Synthesis Of Micro/Nanostructured Metal Oxide Materials And Their Application In Water Treatment

In recent years, the applications of metal oxide materials in wastewater treatment appear particularly important development prospects. The main reason is that the materials in wastewater treatment have their unique advantage. These unique advantages mainly have the following features:i) be of low cost, which can be achieved by using low cost materials and by following effective and low-cost synthesis methods; ⅱ) possess a robust and strong mechanical structure that can sustain water flow for extended periods of time; ⅲ) exhibit high removal capacities and fast adsorption/photocatalytic reaction rates for contaminations. With the continuous development of nanotechnology, the metal oxide materials with micro/nano structures can further demonstrate the advantages. Their micrometer-sized overall structure provides the necessary mechanical robustness against wear and tear; while their nanostructure provides the high surface area as well as the high removal capacity for contaminations. Another remarkable advantage of micro/nano structures is that the mass transportation is facile. In this dissertation, some metal oxide materials with novel micro/nano structures have been prepared, and further been investigated their applications in wastewater treatment. The main contents and novelties are summarized as follows:1. The fried egg jellyfish-like γ-AlOOH(Boehmite)@SiO2/Fe3O4micro/nanospheres with a unique porous structure were synthesized by a simple method. The sample possesses a high BET surface area and more pore channels. The product also displays excellent magnetic properties at room temperature. The as-prepared microspheres were employed in the adsorbtion of Pb(Ⅱ), which shows that they have an ultra high adsorption capacity (the maximum adsorption capacity (qm) is about214.59mg g-1for Pb(Ⅱ)) and efficiency (when the initial concentration of Pb(II) is lower than100mg g-1, the removal efficiency is about100%), All of these splendid properties mean that the as prepared micro/nanospheres can be used as novel, highly efficient and fast separation sorbents for the removal of heavy metal ions from waste water.2. For the first time, a simple, economical and environmentally friendly hydrothermal method has been successfully used to synthesize self-assembled, monodispersed, uniform, and flower-like y-AlOOH micro/nano structures, employing deionized water as a solvent and NaAlO2and urea as reagents in the presence of polyacrylic acid sodium salt as surfactant. The reaction mechanism and the self-assembly evolution process were studied. The product possesses a large BET surface area of145.5m2g-1and a large number of pore channels. It is found that Pb(Ⅱ) and Hg(Ⅱ) ions can be quickly removed from aqueous solutions by the flower-like y-AlOOH micro/nano structures. After only5min, the removal rate for Pb(Ⅱ) and Hg(Ⅱ) ions is over99.0%. The maximal adsorption is ca.124.22mg g-1for Pb(Ⅱ) and131.23mg g-1for Hg(Ⅱ). All of these splendid properties mean that the product can be used as a highly efficient sorbent for the removal of heavy metal ions from waste water.3. A simple, green, efficient method has been successfully used to synthesize the uniform Ag-coated Fe3O4@TiO2micro/nanospheres. The sample has a high BET surface area, a large number of pore channels, and excellent magnetic properties at room temperature. Ag nanoparticle loading can be controlled by the UV photoreduction time; the photo catalytic activity reached a maximum when the exposure time was5h. It was demonstrated that the rate of photodegradation of Methylene blue is superior to that of Degussa P25titania and uncoated Fe3O4@TiO2micro/nanospheres, which is attributed to the Ag-TiO2heterojunction of the Ag-coated Fe3O4@TiO2micro/nanospheres. After recycling the photocatalyst five times for Methylene blue photodegradation, the degradation reaction rate constant of the Ag-coated Fe3O4@TiO2micro/nanospheres was stable. This means that the as-prepared composites can be used as convenient, recyclable photocatalysts for removing organic pollutants from waste water.