Efficient degradation and mineralization of polyethylene terephthalate microplastics by the synergy of sulfate and hydroxyl radicals in a heterogeneous electro-Fenton-activated persulfate oxidation system.

The presence of polyethylene terephthalate (PET) microplastics (MPs) in waters has posed considerable threats to the environment and humans. In this work, a heterogeneous electro-Fenton-activated persulfate oxidation system with the FeS-modified carbon felt as the cathode (abbreviated as EF-SR) was proposed for the efficient degradation of PET MPs. The results showed that i) the EF-SR system removed 91.3 ± 0.9 % of 100 mg/L PET after 12 h at the expense of trace loss (< 0.07 %) of [Fe] and that ii) dissolved organics and nanoplastics were first formed and accumulated and then quickly consumed in the EF-SR system. In addition to the destruction of the surface morphology, considerable changes in the surface structure of PET were noted after EF-SR treatment. On top of the emergence of the O-H bond, the ratio of C-O/C=O to C-C increased from 0.25 to 0.35, proving the rupture of the backbone of PET and the formation of oxygen-containing groups on the PET surface. With the verified involvement and contributions of SO and OH three possible paths were proposed to describe the degradation of PET towards complete mineralization through chain cleavage and oxidation in the EF-SR system.