Due to the diverse functionality of per- and polyfluoroalkyl substances (PFAS), they have been mass-produced and applied in a variety of industries and daily life. Because of the chemical persistence and mobility, PFAS have been frequently detected in groundwater and surface water resources in the United States (U.S.), and potentially impact drinking water safety. Studies have estimated that 6 million residents in the U.S. are exposed to PFAS in drinking water in excess of the U.S. Environmental Protection Agency lifetime health advisory of 70 ng/L for the sum of perfluorooctanesulfonic acid and perfluorooctanoic acid. Traditional drinking water treatment technologies do not remove PFAS efficiently. As the most employed technology, granular activated carbon (GAC) is effective to remove some long-chain PFAS; however, GAC is less effective for removal of short-chain PFAS and PFAS precursors, and co-occurring chemicals such as natural organic matter can impede full regeneration. Small drinking water facilities may not be equipped with advanced adsorption technologies. GAC and other sorption technologies such as ion-exchange resins (IX) do not destroy PFAS. Spent GAC or IXs require disposal or regeneration, yielding concentrated PFAS brine that needs to be carefully handled. Thermal based technologies can completely break carbon-fluoride bonds of PFAS but are energy intensive and economically questionable, and there are knowledge gaps regarding temperatures required for complete degradation of all PFAS to harmless by-products.
The objectives of this project are to develop highly selective and regenerable sorbents and evaluate and optimize the efficacy of thermal destruction of PFAS for remote, off-site impacted water resources treatment. The specific objectives are:
- Design and synthesize highly selective macrocyclic-based adsorption materials for PFAS removal and enrichment.
- Evaluate the influence of co-occurring chemicals during adsorption.
- Optimize regeneration approaches to create a concentrated brine for subsequent thermal destruction.
- Develop and evaluate a thermal catalytic approach to completely degrade PFAS brine into harmless chemicals.
This project will be achieved through a combination of material design, atomistic simulation, analytical experiments, and reactor engineering. Specifically, in Objective 1, density functional theory simulation will assist the design of macrocyclic-based polymers and tune the binding to chemically diverse PFAS. The new sorbents will be tested and optimized for best treatment and regeneration strategies using both PFAS-spiked and aqueous film-forming foam (AFFF)-impacted media in Objective 2. In Objective 3, a systematic mass balance based on gas and liquid phase analysis will be investigated in a thermal reactor to evaluate the degree of PFAS thermolysis and achieve complete degradation. Finally, a preliminary life cycle cost and technology transition will be performed to evaluate the technology.
This work will provide an effective and synergistic physical removal/chemical destruction strategy to eliminate PFAS in drinking water, which will support surface water and groundwater remediation from the numerous AFFF-impacted sites, thus reducing the overall risks to human health due to PFAS exposure. The newly developed materials may overcome the low chemical selectivity, fouling, and regeneration challenges of the existing sorbents. The thermal degradation study will generate the essential data and conditions to completely degrade PFAS. The research will include real AFFF-impacted media that will provide data regarding newly identified PFAS. Results will provide the foundation for future, pilot-scale studies at AFFF-impacted sites. The technology can be further developed and integrated and will also have potential applications to clean up PFAS-impacted sites not limited to water resources. The integrated technology will be of broad interest and relevance to PFAS remediation both within the U.S. and internationally.