Grantee Research Project Results
Final Report: An Electroactive Point-of-Use Filter for Per- and Polyfluoroalkyl Contaminant Removal
EPA Grant Number: SU839800Title: An Electroactive Point-of-Use Filter for Per- and Polyfluoroalkyl Contaminant Removal
Investigators: Call, Douglas R. , Knappe, Detlef R.U.
Institution: North Carolina State University
EPA Project Officer: Page, Angela
Phase: I
Project Period: October 1, 2019 through September 30, 2020 (Extended to September 30, 2021)
Project Amount: $25,000
RFA: P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet (2019) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards
Objective:
There are more than 4,000 different per-and polyfluoroalkyl substances (PFAS) in use today. Many are widely present in drinking water across the country and pose a public and environmental health threat because of their toxicity and persistence in the environment. Granular activated carbon (GAC) is a widely used sorbent to remove PFAS from drinking water, but it faces several technical challenges, including a limited ability to remove (or adsorb) short-chain PFAS (e.g., GenX). Because GAC is inherently electrically conductive, we hypothesized that electrically charging GAC wouldincrease the adsorption of PFAS. The objectives of the study were to: (1) Determine the adsorption capacities and rates of defined PFAS in a lab-scale, electrically-conductive GAC (e-GAC) device, (2) Modify a commercially available GAC filter housing to contain the e-GAC and demonstrate the ability of the device to remove PFAS from real waters, and (3) Promote education about the public and environmental health hazards of PFAS contaminants and the role of technology in securing safe and sustainable drinking water. To fulfill these objectives, we designed and constructed an electrically-conductive housing for two separate beds of GAC so that they could function as an anode and cathode. We validated that voltage could be applied across the bed to remove charged ions using synthetic salt solutions. Then we studied the removal of two model PFAS in the presence and absence of an applied voltage.
Summary/Accomplishments (Outputs/Outcomes):
By applying a small amount of electricity (1.2 volts) across a bed of GAC, our preliminary tests suggest that enhanced removal of some PFAS is possible. We conducted tests in which a continuous supply of water containing GenX and PFOA (each at 200 ng/L) was supplied to our electroactive GAC filter. We ran an identical filter without applying electricity (open circuit voltage, OCV) as a control to determine removals due to physical adsorption only. Filter effluent samples were collected over time and analyzed for PFOA and GenX. Applying 1.2 volts improved the removal of GenX and PFOA compared to the OCV control by ~12.4% (GenX) and ~3.3% (PFOA). Two main observations can be made. First, breakthrough of GenX occurred earlier than that of PFOA. This result was expected based on the smaller size and lower hydrophobicity of GenX. Hydrophobicity is an important driver of chemical adsorption to GAC. PFOA has a longer, hydrophobic tail than GenX, which results in greater adsorption and later breakthrough of PFOA compared to GenX. Second, the electrical enhancement was more pronounced for GenX than for PFOA. The likely reasons for this difference are the smaller size and lower affinity of GenX for the GAC than PFOA. Because PFOA has a higher affinity for GAC, the additional gains in adsorption due to the applied voltage were insignificant. The affinity of GenX for the GAC was likely increased with the applied voltage due to entrapment in electrical double layers formed inthe micropore structure. The fact that this enhancement occurred while PFOA was present, suggests that adsorption of longer-chain PFAS may not have a pronounced impact on electrosorption of shorter-chain species. However, testing of each GenX and PFOA separately is needed to validate this hypothesis. In summary, our preliminary tests suggest that electrically support in physical adsorption may improve removals of some PFAS and in turn reduce human exposure to PFAS viadrinking water.
Journal Articles:
No journal articles submitted with this report: View all 2 publications for this projectSupplemental Keywords:
PFAS, emerging contaminants, drinking water treatment, sustainable water management, point-of-useRelevant Websites:
Progress 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.