Researchers from the University of Bath have developed 3D printed structures that can remove harmful ‘forever chemicals’ from water.
The ceramic-infused lattices (or ‘monoliths’) can reportedly remove up to 75% of perfluorooctanoic acid (PFOA) in under three hours. This is said to offer an efficient and scalable solution to the presence of dangerous chemicals in global water supplies.
PFOA is one of the most common perfluoroalkyl and polyfluoroalkyl substances (PFAS). These man-made forever chemicals can take up to 1,000 years to break down naturally and are toxic to humans.
PFAS’ have been linked to decreased fertility, hormonal changes, liver damage, cardiovascular problems, diabetes, and cancer. They are persistent in the environment and human bodies, being found in many domestic products such as non-stick pans, raincoats, paints, fabrics and firefighting foams.
Published in The Chemical Engineering Journal, the research team called the study a “significant step” in developing an efficient solution to the environmental contamination of the chemicals. They added that the 3D printing-based method offers an “environmentally sustainable and effective solution for PFAS remediation.”
Removing ‘forever chemicals’ with 3D printing
According to Dr Liana Zoumpouli, a Research Associate in Bath’s Department of Chemical Engineering, forever chemicals are a major cause for concern in water treatment and public health.
Co-author Professor Davide Mattia added that these chemicals are not currently heavily regulated in drinking water in the UK. However, he expects to see policy changes quite soon, with water companies likely to look for integrated systems to remove them.
The University of Bath team views their 3D printed monoliths as an ideal solution to this problem. Zoumpouli calls the approach “an efficient way to remove these chemicals from water without using lots of energy.”
The research team fabricated their 4cm-tall monoliths on a VormVrij Lutum 5 extrusion-based clay 3D printer using a specially developed ink infused with ceramic indium oxide. This material naturally bonds with PFAS, allowing a high proportion of the harmful chemicals to be trapped in the lattice structures and and removed from water.
The monoliths featured a cylindrical scaffold geometry designed to maximize the surface area and improve the absorption of the chemicals. During testing, the production process was tweaked with different sizes, flow rates and sintering temperatures assessed. Once the ideal combination was found, the team achieved 67% PFOA absorption and a high absorption capacity of 0.14 mg L-1.
Interestingly, the monoliths became more effective after repeated use, as they could undergo ‘regeneration’ through a thermal heat treatment process. This extends the lifecycle of the 3D printed devices, improving their sustainability.
Subjecting monoliths to a low-temperature pyrolysis process at 500°C allowed them to be used in three absorption cycles, extending the removal of PFOA to 75% in just 3 hours. The heat-treated structures required a much shorter time to reach optimal absorption levels.
The team’s reusable and easy-to-handle lattice structures reportedly eliminate the expensive downstream removal of alternative slurry-based adsorbents. They are therefore said to offer a “clear route for scale-up towards industrial use.”
Looking to the future, the researchers will work to refine the efficiency of the lattices. They are reportedly keen to build a greater understanding of the regeneration process through further experimentation.
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3D printed devices tackle water pollution
This is not the first time 3D printing has been leveraged to improve water quality. Back in 2018, Singapore-based sustainability firm Nano Sun began 3D printing water-filtering membranes to reduce water pollution. 3D printing the devices is said to be five times more efficient than using traditional production processes.
Through its dedicated manufacturing plant, Nano Sun has the capacity to 3D print approximately 600 sq m of membranes every day. These are used by industrial enterprises to remove pollutants from waste water. Early adopters include two large multinational semiconductor enterprises based in Singapore. A waste water plant in China, which can process 20 million litres of water per day, also uses the 3D printed membranes.
Elsewhere, a team of researchers from pharmaceutical 3D printing specialist FabRx, University College London and Universidade de Santiago de Compostela (USC) developed a 3D printed device capable of removing drugs from water.
The reusable biocatalytic device, called Printzyme, features customizable morphology. It leverages natural enzyme laccase as a drug oxidating agent, capable of degrading a wide range of pharmaceuticals.
The team tested the device using two model drugs found on the European water pollution watch list, diclofenac and ethinylestradiol. Printzyme successfully reduced the concentration of both drugs within the solution. It removed over 80 percent of dissolved diclofenac within 24 hours, and 95 percent of ethinylestradiol within just two hours.
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Featured image shows the 3D printed ceramic monoliths. Photo via the University of Bath.
