The overall goal of this project is to improve commercially available adsorbents, such as anion exchange resins and granular activated carbon (GAC), through specific surface chemistry modifications that enhance the capacity and selectivity for 18 ultrashort- and short-chain per- and polyfluoroalkyl substances (PFAS). In particular, the project team will develop (i) hybrid anion-exchange (HAIX) resins, (ii) metal oxide-biochar composites, and (iii) multi-PFAS templated molecularly imprinted polymers on granular activated carbon (mMIP@GAC) adsorbents. These novel materials will be developed, characterized, and evaluated for adsorption, desorption, and performance in PFAS-impacted waters.

The HAIX, metal oxide-biochar, and mMIP@GAC adsorbents represent paradigm shifts that are anticipated to improve the ability to remove ultrashort- and short-chain PFAS from impacted waters. The project team has identified 18 ultrashort- and short-chain PFAS as targets, but additional chemicals of concern will be considered during the project period. The project objective will be achieved through (i) materials development and characterization, (ii) batch adsorption tests to identify isotherm parameters, determine the impacts of water quality parameters, and measure mass transport properties, (iii) batch regeneration tests to optimize not only PFAS desorption, but also PFAS destruction in downstream processes, and (iv) column tests to demonstrate the performance of the materials in at least six real waters collected from DoD facilities, extend treatment capacity compared to the base materials, and measure design parameters needed for future scale-up efforts.

The research plan involves six specific tasks:

1. Develop and characterize novel HAIX, metal oxide-biochar, and mMIP@GAC adsorbents with enhanced capacity and selectivity for ultrashort- and short-chain PFAS.
2. Generate adsorption isotherms, confirm adsorption mechanisms, and develop relationships between isotherm parameters, PFAS properties, and adsorbent characteristics.
3. Optimize regeneration protocols for the adsorbents to improve downstream PFAS destruction in spent regenerants or enhance process sustainability through solvent reuse.
4. Measure the uptake kinetics and mass transport parameters, including intraparticle diffusion coefficients, of the targeted ultrashort- and short-chain PFAS in the adsorbents.
5. Investigate the impacts of water quality parameters, such as solution pH, background anions and cations, dissolved organic matter content, and temperature, on PFAS adsorption.
6. Conduct conventional and rapid small-scale column tests with the adsorbents and their base materials to demonstrate enhanced performance and scalability.

The expected outcomes of this work include (i) improved capabilities for the removal and concentration of ultrashort- and short-chain PFAS in ex situ water treatment processes or remediation operations, (ii) better understanding of the fundamental adsorption-desorption behavior of PFAS with innovative adsorbents designed for treatment of PFAS that are poorly adsorbed by conventional materials, and (iii) enhanced regeneration protocols that are amenable to downstream PFAS destruction. As all three adsorbent classes build upon commercially available materials, the project team is confident in the feasibility of technology transfer and timely implementation. The main benefit of these sorbents stems from the improved removal of ultrashort- and short-chain PFAS in fixed-bed adsorption reactors. (Anticipated Project Completion - 2028)