中国有色冶金

Secondary aluminum ash contains a large amount of Al, Al₂O₃, as well as a certain amount of MgAl₂O₄ and AlN. Direct storage would cause environmental pollution and waste of resources. However, Al, AlN and some impurities in aluminum ash can be dissolved under alkaline leaching conditions, and the remaining residue composition is relatively close to that of magnesium-aluminum spinel material (MA). In this study, secondary aluminum ash was used as the main raw material, and the method of alkali leaching pretreatment combined with pyrometallurgical sintering was adopted. MgO was used as the modifier to prepare MA materials. The research process investigated the influence of alkali leaching process parameters on the leaching rates of Al and AlN, analyzed the alkali leaching mechanism of secondary aluminum ash, and investigated the effect of sintering process parameters on the properties of the prepared magnesium-aluminum spinel materials. The following main conclusions are obtained. The alkali leaching test shows that increasing the concentration of NaOH, raising the leaching temperature, increasing the liquid-solid ratio, and accelerating the stirring rate are all conducive to improving the leaching rates of Al and AlN. Under the optimized alkali leaching conditions of a temperature of 80℃, a NaOH concentration of 1.6mol·L^-1, a stirring rate of 300r·min^-1, and a liquid-solid ratio of 12∶1, the leaching rate of Al reached 80.35% and that of AlN reached 53.21%. The leaching reaction of Al and AlN in secondary aluminum dross is essentially a hydrolysis reaction, and the alkaline system promotes the progress of this hydrolysis reaction. Spinel materials with complete crystal form and high crystallinity can be prepared by using the alkali leaching residue as raw material and the MA material ratio of MgO under the sintering conditions of 1300-1400℃ and sintering time of 3hours. The apparent porosity of the MA material prepared at 1400℃ is 31.56%, and its compressive strength is 50.22MPa, which is higher than the national industry standard “Magnesia Bricks and Magnesia-alumina Bricks” (GB/ T2275—2007) (40MPa).