CHAMPAIGN – A class of synthetic chemicals, commonly referred to as PFAS, have raised concerns because of their link to cancers and other illnesses and their environmental persistence. University of Illinois Urbana-Champaign scientists are working on developing new approaches to removing these “forever chemicals” from the environment.
The researchers have developed a prototype of an electrochemical device that can capture, concentrate and destroy per- and polyfluoroalkyl substances in a single process. The work was published in Nature Communications.
PFAS are human-made chemicals used in products including nonstick pans, fire extinguishing foam and cosmetics. PFAS are also used extensively in semiconductor manufacturing. The molecules are highly stable, making them hard to break down once they enter the environment, leading to water and soil contamination and long-term health concerns in wildlife and humans.
“They have unique properties that make them very valuable, but they also are very hard to degrade in the environment,” said Xiao Su, a UIUC associate professor of chemical and biomolecular engineering, who led the development of this new technology. “That’s why there is all this attention for PFAS as contaminants. There’s a lot of regulations coming or already in place for PFAS and drinking water, so in general we just want to find better ways to remove and degrade them.”
PFAS molecules are polymers that come in a variety of sizes, pertaining to the length of their chains. A previous U of I study demonstrated that both short- and long-chain PFAS can be removed from water using electrosorption, a process where ions or molecules are attracted and bound to the surface of a material using an electric field.
Su said there are challenges when it comes to using electrosorption due to the variability in size of PFAS molecules. Long chain and ulta-short chain PFAS have dramatically different contaminant properties, he said, so they require different separation methods for removal.
“Developing an electrochemical method that could target both the ultra-short, but all the way to the long chain, is something that we wanted to address,” Su said.
To do that, he and colleagues combined two methods. The first uses electrosorption alongside a technique known as redox electrodialysis. Electrosorption uses electrodes to attract and bind contaminants and electrodialysis uses membranes to separate charged ions. The former works well for long-chain PFAS and the latter works better for ultra-short PFAS, Su said. Both techniques, he noted, are combined in the device to create a more versatile and efficient system for PFAS removal.
After PFAS are removed from water samples, they are destroyed by to electrochemical oxidation, which uses electrodes to remove electrons, converting PFAS into fluoride ions and carbon dioxide molecules that are nontoxic and more friendly for the environment, Su said.
John Scott, a senior chemist at the Illinois Sustainable Technology Center who was not involved in the study, has done separate research concerning PFAS. He said the buzz around PFAS is overblown.
“There’s a lot of other pollutants that are already out there that we know of that are much higher concentrations, but nobody seems to get hot and bothered about that,” Scott said.
He cited poly-aromatic hydrocarbons, a group of organic compounds primarily formed through the incomplete combustion of organic materials, such as fossil fuels, tobacco and wood. He said that these compounds are known to be carcinogenic, and they are found in concentrations much higher than PFAS in soils.
While Scott believes that research into PFAS is still worthwhile, he believes researchers should be careful about how much they invest into this area of research.
Su said the work is important because of PFAS’ danger as a contaminant. Traditional technologies for PFAS removal can use a lot of energy or require a lot of chemical consumption, and he said there are benefits to this new technology in addition to its ability to accommodate PFAS’ size spectrum.
“Electrochemical separations, in general, have this big opportunity to actually come in and make a lot of separations more sustainable, and also more modular as well,” Su said.
The research team is looking forward to scaling up their prototypes to be used in real-world settings outside of the lab, he said.