Efficient removal of typical perfluorinated compounds using NH2-MCM-41: Insights into adsorption mechanisms

Perfluorinated compounds (PFCs), which were difficult to biodegrade and posed significant ecological and health risks, had made their removal an urgent global challenge. Herein, NH₂-MCM-41 was designed by modifying MCM-41 with 3-aminopropyltriethoxysilane (APTS) to remove PFOA, PFOS and OBS. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) results indicated that though the implanting of NH₂– on MCM-41 decreased S_BET and pore size, but it dramatically increased the PFOA, PFOS and OBS adsorption capacity. The maximum uptake y capacity of NH₂-MCM-41 increased from 14.41 to 350.61, 19.53 to 445.11, and 28.6 to 452.98 mg/g for PFOA, PFOS and OBS, respectively. Three PFCs adsorptions were more favorable under acidic condition. Both the pseudo-second-order and intra-particle diffusion models provided a good fit for the kinetic data, and the adsorption isotherms were well described by the Langmuir and Freundlich models. The primary adsorption mechanisms involved hydrophobic interactions, electrostatic forces, H bond interaction and micellar or sub-micellar effects. This study demonstrated valuable insights into the applicability of NH₂-MCM-41 for environmental remediation.