Researchers at Flinders University in Australia report a new adsorbent material that removes up to 98% of per- and polyfluoroalkyl substances (PFAS) from water, including the short-chain compounds that conventional treatment technologies struggle to capture. The study was published in Angewandte Chemie International Edition.
The work, led by ARC Research Fellow Dr. Witold M. Bloch combines two materials in a "host-in-host" design: a nano-sized molecular cage doped at roughly 1 wt% into mesoporous silica (60 Å pore size). On its own, the silica does not bind PFAS; the embedded cages provide the selective trap.
According to the authors, PFAS molecules enter the cavity of the cage through anion exchange, and their fluoroalkyl tails then aggregate cooperatively inside the cavity. The team characterised this mechanism using spectroscopic measurements and X-ray crystallography, which they say differs from the binding behaviour of conventional adsorbents such as activated carbon or ion-exchange resins.
"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," Bloch said in a press release published by Flinders University. "We discovered that a nano-sized cage captures short-chain PFAS by forcing them to aggregate favourably inside its cavity."
Andersson said the project began with molecular-level binding studies before the team moved to a practical adsorbent. "That allowed us to understand the precise binding behaviour and then use that knowledge to design an effective adsorbent for PFAS removal," she said.
Performance in laboratory tests
In flow-through experiments using model tap water at environmentally relevant concentrations, the material removed more than 98% of both short- and long-chain PFAS, with high selectivity over common water-borne anions. The authors also report that the adsorbent remained effective after at least five cycles of regeneration and reuse.
Bloch described the material as a candidate for "polishing" drinking water at the final stage of treatment rather than as a stand-alone replacement for existing infrastructure.
PFAS are a large family of synthetic chemicals used in products ranging from firefighting foams to non-stick coatings and water-repellent textiles. Their carbon-fluorine bonds make them extremely persistent in the environment — the origin of the "forever chemicals" label — and short-chain variants, developed in part as replacements for phased-out long-chain compounds, are particularly difficult to remove from water because of their higher mobility.
The Flinders study is a laboratory-scale demonstration. The authors have not reported pilot-scale or field trials, and the economics of producing the molecular cage at volumes relevant to municipal or industrial water treatment are not addressed in the paper.
