Recovery of uranium values from uranium-bearing raw materials

摘要

Finely divided uranium-bearing materials are leached in aqueous sulfuric acid together with manganese dioxide in an amount sufficient to oxidize the uranium to the hexavalent state. The dissolved uranium may be subsequently precipitated in known manner. The leaching may also be effected in the presence of a minor quantity of ferric ions supplied, for example, as ferric sulfate. According to Examples (1) an ore bearing uranium and gold was crushed and the gold values were extracted with aqueous sodium cyanide and the residue was treated as shown in the Figure. The ore was fed to an agitator 1 and pulped with overflow liquor from a thickener B to form a slurry having a pH of 3.5, thereby precipitating any ferric ions: the liquor from the thickener B contained the solubilized uranium values and was partially neutralised by the incoming ore. The slurry was passed to a thickener A and the overflow containing the uranium passed to a precipitator with associated thickener F where the uranium was precipitated by magnesium oxide at a pH of 6.5. The barren solution from the thickener F was returned as washing liquor to the extraction process. The underflow from thickener A was treated with sulfuric acid and manganese dioxide in a vessel 3 and passed to a thickener B from which the overflow, containing the dissolved uranium, was recycled through thickener A for passage to the precipitating unit. The underflow was washed countercurrently with barren liquor in thickeners C, D and E. Small quantities of iron are provided by naturally occuring silicates in the ore and by metallic iron formed by the abrasion of machinery. (2) A uranium ore was wet ground and adjusted to a 60% solid slurry; sulfuric acid together with manganese dioxide and a minor amount of powdered iron were added thereto. The slurry was agitated at ambient temperatures and then filtered thereby solubilising 90% of the uranium of the ore.