Advanced oxidation process as a promising approach for microplastic degradation

Microplastics (MPs) are persistent environmental contaminants whose small size, chemical stability, and heterogeneous composition limit the effectiveness of conventional physical separation and biological treatment methods. Advanced oxidation processes (AOPs) have emerged as promising degradation-based strategies capable of chemically transforming MPs through the generation of highly reactive oxygen species (ROS). This review provides a critical and mechanistic synthesis of recent advances in AOPs-driven MPs degradation, including photocatalysis, Fenton and photo-Fenton systems, electrochemical oxidation, persulfate-based processes, ozone oxidation, and plasma-assisted techniques. Rather than merely listing available technologies, the review systematically compares AOPs based on radical generation pathways, polymer-specific degradation mechanisms, degradation efficiencies, and operational constraints. Key findings reveal that degradation performance is strongly governed by polymer type, crystallinity, aging state, and process conditions, and that no single AOP is universally effective across all the MP classes. Integrated and hybrid AOP configurations-particularly photo-Fenton, photo-electro-Fenton, and persulfate-assisted systems-consistently demonstrate enhanced performance due to synergistic radical production and improved oxidant utilization. The review further identifies critical challenges related to energy demand, catalyst sustainability, scalability, and the formation of secondary transformation products, which may pose additional environmental risks. Overall, this review offers a comparative and mechanistic framework that advances current understanding and supports the rational design of efficient, scalable, and environmentally responsible AOP-based technologies for MPs remediation.