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

The hydrolysis of uranium hexafluoride and its conversion to 'ammonium diuranate' yields an alkaline solution containing ammonium fluoride and low concentrations of uranium. The recovery of the uranium has the advantage of saving this valuable metal and the avoidance of unacceptable discarding the above 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 adsorption on to an anionic ion-exchange resin. The 'ammonium diuranate' filtrate 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 uranyl fluoride was achieved by choosing a suitable pH and flow rate of the uranium-bearing solution on to the resin column. The effluent ammonium fluoride 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 fluoride uranium carbonate is eluted from the resin with a more concentrate ammonium 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 flux prepared using a mixture of sodium and potassium carbonate and ammonium fluoride was used for the uranium fluorescence test (ultraviolet lamp). Based on the successful recovery of the uranium on a laboratory scale this process is being considered for use with enriched uranium. (C) 2001 Elsevier Science B.V. All rights reserved.