Technology for PFAS Adsorption and Degradation

Abstract

In recent years, concerns have emerged regarding the diffusion of perfluorinated and polyfluorinated alkyl substances （PFASs） into the environment; moreover, PFOS, PFOA, and PFHxS have been widely detected in several rivers and the groundwater in Japan. We investigated adsorption treatment using powdered activated carbon （PAC） as an inexpensive and easy-to-use removal technology for diffused PFASs in rivers and groundwater. Adsorption tests on actual river water showed that PFASs with relatively long carbon chains, such as PFOS, were easily removed from the water via adsorption. Moreover, the amount of adsorbed PFASs containing short carbon chains was found to increase when the pH was adjusted to the acidic range. Furthermore, we found that after the adsorption of PFASs on PAC, the latter must be appropriately and reliably decomposed. Hence, we considered using high-temperature superheated steam, which can maintain a high-temperature range of 1,100 ℃ or higher. We developed a new test apparatus for high-temperature superheated steam decomposition via hydrogen combustion rather than fossil fuel combustion to reduce CO₂ emissions. We demonstrated PFAS decomposition using PAC slurry with adsorbed PFOS and other substances. This paper details these efforts.