Foiling forever chemicals with ultrasound
S. Himmelstein | November 16, 2023
An ultrasonic approach devised at The Ohio State University offers a route to the removal of environmentally persistent and biologically hazardous “forever chemicals” — per- and poly-fluoroalkyl substances (PFAS) — from groundwater.
The ultrasound technique was previously demonstrated to eliminate pharmaceuticals in municipal tap water and wastewater. The process transmits sound at a frequency considerably lower than generally employed for medical imaging, forming cavitation bubbles that are pulled apart by the low-pitched pressure pulse of ultrasound. During compression, the bubbles can reach temperatures of up to 10,000 Kelvin, which dissolves the stable carbon-fluorine bonds in the PFAS, rendering the byproducts largely harmless.
Experiments were conducted with laboratory-made mixtures containing three differently sized compounds of fluorotelomer sulfonates — PFAS compounds common in firefighting foams. Results published in The Journal of Physical Chemistry A showed that smaller compounds degraded much faster than the larger ones over a three-hour treatment period. This observation is in contrast to many other PFAS treatment methods in which smaller PFAS are actually more challenging to treat.
Water resource managers are advised to consider using ultrasound in future treatment technology development and with other combined-treatment approaches.