Solvent Extraction and Fluorescence Spectroscopic Investigation of the Selective Am(III) Complexation with TS-BTPhen

ABSTRACT

An americium(III) selective separation procedure was developed based on the coextraction of trivalent actinides (An(III)) and lanthanides (Ln(III)) by TODGA (N,N,N′,N′-tetraoctyl-diglycolamide), followed by Am(III) selective stripping using the hydrophilic complexing agent TS-BTPhen (3,3′,3ʺ,3ʺ′-[3-(1,10-phenanthroline-2,9-diyl)-1,2,4-triazine-5,5,6,6-tetrayl]tetrabenzenesulfonic acid). Distribution ratios were found at an acidity of 0.65 mol L⁻¹ nitric acid that allowed for the separation of Am(III) from Cm(III) (D_Cm > 1; D_Am < 1), giving a separation factor between curium and americium of SF_Cm/Am = 3.6 within the stripping step. Furthermore, Am(III) was readily separated from the lanthanides with the lowest selectivity for the Ln(III)/Am(III) separation being lanthanum with a separation factor of SF_La/Am = 20. The influence of the TS-BTPhen concentration on Am(III) distribution ratios was studied, giving a slope (logD vs. log[TS-BTPhen]) of approximately −1 for the stripping of An(III) with TS-BTPhen from the TODGA-based organic phase. Time-resolved laser fluorescence spectroscopy (TRLFS) measurements of curium(III) were used to analyze the speciation of Cm(III)-TS-BTPhen complexes. Both 1:1 and 1:2 complexes were identified in single-phase experiments. The formation of the 1:1 complex was suppressed in 0.5 mol L⁻¹ nitric acid but it was significantly present in HClO₄ at pH 3. Conditional stability constants of the complex species were calculated from the TRLFS experiments.

KEYWORDS:

• Am(III) separation
• TODGA
• selective stripping
• curium
• americium
• lanthanides
• partitioning
• TS-BTPhen
• americium–curium separation

Acknowledgments

TPH was provided by Manuel Miguirditchian, CEA Marcoule, France. Access to the Chemical Analysis Facility at the University of Reading is gratefully acknowledged.

Funding

Financial support was provided by the SACSESS-project under contract no. FP7-Fission-2012-323-282, which is part of the 7th Framework Program of the European Commission.

Additional information

Funding

Financial support was provided by the SACSESS-project under contract no. FP7-Fission-2012-323-282, which is part of the 7th Framework Program of the European Commission.