Red mud pulp carbonization with scandium extraction during alumina production

Abstract

In the existing technology for the processing of bauxites into alumina, scandium remains in red mud. The average scandium concentration in bauxites coming into processing from the Severoural’skoe and Srednetimanskoe deposits is studied. Bauxites are a rich potential source for the production of scandium. The fractional distribution of mud and the concentration of scandium in its fractions are determined. The concentration of scandium in aluminate solutions and that from mud fields is extremely low and amounts to <0.05 g/m3. The processing of mud with a soda solution results in the partial solubility of scandium with its complexing. For the precipitation of scandium, the solubilities of Al, Ga, Zn, and Sc compounds in alkalinesoda-hydrocarbonate solutions are studied under the conditions of reactive and gas carbonization. Zinc hydroxide is the best coprecipitant. The carbonization of red mud pulp provides for the partial recovery of scandium and reduces the toxicity of mud storage areas by converting the alkaline-carbonate liquid phase into a carbonate-hydrocarbonate one with a lower toxicity.