Chromatographic separation of nuclear rare metals by highly functional xerogels

The uptake behavior of Cs, Pd, Mo, Re and Tc on highly functional xerogels (microcapsules: MCs), the characterization of MCs and the chromatographic separation for the simulated HLLW (28 components) and the spent fuel solution were examined by batch and column methods. Granular MCs of ammonium tungstophosphate (AWP) encapsulated with calcium alginate (CaALG) matrices exhibited a high selectivity towards Cs⁺, and a relatively large separation factor (α) of Cs⁺/Rb⁺ above 10 was obtained. The mutual separation of Cs⁺/Rb⁺ was thus accomplished through the packed column. The novel MCs of insoluble ferrocyanides (CuFC) prepared by direct method had an excellent selectivity towards Pd²⁺; relatively large K_d values above 10⁵ cm³/g were obtained. The chromatographic separation of Pd²⁺/Rh³⁺/RuNO³⁺ in simulated HLLW was accomplished using thiourea-HNO₃ eluent. The extractants (LIX63, MIDOA and TOA) can be encapsulated with the alginate polymer gels. The MCs enclosing the above extractants exhibited high selectivity towards Mo(VI), Re(VII) and Tc(VII) ions, and the chromatographic separation for simulated HLLW and spent fuel solutions was accomplished by using stepwise elution methods. The precise separation system combined the above processes is effective for the recovery of nuclear rare metals from HLLWs. (author)