Formation of environmentally persistent free radicals from thermochemical reactions of catechol

Linjun Qin; Lili Yang; Xiaoyun Liu; Cui Li; Bingcheng Lin; Minghui Zheng; Guorui Liu

doi:10.1016/j.scitotenv.2021.145313

Formation of environmentally persistent free radicals from thermochemical reactions of catechol

Sci Total Environ. 2021 Jun 10:772:145313. doi: 10.1016/j.scitotenv.2021.145313. Epub 2021 Feb 2.

Authors

Linjun Qin¹, Lili Yang¹, Xiaoyun Liu¹, Cui Li¹, Bingcheng Lin², Minghui Zheng³, Guorui Liu⁴

Affiliations

¹ State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
² School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310000, China.
³ State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310000, China.
⁴ State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310000, China. Electronic address: grliu@rcees.ac.cn.

PMID: 33578143
DOI: 10.1016/j.scitotenv.2021.145313

Abstract

In many anthropogenic activities, catechol as a widespread organic chemical could be released and also environmentally persistent free radicals (EPFRs) can be unintentionally formed. However, the underlying links between EPFRs and the role of catechol as an important precursor are not well understood. In this study, EPFR formation from catechol during heating was monitored online by electron paramagnetic resonance spectroscopy. It was found that catechol can produce significant amounts of EPFRs via thermochemical reactions. The EPFR species formed from catechol on metal oxides were oxygen-centered phenoxy and semiquinone radicals. Their half-lives were evaluated to be in the range of 113-909 h. The promotional effects of CaO and CuO on EPFR formation from catechol were stronger than that of Fe₂O₃. The promotional abilities and underlying mechanisms of various metal oxides in EPFR formation were clarified by X-ray photoelectron spectroscopy. Significant EPFR formation was observed during the cooling stage of a heating reaction system when CaO was used as the reaction medium. The obtained knowledge on the formation of EPFRs from catechol and the key factors involved will enable better control of the formation of EPFRs from anthropogenic activities.

Keywords: Catechol; Electron paramagnetic resonance spectroscopy; Environmentally persistent free radicals; Metal oxide; Thermochemical reaction.