Mineralization characteristics and behavior of polyethylene microplastics through ozone-based treatment

The elimination of microplastics (MPs) has become an urgent issue due to their large quantities and imperfect treatment technologies. In this work, polyethylene (PE), which is ubiquitous in the environment, was selected to study its removal by ozone-based treatment. Catalysts including α-MnO₂ and α-FeOOH were synthesized for catalytic ozonation to improve efficiency. The study focused on simulating the conversion of CO₂ in the off-gas via the detection of inorganic carbon produced. The morphology and structure of the remaining PE MPs were characterized using scanning electron microscope and Fourier-transform infrared spectroscopy-attenuated total reflection. Our results confirmed that fragmentation and oxidation occurred in the remaining PE MPs, which enhanced the adsorption capacity of ofloxacin (OF). Besides, the 20 mM α-FeOOH could better improve the mineralization efficiency by 3.27 folds with more production of •OH (1.09*10^-12 M). Moreover, possible products identified by liquid chromatography-time-of-flight mass spectrometer confirmed the decomposition of main chains of MPs into low-molecular-weight organic compounds with functional groups such as C-OH, C-O-C, and CO. The finding that photoaged PE MPs could be efficiently mineralized under the attack of O₃/•OH provides a solid foundation for the removal of natural MPs in the environment.