Utah researchers sever PFAS bonds with mild heat

Researchers at the University of Utah have developed a chemical method to break down per- and polyfluoroalkyl substances, or PFAS, at temperatures as low as 110 degrees Celsius. The process, published on Oct. 28 in the journal Communications Chemistry, uses reactive chemicals called nucleophiles to sever the strong carbon-fluorine bonds that make these pollutants persistent in the environment. This approach offers a potential alternative to incineration, which typically requires temperatures of 1,000 degrees Celsius or higher.

PFAS are a class of water pollutants known for their severe long-lasting effects on public health and the environment. While they have beneficial industrial uses, their chemical stability makes them difficult to destroy. Previous efforts by the research team focused on removing these chemicals from water through filtration and adsorption. This new study addresses the next step in the cleanup process, which is destroying the chemicals after they have been collected in filtration materials.

Ling Zang, a distinguished professor in the Department of Materials Science and Engineering at the John and Marcia Price College of Engineering, led the industry-funded study. She serves as associate dean for research at the college. Zang stated that the ultimate goal is to destroy and detoxify PFAS to reduce their hazards. She noted that cleanup efforts must prevent contamination from simply moving from water into another waste stream.

The research team tested the defluorination method on several compounds, including PFOA and trifluoroacetic acid, known as TFA. TFA is a particularly stubborn small molecule. The process released nearly all of the fluorine from these compounds as fluoride. The team also applied the method to two fluorinated plastics, PVDF and PCTFE, which are commonly used in batteries, industrial products, and munitions. The method achieved efficient fluorine removal from these materials as well.

Most tests were conducted at 110 degrees Celsius, or 230 degrees Fahrenheit. Some materials required temperatures up to 150 degrees Celsius. These temperatures are substantially lower than those used in incineration. Incineration presents challenges because incomplete breakdown can produce secondary pollutants, including smaller fluorinated compounds. Some of these byproducts are more volatile than the original chemicals and can disperse through the atmosphere.

The reported method works in ordinary air. It does not require specialized conditions such as inert gas atmospheres, deep-ultraviolet irradiation, or highly reactive alkali metals. It also avoids the need for heavy-metal catalysts, externally applied high pressure, or energy-intensive mechanical processing. The approach could eventually allow PFAS to be captured from contaminated water, concentrated into a smaller waste stream, and destroyed.

The research remains at the laboratory stage. Future studies will explore alternative reagents and reaction conditions to improve effectiveness and reduce environmental impact. The researchers also plan to evaluate the method using real waste streams, assess treatment costs, and determine the safety of the remaining products. Co-authors include Pallabita Basu, Saravanakumar Manickam, Rana Dalapati, Jiangfan Shi, Matthew Hunter, and Xiaomei Yang.

Funding for the study came from Gentex Corp., where Zang sits on the board of directors. Zang and two of the co-authors are listed as inventors on patent applications filed by the University of Utah in connection with the process. The study title is “Nucleophilic Defluorination of PFAS under Mild Conditions.”