen), and their contributions on the pollutant removal were identified by amperometry, electron spin resonance spectroscopy, and utilization of the quencher and probe compounds. The influence of compositions of wastewaters (pH, halide ions, and types of pollutants) on E-UV/O3 was elucidated, indicating that wastewaters with lower pH and pollutants having lower rate constants with O3 can attain the greater synergism through the E-UV/O3.

Electrochemical ultraviolet/ozone process for removing aqueous micro-pollutants

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ACS Fall 2022

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