Understanding PFAS sorption mechanism in porous carbon sorbents through neutron scattering

Per- and polyfluoroalkyl substances (PFAS) are an emergent class of environmental contaminants that are present in many water sources. While a variety of porous materials, such as activated carbon (AC) and fluorogels have been reported for PFAS remediation, fundamental sorbent design principles are still unclear due to the lack of knowledge associated with the PFAS sorption mechanism under pore confinement. This talk will discuss how pore size of sorbents can directly dictate the sorption and assembly mechanisms of perfluorooctanoic acid (PFOA) through combined use of small angle neutron scattering and molecular dynamics (MD) simulations. It is found that the limited sorption performance of ACs is due to their pore sizes which are similar to the dimensions of PFOA molecules. With increasing pore size, the transport of PFOA into pore channels is greatly facilitated and layered morphologies along the pore wall driven by favorable hydrophobic-hydrophobic interactions between the sorbate and sorbent surface is experimentally observed for the first time. These insights about the assembly mechanism of PFAS under pore confinement will inform the rational sorbent design for efficient removal of toxic, surfactant-based contaminants.