Valorization of PET Plastic as an Active and Stable Ozonation Catalyst via Carbonization and FeMn Loading

Polyethylene terephthalate (PET) waste is an abundant carbon-rich feedstock, yet its conversion into ozonation catalysts remains insufficiently explored. In this study, PET waste was carbonized and loaded with Fe and Mn to prepare a carbon catalyst (FeMn-PET) for catalytic ozonation of recalcitrant contaminants in wastewater. At a catalyst dosage of 100 mg/L and a total Fe/Mn loading of 3.8 wt %, FeMn-PET increased the second-order kinetic constant for benzotriazole degradation to 781.9 M–1 s–1 at pH 2, 19-fold that of ozonation alone. The catalytic activity increased with total Fe/Mn loading and catalyst dosage, and FeMn-PET maintained high activity in the presence of 10 mM inorganic anions and performed well in real secondary effluent. Five-cycle reusability tests confirmed its good stability, with Fe and Mn leaching of only 30 μg/L and 1.2 μg/L, respectively. FeMn-PET promoted the generation of hydroxyl radicals (•OH), superoxide radicals (•O2–), and singlet oxygen (1O2) with pH-dependent oxidation pathways. The estimated production cost of PET-derived activated carbon was 2.81 $/kg, suggesting waste PET as a cost-competitive catalyst precursor for FeMn-loaded carbon catalysts in ozonation-based wastewater treatment.