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PFAS: Chemists can break down indestructible pollutants after all


They are everywhere, they cause enormous damage, they accumulate in nature: there seemed to be no cure for perfluorinated and polyfluorinated alkyl compounds. But now chemists have found a simple method.

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Environmental toxin against environmental toxin: PFOS-containing extinguishing foam after a tanker fire in the USA

Photo: ZUMA Press / IMAGO

Chemists at Northwestern University have "done what seemed impossible," the US university cheered.

According to a study published this Friday in the scientific journal Science, the team has developed an amazingly simple method for dissolving the per- and polyfluorided alkyl compounds (PFAS) feared as “forever chemicals” into harmless products.

PFAS are industrially manufactured substances that repel water and grease and withstand different temperatures.

These properties have proven useful in products such as non-stick coatings for cookware, waterproof yet breathable functional clothing, waterproof cosmetics or fire-fighting foam.

The downside: bacteria can damage the strong compounds just as little as fire or water, and the chemicals accumulate in nature and stay there practically forever.

And: It is now clear that PFAS, even in tiny amounts, can be extremely harmful to health.

They are thought to be the cause of several different types of cancer, hormone disorders and birth defects.

"PFAS have become a huge societal problem," said Northwestern chemistry professor William Dichtel.

The toxins are in a league with lead.

Lots of failed approaches

PFAS are therefore now avoided in most new products, and some compounds are outlawed under the Stockholm Convention and banned in the EU, for example.

The US Environmental Protection Agency (EPA) recently set the limit to zero in most cases.

But what about the residues of the pollutants that have already been produced, which are constantly spreading?

PFAS have already been detected in the drinking water and blood of most US citizens, in Germany in mother's milk and in the liver of polar bears in the Arctic.

According to a new Swiss study, rainwater would be considered undrinkable worldwide because of the PFAS concentration.

While the compounds are successfully filtered out of drinking water, the toxic waste has so far had no viable use.

The connections can be destroyed with high temperatures of up to 400 degrees Celsius or very high pressure, but Dichtel sees only failed approaches: Some of the pollutants escaped from an incinerator in New York State, "through the chimney into the surrounding communities".

In addition, the energy consumption is extreme.

Putting the PFAS in landfills "only guarantees that in 30 years you're going to have a problem because the compounds are starting to seep into the ground."

Under the direction of Dichtel, a team led by doctoral student Brittany Trang has finally found a method through experimentation, which it presents to the world as a simple solution.

Instead of attacking the extremely strong bonds between carbon and fluorine atoms caused by mutual electrical attraction, of which there are several in every PFAS molecule, the researchers targeted what they call the “Achilles heel”: a head group of oxygen and hydrogen atoms .

Under mild heat of 80 to 120 degrees Celsius, this head gave way in the solvent dimethyl sulfoxide in reaction with sodium hydroxide, and then - several atoms at a time - the chain of fluorine and carbon also disintegrated.

According to Dichtel, only harmless substances remained, and that with a cheap and simple, previously undiscovered method.

The experiments were confirmed in cooperation with the University of California at Los Angeles and the Chinese University of Tianjin.

Quantum computers were used in China to analyze the decay process.

To date, the process has been applied to ten out of more than 12,000 different known PFAS compounds.

Dichtel's team now wants to take care of the rest.


Source: spiegel

All tech articles on 2022-08-19

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