Reactive Electrochemical Membrane (REM) Reactors for the Oxidation of PFAS-Impacted Water

Brian Chaplin | University of Illinois at Chicago

ER18-1491

Objective

Perfluoroalkyl substances (PFAS) are prevalent chemicals in groundwater throughout the U.S. These compounds were contained in aqueous film forming foams (AFFFs), which were used to suppress fires at hundreds of sites. PFAS pose a serious human health risk, and thus the U.S. Environmental Protection Agency has issued a drinking water health advisory level of 70 ng L-1 for PFOS and PFOA. As a result, there has been extensive investigations of groundwater at DoD sites, which generates a large volume of waste containing PFAS, which is termed investigation derived waste (IDW). PFAS removal from water is complicated by low volatility, general lack of reactivity to biodegradation and traditional oxidative treatment processes, and poor desorption kinetics from granular activated carbon and other sorbents. Therefore, novel and effective remediation technologies are needed to treat PFAS-impacted IDWs, which would allow for on-site disposal options that would lower the overall cost of site management.

The overall objective of this work is to utilize a cost-effective reactive electrochemical membrane (REM) for the remediation of PFAS in IDWs. Specific technical objectives associated with this work include: 1) development of REMs for destructive PFAS removal in IDW water samples; 2) determination of the optimal operational mode; and 3) calculation of energy requirements for the REM-based system and comparison to those determined for granular activated carbon adsorption and other technologies.

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Technical Approach

The research team will be investigating the technical and economical feasibility of using REMs for treating IDWs containing PFAS. The REM is a novel electroactive membrane made of porous Ti4O7 with micron-sized pores. Anodic polarization of the REM results in degradation of PFAS through a combination of direct electron transfer reactions and reactions with hydroxyl radicals that are generated from water electrolysis. The small pore size and operation in flow-through mode allows for very fast mass transfer, and thus complete elimination of organic compounds in a single pass through the REM.

ER18-1491 Graphic 1

The work plan consists of REM synthesis, a series of bench-scale experimental studies that will determine optimal operating conditions for PFAS oxidation in groundwater samples, and a preliminary cost assessment. Experimental parameters that will be explored include: 1) adsorption capacity; 2) necessary residence time in the reactor; 3) needed membrane surface area per groundwater volume treated; and 4) energy usage (kWh/m3 water treated). The work is projected to end with proof of concept data that will determine if the REM is suitable for treatment of PFAS-impacted IDW solutions.

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Benefits

The successful completion of this project will have numerous benefits to DoD and the scientific community. These expected benefits include 1) a better understanding of the use of electrochemical technologies for groundwater remediation; 2) the generation of proof of concept data that can be used to develop a field-scale prototype REM for the remediation of PFAS-impacted groundwater; and 3) an energy cost assessment for using the REM technology, which can be used by practitioners to assess the REM technology as a viable remediation option. (Anticipated Completion - June 2019)

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Publications

Le, T.X.H., H. Haflich, A.D. Shah, and B.P. Chaplin. 2019. Energy-Efficient Electrochemical Oxidation of Perfluoroalkyl Substances Using a Ti4O7 Reactive Electrochemical Membrane Anode. Environmental Science & Technology Letters, 6(8):504-510. https://doi.org/10.1021/acs.estlett.9b00397

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Points of Contact

Principal Investigator

Dr. Brian Chaplin

University of Illinois at Chicago

Phone: 217-369-5529

Program Manager

Environmental Restoration

SERDP and ESTCP

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