Hydrated Electron-Mediated Transformation of Per- and Polyfluoroalkyl Substances (PFAS): Role of Radical Anion Stability and Reactivity

Colorado School Of Mines, Golden CO

Investigators

Abstract

In this project, funded by the Environmental Chemical Sciences Program of the Chemistry Division, Professors Timothy Strathmann and Shubham Vyas are leading a team at the Colorado School of Mines that is advancing a promising photochemical destruction technology for per- and polyfluoroalkyl substances (PFAS) that have been identified as ubiquitous and highly persistent contaminants of the nation’s drinking water resources. Recent research has identified photochemically generated hydrated electrons as effective chemical reagents for attacking and destroying PFAS “Forever Chemical” pollutants. The goal of this research is to identify important steps in the underlying mechanisms responsible for PFAS decomposition and defluorination during reactions with hydrated electrons. The project lies at the interface of environmental chemistry and water quality engineering, and research is being integrated with education activities providing interdisciplinary training for graduate, undergraduate and K-12 students. Hydrated electrons are powerful reducing agents that can be generated by UV photoexcitation of appropriate sensitizers (e.g., sulfite and iodide ions). Although hydrated electrons reactions with a wide diversity of PFAS structures have been documented, critical discrepancies in our understanding of the underlying reaction mechanisms and pathways remain. The proposed research will probe the importance of fluoroalkyl acid radical anion species, which form upon the initial reaction between hydrated electrons and PFAS, in controlling the ultimate fate of the contaminants. Specific objectives of the project will include (1) establishing the relationship between rates for hydrated electrons decay and rates for transformation of different PFAS structures, (2) identifying molecular and water quality characteristics responsible for the shifting predominance of different PFAS transformation pathways, and (3) establishing a multi-step reaction network for predicting the fate of diverse PFAS structures during photochemical reactions with hydrated electrons. These objectives will be accomplished by combining constant irradiation experiments with high resolution mass spectrometry analyses along with laser spectroscopy and density functional theory calculations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.