Degradation of Microplastics by a Thermal Fenton Reaction

Microplastics (MPs) are ubiquitous in the environment and are infiltrating the food chain, causing potential risks to living beings. However, current methods of MP removal from an aqueous environment are limited by low efficiency. Advanced oxidation processes (AOPs) are emerging techniques for MP purification. Herein, a hydrothermal coupled Fenton system is developed for decomposition of ultrahigh-molecular-weight polyethylene, achieving 95.9% weight loss in 16 h and 75.6% mineralization efficiency in 12 h. The high effectiveness is attributed to the synergy of hydrothermal hydrolysis, proton-rich environment, and massive production of hydroxyl radicals. The system is also efficient to remediate different petroleum-based plastics and maintains high efficiency in practical water bodies. Characterizations revealed a two-stage degradation process: chain unfolding/stretching and oxidation, giving rise to the formation of carbonyl groups and decreased crystallinity of MPs during the hydrothermal treatment. The chain stretching stage is pivotal to the whole treatment because it remarkably facilitates subsequent chain cleavage and Fenton oxidation. This study provides a new approach to removing MPs in water bodies and new insights into MP degradation by the AOP technology.