It is known that PFAS, often referred to as “permanent chemicals“, persist in the environment and in our bodies.
PFAS are a class of about 12,000 synthetic chemicals that have been widely used since the 1940s in a variety of products, from nonstick cookware to waterproof makeup and from electronics to food packaging.
Chemists at Osaka Metropolitan University could eradicate PFAS”forever” thanks to a simple but innovative technology that converts these toxic substances into valuable compounds.
A research team led by Professor Masato Ohashi and Associate Professor Kenichi Michigami from the Graduate School of Science at Osaka Metropolitan University succeeded in synthesizing the so-called fluorine-decorated N-heterocyclic carbenes (NHCs) from perfluoroalkenes, a type of PFAS (perfluoroalkyl and polyfluoroalkyl substances).
The NHC developed in this study plays an important role in stabilizing unstable molecules as well as improving the performance of related transition metal complexes.
The synthesis of fluorinated NHC was achieved by removing two fluorine atoms from the 1,2-difluoroalkene derivative. Due to the small size of the fluorine atoms, the electron-accepting capacity of the NHC ligand can be improved without significantly changing its steric properties.
“Our results facilitate the conversion of harmful PFAS into functional NHC“explains Dr. Michigami. ““The versatile use of NHC fluoride shows potential advantages in various fields such as fluorine chemistry, organometallic chemistry, catalytic chemistry and materials science.”
The results of his research on permanent chemicals were published in the Journal of the American Chemical Society.
Background to permanent chemical eradication
“Over the past 70 years, PFAS have contaminated virtually every drop of water on the planet, and their strong carbon-fluorine bond allows them to pass through most water treatment systems completely unscathed.explains a team of scientists from the University of California, Los Angeles and Northwestern University in the United States.
American chemists will finally propose a solution to what to do with these stubborn pollutants in 2022: Once water is heated to 80 to 120 degrees Celsius, common solvents and reagents can damage the molecular bonds in permanent chemicals, they explain.
“Decarboxylation in non-protic polar solvents produces a carbanion that rapidly decomposes (through a process that involves removal of fluoride, addition of hydroxide, and cleavage of the carbon-carbon bond).”
The discovery followed an observation by William Dichel, a professor of chemistry at Northwestern University, and Brittany Trang, a graduate student, who found that although PFAS molecules contain a long “tail” of carbon-fluorine bonds, they are insensitive to the forces of nature remain. , its “head” group often contains charged oxygen atoms that react strongly with other molecules.
So scientists set out to build a “chemical guillotine” by heating PFAS in water with dimethyl sulfoxide and sodium hydroxide, cutting off the head and leaving an exposed reactive tail.
“That triggered all these reactions and started ejecting fluorine atoms from these compounds to form fluoride, the safest form of fluorine,” Dichel says. “Although the carbon-fluorine bonds are super strong, this charged head group is the Achilles’ heel.”
Scientists have already managed to break down 10 types of perfluoroalkylcarboxylic acids (PFCA) and perfluoroalkyl ethercarboxylic acids (PFECA), including perfluorooctanoic acid (PFOA).
The new method will work for most permanent chemicals that contain carboxylic acids, they say. Hopefully it will also help identify vulnerabilities in other classes of PFAS.
Despite the encouraging results, however, more research needs to be done to determine how best to eliminate the thousands of other types of PFAS. But perhaps we will soon have a method by which we can banish these harmful chemicals from nature forever.
With information from: