Study on phenanthroline carboxamide for lanthanide separation; Influence of amide substituents

Simonnet, M.   ; 小林 徹 ; 下条 晃司郎   ; 横山 啓一  ; 矢板 毅

Simonnet, M.; Kobayashi, Toru; Shimojo, Kojiro; Yokoyama, Keiichi; Yaita, Tsuyoshi

Phenanthroline carboxamide compounds are promising for lanthanide intra-series separation. This paper presents a study on the effect of structure modification of phenanthroline carboxamides onto the extraction of the whole lanthanide series. The study consists in theoretical calculations, extraction experiments of the 14 stable lanthanides and EXAFS analyses of Nd and Dy complexes. The comparison of the tridentate monocarboxamides and the tetradentate dicarboxamides shows different trend in the series extraction, although both preferentially extract the light lanthanides. The amide substituents, although not directly coordinating the metal ions, were also found to impact the distribution ratio, most probably due to a modification in the internal polarity of the molecules. This latter effect, if extrapolated to other nitrogen-based ligands such as pyridines or triazines, can be used to further fine-tune extractants for a process improvement.