Browsing by Author "Fenton, BR"

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    Characterisation of natural substrates with regard to application of surface complexation models
    (OECD, 2001) Waite, TD; Fenton, BR; Payne, TE; Lumpkin, GR; Davis, JA; McBeath, M
    While good correspondence between laboratory sorption data and surface complexation modelling results has been obtained for single oxide phase, much poorer correspondence has been obtained for natural substrates. This result arises, at least in part, from the difficulty in ascertaining the identity of sorbing surfaces and in assigning appropriate values for sorbing surface site concentrations. In an attempt to clarify the nature of possible sorbing phases, we have used a variety of techniques to investigate the surfaces of natural solid substrates from the Koongarra weathered zone. Based on insights gained from the surface characterisation studies, we have then proceeded to assess the applicability of various surface complexation modelling approaches as applied to U(VI) uptake. © 2001 OECD
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    Preferential association of adsorbed uranium with mineral surfaces: a study using analytical electron microscopy
    (Cambridge University Press/Springer Nature Limited, 1999-08-01) Lumpkin, GR; Payne, TE; Fenton, BR; Waite, TD
    Analytical electron microscopy (AEM) has been employed to characterize the distribution of U(VI) on several mineral substrates, including standard kaolinite samples and weathered rock samples from Koongarra, Australia. Results of this study reveal that pre-existing impurity phases play a significant role in the uptake of U(VI) on standard kaolinite samples. Using a natural sample from the weathered zone of the Koongarra uranium deposit, we have also demonstrated that U(VI) sorption is controlled by iron oxyhydroxides (predominantly goethite) which constitute a small fraction of the sample. Limited sorption of U(VI) was observed on the clay minerals of this substrate. Uptake of U(VI) by goethite increases with total uranium content up to the point of uranium precipitation, after which it decreases dramatically. Uranium precipitation is indicated by the appearance of a uranyl oxyhydroxide phase. © 1999 Materials Research Society