Computational study on the extraction pattern of lanthanides with nitrilotriacetamide reagents

Kaneko, Masashi   ; Watanabe, Masayuki   ; Suzuki, Hideya; Matsumura, Tatsuro  

Nitrilotriacetamide (NTAamide) is considered to be a candidate for the separation reagent of minor-actinides (MA) from lanthanides (Ln) for an application to partitioning and transmutation. We have elucisdated the separation mechanism of Am from Eu with NTAamide by means of density functional theory (DFT). The present study applied the DFT method to Ln pattern of distribution ratio with NTAamide by solvent extraction. The extracted complex by NTAamide was modeled as [Ln(NTAamide)] (Ln = La, Ce, Nd, Sm, Eu, Gd) by referring the analogous crystal structure. Calculated geometry was indicated to belong to a pseudo-S point group with the Ln-N(amine) axis as C rotational axes. Gibbs energy difference indicated that NTAamide ligands more stably coordinate to light or middle Ln ions than La ion. This tendency was comparable to the experimental result of distribution ratio for Ln ions reported previously.