Kinetics and Mechanism of Ultrasonic Defluorination of Fluorotelomer Sulfonates.

Ultrasound degrades "legacy" per- and polyfluoroalkyl substances (PFAS) via thermolysis at the interface of cavitation bubbles. However, compared to "legacy" PFAS, polyfluoroalkyl substances have a lesser affinity to the interface and may react with OH. To understand the effect of size on degradation kinetics and mechanism of polyfluoroalkyl substances, this work compared ultrasonic treatment ( = 354 kHz) of :2 fluorotelomer sulfonates (FTSAs) of varying chain lengths ( = 4, 6, 8).

In Situ EPR Spin Trapping and Competition Kinetics Demonstrate Temperature-Dependent Mechanisms of Synergistic Radical Production by Ultrasonically Activated Persulfate.

Ultrasound coupled with activated persulfate can synergistically degrade aqueous organic contaminants. Here, in situ electron paramagnetic resonance spin trapping was used to compare radicals produced by ultrasonically activated persulfate (US-PS) and its individual technologies, ultrasound alone (US) and heat-activated persulfate (PS), with respect to temperature. Radicals were trapped using 5,5-dimethyl-1-pyrroline--oxide, DMPO, to form detectable nitroxide adducts.

Synergistic, aqueous PAH degradation by ultrasonically-activated persulfate depends on bulk temperature and physicochemical parameters.

Coupling ultrasound with other remediation technologies has potential to result in synergistic degradation of contaminants. In this work, we evaluated synergisms from adding high-power ultrasound (20 kHz; 250 W) to activated persulfate over a range of bulk temperatures (20-60 °C). We studied the aqueous degradation kinetics of three polycyclic aromatic hydrocarbons (PAHs: naphthalene, phenanthrene, and fluoranthene) treated by ultrasound-alone, heat-activated persulfate, and combined ultrasonically-activated persulfate (US-PS).