| 摘要 |
<p>Lithium is extracted from petalite by calcining the ore at 600 to 1350 DEG C. grinding, and treating with sulphuric acid at 150 to 400 DEG C. and thereafter extracting the reaction mixture with an aqueous liquid which dissolves the lithium sulphate formed. The sulphuric acid employed has a strength greater than 50% and may be oleum; calculated as 100% acid it constitutes 10% to 50% by weight of the ore. The reaction product may be extracted with water or solutions of hydroxides, carbonates, bicarbonates, borates, silicates and aluminates of alkali or alkaline earth metals or ammonium, the pH not being raised above 7; aqueous solutions of organic solvents such as methyl or ethyl alcohol or acetone may also be used. In all cases, the lithium sulphate is extracted unchanged, and the extract solution may be treated to precipitate lithium as carbonate. The insoluble residue from the extraction is an alumina/silica complex substantially free from metals having coloured oxides: it is hence suitable as an ingredient of glasses or ceramics and the preparation of ceramic slips. According to an example, petalite was roasted at 1000 to 1200 DEG C., crushed to 120 B.S. sieve, then treated with strong sulphuric acid at 200 to 400 DEG C. The cooled mixture was extracted with water and filtered. The filtrate was treated with chalk or limestone at a pH of 6.0 to 6.5, filtered, treated with lime water at pH 12 to precipitate magnesium contaminant and then with soda ash to precipitate calcium carbonate. After adjusting the pH to 7 with sulphuric acid to precipitate aluminium, which was filtered off, the lithium was precipitated as carbonate by means of sodium carbonate solution and separated in the hot at 90 to 100 DEG C.</p> |
