Contamination of ground, surface and drinking water by perfluoroalkyl and polyfluoroalkyl substances (PFAS) affects millions of people worldwide.
A promising new method developed by Flinders University scientists paves the way to help remove the most difficult-to-capture variants of these persistent pollutants from water.
The research team, led by Flinders ARC Research Fellow Dr Witold Bloch, has discovered adsorbents that effectively capture PFAS, including short-chain forms that are especially difficult to remove using existing technologies.
The study, published in the top-tier journal Angewandte Chemie International Edition, showcases the use of a nano-sized molecular cage that acts as a highly selective 'PFAS trap'.
"While some long-chain PFAS can be partially removed using existing water treatment technologies, the capture of short-chain PFAS – which are more mobile in water – remains a major unresolved challenge," says project leader Dr Witold Bloch, from Flinders University's College of Science and Engineering.
"We discovered that a nano-sized cage captures short-chain PFAS by forcing them to aggregate favourably inside its cavity. This unusually strong binding mechanism is different from that of traditional adsorbent materials."
The team embedded these molecular cages into mesoporous silica – an adsorbent that normally shows no PFAS binding properties.
First author Caroline Andersson, a PhD candidate in chemistry at Flinders University, says the presence of the embedded nanosized cage enables a broad range of PFAS to be removed from water, including short-chain variants that are notoriously difficult to isolate.
"The most exciting aspect of this project was that we first conducted in-depth studies of how PFAS bind within the cage on the molecular level," she says. "That allowed us to understand the precise binding behaviour and then use that knowledge to design an effective adsorbent for PFAS removal."
Laboratory testing showed the adsorbent material can remove up to 98% of PFAS at environmentally relevant concentrations in model tap water.
"The adsorbent also demonstrated reusability, remaining highly effective after at least five cycles of reuse. These results highlight its potential for integration into water filtration systems for polishing drinking water at the final stage of treatment," adds Dr Bloch.
"This research represents an important step toward the development of advanced materials capable of tackling one of the world's most persistent environmental contaminants," he concludes.
PFAS molecules from industrial manufacturing, aviation firefighting foam and consumer products, which find their way into fresh water as well as marine environments are creating growing concerns about health risks to humans, livestock and wildlife.
