Highly efficient plutonium scavenging by an extraction chromatography resin containing a tetraaza-12-crown-4 ligand tethered with four diglycolamide pendent arms

An efficient extraction chromatography resin, containing tetraaza-12-crown-4 functionalized with four diglycolamide moieties, was evaluated for the separation of plutonium. This chromatography resin yielded very large distribution coefficients for Pu⁴⁺ (>10⁵) in 0.5 – 6 M HNO₃ feed solutions. Various physicochemical properties such as sorption kinetics, Pu⁴⁺ sorption mechanism, and its sorption capacity were investigated. The sorption kinetics, following a pseudo-second-order model, showed that about 10 minutes of equilibration was sufficient for >99.9% sorption of Pu⁴⁺. The sorption of Pu⁴⁺ on the resin followed the Langmuir monolayer model, which was confirmed by a theoretical calculation based on the kinetic model. The Pu⁴⁺ sorption on the resin was driven by a large exothermic enthalpy change (ΔH = −31.4±2.2 kJ/mol) and a positive entropy change (ΔS = 224±15 J/mol/L). The resin could sorb a maximum of 12.1±0.8 mg of Pu per gram of resin, which is equivalent to 1:2 metal/ligand complex on the resin. The Pu⁴⁺ from the resin phase was completely stripped with 0.5 M oxalic acid. A possible application of this resin for the separation / pre-concentration of Pu⁴⁺ was successfully demonstrated in the column mode.