(354c) Plasma-Assisted Degradation of Perfluorobutane Sulfonate (PFBS)

This study investigates plasma-assisted degradation of perfluorobutane sulfonate (PFBS), a compound very few advanced oxidative and reductive technologies are able to degrade. PFBS, a member of a group of per- and polyfluoroalkyl substances (PFAS), is used as a replacement of perfluorooctane sulfonate (PFOS) in many consumer products such as nonstick pans, wire coating and firefighting foams. Recent studies have shown that PFBS is as persistent in the environment and bio-accumulative in people as its long-chain counterparts and human exposure to it can lead to serious health effects such as cancer, liver damage and immune system and thyroid changes. Here, the degradation of 10 mg/L of PFBS was investigated using a point-ring plasma reacor electrode configuration in which plasma is formed in argon gas and is contacting the surface of water containing dissolved PFBS. Experiments were conducted with and without cetyltrimethylammonium bromide (CTAB), a surfactant, whose purpose was to interact with and concentrate PFBS at the plasma-liquid interface, the region of chemical reactivity. No removal of PFBS was observed without the surfactant. With CTAB, ~99% of PFBS was removed from the bulk liquid and concentrated at the interface. At the interface, 67% of the 99% concentrate was degraded which resulted in 43% defluorination and 42% desulfonation. The dosage of the surfactant also played a role in the degradation. With step-wise CTAB dosing, defluorination rate increased markedly from 43% to 67%, and sulfate production from 42% to 68%. Experiments conducted with different surfactant types revealed that only cationic surfactants such as CTAB affect PFBS degradation, mainly through electrostatic attraction. Electrical discharge plasma appears to be a viable technology for the degradation of non-surfactants, in particular short-chain PFAS.