Removal of long- and short-chain PFAS from groundwater by foam fractionation

Abstract

Due to the tendency for per- and polyfluoroalkyl substances (PFAS) to accumulate at the air–water interface, foam fractionation has gained attention as a cost-effective approach to treat PFAS-impacted water. Although foam fractionation is effective for long-chain length PFAS, short-chain PFAS are less surface active and can remain in solution even after extended treatment times. The objective of this study was to evaluate the ability of six cationic surfactants to remove both long- and short-chain length PFAS from groundwater by foam fractionation. Cetyltrimethylammonium bromide (CTAB) accumulated the most at the air–water interface and was subsequently evaluated in a foam fractionation system over a 4 order of magnitude range of PFAS concentrations, as well as 4 different CTAB mass delivery rates. For two natural groundwaters impacted by aqueous film forming foam (AFFF), total PFAS concentrations were reduced from ∼15 000 ng L⁻¹ to less than the detection limit of 8 ng L⁻¹ in as short as 15 minutes. These findings demonstrate that the addition of CTAB, which exhibits a strong affinity for the air–water interface, to foam fractionation systems achieves rapid removal of both long- and short-chain PFAS from synthetic and natural groundwaters.