• Professor Naresh Kumar.
    Professor Naresh Kumar.

Scientists at UNSW Sydney are developing catalysts able to break down PFAS chemicals that contaminate water.

Per-and poly-fluoroalkyl substances (PFAS) are known as ‘forever chemicals’ because they are notoriously resistant to degradation.

Due to their stable chemical structure, PFAS – which are found in thousands of variants – are used in oil and grease-resistant food packaging, non-stick cookware, cosmetics, clothing, and fire-fighting foams.

The chemicals are so widespread that they have infiltrated water sources and soil. In fact recent reports found that most global water resources exceed the drinking limits of PFAS and concerns over their environmental and health impacts have steadily escalated.

Despite ongoing efforts to develop ways of degrading PFAS, current methods are limited by a lack of efficient, scalable and environmentally friendly processes.

Now, a team of scientists from UNSW’s School of Chemistry have designed a catalyst system that can activate a reaction to break down common types of branched PFAS.

The new method, developed by Dr Jun Sun and Professor Naresh Kumar holds promise for more efficient and sustainable PFAS remediation in the future.

Working alongside Professor Denis O’Carroll, Professor Michael Manefield and Dr Matthew Lee from the UNSW School of Civil and Environmental Engineering, with a $3 million grant from the Australian Research Council in 2019, the team have designed a catalyst system that could play a key role in solving the problem of PFAS.

“Owing to its robust nature, simple application, and cost effectiveness, the new system we have developed shows successful PFAS remediation in the lab, which we hope to eventually test at a larger scale,” Dr Sun said.

Since the 1940s, PFAS chemicals have been produced on an industrial scale.

“In the time that PFAS was being produced globally, it wasn’t realised that this chemical is essentially non-destructible,” Kumar said.

The chemical is so resistant to degradation that people in Australia – and all over the world – are likely to have low levels of PFAS in their bodies.

PFAS is a fluorinated chemical bound by strong Carbon-Fluoride (C-F) bonds, which are famously hard to break. 

An existing method to remove PFAS from water and soil works by absorbing PFAS onto carbon material.

This is a laborious and energy inefficient process, not to mention the environmental impacts of burning carbon material. And while physical separation techniques such as this offer potential for isolating PFAS, they do not actually destroy the chemical, ultimately exacerbating the management challenges associated with PFAS-contaminated waste. 

Another method scientists have explored uses a strong oxidising agent to break it apart. However, this process requires aggressive chemicals that break PFAS down into smaller structures, that can become even harder to remove completely. 

“The method we have developed is a type of reductive defluorination, which decreases the toxicity of PFAS by breaking the strong C-F bonds of branched PFAS,” Dr Sun said.

Testing their method out on two common types of PFAS – branched PFOS and PFOA –Kumar and Dr Sun mixed the PFAS chemicals with nZVMs and the porphyrin ring in a buffer solution and measured the breakdown of the PFAS.

The results from this latest study revealed that within five hours, approximately 75 per cent of the fluoride had been released from branched PFOS and PFOA, significantly reducing the amount of PFAS within the solution.

“The next step for us is to really try this on a pilot scale to see if this can be done out of the laboratory on a real sample,” Kumar said.

“Then we’d like to try it out in a real water purification system or sites which are contaminated with PFAS.”