Removal of Complex Mixtures of Perfluoroalkyl Acids from Water Using Molecularly Engineered Coatings on Sand and Silica

Paul Edmiston | The College of Wooster



The use of aqueous film forming foam (AFFF) in fire control measures has led to the detection of recalcitrant per- and polyfluoroalkyl substances (PFASs) in groundwater at numerous DoD facilities. Cost effective remediation technologies will be required for environmental restoration since microbial and abiotic degradation of PFASs are too slow to allow for natural attenuation. Remediation strategies are complicated by the numerous types of PFASs and their breakdown products found in the AFFF formulations used by the DoD. In this proof-of-concept project, mesoporous organosilica sorbents will be evaluated for the removal of a wide range of PFASs, including anionic, cationic, and non-ionic forms. Adsorption will be designed to be reversible allowing for economical on-site regeneration by solvent rinse. Successfully designed sorbent media could be used for ex situ pump-and-treat remediation systems or point-of-entry water treatment.

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Technical Approach

Organosilica-based sorbents that have proven capable of removing PFASs from water in preliminary work will be further optimized, characterized, and studied. Mesoporous sorbents will be synthesized by a sol-gel based method varying the pore size and surface chemistry. After characterization, the best performing materials will be assessed by equilibrium binding experiments. Materials with the best affinity and capacity will be further evaluated alongside commercially available Osorb® and PuraSorbTM measuring bench-scale adsorption isotherms and breakthrough curves for a diverse set of PFASs. Treatment of groundwater obtained from a representative DoD site impacted by a range of AFFF-derived PFASs will be tested in bench-scale column tests. Regeneration by solvent rinse will also be evaluated. Mechanisms of adsorption will be studied indirectly using competitive adsorption experiments, and directly by infrared spectroscopy. Laboratory work will be followed by a 1 gal/min pilot test at a DoD facility to obtain data to assess in-field performance and estimate costs to conduct remediation at scale.

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Technologies that can be used for economical remedial action for a wide range of PFASs are needed to manage groundwater resources at DoD facilities. Organosilica sorbents will be optimized for performance across a wide range of expected PFASs, including short chain PFASs that are traditionally challenging to capture with sorbent media. The major benefit of the adsorbent media is lower operation and maintenance costs resulting from the development of a regenerable, PFAS-specific media for on-site treatment. The processed waste stream would be an alcohol “brine” of PFASs that could be efficiently destroyed by incineration. The result would be lower costs due to reduced media replacement and transportation while allowing PFAS treatment to be fully addressed on-site. Additionally, this media has shown potential to treat short chain PFASs. While short chain PFASs are currently unregulated, a technology that can treat the entire range of PFASs will result in a reduction of long term liability in a changing regulatory landscape. (Anticipated Project Completion - 12/2019)

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Points of Contact

Principal Investigator

Dr. Paul Edmiston

The College of Wooster

Phone: 330-263-2113

Program Manager

Environmental Restoration