Microanalysis of silica-based adsorbent for effective recovery of radioactive elements

For effective recovery of radioactive elements by adsorbents using polymer-immobilized silica (SiO₂-P) supports, the microstructure of SiO₂-P particles impregnated with octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide as extractants and their change with the crosslinking degree of polymer (CDP) were investigated using scanning transmission X-ray microscopy (STXM) and extended X-ray absorption fine structures (EXAFS) analyses; further, their relation with adsorption/elution behavior was discussed. The results of STXM analysis suggested that the polymer is distributed within several hundred nanometers of the pore surface, and its distributions are spread by the increase of CDP. In addition, the capture of impurity molecules such as H₂O by polymers with high CDP was indicated. EXAFS analyses showed that the local structure around adsorbed europium ions is similar irrespective of the CDP. The adsorption/elution tests demonstrated that a higher CDP inhibited the elution of adsorbed europium ions from the adsorbent.