Comparison of four bidentate phosphoric and diamide compounds for the extractability of actinides

Using four bidentate phosphonate and diamide ligands (L), the extraction of Am(III), Th(IV), Np(V) and U(VI) was studied and their extraction species and extractability in these extractants were discussed. The extractant containing the phosphoric oxygen has stronger chelation than that with the carbonyl oxygen atoms. The molar ratios in the main chemical forms extracted are 1:3 for Am:L, 1:1 for Th:L and Np:L and 1:2 for U:L from the relationship between log D(An) and log[L]. The order of D in actinides with the different oxidation states is U(VI)>Th(IV)>Am(III)>Np(V), which shows the different order from that for HDEHP and HTTA, namely Th(IV)>U(VI)>Am(III)>Np(V). It is clear that BDPPM, a diphosphoric dioxide extractant, has high extractability towards all An used here. (author)