Adsorption of PFOS onto graphite intercalated compound and analysis of degradation by-products during...

Perfluorooctane sulfonate (PFOS) is a highly recalcitrant perfluoro chemical belonging to the family of per- and polyfluoroalkyl substances (PFAS). Its adsorption and degradation was demonstrated in a novel PFAS remediation process involving the adsorption onto graphite intercalated compounds (GIC) and the electrochemical oxidation. The Langmuir type of adsorption was characterized by a loading capacity of 53.9 μg PFOS g^-1 GIC and a second order kinetics (0.021 g μg^-1 min^-1). Up to 99% of PFOS was degraded in the process with a half-life of 15 min. The breakdown by-products included short chain perfluoroalkane sulfonates such as Perfluoroheptanesulfonate (PFHpS), Perfluorohexanesulfonate (PFHxS), Perfluoropentanesulfonate (PFPeS) and Perfluorobutanesulfonate (PFBS), but also short chain perfluoro carboxylic acids such as perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA) and perfluorobutanoic acid (PFBA) indicating different degradation pathways. These by-products could also be broken down but the shorter the chain the slower the degradation rate. This novel combined adsorption and electrochemical process offers an alternative treatment for PFAS contaminated waters.