Photocatalytic Remediation of Polyethylene Terephthalate (PET) Micro- and Nanoplastics using Ellipsoidal α-Fe₂O₃

Microplastics (MPs, <5 mm) and nanoplastics (NPs, <1 μm) generated from plastic waste are emerging as a global environmental and health-related challenge affecting life in water and soil. Among the commodity plastics, polyethylene terephthalate (PET) - extensively used in single-use bottles and textiles - exhibits hydrolytic stability and mechanical resilience, making it more resistant to natural degradation but extremely problematic for long-term persistence as MPs and NPs. In this study, photocatalytic degradation of PET MPs and NPs is investigated using hematite nano-ellipsoids (~ 250 nm major axis and ~ 50 nm minor axis) as the photocatalyst under visible light illumination. For this study, commercial PET granules are converted into NPs (~100 nm) via flash nanoprecipitation (FNP). The extent and efficiency of PET degradation is systematically evaluated using PET NPs of 100 nm under visible light irradiation at neutral pH, which exhibited mean 42±0.4% mass loss over 8 hours, with a reduction in particle size from 100 nm to ~10 nm. PET MPs (~100 μm) photocatalytic degradation exhibited 32±0.4% of weight loss and an overall particle size reduction from 100 μm to 0.8 μm after 8 days. The photocatalytic degradation of PET due to reactive oxygen species is found to be faster for NPs compared to MPs due to the higher specific surface area of NPs. These results establish HNEs as a highly effective and environmentally benign photocatalyst for accelerating PET micro- and nanoplastic degradation, offering a low-complexity and scalable platform for advanced plastic remediation applications.