Breaking Down “Forever Chemicals” New Solutions to the PFAS Problem

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PFAS are notoriously difficult to destroy, but new treatment approaches could weaken their most resilient bonds. Plasma and cavitation technologies are now being explored as potential tools for cleaning contaminated water more effectively.

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have developed two new processes: Using hydrodynamic cavitation and cold atmospheric plasma combined with gas dispersion, they are looking to break down per- and polyfluoroalkyl substances (PFAS), industrial chemicals that are extremely resistant to chemical degradation. To support this effort, experts from the Helmholtz Centre for Environmental Research (UFZ) ran analyses that confirmed the degradation of PFAS and the release of fluoride. Once they reach market maturity, these processes could be used in industry, significantly reducing the release of PFAS into bodies of water.

While some PFAS are suspected of altering genetic material and increasing the risk of cancer, the biological effects of many others remain unknown. This group of substances comprises more than 10,000 short- and long-chain industrial chemicals which owe their exceptional chemical resistance to their highly stable carbon-fluorine bonds. PFAS enter rivers and oceans via wastewater and are spreading worldwide. High concentrations of PFAS have also recently been detected in the Elbe River — a potential health hazard to plants, animals and humans alike.

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Cavitation Breaks Down Stable Bonds

“In hydrodynamic cavitation, we pass PFAS-enriched water through a constriction, generating small vapor bubbles,” explains Dr. Sebastian Reinecke, head of the Department of Water and Environmental Technologies at HZDR. Since long-chain PFAS are surface-active, they attach to the bubbles. “When the bubbles burst under the rising ambient pressure in the water downstream of the constriction, the PFAS that are attached to the bubbles are exposed to local temperature spikes of several thousand degrees Celsius,” Reinecke explains. At the same time, cavitation produces highly reactive hydroxyl radicals that react non-specifically with nearby substances. “Our hypothesis is that they attack the intermediate products, significantly boosting PFAS degradation.”

Ysabel Huaccallo-Aguilar and her colleagues were able to demonstrate that the process did break down PFAS in tap water while mineralizing organically bound fluorine. The longer the duration of the treatment, the higher the continuous increase in fluoride concentration in the solution. For their experiments, the researchers used perfluorooctane sulfonate (PFOS), a particularly persistent and well-studied compound from the PFAS group. By the end of the experiment, they were able to break down approximately 37 % of the dissolved PFOS molecules at a stable degradation rate. “We are now conducting follow-up experiments to increase the degradation rate,” Reinecke explains. “Our goal is to improve the process to a degradation rate of more than 80 % of the PFAS in the solution and mineralizing more than 50 % of the fluorine that is bound in the chemicals — that means, breaking down the carbon-fluorine bonds that are typical of PFAS.”

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Efficient PFAS Degradation with Highly Reactive Plasma Species

In another series of experiments, environmental engineer Dr. Amit Kumar used cold atmospheric plasma in combination with gas dispersion to degrade PFAS. The advantage of this process is that it operates under ambient conditions and requires neither catalysts nor additional chemicals. In his PhD research, Kumar had already investigated ways of degrading micropollutants using the reactive chemical species that are generated in the plasma. He now applied his findings to this experiment. “We generated plasma at the water surface while simultaneously introducing gas into the PFAS-contaminated water,” says Sebastian Reinecke, explaining the experimental setup. “The PFAS attach to the surface of the gas bubbles. As they rise, the water is constantly circulated. This brings the PFAS to the surface, where they are broken down in the plasma.”

This method made it possible to almost completely degrade both long- and short-chain PFAS. About 35 % of the fluorine atoms bound in these “forever chemicals” were released as fluoride salts. “While this method has significantly faster reaction kinetics than cavitation, it also consumes far more energy per volume unit,” Reinecke notes. “In addition, the process generates numerous transformation products that we have not yet been able to investigate in detail — for instance, gaseous compounds that form during the reaction.” The researchers are currently conducting further test series to find out whether the process produces any substances that may pose a health hazard, and if so, how to avoid it.

Synergies from Combining Plasma and Cavitation

The researchers are currently working to scale up the process for larger volumes of contaminated water. Using multiple electrodes and a technical gas injector, they are gradually increasing the reaction volume from about 50 milliliters to five liters. The plan is to combine plasma technology with cavitation. “I believe we’ll achieve high degradation rates by combining the highly reactive species from the plasma with the effects of cavitation,” says Reinecke. If they succeed in merging the benefits of both methods into a single approach, they might create a whole new, efficient PFAS removal technology for contaminated water.

Original Article: Enhanced degradation and defluorination of perfluorooctane sulfonate (PFOS) in tap water using gas-dispersed cold atmospheric plasma; Scientific Reports; DOI:10.1038/s41598-026-57490-6

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