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Much of the large quantity of plastics produced annually is discharged into the environment, where it degrades into tiny plastic debris (e.g., macro-, micro-, and nano-plastics). There are increasing concerns about the adverse effects of these plastics. In particular, nanoplastics are more prone to interacting with surrounding substances, because of their substantially larger surface areas and consequent increased exposure of surface functional groups. However, the oxidative roles of nanoplastics in inducing redox reactions with heavy or transition metals remain poorly understood. In this study, we investigated how Mn2+ was oxidized by the photolysis of polystyrene (PS)-based nanoplastics. We found that peroxyl (ROO•) and superoxide radicals (O2•−) were generated during the photolysis of PS-based nanoplastics, and they were primarily responsible for Mn oxidation. In addition, different plastic particle sizes and functional groups influenced the formation of radicals and the growth and mineral phases of Mn oxide solids. This study provides insights into the occurrence and diversity of Mn oxides in nature. These new findings also enhance our understanding of the oxidative roles of nanoplastics in generating reactive oxygen species (ROS) and how this may apply to the oxidation of other redox-active metal ions and essential chemicals, which could disrupt ecosystems and affect elemental cycling. Moreover, the production of ROS from nanoplastics in the presence of light endangers marine life and human health, and also potentially affects the mobility of the nanoplastics in the environment via redox reactions, which in turn might negatively impact their environmental remediation.
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Oxidative Roles of Polystyrene-Based Nanoplastics in Inducing Manganese Oxide Formation under Light Illumination
Every year, large quantities of plastics are produced and used for diverse applications, growing concerns about the waste management of plastics and their release into the environment. Plastic debris can break down into millions of pieces that adversely affect natural organisms. In particular, the photolysis of micro/nanoplastics can generate reactive oxygen species (ROS). However, their oxidative roles in initiating redox chemical reactions with heavy and transition metals have received little attention. In this study, we investigated whether the photolysis of polystyrene (PS) nanoplastics can induce the oxidation of Mn2+(aq) to Mn oxide solids. We found that PS nanoplastics not only produced peroxyl radicals (ROO•) and superoxide radicals (O2•−) by photolysis, which both play a role in unexpected Mn oxidation, but also served as a substrate for facilitating the heterogeneous nucleation and growth of Mn oxide solids and controlling the formation rate and crystalline phases of Mn oxide solids. These findings help us to elucidate the oxidative roles of nanoplastics in the oxidation of redox-active metal ions. The production of ROS from nanoplastics in the presence of light can endanger marine life and human health, and affect the mobility of the nanoplastics in the environment via redox reactions, which in turn may negatively impact their environmental remediation.
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- Award ID(s):
- 1905077
- PAR ID:
- 10482876
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Nano
- Volume:
- 16
- Issue:
- 12
- ISSN:
- 1936-0851
- Page Range / eLocation ID:
- 20238 to 20250
- Subject(s) / Keyword(s):
- nanoplastics photochemistry abiotic Mn2+ oxidation heterogeneous nucleation peroxyl radicals superoxide radicals
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acsnano.2c05803
