Catalytic transformation of microplastics to functional carbon for catalytic peroxymonosulfate activation: Conversion mechanism and defect of scavenging

Plastic wastes were catalytically transformed into different structured carbons as effective catalysts for peroxymonosulfate activation to degrade organic pollutants in water and the catalytic conversion mechanism was comprehensively investigated. A salt template-based carbonization approach was successfully developed to catalytically converting high-density polyethylene (HDPE) into diverse carbon materials, such as core-shell carbon composites, nanosheets, and their hybrids. The morphology and proportions of structure defective carbon were found to be controlled by a NiCl₂ to HDPE ratio. Carbon nanosheets performed excellent catalytic efficiency in peroxymonosulfate activation toward phenol oxidation, due to a high content of reactive defects via a nonradical electron-transfer mechanism. More importantly, deliberate experiment design and kinetic analyses were employed to illustrate the artifact of radical scavengers (e.g., ethanol) in mechanistic investigation for nonradical/radical reaction. This work provides an upcycle approach for waste plastics into carbocatalysts and new insight to the conversion process and advanced water purification.