GB829087A - Production of aqueous uranyl sulphate solution from uranium dross - Google Patents

Abstract

Uranyl sulphate solutions are obtained from uranium dross arising from the working of metallic uranium and from the slags obtained in the recovery of metallic uranium by reduction of uranium tetrafluoride with calcium or magnesium and separating the metallic uranium, by burning the dross (or slag) in air, preferably at 600 DEG to 1000 DEG C., and thereafter mixing the oxidized dross with lime and roasting in contact with air at 600 DEG 1000 DEG C. If chlorides are present in the dross they may be eliminated by adding a small amount of iron oxide or ammonium sulphate during either of the air calcining steps. The quantity of lime employed is that theoretically necessary to form calcium diuranate although an excess of either lime or uranium may be present. The roasted product is then mixed with sulphuric acid solution and treated with an oxidizing agent to convert any tetravalent uranium into hexavalent form. The preferred sulphuric acid concentration is 5 to 50%. The oxidation of the sulphate solution may be effected with air, hydrogen peroxide, permanganate, chromate or nitrate, the preferred reagents being air initially and hydrogen peroxide to complete the oxidation. The calcium sulphate formed precipitates and may be separated by filtration, the solution preferably being adjusted to a pH of 2 to 4 before effecting the separation. Iron precipitates with the calcium. According to an example, a metallic uranium product obtained as scrap from metal workings and as dross from metal melting and pour operations is converted to U3O8 by heating in air at 600 DEG to 1000 DEG C. and the roasted product is mixed with lime and heated in a rotary kiln to 700 DEG to 800 DEG C. in the presence of air for 3 hours. The calcium diuranate product was then crushed and dissolved in 15 1/2 % strength sulphuric acid at 85 DEG to 90 DEG C. and agitated for 2 hours at 90 DEG to 95 DEG C. Aqueous 27 1/2 % hydrogen peroxide solution was then added and the charge agitated at 90 DEG to 95 DEG C., whereby the pH dropped to 0.5 to 0.6. Calcium carbonate was then added to adjust the pH to 3.7 and the mixture held at 90 DEG to 95 DEG C. whereby the iron and calcium precipitated leaving a purified uranyl sulphate solution. The reference is made to the recovery of uranium as uranium peroxide from this solution by the process of Specification 829,088.