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Enhanced photocatalytic degradation of polyethylene terephthalate microplastic via BiOCl0.5I0.5 solid solution-mediated activation of H2O2
Summary
Scientists have developed a new material that uses light and a common chemical (hydrogen peroxide) to break down PET microplastics—the tiny plastic bits shed from water bottles and food packaging that have been found in our blood, organs, and even breast milk. In lab tests, this method broke down over 40% of the plastic in 48 hours, offering a promising, gentler approach to cleaning up microplastic pollution before it ends up in our water and food supply. While this is still early-stage research done in controlled lab conditions, it points toward future technologies that could help reduce the microplastics we're increasingly exposed to in daily life.
Polyethylene terephthalate (PET) microplastics (MPs) exhibit high chemical stability, limiting their degradation under mild environmental conditions. Herein, a visible-light-responsive BiOCl 0.5 I 0.5 solid solution was synthesized and evaluated for the oxidative degradation of PET MPs in an aqueous H 2 O 2 -assisted system. Structural analyses confirmed successful halide substitution and lattice distortion, while UV–Vis diffuse reflectance spectroscopy revealed bandgap narrowing (2.07 eV) relative to BiOCl, extending visible-light absorption. Photoluminescence and electrochemical impedance spectroscopy demonstrated improved charge separation in the mixed-halide system. Mott–Schottky analysis revealed a sufficiently positive valence band potential to drive the oxidation of H 2 O/OH⁻ to •OH radicals. Under visible-light irradiation (425 nm), the combined BiOCl 0.5 I 0.5 /H₂O₂ system achieved a maximum PET mass loss of 41.0% after 48 h at pH 10, outperforming photolysis and single-component controls. ATR-FTIR, TGA, and SEM analyses indicated ester bond cleavage, reduced thermal stability, and pronounced surface erosion consistent with oxidative chain scission. LC–MS detected soluble intermediates including mono(2-hydroxyethyl) terephthalate (MHET) and terephthalic acid derivatives, suggesting progressive depolymerization and oxidation. Taguchi experimental design and ANOVA identified pH as the dominant operational parameter, followed by light intensity, whereas H 2 O 2 concentration showed a comparatively minor effect within the investigated range. The enhanced performance is attributed to the synergistic generation of hydroxyl and superoxide radicals via photocatalytic activation and H 2 O 2 -reduction pathways. This study demonstrates the potential of bismuth oxyhalide solid solutions for photo-assisted PET microplastic degradation and highlights the importance of coupled chemical–photocatalytic conditions in accelerating polymer breakdown.