NSF Award
2219832
Per- and polyfluoroalkyl substances (PFAS) are fluorinated organic chemicals that have emerged as priority pollutants during the last two decades due to increasing concerns about their persistence, stability, and toxicity as they accumulate in the environment. The detection of PFAS in drinking water has raised significant concerns about their impact on human health. PFAS are difficult to degrade and destroy using conventional water treatment oxidants (e.g., chlorine, ozone, and hydrogen peroxide) due to their strong C-F covalent bonds and C-F bond polarization which causes steric hindrance to chemical attack. Sorption onto granular activated carbon (GAC) filter beds has emerged as the most efficient and cost-effective process from removing PFAS from contaminated drinking water sources. However, spent PFAS-laden GAC filter beds need to be disposed of or regenerated to enable their reuse. The overarching goal of this project is to investigate the viability of thermal regeneration as an efficient and cost-effective process to enable the reuse of PFAS-laden GAC filter beds while catalyzing the degradation and destruction of the sorbed PFAS contaminants. To advance this goal, the Principal Investigators (PIs) propose to test the hypothesis that the abundance of highly mobile electrons on the graphitic surface of activated carbon will catalyze the thermolysis and subsequent degradation of sorbed PFAS molecules from spent GAC filter beds. The successful completion of this research will benefit society through the generation of new fundamental knowledge to advance the utilization of GAC as an efficient and cost-effective sorbent for the treatment of PFAS contaminated drinking water sources. Additional benefits to society will be accomplished through education and training including the mentoring of one graduate and one undergraduate student at the University of Maine and one graduate and one undergraduate student at the University of Nevada, Reno.<br/><br/>Granular activated carbon (GAC) has been demonstrated in the field and at scale to be the most efficient and cost-effective sorbent from removing PFAS contaminants from drinking water sources including pretreated surface water and groundwater. Thermal regeneration is an established process for the regeneration of spent PFAS-laden GAC beds. However, a fundamental understanding of the mechanisms of PFAS degradation, transformations, and destruction during the thermal regeneration of spent GAC filter beds has remained elusive. The goal of this project is to advance the fundamental understanding of PFAS degradation, transformations, and destruction during the thermal regeneration of PFAS-laden GAC beds under relevant process and field conditions. The specific objectives of the research are to: 1) Investigate the effect of thermal regeneration on the physicochemical properties of commercially available and well-characterized GAC PFAS sorbent candidates; 2) Evaluate the impacts of heating rate, regeneration temperature, gaseous atmosphere, and reactivation agents on PFAS degradation/transformations and GAC regeneration efficiency; 3) Assess the impact of GAC pore structure and surface chemistry on the extent and rate of PFAS thermolysis; and 4) Characterize and unravel the desorption, decomposition, and mineralization pathways of sorbed PFAS during the thermal regeneration of PFAS-laden GAC beds. The successful completion of this project has the potential for transformative impact through the generation of fundamental knowledge and performance data to advance the implementation of GAC sorption as an efficient, cost-effective, and sustainable process for the treatment of PFAS contaminated drinking water sources. To implement the educational and outreach goals of this project, the Principal Investigators (PIs) plan to integrate the findings from this research into existing undergraduate/graduate courses at the University of Maine and the University of Nevada, Reno. In addition, the PIs propose to leverage existing programs at their respective institutions to host a “Girls Scouts” outreach program to teach basic concepts of environmental engineering and water treatment to K-3 grade students.<br/><br/>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.
