The Aging Behavior of Polyvinyl Chloride Microplastics by UV/Sodium Percarbonate Oxidation: Efficiency and Mechanism

The aging behavior of microplastics (MPs) in the environment has garnered significant attention, yet the exact aging process undergone by microplastics during advanced oxidation still remains unclear. This study emphasized elucidating the oxidation and dechlorination mechanisms of polyvinyl chloride microplastics (PVC MPs) within the UV-activated sodium percarbonate system (UV/SPC). After 35 h of UV/SPC (0.05 M) treatment, it exhibited effective dechlorination with a Cl− release of 100.62 ± 13.17 mg/L. And this treatment resulted in the fragmentation and release of fragments from the PVC MPs, thereby contributing to their further aging and dechlorination. In addition, an increase in oxygen-containing functional groups was identified. Quenching experiments confirm that ·OH and ·CO3− are the primary active species present in the system. In summary, the aging of PVC MPs results in a process of fragmentation, releasing fragments that are more fragile and susceptible to mineralization compared to the original PVC MPs. The release of chloride ions originates from the mineralization of these fragments released from PVC MPs by ·OH and ·CO3−. This study has provided valuable insights into the aging mechanisms of MPs in practical wastewater treatment.