TY - JOUR
T1 - ROS-mediated photoaging pathways of nano- and micro-plastic particles under UV irradiation
AU - Duan, Jiajun
AU - Li, Yang
AU - Gao, Jianan
AU - Cao, Runzi
AU - Shang, Enxiang
AU - Zhang, Wen
N1 - Funding Information:
The study was financially supported by the Fund for National Key R&D Program of China ( 2021YFC3200401 ), National Natural Science Foundation of China (No. 52170024 , 21677015 and No. 22006031 ), New Jersey Water Resources Research Institute (NJWRRI) Grant (Project Number: 2018NJ399B ), and the Natural Science Foundation of Hebei Province (No. B2019204315 ).
Publisher Copyright:
© 2022 Elsevier Ltd
PY - 2022/6/1
Y1 - 2022/6/1
N2 - Reactive oxygen species (ROS) generation is considered as an important photoaging mechanism of microplastics (MPs) and nanoplastics (NPs). To elucidate the ROS-induced MP/NP aging processes in water under UV365 irradiation, we examined the effects of surface coatings, polymer types and grain sizes on ROS generation and photoaging intermediates. Bare polystyrene (PS) NPs generated hydroxyl radicals (•OH) and singlet oxygen (1O2), while coated PS NPs (carboxyl-modified PS (PS-COOH), amino-modified PS (PS-NH2)) and PS MPs generated fewer ROS due to coating scavenging or size effects. Polypropylene, polyethylene, polyvinyl chloride, polyethylene terephthalate and polycarbonate MPs only generated •OH. For aromatic polymers, •OH addition preferentially occurred at benzene rings to form monohydroxy polymers. Excess •OH resulted in H abstraction, C–C scission and phenyl ring opening to generate aliphatic ketones, esters, aldehydes, and aromatic ketones. For coated PS NPs, •OH preferentially attacked the surface coatings to result in decarboxylation and deamination reactions. For aliphatic polymers, •OH attack resulted in the formation of carbonyl groups from peracid, aldehyde or ketone via H abstraction and C–C scission. Moreover, 1O2 might participate in phenyl ring opening for PS NPs and coating degradation for coated PS NPs. This study facilitates understanding the ROS-induced weathering process of NPs/MPs in water under UV irradiation.
AB - Reactive oxygen species (ROS) generation is considered as an important photoaging mechanism of microplastics (MPs) and nanoplastics (NPs). To elucidate the ROS-induced MP/NP aging processes in water under UV365 irradiation, we examined the effects of surface coatings, polymer types and grain sizes on ROS generation and photoaging intermediates. Bare polystyrene (PS) NPs generated hydroxyl radicals (•OH) and singlet oxygen (1O2), while coated PS NPs (carboxyl-modified PS (PS-COOH), amino-modified PS (PS-NH2)) and PS MPs generated fewer ROS due to coating scavenging or size effects. Polypropylene, polyethylene, polyvinyl chloride, polyethylene terephthalate and polycarbonate MPs only generated •OH. For aromatic polymers, •OH addition preferentially occurred at benzene rings to form monohydroxy polymers. Excess •OH resulted in H abstraction, C–C scission and phenyl ring opening to generate aliphatic ketones, esters, aldehydes, and aromatic ketones. For coated PS NPs, •OH preferentially attacked the surface coatings to result in decarboxylation and deamination reactions. For aliphatic polymers, •OH attack resulted in the formation of carbonyl groups from peracid, aldehyde or ketone via H abstraction and C–C scission. Moreover, 1O2 might participate in phenyl ring opening for PS NPs and coating degradation for coated PS NPs. This study facilitates understanding the ROS-induced weathering process of NPs/MPs in water under UV irradiation.
KW - Microplastics
KW - Nanoplastics
KW - Photoaging
KW - Reactive oxygen species
KW - Surface coating
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U2 - 10.1016/j.watres.2022.118320
DO - 10.1016/j.watres.2022.118320
M3 - Article
C2 - 35339969
AN - SCOPUS:85126882286
SN - 0043-1354
VL - 216
JO - Water Research
JF - Water Research
M1 - 118320
ER -