METHOD OF EXTRACTION OF ALUMINIUM OXIDE FROM RED SLIME Russian patent published in 2015 - IPC C01F7/06 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to processing of red slime - waste of aluminous production of processing of bauxites by Bayer alkaline method. The method of extraction of aluminium oxide from red slime comprises autoclave leaching of red slime at the temperature 230-260°C and pressure 21-26 MPa in presence of calcium hydroxide in alkaline solution, meanwhile into the initial red slime the calcium hydroxide amounting 2.5-5.0% of the mass of initial slime and 40% NaOH solution until getting a ratio L:S = 1.5÷2.8:1; after autoclave leaching the obtained pulp is cooled down to 80-120°C, then 10% NaOH solution or water is added until getting a ratio L:S not less than 5:1 and it is conditioned at mixing during 1 hour minimum, then it is filtered. The invention allows to extract aluminium oxide from red slime without conducting additional operations, and also to provide high percentage of extraction of aluminium oxide from red slime and to reduce losses of the target product with the waste red slime.

EFFECT: invention allows to decrease the content of alkali (Na₂O_caust) in the waste red slime and to return it into alkaline aluminium-bearing solution.

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