Nanosized Fe3O4/SiO2 core-shells fabricated from natural sands, magnetic properties, and their application for dye adsorption

Abstract

This work presents Fe₃O₄/SiO₂ core-shell fabrication. Silica (SiO₂) nanoparticles (NPs) were prepared from silica sand using a continuous method, and Fe₃O₄ NPs were prepared from iron sand using the co-precipitation route. For Fe₃O₄/SiO₂ core-shell fabrication, we used the wet mixing method, where the composition of Fe₃O₄ and SiO₂ NPs was varied, and polyethylene glycol (PEG) was used as a binder. With an in-situ technique, tetraethyl orthosilicate (TEOS) was used as the SiO₂ precursor to coat the surface of the Fe₃O₄ NPs and the mass ratio of SiO₂ and Fe₃O₄ NPs was modified by varying the composition of the TEOS. The samples were characterized as follows: the structure, functional groups, particle size, morphology, and the magnetic property of Fe₃O₄/SiO₂ was characterized via X-ray diffraction, energy dispersive X-ray, Fourier transform infrared, scanning electron microscopy, and vibrating sample magnetometer, respectively, and porosity analysis was conducted. The Fe₃O₄/SiO₂ composites were successfully synthesized using wet mixing and in situ methods. Specifically, the diffraction peaks show PEG (2θ»19° and 23°) for samples prepared using the wet mixing technique. The presence of PEG in the Fe₃O₄/SiO₂ composites reduced the saturation magnetization of the Fe₃O₄ NPs significantly from 29.5 to 9.0 emu/g when synthesized using the wet mixing method, and from 29.5 to 19.8 emu/g when synthesized using in the situ method. Furthermore, the increasing SiO₂ NPs composition reduced the shell wall thickness significantly and enhanced the adsorption porosity of the Fe₃O₄/SiO₂ core-shells. The higher SiO₂ content led to a decrease in the porous volume of the Fe₃O₄/SiO₂ core-shells.