Complexation of Actinide(III) and Lanthanide(III) with H₄TPAEN for a Separation of Americium from Curium and Lanthanides

Abstract

Previous studies have identified the TPAEN ligand as a potentially appropriate complexing agent in solvent extraction processes for the separation of americium (Am(III)) from the fission products including lanthanide (Ln(III)) and curium (Cm(III)) ions, a challenging issue for advanced nuclear fuel recycling. To get insight into the selectivity of this ligand, the complexation of selected trivalent Ln(III) and actinide (An(III)) cations with TPAEN was investigated in solution. First, the structure and stoichiometry of the TPAEN complex with Am(III) were characterized by extended X-ray absorption fine structure spectroscopy (EXAFS). Then complexation constants and thermodynamics data were acquired for the complexes using different methods: microcalorimetry for the Ln(III) cations, time-resolved laser fluorescence spectroscopy (TRLFS) for Eu(III) and Cm(III), and UV-visible spectroscopy for Nd(III) and Am(III).

Understanding the Stability Trend Along Light Lanthanide Complexes with an Ehtylenediamine‐Type Ligand: A Quantum Chemical Study

“…Compared to the experimental data from literature, the magnitudes of calculated ΔG are too large. However the calculated stability trend are in good agreement with the experimental stability trend (see Figure ), which can some extend proves that the method we used is suitable for the studied systems.…”

“…In 2015, S. Gracia et al., discovered H 4 TPAEN and its derivatives can be used as An 3+ /Ln 3+ , Am 3+ /Eu 3+ back‐extraction and separation agents . Two years later, Boubals and colleagues measured the complexation constants and the thermodynamic data of a series of Ln‐TPAEN complexes. These experimental data showed that light Ln‐TPAEN complexes’ stability first decreases from La to Ce, then increases from Ce to Nd, and finally decreases from Nd to Gd.…”

Influence of a Pre‐organized N‐Donor Group on the Coordination of Trivalent Actinides and Lanthanides by an Aminopolycarboxylate Complexant

“…Boubals et al. studied N , N , N′ , N′ ‐tetrakis[(6‐carboxypyridin‐2‐yl)methyl]ethylenediamine (TPAEN) in which all the acetate groups of EDTA have been substituted with 2‐methylpicolinate functionalities . When compared, the conditional constants describing the 1:1 stoichiometry for the complexation of the isoelectronic Nd 3+ and Am 3+ by EDTA and TPAEN show no significant impact on trivalent 4f/5f group differentiation due to the presence of the nitrogen‐containing picolinate groups (EDTA: β 101 (Am/Nd)=1.5, TPAEN: β 101 (Am/Nd)=1.4) .…”

“…studied N , N , N′ , N′ ‐tetrakis[(6‐carboxypyridin‐2‐yl)methyl]ethylenediamine (TPAEN) in which all the acetate groups of EDTA have been substituted with 2‐methylpicolinate functionalities . When compared, the conditional constants describing the 1:1 stoichiometry for the complexation of the isoelectronic Nd 3+ and Am 3+ by EDTA and TPAEN show no significant impact on trivalent 4f/5f group differentiation due to the presence of the nitrogen‐containing picolinate groups (EDTA: β 101 (Am/Nd)=1.5, TPAEN: β 101 (Am/Nd)=1.4) . The corresponding values for EDTA‐Mpic, when compared with DTPA‐type reagents, indicates that the incorporation of a picolinate arm lessens the An 3+ /Ln 3+ differentiation (DTPA: β 101 (Am/Nd)=25.1, DTTA‐BuA: β 101 (Am/Nd)=51.3, EDTA‐Mpic: β 101 (Am/Nd)=7.4) …”

Green Processing of Strategic Elements Based on Magnetic Nanohydrometallurgy

“…Such concentrates are usually processed by rather elaborate solvent extraction methods and ionic exchange. [44][45][46][47][48][49][50] However, it should be mentioned that lanthanide ions separation is far from trivial, since the elements exhibit very similar chemical properties, and the only possibility of success relies on the exploitation of the so called lanthanide contraction accompanying the increase of the atomic number. Such radial contraction determines the relative trends of the stability constants of the complexes, allowing some discrimination between the elements, which can be employed for separation purposes.…”