Hundreds of Department of Defense sites in the U.S. are impacted by per- and poly-fluoroalkyl substances (PFAS) due to historic use of aqueous film-forming foam (AFFF) for fire suppression. The standard approach to treat PFAS-impacted water involves sorption of dissolved PFAS with granular activated carbon (GAC) or single-use ion exchange resins (IX) followed by regeneration, destruction, or disposal of used sorbent. However, both sorbents have major drawbacks, ranging from high regeneration cost to production of secondary wastes.
The goal of this project is to determine, through controlled experiments under realistic conditions, whether a class of novel sorbents – swellable ionomers – outperforms conventional sorbents in removing a broad range of PFAS from water without the drawbacks that have been plaguing conventional sorbents. The project team will address the following four objectives:
- Develop cost effective treatment approaches for PFAS-impacted matrices, including but not limited to groundwater, soils, aquatic sediments, spent media, and AFFF concentrate.
- Develop cost effective approaches for complete destruction of PFAS bound onto spent media (e.g., GAC and single-use IX), regeneration of spent media, and treatment of associated ancillary waste streams.
- Evaluate treatment technologies using field-impacted media containing PFAS mixtures and common environmental treatment complications (e.g., water quality parameters, co-occurring chemicals).
- Develop treatment train approaches that cost-effectively treat PFAS and facilitate treatment of co-occurring chemicals.
The project team will conduct a series of PFAS (de)sorption and defluorination experiments to test three hypotheses, each corresponding to an advantage of ionomers stated above. The project team will use mixtures of representative PFAS, AFFF formulations, and groundwater from a PFAS-impacted site for this project. PFAS sorption kinetics and capacity will be investigated to assess ionomer performance against those of model GAC and IX. Hydrothermal treatment of aqueous PFAS solutions and PFAS-laden ionomers will be studied using a temperature/pressure/pH-controlled reactor system customized for PFAS defluorination experiments. PFAS and their degradation products will be quantified by liquid chromatography-mass spectrometry, ion chromatography, interdisciplinary science and engineering, total organic carbon, and total bound nitrogen to establish carbon and fluorine mass balances.
The swellable ionomers do not contain/use fluorinated chemicals, unlike several of the new sorbents being developed for PFAS removal, such a cyclodextrin polymers, ionic fluorogelsand swellable organically modified silica. Hence, there is no risk of releasing fluorinated chemicals during production or use or after disposal. If the hypotheses are correct, ionomers may replace GAC and IX as faster and higher capacity sorbents that can be quickly regenerated on-site without creating cosolvent/brine waste streams. In addition, PFAS-laden ionomers may be directly treated hydrothermally to degrade sorbed PFAS and regenerate ionomers simultaneously, thus simplifying the treatment train and reducing treatment time, cost, and complexity. The project team envisions that stationary systems and mobile units based on the ionomer technology can be developed for liquid investigation-derived waste and wastewater treatment and for groundwater remediation.