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

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 Eu-152/154, Am-241, 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.