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Visible‑light driven photocatalytic microplastic degradation using naturally occurring minerals CuO, CuFe2O4 and ZnFe2O4: from activity to mechanistic insights
Summary
Scientists found that certain natural minerals can break down plastic pollution in water using just sunlight, offering a cheap and eco-friendly way to tackle microplastics that current water treatment plants can't filter out. In lab tests, these mineral catalysts destroyed nearly half of the plastic particles within three days, and the process even worked under real outdoor sunlight, suggesting this could one day help reduce the microplastics we're exposed to through drinking water.
The sharp rise in global plastic production has led to growing concerns about the buildup of microplastics (MPs) in aquatic environments. Conventional water treatment technologies have proven inadequate for their removal, underscoring the necessity for advanced and sustainable solutions. In this study, the polyethylene (PE) MPs degradation under different lights is evaluated using green, mineral-based photocatalysts: CuO, CuFe 2 O 4 and ZnFe 2 O 4 . These semiconductors exhibit effective visible-light activation due to suitable band gap energies, enabling the generation of reactive oxygen species responsible for polymer degradation. Photocatalytic experiments demonstrate analogous initial pseudo-first-order reaction rates ranging from 2.31 10 -3 to 2.86 10 -3 min -1 for all photocatalysts under UV-A and visible light. However, long-term experiments (72 h) demonstrate a performance order of CuO>ZnFe 2 O 4 >CuFe 2 O 4 under visible light, though similar mass loss results are obtained within the range from 52.0 ± 1.4% to 44.0 ± 4.2% for all the materials. Mechanistic studies underscore distinct ROS roles: CuO activity is dominated by superoxide radicals, while CuFe 2 O 4 and ZnFe 2 O 4 proceed via combined photocatalytic and photo-Fenton-like mechanisms. Addition of H 2 O 2 serve to enhance the degradation process within ferrite systems, thereby validating their dual functionality. Finally, the activity of these materials is successfully validated under real sunlight conditions. The comprehensive evaluation of this research indicates that green mineral photocatalysts hold promise as sustainable candidates for MPs removal under visible light. These catalysts exhibit several advantageous characteristics, including significant activity in MPs degradation, recovery potential (in the case of magnetic ferrites), and a reduced environmental impact compared to conventional materials.