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.

Evaluation of Main Factors for Improvement of the Scandium Leaching Process from Russian Bauxite Residue (Red Mud) in Carbonate Media

“…To prevent the formation of dawsonite and coprecipitation of Sc with it in the processes of carbonate RM leaching, it is necessary to prevent the release of Al into the carbonate solution together with Sc. 87 In the absence of Al, the saturation of Sc carbonate solutions by CO 2 (g) does not result in the formation of secondary precipitates. 27 To remove some of the soluble forms of Al from RM, two consecutive stages of alkaline pretreatment of RM were carried out with aqueous 4.0 mol L –1 NaOH solution at 100 °C for 120 min.…”

“…This treatment practically does not leach Sc, while some portion (15–20%) of Al is released into the alkaline solution. 87 The concentration of Al in carbonate solutions was 2.0–2.2 g L –1 . XRD data of the pretreated and washed RM sample indicate a decrease in the intensity of the reflexes of calcium carbonate which is associated with its interaction with NaOH ( Figure 10 ).…”

“…To prevent the formation of dawsonite and coprecipitation of Sc with it in the processes of carbonate RM leaching, it is necessary to prevent the release of Al into the carbonate solution together with Sc . In the absence of Al, the saturation of Sc carbonate solutions by CO 2 (g) does not result in the formation of secondary precipitates .…”

Current key options for management of industrial alkaline waste of alumina production (red mud)

“…As alternative reagents for selective extraction of Sc, Zr and some other valuable metals from RM, aqueous solutions of Na2CO3, NaHCO3 or their mixtures are proposed. Scientific foundations of carbonate processes of Sc extraction from RM were developed by employees of ISSC RAS UB (Russia) [28] and subsequently developed by some researchers [29][30][31][32][33]. The use of acids provides a high degree and ease of extraction of REEs from all types of RM due to the high content of compounds Fe, Al, Ca and Ti, which are relatively easily decompose in acidic solutions releasing valuable components.…”

Complex reprocessing of industrial alkaline waste of alumina production (red mud) for solving raw materials and environmental problems

“…An complex approach to the reprocessing of RM dictates the need to recover aluminum from it as a useful product [16]. Two methods of aluminum recovery under conditions without autoclave treatment of RM have previously been discussed [17]. According to the first method, RM samples were directly leached by NaOH aqueous solutions at temperatures close to boiling points.…”