There’s a new way to destroy harmful “permanent chemicals,” scientists say.
Perfluoroalkyl and polyfluoroalkyl substances, also known as PFAS, are found in nonstick pans, water-repellent fabrics, and food packaging and they are ubiquitous throughout the environment. They are nicknamed eternal chemicals for their ability to stay put and not break down. In part, that’s because PFAS have a super-strong bond between their carbon and fluorine atoms (Serial number: 4/6/19). Now, using a little heat and two relatively common compounds, researchers have degraded an important type of chemical forever in the labreports the team on August 19 Sciences. The work could help pave the way for a process to commercially break down certain permanent chemicals, for example, by treating wastewater.
“The fundamental understanding of how materials degrade is the most important thing to come out of this study,” organic chemist William Dichtel said at a news conference on August 16.
While some scientists have found relatively simple ways to breakdown of selected PFASMost degradation methods require rigorous, energy-intensive processes that use intense pressure, in some cases over 22 megapascals, or extremely high temperatures, sometimes over 1000⁰ Celsius, to break chemical bonds. (NS: 6/3/22).
Dichtel, of Northwestern University in Evanston, Illinois, and his team experimented with two substances found in almost every chemistry lab cabinet: sodium hydroxide, also known as lye, and a solvent called dimethyl sulfoxide, or DMSO. The team worked specifically with a group of permanent chemicals called PFCAs, which contain carboxylic acid and make up a large percentage of all PFAS. Some of these types of forever chemicals are found in waterproof clothing.
When the team combined the PFCAs with the bleach and DMSO at 120⁰ C and without the need for additional pressure, the carboxylic acid broke away from the chemical and converted to carbon dioxide in a process called decarboxylation. What happened next was unexpected, Dichtel said. The loss of the acid led to a process that caused “the entire molecule to fall apart in a cascade of complex reactions.” This cascade involved steps that degraded the rest of the chemical into fluoride ions and smaller carbon-containing products, leaving virtually no harmful byproducts. .
“It’s a clean method, it’s different from others that have been tried,” says Chris Sales, an environmental engineer at Drexel University in Philadelphia, who was not involved in the study. “The bigger question is, how could this be adapted and scaled up?” Northwestern has filed a provisional patent on behalf of the researchers.
Understanding this mechanism is just one step in undoing the chemicals for good, the Dichtel team said. And more research is needed: there are other classes of PFAS that require their own solutions. This process would not work to address PFAS in the environment, because it requires a concentrated amount of chemicals. But one day it could be used in sewage treatment plants, where contaminants could leach out of the water, concentrate, and then break down.