Influence of humic acid on the sorption of uranium(IV) to kaolin

Nick Evans, Peter Warwick, Tara Lewis, Nick Bryan

    Research output: Contribution to journalArticlepeer-review


    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. © 2009 Springer-Verlag.
    Original languageEnglish
    Pages (from-to)25-30
    Number of pages5
    JournalEnvironmental Chemistry Letters
    Issue number1
    Publication statusPublished - Mar 2011


    • Humic acid
    • Linear additive model
    • Ternary systems
    • Uranium(IV)


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