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Photodegradation of microplastics by chalcopyrite and pyrite: Processes and mechanisms
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A lab study found that two common sulfide minerals, chalcopyrite and pyrite, sped up the breakdown of polystyrene microplastics under light, breaking down about a quarter of the plastic in 20 days. The minerals and plastics also affected each other chemically, with each mineral producing different reactive compounds that attacked specific chemical bonds in the plastic.
Photodegradation of microplastics (MPs) is known to occur under solar irradiation, yet how ubiquitous sulfide minerals in mine-related environments affect this photochemical behavior remains largely unexplored, especially regarding mineral–MP interfacial interactions. In this study, two typical sulfide minerals (chalcopyrite and pyrite) were selected to investigate the effects on photodegradation behavior and mechanisms of polystyrene (PS) microplastics under illumination. Results indicate that both minerals generally promote PS photodegradation, with degradation rates of 26.1% and 25.3% within 20 days, respectively. At the same time, the presence of MPs has accelerated the oxidation process of sulfide minerals, manifested as an accelerated decrease in pH, an increase in ORP, and an increase in metal leaching concentration. Spectroscopic characterization combined with EPR analysis revealed distinct pathways for reactive oxygen species (ROS) generation: chalcopyrite primarily generated superoxide radicals (•O 2 − ) via photogenerated charge carriers, whereas pyrite enhanced oxidative capacity through mineral oxidation–induced Fenton-like reactions. Further integration of 2D-FTIR-COS, GC–MS, and theoretical calculations identified the primary reaction sites for PS degradation as aromatic C H and -CH, -CH 2 on the main chain, with β-scission serving as the key chain-breaking process. This study reveals the key role of sulfide-mineral interfacial photochemistry in microplastic transformation, providing new insights into microplastic transformation in mining areas and similar reducing environments.
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Photon-induced redox chemistry on pyrite promotes photoaging of polystyrene microplastics
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Pyrite, a common mineral in lake and river sediments, was found to accelerate photoaging of polystyrene microplastics through redox reactions when exposed to sunlight, generating reactive oxygen species that oxidize the plastic surface. The finding identifies mineral-plastic interactions as an important but underappreciated driver of microplastic weathering in natural sediment environments.
Phase-dependent mechanisms in ferrihydrite photoreduction mediated by derivatives of polystyrene microplastics
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In lab tests, tiny polystyrene plastic particles and dissolved substances released from polystyrene both sped up the release of iron from a mineral called ferrihydrite when exposed to UV light. The tiny particles caused longer-lasting iron release through direct chemical bonds, while the dissolved substances caused shorter-lived effects through different chemical reactions.
Molecular transformation and photochemical reactivity of microplastic-derived dissolved organic matter on goethite: Implications for persistence and reactive oxygen species dynamics
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Researchers investigated how microplastic-derived dissolved organic matter interacts with the mineral goethite and how this affects its photochemical reactivity. They found that different plastic types produced distinct chemical behaviors: polystyrene-derived matter underwent sulfonation that enhanced reactive oxygen species formation, while polyethylene-derived matter remained relatively inert. The study suggests that microplastic-derived organic matter persists differently in soil depending on its polymer origin and mineral interactions.
Photoaging of Microplastics in the Presence of Minerals
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Sunlight breaks down plastic litter into microplastics faster when it's mixed with natural minerals like clay found in coastal sand and mud, according to new research—meaning plastic pollution on beaches and shorelines may fragment into smaller pieces more quickly than lab tests in plain water suggest. This matters because smaller microplastic fragments are more likely to be ingested by marine life and eventually end up in the food we eat, so understanding how coastal environments speed up this breakdown helps scientists better predict and manage plastic pollution's real-world impact.
Oxidative Roles of Polystyrene-Based Nanoplastics in Inducing Manganese Oxide Formation under Light Illumination
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Researchers demonstrated that polystyrene nanoplastics can generate reactive oxygen species under light illumination, driving the oxidation of dissolved manganese into manganese oxide minerals and revealing a previously unrecognized geochemical role of plastic debris.
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