Preparation Of Magnetite Nanoparticles And Their Properties

Magnetic iron oxide nanopowder has been widely used in many applications such as magnetic recording, catalysis, ferro-fluids, microwave absorbent and biomedical field. Therefore, the studies on nano-sized magnetic particles have become one of the most interesting research areas. Recently, although many synthesis methods have been reported for magnetic iron oxide nanopowder, the development of production technology which can satisfy the industrial needs is still a challenging research subject. Therefore, an easy and environment-friendly synthetic method attracts much attention. In the present work, magnetite (Fe3O4) nanopowder was synthesized by thermal decomposition method and solvothermal synthesis method using Fe-urea complex as raw materials. The main advantages of these methods are(1) the preparation procedure of Fe3O4 nanopowder is simple, (2)the precursor, [Fe(CON2H4)6](NO3)3, a nontoxic material, can be easily synthesized form readily available Fe(NO3)3·9H2O and CON2H4,and (3) the solvent, C2H5OH, is an environment-friendly and most commonly used solvent.Fe3O4 nanopowder was synthesized by thermal decomposition method using Fe-urea complex as raw materials. The synthesized Fe3O4 nanopowder was characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), transmission electron micrograph (TEM), N2 adsorption-desorption (BET method) and magnetic measurements. The result shows that the average crystallite size of Fe3O4 nanopowder is in 20～100 nm, and they possess ferromagnetic characteristics. The average crystallite size and saturation magnetization of the Fe3O4 nanopowder increases with the increase of reaction temperature and reaction time. This suggests that the crystallite size and magnetic properties of the Fe3O4 nanopowder can be controlled by varying the reaction temperature and reaction time.Fe3O4 nanopowder was also synthesized by solvothermal synthesis method using Fe-urea complex as raw materials and ethanol as solvent. The synthesized Fe3O4 nanopowder was characterized by XRD, IR spectroscopy, XPS, TEM, N2 adsorption-desorption and magnetic measurements. The average crystalline size of the Fe3O4 nanopowder is estimated to be 10 nm; and, its maximum specific surface area is determined to be 136m2/g. The Fe3O4 nanopowder has a mesoporous structure and superparamagnetic characteristics. The average crystallite size and saturation magnetization of the Fe3O4 nanopowder increases with the increase of reaction time, indicating that the crystallite size and magnetic properties of the Fe3O4 nanopowder can be controllable.In this paper, the adsorption abilities of Fe3O4 nanopowder for Cr(Ⅵ) were also studied. The Fe3O4 nanopowder has a high removal ability for Cr(Ⅵ), such as the fast adsorption rate and the high adsorptive capacity. The adsorption of Cr(Ⅵ) on Fe3O4 nanopowder reaches the maximum adsorption rate within 30 minutes, and the adsorption rate of Cr(Ⅵ) fits well with bangham adsorption rate equation. The adsorption capacity for Cr(Ⅵ) increases with the increase of initial concentration of Cr(Ⅵ) and gradually trend to saturation; and, the maximum adsorption capacity is determined to be 15.5mg/g. The adsorption capacity and adsorption rate for Cr(Ⅵ) increase with the decrease of solution pH. The adsorption of Cr(Ⅵ) on Fe3O4 nanopowder can be well described using Langmuir and Freundlich adsorption models, and the Fe3O4 nanopowder can be reusable.