The kinetics and mechanisms of simulated British Magnox waste glass dissolution as a function of pH,silicic acid activity and time in low temperature aqueous systems |
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| Institution: | 1. Department of Earth Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK;2. Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK;3. British Nuclear Fuels plc, Research & Technology, Waste Technology Group, Sellafield, Cumbria, CA20 1PG, UK;4. British Nuclear Fuels plc, Environmental Technology, Rutherford House (R002), Risley, Warrington, Cheshire, WA3 6AS, UK;1. Computational Techniques Branch, Canadian Nuclear Laboratories, 286 Plant Rd, Chalk River, Ontario, Canada, K0J 1J0;2. Department of Engineering Physics, McMaster University, 1280 Main St. W., Hamilton, Ontario, Canada, L8S 4L8;1. Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan;2. Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu 808-0196, Japan;1. CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette, France;2. CEA, INSTN, UEPTN, F-91191 Gif-sur-Yvette, France;1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, No .2019 Jialuo Highway, Shanghai, China;2. University of Chinese Academy of Sciences No. 19 (A) Yuquan Road, Shijingshan District, Beijing, China;3. Shanghai Tech University No. 393 Middle Huaxia Road, Shanghai, China;4. China Institute of Atomic Energy P.O. Box 275-50, Beijing 102413, China |
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| Abstract: | Dissolution of a simulated British Magnox waste glass is governed by two pH-dependent processes. At low pH, dissolution is governed by reactions occurring predominantly at non-Si sites and residual Si-rich gels develop at the glass surface as B, Al and modifier cations are selectively leached. Here, extensive proton promoted hydrolysis of BO and AlO bonds is coupled with hydration and ion exchange processes. Hydrolysis of siloxane bonds governs the rate of dissolution at high pH and the glass dissolves congruently as the silicate network breaks down extensively. Differences in the surface chemistries and morphologies of glass samples reacted in strongly acidic and highly alkaline media reflect the net effects of these processes. The rate of the congruent dissolution process is influenced by the activity of silicic acid. The results are compared with published data for other glass formulations and are discussed in the context of proposed kinetic dissolution models. |
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