Effect of granular activated carbon and other porous materials on thermal decomposition of per- and polyfluoroalkyl substances: Mechanisms and implications for water purification

Thermal treatment is routinely used to reactivate the spent granular activated carbon (GAC) from water purification facilities. It also an integral part of sewage sludge and municipal solid waste management. This study presents a detailed investigation fate per- polyfluoroalkyl substances (PFAS) one PFAS alternative (GenX) in thermal processes, focusing on effect GAC. We demonstrate that thermolysis perfluoroalkyl carboxylic acids (PFCAs), including perfluorooctanoic acid (PFOA), GenX can occur at temperatures 150?200 °C. Three temperature zones were discovered for PFOA, stable nonvolatile zone (?90 °C), phase-transfer decomposition (90?400 fast (?400 °C). The began with homolysis C?C bond next carboxyl group PFCAs, which formed unstable radicals. Dual pathways seem exist. addition highly porous adsorbent, such as GAC or copolymer resin, compressed intermediate sublimation changed their pathways, increased rate constant by up 150-fold 250 results indicate observed acceleration was linked adsorption gas-phase PFCA molecules presence non-activated charcoals/biochars low affinity PFOA did not accelerate its decomposition, suggesting ? electron-rich, polyaromatic surface charcoal/GAC played insignificant role compared adsorbent's porosity. Overall, (1) substantial PFCAs during conventional GAC/sludge/waste very likely, (2) other materials alter pathways.