title: Why Does 2,3,5,6-Tetrachlorophenol Generate the Strongest Intrinsic Chemiluminescence among All Nineteen Chlorophenolic Persistent Organic Pollutants during Environmentally-friendly Advanced Oxidation Process?
abstract: We found recently that intrinsic chemiluminescence (CL) could be produced by all 19 chlorophenolic persistent organic pollutants during environmentally-friendly advanced oxidation processes. Interestingly and unexpectedly, the strongest CL was produced not by the most-highly chlorinated pentachlorophenol (PCP), but rather by the less chlorinated 2,3,5,6-tetrachlorophenol (2,3,5,6-TeCP), one of the three tetrachlorophenol (TeCPs) isomers. However, it remains unclear what is the underlying molecular mechanism. Here we show that not only chlorinated quinoid intermediates, but more interestingly, semiquinone radicals were produced during the degradation of the three TeCPs and PCP by Fenton reagents, and the type and yield of which were found to be well correlated with CL generation. We propose that hydroxyl radical-dependent formation of more tetrachlorinated quinoids, quinone-dioxetanes and electronically excited carbonyl species might be responsible for the exceptionally strong CL production by 2,3,5,6-TeCP as compared to PCP and its two isomers. This is the first report showing the critical role of quinoid intermediates and semiquinone radicals in CL generation from polychlorinated phenols and Fenton system. These new findings may have broad chemical and environmental implications for future studies on remediation of other halogenated persistent aromatic pollutants by advanced oxidation processes.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, P. R. China.|University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
authors.forename: Hui-Ying
authors.initials: HY
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, P. R. China.|University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
authors.forename: Li
authors.initials: L
authors.lastname: Mao
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, P. R. China.|University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
authors.forename: Bo
authors.initials: B
authors.lastname: Shao
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, P. R. China.|University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
authors.forename: Chun-Hua
authors.initials: CH
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, P. R. China.|University of Chinese Academy of Sciences, Beijing 100049, P. R. China.|Linus Pauling Institute, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Ben-Zhan
authors.initials: BZ
authors.lastname: Zhu
mesh_terms: D002733:Chlorophenols / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry*; D049449:Luminescence; D010084:Oxidation-Reduction
chemical_list: D002733:Chlorophenols; D004785:Environmental Pollutants; C039673:2,3,5,6-tetrachlorophenate