Synthesis of submicronic α-alumina from local aluminum slags

Abstract

In this study, a high valued product submicronic ?-alumina is successfully extracted from aluminum slags generated by the local aluminum industry. The extraction technique is based on the leaching of slags by H2SO4 followed by precipitation. The coarser aluminum-rich fractions of the slags are used in this study instead of the finer oxide-rich fractions that were commonly used in previous studies. The precipitation of the leached slags by NH4OH is controlled by zetameter in order to determine the optimal precipitation pH. Then, the obtained gel showing the higher precipitation rate and the finer particle size is calcined at 1200 ?C and characterized by XRF, XRD, FTIR, SEM, EDS and laser granulometry. Even without any pretreatment of slags, the XRF analysis reveals that a high purity and high extraction efficiency of 99.2% and 93.75% respectively can be achieved just at a leaching acid concentration of 15%. XRD spectrum shows that the produced alumina is a pure a-corundum, which is confirmed by FTIR spectrum showing only the Al-O bonds. The laser granulometry shows that the recovered powder exhibit a wide particle size distribution. It is between 50 nm and 20 ?m while the average particle size (d50) is about 400 nm. SEM observations reveal that the grains are in the form of submicronic whiskers. The above characteristics allow the obtained alumina powder in this study to be used in the usual applications of alumina such as refractory, ceramic fibers, abrasive, etc. The obtained powders may assume also applications as a thermally stable substitute for the commonly used transition alumina powders, which need further investigations in future studies.