Selective separation of samarium(III) by synergistic extraction with -diketone and methylphenylphenanthroline carboxamide

Hasegawa, Yuko*; Tamaki, Sayaka*; Yajima, Hirofumi*; Hashimoto, Bunji*; Yaita, Tsuyoshi

Synergistic extraction of trivalent lanthanides (Lns(III)) with pivaloyltrifluoroacetone (HA) and N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide (MePhPTA) was evaluated across the Ln series. The distribution ratio () of Sm(III) under an identical condition was the largest among all Lns(III). The separation factor (SF) between Sm(III) and Nd(III) (SF=/) was 2.0 and SF between Sm(III) and Eu(III), (/) was 1.4. Upon analyzing the extraction data in detail on the basis of mass balance, it was found that the dominant extracted species of light Lns(III) was a stable ternary complex consisting of Ln(III), HA, and MePhPTA (B), namely, LnAB, while the dominant extracted species of heavy Lns(III) was the ion pair, [LnAB]ClO. The complex for Pr(III) was very stable. It suggests that LnA can form two 5-membered rings with MePhPTA, and the size of Pr(III) matches to the distance between the donor atoms in MePhPTA.