Researchers in the American Chemical Society’s (ACS) Environmental Science & Technology Letters report a new type of additive for “ball milling” that completely breaks down per- and polyfluoroalkyl substances (PFAS) at ambient temperature and pressure.
Ball milling, a process that mixes PFAS and additives with metal balls at high speeds, creates 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. To overcome these limitations, researchers turned to boron nitride, a piezoelectric material that generates partial electrical charges and can accept electrons when deformed by mechanical forces. They now report a ball-milling process that uses boron nitride as a non-corrosive additive to react with and destroy PFAS.
According to a press release from ACS, 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. The method also broke down 80% of known PFAS from soils contaminated with firefighting foam after six 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.
