GB829094A - Production of uranium peroxide - Google Patents

Abstract

Uranium peroxide is precipitated from an aqueous uranyl salt solution, particularly the sulphate, containing magnesium and fluorine, by effecting the precipitation in the presence of a substantial amount of ammonium sulphate, which holds fluorine in solution and improves the crystalline form of the uranium peroxide obtained. Aqueous uranyl sulphate starting solutions preferably contain between 3 and 16% of uranyl sulphate and between 1 and 2 1/2 mols. of ammonium sulphate are added for each mol. of uranyl sulphate. The pH is preferably between 2 and 4 and sufficient hydrogen peroxide or alkali metal peroxide is then added to precipitate the uranium peroxide, the pH of the solution being adjusted by acid or alkali during the precipitation. The precipitation should be effected below 65 DEG C. and preferably at at least 30 DEG C., and the crystalline uranium peroxide formed should be separated from the solution promptly to avoid fluorine contamination. According to examples: (1) slag obtained in the production of uranium metal by reduction of uranium tetrafluoride by magnesium was air roasted and treated with dilute sulphuric acid. Hydrogen peroxide was added to convert tetravalent uranium to hexavalent and calcium carbonate was added to bring the pH to 3.7. The mixture was maintained at 85 DEG to 90 DEG C. and then filtered; the filter cake washing and filtrate were combined to provide an uranyl sulphate starting solution. Ammonium sulphate was added and the pH adjusted to 2.9 with caustic soda solution. Precipitation of uranium peroxide was effected with aqueous hydrogen peroxide. (3) a uranyl sulphate solution obtained by calcining uranium dross containing magnesium and fluorine, with quick lime, digesting the calcined product in aqueous sulphuric acid at 90 DEG to 95 DEG C., neutralizing with calcium carbonate to a pH of 3.5 and filtering, was used as the starting solution. Ammonium sulphate was added and the solution was acidified to pH 3 with dilute sulphuric acid and cooled to 40 DEG C. After filtering 27.5% hydrogen peroxide solution was added beneath the surface during which addition the pH fell to 1.5; aqueous ammonium hydroxide was added to restore the pH to 3. Precipitated uranium peroxide was separated from the mother liquor by centrifuging and after washing with distilled water at 60 DEG C. contained less than 0.2% of fluorine. Specifications 829,088 and 829,091 are referred to.