Simple method discovered to destroy PFAS

There’s finally hope for a simple, cheap way to destroy a class of ubiquitous environmental toxins found in shampoos, fast-food wrappers, and fire-dousing foams. A common ingredient in soap, mixed with water and an organic solvent, readily degrades per- and polyfluoroalkyl substances (PFAS), commonly known as ‘forever chemicals’, a new study shows. 

PFAS contain strings of carbon atoms attached to fluorine atoms, which bind so tightly to one another they are nearly impossible to break apart. The compounds repel oil and water and can withstand friction and high temperatures, making them widely popular in industry. They accumulate in soils, water supplies, and even in living tissue. Numerous studies have shown they are toxic in minute quantities.

Two years ago, researchers at the U.S. Environmental Protection Agency hit on a better approach by chance. When they placed a PFAS compound in a common solvent called DMSO as part of a toxicity study, the PFAS compound began to degrade. The new study builds on that work. Researchers studied numerous recipes involving DMSO. One combined a little bit of the solvent with sodium hydroxide, a common component of soap, in water. When the team heated the mix to boiling temperature, it readily degraded one of the largest subsets of PFAS compounds.

The PFAS compounds in question—used in fire-fighting foams and the production of nonstick coatings—contain a chemical group called a carboxylic acid, a small cluster of carbon, oxygen, and hydrogen atoms. Computer calculations revealed DMSO knocks off the carboxylic acid group. What’s left behind is mostly easily captured fluorine ions, and a mixture of harmless, naturally occurring carbon and oxygen containing byproducts.

Roughly 40% of PFAS compounds contain carboxylic acid groups, and thus could potentially be degraded by the new approach. Though it has yet to be tested in the field, the most likely strategy would be to use conventional means to filter PFAS chemicals from, say drinking water, and then treat them off-site.

The method doesn’t work on all types of PFAS, however. Compounds used in flame retardants and batteries, for example, contain a sulfonate group instead of a carboxylic acid group and won’t break down with this approach. Yet, the new work offers hope that other researchers will be able to find mild recipes to tear apart these forever chemicals as well.

Science.org