A process for preparing high-purity uranium values from uranium ore concentrates

摘要

A solution containing uranium substantially free from other metals is obtained by preparing an aqueous solution of a uranium ore concentrate, having a pH from 0.1-3.0, contacting the solution with a solution of a dialkyl phosphate in an organic water-immiscible solvent and separating the resultant uranium-bearing organic phase from the aqueous phase. The initial solution is prepared by the use of an oxidising agent with a mineral acid, e.g. sodium perchlorate with hydrochloric acid, or with an oxidising acid such as nitric acid; hydrogen peroxide and manganese dioxide are also referred to as oxidising agents, and sulphuric acid is mentioned. The aqueous solution is then intimately mixed with the organic phase in an extractor. The preferred dialkyl phosphate is di-(2-ethylhexyl)phosphoric acid and suitable solvents are kerosene, naphtha, heptane or other water-immiscible aliphatic hydrocarbon. The phases are separated and the uranium-containing organic phase may be scrubbed with a small amount of dilute hydrochloric acid and stripped e.g. with sodium or ammonium hydroxide or carbonate solutions or concentrated hydrochloric acid. If hydrochloric acid is used, the solution may be evaporated to dryness and the resultant uranyl chloride calcined to U3O8, or evaporated to eliminate excess hydrochloric acid (which can be recycled), diluted with water and the uranium precipitated with ammonia as ammonium diuranate which can be calcined to oxide.