Mechanisms of uranyl sorption
M. Del Nero, A. Froideval, C. Gaillard, G. Mignot, R. Barillon, I. Munier, A. Ozgümüs, 2004. "Mechanisms of uranyl sorption", Energy, Waste and the Environment: a Geochemical Perspective, R. Gieré, P. Stille
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Detailed knowledge of the reactions at the water/colloid/mineral interface is crucial to model accurately actinide behaviour in nature. In this paper, we review current knowledge of the sorption of actinides and of the mechanisms of sorption, with a particular focus on uranyl. Of major interest is the influence of the aqueous uranyl species (e.g., carbonate complexes, polynuclear species, colloids) on the uranyl sorption species. We present extended X-ray absorption fine structure (EXAFS) and X-ray photoelectron spectroscopy (XPS) studies on the coordination of uranyl onto an amorphous Al phase and onto quartz, respectively. Our XPS investigations show that two components having uranyl ions in very distinct coordination environments co-exist on quartz at high uranyl surface coverage, independently of the presence of uranyl carbonate complexes or uranyl colloids in solution. One component corresponds to polynuclear surface species and/or schoepite-like surface precipitates. In the case of similar uranyl concentrations and of high carbonate solution concentrations, polymeric uranyl species are formed on quartz, whereas no such surface species occurs on the Al phase. Uranyl is found on the Al phase as mononuclear uranyl carbonato surface complexes only. These results are of importance because they suggest that mineral surface characteristics strongly control the uranyl surface species in aquifers.
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Energy, Waste and the Environment: a Geochemical Perspective
This book provides incentives for further development of sustainable fuel cycles through a novel and interdisciplinary approach to an Earth science-related topic. The main focus is on geochemical concepts in immobilizing, isolating or neutralizing waste derived from energy production and consumption. The book also addresses the issue of using some types of energy-derived waste as alternative raw materials. Moreover, it highlights research on how certain wastes can be used for energy production, an increasingly important aspect of modern integrated waste management strategies. The main objectives are to: (a) identify the most serious environmental problems related to various types of power generation and associated waste accumulation; (b) present strategies, based on natural analogue materials, for the immobilization of toxic and radioactive waste components through mineralogical barriers; (c) discuss modern procedures for reuse of waste or certain waste components; and (d) review the importance of geochemical modelling in describing and predicting the interaction between waste and the environment.