Patent GB-768831-A (GB)
Title: Recovery of uranium values from waste material
IPC: C01G43/06
Filed: 1946-01-02
Abstract: Uranium values are recovered from uranium containing waste material by hydrofluorinating the material preferably at 500 to 600 DEG C. to convert metal values to non-volatile fluorides and thereafter reacting the residue with fluorine preferably at 400 to 500 DEG C. to convert the uranium to uranium-hexafluoride which is volatilized and recovered as a condensate in cooled traps. Typical waste material includes broken glass containers, broken insulators and the metallic parts of isotope separation apparatus. Silica, contained in the initial waste is converted to silicon fluoride in the initial hydrofluorination and is removed before flurorination is performed. If a chromium containing material is treated the fluorides of uranium and chromium are collected together and the resulting condensate can either be oxidized in aqueous medium to convert the chromium to a soluble chromate, followed by precipitation of the uranium in an insoluble form, or alternatively the condensate may be treated with aqueous ammonia for example, to precipitate chromium and uranium and a mixed hydroxide and uranate after which the precipitate thus formed may be dissolved in aqueous acid, oxidized to convert the chromium to a soluble chromate, and the uranium then precipitated in insoluble separable form, preferably in the form of ammonium diuranate. Silica may be removed from the diuranate precipitate by dissolving it in hydrochloric acid and concentrating almost to dryness whereupon silica is precipitated and removed after which the diuranate may be reprecipitated with ammonium hydroxide.  If no silica is present in the initial washings of the condensate from the traps, they may be treated with fluoride complexing and sorting out reagents, for example by treatment with excess ammonium hydroxide in the presence of an aluminium salt, after which the precipitate may be dissolved in nitric acid and subjected to extraction with an organic solvent such as ethyl ether or carbitol.  The uranium may be recovered by contacting the solvent with water and precipitating the uranium as peroxide from the aqueous solution.  According to an example, waste material was treated with hydrogen fluoride at 500 to 600 DEG C. to remove silica and convert the remaining metals to the corresponding fluorides, after which the system was purged of hydrofluoric acid and thereafter the material was treated with fluorine at 450 to 500 DEG C. to evolve the volatile uranium and chromium fluorides. These were condensed in five copper traps, the first two of which being cooled with a dry icetrichlorethylene mixture and the rest cooled in liquid oxygen.  The first two traps, which contained the uranium and chromium fluorides were washed with water and the solution treated with excess ammonium hydroxide thereby precipitating ammonium uranate and chromium hydroxide together with hydrated silica; the precipitate was removed and treated with a persulphate to oxidize the chromium, and ammonium hydroxide was added to precipitate the ammonium uranate together with the silica.  The latter was eliminated by evaporation with hydrochloric acid and the ammonium diuranate was further purified by several persulphate oxidazations to complete the removal of chromium followed by precipitation from a solution in nitric acid to remove sulphate.  The ammonium diuranate obtained was dissolved in dilute nitric acid for use.