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, beta-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 electron 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, beta-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 pi-pi 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.