GB759900A - Improvements in and relating to the production of uranium - Google Patents

Abstract

Uranium is selectively precipitated from solutions thereof containing other metals by adjustment of the pH in the presence of a soluble phosphate or arsenate. Thus a solution containing U, Cu and Al where the atomic ratio Al/U does not exceed 1, is treated with a soluble phosphate or arsenate in amount sufficient to combine with the uranium and the pH is adjusted to 2.5 with alkali to precipitate uranium values. If the Al/U ratio exceeds 1 then the phosphate or arsenate should be sufficient to combine with both the U and Al and the pH is adjusted to 1.8 to 2.0 to precipitate uranium values. Ferric iron may be removed from the initial solution by adjustment of the pH to 3.0 to 3.5 thereby precipitating iron and the pH of the resulting solution is adjusted to 6.0 to 6.1 whereby U, Al and Cu precipitate. The precipitate is then taken of in acid the phosphate or arsenate added and the resulting solution adjusted to pH 2.5 to precipitate uranium values. If the precipitate containing U, Al and Cu also contains iron the precipitate, after being taken up in acid is adjusted to pH 3.1 to precipitate ferric iron before being treated again with phosphate or arsenate. Alternatively, if a large content of ferric iron is present in the initial solution, the ferric iron may be reduced to the ferrous state and the U, Al and Cu may be precipitated by adjusting the pH to 6.0 to 6.1 leaving the ferrous iron in solution. The precipitate is taken up in acid and the uranium selectively precipitated as before. A uranium solution containing ferrous and ferric iron, Al, Si, Ca, Mg, Mn, Ni, Co and Zn may be treated with alkali to pH 3.1, followed by separating the solution containing dissolved U and Al from the precipitate, adding alkali metal phosphate equivalent to the U and Al, adjusting the pH to 3.5 by alkali metal hydroxide whereby U and Al precipitate as phosphate, taking up the precipitate in mineal acid to give a pH of 1.5, adding ammonia to a pH of 1.8 and thereby precipitating ammonium uranyl phosphate which is recovered. Sodium diuranate may be prepared by treating the ammonium uranyl phosphate with sodium hydroxide. According to examples (1) a solution containing U, Fe, Al, Zn and Co or sulphates and having an Al/U ratio of 1:1 was treated with calcium hydroxide to a pH of 3.1 whereby basic ferric sulphate precipitated, the pH falling to 2.8. Phosphonic acid was added and the pH adjusted to 2.5 with calcium hydroxide, thereby precipitating the uranium. If the Al/U ratio were greater the iron free solution may be treated with ammonium phosphate and the pH adjusted to 1.8 with aqueous ammonia to precipitate uranium. (2) A solution containing ferric and ferrous iron, Cu, Al, Co, Mn, Zn, Ni, Ca and Mg as sulphates was adjusted to pH 6.1 by alkali metal hydroxide to precipitate ferric iron, Cu, Al and U. The precipitate was dissolved in acid, the ferrous salt oxidized with hydrogen peroxide, nitric acid or chlorine and the solution treated as in (1) above. (3) If the solution is very dilute a carrier such as copper ferric or aluminium sulphate, is added to constitute 0.1 per cent. by weight of the solution. Such a solution was adjusted to pH 6.1 by caustic soda and the uranium containing precipitate was taken up in sulphuric acid and treated as in (1) to remove ferric iron and precipitated uranium