Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in aquatic environments around the world. In recent years, the enrichment of PFAS on the surface of nanobubbles on adsorbents has been proposed, but no direct evidence has been provided to support this new adsorption mechanism. In this study, we used density functional theory (DFT) and molecular dynamics (MD) to simulatively investigate the contribution of nanobubbles for PFAS adsorption on the pristine and functionalized graphene (GR). The adsorption energy of PFAS on GR-NH₂ was higher than that of GR-OH, while GR showed the lowest adsorption energy. When the effect of water molecules was considered, the oleophobic property of the C–F chain made it difficult for hydrophobic interaction to be involved in the adsorption of PFAS on nonpolar GR. With the existence of nanobubbles, both GR and GR-NH₂ can effectively remove PFAS, but their adsorption mechanisms were quite different. For hydrophobic GR, the nanobubbles initially attached to the surface of materials played a major role, while for hydrophilic GR-NH₂, the nanobubbles dispersed in the solution were more important. Moreover, the nanobubbles had a more significant contribution to long-chain PFAS. Our degassing and aeration experiments could support the simulation results. The removal of PFOS decreased by 27.7% at maximum after degassing and increased by 21.0%–29.2% after aeration. The study could provide a theoretical basis for the environmental process and contamination control of PFAS at the solid–liquid interfaces.

中文翻译：

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纳米气泡对石墨烯和 OH 和 NH2 功能化石墨烯 PFAS 吸附的贡献：模拟与实验结果的比较

全氟和多氟烷基物质 (PFAS) 在世界各地的水生环境中无处不在。近年来，有人提出在吸附剂上的纳米气泡表面富集 PFAS，但没有提供直接证据来支持这种新的吸附机制。在这项研究中，我们使用密度泛函理论 (DFT) 和分子动力学 (MD) 来模拟研究纳米气泡对原始和功能化石墨烯 (GR) 上 PFAS 吸附的贡献。PFAS对GR-NH ₂的吸附能高于 GR-OH，而 GR 表现出最低的吸附能。当考虑水分子的影响时，C-F 链的疏油特性使得疏水相互作用难以参与 PFAS 在非极性 GR 上的吸附。由于纳米气泡的存在，GR和GR-NH ₂都可以有效去除PFAS，但它们的吸附机制却大不相同。对于疏水性 GR，最初附着在材料表面的纳米气泡起主要作用，而对于亲水性 GR-NH ₂，分散在溶液中的纳米气泡更为重要。此外，纳米气泡对长链 PFAS 的贡献更为显着。我们的脱气和曝气实验可以支持模拟结果。脱气后PFOS的去除量最大减少27.7%，曝气后增加21.0%~29.2%。该研究可为固液界面PFAS的环境过程和污染控制提供理论依据。