Inhibiting the release of polyvinyl chloride nanoplastics via superoxide ion-induced self-flocculation during polyvinyl chloride microplastics degradation

Microplastics (MPs) and nanoplastics (NPs) have attracted widespread attention due to their detrimental effects on the ecosystem and human health. NPs, which are smaller and more harmful than MPs, are generated during the degradation of MPs. The present study aimed to inhibit the release of polyvinylchloride NPs (PVC-NPs) generated during the degradation of PCV-MPs, by using Ultraviolet/ sulphite (UV/SO₃^2-) in the presence of O₂ (UV/SO₃^2-/O₂). Under optimal conditions, the dechlorination rate and weight loss of PVC-MP were 72.4% and 61.7%, respectively. The chemical changes of the treated PVC-MPs and the intermediates during the degradation of PVC-MPs were investigated. It was confirmed that PVC-NPs form during the degradation PVC-MPs. In addition, PVC-NPs were successfully removed from the water by superoxide ion (O₂^-)-induced self-flocculation, resulting in a reduced release of PVC-NPs into the water. The weight of the self-flocculation containing PVC-NPs was 5.2 mg. Self-flocculation was investigated by scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Numerous C-O-C groups were identified in the self-flocculation. The results indicate a potential process for the removal of PVC-NPs by self-flocculation. This study introduces a new method of degradation of PVC-MPs while simultaneously reducing the release of PVC-NPs.