Scientists Found an Easy Way To Destroy Toxic ‘Forever Chemicals’

May 28, 2024

Chemists discovered a simple way to get rid of some types of PFAS, the toxic chemicals left over from plastics.

For over a century, our world has been made of plastic. It’s in everything from firefighting foam to water bottles to nonstick pans, yielding convenient products that last. But in the long run, plastic releases hazardous chemicals, called Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS), that seep into the soil and groundwater. These “forever chemicals” are everywhere today: in our drinking supplies, our food, the air, and even our bodies, where they can lead to unwelcome consequences, including cancer, infant development problems, and weakened immunity.

Scientists have been working on ways to destroy PFAS chemicals that permeate our environment, but no easy method exists. That’s because these standoffish compounds don’t react to anything—not biological or other chemical agents. They stick only to each other and resist being torn apart. Current methods require “very harsh conditions to decompose these compounds,” according to chemists at Northwestern University in Evanston, Illinois. Until now, how to break those PFAS bonds has been unclear.

That team’s recent work, published in the journal Science on August 18, proves that the stubborn power of PFAS bonds can, in fact, be broken. The scientists discovered a way to disintegrate two concentrated, toxic forms of PFAS into smaller, innocuous compounds that decompose. Using low heat, a solvent, and sodium hydroxide (lye, the basis of some soaps), the method is both simple and inexpensive. It works for two major categories of PFAS permeating the environment today: perfluorooctanoic acid (PFOA) and one of its common replacements, known as GenX.

The traditional difficulty in destroying a PFAS compound lies in its many carbon-fluorine bonds, which organic chemists know as the strongest bonds. They require immense heat (about 400 degrees Celsius) and pressure to break, which can lead to cases of air contamination during incineration, William Dichtel, the lead author of the new study, explains in a news release. “In New York state, a plant claiming to incinerate PFAS was found to be releasing some of these compounds into the air,” says Dichtel, a professor of chemistry. “The compounds were emitted from the smokestacks and into the local community.” And burying PFAS just causes them to contaminate the environment after a few decades, he adds.

Not all PFAS break down into microplastics, but some, like polyvinyl fluoride (PVF) and polytetrafluorethylene (PTFE), do. PFAS is also used in coatings for synthetic textiles and in plastics that break down into fiber- or particle-based microplastics. Let’s explore the connection.

It turns out that PFAS chemicals have a weak spot: they often include charged oxygen atoms at one end of their molecules. Dichtel’s team chose an uncommon solvent, dimethyl sulfoxide, which allowed them to heat the PFAS gently between 80 and 120 degrees Celsius along with sodium hydroxide, a typical reagent that helps cause a chemical reaction. The result was a flurry of reactions, starting with the charged oxygen atoms falling off. Then fluorine atoms fell off as well, abandoning their carbon companions to form fluoride, a safe form of fluorine. The whole process took only 12 hours, by which time, more than 90 percent of the PFAS chemicals were converted into safe carbon byproducts. Dichtel called the group of charged atoms the PFAS molecule’s “Achilles’ heel” in the release.

In previous attempts to destroy PFAS, other researchers have used high temperatures—up to 400 degrees Celsius. The new technique, based on an inexpensive reagent and milder conditions, caused the carbon atoms to fall off two or three atoms at a time, the group discovered through further research using quantum mechanical models to better understand the chemistry of the process. Dichtel hopes their analysis will provide a key to others doing similar research.

“PFAS has become a major societal problem. Even just a tiny, tiny amount of PFAS causes negative health effects, and it does not break down. We can’t just wait out this problem. We wanted to use chemistry to address this problem and create a solution that the world can use. It’s exciting because of how simple—yet unrecognized—our solution is,” he says in the release.

PFAS are now deemed so unsafe that the U.S. Environmental Protection Agency (EPA) recently declared that they shouldn’t exist in drinking water at all. The form called PFOA must be brought down to virtually zero, the EPA advised on June 15 this year. Dichtel believes the new method could one day be scaled up to eliminate PFAS compounds categorized as carboxylates, if they are first effectively filtered from the water supply. Still, this method doesn’t work on other PFAS categories, such as sulfonates.

While this study successfully degraded ten perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl ether carboxylic acids (PFECAs), there’s a long way to go. The EPA estimates that 11,990 PFAS types are still out there.

Before joining Popular Mechanics, Manasee Wagh worked as a newspaper reporter, a science journalist, a tech writer, and a computer engineer. She’s always looking for ways to combine the three greatest joys in her life: science, travel, and food.

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