Uptake of uranium by carbonate crystallization from reduced and oxidized hydrothermal fluids

• Published in: Chemical geology Vol. 564; p. 120054
• Main Authors: Gabitov, Rinat, Migdisov, Artas, Nguyen, Anh, Van Hartesveldt, Noah, Perez-Huerta, Alberto, Sadekov, Aleksey, Sauer, Kirsten Benedict, Baker, Jason, Paul, Varun, Caporuscio, Florie, Xu, Hongwu, Roback, Robert
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 20-03-2021; Elsevier
• Subjects: GEOSCIENCES; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; uranium, calcite, uptake, hydrothermal
• ISSN: 0009-2541; 1872-6836
• DOI: 10.1016/j.chemgeo.2020.120054

This work evaluated the immobilization of uranium (U) through incorporation into calcite under reduced and oxidized conditions. We investigated how much U could be entrapped by calcite crystallizing in chloride solutions in autoclaves at temperatures from 162 to 300 °C. The oxidation state of U was set by controlling oxygen fugacity via redox buffers. Uranium was introduced into calcite growth media as a solid oxide compound or U aliquot. We found the uptake of tetravalent U by calcite is higher than that of hexavalent U by up to four orders of magnitude. We estimate that crystallization of a few mg of calcite immobilizes all dissolved U when 1 kg of solution is saturated with UO2 under reduced hydrothermal conditions.
•Aragonite transforms to calcite and uptakes U from solutions at 162–350 °C.•U4+ has a higher affinity of incorporating into calcite compared with U6+.•Calcite has strong potential in immobilizing U4+ at 250-3000 °C.