Degradation of polyvinyl chloride microplastics via electrochemical oxidation with a CeO2-PbO2 anode

As an emerging organic pollutant, microplastics (MPs) pose a serious threat to the water environment and human health. Effective water treatment processes are urgently needed to remove MPs from the aquatic environment. Herein, an electrocatalytic oxidation system with a CeO2-modified PbO2 anode (marked as CeO2-PbO2) was proposed for the degradation of polyvinyl chloride microplastics (PVC-MPs). When the CeO2 concentration in the electrodeposition solution was 0.005 M, the obtained CeO2-PbO2 electrode had the best electrocatalytic activity due to its denser structure, higher oxygen evolution potential, and more active sites. After 6 h of electrolysis, the weight loss of PVC-MPs at the CeO2-PbO2-0.005 anode was 38.67%, greatly higher than 16.67% at the pristine PbO2 anode. To explore the degradation mechanism of PVC-MPs, the surface morphologies, elemental states, and functional groups of PVC-MPs were compared before and after electrochemical treatment, and the formed intermediates were identified. Experimental results revealed that the PVC backbones were broken, the C--C double bonds were oxidized or oxidatively cleaved into small molecules, and the dechlorination reaction occurred in the electrochemical oxidation process. As a result, the particle size of the PVC-MPs decreased significantly, lots of cracks appeared and many small pieces were formed on the surface of the PVC-MPs.