Procédés de récupération de l'uranium à partir de solutions aqueuses contenant de l'uranium.

摘要

In a liquid-liquid extraction process for the recovery of uranium values from an acidic aqueous solution thereof, the acidic solution is contacted with an organic uranium-complexing liquid (see below), the resulting uranium-containing organic solution is separated from the depleted aqueous phase and the uranium values stripped with an aqueous ammonium carbonate solution loaded with uranium values, thereby precipitating uranium values from the organic phase. The resulting aqueous slurry is separated from the stripped organic phase. The organic uranium-complexing compound may be an ether, a glycol ether, an ester, a ketone, an alcohol, an alkylphosphate, an amine or a dialkyl phosphoric acid. The uranium loaded ammonium carbonate stripping solution may be obtained by adding ammonium carbonate to an aqueous solution containing uranium values; however, preferably the stripping solution is obtained by recycling the aqueous ammonium carbonate stripping solution after the removal of the ammonium uranyl carbonate precipitate and replenishing with NH4+ and CO3-. The composition of the uranium-loaded stripping solution may be varied but NH4+ must be the major cation present although up to 40% of Na+ and/or K+ may be present. Enough carbonate must be present in the stripping solution to provide the stoichiometric requirements of 3 moles of carbonate per mole of uranium present in the organic phase and the total anion concentration must be at least 0,7 molar. The pH of the aqueous phase after contact with the uranium-containing organic solution must be maintained above 7,5. In a preferred form of the invention a second stripping stage and a method of separating molybdenum from uranium values are incorporated in the process. According to Fig. 2 the organic phase was passed to a first stripping stage 7 where it was contacted with an aqueous solution of ammonium carbonate containing uranium values. Uranium and molybdenum values were transferred to the aqueous carbonate solution and the uranium precipitated as (NH4)4 UO2 (CO3)3. The resulting aqueous slurry was transferred to settler 8 where ammonia and carbon dioxide were added, the thickened slurry was filtered in filter 9 and the resulting uranium-containing precipitate calcined to U3O8. A portion of the filtrate from filter 9 was bled off and heated in vessel 11 to remove NH3 and CO2 until the pH dropped to 7 to 8 and uranium precipitated. The resulting slurry was transferred to filter 12, the precipitate was combined with that from filter 9, and the aqueous molybdenum-containing phase was discarded. The organic liquid from the first stripping stage was transferred to a second stripping stage B where it was treated with an aqueous ammonium carbonate solution and virtually all the uranium remaining was stripped into the carbonate solution and the resulting uranium-depleted organic solution was returned to extraction section 6. When molybdenum and uranium values are to be separated using a recycled ammonium carbonate solution, the concentration of the molybdenum in the recycled solution is maintained below the saturation point by separating the uranium and molybdenum-containing solution into a major portion and a minor portion and recycling just the major portion to which has been added additional ammonium and carbonate ions.