Study On The Preparation And Adsorption Properties Of Alumina Of Controllable Morphology

Al2O3 is one of the most important industrial materials, which can be widely used as adsorbents, catalysts, catalyst supports, functional ceramics and reinforcements for composite materials abrasives due to its high specific surface area, good thermal stability,low cost and high dielectric constant. So the synthesis of Al2O3 with special microstructures and controllable morphologies has attracted much more attention in recent years. Herein, we have described a facile hydrothermal route to synthesis different morphologies Al2O3, by changing raw materials or surfactant, adjusting reaction temperature, reaction time, hydrolytic rateof aluminium source or other conditions. As-prepared products can be used as adsorbents for the quickly and effectively extract of congo red(CR) dye from wastewater. The main results are present as follows:(1) High purity stalk-like Al2O3 nanopowdershave been successfully synthesized employing a simple hydrothermal process, using aluminum nitrate as aluminum source, polyethylene glycol(PEG) as template agent and urea as additive. The effects of hydrothermal time on morphologies and microstructures of the samples were systematically investigated, and the formation mechanism of the samples with 3D stalk-like nanostructure is expected. The results showed that nanosheets tend to aggregate into 3D structure in the earlier stage. However, the Ostwald ripening process occurred with reaction further proceeding, which resulted in collapses of stalk-like structures. Batch adsorption experiments were conducted for removing azo-dye CR from aqueous solution. The impacts on adsorption performances of contact time, initial concentration and p H value of CR solution were further studied.(2) Al2O3 nanopowders with different hierarchical microstructures were successfully synthesized via a template-free hydrothermalmethod through adjusting the reaction time, using aluminum nitrate and urea as raw materials. The results indicated that reaction time has a big impact on the morphologies and microstructures of the samples. The formation mechanism of the samples with 3D flower-like nanostructures is expected by comparing the experiment results with the first chapter. As-prepared products can be used as adsorbents for the quickly and effectively extract of CR dye from wastewater. Experiment results suggested that all Al2O3 nanopowders are very promising materials for wastewater treatment.(3) Clew-like, nanorods and nanosheets, three different size-controlled Al2O3 nanopowders have been successfully synthesized via a reverse cation-anion double hydrolysis method without any additive, employing the starting material of Na Al O2 and Al(NO3)3·9H2O, Al Cl3·6H2O, Al2(SO4)3·18H2O. For this synthesis method, the hydrolysis reaction quickly proceeds to a complete extent in a real sense that other methods cannot achieve by mixing the stoichiometric amount of Al3 + and Al O2-, and evades the complicated p H adjusting process and the rather long hydrolysis period. These advantages render this method highly superior over the former ones for the industrial scaling-up.(4) Al2O3 hexagonal nanosheets have been successfully synthesized by a traditional hydrothermal method without any other additive, only using the organic aluminum source, aluminium isopropoxide, as raw material. This result denoted that the new nanostructure can be obtained by using aluminium isopropoxide, and the sample still possessed remarkable ability to remove CR pollutant from waste water.