Ultrasound-assisted electrocatalytic degradation of microplastics by a hydrophobic Ce3Mn7-PbO2 anode: Enhanced performance and degradation mechanism

Microplastics (MPs), as emerging organic pollutants, pose significant threats to water environment safety and human health. In this study, a highly hydrophobic Ce₃Mn₇-PbO₂ (HH-Ce₃Mn₇-PbO₂) anode was developed and applied in ultrasound-assisted electrochemical oxidation (UEO) system for the degradation of MPs. The incorporation of Ce₃Mn₇ and enhanced hydrophobicity improved the stability of the PbO₂ anode and facilitated the generation of hydroxyl radicals (•OH). The introduction of ultrasound led to the formation of hot spots, which not only enhanced chemical reaction and mass transfer but also increased the production of reactive oxygen species (ROS). Consequently, during the degradation of polyvinyl chloride microplastics (PVC-MPs), the UEO system with the HH-Ce₃Mn₇-PbO₂ anode achieved significantly higher degradation efficiency of 71.5 %, compared to 24.7 % observed in conventional electrochemical oxidation (EO) system using a pure PbO₂ anode. Electron spin resonance (ESR) tests and reactive species quenching experiments revealed that the •OH was the primary reactive species, contributing 67.4 % to the degradation process. In contrast, the contributions of sulfate radical (SO₄^•−), superoxide radical (O₂^•−), and singlet oxygen (¹O₂) were relatively minor, at 7.3 %, 15.3 %, and 10.0 %, respectively. These findings provide a scientific foundation and theoretical insights for the efficient degradation of MPs through the UEO process.