One-Step Synthesis of Fe@SiO<sub>2</sub> and Its Application in Cr(VI) Removal

Abstract

Without using aqueous ammonia and a surface modifier, a facile one-step method was developed to fabricate Fe nanoparticles coated with a SiO2 shell (Fe@SiO2) by a modified Stober method combined with an aqueous reduction method. The Fe@SiO2, was prepared by directly adding potassium borohydride to a mixed solution of tetraethylorthosilicate (TEOS) and anhydrous ferric chloride. The structure and morphology of the as-synthesized powders were investigated by X-ray powder diffraction (XRD), energy dispersion analysis of X-ray (EDAX), transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) absorption spectroscopy, Fourier-transform infrared (FTIR) spectrometry and X-ray photoelectron spectroscopy (XPS). The feasibility of using the prepared Fe@SiO2 for the reductive immobilization of Cr(VI) in water was studied. The influence of TEOS addition on Cr(VI) removal by Fe@SiO2 was investigated. The results showed that the prepared Fe@SiO2 had a distinct core-shell structure. One or two Fe nanoparticles (20-30 nm in diameter) were homogeneously coated by a porous SiO2 shell. With an increase in the amount of added TEOS the Fe nanoparticles had better dispersion and the thickness of the SiO2 coating increased gradually. Compared with uncoated Fe nanoparticles, Cr(VI) removal by Fe@SiO2 increased greatly. At a TEOS dosage of 0.1 mL the removal ability of the prepared Fe@SiO2 was the highest. The highest removal ability of Fe@SiO2 was 466.67 mg . g(-1) and it was only 76.35 mg . g(-1) for uncoated Fe nanoparticles.