Investigating Electrocatalytic and Catalytic Approaches for In Situ Treatment of Perfluoroalkyl Contaminants in Groundwater

Dr. Charles Schaefer | CDM Smith

ER-2424

Objective

The objective of this project is to develop and assess the use of electrocatalytic and catalytic approaches for in situ treatment of poly- and perfluoroalkyl substances (PFASs) in groundwater. Specifically, electrocatalytic approaches will focus on the ability of ruthenium oxide-coated titanium (Ti/RuO2) and other mixed metal oxide (MMO) anodes to oxidize PFASs in groundwater under a wide range of conditions; catalytic approaches will focus on the use of supported rhodium-based catalysts for the hydrodefluorination of PFASs in groundwater under ambient conditions. Preliminary bench-scale testing of these technologies by the project team, along with previously published studies, indicate that these technologies hold exceptional promise for the in situ treatment of PFASs under ambient conditions at many Department of Defense (DoD) facilities. Reaction kinetics, reaction intermediates and products, optimal catalyst materials, geochemical and co-contaminant impacts on treatment effectiveness, and potential applicability to field-scale remediation will be evaluated as part of this project.

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Technical Approach

This project will consist of a series of bench-scale batch and column experiments using both MMO anodes and supported rhodium-based catalysts. Initial efforts will focus on selecting and/or formulating optimal MMO and rhodium-based catalyst materials for treatment of PFASs. Batch experiments, using simplified aqueous systems (with respect to water geochemistry and contaminant mixtures), will then be performed to obtain a fundamental understanding of reaction mechanisms, pathways, and rates. To understand the potential formation of harmful degradation products, substantial analytical effort will be expended to provide adequate characterization of transformation products. Subsequent batch experiments using synthetic and natural groundwaters will employ the use of PFAS mixtures (including precursor compounds), hydrocarbon or chlorinated solvent co-contaminants, and a range of geochemical conditions. Column experiments will be performed for both the electrocatalytic and catalyst systems to evaluate material longevity and to assess remedial performance under conditions more representative of potential field-scale implementation. Detailed analyses will be performed on the electrode and catalyst materials to assess the nature and extent of any fouling or deactivation mechanisms.

ER-2424 Photo

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Benefits

PFASs have become a concern of growing urgency for DoD. With several studies showing the presence, or potential presence, of these compounds in groundwater associated with fire training areas, adverse PFAS impacts on groundwater are potentially widespread at DoD facilities. However, with conventional technologies ineffective or inefficient for treatment and the well-documented recalcitrance of PFASs with respect to natural or enhanced degradation processes, cost-effective in situ treatment options for these compounds are currently not available. Development of electrocatalytic and catalytic approaches is expected to provide remedial tools that can be efficiently and cost-effectively applied for treatment of PFAS-impacted groundwater at a wide range of DoD facilities. (Anticipated Project Completion - 2018)

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Publications

Liu, J., D.J. Van Hoomissen, T. Liu, A. Maizel, X. Huo, S.R. Fernández, C. Ren, X. Xiao, Y. Fang, C. Schaefer, C.P. Higgins, S. Vyas, and T.J. Strathmann. 2018. Reductive Defluorination of Branched Per-and Polyfluoroalkyl Substances with Cobalt Complex Catalysts. Environmental Science & Technology Letters. doi:10.1021/acs.estlett.8b00122

Schaefer, C.E., C. Andaya, A. Burant, C.W. Condee, A. Urtiaga, T.J. Strathmann, and C.P. Higgins. 2017. Electrochemical Treatment of Perfluorooctanoic Acid and Perfluorooctane Sulfonate: Insights into Mechanisms and Application to Groundwater Treatment. Chemical Engineering Journal, 317:424-432.

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Points of Contact

Principal Investigator

Dr. Charles Schaefer

CDM Smith

Phone: 732-590-4633

Program Manager

Environmental Restoration

SERDP and ESTCP

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