Researchers at the University of Bath have created ceramic-infused lattices (or ‘monoliths’), that can remove at least three-quarters of perfluorooctanoic acid (PFOA), one of the most common perfluoroalkyl and polyfluoroalkyl substances (PFAS), from water and could become an important tool in future efforts to eliminate the chemicals from water supplies.
Known as forever chemicals due to the incredibly long time they take to break down – in some cases more than 1,000 years – PFAS are man-made and known to cause health issues including damage to reproductive, developmental and cardiovascular systems, and an increase in the likelihood of developing diabetes. Sources of PFAS include domestic products, often with water-repellent properties, such as non-stick pans, raincoats, paints, fabrics and firefighting foams.
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‘PFAS, or “forever chemicals”, are a major focus in water treatment and public health, said Liana Zoumpouli, a research associate in Bath’s Department of Chemical Engineering and a member of the Centre for Digital, Manufacturing and Design. ‘We have created an efficient way to remove these chemicals from water without using lots of energy.
‘Using 3D printing to create the monoliths is relatively simple, and it also means the process should be scalable,’ she continued. ‘3D printing allows us to create objects with a high surface area, which is key to the process. Once the monoliths are ready, you simply drop them into the water and let them do their work. It’s very exciting and something we are keen to develop further and see in use.’
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While legislators around the world, particularly in the USA and EU, have brought in rules on acceptable levels of PFAS and similar chemicals in drinking water, the researchers say further legislation is likely as the scale of health threats comes into clearer focus.
‘Currently, these chemicals are not strongly regulated in the UK in drinking water, but there are guidelines, and we expect changes in policy quite soon,’ said Professor Davide Mattia. ‘Water companies are likely to be looking at integrating systems to deal with them.’
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Made of ink infused with the ceramic indium oxide, the four-centimetre monoliths are created by extruding the ink from a 3D printer – like squeezing toothpaste from a tube – and forming it into a lattice shape. Indium oxide bonds with PFAS, so the chemicals stick to the monoliths and can be removed from the water in under three hours, which is compatible with current water treatment plants in the UK and abroad.
While testing has so far found that the monoliths remove 75 per cent of PFAS from water, the team is aiming to increase the efficiency of the process with further refinement. Testing of the monoliths has surprisingly shown that they have become more effective under repeated use – they undergo high-temperature thermal ‘regeneration’ treatment after each use. This is something the researchers are keen to understand more fully with further experimentation.
The research has been published in the Chemical Engineering Journal.