Regulating Hydroxyl Radicals (<sup>•</sup>OH) and Hydrated Electron (e<sub>aq</sub>) for Enhanced Radiolytic Degradation of 4-Nitrophenol by Addition of H<sub>2</sub>O<sub>2</sub>
Cheng Feng, Jianlong Wang
Abstract
Ionizing radiation (IR) technology can degrade toxic organic pollutants effectively through hydroxyl radicals ( • OH) and hydrated electron (e aq – ) generated in the water radiolysis process. However, the treatment cost might increase due to the mutual consumption of • OH and e aq – . In this study, hydrogen peroxide (H 2 O 2 ) was incorporated into the IR system to enhance its degradation efficacy to phenol compounds. The higher steady-state concentrations of • OH in the IR/H 2 O 2 system than that of the IR system showed that H 2 O 2 promoted the generation of • OH in the IR system. The contributions of • OH and e aq – in the degradation of 4-nitrophenol (4-NP) and phenol (PE) were evaluated, indicating that the reductive role of e aq – 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 H 2 O 2 addition hindered the reductive degradation of 4-NP by e aq –, favoring oxidation by • OH. Finally, the practicality and efficiency of the IR technology for actual coking wastewater treatment was assessed.