Quantification of In Situ Chemical Reductive Defluorination (ISCRD) of Perfluoroalkyl Acids in Groundwater Impacted by AFFFs

Dr. Linda Lee | Purdue University

ER-2426

Objective

Perfluoroalkyl substances (PFASs), because of their heat resistance and their ability to block oxygen to and suppress volatile vapors from flammable solvents, are components of aqueous film-forming foams (AFFFs) used to fight fires. However, PFASs appear to bio-accumulate and persist in the environment, with toxicity to both wildlife and humans. Such findings led the U.S. Environmental Protection Agency (USEPA) in 2009 to develop provisional health advisories to minimize potential risk from exposure to these chemicals through drinking water.

Currently, there are no viable in situ treatment methods available for the range of PFASs common to military sites where training with AFFFs occurred. Advanced oxidative technologies have been demonstrated for perfluorooctanoic acid (PFOA) and other PFASs, but not for pefluorooctane sulfonate (PFOS) applicable to in situ application. Similarly, biological treatment has not been demonstrated effective for either PFOA or PFOS.

The objective of this project is to develop reductive technologies as a first step in remediating linear PFOS as a representative PFAS. Researchers will quantify optimal working conditions and the effectiveness of a subset of reductive technologies and couple the most successful reductive approaches to oxidative technologies to obtain highly effective destruction in a cost-effective in situ treatment train for remediation of PFASs in contaminated aquifer systems.

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Technical Approach

This project will investigate the use of zero-valent metals/bimetals (Pd /Fe , Mg , Pd/Mg ) including Pd /Fe  synthesized within clay interlayers for ease of injection and reduced loss of reactivity, as well as co-solvent assisted Vitamin B12 defluorination. Researchers will quantify the magnitude, rate, and effectiveness of abiotic reductive techniques to defluorinate linear PFOS in aqueous systems within an environmentally relevant PFOS concentration range and at three pH values spanning 4 to 9. Intermediates resulting from incomplete defluorination will be characterized. The team will quantify the effectiveness of smectite intercalated Pd /Fe  to defluorinate PFOS by measuring loss of PFOS and generation of fluoride and sulfate. The team will also quantify the effect of ionic composition and co-contaminants in aqueous system defluorination in a subset of reductive systems. Defluorination in vadose zone soils and aquifer materials will be evaluated using a subset of the most favorable abiotic reductive transformation approaches. Finally, the team will assess increased potential for oxidation of intermediates towards evaluating selected reductive/oxidative treatment trains.

ER-2426 Project Graphic 1

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Benefits

This project addresses the reductive reaction mechanisms and pathways (intermediates) for defluorination of PFOS and associated PFASs, which will facilitate design of an in situ strategy for remediation of PFAS-contaminated groundwater at military sites with minimal adverse impacts. Site managers and consultants will be able to use these results to improve long-term site management plans. The project will also provide additional analytical tools for identifying and quantifying defluorination products and elucidate potential naturally occurring albeit abiotic processes that may be enhanced. (Anticipated Project Completion - 2018)

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Publications

Park, S., J. Zenobio*, and L.S. Lee. 2018. Perfluorooctane sulfonate (PFOS) loss with Pd /nFe  nanoparticles: adsorption and Fe-complexation, not transformation, Journal of Hazardous Materials, 342:20-28.  https://doi.org/10.1016/j.jhazmat.2017.08.001

Park, S., C. de Perre, and L.S. Lee. 2017. Alternate reductants with VB12 to transform C8 and C6 Perfluoroalkyl Sulfonates: Limitations and insights into isomer-specific transformation rates, products and pathways. Environmental Science & Technology, 51 (23):13869–13877.  https://doi.org/10.1021/acs.est.7b03744

Park, S. L.S. Lee, V. F. Medina, A. Zull, and S. Waisner. 2016. Heat-activated persulfate oxidation of PFOA, 6:2 fluorotelomer sulfonate, and PFOS under conditions suitable for in-situ groundwater remediation. Chemosphere, 145:376-383.  https://doi.org/10.1016/j.chemosphere.2015.11.097

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Points of Contact

Principal Investigator

Dr. Linda Lee

Purdue University

Phone: 765-494-8612

Fax: 765-494-8612

Program Manager

Environmental Restoration

SERDP and ESTCP

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