pH effect on Re(VII) and Se(IV) diffusion in compacted GMZ bentonite |
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| Institution: | 1. Department of Life Science, Huzhou University, 313000 Huzhou, PR China;2. China Institute of Atomic Energy, P.O. Box 275(88), 102413 Beijing, PR China;3. Jiangxi Provincial Water Conservancy Planning Design and Research Institute, 330000 Nanchang, PR China;4. China Resources New Energy Group Co., Ltd., 999077, Hong Kong, China;1. College of Environmental Science and Engineering, Beijing Key Lab for Source Control Technology of Water Pollution, Beijing Forestry University, Beijing, 100083, China;2. Key Laboratory of the Three Gorges Reservoir Region''s Eco-Environment, State Ministry of Education, Chongqing University, Chongqing, 400045, China;1. Landesamt für Bergbau, Energie und Geologie (LBEG), Stilleweg 2, D-30655 Hannover, Germany;2. School of the Environment, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia;3. AMPHOS 21 Consulting S.L., Pg. García i Faria 49-51, 1-1, 08019 Barcelona, Spain;4. Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, D-30655 Hannover, Germany;1. Institute of Ecological and Environmental Sciences, Sichuan Agricultural University – Chengdu Campus, Chengdu, Sichuan 611130, PR China;2. Rural Environment Protection Engineering & Technology Center of Sichuan Province, Sichuan Agricultural University – Chengdu Campus, Chengdu, Sichuan 611130, PR China;3. Department of Information Integration and Consultation, Library of Sichuan Agricultural University – Chengdu Campus, Chengdu, Sichuan 611130, PR China;1. Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, Southeast University, Nanjing 210096, PR China;2. Institute of Ecological and Environmental Science, Sichuan Agricultural University, Sichuan 611130, PR China |
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| Abstract: | In a high-level radioactive waste (HLW) repository, pH has an impact on the solubility, migration, and adsorption of radionuclides. Thus, understanding the effects of pH on the diffusion of radionuclides is essential for long-term disposal of HLW. In this work, the diffusion behaviors of Re(VII) and Se(IV) in compacted Gaomiaozi (GMZ) bentonite at different pH have been investigated by a through-diffusion method. The effective diffusion coefficient, i.e., De values of Re(VII) and Se(IV) were in the range of (1.0–2.4) × 10?11 m2/s at pH 3.0–10.0 and (0.38–2.3) × 10?11 m2/s at pH 3.0–9.0. In the case of Re(VII), the De values remained almost unchanged probably because ReO4? was the dominant species in the pH range of 3.0–10.0. In the case of Se(IV), whose predominant species were HSeO3? at pH < 9.0 and SeO32? at pH ≥ 9.0, the De values decreased by a factor of 3–6 at pH 9.0, i.e., De (pH < 9.0)/De (pH 9.0) ≈ 3–6, implying that the species with a higher valence state had a stronger anion exclusion effect. The decrease in De values can be explained by the diffusion species of Se(IV). Additionally, the rock capacity factor α decreased with the increase of pH. HSeO3? was absorbed on GMZ bentonite with distribution coefficient Kd values in the range of (1.0–2.5) × 10?4 m3/kg at pH ≤ 8.0, whereas SeO32? was negligibly sorbed at pH > 8.0. |
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| Keywords: | Diffusion Se(IV) Re(VII) pH GMZ bentonite |
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