Studying On The Reproduction Of Waste Activated Alumina

Large amount of waste activated alumina is produced during catalytic and adsorption processes in many chemical industries. Heat-treatment and hydrogen nitrate dipping methods were used to reproduce the waste by modifying the inner pore structures in this paper. Comparing to the traditional way, this project has high social and economic benefits owing to the very low cost and high quality. X-ray diffraction and Scanning electron microscopy were used to characterize the crystalline phases and microstructures. ASAP2010 specific surface area analyzer has been used to calculate the specific surface area and, pore volume and its distribution. The samples were undergone watering and drying processes before sintering at different temperatures and time. The influences of different heat treatment routines on the physical properties, crystal phases and microstructures were discussed. The results show that 2 kinds of interstitial solid solutions((Al2Q3)i.33 and AI2.85O3. 45N0.55) were formed with cubic Fm3m and Fd3m space group respectively. The specific surface area is decreasing with time increases when temperature higher than 550. At the same temperature, the specific surface area is also decreasing with time increases. By synthetical analysis, the optimum calciantion temperature is 550, sintering time is 2h. Under such condition, the specific surface area is up to 242.2m2/g, pore volume reaches to 0.46cm3/g and pore diameter reaches to 7.1 lnm. According to hydrogen nitrate dipping procedure, the samples must undergo water clearing drying hydrogen nitrate dipping water clearing drying calcination procedures. Hydrogen nitrate is used as active and plastering agents, they could expand the pore and improve the specific surface area. The influences of different hydrogen nitrate concentrations, dipping time, calcination temperatures and sintering time on the samples' physical properties, crystal phase and micro structures were investigated. The results show that only one crystalline phase: (Al2O3)i.33 interstitial solid solution is formed in each sample. The specific surface area is decreasing with hydrogen nitrate concentration increases when its range from 8% to 14%, but when it ranges from 16% to 20%, the changing laws is reverse. The influences of time on the specific area is discussed. By synthetical analysis the optimum treat conditions are: hydrogen nitrate concentration: 8%. dipping time: lOmin, calciantion temperature: 500, sintering time: 2h. Under such conditions, the specific surface area is up to 251.97m2/g which is even higher than the untreated sample. The results show that the reproduced active alumina have good properties which is comparable or superior to commercial products. The treated samples are applied in regeneration of working solution of hydrogen peroxide, the results shows the capability of regeneration are better than the unused alumina, the activity is higher than YI2O3...