Consideration on modeling of Nb sorption onto clay minerals

山口 徹治; 大平 早希; 邉見 光; Barr, L.; 島田 亜佐子; 前田 敏克; 飯田 芳久

Radiochimica Acta, 108(11), p.873 - 877, 2020/11

https://doi.org/10.1515/ract-2020-0006

Sorption distribution coefficient (Kd) of niobium-94 on minerals are an important parameter in safety assessment of intermediate-depth disposal of waste from core internals etc. The Kd of Nb on clay minerals in Ca(ClO) solutions were, however, not successfully modeled in a previous study. The high distribution coefficients of Nb on illite in Ca(ClO) solutions were successfully reproduced by taking Ca-Nb-OH surface species into account. Solubility of Nb was studied in Ca(ClO) solutions and the results were reproduced by taking an aqueous Ca-Nb-OH complex species, CaNb(OH), into account in addition to previously reported Nb(OH) and Nb(OH). Based on this aqueous speciation model, the Ca-Nb-OH surface species responsible for the sorption of Nb on illite in Ca(ClO) solutions was presumed to be X_OCaNb(OH). Although uncertainties exist in the speciation of aqueous Ca-Nb-OH species, the result of this study proposed a possible mechanism for high distribution coefficient of Nb on illite in Ca(ClO) solutions. The mechanism includes Ca-Nb-OH complex formation in aqueous, solid and surface phases.

Adsorption mechanisms and models of Sr, Np, Pu and Am in loess media (Joint research)

田中 忠夫; 向井 雅之; 前田 敏克; 松本 潤子; 小川 弘道; Li, S.*; Wang, Z.*; Wang, J.*; Guo, Z.*; Zhao, Y.*

JAERI-Research 2002-034, 20 Pages, 2002/12

JAERI-Research-2002-034.pdf:1.1MB

Sr(II),Np(V),Pu(IV)及び Am(III)の黄土への吸着メカニズムと吸着モデルを吸着脱離実験結果に基づき検討した。Sr及びNpの分配係数はPu及びAmより23桁小さい値であった。分配係数が小さなSr及びNpの黄土への吸着は、主にイオン交換によって支配されていた。一方、黄土に吸着した大部分のPu及びAmは、鉄やマンガンの水酸化物・酸化物や腐植物質との選択的な化学結合によって支配されていた。得られた吸着脱離実験結果に基づき、黄土中における放射性核種の移行を解析する手法を確立するため、吸着の可逆性,反応速度等を考慮した吸着モデルを提案した。