14 May 2024

Properties and Mechanisms for PFAS Adsorption to Aqueous Clay and Humic Soil Components

Abstract: The proliferation of poly- and perfluorinated alkyl substances (PFASs) has resulted in global concerns over contamination and bioaccumulation. PFAS compounds tend to remain in the environment indefinitely, and research is needed to elucidate the ultimate fate of these molecules. We have investigated the model humic substance and model clay surfaces as a potential environmental sink for the adsorption and retention of three representative PFAS molecules with varying chain length and head groups. Utilizing molecular dynamics simulation, we quantify the ability of pyrophyllite and the humic substance to favorably adsorb these PFAS molecules from aqueous solution. We have observed that the hydrophobic nature of the pyrophyllite surface makes the material well suited for the sorption of medium- and long-tail PFAS moieties. Similarly, we find a preference for the formation of a monolayer on the surface for long-chain PFAS molecules at high concentration. Furthermore, we discussed trends in the adsorption mechanisms for the fate and transport of these compounds, as well as potential approaches for their environmental remediation.

31 Mar 2022

Design, Construction, and Testing of the PFAS Effluent Treatment System (PETS), a Mobile Ion Exchange–Based System for the Treatment of Per-, Poly-Fluorinated Alkyl Substances (PFAS) Contaminated Water

Abstract: Poly-,Per-fluorinated alkyl substances (PFAS) are versatile chemicals that were incorporated in a wide range of products. One of their most important use was in aqueous film-forming foams for fighting liquid fuel fires. PFAS compounds have recently been identified as potential environmental contaminants. In the United States there are hundreds of potential military sites with PFAS contamination.The ERDC designed and constructed a mobile treatment system to address small sites (250,000 gallons or less) and as a platform to field test new adsorptive media. The PFAS Effluent Treatment System (PETS) has cartridge filters to remove sediments and a granular activated carbon (GAC) media filter to remove organic compounds that might compete with PFAS in the ion exchange process, although it may also remove PFAS too. The last process is an ion exchange resin specifically designed to remove PFAS to a target level of 70 ng/L or less (equivalent to the US Environmental Protection Agency (EPA) Drinking Water Health Advisory). The system was tested at Hurlburt Field, a US Air Force facility in Florida and at Naval Support Activity (NSA) Mid-South in Millington, TN.