Forever Chemicals No More? PFAS Are Destroyed With New Technique

An anonymous reader quotes a report from the New York Times: A team of scientists has found a cheap, effective way to destroy so-called forever chemicals, a group of compounds that pose a global threat to human health. The chemicals -- known as PFAS, or per- and polyfluoroalkyl substances -- are found in a spectrum of products and contaminate water and soil around the world. Left on their own, they are remarkably durable, remaining dangerous for generations. Scientists have been searching for ways to destroy them for years. In a study, published Thursday in the journal Science, a team of researchers rendered PFAS molecules harmless by mixing them with two inexpensive compounds at a low boil. In a matter of hours, the PFAS molecules fell apart. The new technique might provide a way to destroy PFAS chemicals once they've been pulled out of contaminated water or soil. But William Dichtel, a chemist at Northwestern University and a co-author of the study, said that a lot of effort lay ahead to make it work outside the confines of a lab. "Then we'd be in a real position to talk practicality," he said. At the end of a PFAS molecule's carbon-fluorine chain, it is capped by a cluster of other atoms. Many types of PFAS molecules have heads made of a carbon atom connected to a pair of oxygen atoms, for example. Dr. Dichtel came across a study in which chemists at the University of Alberta found an easy way to pry carbon-oxygen heads off other chains. He suggested to his graduate student, Brittany Trang, that she give it a try on PFAS molecules. Dr. Trang was skeptical. She had tried to pry off carbon-oxygen heads from PFAS molecules for months without any luck. According to the Alberta recipe, all she'd need to do was mix PFAS with a common solvent called dimethyl sulfoxide, or DMSO, and bring it to a boil. "I didn't want to try it initially because I thought it was too simple," Dr. Trang said. "If this happens, people would have known this already." An older grad student advised her to give it a shot. To her surprise, the carbon-oxygen head fell off. It appears that DMSO makes the head fragile by altering the electric field around the PFAS molecule, and without the head, the bonds between the carbon atoms and the fluorine atoms become weak as well. "This oddly simple method worked," said Dr. Trang, who finished her Ph.D. last month and is now a journalist. Unfortunately, Dr. Trang discovered how well DMSO worked in March 2020 and was promptly shut out of the lab by the pandemic. She spent the next two and a half months dreaming of other ingredients which she could add to the DMSO soup to hasten the destruction of PFAS chemicals. On Dr. Trang's return, she started testing a number of chemicals until she found one that worked. It was sodium hydroxide, the chemical in lye. When she heated the mixture to temperatures between about 175 degrees to 250 degrees Fahrenheit, most of the PFAS molecules broke down in a matter of hours. Within days, the remaining fluorine-bearing byproducts broke down into harmless molecules as well. Dr. Trang and Dr. Dichtel teamed up with other chemists at U.C.L.A. and in China to figure out what was happening. The sodium hydroxide hastens the destruction of the PFAS molecules by eagerly bonding with the fragments as they fall apart. The fluorine atoms lose their link to the carbon atoms, becoming harmless. [...] Dr. Dichtel and his colleagues are now investigating how to scale up their method to handle large amounts of PFAS chemicals. They're also looking at other types of PFAS molecules with different heads to see if they can pry those off as well.

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