Uranium release from a natural rock under near-natural oxidizing conditions

Summary

Understanding how uranium moves through the soil and groundwater is essential to determine the effectiveness of cleanup technologies. Uranium release and transport in the subsurface under oxic conditions have been reported to be mostly dependent on sorption onto Fe/Mn-oxide and complex interactions with organic substances. Available information in the literature, however, presents evidence of U retardation by natural sands. The aim of this investigation was to characterize U dissolution from a uraninite-containing rock (UO₂-rock) in different waters under test conditions relevant to U transport from mine tailings.For this purpose, not shakenbatch experiments were conducted with a constant amount of anUO₂-rockand different types of water (deionised, tap and mineral water). For comparison parallel experiments were conducted with 0.1M Na₂CO₃and 0.1M H₂SO₄. Furtherdissolution experiments using UO₂-rock together with dolomite and pyritewere conducted. The results indicate that carbonate addition enhanced U solubilization, whereas pyrite addition essentially slowed the initial U solubilization. It is shown that SiO₂and other rock constituents retard U transport.