Using sulfite and iodide under ultraviolet light can destroy PFAS in water within hours

Once dubbed “chemicals forever,” per- and polyfluoroalkyl substances, or PFAS, might be in the market for a new moniker.

That’s because adding iodide to a water treatment reactor that uses ultraviolet (UV) light and sulfite destroys up to 90% of the carbon-fluorine atoms in PFAS chemicals forever. in just hours, reports a new study by environmental engineering researchers at UC Riverside. Adding iodide increases the rate of the reaction up to four times, saving energy and chemicals.

“Iodide really does a substantial job,” said corresponding author Jinyong Liu, assistant professor of chemical and environmental engineering. “Not only does this speed up the reaction, but it also makes it possible to treat ten times higher concentrations of PFAS, even some very recalcitrant structures.”

Liu’s lab has been working on ways to destroy PFAS through photochemical reactions since 2017. The new method has already attracted industry interest, and Liu’s group is partnering with companies to conduct pilot tests.

Synthetic chemicals known as PFAS contain multiple, very strong carbon-fluorine bonds. The widespread use of these non-biodegradable compounds in countless products since the 1940s has contaminated water supplies across America, with various negative effects on human and animal health. Because the carbon-fluorine bond is very difficult to break, PFAS pass through most water treatment systems unchanged.

Photochemical degradation by UV light and sulfite (SO32−) is, to date, one of the most effective means of breaking down PFAS. The original process used a lot of electricity because the chemical reactions happened slowly. It also left multiple carbon-fluorine bonds in the breakdown products, with unknown health effects.

Last year, researchers reported that oxidation treatments before and after UV/sulfite treatment can achieve nearly 100% destruction of carbon-fluorine bonds in various major PFAS pollutants.

In the new work, the researchers added iodide to the UV/sulfite system to treat a particularly stubborn four-carbon PFAS molecule called perfluorobutane sulfonate (PFBS), which degrades poorly in the original UV/sulfite setting. . The iodide accelerated the reaction and completely eliminated the PFBS in 24 hours.

As expected, the UV/sulfite+iodide system also readily degraded other PFAS, such as the frequently reported eight-carbon PFOA and PFOS. The addition of iodide also allowed the system to destroy concentrated PFAS in a brine solution, which presents a practical challenge for groundwater remediation. Ion exchange systems are used to clean up groundwater, but the PFAS chemicals captured in the resin must be washed and destroyed cost-effectively.

Source of the story:

Materials provided by University of California – Riverside. Original written by Holly Ober. Note: Content may be edited for style and length.

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