Geochemical Characteristics and Uranium Neutral Leaching through a CO2 + O2 System—An Example from Uranium Ore of the ELZPA Ore Deposit in Pakistan

Abstract

Geochemical characterization studies and batch leaching experiments were conducted to explore the effects of a CO2 + O2 leaching system on uranium (U) recovery from ores obtained from an eastern limb of Zinda Pir Anticline ore deposit in Pakistan. The mineralogy of the ore was identified by Electron Probe Micro-analyzer (EPMA) and Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), showing that pitchblende is the main ore mineral. XRD was also used along with EPMA and SEM characterization data. Experimental results indicate that U mobility was readily facilitated in the CO2 + O2 system with Eh 284 mV and pH 6.24, and an 86% recovery rate of U3O8 was obtained. U speciation analysis implied the formation of UO2 (CO3)22− in the pregnant solution. The plausible mechanism may be attributed to the dissolved CO2 gas that forms carbonate/bicarbonate ion releasing oxidized U from the ore mineral. However, U recovery in the liquid phase was shown to decrease by higher U(VI) initial concentration, which may be due to the saturation of Fe adsorption capacity, as suggested by an increase in Fe concentration with increasing initial U(VI) concentration in the solid phase. However, further studies are needed to reveal the influencing mechanism of U(VI) initial concentration on U recovery in the solid phase. This study provides new insights on the feasibility and validity of the site application of U neutral in situ leaching.

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

“…Sandstone uranium (U) deposits, accounting for approximately 18% of world U resources, are the important primary materials for the generation of nuclear power (Asghar et al., 2020). Uranium roll‐front deposits are found in sandstone‐type U deposits (Cumberland et al., 2016), and are characterized by high contents of carbonate and argillaceous substances, low permeability, low ore grade, and complex hydrogeological conditions (Q. Ma et al., 2017; Su et al., 2020; Yue et al., 2020, 2021).…”

“…Groundwater physicochemical parameters critically control the U mobilization in aquifer systems containing U deposits, including pH, Eh, temperature, dissolved inorganic carbon, and reductants (Asghar et al., 2020; Blake et al., 2015; van Berk & Fu, 2017; Su et al., 2020). The U mobilization is closely linked to redox conditions, and the introduction of O 2 or NO 3 − into reduced aquatic systems leads to the dissolution of U‐bearing materials (Dutova et al., 2017; Pan et al., 2018; van Berk & Fu, 2017).…”

Quantifying the impact of mineralogical heterogeneity on reactive transport modeling of CO2 + O2 in-situ leaching of uranium

“…O 2 leaching system, where uranium is prone to soluble and transport under oxidizing and neutralweakly conditions, involves the injection of leaching solutions with O 2 (aq) as the oxidant through injection wells and the inorganic carbon promotes the release of adsorbed U ?6 from the Uranium-bearing mineral. Within the deposit, uranium is converted from the relatively insoluble tetravalent form of U ?4 into the water-soluble hexavalent form of U ?6 under oxidizing conditions, mainly exists as uranyl-carbonate complexes of UO 2 (CO 3 )2-2 and UO 2 (CO 3 )4-3; then the dissolved uranium is recovered through production wells and treated in surface plants (Langmuir 1978;Regnault et al 2012;Asghar et al 2020;Su et al 2020). The principal geochemical reactions between mining solutions and minerals as well as the host rock include oxidation and reduction, dissolution and precipitation, and aqueous complexation, among others.…”

Leaching Kinetics of Valuable Metals

“…Geochemical characterization studies and batch leaching experiments were conducted to explore the effects of a CO 2 + O 2 leaching system on uranium (U) recovery from ores obtained from an eastern limb of the Zinda Pir Anticline ore deposit in Pakistan [1]. This study provides new insights into the feasibility and validity of the site application of U neutral in situ leaching.…”