Construction And Performance Evaluation Of Fe 3 O 4 Based Magnetic Nanocomposites

Owing to its unique optical, electrical, and magnetic properties, nanocomposites have wide applications in water treatment, energy storage, biochemistry and so on. In this paper, Fe₃O₄/activated montmorillonite nanocomposites, Fe₃O₄ nanofibers and Fe₃O₄ nanowire@CeO₂/Ag nanocomposites were fabricated and synthesized using the hydrothermal and co-precipitation methods. Finally, their applications either in water treatment or energy storage are investigated. The main research contents and results are as follows:?1? Fe₃O₄/activated montmorillonite ?Fe₃O₄/Mt? nanocomposites were prepared by a coprecipitation method. The morphology and structure of the Fe₃O₄/Mt nanocomposites are explored using X-ray powder diffraction, Fourier transform infrared spectroscopy, N2 adsorption-desorption isotherms and scanning electron microscopy. The adsorption capacity of Fe₃O₄/Mt for methylene blue ?MB? was evaluated. Within 25 min, the Fe₃O₄/Mt nanocomposite ?0.5 g? removed 99.47% of the MB from a 120 mg L"1 solution at 293 K and at a original solution pH of 7.37. The experimental adsorption data followed a pseudo-second-order kinetic model and Langmuir isotherm and the adsorption was a spontaneous, exothermic process. The reusability of the Fe₃O₄/Mt was tested and still over 83.73% color removal of MB was obtained after five cycles. The Fe₃O₄/Mt has good stability and reusability.?2? One dimensional Fe₃O₄ nanofibers with average diameters of about 1 ?m and average lengths of about 25?m were prepared by hydrothermal synthesis in the presence of sodium citrate and characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The results show that Na3cit was used as a capping agent in the formation of the Fe₃O₄ nanofibers and the Fe₃O₄ crystal nuclei were generated from different Fe2+-citrate complexes under hydrothermal conditions. These nanocrystals then further grew along the{110} axis and on the exposed ?111? facet. The Fe₃O₄ nanocrystals formed larger nanostructures via an oriented attachment mechanism during the collisions. PVP was more conducive to nanofibers growth in comparison to PEG-4000, CTAB and SDS. The electrochemical properties show that the Fe₃O₄ nanofibers had a specific capacitance of 117.6 F g^-1 as well as good cycling performance.?3? Ternary magnetic Fe₃O₄ nanowire@CeO₂/Ag nanocomposites have been firstly synthesized by means of hydrothermal and co-precipitation techniques. The morphology and structure of the Fe₃O₄ nanowire@CeO₂/Ag nanocomposites are explored using X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption-desorption isotherms, etc. The results show that Ag and CeO₂ nanoparticles are uniformly deposited on the surface of Fe₃O₄ nanowires. The photocatalytic experiments demonstrate that the Fe₃O₄@CeO₂/Ag nanocomposites exhibit remarkably enhanced photocatalytic properties compared with CeO₂, CeO₂/Ag, Fe₃O₄@CeO₂ under natural sunlight exposure, the degradation efficiency of MB is 94.1%. Moreover, the photocatalytic degradation efficiency of phenol and MO are 83.9% and 74.2%, respectively. The enhanced photocatalytic performance may be attributed to the synergetic effect of CeO₂, Ag and Fe₃O₄ nanowire, which lead to the enhanced light harvesting, the promoted charge separation and enhanced adsorption capacity. The reusability of the Fe₃O₄@CeO₂/Ag was tested and still over 93.1% degradation efficiency of MB was obtained after five cycles.In addition, the Fe₃O₄@CeO₂/Ag photocatalyst can be easily collected and separated by an external magnet.