Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.
Environ Sci Technol. 2022 Jun 21;56(12):8043-8052. doi: 10.1021/acs.est.2c01054. Epub 2022 May 11.
The ubiquitous presence of poly- and perfluoroalkyl substances (PFAS) in different natural settings poses a serious threat to environmental and human health. Soils and sediments represent one of the important exposure pathways of PFAS for humans and animals. With increasing bioaccumulation and mobility, it is extremely important to understand the interactions of PFAS molecules with the dominant constituents of soils such as clay minerals. This study reports for the first time the fundamental molecular-level insights into the adsorption, interfacial structure, and dynamics of short- and long-chain PFAS molecules at the water-saturated mesopores of kaolinite clay using classical molecular dynamics (MD) simulations. At environmental conditions, all the PFAS molecules are exclusively adsorbed near the hydroxyl surface of the kaolinite, irrespective of the terminal functional groups and metal cations. The interfacial adsorption structures and coordination environments of PFAS are strongly dependent on the nature of the functional groups and their hydrophobic chain length. The formation of large, aggregated clusters of long-chain PFAS at the hydroxyl surface of kaolinite is responsible for their restricted dynamics in comparison to short-chain PFAS molecules. Such comprehensive knowledge of PFAS at the clay mineral interface is critical to developing novel site-specific degradation and mitigation strategies.
多氟和全氟烷基物质（PFAS）在不同自然环境中的普遍存在对环境和人类健康构成了严重威胁。土壤和沉积物是人类和动物接触 PFAS 的重要途径之一。随着生物累积和迁移性的增加，了解 PFAS 分子与土壤主要成分（如粘土矿物）的相互作用极其重要。本研究首次利用经典分子动力学（MD）模拟，在水饱和的高岭石中报道了有关短链和长链 PFAS 分子在介孔中的吸附、界面结构和动力学的基本分子水平见解。在环境条件下，所有的 PFAS 分子都仅被吸附在高岭石的羟基表面，而与末端官能团和金属阳离子无关。PFAS 的界面吸附结构和配位环境强烈依赖于官能团的性质及其疏水性链长。与短链 PFAS 分子相比，长链 PFAS 在高岭石羟基表面形成大的、聚集的簇，导致其动力学受限。这种对粘土矿物界面上 PFAS 的全面了解对于开发新型特定地点的降解和缓解策略至关重要。
