Solvent Extraction Investigations on Pu(IV) and Th(IV) Complexes with Hydrophilic SO₃-Ph-BTP and SO₃-Ph-BTBP Ligands

ABSTRACT

Complexation of Pu(IV) and Th(IV) cations by the title ligands – hydrophilic sulfophenyl triazinyl derivatives of bis-triazinyl-pyridine and -bipyridine – was studied in solvent extraction systems containing a TODGA extractant and one of these hydrophilic ligands. Stoichiometries and stability constants of the complexes formed in an acidic (HNO₃) aqueous phase have been determined. The Pu(IV) complexes are significantly stronger than their Th(IV) analogues. Only two complexes of each metal with SO₃-Ph-BTP (1:1 and 1:2) have been detected, and only one (1:1) with SO₃-Ph-BTBP; both numbers being less than expected based on the coordination numbers of the metal ions and on the denticities of the ligands. Possible reasons of this discrepancy are discussed.

KEYWORDS:

• Plutonium(IV)
• thorium(IV)
• hydrophilic BT(B)P ligands
• complexes
• stability constants

Acknowledgments

The authors are indebted to Dr. Andreas Geist of Karlsruhe Institute of Technology for his kind supplying the sample of SO₃-Ph-BTBP ligand used in this work. One of the authors (JN) gratefully recalls his postdoc stay at Chalmers University of Technology in 1975-76 on the invitation of the late Professor Jan Rydberg, as well as the further scientific contacts with Jan.

Preliminary results of the work were presented at the International Conference ATALANTE 2016 – Nuclear Chemistry for Sustainable Fuel Cycles. ^[23]

Additional information

Funding

The work was supported by the European Commission under project SACSESS, Contract number (FP7-Fission-2012-323282); and also by the CEA Marcoule and the Ministry of Science and Higher Education of Poland under the project of Cooperation Agreement (between the Institute of Nuclear Chemistry and Technology and the CEA Marcoule) number 31/CA/2014.