Production of pure ammonium diuranate concentrate

The treatment of solutions from leaching and/or mechanical processing of uranium ores results in ammonium diuranate containing organic as well as inorganic impurities. A procedure as follows was developed for the production of ammonium diuranate concentrate which is purer than the starting material (solid or suspended in water). Sulfuric acid is added to the starting material, whereupon the ammonium diuranate precipitate dissolves at pH 1 to 4.5 while the impurities remain mostly in the solid phase. The liquid phase is separated from the solid phase by decantation, filtering, or centrifugation, and pure ammonium diuranate is precipitated from the solution by using gaseous or aqueous ammonia at pH 6.8 to 9.0. (Z.S.)