Preparation Of γ-Fe₂O₃ Nanopowder, γ-Fe₂O₃/SiO₂ Nanocomposite And Their Properties

Magnetic inorganic nanopowders attract much interest not only for many industrial applications but also from academic viewpoint. In addition, the magnetic inorganic nanopowders, especially iron oxide nanopowders, are widely used in the preparation of magnetic composites. In the present work, the studies concerned on the preparation, characterization and application of magnetic nanomaterials were carried out. The contents of the work involved the preparation and characterization ofγ-Fe2O3 nanopowder,mesoporousγ-Fe2O3 nanopowder andγ-Fe2O3/SiO2 nanocomposite, as well as the investigation of adsorption performance of these materials.Firstly, we have developed a novel method for the preparation of magneticγ-Fe2O3 nanopowder. The obtainedγ-Fe2O3 nanopowder was characterized using infrared (IR), scanning electron micrograph (SEM), transmission electron micrograph (TEM), X-ray powder diffraction (XRD), N2 adsorption-desorption (BET method) and vibrating-sample magnetometer (VSM). The average crystalline size of theγ-Fe2O3 nanopowder is estimated to be 24 nm; and, its specific surface area is determined to be 27 m2/g. Magnetic measurements show that theγ-Fe2O3 nanopowder exhibits ferromagnetic characteristics with a saturation magnetization (Ms) of 58.0 emu/g. The adsorption abilities of theγ-Fe2O3 nanopowder for the removal of methyl orange (MO) from waste water were also studied. The results show that theγ-Fe2O3 nanopowder exhibits relatively high adsorption capacity for MO although its specific surface area was not so large. The adsorption of MO on theγ-Fe2O3 nanopowder reaches the maximum adsorption rate within a few minutes; the maximum adsorption capacity is determined to be 454.6 mg/g. Mesoporousγ-Fe2O3 was also prepared by this method with the aid of a soft template (i.e., cetyltrimethyl ammonium bromide, CTAB), and its removal ability for MO was investigated. XRD and N2 adsorption-desorption measurements together with TEM observations show the formation of mesoporousγ-Fe2O3 with an average pore size of 3.5 nm and a specific surface area of 93.0 m2/g. Magnetic measurements show that the mesoporousγ-Fe2O3 shows ferromagnetic characteristics with a saturation magnetization of 54.5 emu/g. The maximum adsorption capacity of the mesoporousγ-Fe2O3 for MO is measured to be 384.6 mg/g, which suggests that the mesoporousγ-Fe2O3 could be an excellent magnetic adsorbent for MO.Secondly, magneticγ-Fe2O3/SiO2 nanocomposite was prepared successfully by sol-gel method, and it was characterized using IR,SEM,TEM,XRD,BET,VSM. At the same time, the adsorption capacity of the nanocomposite for MO was also investigated. The specific surface area of theγ-Fe2O3/SiO2 nanocomposite is 245.0 m2/g, which is almost one order larger than that of pureγ-Fe2O3 nanopowder. The average crystalline size of theγ-Fe2O3 contained in the nanocomposite is estimated to be 20 nm; and the saturation magnetization of the nanocomposite is 20.9 emu/g. The maximum adsorption capacity for MO is as large as 476.2 mg/g.