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The Shihongtan uranium deposit in northwest China is a sandstone-type deposit suitable for alkaline in-situ leaching exploitation of uranium. Alkaline leaching tends to result in CaCO_3 precipitation there by affecting the porosity of the ore-bearing aquifer. CaCO_3 deposits can also block pumping and injection holes if the formulation parameters of the leaching solution are not well controlled. However, controlling these parameters to operate the in-situ leaching process is challenging. Our study demonstrates that the dissolved uranium concentration in the leaching solution increases as HCO_3~-concentration increases. Therefore, the most suitable HCO_3~-concentration to use as leaching solution is defined by the boundary value of the HCO_3~-concentration that controls CaCO_3 dissolution-precipitation. That is, the dissolution and precipitation of calcite is closely related to pH, Ca~(2+) and HCO_3~-concentration. The pH and Ca~(2+) concentration are the main factors limiting HCO_3~-concentration in the leaching solution. The higher the pH and Ca~(2+) concentration, the lower the boundary value of HCO_3~-concentration, and therefore the more unfavorable to in-situ leaching of uranium.
The Shihongtan uranium deposit in northwest China is a sandstone-type deposit suitable for alkaline in-situ leaching exploitation of uranium. Alkaline leaching tends to result in CaCO_3 precipitation there by affecting the porosity of the ore-bearing aquifer. and injection holes if the formulation parameters of the leaching solution are not well controlled. However, controlling these parameters to operate the in-situ leaching process is challenging. Our study demonstrates that the dissolved uranium concentration in the leaching solution increases as HCO_3 ~ -concentration增大. Therefore, the most suitable HCO_3 ~ -concentration to use as leaching solution is defined by the boundary value of the HCO_3 ~ -concentration that controls CaCO_3 dissolution-precipitation. That is, the dissolution and precipitation of calcite is closely related to pH, Ca 2+ and HCO 3 ~ -concentration. The pH and Ca 2+ concentration are the main factors limiting HCO 3 ~ -co The higher the pH and Ca ~ (2+) concentration, the lower the boundary value of HCO_3 ~ -concentration, and therefore the more unfavorable to in-situ leaching of uranium.