Unveiling the activity difference cause and ring-opening reaction routes of typical radicals induced degradation of toluene

Zhen Qian; Yongxue Guo; Mengchao Luo; Lijuan Yang; Siqi Liu; Peng Qin; Bo Yuan; Feng Liu; Runlong Hao

doi:10.1016/j.jhazmat.2024.134273

Unveiling the activity difference cause and ring-opening reaction routes of typical radicals induced degradation of toluene

J Hazard Mater. 2024 Jun 5:471:134273. doi: 10.1016/j.jhazmat.2024.134273. Epub 2024 Apr 12.

Authors

Zhen Qian¹, Yongxue Guo¹, Mengchao Luo², Lijuan Yang³, Siqi Liu², Peng Qin², Bo Yuan¹, Feng Liu¹, Runlong Hao⁴

Affiliations

¹ Hebei Key Lab of Power Plant Flue Gas Multi-Pollutants Control, Department of Environmental Science and Engineering, North China Electric Power University, Baoding 071003, PR China; MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, PR China.
² Hebei Key Lab of Power Plant Flue Gas Multi-Pollutants Control, Department of Environmental Science and Engineering, North China Electric Power University, Baoding 071003, PR China.
³ Hebei Key Lab of Power Plant Flue Gas Multi-Pollutants Control, Department of Environmental Science and Engineering, North China Electric Power University, Baoding 071003, PR China; MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, PR China. Electronic address: lisayangtony@163.com.
⁴ Hebei Key Lab of Power Plant Flue Gas Multi-Pollutants Control, Department of Environmental Science and Engineering, North China Electric Power University, Baoding 071003, PR China; MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, PR China. Electronic address: hrl_ncepu@hotmail.com.

PMID: 38653137
DOI: 10.1016/j.jhazmat.2024.134273

Abstract

This study employs five UV-AOPs (PMS, PDS, H₂O₂, NaClO and NaClO₂) to produce radicals (•OH, SO₄^•-, ClO•, O₂^•- and ¹O₂) and further comparatively studies their activity sequence and activity difference cause in toluene degradation. The toluene mineralization efficiency as a descending order is 73 % (UV-PMS) > 71 % (UV-PDS) > 70 % (acidified-UV-NaClO) > 55 % (UV-H₂O₂) > 36 % (UV-NaClO) > 35 % (UV-NaClO₂); that of conversion efficiency is 99 % (acidified-UV-NaClO) > 95 % (UV-PMS) > 90 % (UV-PDS) > 74 % (UV-H₂O₂) > 44 % (UV-NaClO) > 41 % (UV-NaClO₂). Acidic pretreatment significantly boosts the reactivity of UV-NaClO. ESR combined with radical quenching tests reveals the radicals' generation and evolution, and their contribution rates to toluene conversion, i.e. ClO• > SO₄^•- > O₂^•- > ¹O₂ > •OH. Theoretical calculations further unveil the ring-opening reaction routes and the nature of the activity difference of different radicals. The minimum energy required for ring-opening reaction is 116.77, 150.63, 168.29 and 191.92 kJ/mol with respect to ClO•, SO₄^•-, ¹O₂ and •OH, and finding that the ClO•-HO• pair is the best for toluene mineralization. The difficulty for eliminating typical VOCs by using UV-AOPs method is determined as toluene > chlorobenzene > benzene > ethyl acetate.

Keywords: Radicals; Reaction route; Theoretical calculation; Toluene; UV-AOPs; VOCs elimination.