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Modified TiO2 and ZnO photocatalysts for microplastic degradation: mechanisms, challenges, and recent advances
Summary
This review examines recent advances in using modified titanium dioxide and zinc oxide photocatalysts to degrade microplastics in the environment. Researchers summarized the mechanisms by which these catalysts break down plastic particles when activated by light, as well as the challenges that remain for practical application. The study suggests that photocatalytic degradation is a promising approach for addressing microplastic pollution, though significant technical hurdles still need to be overcome.
Microplastics have emerged as persistent environmental pollutants, ubiquitously present in aquatic and terrestrial ecosystems. Their minute size facilitates entry into food webs, where they disrupt physiological functions and trigger oxidative stress and inflammatory responses in living organisms. Furthermore, microplastics act as vectors for toxic chemicals and pathogenic microorganisms, intensifying their ecological and health-related hazards. Due to their stable and highly polymerized structure, natural degradation of these materials remains extremely limited. Photocatalysis has gained considerable attention as a sustainable and eco-friendly approach for the degradation of microplastics. This review comprehensively summarizes research progress from 2015 to 2025, focusing on photocatalytic mechanisms, degradation pathways, and efficiency trends, particularly for polyethylene, polypropylene, and polystyrene. Among various photocatalysts, titanium dioxide (TiO) and zinc oxide (ZnO) have been most extensively investigated owing to their stability, strong oxidizing potential, and photochemical activity. Under ultraviolet irradiation, these semiconductors generate reactive oxygen species (ROS), including superoxide anions (·O⁻) and hydroxyl radicals (·OH), which initiate oxidative scission of polymer chains, ultimately leading to mineralization into CO and HO. Recent advances have concentrated on improving photocatalytic performance through structural and compositional modifications aimed at enhancing visible-light absorption, reducing electron-hole recombination, and increasing surface reactivity. This review provides a detailed overview of these advancements and offers a comparative evaluation of modified TiO and ZnO photocatalysts, emphasizing their potential for efficient and sustainable mitigation of microplastic pollution.