| This work reports on the partitioning of the uranyl ion between nitric acid and supercritical carbon dioxide (scCO2) in the presence of tributyl phosphate (TBP) as a function of temperature and pressure.; The distribution coefficients (DU) of uranium (0.2-2.5) were found to be highly dependent on the density of ScCO2. A decrease in Du was seen to correspond to a decrease in the concentration of TBP in the ScCO2 phase while no corresponding decrease in the concentration of TBP in the aqueous phase was observed.; The system was found to be non-ideal by comparison of the partition coefficients of TBP to the ratio of solubilities of TBP in pure scCO2 and water.; In the uranium-nitric acid-ScCO2-TBP extraction system, up to 92% of the nitrate in scCO2 phase was due to the formation and partitioning of the HNO3TBP complex even though its distribution coefficient is two to three orders of magnitude lower than that of the UO2(NO3)2·2TBP complex. |
