Water Vapor Condensation on Iron Minerals Spontaneously Produces Hydroxyl Radical

The hydroxyl radical (•OH) is a potent oxidant and key reactive species in mediating element cycles and pollutant dynamics in the natural environment. The natural source of •OH is historically linked to photochemical processes (e.g., photoactivation of natural organic matter or iron minerals) or red...

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Published in:Environmental science & technology 2023-06, Vol.57 (23), p.8610-8616
Main Authors: Pan, Yishuai, Zheng, Xiaoshan, Zhao, Guoqiang, Rao, Zepeng, Yu, Wanchao, Chen, Baoliang, Chu, Chiheng
Format: Article
Language:English
Subjects:
Biogeochemical Cycling
Bisphenol A
Carbamazepine
Chemical reactions
Condensates
Condensation
Earth surface
Evaporation
Goethite
Hematite
Hydrogen peroxide
Hydroxyl radicals
Hydroxylation
Iron
Magnetite
Minerals
Natural environment
Organic carbon
Organic matter
Oxidants
Oxidizing agents
Photoactivation
Photochemicals
Pollutants
Sediments
Water vapor
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Summary:The hydroxyl radical (•OH) is a potent oxidant and key reactive species in mediating element cycles and pollutant dynamics in the natural environment. The natural source of •OH is historically linked to photochemical processes (e.g., photoactivation of natural organic matter or iron minerals) or redox chemical processes (e.g., reaction of microbe-excreted or reduced iron/natural organic matter/sulfide-released electrons with O2 in soils and sediments). This study revealed a ubiquitous source of •OH production via water vapor condensation on iron mineral surfaces. Distinct •OH productions (15–478 nM via water vapor condensation) were observed on all investigated iron minerals of abundant natural occurrence (i.e., goethite, hematite, and magnetite). The spontaneous •OH productions were triggered by contact electrification and Fenton-like activation of hydrogen peroxide (H2O2) at the water–iron mineral interface. Those •OH drove efficient transformation of organic pollutants associated on iron mineral surfaces. After 240 cycles of water vapor condensation and evaporation, bisphenol A and carbamazepine degraded by 25%–100% and 16%–51%, respectively, forming •OH-mediated arene/alkene hydroxylation products. Our findings largely broaden the natural source of •OH. Given the ubiquitous existence of iron minerals on Earth’s surface, those newly discovered •OH could play a role in the transformation of pollutants and organic carbon associated with iron mineral surfaces.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.3c01379