In
recent years, there have been increasing initiatives undertaken
worldwide to employ alternative per- and polyfluoroalkyl substances
(PFAS) molecules in order to minimize the environmental and health
effects associated with legacy PFAS molecules. Hexafluoropropylene
oxide dimer acid (HFPO-DA), commonly known as GenX, is one of the
important replacements currently used for PFOA. However, growing investigations
suggest that GenX is identified in natural settings, including soils
and groundwater, thus emphasizing the need to understand their sorption
behavior in these environments. This study provides molecular-level
insights into the impact of three different common soil constituents,
namely, clay minerals, that vary in mineralogical composition and
surface charge distribution in dictating the adsorption and transport
characteristics of GenX on a fundamental molecular level for the first
time using molecular dynamics simulations. The surface complexation
of GenX varies significantly between the three clay minerals, and
the factors that dictate the complexation are completely different.
Depending upon the clay minerals, both surface-adsorbed and solution-phase
GenX are observed. Importantly, the interfacial structure, nearest
neighbor coordination, and dynamic behavior of GenX and their correlation
with legacy PFAS in minerals systems are presented.