Analysis of Thermal Degradation Pathways of per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are a group of highly stable molecules comprised of a long carbon chain with fluorines around them. These molecules are known for their ability to bioaccumulate in wildlife, humans, and pollute water sources, causing severe health effects like cancer, immune system suppression, liver failure, and kidney damage. PFAS compounds are found in several everyday products, like cookware and waterproof containers. The EPA has set a strict limit on the levels of Perfluorooctanoic acid (PFOA), one of the more common PFAS molecules, at 4 ppt. Due to the strict limit and range in concentration found in varying water sources, a preconcentration step is required before degradation can take place. This has been initially investigated through the use of zeolite, resulting in about > 90% absorption from an initial concentration of 10ppm. Further understanding of this compound has led the team to investigate the degradation pathway of PFOA to close out the fluorine mass balance. This investigation will look into how different PFAS molecules break down via thermal degradation at 900°C in a nitrogen rich environment while using Zeolite as the sorbent material. During the design process of the thermal system, the team encountered several leaks due to the pressure build up in the bubbling tanks. This issue was further complicated as the majority of commercial thread sealant products are manufactured with fluorinated compounds. A solution was found by taking rubber sheets and cutting them into custom fit rubber gaskets. These tests will be performed on fluorinated compounds ranging from C8 – C4. After the thermal system has degraded the PFAS compound LCMS / MS will be used to acquire a quantitative analysis of the degradation compounds. In the future, this system will then be optimized to then acquire qualitative data. These results will be used as the baseline for the development of Electric Cell-substrate Impedance Sensing (ECIS) methodology that will aid in understanding the in-vitro cellular toxicity of the degradation products. ECIS technology is a system that measures electrical impedance over cells in a culture. Electrical impedance increases when cells are attached to the electrodes, and impedance drops as cells die due to an introduced toxin. This will allow the team to gain a better understanding of the biological impact of PFAS molecules and their subsequent products after degradation has occurred.