Fluorine reclaimed from PFAS in mechanochemical process

A straightforward mechanochemistry method can break down problematic PFAS compounds while simultaneously recovering the fluoride they contain for use in the production of commercial fluorochemicals (Nature 2025, DOI: 10.1038/s41586-025-08698-5).

The accumulation of per- and polyfluoroalkyl substances, known as PFAS, is a growing cause of concern. Their strong carbon–fluorine bonds give these compounds excellent chemical and thermal stability, and they are widely used in applications as diverse as packaging, textile treatments, and firefighting equipment. Those same useful properties also make PFAS-based materials incredibly resistant to degradation. Rising concentrations in the environment coupled with worrying evidence about the health implications of exposure have made clear the urgent need for methods that safely destroy these chemicals and prevent further contamination.

Intriguingly, tackling the PFAS problem was not a primary focus for Véronique Gouverneur and her team at the University of Oxford. While the group was investigating safer methods to produce fluorochemicals from fluorspar, the major mineral source of fluorine, they developed a simple mechanochemical procedure combining the raw mineral with phosphate salts. The results seemed too good to be true. The process returned a greater than 100% yield of fluoride.

It took a lucky observation to resolve the discrepancy. “Our postdoc Long Yang noticed that the specific jar, instead of having a rubber seal, which is what we use all the time, had a [polytetrafluoroethylene] seal,” explains Gouverneur. “That made us realize that perhaps those mechanical conditions, and applying a phosphate salt, was able to harvest the fluoride content and therefore destroy the PTFE.”

The team moved quickly to investigate the mechanism underlying this destructive process, beginning by establishing exactly what had formed in the ball mill. NMR revealed that the PTFE fluoropolymer was broken into a variety of mineralized carbon fragments, including graphite, carbonates, and oxalates, combined with a mixture of recyclable phosphate salts. The team recovered fluoride either as ions that can be used in fluorination chemistry or as fluorophosphates that can be diverted into other forms, including tetrabutylammonium fluoride, says Gouverneur.

In particular, the phosphate salt proved essential for the degradation process, with the carbonate and hydroxide alternatives both yielding inferior results. The team’s long-term collaborator Robert Paton used density functional theory calculations to study a possible breakdown mechanism. The group hypothesizes that the phosphate anion behaves as a nucleophile, enabling it to break the C–F bonds. The reaction was then successfully validated on a variety of solid waste PFASs, including Teflon tape, plastic tubing, and wire insulation. Gouverneur is now working on translating the process to a commercial scale.

Linda Weavers at the Ohio State University was excited by the circularity of the approach and believes it could be a valuable complement to existing remediation and destruction strategies. “Processes like this, where you can break down components to get back a valuable starting material, are a very important area of research,” she says. “This might be a way to get the PFAS off the activated carbon [used] to remove these compounds from water systems.”

Timm Strathmann at the Colorado School of Mines believes that although the new process is innovative, environmental and economic analysis will be required before the method is ready for commercial development. “I would like to see rigorous life cycle and techno-economic assessments of this cyclic process that they’re proposing, in comparison to simply destroying the PTFE and recovering the fluoride by calcium fluoride precipitation,” he says.