Distribution behaviour of U(VI), Th(IV) and Pa(V) from nitric acid medium using linear and branched chain extractants

The extraction behaviour or 1M solutions of tri-2-ethylhexyl phosphate (TEH P), di-2-ethyl hexyl isobutyramide (D2EHIBA), tri-n-butyl phosphate (TBP) a nd di-n-hexyl hexanamide (DHHA) in n-dodecane towards U(VI), Th(IV) and PBM in the presence of 220 g/L of Th from nitric acid medium has been studied. The limiting organic concentrations (LOC) of thorium (g/L) for 1 M TBP and 1 M DHHA are evaluated as 31, 20 ( at 1 M HNO3) and 25, 13 (at 4 M HNO3) r espectively. The distribution ratio (D) values of U(VI), Th(IV) and Pa(V) i n the presence of thorium (220 g/L) at 1 M HNO3 suggest that branching in t he alkyl group of amides suppresses the extraction considerably. In view of the selective extraction of U over Th by 5 % TBP in THOREX process at 4 M HNO3, distribution behaviour is also studied employing a lower concentratio n (0.18 M) of extractant for comparison purpose. Separation factor (S. F.) values for U(VI) over Th(IV) under different experimental conditions consis tently varied in the order: D2EHIBA > DHHA > TEHP > TBP. the quantitative e xtraction of U-233 from a synthetic mixture containing U-233 (10(-5) M). Pa -233 (10(-11) M) and thorium (220 g/L) at 1 M HNO3 using 1 M solution of D2 EHIBA in n-dodecane is achieved in three stages. Stripping and reusability studies of D2EHIBA have also been carried out.