Abstract: Process for the production of hydrated aluminae through the precipitation of aluminum hydroxide in a reactor by the reaction of an aluminum compound soluble in a polar solvent with a precipitating agent, also solubilized in the polar solvent, in constant conditions of pH, temperature, concentration and agitation; concentration of the suspension of precipitated aluminum hydroxide; crystallization in an alkaline pH, essentially constant; separation of the crystallized aluminum hydroxide, for later washing and drying. The product obtained is homogeneous and with excellent characteristics for utilization in the manufacturing of catalysts and catalytic supports. The process can be applied, advantageously, in the treatment of the acid waste from processes which utilize Friedel-Crafts type reactions, obtaining, in addition to the hydrated alumina, a liquid effluent with low metal contents.