Ultrasonication degradation of per- and polyfluoroalkyl substances (PFAS) in synthetic environmental samples: Impact of ionic composition and water chemistry

This study investigates the effectiveness of ultrasonication in degrading per- and perfluoroalkyl substances (PFAS) in different water matrices, including seawater (SW) and creek water (CW), with the results compared to those obtained from control Milli-Q water (MQ). Various salts were introduced in a controlled manner to understand the influence of ionic background on the ultrasonic degradation of PFAS. Two experimental setups were employed to explore the role of water matrix and the applicability of the method to real-world scenarios. In the first setup, experiments were conducted using synthetic samples prepared by spiking SW and CW with perfluorooctanoic acid or PFOA, perfluorooctane sulfonate or PFOS, 6:2 fluorotelomer sulfonate or 6:2 FTS, aqueous film-forming foam (AFFF), and form fractionate (FF). In the second setup, PFAS-contaminated groundwater (GW) was ultrasonicated to evaluate the PFAS remediation in contaminated aquifers. The ultrasonic system achieved ∼82 % PFAS degradation removal in GW. Notably, the ultrasonic system achieved above 100 % defluorination in MQ and CW for AFFF and FF, suggesting complex degradation mechanisms and challenges in closing the mass balance. In contrast, SW showed lower defluorination (72 %/81 % for AFFF/FF), aligning with lower defluorination observed for individual PFAS in SW (2.3–56 %) compared to MQ (47–86 %) and CW (28–85 %). These results highlight the inhibitory effect of high salinity on the ultrasonic defluorination of PFAS. Overall, the results underscore the role of water matrix composition in PFAS treatment and demonstrate the potential of ultrasonication as an effective remediation technique for PFAS across various aquatic environments. • PFAS degradation pattern differs in Milli-Q water and natural waters. • Ultrasonication of PFAS is effective in creek water, a low-salinity environment. • High salinity of seawater inhibits the effectiveness of ultrasonication of PFAS. • Defluorination and degradation of PFAS in natural waters differ significantly. • PFAS mass balance closure is key towards scale-up applications.