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

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...

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Published in:Chemical geology 2021-03, Vol.564, p.120054, Article 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
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Language:English
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Summary: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.
ISSN:0009-2541
1872-6836
DOI:10.1016/j.chemgeo.2020.120054