中文摘要：

利用液相还原与改进的Stbr法相结合,在不使用表面改性剂和氨水的条件下,通过向原硅酸乙酯（TEOS）和氯化铁混合溶液直接添加硼氢化钾,一步合成了二氧化硅包覆的纳米铁复合材料（Fe@SiO_2）.通过X射线粉末衍射（XRD）仪、能量色散X射线仪（EDAX）、透射电子显微镜（TEM）、紫外-可见（UV-Vis）吸收分光光度计、傅里叶红外（FTIR）光谱仪、X射线光电子能谱仪（XPS）等对所得样品的形貌、结构和组成进行表征.将制备的Fe@SiO_2用于水体中Cr（Ⅵ）还原去除并考察了TEOS添加量对其去除能力的影响.结果表明Fe@SiO_2具有清晰的核壳结构,多孔的SiO_2包裹1-2个球形纳米铁粒子.纳米铁粒径主要分布在20-30 nm之间,随着TEOS投加量的增加,SiO_2层变厚,纳米铁核具有更好的分散性.与未包覆型纳米铁相比,Fe@SiO_2对Cr（Ⅵ）的去除能力显著提高.TEOS投加量为0.1 mL所制备的Fe@SiO_3对Cr（Ⅵ）去除能力（以Fe的质量计算）达到量大,为466.67 mg·g~（-1）,而未包覆型纳米铁仅为76.35 mg·g~（-1）.

英文摘要：

Without using aqueous ammonia and a surface modifier,a facile one-step method was developed to fabricate Fe nanoparticles coated with a SiO_2 shell（Fe@SiO_2） by a modified Stober method combined with an aqueous reduction method.The Fe@SiO_2 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@SiO_2 for the reductive immobilization of Cr（VI） in water was studied.The influence of TEOS addition on Cr（VI） removal by Fe@SiO_2 was investigated.The results showed that the prepared Fe@SiO_2 had a distinct core-shell structure.One or two Fe nanoparticles（20-30 nm in diameter） were homogeneously coated by a porous SiO_2 shell.With an increase in the amount of added TEOS the Fe nanoparticles had better dispersion and the thickness of the SiO_2 coating increased gradually.Compared with uncoated Fe nanoparticles,Cr（Ⅵ） removal by Fe@SiO_2 increased greatly.At a TEOS dosage of 0.1 mL the removal ability of the prepared Fe@SiO_2 was the highest.The highest removal ability of Fe@SiO_2 was 466.67 mg·g~（-1） and it was only 76.35 mg·g~（-1） for uncoated Fe nanoparticles.