Per- and polyfluoroalkyl substance emission from waste thermal treatment: A review

The objective of this study is to examine the content of per- and polyfluoroalkyl substance (PFAS) in the emissions from waste containing PFAS thermal treatment. The study is reviewed according to PRISMA 2020. Scopus, Web of Science and PubMed are the databases used. The publishing period is from 2020 to 7 August 2024; only studies written in English language are included; studies reporting on analysis of PFAS in the inlet, outlet streams and removal efficiency; combustion, oxidation, hydrothermal carbonization, pyrolysis and gasification processes; waste from full-scale facilities are considered. Two of three researchers screened the studies for eligibility. One researcher extracted the data and the other two reviewed them for accuracy. Data were then organized based on the statistical information reported in each included study. A total of 14 studies were included. From equation $\sum _{i=1}^n{\mathrm{PFAS}}_i$, mean concentration of each PFAS_i in the inlet waste ranged from 9.3 ng g^-1 DM to 203.9 ng g^-1 DM. PFPeA, perfluoro octane sulfonate (PFOS) and PFHxA compounds were compared with those of higher concentration in inlet waste ranging from 30 ng g^-1 wb, for PFOS, to about 400 ng g^-1 wb, for PFPeA. Removal efficiency was calculated as a mass balance among inlet and outlet of investigated PFAS, ranged from 30% to 100%. Maximum removal efficiencies were detected for process temperatures ⩾550°C and retention time ⩾2 seconds. Thermal treatment of PFAS containing waste achieves high level of PFAS removal when operated at high temperatures and proper gas residence time. More research is needed for better assessing the effective mineralization of PFAS in the outlet stream and the presence and fate of potential reactive compounds due to incomplete combustion.