Hydrothermal Fenton-like process for dehydrochlorination and recovering of PVC pipe microplastics in aquatic systems

The widespread use of polyvinyl chloride (PVC) pipes in plumbing and drainage systems constitutes a major source of microplastic (MPs) pollution in aquatic environments. Both discarded pipes and the derived PVC_MPs present serious environmental and health risks. To be addressed, this study presents a Fenton-like strategy using 1.0wt%H₂O₂ with Fe(OH)₃ under subcritical water (250°C, ∼3.0MPa), achieving near-complete dehydrochlorination (>99.0% efficiency) of PVC_MPs. The generated solid carbonaceous products retained most of carbon from PVC_MPs (89.27± 0.26 %), demonstrating their great potential for valuable conversion into graphene. Liquid phase product was primarily consisted of Fe²⁺/Fe³⁺ and monocyclic aromatics (e.g.benzaldehyde and acetophenone). Mechanistic investigations revealed that Fe(OH)₃ initially served as an interfacial catalyst and adsorbent, facilitating critical bonds cleavage. Subsequent release of HCl promotes the dissolution of Fe³⁺ ions, activating Fenton-like reactions to generate abundant reactive oxygen species (ROS), primarily HO·, HO₂· and ¹O₂. These ROS radicals drive dehydrochlorination via β-scission, where the attack on C-H bonds generates alkyl radicals (R·) as key intermediates to proceed subsequent dehydrochlorination, oxygenation, and dehydrogenative aromatization. The resulting C=C bonds by dehydrochlorination enabled further cyclization and dehydroaromatization. This proposed mechanism is strongly supported by molecular dynamics simulations and density functional theory calculations. Techno-economic analysis demonstrated a remarkable net revenues of 4331.86 USD per ton of PVC pipes through the graphene recovering pathway. Therefore, this Fenton-like strategy not only help mitigate PVC (micro)plastic pollution in aquatic systems but also offers an economically attractive pathway for (micro)plastic wastes managements in future.