Per- and Polyfluoroalkyl Substances (PFAS) Separation Efficiency in Conventional and Shear-Induced Foam Fractionation Systems

Abstract

Per- and polyfluoroalkyl substances (PFAS) are synthetic compounds found widely in the environment, posing concerns due to their persistence, recalcitrant nature, and limited regulatory standards. Recently, foam fractionation (FF) has attracted interest for PFAS removal by concentrating contaminants at air–water interfaces within the generated foam. This study evaluates the effectiveness of FF for the removal of PFAS from waters impacted by aqueous film-forming foam (AFFF). The performance of conventional bubble-induced (BI) FF and an innovative shear-induced (SI) FF system was assessed, and 12 different single-stage FF scenarios (2 systems, 2 water types, and 3 surfactant dosages) revealed a direct correlation between removal efficiency and PFAS chain length, surfactant concentration, and aeration/mixing duration. Results also confirmed higher removals for sulfonate PFAS compared to carboxylates. While both systems achieved high removal efficiencies (>90% for long-chain PFAS with 6 and 9 mg/L CTAB), the SI system reached similar removal levels in approximately 80% less time while exhibiting higher velocity gradients, energy consumption, and foam generation across all cases. Moreover, SI-FF’s faster operation and higher foamate generation suggest its suitability for final stage fractionation, which was tested and shown to substantially outperform BI-FF in a dual-stage system.