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Impact of UV-B Photoaging on Chlorpyrifos Adsorption by PET Microplastics: Insights from Experimental and DFT Analysis
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Researchers studied how UV-B light aging changes the ability of PET microplastics to absorb the pesticide chlorpyrifos, combining laboratory experiments with computational modeling. They found that aging created new surface functional groups on the microplastics that significantly increased their capacity to bind the pesticide. The findings suggest that weathered microplastics in the environment may carry higher loads of harmful chemicals than fresh plastic particles.
Microplastics (MPs) in the environment pose a persistent concern, as these plastic particles can adversely impact both aquatic ecosystems and human health. MPs are subject to natural weathering and aging processes, such as photodegradation, which significantly alter their surface morphology and physicochemical properties, thereby influencing their fate, transport, and sorption behavior. To better understand how aging affects these properties and to elucidate the mechanisms behind the interactions with the chlorpyrifos pesticide, poly(ethylene terephthalate) (PET) microplastics (<100 μm) were subjected to accelerated photoaging in a UV-B chamber for varying exposure times. Several characterization techniques were employed, including scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), infrared spectroscopy (IR), point of zero charge (pHPZC), and thermogravimetric analysis (TGA). Additionally, the percentage of crystallinity and carbonyl index (CI) were calculated. The results demonstrated a decrease in pHPZC following photodegradation, likely due to an increase in δ- (-C=O) groups, consistent with the CI findings. SEM revealed surface deterioration caused by aging, while TGA indicated an early thermal degradation stage associated with water volatilization, suggesting enhanced hydrophilicity. Density functional theory (DFT) calculations showed that the PET monomer absorbs slightly in the UV-B region, leading to excitation and subsequent radical reactions that form Norrish type I products. The adsorption capacity of aged PET increased compared to the pristine material, likely due to the molecular geometry becoming more planar, facilitating interactions between the aged MPs and chlorpyrifos, as confirmed by noncovalent interaction (NCI) analysis. These findings highlight the significant potential of aged microplastics to adsorb micropollutants and act as vectors in aquatic environments.
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Researchers studied how UVB-induced photoaging changes the properties of polyethylene microplastics and their ability to absorb the pesticide chlorpyrifos. They found that aged microplastics absorbed nearly 18% more pesticide than pristine ones, due to the formation of oxygen-containing surface groups, increased surface roughness, and reduced crystallinity. The findings suggest that weathered microplastics in the environment may pose greater risks as carriers of harmful pesticides.
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This study examined how UV-B radiation ages polyethylene microplastics over time and how that aging changes their ability to adsorb the pesticide chlorpyrifos. Photoaging modified the surface chemistry and structure of the plastic, altering its interaction with the pesticide, suggesting that weathered microplastics in aquatic environments may carry different — and potentially higher — loads of toxic chemicals than fresh particles. This "Trojan horse" effect is important for understanding how microplastics contribute to broader chemical contamination of waterways.
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Researchers simulated the aging of six types of microplastics in freshwater and seawater to study how weathering affects their ability to adsorb the pesticide chlorpyrifos. The study found that UV-driven aging caused surface cracks, pores, and chemical changes in the microplastics, and the aging process increased their capacity to adsorb chlorpyrifos, suggesting that weathered microplastics in the environment may carry higher concentrations of pesticide pollutants.
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