Critical Review of Thermal Decomposition of Per- andPolyfluoroalkyl Substances: Mechanisms and Implications forThermal Treatment Processes

Per- and polyfluoroalkyl substances (PFASs) arefluorinated organic chemicals that are concerning due to theirenvironmental persistence and adverse human and ecological effects.Remediation of environmental PFAS contamination and their presencein consumer products have led to the production of solid and liquidwaste streams containing high concentrations of PFASs, which requireefficient and cost-effective treatment solutions. PFASs are challenging todefluorinate by conventional and advanced destructive treatmentprocesses, and physical separation processes produce waste streams(e.g., membrane concentrate, spent activated carbon) requiring furtherpost-treatment. Incineration and other thermal treatment processes arewidely available, but their use in managing PFAS-containing wastesremains poorly understood. Under specific operating conditions, thermal treatment is expected to mineralize PFASs, but thedegradation mechanisms and pathways are unknown. In this review, we critically evaluate the thermal decomposition mechanisms,pathways, and byproducts of PFASs that are crucial to the design and operation of thermal treatment processes. We highlight theanalytical capabilities and challenges and identify research gaps which limit the current understanding of safely applying thermaltreatment to destroy PFASs as a viable end-of-life treatment process.

Automated summary

Per- and polyfluoroalkyl substances (PFASs) are a type of fluorinated organic chemicals that pose environmental and human health risks. Efficient and cost-effective treatment solutions are needed for remediation of PFAS contamination and waste streams with high concentrations of PFASs. Conventional and physical separation processes are not effective in defluorinating PFASs, and the degradation mechanisms and pathways of thermal treatment processes remain unclear. This review critically evaluates the thermal decomposition mechanisms, pathways, and byproducts of PFASs to improve the understanding and application of thermal treatment as an end-of-life process for PFAS destruction.