A convenient strategy for mitigating microplastics in wastewater treatment using natural light and ZnO nanoparticles as photocatalysts: A mechanistic study

Polypropylene microplastics (PPMPs) are one of the major emerging contaminants in the ecosystem due to their frequent usage and improper disposal practices. These PPMPs enter ecosystems via wastewater effluent plants and cause severe environmental health issues. In addition, quantifying PPMPs smaller than 50 μm in wastewater plant extraction is very difficult. Thus, the current study was designed to mitigate the PPMPs using zinc oxide nanoparticles (ZnONPs) as a photocatalyst under sunlight. The photocatalytic reaction was examined using spectroscopic techniques and microscopic imaging. The findings indicated that the weight loss percentage of PPMPs increased, and a decrease in UV-Vis DRS peak intensities was observed. The spectroscopic results elucidated the formation of free radicals, which affect the PPMPs and lead to the formation of carbonyl, allylic, and unsaturated groups. Further, EDS reports clarified that there is increased oxygen content due to the photooxidation process and the disintegration of the polymer chain owing to decreased carbon levels. Overall, ZnO photocatalyst absorbs photons from the visible spectrum of sunlight and forms free radicals, which affect the PPMPs to initiate polymer deterioration. Also, the current study revealed the mechanistic pathway of PPMP degradation under the photocatalytic reaction as proposed in the results obtained above.