@article{e5c02794f7d848d994e47e74d76815fb,
title = "Adsorption and diffusion of selenite on Boda Claystone Formation",
abstract = "This study provides adsorption and diffusion data of selenite on Boda Claystone Formation (BCF) which is a potential host rock of a deep geological disposal of high-level radioactive waste. The experiments were performed on two diverse core samples: one albitic claystone sample characteristic for the entire BCF and one pyrite containing sample sparsely occurring in BCF. The experiments were carried out under atmospheric conditions. Batch experiments were carried out to study the kinetics of adsorption at a high initial concentration (1.2 × 10−3 M), the adsorption isotherms and reversibility were investigated in the 10−10–10−3 M concentration range. Adsorption onto petrographic thin sections was done to study the elemental distribution on the microscale and the oxidation state of selenium. The maximum of the distribution coefficient was found as Kd ≈ 200 L/kg and a decrease was experienced around 10−6–10−7 M equilibrium concentration, which showed similarities to other argillaceous rocks. Isotopic exchange experiments revealed reversibility of selenite adsorption. Diffusion was studied with through-diffusion and in-diffusion experiments. Using X-ray fluorescence, despite a low initial concentration of 2.3 × 10−5 M in the in-diffusion experiment, a meaningful diffusion profile of selenium could be obtained, from which the selenite apparent diffusion coefficient Dappselenite = (1.5–4.3) × 10−14 m2/s and the selenite rock capacity factor αselenite = 1.4–2.2 were determined. As selenium species are redox sensitive the oxidation state of adsorbed species was studied with X-ray absorption near edge structure spectroscopy on Se–K edge. Adsorbed selenium remained in +IV oxidation state, however reduction was experienced on the pyritic sample.",
keywords = "Adsorption, Boda Claystone Formation, Clay rich media, Diffusion, Selenite mobility",
author = "Ott{\'o} Cz{\"o}mp{\"o}ly and Margit F{\'a}bi{\'a}n and Kor{\'a}nyi, {Tam{\'a}s I.} and G. Nagy and Horv{\'a}th, {Z. E.} and Ivo Zizak and Simone Pollastri and Marc Aertsens and J{\'a}nos Os{\'a}n",
note = "Score=10 Funding Information: The research was supported by the European Joint Programme on Radioactive Waste Management (EURAD) Fundamental understanding of Radionuclide Retention (FUTURE) work package (EU grant agreement number: 847593). We acknowledge Elettra Sincrotrone Trieste for providing access to its synchrotron radiation facilities and for financial support under the IUS internal project (Elettra No. 20215774 and 20220423) and acknowledge the staff of XAFS and XRF beamlines for collecting additional data during in-house beamtime. We also thank the Helmholtz-Zentrum Berlin f{\"u}r Materialien und Energie for the allocation of synchrotron radiation beamtime. The courtesy of the Public Limited Company for Radioactive Waste Management (PURAM, Hungary) for providing the samples for analysis is also appreciated. Funding Information: The research was supported by the European Joint Programme on Radioactive Waste Management (EURAD) Fundamental understanding of Radionuclide Retention (FUTURE) work package (EU grant agreement number: 847593). We acknowledge Elettra Sincrotrone Trieste for providing access to its synchrotron radiation facilities and for financial support under the IUS internal project (Elettra No. 20215774 and 20220423) and acknowledge the staff of XAFS and XRF beamlines for collecting additional data during in-house beamtime. We also thank the Helmholtz-Zentrum Berlin f{\"u}r Materialien und Energie for the allocation of synchrotron radiation beamtime. The courtesy of the Public Limited Company for Radioactive Waste Management (PURAM, Hungary) for providing the samples for analysis is also appreciated. Publisher Copyright: {\textcopyright} 2023 The Authors",
year = "2023",
month = sep,
day = "1",
doi = "10.1016/j.clay.2023.106997",
language = "English",
volume = "241",
journal = "Applied Clay Science",
issn = "0169-1317",
publisher = "Elsevier B.V.",
}