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Retention of uranium(VI) by Ca-bentonite at high ionic strength and high pH studied by batch sorption tests and TRLFS
Philipp, T.; Schmeide, K.; Stumpf, T.;
The retention behavior of U(VI) by Ca-bentonite was studied in saline and alkaline solution via batch sorption experiments and TRLFS. At pH 8.5-9.5 sorption is lower in the presence of CO2 due to the formation of weakly sorbing uranyl carbonate species, which have been observed to dominate speciation up to pH 10 by TRLFS. In the pH range10-12 the U(VI) retention is almost complete both in the absence as well as in the presence of CO2 (carbonate concentrations between 1∙10-4 and 1∙10-3 M). This retention appears to be a combination of adsorption of uranyl hydroxo complexes and precipitation of uranium due to an altered solubility of U(VI) induced by ions leached out of the bentonite. At pH > 12 the U(VI) retention decreases again, pre-sumably due to the formation of the strongly negatively charged 1:4 uranyl hydroxo complex.
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    7th International Conference on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, 24.-27.09.2017, Davos, Schweiz

Publ.-Id: 25006 - Permalink