Breaking the “Forever Chemical” Cycle: A Critical Review of Per- and Polyfluoroalkyl Substances in Solid Waste Sources and Their Fate During Thermal Treatment

The persistence of per- and polyfluoroalkyl substances (PFASs) poses a significant challenge in solid waste management. This paper systematically reviews the distribution characteristics of PFASs in various solid waste streams, including industrial sludge, food packaging, textiles, and electronic waste. It also evaluates the removal efficiency of four thermal treatment technologies—incineration, pyrolysis, smoldering combustion, and hydrothermal liquefaction (HTL)—for PFASs in solid waste. Although incineration and smoldering combustion can achieve destruction and removal efficiencies exceeding 99.99%, the release of short-chain byproducts remains a critical bottleneck. Pyrolysis effectively decontaminates solid-phase products but carries the risk of phase transfer into pyrolysis oils. The efficiency of HTL is highly dependent on process parameters. PFAS degradation is a radical-mediated process initiated by the dissociation of functional groups. We emphasize that substrate surface properties and the presence of counterions play pivotal roles in modulating these reaction pathways. The introduction of water vapor (as a hydrogen-rich medium), alkaline additives, or specific catalysts is considered a promising strategy to inhibit the recombination of reactive byproducts and enhance mineralization rates.