2,2′‐(Methylimino)bis(N,N‐dioctylacetamide) (MIDOA), A New Tridentate Extractant for Technetium(VII), Rhenium(VII), Palladium(II), and Plutonium(IV)

* Ibaraki University, Bunkyo 2‐1‐1, Mito, Ibaraki 310‐8512.

Abstract

2,2′‐(Methylimino)bis(N,N‐dioctylacetamide) (MIDOA) was developed as a new extractant for technetium. MIDOA has a similar backbone to TODGA, N,N,N′,N′‐tetraoctyldiglycolamide, where the nitrogen atom bearing a methyl group replaces the ether oxygen in TODGA. MIDOA is highly lipophilic and ready to use in the HNO₃–n‐dodecane extraction system. The distribution ratio (D) for Tc(VII) is extremely high. In addition, Cr(VI), Re(VII), Mo(VI), W(VI), Pd(II), and Pu(IV) are well extracted by MIDOA. MIDOA has high selectivity toward certain oxometallates. The D(Tc) values decrease gradually with HNO₃, H⁺, and NO₃ ⁻ concentrations, and the log D vs log [MIDOA] dependence indicates the species extracted to be the 1:1 metal‐ligand complex. It is clear that MIDDA [2,2′‐(methylimino)bis(N,N‐didodecylacetamide)] and IDDA [2,2′‐(imino)bis(N,N‐didodecylacetamide)], which have structures analogous to MIDOA, have similar extraction behavior to that of MIDOA.

Keywords:

• Tc
• Re
• Pd
• Pu
• diamide
• tridentate
• MIDOA
• solvent extraction

ACKNOWLEDGMENTS

The authors would like to deeply thank Professor emeritus G.R. Choppin of Florida State University for the useful discussion, Professor K. Oguma of Chiba University for the discussion of the solution chemistry of Tc, Drs. Y. Sugo, M. Saeki, and Mr. T. Masaki of Japan Atomic Energy Agency for the useful comment of ligands for Tc extraction, and the staff of Wako‐Pure Chemical Ind. Ltd. for the organic synthesis.

Notes

* Ibaraki University, Bunkyo 2‐1‐1, Mito, Ibaraki 310‐8512.