Fe₃O₄@ZIF-8@SiO₂ Core–Shell Nanoparticles for the Removal of Pyrethroid Insecticides from Water

Residues of pyrethroid pesticides in aquatic environments seriously threaten aquatic organisms and the human health. Herein, a novel highly dispersed and recyclable composite ZIF-8 and SiO₂ double-layer-modified Fe₃O₄ nanoparticle, named Fe₃O₄@ZIF-8@SiO₂ nanoparticle, was synthesized via a layer-by-layer assembly method to remove pyrethroid insecticides (namely, fenvalerate, β-cyfluthrin, and tetramethrin) from water. The physical properties of the Fe₃O₄@ZIF-8@SiO₂ nanoparticles were characterized via scanning electron microscopy, elemental mapping, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma spectroscopy, thermogravimetric analysis, Brunauer–Emmett–Teller surface area analysis, dispersion analysis, and vibrating sample magnetometry. The prepared Fe₃O₄@ZIF-8@SiO₂ nanoparticles exhibited excellent adsorption performance and high dispersibility and could be rapidly separated from water using an external magnetic field. The Fe₃O₄@ZIF-8@SiO₂ nanoparticles exhibited the strongest adsorption effect at an adsorbent dosage of 10 mg, an adsorption time of 40 min, and a pH of 7. The fitted model for the adsorption process was consistent with the proposed secondary kinetic model and Sips isotherm model. The Fe₃O₄@ZIF-8@SiO₂ nanoparticles exhibited maximum adsorption capacities of 316.23, 364.43, and 258.69 mg g^–1 for fenvalerate, β-cyfluthrin, and tetramethrin, respectively. The Fe₃O₄@ZIF-8@SiO₂ nanoparticles retained most of their adsorption capacity after five reuse cycles when acetone was used as an eluent for desorption. The mechanisms involved in the adsorption process included π–π stacking interactions, hydrogen bonds, hydrophobic interactions, and pore filling effects. This study provides a potential design for rapidly recoverable and reusable nanoparticles that can be used to effectively adsorb pyrethroid insecticides in wastewater.