Grantee Research Project Results
Final Report: Fundamentals of Adsorption, Desorption, and Biodegradation of PFAS and Precursor Compounds in the Soil and Landfill Leachate System and An Innovative Treatment Strategy for Their Removal in Landfill Leachate and Groundwater
EPA Grant Number: R839660Title: Fundamentals of Adsorption, Desorption, and Biodegradation of PFAS and Precursor Compounds in the Soil and Landfill Leachate System and An Innovative Treatment Strategy for Their Removal in Landfill Leachate and Groundwater
Investigators: Xiao, Feng
Institution: University of North Dakota
EPA Project Officer: Hahn, Intaek
Project Period: August 1, 2019 through July 31, 2022 (Extended to July 31, 2023)
Project Amount: $498,907
RFA: Practical Methods to Analyze and Treat Emerging Contaminants (PFAS) in Solid Waste, Landfills, Wastewater/Leachates, Soils, and Groundwater to Protect Human Health and the Environment (2018) RFA Text | Recipients Lists
Research Category: PFAS Treatment , Drinking Water , Water , Human Health , Water Quality
Objective:
• Identify the governing soil sorption and desorption mechanisms (thermodynamics and hysteresis) of per- and polyfluoroalkyl substances (PFAS) in landfill leachate.
• Investigate the biodegradation of sorbed precursor compounds of perfluoroalkyl acids (PFAAs) and examine the effect of sorption hysteresis.
• Innovatively integrate and enhance commonly used water treatment technologies to effectively and practically remove PFAS from the test water.
Summary/Accomplishments (Outputs/Outcomes):
1. A comprehensive dataset and evaluation of adsorption and desorption behaviors for various PFAS compounds in different soil types. The data also includes the hysteresis effects observed for these compounds, informing about their retention and release from soils.
2. We have thoroughly investigated and characterized the efficiency of commercially available granular activated carbon (GAC) for removing PFAS from various water sources, including landfill leachate. We have determined that GAC derived from bituminous sources outperform those derived from coconut shells and lignite coal. We have also demonstrated that pre-ozonation of landfill leachate can enhance PFAS adsorption on GAC.
3. We have developed PFAS adsorption isotherms for GAC in different water types, offering crucial insights into the effect of water chemistry on PFAS adsorption and informing the design of effective GAC treatment systems.
4. We have shown that GAC contaminated with PFAS can be regenerated effectively through heating using conventional and induction methods, providing a solution for reusing this resource and reducing waste.
5. Our studies have examined the thermal stability and decomposition mechanisms of various PFAS on GAC, providing crucial data for understanding their environmental fate and informing the development of effective PFAS removal strategies.
6. We have studied the thermal decomposition mechanisms of novel and emerging PFAS, including perfluoroalkyl ether carboxylic acids (PFECAs) and short-chain perfluoroalkyl carboxylic acids (PFCAs), providing first-hand evidence of their thermal degradation pathways.
7. The bond dissociation energies of various PFAS have been computed, providing new insights into the factors influencing their thermal stability. This information is vital for understanding PFAS degradation and decomposition processes under different conditions.
8. We have identified significant thermal decomposition pathways for some PFAS, highlighting their potential to form volatile organofluorine compounds. This paves the way for more in-depth studies on exposure to these compounds during various thermal processes involving PFAS.
9. Our research has discovered and highlighted the susceptibility of PFAS to decompose on GAC at temperatures lower than previously thought. These findings challenge the common perception of PFAS thermal stability and indicate a new direction for future research.
10. An in-depth understanding of the thermal degradation mechanisms of short-chain PFAS substitutes was provided. The research discovered that these substitutes can also produce compounds like perfluoropropionic acid (PFPrA) and trifluoroacetic acid (TFA) during thermal treatments.
11. Our findings have led to a robust understanding of the effect of chain length and functionality on the thermal stability of PFAS. It has provided first-hand evidence for a C‒C scission mechanism on the perfluorinated backbone through which short-chain PFCAs thermally decompose.
Conclusions:
1. The research has increased our understanding of PFAS behaviors in soil environments. It can predict their fate more accurately, crucial for informing environmental management strategies and risk assessments.
2. We have provided clear guidance for water treatment plants on using GAC-based filtration systems to remove PFAS, significantly improving our ability to reduce PFAS concentrations in drinking water and ensure compliance with safety standards.
3. Our findings have provided crucial insights for landfill operators. We have demonstrated effective strategies for reducing PFAS release into the environment from landfill leachate, directly contributing to improved environmental health and safety.
4. We have provided significant advancements in understanding the thermal degradation mechanisms of PFAS, particularly regarding the formation of potentially hazardous byproducts. These insights will inform safer and more effective strategies for managing PFAS-contaminated materials, including spent GAC and other waste materials.
5. The insights into the thermal stability and decomposition pathways of novel and emerging PFAS provide a foundation for further research into these substances. Our results will inform future work on these compounds, contributing to a broader understanding of PFAS behavior and management strategies.
6. The ability to identify the best treatment strategies for specific types of PFAS contamination has been significantly improved. The data collected can guide the appropriate selection of treatment technologies depending on the specific PFAS present, the medium they are in, and the end goals of the treatment process.
7. The project results will inform the development of regulations and standards related to PFAS. By providing more precise data on PFAS behavior in various environments and during thermal processes, this research can guide policymakers in establishing more effective and science-based regulations.
8. The study provides critical insights into the environmental behavior and thermal decomposition of PFAS substitutes. These are increasingly used due to the phase-out of long-chain PFAS, making it crucial to understand their potential risks.
9. There is an enhanced understanding of PFAS behavior during the thermal regeneration (>400 oC) and reactivation (>600 oC) of GAC. This will inform the design and operation of GAC regeneration processes, improving their efficacy and sustainability.
10. Our results will aid in improving the design and operation of thermal technologies for PFAS degradation. Knowledge of the formation and speciation of incomplete PFAS thermal degradation products is essential for achieving treatment targets while minimizing unwanted product formation.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
Other project views: | All 15 publications | 13 publications in selected types | All 13 journal articles |
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Wang Z, Alinezhad A, Nason S, Xiao F, Pignatello JJ. Enhancement of per-and polyfluoroalkyl substances removal from water by pyrogenic carbons:Tailoring carbon surface chemistry and pore properties. Water Research 2023;229:119467. |
R839660 (Final) |
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Alinezhad A, Shao H, Litvanova K, Sun R, Kubatova A, Zhang W, Li Y, Xiao F. Mechanistic investigations of thermal decomposition of perfluoroalkyl ether carboxylic acids and short-chain perfluoroalkyl carboxylic acids. Environmental Science & Technology 2023;57(23):8796-807. |
R839660 (Final) |
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Wang Z, Alinezhad A, Sun R, Xiao F, Pignatello JJ. Pre-and postapplication thermal treatment strategies for sorption enhancement and reactivation of biochars for removal of per-and polyfluoroalkyl substances from water. ACS ES&T Engineering 2023;3(2):193-200. |
R839660 (Final) |
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Supplemental Keywords:
Adsorption; desorption; degradation; practical removal; enhanced water treatmentProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.