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UV Method Helps To Clean Up Harmful PFAS

Trainee firefighters putting out a car fire using firefighting foam.
Credit: Włodek / Pixabay.
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Aqueous film-forming foam (AFFF) is incredibly efficient at putting out fires. These foams form an aqueous film over burning gasoline, fuels and other flammable liquids, which quickly deprives the blaze of oxygen and extinguishes it. For this reason, AFFF is often used for rapid fire suppression on military bases and at commercial airports.

But, while lifesaving in one way, AFFF also comes with significant health risks of its own; the foam is full of per- and polyfluoroalkyl substances (PFAS). Sustained exposure to these chemicals has been linked to serious health problems, including reproductive issues and an increased risk of some cancers. Recent assessments of 715 military sites carried out by the US Department of Defense have found concerningly high levels of PFAS at 574 sites due to the use of AFFF, with the federal government now requiring cleanups or further investigations.  

But how exactly do you clean up PFAS contamination? Researchers at the University of California Riverside (UCR) and Clarkson University think they have an answer. Published in Nature Water, the researchers’ new method promises to destroy nearly all the PFAS compounds present in AFFF-contaminated water.

Using light to tackle PFAS contamination

The new treatment method involves using ultraviolet (UV) light in conjunction with a sulfite–electrochemical oxidation process to degrade PFAS and other organic chemicals present in AFFF.

“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,” said Jinyong Liu, an associate professor of chemical environmental engineering at UCR, who has published nearly 20 papers on treating PFAS pollutants in contaminated water. “We put these two steps together and we achieved near-complete destruction of PFAS in various water samples contaminated by the foams.”

Water contamination by AFFF foams is a surprisingly tricky nut to crack. In addition to PFAS, these foams can also release other unwanted organic compounds into the water, which can hinder attempts to break the strong carbon–fluorine bonds in PFAS and make their remediation even more difficult.

“In the real world, the contaminated water can be very complicated,” Liu said. “It contains a lot of things that might potentially slow down the reaction.”

Liu’s team had previously worked on a PFAS eradication method using UV light and sulfite that was able to destroy up to 90% of these carbon–fluorine bonds. Now, by incorporating the expertise from the Clarkson University electrochemical oxidation group, the team’s hybrid method promises to realize the “near-complete defluorination and mineralization of most PFAS and organics in AFFF” by targeting the organics too.

Cleansing highly contaminated groundwater

The team said that their new decontamination method is well suited for cleansing the highly contaminated water that results from flushing out used tanks, containers, hoses and other firefighting equipment.

They also believe that the method could help water utilities deal with polluted groundwater. One common method for tackling PFAS-contaminated groundwater is the use of ion exchange resin beads, which “grab” onto PFAS molecules and help with their removal. By combining this with the new photo-electrochemical process, Liu hopes that it should be possible to regenerate and recycle these beads, making the water treatment process more sustainable overall.

“We want to have sustainable management of the resin,” Liu said. “We want to reuse it.”

Reference: Guan Y, Liu Z, Yang N, et al. Near-complete destruction of PFAS in aqueous film-forming foam by integrated photo-electrochemical processes. Nat Water. doi: 10.1038/s44221-024-00232-7

This article is a rework of a press release issued by the University of California Riverside. Material has been edited for length and content.