GB844407A - Process for the production of ammonium uranate - Google Patents

Abstract

Ammonium uranate is precipitated from an aqueous solution of a hexavalent uranium salt, e.g. uranyl chloride, fluoride, sulphate, or nitrate, having a pH of less than 6, by passing a gaseous mixture of ammonia and an inert diluent, e.g. air, through the solution with vigorous stirring until a pH of 6-7, preferably 6.5 is reached, the ratio of inert gas to ammonia being at least 1:10. The reaction may be continued by the continuous introduction of gas and solution, the flow of gas or solution being regulated so as to maintain the above pH. The uranium salt solution may be a hydrofluoric acid solution of uranyl fluoride obtained by hydrolysis of uranium hexafluoride, or a solution obtained by acidifying a solution of a complex hexavalent uranium carbonate. A product containing less than 1 X 10-5% of boron (based on uranium) may be obtained from a solution containing 10-2% of boron. Precipitation in the form of needles may be effected at a temperature of above 70 DEG C. and with a volumetric ratio of ammonia to inert gas of 1-5 to 1. Precipitation in the form of spheres may be effected at a temperature of below 70 DEG C., e.g. 20-50 DEG C. According to Example 1, spherical particles having a mean diameter of 6 are obtained by introducing a mixture of 1 vol. ammonia and 3 vol. air with stirring at a rate of 150 1/min. and for a period of 5 hours into a uranyl nitrate solution which contains 90 grm./1. of uranium and a small amount of nitric acid and which is held at a temperature of 50 \sB 5 DEG C. When a pH of 6.5 is reached a mixture of 1 vol. ammonia and 2 vol. air at a rate of 150 1./min. and uranyl nitrate solution at a rate of 2 1./min. are continuously introduced while the temperature is maintained at 50 \sB 5 DEG C. and the pH is maintained at 6.5. According to Example 2, needle-like crystals are obtained by introducing a mixture of 1 vol. ammonia and 2 vol. air with stirring at a rate of 60 1./min. and for a period of 2.5 hours into a hydrofluoric acid solution of uranyl fluoride obtained by the hydrolysis of uranium hexafluoride, the solution being held at a temperature of 80-90 DEG C.