Actinide(III)/Lanthanide(III) Separation Via Selective Aqueous Complexation of Actinides(III) using a Hydrophilic 2,6-Bis(1,2,4-Triazin-3-Yl)-Pyridine in Nitric Acid

Abstract

i-SANEX is a process for separating actinides(III) from used nuclear fuels by solvent extraction: Actinides(III) and lanthanides(III) are co-extracted from a PUREX raffinate followed by selective back extraction of actinides(III) from the loaded organic phase. This step requires a complexing agent selective for actinides(III). A hydrophilic sulfonated bis triazinyl pyridine (SO₃-Ph-BTP) was synthesized and tested for selective complexation of actinides(III) in nitric acid solution. When co-extracting Am(III) and Eu(III) from nitric acid into TODGA, adding SO₃-Ph-BTP to the aqueous phase suppresses Am(III) extraction while Eu(III) is extracted. Separation factors in the range of 1000 are achieved. SO₃-Ph-BTP remains active in nitric acid up to 2 mol/L. As a result of this performance, buffering or salting-out agents are not needed in the aqueous phase; nitric acid is used to keep the lanthanides(III) in the TODGA solvent. These properties make SO₃-Ph-BTP a suitable candidate for i-SANEX process development.

Keywords:

• i-SANEX
• liquid-liquid extraction
• aqueous complexation
• hydrophilic BTP
• actinides(III)
• lanthanides(III)
• separation
• nitric acid

ACKNOWLEDGMENT

Financial support from the Commission of the European Community (project ACSEPT, FP7-CP-2007-211 267) and the German Federal Ministry of Education and Research (BMBF contract numbers 02NUK012A and 02NUK012E) is acknowledged. ESI-MS analysis of SO₃-Ph-BTP was kindly performed by D. Girnt, Karlsruher Institut für Technologie, Institut für Anorganische Chemie.