Molecular Achilles' heel breaks down toxic PFAS "forever chemicals"
Toxic PFAS compounds earn themselves the nickname of “forever chemicals” thanks to their tendency to persist in the environment for decades. In a new study, chemists claim to have found an Achilles’ heel to these ultra-stable molecules, using a relatively simple chemical reaction to “decapitate” some kinds of PFAS into benign end products.
Per- and polyfluoroalkyl substances (PFAS) is an umbrella term for thousands of chemicals that have been commonly used for their water-repelling properties in products such as non-stick cookware, food packaging, waterproof clothing and firefighting foam. However, a growing body of research over the last few decades has linked PFAS chemicals to a range of health problems, such as diabetes, infertility, hypothyroidism, and kidney and liver cancer, leading the EPA to lower the safe threshold in drinking water to near zero.
Worse still, decades of widespread use coupled with an infamously long life means that exposure is hard to avoid. A recent study found that PFAS levels in rainwater all over the world exceed the EPA’s guidelines, even in samples taken from remote areas like Antarctica or the Tibetan Plateau.
Scientists have been investigating ways to break down the chemicals using boron nitride powders or photochemical reactions. In the new study, researchers at Northwestern University have found a new way to degrade PFAS compounds using simple and inexpensive chemicals and under mild conditions.
PFAS gets its incredible and frustrating stability from its molecular structure – it’s made up mostly of carbon and fluorine bonds, which are the strongest known to organic chemistry. But the team discovered a weakness at the head of the molecule, where charged groups of atoms like oxygen can be found.
The team targeted this area instead, by heating PFAS samples to between 80 and 120 °C (176 and 248 °F) in dimethyl sulfoxide as a solvent and sodium hydroxide as a reagent. And sure enough, this head group was “decapitated” from the molecule, leaving a reactive tail that cascaded through the structure.
“That triggered all these reactions, and it started spitting out fluorine atoms from these compounds to form fluoride, which is the safest form of fluorine,” said William Dichtel, lead author of the study. “Although carbon-fluorine bonds are super strong, that charged head group is the Achilles’ heel.”
Using this process, the team successfully broke down 10 different types of PFAS, including PFOA and a particularly problematic chemical known as GenX, degrading up to 100% within 24 hours. The researchers say future work will continue testing the method on other types of PFAS, of which there are thousands.
The research was published in the journal Science.
Source: Northwestern University