Pivotal Roles of Metal Oxides in the Formation of Environmentally Persistent Free Radicals

Yang, Li; Liu, Guorui; Jin, Rui-Bo; Zhao, Yuyang; Wu, Xinke; Xu, Yang

doi:10.1021/acs.est.7b03583

Cited by 102 publications

(82 citation statements)

References 40 publications

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“…In addition, ZnO is an intrinsic semiconductor and can produce intrinsic defectivity at higher temperatures (D'Arienzo et al 2019;Özgür et al 2005). We detected the hole of ZnO by electron paramagnetic resonance (Table 1); this hole can result in electron transfer to the precursors, accelerating the formation and stabilization of the intermediate radicals (D'Arienzo et al 2019;Yang et al 2017a), which can further dimerize to form Cl-PAHs. Therefore, the concentrations of intermediate radicals catalyzed by ZnO were relatively higher than those of radicals catalyzed by CuO, contributing to the relatively higher concentrations of Cl-PAHs, polychlorinated naphthalenes (Liu et al 2014), and polychlorinated biphenyls (Liu et al 2013) on the surface of ZnO particles.…”

Section: Congener Pro Les Of Cl/br-pahs From Sezn Smelting Plants and Implications For The Dominant Formation Mechanismsmentioning

confidence: 99%

“…Organic radicals are important intermediates in the formation of persistent organic pollutants from precursors during thermal processes (Yang et al 2017c;Zhao et al 2020), and zinc oxide (ZnO) is known to catalyze the formation of those organic radical intermediates (Yang et al 2017a). The catalytic capacity of ZnO during the formation of dioxins has been con rmed, and the emissions of dioxins from secondary zinc (SeZn) smelting activities have been shown to be comparable to those from SeCu and SeAl smelting and much higher than dioxin emissions from thermal processes such as municipal solid waste incineration and steelmaking (Liu et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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Discovery of Significant Emission of Halogenated Polycyclic Aromatic Hydrocarbons From Secondary Zinc Smelting

Yang

Liu

et al. 2021

Preprint

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Chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/Br-PAHs) are persistent organic pollutants, and controlling their adverse effects requires the identification of their sources. However, current knowledge on the formations of Cl/Br-PAHs is far insufficient for source control, much less on their formation mechanisms. In this field study, we firstly discovered secondary zinc smelting as a significant source of Cl/Br-PAHs. The mean concentration of Cl/Br-PAHs emitted in stack gas from secondary zinc smelting was 9,553 ng/m3, exceeding concentrations from other metal smelting sources by one or two orders of magnitude. Cl/Br-PAHs with fewer rings were the dominant congeners in stack gas from secondary zinc smelting and secondary copper smelting. However, emissions from secondary aluminum smelting were dominated by congeners with more rings. The differences in congener profiles were attributable to the catalytic effects of metal compounds during smelting activities. Zinc oxide and copper oxide dominantly catalyzed dehydrogenation reactions, contributing to the formation of intermediate radicals and subsequent dimerization to Cl/Br-PAHs with fewer rings. Aluminum oxide induced alkylation reactions and accelerated ring growth, resulting in the formation of Cl-PAHs with more rings. The newly proposed mechanisms can successfully explain the emission characteristics of Cl/Br-PAHs during smelting activities and the higher concentrations of Cl/Br-PAHs from secondary zinc smelting, which should be useful in targeted source control.

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Section: Congener Pro Les Of Cl/br-pahs From Sezn Smelting Plants and Implications For The Dominant Formation Mechanismsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Discovery of Significant Emission of Halogenated Polycyclic Aromatic Hydrocarbons From Secondary Zinc Smelting

Yang

Liu

et al. 2021

Preprint

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“…Yang et al. [ 144 ] using 2,4‐dichloro‐1‐naphthol as precursor, investigated the effect of different metal oxides (Al 2 O 3 , ZnO, and NiO) on the formation of surface‐bound PFRs with the precursor. The spectra obtained with catalysis by different metal oxides resulted in the formation of different PFRs.…”

Section: Conversion Of Biomasses Into Biochar Catalystsmentioning

confidence: 99%

Hydrothermal and Pyrolytic Conversion of Biomasses into Catalysts for Advanced Oxidation Treatments

Zheng

et al. 2020

Adv Funct Materials

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Biomasses are very important natural products. Transferring biomass into catalysts for the advanced oxidation process (AOP) via heat treatment has attracted extensive attention. This review systematically introduces and summarizes two kinds of innovative biomass‐based catalysts according to the treating temperature. At low temperature (<300 °C), biomasses are converted into hydrothermal carbonation carbon (HTCC) with semiconductive properties for photocatalysis application. At high temperature (>300 °C), by contrast, the products lose their semiconductive nature and become a conductive carbon‐based conductor (biochar). They usually work as AOP catalysts by activating oxidant of O2, H2O2, and peroxysulfate for environmental treatment. This review summarizes and compares HTCC and biochar according to their formation process, structure, catalytic mechanism, and key points for the activity enhancement. The active units in HTCC are the sp2‐hybridized polyfuran unit while those in biochar are the persistent free radicals, nitrogen‐containing unit, or defects. HTCC converts water into OH radicals by using the photoexcited electron/hole pairs induced by solar illumination, while biochar activates oxidants via the active unit on its surface. More importantly, this review summarizes and demonstrates the key points to obtain high‐efficiency HTCC and biochar catalysts. Finally, conclusions are drawn and the future aspects for biomass‐based catalysis are given.

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“…The variations are caused not only by the different meteorological conditions (e.g., humidity, temperature) but also by the presence of different sources (Ravindra et al, 2008;Tian et al, 2009). Although previous studies have con rmed that PAHs can form EPFRs during photochemical reaction or oxidation by O 3 in laboratory condition, the relationship between EPFRs and PAHs in actual atmospheric is still unknown (Borrowman et al, 2016;D'Arienzo et al, 2017;Jia et al, 2016;Jia et al, 2017;Jia et al, 2019b;Jia et al, 2018;Yang et al, 2017a). Moreover, PAHs from different sources have different congener compositions which is also a key factor in the relationships.…”

Section: Introductionmentioning

confidence: 99%

Characteristics and Sources of Environmentally Persistent Free Radicals in PM2.5 in Dalian: Important Role of Polycyclic Aromatic Hydrocarbons

Zhao

et al. 2021

Preprint

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Environmentally persistent free radicals (EPFRs) are an emerging class of environmental hazardous contaminants that extensively, stably exist in airborne particulate matter and pose harmful effects on human health. However, there was little research about the sources of EPFRs in actual atmospheric conditions. This study reported the occurrence, characteristics and sources of EPFRs and polycyclic aromatic hydrocarbons (PAHs) in PM2.5 collected in Dalian, China. The concentrations of PM2.5-bound EPFRs ranged from 1.13×1013 to 8.97×1015 spins/m3 (mean value: 1.14×1015 spins/m3). Carbon-centered radicals and carbon-centered radicals with adjacent oxygen atoms were detected. The concentration of ∑PAHs ranged from 1.09 to 76.24 ng/m3 and PAHs with high molecular weight (HMW) were predominant species in PM2.5. The correlation analysis and PMF result showed that coal and biomass combustion are the top contributors to EPFR, followed by vehicle emission. The secondary sources to EFPRs was negligible. The finding of present study provides an important evidence for further study on the formation mechanism of EPFRs in actual atmospheric to control the air pollution.

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Pivotal Roles of Metal Oxides in the Formation of Environmentally Persistent Free Radicals

Cited by 102 publications

References 40 publications

Discovery of Significant Emission of Halogenated Polycyclic Aromatic Hydrocarbons From Secondary Zinc Smelting

Discovery of Significant Emission of Halogenated Polycyclic Aromatic Hydrocarbons From Secondary Zinc Smelting

Hydrothermal and Pyrolytic Conversion of Biomasses into Catalysts for Advanced Oxidation Treatments

Characteristics and Sources of Environmentally Persistent Free Radicals in PM2.5 in Dalian: Important Role of Polycyclic Aromatic Hydrocarbons

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