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). According to the DFT calculation, the adsorption energy of PFAS on GR-NH2 was higher than that of GR-OH, while GR showed the lowest adsorption energy. As for MD simulation, the models with gas-liquid-solid three-phases were established. 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 can enrich PFAS and then the electrostatic attraction between the positively charged amino groups and PFAS anions can connect the nanobubbles with the materials. 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.

Contribution of nanobubbles for PFAS adsorption on graphene, OH- and NH<sub>2</sub>-functionalized graphene: Comparing simulations with experimental results

ACS Spring 2022

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Contribution of nanobubbles for PFAS adsorption on graphene, OH- and NH2-functionalized graphene: Comparing simulations with experimental results

Contribution of nanobubbles for PFAS adsorption on graphene, OH- and NH₂-functionalized graphene: Comparing simulations with experimental results