Study on High-Purity Alumina Preparation and Its Applications =Étude sur la préparation de l'alumine de haute pureté et ses application

Wastewater from different aluminum processing plants contains different surface treatment liquids. These liquids are strictly prohibited from being discharged directly into the environment due to their high acidity. Different factories and enterprises add water to dilute them or neutralize them with alkali. These approaches not only cause a part of the aluminum ions being discharged, but also result in the release of a large number of harmful metal ions and heavy metal ions. In such cases, a large amount of water and alkali are consumed; at the same time, surface water, groundwater and soil become polluted by a large volume of wastewater and different metal ions.;The main objectives of the project are: 1) to extract ultra-pure aluminum ions from wastewater and to study the effect of different parameters on the efficiency of the process; 2) to produce ultra-pure nano-alumina from wastewater using an organic template and to study the effect of different parameters on the particle size distribution as well as on the morphology of the nanoparticles; 3) to explore the possibility of different applications for different types of alumina particles.;In this work, aluminum was extracted from the wastewater in the form of alum. This aluminum alum solution was later used to produce 99.999% pure (5N) nano-alumina particles. Two different methods, namely single and double template methods, were used to control the size and the nature of the alumina particles.;A single template method was used to produce 99.999% pure (5N) spherical alumina nanoparticles. The aluminum alum solution was hydrolyzed to produce boehmite which was used to produce the spherical alumina nanoparticles. Gum arabic and urea were used to produce the single template. These alumina nanoparticles were converted to alpha (alpha) form by heating. Then, the alpha-alumina particles were used to produce sapphire crystals.;An evaporation-induced synthesis approach with double template was used to produce spherical mesoporous nanoparticles of uniform size distribution. These particles were used for the photoacoustic tomography. The originality of the project lies in the utilization of new sources of raw materials (wastewater from industries) and using chelating polymers as well as additives to develop a novel and environment friendly high purity alumina (HPA) production method. In addition, the alumina particle size and its distribution are controlled precisely, which is difficult to achieve with other alumina production methods.