ICONE15-10583 Am(III)/Eu(III) SEPARATION WITH TPEN

Abstract

We are developing a new MA/Ln separation process with N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine, TPEN, and its derivatives for P&T technology. TPEN has six soft-donor sites as a kind of podand type molecule and can encapsulate a metal ion. TPEN has good selectivity of Am(III) from Ln(III) and has potential to establish partitioning of MA. We elucidated extraction behavior of Am(III) and Eu(III) using several organic solvents. The maximum separation factor of Am(III) from Eu(III), SFAm/Eu, was 270 at pH 4.80 with nitrobenzene as organic solvent. In synergistic extraction system, Am(III) was separated effectively with TPEN and decanoic acid diluted with 1-octanol. The synergistic extraction system was comfortable for reduction of secondary waste from the used organic solvent and operation management, because the organic phase of the extraction system was compatible with CHON principle and has low toxicity. The SFAm/Eu and the distribution ratios of Am(III) and Eu(III) were sufficient to establish the separation process. The extraction mechanism was considered ion-pair extraction. From the viewpoint of practical application, there is a problem in the characteristics of TPEN. One of them is hydrophilicity. The hydrophobicity of TPEN is improved by introducing alkyl groups. We synthesized the hydrophobic derivative N,N,N',N'-tetrakis(2-methylpyridyl) dibutylethylenediamine, tpdben, which has two n-butyl groups. Tpdben showed the maximum SFAm/Eu was 34 at pH 5.06. A hydrophobic derivative of TPEN which has selectivity of An(III) from Ln(III) was synthesized successfully.