Experimental study and modeling of the sorption of uranium(VI) onto olivine-rock |
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| Institution: | 1. Quintessa Ltd, The Hub, 14 Station Road, Henley-on-Thames RG9 1AY, UK*;2. Quintessa Ltd, 633/635 Birchwood Boulevard, Birchwood, Warrington WA3 7QU, UK;3. Savage Earth Associates Ltd, Queens Park, Bournemouth BH8 9EE, UK;4. Radioactive Waste Management Ltd, Building 587, Curie Avenue, Didcot OX11 0RH, UK;1. Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China;2. Key Laboratory of Poyang Lake Basin Agricultural Resource and Ecology of Jiangxi Province, College of Land Resource and Environment, Jiangxi Agricultural University, Nanchang 330045, China;3. Physical Chemistry and Soft Matter, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands;4. Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039, China |
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| Abstract: | The sorption of U(VI) onto the surface of olivine has been experimentally investigated at 25 °C under an air atmosphere as a function of pH, solid surface to volume ratio and total U concentration. Sorption has been observed to decrease as the extent of carbonate complexation of U(VI) in solution increases, which is attributed to the competition between aqueous and solid ligands for the coordination of U. The experimental results have been interpreted by means of two different approaches: (1)a semi-empirical model, exemplified by the application of a Langmuir isotherm and (2) a non-electrostatic thermodynamic surface complexation model which includes the formation of the surface species: >SO–UO2+ and >SO–UO2(OH). The following stability constants for these species have been determined from the thermodynamic analysis: K(>SO–UO2+)=289±71 and K(>SO–UO2(OH))=(3.4±0.4)×10?6. The comparison of the sorption of U onto olivine with granites of different origin indicate that the use of this mineral as additive to the backfill of deep high level nuclear waste repositories could retard the migration of U from the repository to the geosphere. |
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