Metal-Catalyzed Formation of Organic Pollutants Intermediated by Organic Free Radicals

Abstract

Metal compounds play important roles in the formation of organic pollutants during thermal-related processes. However, the metal-catalyzed predominant organic pollutants have not previously been characterized nor have any detailed catalytic mechanisms been clarified. Here, we preciously distinguished the multiple organic free radical intermediates on metal catalyst surfaces during the organic pollutant formation through laboratory and theoretical studies. Differences between the organic free radical intermediate species, concentrations, and formation mechanisms under the catalysis of different metal compounds were investigated. The results were verified mutually with the differed characteristics of organic pollutant products. CuO predominantly catalyzed the formation of highly chlorinated phenoxy radical intermediates and dioxins. High proportions of semiquinone radicals and oxygen-containing derivatives were found on ZnO surfaces. Differently, methyl-substituted phenoxy radicals and long-chain products formed on Al 2 O 3 surfaces. The results will be instructive for the target emission control of priority organic pollutants during thermal-related processes rich in different metal compounds.

Atmospheric evolution of environmentally persistent free radicals in rural North China Plain: insights into water solubility and effects on PM2.5 oxidative potential

“…It is widely acknowledged that EPFRs from combustion processes are formed through the electron transfer mediated by transition metals on organic combustion byproducts such as PAHs (Liu et al, 2022a;Vejerano et al, 2018). The EPR signal of these metal-EPFRs complexes can be substantially reduced ( > 90%, Figure 5c) after acidification, as demonstrated by previous work (Guo et al, 2023).…”

Atmospheric emissions of hexachlorobutadiene in fine particulate matter from industrial sources

“…This high concentration of HCBD in EAF steelmaking could be caused by the presence of organic residues in scrap raw materials, such as rubber, cable wrapping, plastics, and polyvinyl chloride, which provide additional sources of chlorine for the unintentional formation and emission of HCBD 29 . Yang et al speculated that differences in the chlorine contents of raw materials and metal catalysts are important contributors to differences in the emissions of chlorinated organic pollutants 30 , 31 . In conjunction with the results from previous research, the large variation in HCBD concentrations among the samples could be attributed to differences in the steelmaking process.…”

Occurrence and Formation Mechanism of PCDD/Fs and SCCPs in Chlorinated Paraffin Products

“…Chlorine- and hydroxyl-substituted benzenes are the dominant precursors of PCDD/Fs and are often found as precursors of environmentally persistent free radicals . In addition, chlorophenols are widely recognized as precursors of PCDD/Fs in thermal reactions . Hence, these eight compounds detected in the raw materials used for CP production will be informative for investigating the formation of trace PCDD/Fs in the CP industry.…”

“…42 In addition, chlorophenols are widely recognized as precursors of PCDD/Fs in thermal reactions. 43 Hence, these eight compounds detected in the raw materials used for CP production will be informative for investigating the formation of trace PCDD/Fs in the CP industry.…”