Novel polysiloxane resin functionalized with dicyclohexano-18-crown-6 (DCH18C6): Synthesis, characterization and extraction of Sr(II) in high acidity HNO3 medium

Graphical abstract: A novel kind of polysiloxane resin functionalized with dicyclohexano-18-crown-6 (DCH18C6) was synthesized for the extraction of Sr (II). The functionalized resin showed excellent thermal and hydrolytic stability, as well as the separation capacity for strontium ions in high acidity HNO3 medium (5.0 M). Highlights: ► Novel polysiloxane resin functionalized with DCH18C6 ligand was synthesized. ► Structure, thermal property and surface morphology of the resin were characterized. ► The resin showed excellent thermal and hydrolytic stability. ► The resin can extract Sr (II) in high acidity HNO3 medium. - Abstract: A novel kind of polysiloxane resin functionalized with dicyclohexano-18-crown-6 (DCH18C6) was synthesized through a post-modification approach. The DCH18C6 moieties bearing amino groups were firstly prepared, followed by covalent grafting to a silica precursor P-(CH2)3-Cl (Where P represents a 3-dimentional polymerized silica matrix) based on nucleophilic substitution reaction. 29Si and 13C solid-state NMR, FT-IR, XPS, TGA, ESEM and elemental analysis were employed to systematically characterize the structure, thermal property and surface morphology of the functionalized resin. The results indicated that the DCH18C6 ligands were successfully bonded to the polysiloxane resin with a satisfactory grafting degree (33.6 wt.%). Due to the robust organosilica framework and the covalent immobilization of the ligands, the functionalized resin had excellent thermal stability and acid resistance. Batch experiments showed that the resin could effectively separate Sr(II) in high acidity mediums. The distribution coefficient (Kd) of 43.6 cm3/g could be achieved in 5.0 mol/L HNO3 solution. The influences of contact time and acidity of HNO3 on the resin's extraction performance were examined. The reusability and the selectivity to Sr(II) over interference ions were investigated. The DCH18C6-functionalized resin might be potentially applied for the radiostrontium removal in the high level liquid waste (HLLW).