Pyridine Polyaminocarboxylate Ligands for Use as Actinide-selective Holdback Reagents in Simplified TALSPEAK-like Extraction Systems

ABSTRACT

Three pyridine-based aqueous complexants have been synthesized and evaluated for their utility in an unbuffered TALSPEAK (Trivalent Actinide Lanthanide Separation by Phosphorus-reagent Extraction from Aqueous Komplexes) separation system as trivalent actinide-selective holdback reagents. The selectivity was established based on distribution studies using radiotracer ^152/154Eu, ²⁴¹Am, stable Ln, Y, and Th. In this system, these ligands selectively sequester Am from the lanthanides without the need for a secondary pH buffer. Am-lanthanide single-stage separation factors for Eu were found to be >70 for all three ligands and >15 for Nd. The results demonstrate that aqueous pyridine-based ligands represent viable alternatives to conventional aminopolycarboxylate complexants as actinide-selective holdback reagents in TALSPEAK-based actinide-lanthanide separation systems.

KEYWORDS:

• TALSPEAK
• pyridine-based ligands
• solvent extraction
• americium
• holdback reagents

Acknowledgments

ICP-MS analysis was performed by Dr. Scott Boroughs in the GeoAnalytical Lab in WSU School of the Environment. This research was supported by the U.S. Department of Energy, Office of Nuclear Energy, Fuel Cycle Research and Development program, Sigma Team for Minor Actinide Separations.