Sequestration of Actinides by an Extraction Chromatography Resin Containing a Triaza-9-crown-3 Functionalized Diglycolamide

We prepared a new extraction chromatography resin by coating a diglycolamide (DGA) ligand having three DGA moieties tethered to a triaza-9-crown-3 scaffold (TAM-3-DGA) on an inert solid support. This resin was evaluated for the separation of actinides and lanthanides from moderate acid solutions of 0.01-6 M HNO₃. The distribution coefficient (K_d) values for trivalent and tetravalent actinides (Am³⁺, Np⁴⁺, and Pu⁴⁺) on the resin were large enough (>1 × 10⁴ mL/g) between 2 and 6 M HNO₃ for its real application in separating these minor actinides. The metal ion sorption mechanism studied for Eu³⁺ and Pu⁴⁺ indicated the existence of a chemisorption phenomenon. The sorption energies for Eu³⁺ and Pu⁴⁺ were 12.1 ± 0.72 and 18.5 ± 0.5 kJ/mol, respectively. The resin capacity was 13.9 ± 0.3 mg of Eu³⁺ and 11.7 ± 0.4 mg of Pu⁴⁺ per g of the resin, corresponding to the formation of a 1:1 metal/ligand complex for the Eu³⁺ ion and a 1:2 metal/ligand complex for the Pu⁴⁺ ion. The sorbed Eu³⁺ and Pu⁴⁺ ions from the resin phase were effectively eluted with complexing reagents like HEDTA and oxalic acid, respectively. The column capacity was ∼80% of the batch equilibrium value for both Eu³⁺ and Pu⁴⁺ ions.