Photodegradation of Perfluorooctanesulfonic Acid on Fe-Zeolites in Water

Abstract

Perfluorooctanesulfonic acid (PFOS) decomposition in an aqueous environment remains a huge challenge because of its extreme chemical and biological inertness even when compared with other per- and polyfluoroalkyl substances (PFAS). In this work, we demonstrate for the first time a successful photochemical PFOS degradation by irradiation with 254 nm ultraviolet (UV) light after adsorption on μm-sized Fe(III)-loaded zeolites under ambient conditions with oxygen (O₂) as the terminal oxidant. Twenty μM PFOS loaded on 0.5 g L^-1 Fe-zeolites in aqueous suspension was degraded up to 99% within 96 h under acidic conditions (pH ≤ 5.5) in the presence of oxygen. Besides fluoride and sulfate, short-chain perfluorinated carboxylic acids (PFCAs) were identified and quantified as products. In addition, the effects of initial pH, catalyst dosages, and operation temperature on the degradation of PFOS were investigated. We also successfully applied the system to real groundwater samples where trace PFOS was present. Our results indicate that PFOS degradation is initiated by electron transfer from sulfonate to iron. The presented experimental study offers an option for a novel water remediation technology, comprising first a zeolite-based adsorption step followed by a step for photochemical regeneration of the adsorbent.