Regulating Hydroxyl Radicals (^•OH) and Hydrated Electron (e_aq) for Enhanced Radiolytic Degradation of 4-Nitrophenol by Addition of H₂O₂

Ionizing radiation (IR) technology can degrade toxic organic pollutants effectively through hydroxyl radicals (•OH) and hydrated electron (eaq–) generated in the water radiolysis process. However, the treatment cost might increase due to the mutual consumption of •OH and eaq–. In this study, hydrogen peroxide (H2O2) was incorporated into the IR system to enhance its degradation efficacy to phenol compounds. The higher steady-state concentrations of •OH in the IR/H2O2 system than that of the IR system showed that H2O2 promoted the generation of •OH in the IR system. The contributions of •OH and eaq– in the degradation of 4-nitrophenol (4-NP) and phenol (PE) were evaluated, indicating that the reductive role of eaq– in the degradation process should not be overlooked. Further, the quantitative analysis of the oxidative and reductive intermediates in the 4-NP degradation process showed that H2O2 addition hindered the reductive degradation of 4-NP by eaq–, favoring oxidation by •OH. Finally, the practicality and efficiency of the IR technology for actual coking wastewater treatment was assessed.