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Carrier effects of face mask-derived microplastics on metal ions: Enhanced adsorption by photoaging combined with biofilms, exemplified with Pb(Ⅱ)
Summary
Researchers investigated how photoaging and biofilm formation on face mask-derived microplastics enhance their ability to adsorb heavy metals like lead. They found that the combination of UV weathering and microbial biofilm growth significantly increased the metal-binding capacity of both polypropylene and polyurethane mask particles. The study highlights that discarded face masks in the environment may pose compounding pollution risks by concentrating toxic metals on their surfaces.
Face masks have emerged as a significant source of microplastics (MPs) under the influence of biotic and abiotic interactions. However, the combined effects of abiotic photoaging and biofilm-loading on mask-derived MPs as carriers of metal ions are not clear. We investigated the Pb(Ⅱ) adsorption onto polypropylene (PP) and polyurethane (PU) mask-derived MPs treated by photoaging, biofilm-loading, and both combinations, evaluating the composite risks. PU mask-derived MPs (1.157.47 mg/g) exhibited greater Pb(Ⅱ) adsorption capacity than PP mask-derived MPs (0.842.08 mg/g) because of the presence of intrinsic carbonyl functional groups. Photoaging (30.5%, 88.4%), biofilm-loading (110.7%, 87.1%), and both combinations (146.7%, 547.0%) of PP and PU masks enhanced Pb(Ⅱ) adsorption compared to virgin mask-derived MPs due to the increase of oxygen-containing functional groups. High-throughput sequencing indicated that the structural morphology and chemical composition of masks significantly affected the microbial community. Adsorption mechanisms involved electrostatic force and surface complexation. A combination of photoaging and biofilms increased the ecological risk index of mask-derived MPs in freshwater, showing the risk level to be high (PP mask) and very high (PU mask). This research highlights the crucial role of photoaging combined with biofilms in controlling metal ion adsorption onto mask-derived MPs, thereby increasing the composite risks.