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 CC 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.