Soil and water impacted with per- and polyfluoroalkyl substances (PFAS) necessitates the development of effective and safe remediation technologies. Conventional methods struggle to eliminate these refractory anthropogenic compounds. The primary objective of this project is to integrate experimental data with theoretical insights to gain a mechanistic and predictive understanding of the directly and indirectly controlled process parameters governing the pathways and kinetics of thermal PFAS decomposition. The main outcome of this work will be an improved fundamental understanding of PFAS incineration and the development of a model to optimize the destruction and removal efficiency (DRE) of the process while minimizing the formation of products of incomplete destruction.

Task 1 will focus on the impacts of directly controlled parameters on PFAS decomposition pathways and kinetics. To enable a mechanistic understanding of a significant number of variables such as temperature, oxygen, hydrocarbon fuel, and PFAS concentrations, the project will focus the initial investigations on a small, targeted number of PFAS.

In Task 2, the project will explore the effects of indirectly controlled parameters, including sodium, silica, and organic matter as soil components, polyethoxylate surfactants as aqueous film-forming foam (AFFF) components, calcium, and chlorinated solvents as co-occurring chemicals.

In Task 3, the project will explore the evolution of intermediates and kinetic bottlenecks during thermal destruction of selected representative PFAS using molecular-beam mass spectrometer and highest-level computational modeling, and will determine the impacts of varying functional headgroups, chain length, hydrogen atom content, etc.

Successively, Task 4 will address the compositionally complex PFAS such as AFFF and/or original PFAS-impacted waste samples based on the mechanistic framework and kinetic parameters acquired from previous tasks. Finally, the project team will build on the experimental measurements and theoretical analysis for the thermal decomposition of perfluorooctane sulfonic acid, and this model will form the basis for other fluorochemical feedstocks, eventually AFFF.

The intended impact and benefit of the present research is to provide the chemical reaction insights needed to underpin technology developed specifically to destroy PFAS in impacted materials, and in doing so, to reduce both the environmental impact of these chemicals and the associated liabilities. The analysis will lead to estimation of controlling parameters for each elementary reaction step, which will be based on theoretical analysis and experiments. Ultimately, the insights gained in this study will be the foundation for optimizing DREs on the path to cost-efficient and safe destruction of these persistent chemicals. (Anticipated Project Completion - 2027)