Blockage and uranium migration via CO2 + O2 leaching within autoclave: a test study from Mengqiguer deposit in Yili Basin, Northwest of China

Multi‐Isotope Based Identification and Quantification of Oxygen Consuming Processes in Uranium Hosting Aquifers With CO2 + O2 In Situ Leaching

“…Pyrite oxidation under O 2 ‐enriched conditions, leading to the precipitation of iron minerals (Kameia & Ohmotob, 2000), would potentially cause pore‐clogging in sandstone U deposits and thus significantly reduced the leachate flow rate and the U available for leaching (K. Zhao et al., 2022; Y. Zhao et al., 2022). Furthermore, pyrite oxidation is thermodynamically more favorable than U oxidation and might compete for available O 2 during ISL, which would decrease the efficiency of U oxidation.…”

“…In situ leaching (ISL) is the main leaching method for sandstone‐type uranium ore (Abzalov, 2012; Mudd, 2001a, 2001b), mainly including acidic (Su et al., 2020; Zhou et al., 2020), neutral (Yang et al., 2022), and alkaline ISL (Abzalov, 2012). The neutral ISL (i.e., CO 2 + O 2 ISL) minimizes groundwater pollution during leaching and is considered to be more environmentally friendly (Yang et al., 2022; K. Zhao et al., 2022; Y. Zhao et al., 2022). As the inverse process of U mineralization, the injection of dissolved CO 2 and O 2 in the CO 2 + O 2 ISL substantially increases the redox potential and concentration of dissolved HCO 3 − , which oxidizes the reduced U(IV) to oxidized U(VI) and stimulates complexation of U with bicarbonate, including uranyl dicarbonate [UO 2 (CO 3 ) 2 2− ], uranyl tricarbonate [UO 2 (CO 3 ) 3 4− ], and ternary Ca/Mg‐UO 2 ‐CO 3 complexes (Su et al., 2020; Yang et al., 2022).…”