Kill it with fire: CSU researchers seek solution for pervasive PFAS pollutants

photo of an incinerator in Ohio
An incinerator in East Liverpool, Ohio, burns PFAS-containing material under contract with the U.S. Department of Defense. Credit: Center for Land Use Interpretation/Creative Commons

PFAS are everywhere. Per- and polyfluoroalkyl substances, known as PFAS, can be found in food packaging, cleaning products, electronics, nonstick cookware, water-repellant clothing and firefighting foams – to name a few. Unfortunately, they also can be found in our food and water, and have been linked to adverse health effects.

PFAS are a family of thousands of human-made chemicals. Two of the most extensively produced and studied of these compounds, PFOA and PFOS, are no longer manufactured in the United States. Now CSU scientists are trying to figure out how to clean them up.

CSU researchers Jens Blotevogel and Anthony Rappé recently received a $474,000 U.S. Department of Defense grant to study and improve the incineration process, so PFAS can be permanently removed from the environment without producing hazardous byproducts.

PFAS’ signature carbon-fluorine chemical bond is among the strongest in nature and makes these substances nearly impossible to destroy, giving them their nickname, “forever chemicals.” Scientists are trying to develop alternative destructive treatment technologies, but incineration is currently the only large-scale method that can break down these compounds completely.

“These compounds are in so many products, and they are very mobile in the environment,” said Blotevogel, co-principal investigator on the project and research assistant professor in the Department of Civil and Environmental Engineering. “You can find them in highly industrial areas, but you can also find them in polar bear tissues, thousands of miles from where they have ever been used.”

Blotevogel and others have developed effective means of removing PFAS from water, through membrane filtration, ion exchange or adsorption to activated carbon. These methods clean the water but produce concentrated waste streams that often are discarded in landfills, transferring the problem from one environmental compartment to another.

“At the moment, the only large-scale technology that can destroy these compounds is incineration, whether we like it or not,” Blotevogel said.

There are several reasons to dislike it.

As with any treatment method, there’s always a small amount of contaminant that escapes. Elevated levels of PFAS have been found in soil surrounding incinerators, and incineration leaves behind residual ash material.

“That just means we have to do an appropriate job of running these incinerators under the right conditions to ensure that people are safe,” Blotevogel said.

One model, thousands of solutions

Blotevogel and co-principal investigator Rappé, a professor in the Department of Chemistry, will determine optimal incineration conditions, including how long and at what temperatures PFAS need to burn to break down completely. Understanding these details will yield environmental and health benefits as well as cost savings.

Because there are thousands of PFAS, figuring out the specific conditions needed to destroy each compound is an enormous undertaking. Blotevogel and Rappé plan to develop a predictive model that can be applied to any compound in the PFAS family.

Graphic overview of the research approach, details in story
Conceptual overview of the research approach Blotevogel and Rappé will use in this DoD-funded project.

They will use computational chemistry based on quantum mechanics to predict the PFAS’ thermal decomposition, then use machine learning to speed up their model. They will share their findings with other DoD-funded researchers conducting physical incineration experiments, to see if their calculations align with observations.

Blotevogel and Rappé’s model will expand on small-scale lab experiments, projecting outcomes based on the conditions of full-scale incineration. It also will identify any products of incomplete combustion that are formed when a compound doesn’t fully break down.

These intermediate compounds can sometimes be more toxic than the original compound. Their findings will guide analytical chemists, who can then target these specific intermediates, instead of blindly searching for thousands of compounds.

While incineration may not be ideal, the researchers and the DoD agree that something must be done about PFAS. Developing this new predictive model is an important step to ensuring these difficult contaminants are eliminated efficiently and effectively.

“You need to get rid of it; you can’t just build it up,” Rappé said. “Hopefully we’ll contribute to making sure the process is clean.”