University of California Los Angeles
PhD candidate working with Dr. Shaily Mahendra on PFAS remediation at Department of Civil and Environmental Engineering, UCLA
Ultrasonic Nanobubbles Mediated Destruction of Per- and Polyfluoroalkyl Substances Mixtures in Groundwater
Shashank Singh Kalra,† Brian Cranmer,‡ Gregory Dooley,‡ Sanjay Mohanty,† Jens Blotevogel,# and Shaily Mahendra,∗,†
†Civil and Environmental Engineering, University of California, Los Angeles 5732 Boelter Hall, Los Angeles, 90095, California, United States ‡Environmental and Radiological Health Sciences, Colorado State University, 1680 Campus Delivery, Fort Collins, Colorado 80523, United States #Center for Contaminant Hydrology, Colorado State University, 1320 Campus Delivery, Fort Collins, 80523, Colorado, United States
Per- and polyfluoroalkyl substances (PFASs) are anthropogenic amphipathic heat resistant materials found in some household items and in Aqueous Film Forming Foams (AFFFs). There is a critical need for developing destructive and non-destructive technologies for their removal from contaminated environments. Ultrasonic destruction of PFASs employs high-frequency sound waves to generate nanoscale bubbles, which implode under high acoustic pressure causing pyrolysis of chemical bonds. We report the destruction of perfluoro-1-octanesulfonamide (FOSA-I), 1H,1H,2H,2H-perfluorooctane sulfonate (6:2FTS), perfluoro-n-octanoic acid (L-PFOA), perfluoro-1-octanesulfonate (L-PFOS), perfluoro-1-butanesulfonate (L-PFBS), N-(carboxymethyl)N,N-dimethyl-N-[3-(1H,1H,2H,2H-perfluoro-1-octanesulfonamido)propan-1-yl] ammonium (NCMAmp-6:2FOSA or 6:2 FTAB) and, a mix of 24 native PFASs (PFAC-24PAR) at 900 kHz and 300 W. PFOA removal rates were found to be independent of initial concentration within the tested range. Moreover, PFASs followed first-order removal kinetics with removal rates increasing with chain length. For the same chain length, carboxylates had higher removal rates as compared to sulfonates. The half-lives for the individual PFASs as well as PFAC-24PAR ranged from 18 min to 120 min in contaminated groundwater and 11 min to 76 min in deionized water. Significant increases in rates of removal for shorter chain PFASs were observed in groundwater when compared to the removal rates in deionized water; however, the effect was opposite for longer chain compounds. Our results imply that ultrasonic nanobubble technology with its ability to mineralize PFASs could be a viable treatment for PFAS-contaminated environmental media.