US researchers have discovered a new strategy to clean up “forever chemicals” from contaminated water and importantly, it can do so at room temperatures.
Per- and polyfluoroalkyl substances (PFAS) are entirely man-made chemicals widely used for their heat-resistant, and water, oil, and dirt-repellent properties.
However, PFAS’ stubbornly strong carbon-fluorine bonds are resistant to chemical and biological degradation, which allows them to persist indefinitely in the environment.
Results from epidemiological studies and animal testing have linked PFAS exposure to health problems, so there is an increasingly urgent need for strategies to degrade them.
The new method detailed in the journal Nature Water involves treating heavily contaminated water with ultra-violet (UV) light, sulphite (SO32−) and electrochemical oxidation.
“In this work, we continued our research on the UV-based treatment, but this time, we had a collaboration with an electrochemical oxidation expert at Clarkson University,” says co-author Jinyong Liu, an associate professor of chemical environmental engineering at the University of California, Riverside.
“We put these two steps together and we achieved near-complete destruction of PFAS in various water samples contaminated by [fire-suppressing] foams.”
Fire-suppressing foams are a major source of PFAS pollution in groundwater because they have been used for decades to extinguish aviation fuel fires at military sites and commercial airports.
The foams form an aqueous film around burning petrol and other flammable liquids, which deprives the fire of oxygen and extinguishes it.
Breaking down PFAS involves complete defluorination, meaning all of the strong carbon-fluorine bonds are cleaved.
The foams also contain various other concentrated organic compounds that further hinder this process.
“In the real world, the contaminated water can be very complicated. It contains a lot of things that might potentially slow down the reaction,” Liu says.
Liu and collaborator Yang Yang, assistant professor of civil and environmental engineering at Clarkson University, found that combining UV light with electrochemical oxidation breaks up organics and allows the reactions to occur at room temperature without a need for additional heat or high pressure to stimulate the reaction.
Liu says the method is well suited for cleaning heavily contaminated water used to flush out tanks, hoses, and other firefighting equipment. The method also can be used to treat leftover containers of PFAS-containing foams.
The method could also regenerate the resin beads used in existing treatment strategies to remove PFAS from groundwater.
“We want to have sustainable management of the resin. We want to reuse it,” says Liu.
