Regulating Hydroxyl\nRadicals (<sup>•</sup>OH)\nand Hydrated Electron (e<sub>aq</sub>) for Enhanced Radiolytic Degradation\nof 4‑Nitrophenol by Addition of H<sub>2</sub>O<sub>2</sub>

Ionizing radiation (IR) technology can degrade toxic\norganic pollutants\neffectively through hydroxyl radicals (<sup>•</sup>OH) and\nhydrated electron (e<sub>aq</sub><sup>–</sup>) generated in\nthe water radiolysis process. However, the treatment cost might increase\ndue to the mutual consumption of <sup>•</sup>OH and e<sub>aq</sub><sup>–</sup>. In this study, hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) was incorporated into the IR system to enhance its\ndegradation efficacy to phenol compounds. The higher steady-state\nconcentrations of <sup>•</sup>OH in the IR/H<sub>2</sub>O<sub>2</sub> system than that of the IR system showed that H<sub>2</sub>O<sub>2</sub> promoted the generation of <sup>•</sup>OH in\nthe IR system. The contributions of <sup>•</sup>OH and e<sub>aq</sub><sup>–</sup> in the degradation of 4-nitrophenol (4-NP)\nand phenol (PE) were evaluated, indicating that the reductive role\nof e<sub>aq</sub><sup>–</sup> in the degradation process should\nnot be overlooked. Further, the quantitative analysis of the oxidative\nand reductive intermediates in the 4-NP degradation process showed\nthat H<sub>2</sub>O<sub>2</sub> addition hindered the reductive degradation\nof 4-NP by e<sub>aq</sub><sup>–</sup>, favoring oxidation by <sup>•</sup>OH. Finally, the practicality and efficiency of the\nIR technology for actual coking wastewater treatment was assessed.