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論文

Uranium (VI) sorption on illite under varying carbonate concentrations; Batch experiments, modeling, and cryogenic time-resolved laser fluorescence spectroscopy study

Mei, H.; 青柳 登; 斉藤 拓巳*; 香西 直文; 杉浦 佑樹; 舘 幸男

Applied Geochemistry, 136, p.105178_1 - 105178_8, 2022/01

Dissolved inorganic carbonate ions (DIC) present in groundwaters may affect both the aqueous and surface species of U(VI) due to its strong complexation ability with U(VI). However, it is still not clear how DIC affects U(VI) sorption on illite, which is one of the critical components in argillaceous rocks. In this study, the sorption of U(VI) on conditioned illite du Puy in presence of varying DIC concentrations (up to 250 mM DIC) as a function of pH was investigated by combining batch sorption experiments, surface complexation modeling, and the cryogenic time-resolved laser fluorescence spectroscopy (TRLFS). The distribution coefficients of U(VI) were sensitive to the DIC concentration, which decreased with an increase of DIC. There is no sorption of U(VI) under relatively high DIC concentrations (100 mM DIC). The U(VI) sorption behavior on illite was modeled by using the 2 Site Protolysis Non-Electrostatic Surface Complexation and Cation Exchange model. Two ternary surface complexation reactions with carbonate were needed to depict the experimental sorption data in addition to binary and ternary hydroxo surface complexation reactions employed for the description of U sorption to illite without carbonate. The cryogenic TRLFS revealed that U(VI) did sorb to illite in presence of high DIC concentration (up to 10 mM DIC). The spectra were unchanged with DIC at pH 8.5, suggesting the surface speciation of U(VI) remained the same. The decay curves were biexponential, which further indicated that at least two species were responsible for the sorption. Our finding will help to predict the transport and retention behaviors of U(VI) near radioactive waste repositories.

口頭

A Study of U(VI) sorption on illite under carbonate-rich environments; Batch experiments, TRLFS and modeling

Mei, H.; 青柳 登; 斉藤 拓巳*; 香西 直文; 舘 幸男

no journal, , 

Carbonate ions in groundwater are believed to influence migration behaviors of radionuclides in the geological environment by formation of aqueous carbonate complexes. However, little is known about the possibility of sorption of the radionuclide-carbonate complexes on minerals. We investigate U(VI) sorption on an illite mineral as functions of pH and carbonate concentrations, by combining cryogenic time-resolved laser fluorescence spectroscopy and surface complexation modeling. We will present the macroscopic and microscopic results of the speciation of U(VI) in the presence of carbonate and discuss the modeling of the sorption data, reflecting the speciation data.

口頭

TRLFS法を用いた微小な空隙内でのEuの吸着状態に関する研究

室田 健人*; 青柳 登; Mei, H.; 斉藤 拓巳*

no journal, , 

放射性廃棄物から溶出した放射性核種の地下環境中の動態においては、移行の過程での岩石や緩衝材内部の微小な空隙への吸着が重要な機構である。メソスケール(2$$sim$$50nm)やナノスケール(2nm以下)の微小な空隙内での水の性質がより大きな空隙内でのそれと異なることが報告されているが、イオンの吸着がどのように異なるのかは明らかでない。そこで、微小空隙を有する岩石の模擬物質として、異なる径のメソ空隙を持つメソポーラスシリカに対しEu(III)を吸着させ、その吸着状態をTRLFSで分析した。得られたデータを多変量解析することで、空隙サイズによってEu(III)の吸着状態がどのように変化するのかについて調べた結果を報告する。

口頭

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

Mei, H.; 青柳 登; 斉藤 拓巳*; 香西 直文; 杉浦 佑樹; 舘 幸男

no journal, , 

U(VI) sorption on illite in the presence of varying concentrations of carbonate ions was investigated by using the cryogenic TRLFS technique. The sorption species were differentiated by analyzing the fluorescent spectral shape and lifetime and using Parallel Factor Analysis.

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