Formatted Title
In Situ Electro-Osmosis Removal of PFAS from Impacted Soils
Background/Objectives
With DoD’s large number of AFFF-impacted sites requiring investigation, monitoring, and interim remedial activities, a large volume of solid and liquid investigation-derived waste (IDW) is produced. The treatment and disposal of PFAS-containing IDW presents unique challenges as treatment technologies and best practices for handling and disposition are currently evolving. There is a significant need to treat PFAS-impacted solids that are IDW and generated as part of soil removal actions. Few viable technologies are currently available for the treatment of PFAS-impacted solid matrices. Applying electro-osmosis for soil decontamination is a Battelle-patented method that is effective for PFAS removal while being less energy-intensive. Electro-osmosis operates by transporting water (contaminated with PFAS) through porous media under the influence of an applied electric potential. This process drives the PFAS trapped in the air-water/air-soil interfaces of the pore-water and soil pores. The collected PFAS mainly concentrates on the anode which can then be further destroyed using PFAS destruction technologies. The electro-osmosis method can be used as a treatment train approach as an in-situ application for the removal of PFAS in soil media.
Main objective of the study is to investigate PFAS removal from the laboratory-spiked saturated soil and applying electrical energy to the electrodes to mobilize contaminated water media from the soils. Both the laboratory contaminated soils and PFAS-impacted field soils were tested.
Approach/Activities
Electro-osmosis is a process where water and contaminants are transported through porous media using an applied electric potential. As part of Battelle’s Internal Research and Development project, proof-of-concept experiments were carried out to develop soil treatment technology for PFAS contamination. The experiments involved using an electric field with three pairs of electrodes to mobilize the contaminated water and concentrate the PFAS at the anode side of the electrode. The concentrated PFAS can then be removed and destroyed. The main objective of the proof-of-concept research was to investigate the removal of PFAS from saturated soil impacted by PFAS, considering the anode and cathode distance, holding time, voltage, moisture content, and electrolyte media.
Results/Lessons Learned
During the experiment, it was observed that water was moving towards the cathode, while the PFAS was moving towards the anode. This reverse trend was caused by the negatively charged tails of surfactants, which led to the depletion of PFAS near the cathode. The removal of PFAS increased with voltage gradient and holding time. Further, chain length and functional group dependent trends were observed. Additionally, all test conditions resulted in a low concentration of PFAS detected in the leachate