Rich microbubbles modifying the leaching mechanism of aluminum and aluminum nitride of secondary aluminum dross in sodium aluminate solution

An understanding of the mechanisms of reactive Al and AlN in a sodium aluminate solution contributes to the safe and effective utilization of secondary aluminum dross (SAD). This study demonstrates that the slurry temperature increased exponentially with an increase in the SAD dosage. Synergistic kinetic phenomena in the form of a large dosage and high temperature occurred initially in relatively stable microbubbles and later in the slurry. The leaching efficiencies of pure Al and AlN powders were greater than that of Al and AlN in SAD, respectively. Meanwhile, the leaching rate became higher for Al in SAD but lower for AlN in SAD compared to that of pure Al and AlN powder. The AlN particles in SAD were covered by Al(OH) 3 precipitated from the saturated solution in the bubbles. As a result, the relatively stable microbubbles with a thick border accelerated the reaction of Al and AlN and produced a saturated solution thereby changing the leaching efficiency and leaching rate of AlN in SAD. The embedded Al and AlN grains in the SAD, relatively stable microbubbles, and the SAD particles covered by Al(OH) 3 , synergistically changed the leaching mechanism. These results provide further understanding of the reaction mechanism of rich bubbles and facilitate the optimization of the comprehensive utilization of SAD.