Environmental Aging Enhances Hydrodynamic Driven Microplastics Piezoelectric Catalytic Decomposition of Organic Pollutants.

Microplastics (MPs) are recognized as emerging environmental pollutants. However, their potential role in degrading pollutants under hydrodynamic conditions after environmental aging is frequently overlooked. In this study, three common MPs including polyethylene (PE), polypropylene (PP), and polystyrene (PS) were investigated for their ability to enhance atrazine (ATZ) degradation after UV aging and under ultrasonic hydrodynamic treatment. Our findings demonstrate that environmental aging significantly boosts the piezoelectric catalytic activity of MPs, consequently accelerating pollutant degradation. UV-aged polypropylene (PP-8) exhibited the highest performance, achieving a piezoelectric catalytic degradation rate constant (k ═ 0.246 min-1), which is 22.36-fold higher than that of pristine PP (k ═ 0.011 min-1). Mechanistic studies revealed that polar carbonyl (C ═ O) functional groups formed during aging play a pivotal role for improving the piezoelectric properties of MPs. This enhancement promotes hydroxyl radicals (·OH) generation from water molecules, which drives pollutant degradation. Furthermore, this effect was found to be general as it was consistently observed in systems using MPs aged by different environmental processes (high temperature, mechanical wear, and Fenton oxidation) and exposed to various hydrodynamic conditions (oscillation and cavitation). This study provides new insights into the self-purification mechanisms of organic pollutants in natural environments.