Process to separate per- and polyfluoroalkyl substances from water using colloidal gas aphrons

Current ex situ per- and polyfluoroalkyl substances (PFAS) remediation strategies often involve the treatment of large volumes of PFAS-impacted water via separation processes to concentrate PFAS for subsequent treatment or disposal. This study presents a new method for concentrating PFAS that relies on colloidal gas aphrons (CGAs), unusual microstructures composed of water, multilayers of surfactants, and air, that can be used for separation via electrostatic and hydrophobic sorption. This study successfully demonstrates the efficacy of CGAs in removing ionic dyes (as PFAS surrogates) (81%-91%), as well as ultra-short and short-chain PFAS (60%-90%) and perfluorooctanoate (PFOA,88%) within 10 min. However, poor removal of perfluorooctanesulfonate (PFOS,O%) was observed within 10 min of treatment. Compared to bubbling with nitrogen alone, and nitrogen with cetrimonium bromide (CTAB) in bulk solution, CGAs demonstrate significantly higher removal of perfluorobutanoic acid, a short-chain PFAS (0% for N-2, 11% for N-2 + CTAB, and 90% for CGAs). These results suggest that CGAs may serve as a promising new separation and concentration technology for removing a suite of PFAS from water, particularly for difficult to remove short-chained compounds.