Supercritical CO2 Extraction of Uranium(VI) from HNO3 Solution Using N,N,N‘,N‘-Tetrabutyl-3-oxapentanediamide

Distribution ratio ( D U ) and extraction efficiency ( E U ) of uranium(VI) were investigated using N, N, N ‘, N ‘-tetrabutyl-3-oxapentanediamide (TBOD) in supercritical carbon dioxide (Sc-CO 2 ) . Five diamide derivatives were synthesized; TBOD was found to be the most suitable extractant through solubility data. The composition ratio of uranium(VI) extraction was described as a relation of UO 2 (NO 3 ) 2 TBOD, through the measurement of D U as the concentration ranges of HNO 3 and TBOD. Comparing this with the extractability of TBP, the D U of TBOD was superior to that of TBP in Sc-CO 2 by 2 orders of magnitude. The results showed that TBOD could be substituted for tri- n -butyl phosphate (TBP) in Sc-CO 2 extraction of uranium(VI). Uranium, fission products (Cs, Cd, Mo, Ba), and corrosion products (Ni, Fe, Cr, Co) were extracted with TBOD in Sc-CO 2. Over 90% each of actinides (U, Th) and lanthanides (La, Ce, Gd) were extracted. But, fission products and corrosion products were extracted at a low efficiency of less than 20%, which showed the possibility of selective separation in these metals.