[2H07-12] Migration/Sorption 2

[2H09] Cryogenic TRLFS investigation on U(VI) sorption on illite in the presence of carbonate ions

*Huiyang Mei¹, Noboru Aoyagi¹, Takumi Saito², Naofumi Kozai¹, Yuki Sugiura¹, Yukio Tachi¹ (1. JAEA, 2. UTokyo)

Keywords:illite, U(VI), carbonate, TRLFS, sorption

Identification of the sorption species of radionuclides on minerals is important for understanding the retardation mechanism of host rock for radionuclides and the safety assessment for deep geological disposal of radioactive wastes. Particularly, the presence of relatively high concentrations of carbonate ions in sedimentary groundwater (> 2,000 mg/L as HCO₃^- in some cases) may inhibit the sorption of radionuclides on minerals obviously, and lead to quite low surface loading of radionuclides, which may increase the difficulty in identifying the sorption species. In light of this, we investigate U(VI) sorption on illite (one of the main constituents of argillaceous rock) as a function of HCO₃^- concentrations at fixed pH, by using cryogenic time-resolved laser fluorescence spectroscopy and Parallel Factor Analysis. In the talk, we will present the macroscopic and microscopic results of the surface speciation of U(VI) on illite in the presence of HCO₃^- and discuss the modeling of the sorption data, reflecting the speciation data.