Accurate identification of radicals by in-situ electron paramagnetic resonance in ultraviolet-based homogenous advanced oxidation processes

Chen，Long1; Duan，Jun1; Du，Penghui2; Sun，Weiliang3; Lai，Bo4; Liu，Wen1

2022-08-01

10.1016/j.watres.2022.118747

WATER RESEARCH   Impact Factor & Quartile

0043-1354

1879-2448

Accurate identification of radicals in advanced oxidation processes (AOPs) is important to study the mechanisms on radical production and subsequent oxidation-reduction reaction. The commonly applied radical quenching experiments cannot provide direct evidences on generation and evolution of radicals in AOPs, while electron paramagnetic resonance (EPR) is a cutting-edge technology to identify radicals based on spectral characteristics. However, the complexity of EPR spectrum brings uncertainty and inconsistency to radical identification and mechanism clarification. This work presented a comprehensive study on identification of radicals by in-situ EPR analysis in four typical UV-based homogenous AOPs, including UV/HO, UV/peroxodisulfate (and peroxymonosulfate), UV/peracetic acid and UV/IO systems. Radical formation mechanism was also clarified based on EPR results. A reliable EPR method using organic solvents was proposed to identify alkoxy and alkyl radicals (CHC(=O)OO·, CHC(=O)O· and ·CH) in UV/PAA system. Two activation pathways for radical production were proposed in UV/IO system, in which the produced IO·, IO·, ·OH and hydrated electron were precisely detected. It is interesting that addition of specific organic solvents can effectively identify oxygen-center and carbon-center radicals. A key parameter in EPR spectrum for 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin adduct, A, is ranked as: ·CH (23 G) >·OH (15 G) >IO· (12.9 G) >O· (11 G) ≥·OOH (9–11 G) ≥IO· (9–10 G) ≥SO· (9–10 G) >CHC(=O)OO· (8.5 G) > CHC(=O)O· (7.5 G). This study will give a systematic method on identification of radicals in AOPs, and shed light on the insightful understanding of radical production mechanism.

Advanced oxidation processes Electron paramagnetic resonance Homogeneous Radical Ultraviolet

SCI ; EI

English

NI Journal Papers ; ESI Hot Papers ; ESI Highly Cited Papers

Others

China Postdoctoral Science Foundation[2021M690208];China Postdoctoral Science Foundation[2021M700213];National Key Research and Development Program of China Stem Cell and Translational Research[2021YFA1202500];National Natural Science Foundation of China[21906001];National Natural Science Foundation of China[51721006];Beijing Nova Program[Z191100001119054];

Engineering ; Environmental Sciences & Ecology ; Water Resources

Engineering, Environmental ; Environmental Sciences ; Water Resources

WOS:000835552300003

PERGAMON-ELSEVIER SCIENCE LTD

20222612277445

Electron resonance ; Electron spin resonance spectroscopy ; Electrons ; Organic solvents ; Oxidation ; Paramagnetism ; Redox reactions

Magnetism: Basic Concepts and Phenomena:701.2 ; Chemistry:801 ; Chemical Reactions:802.2 ; Chemical Agents and Basic Industrial Chemicals:803 ; Organic Compounds:804.1

ENVIRONMENT/ECOLOGY

2-s2.0-85132722867

Scopus

1.The Key Laboratory of Water and Sediment Sciences,Ministry of Education,College of Environmental Sciences and Engineering,Peking University,Beijing,100871,China
2.State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control,School of Environmental Science and Engineering,Southern University of Science and Technology,Shenzhen,518055,China
3.Department of Civil and Environmental Engineering,Louisiana State University,Baton Rouge,70803,United States
4.State Key Laboratory of Hydraulics and Mountain River Engineering,College of Architecture and Environment,Sichuan University,Chengdu,610065,China

Chen，Long,Duan，Jun,Du，Penghui,et al. Accurate identification of radicals by in-situ electron paramagnetic resonance in ultraviolet-based homogenous advanced oxidation processes[J]. WATER RESEARCH,2022,221.

Chen，Long,Duan，Jun,Du，Penghui,Sun，Weiliang,Lai，Bo,&Liu，Wen.(2022).Accurate identification of radicals by in-situ electron paramagnetic resonance in ultraviolet-based homogenous advanced oxidation processes.WATER RESEARCH,221.

Chen，Long,et al."Accurate identification of radicals by in-situ electron paramagnetic resonance in ultraviolet-based homogenous advanced oxidation processes".WATER RESEARCH 221(2022).