Influence of Soil Minerals on the Adsorption, Structure, and Dynamics of GenX

Inrecent years, there have been increasing initiatives undertakenworldwide to employ alternative per- and polyfluoroalkyl substances(PFAS) molecules in order to minimize the environmental and healtheffects associated with legacy PFAS molecules. Hexafluoropropyleneoxide dimer acid (HFPO-DA), commonly known as GenX, is one of theimportant replacements currently used for PFOA. However, growing investigationssuggest that GenX is identified in natural settings, including soilsand groundwater, thus emphasizing the need to understand their sorptionbehavior in these environments. This study provides molecular-levelinsights into the impact of three different common soil constituents,namely, clay minerals, that vary in mineralogical composition andsurface charge distribution in dictating the adsorption and transportcharacteristics of GenX on a fundamental molecular level for the firsttime using molecular dynamics simulations. The surface complexationof GenX varies significantly between the three clay minerals, andthe factors that dictate the complexation are completely different.Depending upon the clay minerals, both surface-adsorbed and solution-phaseGenX are observed. Importantly, the interfacial structure, nearestneighbor coordination, and dynamic behavior of GenX and their correlationwith legacy PFAS in minerals systems are presented. This study unravels the critical interactionsthat dictatethe fate and the transport behavior of GenX in soil minerals.