Key points:
- PFAS contamination is growing, and so too are methods to destroy the “forever chemicals.”
- Researchers introduce a new ball milling technique that completely breaks down PFAS at ambient temperature and pressure.
- The technique relies on a non-corrosive additive and is not as energy-intensive as current methods.
Concerns about per- and polyfluoroalkyl substances (PFAS) contamination have been growing in recent years. Currently, the U.S. Environmental Protection Agency recommends incineration to destroy these substances, but concerns remain about whether this energy-intensive method can effectively prevent environmental contamination.
One emerging technique to degrade PFAS involves forcefully grinding them with metal balls in a moving container, but this technique can require corrosive additives. Now, researchers in ACS’ Environmental Science & Technology Letters report a new type of additive for “ball milling” that completely breaks down PFAS at ambient temperature and pressure.
The current ball milling process mixes PFAS and additives with metal balls at high speeds. Collisions between the balls and additives create solid-state reactions that break the carbon-fluorine bonds on PFAS and convert them to less harmful products. A common additive for this process is potassium hydroxide (KOH), but it forms problematic clumps and is corrosive.
In the new study, researchers at Clarkson University turned to boron nitride, a non-corrosive piezoelectric material that generates partial electrical charges and can accept electrons when deformed by mechanical forces.
As a proof-of-concept for the new additive, the team ball milled two legacy PFAS compounds with boron nitride and analyzed the products. By optimizing the ratio of boron nitride to PFAS, the team almost completely removed the fluorine atoms from PFAS in four hours at ambient temperature and pressure, effectively destroying it. According to the study, the method also broke down 80% of known PFAS from soils contaminated with firefighting foam after 6 hours.
In both experiments, boron nitride degraded PFAS more efficiently than when KOH was used. Further analyses suggest that boron nitride accepts electrons and fluorine atoms from PFAS, which then breaks into fluoroalkyl radical species that react with oxygen or other radicals to ultimately produce innocuous minerals.
This new method could open the door for future mechanical-force-based PFAS remediation strategies, say the researchers.
Information provided by American Chemical Society.