Aluminium leaching from red muds for their complexing reprocessing

Abstract

Complexing processing of «red muds» (R.M.) - waste of bauxite reprocessing by the Bayer's method, is one of the important tasks of toxic industrial waste utilization. Studied the possibility of aluminum leaching from the R.M. which content reach 14 %, received from Bogoslovsky aluminum plant of JSC «Siberian-Urals Aluminium Company» by aqueous solutions of NaOH. The process was carried out at atmospheric pressure and temperatures near to the boiling point of leaching solutions with the utilization of the residual alkali. The time’s dependence of the aluminum leaching degree from the R.M. by aqueous solutions of NaOH passes through the maximum due to the formation of secondary precipitation of aluminum. The cause of secondary sedimentation is the interaction of silicon with aluminum with formation of insoluble aluminosilicates, for example, Nа2Аl2Si2O8·2Н2O. The conditions of leaching, under which the formation of stable aluminate solutions during the time do not form of secondary precipitations were established. The maximum achieved values of the aluminum leaching degree in autoclave-free conditions was reach 20-25 %. The removal of alkali and part of aluminum under the first stage of complexing processing of R.M. leads to their enrichment in iron. The cakes from aluminum leaching and next carbonate scandium leaching can be used for pyrometallurgical recovery of iron and slag, in which untreated elements are passed, including residual aluminum, scandium, sum of rare earth elements, titanium and zirconium. A significant decrease in the volume of slag opens more opportunities for further isolation their components by acidic methods.