Multiple interactions steered high affinity toward PFAS on ultrathin layered rare-earth hydroxide nanosheets: Remediation performance and molecular-level insights

The global occurrence of per-and polyfluoroalkyl substances (PFAS) in aquatic systems has raised concerns about their adverse effects on ecosystems and human health. Adsorption is a promising technique for the remediation of PFAS, yet effective adsorbents with rapid uptake kinetics and high adsorption capacity are still in high demand, and molecular-level understanding of the interfacial adsorption mechanisms is lacking. In this study, we developed a superior layered rare-earth hydroxide (LRH) adsorbent, ultrathin Y-2(OH)(4.86)Cl(1.44 center dot)1 center dot 07H(2)O (namely YOHCl) nanosheets, to achieve the effective removal of perfluorooctanoic acid (PFOA). YOHCl nanosheets exhibited ultra-high adsorption capacity toward PFOA (up to 957.1 mg/g), which is 1.9 times and 9.3 times higher than the state-of-the-art layered double hydroxides (MgAl-LDH) and benchmark granular activated carbon (GAC) under the same conditions, respectively. Furthermore, YOHCl nanosheets pose stable performance on the removal of PFOA under various water matrices with robust reus-ability. We also developed YOHCl-based continuous-flow column, demonstrating its promise in simultaneously removing multiple PFAS with wide range of chain lengths at environmentally relevant concentrations. With the molecular-level investigations, we have revealed that multi-mechanism, including ion exchange, electrostatic attraction and bidentate/bridging coordination, contributed to the strong PFOA-YOHCl affinity, leading to the ultra-high adsorption capacity of PFOA. We have provided emerging LRHs-based adsorbents for the effective remediation of PFAS with molecular-level insights on the interfacial mechanisms.

Automated summary

The global occurrence of per- and polyfluoroalkyl substances (PFAS) in aquatic systems has raised concerns due to their adverse effects on ecosystems and human health. This study developed a highly effective and stable layered rare-earth hydroxide (LRH) adsorbent called YOHCl nanosheets for the removal of perfluorooctanoic acid (PFOA). The YOHCl nanosheets showed a significantly higher adsorption capacity for PFOA compared to other commonly used adsorbents under the same conditions. Molecular-level investigations revealed that multiple mechanisms contributed to the strong affinity between PFOA and YOHCl, leading to the high adsorption capacity.