Unexpected catalytic influence of atmospheric pollutants on the formation of environmentally persistent free radicals

Wang, Li; Liang, Dandan; Liu, Jiarong; Du, Lin; Vejerano, Eric P.; Zhang, Xiuhui

doi:10.1016/j.chemosphere.2022.134854

Cited by 7 publications

(4 citation statements)

References 67 publications

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“…Hence, considering the “indifferent” behavior of MCP230 EPFR generation in relation to catalyst morphologies, we tend to favor the idea that multiple mechanisms, running parallel to the conventional EPFR generation model, are in operation. Several publications have recently raised the importance of numerous alternative pathways for the formation of EPFRs. ,,,,, The role of a trace amount of oxygen in the formation of EPFRs was advocated in ref for phenoxy radicals from exposure to metal oxide surface by benzene. A hypothesis was reported recently by Mocarelo about the critical role of adsorbed superoxide species in the formation of EPFRs.…”

Section: Resultsmentioning

confidence: 99%

“…It is also vital to consider the effect of metal surface defects and oxygen vacancies on the formation of EPFRs, which has been shown recently during the process of formation of EPFRs on ZnO surfaces . The acidity/basicity character of the surface to initiate EPFR generation was reported in ref .…”

Section: Resultsmentioning

confidence: 99%

“…Several publications have recently raised the importance of numerous alternative pathways for the formation of EPFRs. 5,6,36,55,56,24 The role of a trace amount of oxygen in the formation of EPFRs was advocated in ref 5 for phenoxy radicals from exposure to metal oxide surface by benzene. A hypothesis was reported recently by Mocarelo 55 about the critical role of adsorbed superoxide species in the formation of EPFRs.…”

Section: Degree Of Hydroxylation Of the Catalyst Hasmentioning

confidence: 99%

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New Features of Laboratory-Generated EPFRs from 1,2-Dichlorobenzene (DCB) and 2-Monochlorophenol (MCP)

Khachatryan,

Rezk,

Nde

et al. 2024

ACS Omega

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The present research is primarily focused on investigating the characteristics of environmentally persistent free radicals (EPFRs) generated from commonly recognized aromatic precursors, namely, 1,2-dichlorobenzene (DCB) and 2monochlorophenol (MCP), within controlled laboratory conditions at a temperature of 230 °C, termed as DCB230 and MCP230 EPFRs, respectively. An intriguing observation has emerged during the creation of EPFRs from MCP and DCB utilizing a catalyst 5% CuO/SiO 2 , which was prepared through various methods. A previously proposed mechanism, advanced by Dellinger and colleagues (a conventional model), postulated a positive correlation between the degree of hydroxylation on the catalyst's surface (higher hydroxylated, HH and less hydroxylated, LH) and the anticipated EPFR yields. In the present study, this correlation was specifically confirmed for the DCB precursor. Particularly, it was observed that increasing the degree of hydroxylation at the catalyst's surface resulted in a greater yield of EPFRs for DCB230. The unexpected finding was the indifferent behavior of MCP230 EPFRs to the surface morphology of the catalyst, i.e., no matter whether copper oxide nanoparticles are distributed densely, sparsely, or completely agglomerated. The yields of MCP230 EPFRs remained consistent regardless of the catalyst type or preparation protocol. Although current experimental results confirm the early model for the generation of DCB EPFRs (i.e., the higher the hydroxylation is, the higher the yield of EPFRs), it is of utmost importance to closely explore the heterogeneous alternative mechanism(s) responsible for generating MCP230 EPFRs, which may run parallel to the conventional model. In this study, detailed spectral analysis was conducted using the EPR technique to examine the nature of DCB230 EPFRs and the aging phenomenon of DCB230 EPFRs while they exist as surface-bound o-semiquinone radicals (o-SQ) on copper sites. Various aspects concerning bound radicals were explored, including the hydrogen-bonding tendencies of o-semiquinone (o-SQ) radicals, the potential reversibility of hydroxylation processes occurring on the catalyst's surface, and the analysis of selected EPR spectra using EasySpin MATLAB. Furthermore, alternative routes for EPFR generation were thoroughly discussed and compared with the conventional model.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Degree Of Hydroxylation Of the Catalyst Hasmentioning

confidence: 99%

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New Features of Laboratory-Generated EPFRs from 1,2-Dichlorobenzene (DCB) and 2-Monochlorophenol (MCP)

Khachatryan,

Rezk,

Nde

et al. 2024

ACS Omega

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“…Apart from metal oxides, organic precursors that can interact with them also have a significant influence on the formation process of EPFRs. Numerous studies have found that C 6 H 5 OH is one of the most primary organic precursors contributing to EPFRs formation; meanwhile, it widely exists in the atmospheric environment with a simple molecular structure. − Therefore, C 6 H 5 OH was selected as the precursor for EPFRs formation in this study.…”

Section: Introductionmentioning

confidence: 99%

Formation Mechanism of Environmentally Persistent Free Radicals on Alkaline Earth Oxide Surfaces

Liang,

Liu,

Feng

et al. 2024

J. Phys. Chem. A

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The formation of environmentally persistent free radicals (EPFRs) is usually related to transition-metal oxides in particulate matter (PM). However, recent studies suggest that alkaline-earth-metal oxides (AEMOs) in PM also influence EPFRs formation, but the exact mechanism remains unclear. Here, density functional theory calculations were performed to investigate the formation mechanism of EPFRs by C 6 H 5 OH on AEMO (MgO, CaO, and BaO) surfaces and compare it with that on transitionmetal oxide (ZnO and CuO) surfaces. Results indicate that EPFRs can be rapidly formed on AEMOs by dissociative adsorption of C 6 H 5 OH, accompanied by electrons transfer. As the alkalinity of AEMOs increases, both adsorption energy and the number of electron transfers gradually increase. Also, the stability of the formed EPFRs is mainly attributed to the electrostatic and van der Waals interactions between the phenoxy radical and surfaces. Notably, the formation mechanism of EPFRs on AEMOs is similar to that on ZnO but differs from that on CuO, as suggested through geometric structure and charge distribution analyses. This study not only elucidates the formation mechanisms of EPFRs on AEMOs but also provides theoretical insights into addressing EPFRs pollution.

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Formation of environmentally persistent free radicals and their risks for human health: a review

Wang,

Liu,

Xue

et al. 2024

Environ Chem Lett

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Unexpected catalytic influence of atmospheric pollutants on the formation of environmentally persistent free radicals

Cited by 7 publications

References 67 publications

New Features of Laboratory-Generated EPFRs from 1,2-Dichlorobenzene (DCB) and 2-Monochlorophenol (MCP)

New Features of Laboratory-Generated EPFRs from 1,2-Dichlorobenzene (DCB) and 2-Monochlorophenol (MCP)

Formation Mechanism of Environmentally Persistent Free Radicals on Alkaline Earth Oxide Surfaces

Formation of environmentally persistent free radicals and their risks for human health: a review

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