Influence of humic acid on the sorption of uranium(IV) to kaolin |
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Authors: | Nick Evans Peter Warwick Tara Lewis Nick Bryan |
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Institution: | (1) Department of Chemistry, Loughborough University, Ashby Road, Loughborough, LE11 3TU, UK;(2) Centre for Radiochemistry Research, School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK |
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Abstract: | Safety assessments for radioactive waste disposal require estimations of the migration of radionuclides in soils. The influence
of humic acid (HA) on the sorption of uranium in its +4 oxidation state to kaolin has been examined from pH 4 to 8, with HA
concentrations of 15–200 ppm. In the absence of HA, 20–40% of the U(IV) was in solution, with more sorption occurring at higher
pH. The presence of HA solubilised up to 90% of the uranium with higher solubilities at higher HA concentrations and higher
pH values. Uranium sorption was mapped against HA sorption, and it was found that there was a lower level of U(IV) sorption
than can be accounted for by just measuring HA sorption. However, this effect got less marked as the pH rose. Sensitivity
analysis indicated that the fraction of surface-bound HA is the controlling parameter for modelling in these systems. |
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