Regenerable Graphene Nanoplatelet Adsorbents for Rapid and Trace-Level PFAS Removal from Water

Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic chemicals of global concern, and adsorption remains one of the most efficient methods for their removal from water. The present research reported a new kind of graphene nanoplatelets (GNP) modified by a cationic surfactant, cetyltrimethylammonium chloride (CTAC). This GNP-CTAC was observed to achieve nearly 100% capture of all 10 target PFAS, each at 10 μg/L in Milli-Q water. The pseudo-second-order model most accurately represented the adsorption kinetics, which was realized as a fast adsorption process in less than 1 min. The Sips isotherm model effectively fits the isotherm data, indicating that the adsorption of PFAS onto GNP-CTAC involved both heterogeneous surface sites and multilayer adsorption driven by combined electrostatic and hydrophobic interactions. The hypothesized adsorption mechanisms, including electrostatic and hydrophobic interactions, were validated by detailed physicochemical characterization. Remarkably, the performance of GNP-CTAC remained unaffected by variations in solution pH, ionic strength, natural organic matter, and nearly 100% removal effectiveness of PFAS in river water (surpassing conventional adsorbents like powdered activated carbon) at an initial PFAS concentration of 200 ng/L. Importantly, the adsorption performance of GNP-CTAC was successfully validated through a third-party evaluation. Along with its rapid adsorption of PFAS and stability across various water qualities, GNP-CTAC was also regenerable and could be reused for a minimum of four cycles, retaining most of its adsorption performance. Notably, stability evaluations confirmed that CTAC remained attached to the GNP surface during regeneration and adsorption, with no signs of surfactant leakage.