(346f) Experimental and Computational Evaluation of the Interaction between per- and Polyfluoroalkyl Substances with Microplastics in Aqueous Systems

Per- and polyfluoroalkyl substances (PFAS) are surface-active compounds composed of alkyl fluorinated hydrophobic tails, applied as industrial surfactants mainly due to their chemical stability. The development of health problems like diabetes, high cholesterol, cardiovascular disease, thyroid, kidney, and immune system dysfunctions have been recently linked to long-term human exposure to PFAS, such as perfluorooctane sulfonate (PFOS). In order to develop a better understanding of the fate of these molecules in aqueous systems, it is important to quantify the interaction of these molecules with different microplastic species. Here, we experimentally assess the adsorption behavior of PFOS in aqueous media onto the surfaces of polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC). The experimental behavior is further analyzed using molecular dynamics simulations to calculate the PFAS superficial properties, such as the PFAS-PFAS virial coefficient and transfer free energy, in which PFAS molecules with different alkyl sizes are evaluated. The adsorption mechanism of four different perfluorooctyl PFAS molecules on PE, PP, and PVC nanoplastic particles is evaluated by inspecting the potential-of-mean-force of pulling the PFAS molecules from the aqueous bulk phase to the plastic-water interfacial region. The molecular simulation results suggest a pronounced dispersive interaction between the polymer and PFAS molecules for PE and PP; while the dispersive interaction dominates the PVC systems, as compared to PE and PP, a much stronger coulombic PFAS-PVC interaction is found. Overall, evaluating the relevant molecular features involved in the adsorption of aqueous phase dispersed PFAS molecules, as performed in this work, is essential in understanding the lifecycle of PFAS transport and designing novel polymetric adsorbent materials.