Polyvinyl chloride recycling and Plastic Waste Management: Addressing the PVC Challenge through Innovative Dechlorination Technologies

Polyvinyl chloride (PVC) is the third most widely used thermoplastic globally, with production capacity exceeding 50 million tons in 2023 and a compound annual growth rate exceeding 5% projected through 2028. However, PVC's high chlorine content—approximately 57% of its total mass—poses a significant threat to the environment and human health. Currently, 36% of waste PVC is landfilled and 9.3% is incinerated, with the remainder managed through various recycling approaches. The urgent need for efficient and clean recycling technologies has driven significant research into advanced strategies for the upgrading and reuse of PVC waste plastics.

Plastic waste management strategies for PVC are categorized into primary (closed-loop), secondary (mechanical), and tertiary (chemical) processes. Closed-loop recycling involves reprocessing waste plastics to retain useful properties, but can lead to plasticizer loss and partial degradation, resulting in decreased performance of recycled products. Mechanical recycling, which converts waste plastics into reproducible products through separation, sorting, cleaning, crushing, and compound granulation, has shown some promise in enhancing certain mechanical properties. However, the instability of PVC's chemical structure and the risk of releasing harmful substances have not been fundamentally addressed through mechanical methods alone.

Polyvinyl chloride recycling faces unique challenges due to the presence of various additives used during PVC preparation to ensure stability and strength. During chemical recycling, the high chlorine content may lead to the formation of toxic chlorides such as dioxins and polychlorinated biphenyls, cause equipment corrosion, result in environmental pollution, and reduce the value of target products. These challenges have driven the development of thermochemical pretreatment dechlorination methods as a mainstream approach to mitigate environmental issues and facilitate conversion of waste plastics into valuable energy and chemical products.

Thermal dechlorination methods include pyrolysis, hydrothermal, and solvent dechlorination processes. Pyrolytic dechlorination typically involves two stages: pretreatment dechlorination followed by further degradation of polyenes. Hydrothermal dechlorination removes chlorine from PVC under subcritical or supercritical water conditions, converting it into inorganic chlorine. Solvothermal dechlorination utilizes specific solvents at relatively low reaction temperatures below 200°C, enabling sustainable PVC upgrading while promoting pre-crosslinking of the precursor. These pre-treatment dechlorination strategies can effectively dechlorinate and recycle PVC, with significant advantages demonstrated by cutting-edge technologies such as staged catalytic pyrolysis, catalytic co-hydrothermal treatment, and ionic liquids.

Plastic waste management for PVC lies in comprehensive approaches that address both the dechlorination process and the upgraded utilization of dechlorinated PVC (DPVC) and chlorine elements (Cl). Research highlights the potential of waste Cl recirculation for the closed-loop utilization of chlorine resources. DPVC can be further processed into solid, liquid, and gaseous fuels, providing sustainable alternatives in the energy sector, and demonstrates unique application value in environmental management and materials science due to its multifunctional carbon material properties. As global PVC production continues to grow, these innovative recycling technologies will play an increasingly critical role in achieving circular economy goals for plastics.

Polyvinyl chloride recycling represents a critical pathway toward reducing the environmental burden of PVC waste while recovering valuable materials. The development of advanced dechlorination technologies, integration of digital process control, and policy support for recycling infrastructure will drive continued progress in this essential sector. As industries and governments increasingly prioritize circular economy principles, effective PVC recycling will remain a cornerstone of sustainable plastic waste management strategies, ensuring that valuable polymer resources are recovered and reintegrated into manufacturing supply chains.