Removal of Perfluorooctanesulfonic Acid in Water by Combining Zerovalent Iron Particles with Common Oxidants

The frequent occurrence of per- and polyfluoroalkyl substances (PFAS) in the water environment is a recent global concern. Because of their extraordinarily strong chemical stability caused by the multiple C-F bonds, decomposition of PFAS by using relatively practical technologies is the most challenging but significant task. In this context, this study focused on evaluating the potential of zerovalent iron (ZVI) particles combined with common oxidants such as hydrogen peroxide, persulfate, and peroxymonosulfate for the removal of perfluorooctanesulfonic acid (PFOS). Oxidant type and dose, temperature, and pH were controlled to generate various oxidizing and reducing reactive species separately or in combination. In most of the cases, a substantial amount of PFOS was removed. However, building up of identifiable expected intermediates and fluoride ions in water was not significant, implying that the observed PFOS removal could be ascribed to presumably its adsorption to and/or complexation with iron (Fe) species such as Fe oxides and dissolved Fe ions originating from ZVI. To confirm the persistence of PFOS, perfluorooctanoic acid (PFOA) with the very similar structure to PFOS was briefly examined. PFOA was well decomposed, producing many expected intermediates such as shorter chain PFAS. The results indicated PFOS, unlike PFOA, seems much more stable even in the presence of the strong reactive species produced by the integrated system.