Grantee Research Project Results

Final Report: Capacitive removal of PFOA and PFOS from Drinking Water

EPA Contract Number: 68HE0D18C0020
Title: Capacitive removal of PFOA and PFOS from Drinking Water
Investigators: Cox, Philip
Small Business: Mainstream Engineering Corporation
EPA Contact: Packard, Benjamin H
Phase: I
Project Period: October 1, 2018 through March 31, 2019
Project Amount: $99,878
RFA: Small Business Innovation Research (SBIR) - Phase I (2018) RFA Text |  Recipients Lists
Research Category: SBIR - Water , Small Business Innovation Research (SBIR) , SBIR - Drinking Water and Water Monitoring

Description:

Perfluoroalkyl substances (PFAS) in drinking and other ground water sources have been linked to increased chances of cancer and other health problems including hormone disruption, high cholesterol, and reproductive and developmental risks. PFAS represent a significant risk due to their high water solubility and chemical stability, which makes them highly persistent in the environment. The established concentration limits are 70 parts per trillion for drinking water.

Summary/Accomplishments (Outputs/Outcomes):

In this successful Phase I, Mainstream has successfully demonstrated the efficient, high-capacity, and rapid removal of PFAS compounds such a perfluorooctanic acid (PFOA) by electrosorption using our high-performance, high- durability, templated carbon nanotube (CNT) electrode structures. Specifically, Mainstream has completed the following:

• Demonstrated the reversible adsorption of PFAS such as PFOA onto a stable, templated CNT- based electrode structure.

• Demonstrated batched-based extractions with PFAS adsorption up 0.7 mmol/g of carbon or 5 mg of PFOA per cm² of electrode area, providing sizing information for the prototype system to be built and optimized in Phase II.

• Demonstrated continuous and stable removal of PFOA from a continuous water feed, dependent on the flow rate and applied voltage, thus providing the critical process and sizing information for the prototype system to be built in Phase II.

• Demonstrated a scalable, multicell, electrosorption cell design configuration that can be sized for the removal capacity and targeted water flow rates.

• Demonstrated electrode stability and reproducibility over multiple extraction cycles and conditions.

• Demonstrated controlled desorption of the PFAS species from the electrode, thus allowing the design, sizing, and controls for the system in Phase II.

Conclusions:

In Phase II, Mainstream will use the overall process conditions and system scaling information obtained from Phase I, combined with the engineering advances and designs from our previous development program for the desalination of brackish water, to build and optimize a prototype PFAS extraction system. We will build demonstration units for the continuous clean-up of drinking waters with high PFOA/PFOS levels. Additionally, with high removal rates and capacities for our proposed units, Mainstream expects that the electrosorption system will readily find application with the removal of PFAS compounds from groundwater and other process streams.