ETH develops new method for breaking down perpetual chemicals

Researchers at the Swiss Federal Institute of Technology in Zurich (ETH) have developed a new process to break down a subgroup of harmful per- and polyfluorinated alkyl compounds (PFAS). These are perfluorooctane sulfonates (PFOS), a group of extremely stable and toxic substances. According to a press release, so-called piezocatalysis using nanoparticles and ultrasound could offer an effective alternative to existing processes in the future. However, these have so far been very costly or energy-intensive. The new method shows promising results in the laboratory, as more than 90 percent of the PFOS molecules were decomposed in the tests.

Chemicals that are extremely stable and therefore have an impregnating effect or are heat-resistant are very popular in terms of their usability. However, so-called PFAS and their subgroup PFOS are released into the environment via landfills or industrial wastewater after use without being degraded. Such harmful substances can also be detected in human blood, where they can cause cancer, among other things. According to the researchers led by Salvador Pané i Vidal, Professor at the Institute of Robotics and Intelligent Systems at ETH Zurich, current methods for breaking down these stable compounds are inadequate. The team therefore wanted to find a new way to break down PFAS.

"The main problem is that the molecules consist of long carbon chains surrounded by fluorine atoms. This carbon-fluorine bond is so strong that you need a lot of energy to break it," says Andrea Veciana, PhD student at Pané i Vidal. The researchers used piezocatalysis for the first time to break down the PFOS molecules. "We have developed nanomaterials that are piezoelectric," says Veciana. In an ultrasonic bath, the particles become electrically charged and act as a catalyst. The electrical charge then sets off a chain of reactions that break down the PFOS molecules piece by piece. So far, this has been achieved in the laboratory with water samples of 50 milliliters. "The scalability of our method is one of the biggest challenges," adds Pané i Vidal. However, the researchers are confident and also see potential in the technology for the entire spectrum of PFAS. ce/eb