Magnetite-assisted hydrothermal upgrading of polyvinyl chloride into an efficient heterogeneous Fenton catalyst

Dechlorination and valorization of waste polyvinyl chloride (PVC) are vital for environmental sustainability, but conventional hydrothermal methods struggle to simultaneously achieve efficient dechlorination and the production of value-added products. Herein, we exploit the dual reactivity of magnetite to concurrently drive dechlorination and carbonization, enabling one-step hydrothermal conversion of PVC into a heterogeneous Fenton catalyst. As an electron donor and provider of solid acid sites, magnetite can synergistically promote the cleavage of C-Cl bonds in PVC during hydrothermal processes through both reductive dechlorination and catalytic hydrolysis pathways, with a high dechlorination efficiency of 96.2∼98.9%. Moreover, affected by these two enhanced dechlorination pathways, PVC-derived hydrochar exhibits a higher graphitization degree and a larger oxygen-containing functional group content than the control (without magnetite). Besides, magnetite inhibits PVC melting agglomeration to reduce particle size, and facilitates the carbonization of organic intermediates, thereby increasing the carbon yield of hydrochar from 74.7% to 97.3%. The resulting composite exhibited efficient heterogeneous Fenton catalytic activity for Bisphenol A degradation, particularly achieving a 97% degradation efficiency within 30 min when natural magnetite was employed. This research could provide valuable insights into the chemical recycling of chlorinated plastics, helping to reduce environmental pollution and promote the efficient utilization of products.