Scientists in the UK have developed a new method for removing toxic “persistent chemicals” from wastewater. Specially treated, 3D-printed ceramic cages can remove up to 75% of chemicals from contaminated water in three hours, and the structures get better at their job the more they are reused.
One of the most pressing environmental and health concerns today is a group of chemicals known as perfluoroalkyl and polyfluoroalkyl substances (PFAS). Their widespread use for more than a century has spread these chemicals across the planet and they do not break down, leading to the nickname “forever chemicals.” They inevitably enter our bodies, where they are linked to a variety of health problems, from diabetes to various cancers.
Now, scientists at the University of Bath have shown a new potential way to remove PFAS from water. The idea is to use 3D-printed “monoliths” made from ceramic materials infused with indium oxide, which bonds with PFAS molecules. These monoliths can be left in dirty water for a few hours, and when they are removed, the PFAS goes with them. They can then be processed to remove the chemicals and allow the monoliths to be reused.
While many 3D-printed structures require fine detail, these are made from much thicker “noodle” materials, like toothpaste squeezed from a tube, into a structure that looks like a stack of waffles. The goal of this is not only to simplify manufacturing, but also to maximize surface area to allow them to capture as much PFAS as possible.
In tests, these monoliths were initially able to remove 53% of a common PFAS called perfluorooctanoic acid (PFOA) from water in three hours. The pyrolysis process of the monoliths at 500°C (932°F) regenerated them and allowed them to be used again—and interestingly, this actually increased their ability to clean water. By the third cycle, the monoliths were removing 75% of the PFOA in three hours.
While there is still more work to be done, the team says that adding these reusable ceramic monolith arrays to existing wastewater treatment plants could be a valuable step. Unlike other techniques that require catalysis, the process itself does not require energy – although regenerating them through pyrolysis could be a challenge.
“Using 3D printing to create monoliths is relatively simple and also means the process should be scalable,” said Dr. Liana Zoumpouli, one of the authors of the study. “3D printing allows us to create objects with a high surface area, which is key to the process. Once the monoliths are ready, you drop them in water and let them do their thing. It's very exciting and something we want to develop further and see in use.”
The research was published Journal of Chemical Engineering.
Source: University of Bath