An Australian-led team of international scientists have shown how per- and polyfluoroalkyl substances (PFAS) can be safely destroyed by burning them.
Theirs is the first study to trace the entire chain of chemical reactions as PFAS break down during incineration.
Global concern around PFAS contamination is mounting because these "forever chemicals" persist and accumulate in the environment, causing significant harm to human and animal health.
There is currently a moratorium on burning PFAS in the United States, and regulatory uncertainty elsewhere.
This is because improper incineration does not completely destroy them, and risks spreading them further through the air. It also creates harmful greenhouse gas emissions.
Now, researchers from Australia's national science agency, CSIRO, the University of Newcastle, Colorado State University and the National Synchrotron Radiation Laboratory in Hefei, China, have defined a pathway for PFAS to be destroyed safely and completely, inside a hazardous waste incinerator.
CSIRO Environmental Chemist and study co-author, Dr Wenchao Lu, explained how the interdisciplinary team studied a common type of PFAS called perfluorohexanoic acid.
"There are over 15,000 types of PFAS, but all of them share a strong fluorocarbon chain which doesn't break down naturally," Dr Lu said.
"This is what makes them so persistent in our environments."
Some of the chemicals formed during PFAS incineration exist for just 1 millisecond: shorter than a housefly's wing flap. But identifying these intermediary molecules is crucial to determining what harmful products are formed throughout the process.
Researchers ionised then detected the different molecules created as the PFAS was burned. Using specialised equipment at the National Synchrotron Radiation Laboratory, the researchers detected the short-lived molecules, created as the PFAS burned.
"By taking 'snapshots' of the chemical reactions as they occur, we can see what intermediaries or harmful free radicals form inside the incinerator," Dr Lu said.
"These chemicals had been hypothesised, but never actually detected."
Co-author from the University of Newcastle, Professor Eric Kennedy, said their results shed light on how PFAS can be safely destroyed at high temperatures.
"This study has identified intermediary molecules that are critical for us to ensure the PFAS molecule is completely destroyed, and to ensure no harmful byproducts are formed," he said.
Co-author from Colorado State University, Professor Anthony Rappé, said: "This international team effort is illustrative of the collaborative environmental work that CSIRO leads."
The ultimate goal of incinerating PFAS is a process called 'mineralisation'. This converts the strong fluorocarbon chains into inorganic compounds like calcium fluoride, carbon dioxide, carbon monoxide, and water.
These byproducts can, in turn, be captured at the source and transformed into reusable materials such as industrial chemicals, concrete, fertilisers and fuels.
While further research is needed, these insights offer a promising option for destroying PFAS safely, and for good.
PFAS occur in a range of consumer, industrial, and commercial products, such as non-stick food packaging and cookware, and legacy firefighting foams.
The chemicals can leach into soils and groundwater, travel long distances, and do not fully break down naturally, giving them their moniker of "forever chemicals".
The research paper, ' Direct Measurement of Fluorocarbon Radicals in Thermal Destruction of Perfluorohexanoic Acid Using Photoionization Mass Spectrometry ', was published in Science Advances.
