Solvent extraction of uranium from alkaline solutions using Aliquat 336

Abstract

Molybdenum-99 is the greatest important isotope in nuclear medicine because its daughter Technetium-99m is commonly used in medical radiographic imaging. During the dissolution process of the irradiated target plates containing enriched uranium, uranium and some fission products are precipitated as mixed hydrated oxides to form the residue. This residue is commercially valuable, as it could form the feedstock for recovering and purifying uranium from the other fission products and transuranium elements for further production of the (Mo-99) medical isotope. (Plutonium Uranium Redox Extraction PUREX) is a well-known process for the extraction of uranium using the conventional acid route. There are however unfavourable proliferation issues with the Purex process due to the possibility of recovering plutonium in a pure form. Uranyl solution was generated as simulant of real nuclear waste for this study. The objective of this research was to evaluate different organic extraction solvents/diluents that can remove uranium from the nuclear waste and to determine the most effective extraction ligand/organic solvent combination in extracting uranium only, from alkaline media. Experimental parameters included: different concentrations of ammonium carbonate at pH 9, uranium, concentration of Aliquat 336 and different phase volume ratio were investigated and concentration of sodium carbonate at pH 10,11 and 12. The stripping agents of uranium from loaded organic solution using sodium hydroxide, ammonium sulphate and ammonium carbonate were studied. The results indicate that organic extractant Aliquat 336 in Toluene extracted 82% of the uranium from the feed solution after 30 minutes decreasing to 76% after 60 minutes. 0.2M of ammonium carbonate and 0.01M uranium in phase volume ratio of 1:5 with Aliquat 336 concentrations of 15% are the best extraction parameters that can be used to extract uranium with an extraction percentage of 98%. It was found that when the ammonium sulphate strip was at pH 2, the uranium strip efficiency reached more than 90%.