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

Abstract

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.

Impact of Variable Water Chemistry on PFOS-Goethite Interactions: Experimental Evidence and Surface Complexation Modeling

“…Thus, there is a need for mechanistic sorption prediction models that can precisely assess PFOS mobility in the environment under dynamic water chemistry conditions and electrostatic properties of the surface–solution interface. Such models can also benefit from increasingly available molecular-level insights on adsorption of per- and polyfluoroalkyl substances (PFAS) provided by spectroscopic analyses and molecular dynamics simulations. − …”

Binding of Per- and Polyfluoroalkyl Substances (PFAS) to the PPARγ/RXRα–DNA Complex

“…Per- and polyfluoroalkyl substances (PFAS) are a group of chemical compounds used as fluoropolymers, which have industrial applications ranging from coatings, adhesives, firefighting foam, to oil repellants, due to their high heat resistance. − PFAS are considered “forever chemicals” due to their resistance to degradation , and their persistence in the environment (soil and water) , as well as in humans and animals (see e.g., refs , ). To illustrate their prevalence, in the U.S., it is estimated that PFAS can be found in more than 99% of the population .…”