Modulating the Ce(III)/Ce(IV) redox potential via chelation for the separation of Ce(IV) from Pr(III) by solvent extraction.

Carrier-free 143Pr is a promising radionuclide for bone pain palliation. However, its selective separation from neutron-irradiated cerium targets remains challenging, primarily due to the nearly identical aqueous chemistry of Ce(III) and Pr(III). Here, we present a coupled strategy that integrates coordination-regulated valence-state control with synergistic solvent extraction. 2,6-Pyridinedicarboxylic acid (DPA) is employed as a multidentate ligand to selectively stabilise Ce(IV) through strong coordination. This valence transformation is systematically validated by potentiometry, single-crystal X-ray diffraction, cyclic voltammetry, and X-ray photoelectron spectroscopy. Building on this, a 4,4,4-trifluoro-1-phenylbutane-1,3-dione (HBTA)/trioctylphosphine oxide (TOPO) extraction system is introduced to achieve selective separation of Pr(III). The results demonstrate that the HBTA/TOPO system exhibits a pronounced preference for Ce(IV) over Pr(III), with significantly enhanced separation factors across a broad pH range. This strategy provides a viable chemical route to produce high-purity carrier-free 143Pr from irradiated cerium targets. More broadly, it establishes a general framework for the selective separation of adjacent light lanthanides through coordination-mediated redox control.