New macrocyclic ligand incorporated organosilicas: Co-condensation synthesis, characterization and separation of strontium in simulated high level liquid waste

A new category of organosilica adsorbents functionalized with macrocyclic ligand cis-dicyclohexano-18-crown-6(cis-DCH18C6) were synthesized for selective strontium separation. The cis-DCH18C6 molecule, well-known as an excellent complexing agent of strontium, was elaborately modified for immobilization in the organosilica matrix by co-condensation. 13C and 29Si solid-state NMR, XPS, FT-IR, ESEM, and elemental analysis were employed to characterize the structure and surface morphology of the organosilicas. Due to the improved surface properties and supramolecular recognition to the ion, the functionalized organosilicas showed favorable adsorption capacity and selectivity to the strontium in HNO3 media. The sample of Crown-75 showed a high distribution coefficient (185.3 cm3/g) of strontium in 1 mol/L HNO3 solution. For practical purpose, the separation of strontium in the simulated high level liquid waste (HLLW) from the spent fuel of a light water reactor (LWR) was investigated. The Kds of strontium as well as dozens of other metals present in the HLLW were obtained. Moreover, the radiolytic and hydrolytic stability of the organosilicas was evaluated. It revealed that the organosilicas had excellent resistance against gamma-ray irradiation and nitric acid treatment. These novel DCH18C6-functionalized organosilicas possess a promising future for the separation of the strontium in radioactive liquid waste.