GB750336A - Method of extracting lithium from its silico-aluminous ores - Google Patents

Abstract

Lithium acetate is formed by heating a lithium ore with sodium or potassium acetate under anhydrous conditions below 400 DEG C. to effect an exchange between the lithium of the ore and the sodium or potassium ion employed, and thereafter leaching the reaction product to remove lithium acetate. The ore, preferably spodumene, may first be converted to its b modification by heating to 1050-1150 DEG C. prior to reaction or converted to the vitreous state by heating to 1380 DEG C. and suddenly cooling. Specifications 9971/06, [Class 1 (iii)], and 678,978, [Group III], are referred to.ALSO:Lithium is extracted from silicoaluminous ores thereof by heating the ores in anhydrous state with sodium and/or potassium salts which melt at and which form lithium salts which melt at, a temperature below 400 DEG C. thereby exchanging the sodium or potassium ions with the lithium ions to form a lithium salt extractable by lixiviation or melting out. Suitable salts are the acetate, nitrate, nitrite and chlorate of sodium and potassium and the ore preferred is spodumene. The spodumene is preferably converted to its b modification before the extraction reaction by heating it to 1050 DEG C. to 1150 DEG C. or alternatively converted to a vitreous form by heating to fusion and suddenly cooling; alternatively the ore may be subjected to a preliminary calcination in the presence of calcium oxide or other alkali or alkaline earth metal oxides. Small quantities of alkali or alkaline earth metal compounds such as sodium hydroxide, chloride, or sulphate may also be added to the mixture of the lithium ore and the sodium or potassium decomposing salt. The extraction reaction may also be effected by washing the moderately heated ore by means of molten sodium or potassium salts preferably in counter-current after which the lithium is extracted from the cooled molten salt mixture. According to a preferred procedure spodumene decrepitated by heating at 1100 DEG C. and thereafter finely ground is mixed with anhydrous sodium acetate or with an aqueous solution of the trihydrate and the water if any evaporated below 120 DEG C. The mixture is then heated slowly up to about 324 DEG C. thereby forming lithium acetate which is extracted from the cooled ground reaction mass by boiling water. The solution may be concentrated by evaporation thereby precipitating impurities from the acetate solution and purified from organic impurities by the addition of a decolourant such as animal black or bentonite. The lithium is suitably extracted from the acetate solution in the form of lithium carbonate by reacting the acetate solution with sodium carbonate solution at a 100 DEG C. in an amount preferably stoichiometrically equal to the lithium content. The lithium is thereby precipitated as carbonate and a solution of sodium acetate containing small amounts of lithium carbonate is formed which may be concentrated by evaporation or reduced to the dry state for recycling to the extraction reaction. Excess soda if present may be neutralized with acetic acid before recycling; alternatively if excess soda is recycled the lithium which would otherwise remain in the reaction residue on lixiviation as carbonate may be recovered by adding acetic acid to the lixiviation water or by slurrying the reaction residue after lixiviation with slightly acidulated water containing acetic, hydrochloric, nitric or sulphuric acid thereby converting the insoluble carbonate to soluble salts which may be recovered by evaporation or which may be subsequently precipitated as carbonate. The lixiviation of the reaction product may also be effected by alcohols such as amyl alcohol or by pyridine which selectively dissolve the lithium salts. Further examples relate to the use of sodium nitrite for the extraction reaction whereby lithium nitrate and sodium nitrite may be formed. Specifications 9971/06 [Class: 1(iii)] and 678,978 are referred to.