Abstract: There is disclosed a method for the elimination of the chief impurities in aluminum dross tailings. The method can be used as a pretreatment in the manufacture of aluminum sulfate from aluminum dross tailings in a continuous flow reaction zone in which the dross tailings prior to reaction with sulfuric acid are pretreated to reduce the more objectionable contaminants contained therein to acceptable levels. The most objectionable contaminant in the dross tailings is aluminum metal which, in the invention, is oxidized with water or steam at elevated temperatures. The dross tailings, which are chiefly particles of aluminum oxide, are suspended in an aqueous slurry and the slurry is heated to a temperature from 185.degree.-225.degree. F. and maintained under liquification pressures and sufficient agitation to insure particle-to-particle attrition that removes an aluminum hydroxide coating which would otherwise inhibit the reaction.

Abstract: There is disclosed a method for the elimination of the chief impurities in aluminum dross tailings. The dross tailings, which are chiefly particles of aluminum oxide, are suspended in an aqueous slurry and the slurry is heated to a temperature from 185.degree.-225.degree. F. and maintained under liquification pressures and sufficient agitation to insure particle-to-particle attrition that removes an aluminum hydroxide coating which would otherwise inhibit the reaction. The reaction rate is accelerated by chemical and physical additives that can be optionally added to the slurry such as trace quantities of caustic, which serves as a source of hydroxyl ligands to increase the solubility of aluminum hydroxide and/or refractory particles such as ceramic spheres which increase the attrition. Other contaminants present in the dross tailings include aluminum nitride, which is decomposed to aluminum oxide and ammonia, and aluminum carbide which is decomposed to aluminum oxide and methane.