Recovery of uranium from the filtrate of 'ammonium diuranate' prepared from uranium hexafluoride

The hydrolysis of uranium hexafluoride and its conversion to 'ammonium diur anate' yields an alkaline solution containing ammonium fluoride and low con centrations of uranium. The recovery of the uranium has the advantage of sa ving this valuable metal and the avoidance of unacceptable discarding the a bove mentioned solution to the environment. The recovery of uranium(VI) is based on its complex with the excess of fluoride in the solution and its ad sorption on to an anionic ion-exchange resin. The 'ammonium diuranate' filt rate has an approximate concentration of 130 mg l(-1) of uranium and 20 g l (-1) of ammonium fluoride. An effective separation and recovery of the uran yl fluoride was achieved by choosing a suitable pH and flow rate of the ura nium-bearing solution on to the resin column. The effluent ammonium fluorid e will be recovered as well. Uranium fluoride adsorbed by the ion-exchanger is then transformed into the corresponding uranyl tricarbonate complex by percolation of a dilute ammonium carbonate solution. Finally, the free fluo ride uranium carbonate is eluted from the resin with a more concentrate amm onium carbonate solution. The eluate now can be storage to be precipitated as ammonium uranyl carbonate (AUC). The loading and elution of uranium(VI) on to the ion-exchange column was followed up by a fluorescence test. A flu x prepared using a mixture of sodium and potassium carbonate and ammonium f luoride was used for the uranium fluorescence test (ultraviolet lamp). Base d on the successful recovery of the uranium on a laboratory scale this proc ess is being considered for use with enriched uranium. (C) 2001 Elsevier Sc ience B.V. All rights reserved.