Fluorine has two very different faces. In per- and polyfluoroalkyl substances, better known as PFAS or “forever chemicals,” it helps create some of the strongest bonds in organic chemistry, making these compounds extraordinarily persistent in the environment. Yet fluorine is also a valuable element in modern chemical manufacturing and is widely used in pharmaceuticals, agrochemicals and advanced materials.
That contrast raised a simple question: Could the fluorine locked inside persistent pollutants be recovered and given a second life?
At Rice University, our research group has spent several years developing rapid electrothermal approaches for tackling fluorinated wastes. The technology is based on flash Joule heating, in which a short electrical pulse delivers energy directly to a conductive material, raising its temperature extremely rapidly within seconds. Unlike conventional furnace heating, which gradually transfers heat from the outside inward, flash heating creates a brief, intense reaction environment that can rapidly break strong chemical bonds and drive unusual high-temperature transformations.
Our earlier studies showed that this approach could destroy PFAS in contaminated soils and granular activated carbon and convert their fluorine into stable mineral forms (Nat. Commun., 2024, 15, 6117. Nat. Water, 2025, 3, 486–496). We subsequently extended the concept to other PFAS-containing materials and explored how waste-derived fluorine could participate in useful chemical processes, including lithium recovery from brines (Nat. Water., 2026, 4, 369–380). These studies gradually shifted our thinking. Rather than asking only how to remove or mineralize PFAS, we began asking whether the fluorine itself could be recovered as a chemical resource.
That idea led us to silver fluoride, or AgF. AgF is a useful fluorination reagent that can transfer fluorine into organic molecules, including chemical building blocks relevant to pharmaceutical synthesis. Silver is also attractive because it can be recovered and reused. In our process, even the initial silver source can come from waste silver-containing conductive films, affording an opportunity to combine two waste streams in a single recovery strategy.
There was, however, a major chemical challenge. PFAS are commonly captured on activated carbon, but activated carbon generates a strongly reducing environment during rapid heating. If silver or newly formed AgF comes into direct contact with carbon, AgF can be reduced back to metallic silver before it can be recovered.
The solution turned out to be surprisingly simple: keep them apart, but let the fluorine travel between them.
We developed a process called flash-encapsulated fluorination, in which a porous glass-fiber barrier physically separates the silver from the PFAS-loaded activated carbon (Fig. 1). The glass-fiber layer prevents direct contact between the carbon and silver while allowing volatile fluorine-containing species generated during the flash process to pass through. These fluorine species then react with silver on the other side of the barrier to form AgF.
Fig. 1. Schematic illustration of the flash encapsulated fluorination process.
In this way, the encapsulated architecture performs two jobs at once. It protects the newly formed AgF from reduction while allowing a pathway for fluorine to move from the waste into a useful chemical reagent. The process occurs within seconds and converts waste-derived fluorine into AgF that can subsequently be used for organic fluorination. The waste fluorine was from aqueous film-forming foam (AFFF, or firefighting foam) adsorbed from water onto granulated activated carbon (GAC), while the silver was obtained from Ag-rich ash produced by calcining waste conductive films.
The story does not end after one reaction. When AgF transfers fluorine to an organic molecule, the silver is converted into other silver salts such as AgCl or AgBr. These silver-containing residues can then be recovered, exposed again to fluorine released from waste, and regenerated into AgF. The silver therefore acts as a recyclable carrier that helps move fluorine from persistent waste into useful chemical products (Fig. 2).
Fig. 2. Conceptual schematic of the circular utilization of fluorine resources.
This changes the way we can think about PFAS treatment. Traditional adsorption technologies can effectively remove PFAS from water, but they largely transfer the pollutants from one medium to another, leaving behind contaminated activated carbon that still requires further treatment. Destruction technologies address that problem by breaking down PFAS, but the fluorine is usually treated as something that must simply be immobilized or disposed of.
Our goal was to take the next step: not only destroy the persistent pollutant, but also recover the fluorine and put it back to work.
By linking PFAS destruction, fluorine recovery and fluorochemical synthesis, flash encapsulated fluorination offers a different vision for managing fluorinated waste—one in which an environmental liability can become a feedstock for useful chemistry. Rather than ending the story of PFAS with destruction, the process opens the possibility of beginning a new chemical cycle for the fluorine they contain.
Publication link: https://www.nature.com/articles/s44286-026-00442-8