Optimizing Environmental Perfluoroalkyl Acid Degradation by Elucidating Mechanisms: A Coupled Computational and Experimental Approach

Colorado School Of Mines, Golden CO

Investigators

Abstract

This project is funded by the Environmental Chemical Sciences Program in the Chemistry Division at the National Science Foundation. Prof. Professor Shubham Vyas and his students investigate the mechanisms by which perfluoroalkyl acids (PFAAs) are transformed in the environment. PFAAs are synthetic chemicals that are used as coating for carpets, textiles and paper, and fire extinguishing foams. Because PFAAs are very unreactive chemicals, they are extremely persistent compounds in the environment. They also pose threats to human and ecological health, for instance as pollutants in drinking water. The overall goal of this project is to test various chemical conditions in which one can improve the destruction of PFAAs in aqueous environment. At the same time, the energy demand for such a process should be reduced. Several undergraduate and graduate students are getting trained during this project as they engage in multidisciplinary research in environmental chemistry. Furthermore, the investigators actively use research strategies and findings from this project to reach out to K-12 students and educators. Professor Vyas and his team employ a coupled experimental and computational approach to carry out this project. They use two representative PFAAs, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS). Chemical computations using density functional theory and post-Hartree-Fock-based calculations provide guidance for experimental efforts. The experiments iteratively feed findings back into the chemical computations. This improves the models and explains unusual experimental findings. The Vyas lab studies the degradation of PFAAs using superoxide radical anion, hydroxyl radical, and persulfate radical anion in the presence of transition metal cations. These reactions are likely facilitated by heat or by external light. Time-resolved absorption spectroscopic measurements provide information on reactive intermediates and the efficiency of light triggered reactions. Mass spectrometric and chromatographic measurements are used to monitor reaction products. Students participating in this inherently interdisciplinary research project acquire a unique skill set that incorporates elements of computational and experimental environmental chemistry, providing them with skills for their future careers. This project is also used as a vehicle to incorporate concepts of environmental computational chemistry into undergraduate and graduate chemistry curricula.