Treatment of PFAS-impacted Matrices by Dissolving Metal Reduction with Mechanochemical Mixing

Paul Tratnyek | Oregon Health & Science University

ER22-3286

Objective

This project aims to demonstrate a novel process for treatment of per- and polyfluoroalkyl substance (PFAS) impacted matrices that combines several previously proven methods of PFAS degradation in a way that overcomes the individual limitations that have prevented their full-scale application. The process—which involves combining dissolving metal reduction (DMR) with zerovalent magnesium (Mg ) and mechanochemical mixing (MCM) by ball milling—is likely to produce rapid, deep, and sustained defluorination of PFAS via solvated electrons. Testing this novel combination of treatment processes is the overall objective of this proof-of-concept project.

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Technical Approach

Many methods of treating matrices (including solids and liquids) impacted with PFAS are under investigation, but most are either marginally effective or complex to implement. Solvated electrons can defluorinate PFAS, but the advanced reduction processes currently used to achieve this are difficult to up-scale for engineering applications. Mg  is known to generate solvated electrons by DMR, but harnessing this chemistry for remediation applications has proven difficult. MCM—i.e., “ball milling”—has proven to be very effective for maintaining optimal conditions for DMR (and is widely used for other purposes in industry), but there has been just a few studies that combine MCM with Mg  for treatment applications and even fewer have considered MCM for degradation of PFAS. This project will test the entirely novel, but highly promising, intersection of these three approaches for treatment of PFAS impacted matrices: i.e., ball-milling with Mg  for advanced reduction of PFAS. Variations on this approach could be applied to impacted liquids and solids (from groundwater to spent carbon adsorbents), ex situ or in situ (e.g., with micron-sized injectable Mg/Fe alloy), and for treatment of complex and/or concentrated mixtures (membrane backwash, aqueous film forming foams, etc.).

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Benefits

If the combination of DMR and MCM is as effective at degradation of PFAS is anticipated, and if the DMR-MCM process is as up-scalable and compatible with existing PFAS treatment processes as anticipated, then DMR-MCM could quickly become a significant component of the “tool kit” of options for treatment of PFAS-impacted matrices. The DMR-MCM process should not only give nearly complete degradation of PFAS in liquid matrices, it should also be applicable to a variety of solid matrices (ranging from spent granular activated carbon or resin and soil). Many variations of DMR-MCM are possible: e.g., combination with zerovalent iron or fine-grained carbon to produce injectable media for in situ applications—that could be developed in future work.

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Points of Contact

Principal Investigator

Dr. Paul Tratnyek

Oregon Health & Science University

Phone: 503-346-3431

Fax: 503-346-3417

Program Manager

Environmental Restoration

SERDP and ESTCP

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