Authors: A.A. Karapuzikova, L.I. Galkova, A.A. Krylov, R.I. Gulyaeva, V.N. Rychkov, M.S. Botalov, E.V. Kirillov

Title of the article: Extraction of rare earth elements from red sludge

Year: 2026, Issue: 1, Pages: 42-55

Branch of knowledge: 2.6.8. Technology of rare, scattered and radioactive elements

Index UDK: 669.85/.86

DOI: 10.26730/1999-4125-2026-1-42-55

Abstract: Red sludge (RS) is a waste product formed in the production of alumina using the Bayer method. The scale of its formation is equivalent to the volume of marketable products, averaging 1.1 - 1.2 tons per 1 ton of alumina. Storage of RS is a spatial and environmental problem. Currently, RS is not recycled and used in small quantities. Red sludges contain essential valuable elements such as aluminum, iron, titanium, calcium, silicon, and free alkali. Rare-earth elements concentrated in the sludge are suitable for industrial extraction. This work is aimed at data extension regarding leaching of REE from RS using sulfuric acid. The proposed method of low-temperature RS roasting with sodium carbonate followed by leaching of the roasting product using sulfuric acid is of interest. The effect of sodium carbonate additives in the process of RS roasting as well as leaching parameters, such as pH solution, temperature, and duration, were studied. The composition of the initial RS sample and the products of its roasting with sodium carbonate were determined by X-ray phase analysis. The method of differential thermal analysis followed by X-ray diffraction of heat treatment products was used to determine the thermal transformations during heating of RS and its mixture with NA2CO3. It has been established that roasting with sodium carbonate has a positive effect on leaching. The total extraction of REE increased by 10-15%. In addition, leaching of the roasted mixture helps to prevent the formation of silica gel. The acidity and the temperature of the solution have the greatest effect. The extraction of Sc and Dy into the solution reaches 90%, and La and Ce – about 50%. It is noted that leaching without heating leads to a decrease in the solubility of aluminum (from 55 to 35%) and iron, which practically does not pass into solution.

Key words: REE red sludge roasting sodium carbonate XFA differential thermal analysis leaching

Receiving date: 12.07.2025

Approval date: 15.01.2026

Publication date: 19.03.2026

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