Emerging Approaches for Dechlorination of Plastic Waste Prior to Thermochemical Recycling: A Comprehensive Review

The increasing generation of plastic waste has intensified the search for sustainable recycling technologies capable of recovering valuable resources while minimizing environmental impacts. Among emerging solutions, thermochemical recycling processes such as pyrolysis, gasification, and hydrothermal liquefaction have gained significant attention. However, the presence of chlorine-containing polymers, particularly poly(vinyl chloride) (PVC), represents a major challenge due to the release of hydrogen chloride (HCl), catalyst deactivation, equipment corrosion, and contamination of valuable products. Consequently, effective dechlorination pretreatments are essential for improving process performance and product quality. This review provides a comprehensive overview of current pretreatment technologies for chlorine management in plastic solid waste. Mechanical sorting, density-based separation, chemical extraction, alkaline treatments, hydrothermal processing, thermal dehydrochlorination, catalytic methods, and emerging photocatalytic approaches are critically analyzed and compared. The mechanisms, operating conditions, chlorine removal efficiencies, technological readiness levels, and industrial applicability of each method are discussed. Moreover, particular attention will be devoted to integrating different pretreatment technologies to achieve an overall enhanced chlorine removal efficiency before thermochemical technologies. Finally, reported techno-economic, environmental, and safety indicators are compared where quantitative data are available, while the principal data gaps and technological barriers to large-scale implementation are identified.