The Versatility of Surface-Modified Clay Adsorbents for PFAS Treatment

Surface-modified clay adsorbents are highly effective at removing perfluoroalkyl and polyfluoroalkyl substances (PFAS) from a variety of water types. These adsorbents are made by loading clay with a modification agent that has a high affinity for PFAS. The modification agent, which has electrostatic and hydrophobic moieties, is attached to the plate-like crystalline structure of the clay via cation exchange sites to form adsorptive inter-platelet layers or galleries. Exchangeable cations in the clay, like sodium and calcium, are replaced, thereby eliminating swelling when hydrated. Surface modified clay has been investigated in the laboratory and in the field for treatment of a variety of PFAS (short and long chain) and have the ability to remove PFAS to non-detect concentrations in groundwater, waste water, and landfill leachate. The media is resistant to the detrimental effects of water constituents, like dissolved organic carbon and anions, on PFAS adsorption and provides fast adsorption kinetics, resulting in a low empty bed contact time when used in filtration vessels. Surface-modified clay can also be used to stabilize PFAS in soil, as verified with multiple leaching tests, injected/emplaced for subsurface remediation, and installed as a sediment cap. Results with soil, groundwater, drinking water, and landfill leachate will be presented.Ope