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Surface-engineered anisotropic Fe3O4 nanoplates for highly efficient magnetic field-assisted micro/nanoplastics remediation
Summary
Researchers developed surface-engineered anisotropic magnetite (Fe3O4) nanoplates coated with SiO2 for highly efficient magnetic field-assisted removal of micro- and nanoplastics from aqueous environments. The anisotropic nanoplate architecture provided greater surface area and improved magnetic responsiveness compared to conventional spherical particles, enabling efficient capture and separation of plastic particles across a range of sizes and polymer types.
Micro- and nanoplastics (MNPs) are emerging contaminants of global concern, but their efficient removal from aqueous environments poses a critical challenge. This paper reports the development of anisotropic magnetite nanoplates (MNPLs) coated uniformly with SiO to yield MNPL@SiO as highly efficient magnetic nanoharvesters for MNPs. Engineering the SiO surface with aminopropyl (NH-), octadecyl (C-), and phenylethyl (Ph-) groups to tune the electrostatic, hydrophobic, and π-π interactions enabled optimally functionalized MNPL@SiO to show rapid and highly efficient MNPs remediation, with 93.4 %, 92.1 %, and 94.3 % removal efficiencies (REs) for 100 nm, 500 nm, and 1 μm polystyrene (PS) MNPs, within 10 min under magnetic field-assisted conditions. The mechanistic insights were obtained through a systematic evaluation of the MNPs removal kinetics and isotherms. The kinetic data followed a pseudo-second order model, indicating chemisorption driven by electrostatic interactions, while equilibrium adsorption isotherms conformed to the Langmuir model with high sorption capacity (∼3630.2 mg/g), outperforming many reported nanostructured adsorbents. In addition to classical adsorption, a secondary mechanism-dynamic trapping-was uncovered when plate-like MNPL@SiO aggregated into hierarchical architectures under a magnetic field that physically entrap unadsorbed MNPs within the void spaces. Dynamic trapping contributed significantly to RE enhancement, where an additional 18.2 % removal was shown. Reusability assessments confirmed that NH-MNPL@SiO retained promising activity across multiple cycles after solvent cleaning. These findings highlight the synergistic contributions of shape anisotropy, surface engineering, and magnetic field-assisted dynamic trapping in MNPs removal, providing new mechanistic insights and offering a scalable approach for rapid, efficient, and sustainable water remediation applications.