Mineralization of captured perfluorooctanoic acid and perfluorooctane sulfonic acid at zero net cost using flash Joule heating

Abstract

Per- and polyfluorinated alkyl substances (PFAS), including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), are persistent environmental contaminants that have infiltrated freshwater systems. Granular activated carbon (GAC) is widely used for PFAS removal but becomes secondary waste (PFAS-GAC). Current treatment methods are energy intensive and release hazardous fluorocarbons. This study demonstrates electrothermal mineralization of PFOA and PFOS-GAC via flash Joule heating, a scalable and efficient process. Heating PFAS-GAC with sodium or calcium salts converts PFAS into inert fluoride salts with >90% fluorine conversion and >99% PFOA and PFOS removal. Simultaneously, the spent carbon is upcycled into flash graphene, offsetting treatment costs by US$60–100 per kg. This solvent- and catalyst-free method substantially reduces energy use, greenhouse gas emissions and secondary waste. A techno-economic assessment highlights its scalability and environmental benefits, offering a rapid (~1 s), cost-effective solution for PFAS remediation and upcycling of waste carbon into high-value products. Activated carbon has been widely used for PFAS adsorption, but this method generates secondary solid wastes. The flash Joule heating approach realizes mineralization of PFAS and generation of useful flash graphene in waste granular activated carbon.