Metal-powder/Pure-water Hydrothermal Method To Prepare Metallic Oxide, And Their Characterization And Performance

Metallic oxide (MOx) nanostructures not only has the characteristics of metal oxide,but also has properties of nanomaterials such as high specific surface area, strong lightabsorption and strong adsorption ability, it is widely used in fields of self-cleaningmaterials, catalyst and carrier, electronics, foods, biology and medical science. Thepreparation of MOxnanostructures includes gas-phase methods, solid-phase methodsand liquid-phase method. As one of liquid-phase methods, the hydrothermal method hasbecome a commonly used method for the preparation of MOxnanostructures, becauseof its simple operation, moderate condition, and its product generally with a narrowparticle size distribution, less particle aggregation and certain morphology. However,there are disadvantages such as low-purity and trival subsequent processing.In order to make up the defect of the commonly used hydrothermal method, on thebasis of preliminary wore of the laboratory, this paper present metal/pure-waterhydrothermal oxidation. We adopted zinc-powder (or iron-powder)/pure-waterhydrothermal oxidation prepared the target products, nano-ZnO, nano-Fe3O4. Thecrystal structure, morphology, optical property, elements, valence band structure andmagnetic property of samples were characterized by X-ray diffraction (XRD), fieldemission scanning electron microscopy (FE-SEM)， transmission electronmicroscopy(TEM), photoluminescence spectrum(PL), Fourier transform infraredspectroscopy(FTIR), X-ray photoelectron spectroscopy (XPS), UV-Vis diffusereflection spectrum (UV-Vis DRS) and hysteresis loop (B-H loop), respectively. Further,the (photo)catalytic activity of the MOxnanostructures is investigated.The ZnO nanoparticles are prepared by zinc-powder/pure-water hydrothermaloxidation. The influence of hydrothermal time to the characters and catalytic property isinvestigated using the samples as the model object, which are prepared by thehydrothermal oxidation for18h(ZnO-18h),36h(ZnO-36h),72h(ZnO-72h), respectively.The results of XRD and TEM show that all the products are nanoparticles withhexagonal wurtzite structure. The green light emitting of ZnO nanoparticles wasprobably caused by the oxygen vacancies, the density of Oxygen vacancy is decreased,along with the growth of the hydrothermal time. The result of X-ray photoelectronspectroscopy indicated that there is no impurities in the samples. O1s suggests that theconcentration of oxygen vacancies were reduced when the hydrothermal time increased.It is consistent with the result of photoluminescence spectra. The valence band spectra show that the valence-band top shift down according to the hydrothermal time growth.The width of forbidden band narrowing, along with the growth with time, displayed bythe ultraviolet diffuse. These samples show excellent photocatalytic performance in thedegradation of organic pollutants when irradiated with UV lamp, and show a highperformance in reutilization. The photocatalytic performance of ZnO nanoparticles iswell, when high pressure mercury lamp as the light source, but there was a slightdecrease of the degradation efficiency, along with the growth of the hydrothermal time.This may be related to the density of oxygen vacancy.We adopted iron-powder/pure-water hydrothermal oxidation prepared thenano-Fe3O4, the various characters of Fe3O4nanoparticles and the catalytic performanceto antibiotics degradation of the Fe3O4/H2O2system were studied. The results of XRDand FESEM show that the Fe3O4nanoparticles are magnetite structure, with an averageparticle size of100nm. The strong absorption peak at the wave number of518cm-1wascaused by the stretching vibration of Fe-O-Fe. XPS showed that there was very smallamount of FeOOH may exist. The magnetic test shows that the saturation magnetization(Ms), remanent magnetization (Mr) and coercive force (Hc) of the sample is96.66emu/g,25.13emu/g,250.56Oe, respectively. These magnetic parameters are higher than thesimilar ferroferric oxide nanomaterials, even the bulk magnet. So it is easy to recyclingthe nanoparticles. The Fe3O4/H2O2system shows a good catalytic performance to thedegradation of antibiotics, the degradation efficiency can reach91.73%within1h. TheXRD of the reclaimed nano-Fe3O4shows no obvious change, compared with the resultbefore catalytic reaction, it is possible to reuse for many times.