| A uranium mine in Xinjiang has high carbonate and pyrite content and uneven distribution.In CO2+O2 in-situ leaching system,the interaction between leaching agent and rock and mineral leads to the formation of calcium carbonate,calcium sulfate and ferric precipitation in the process of element migration,resulting in the decrease of permeability and borehole water volume,affecting the uranium leaching efficiency.In order to explore the mechanism of precipitation and blockage in CO2+O2 in-situ leaching process of the uranium mine,typical minerals such as calcite,potash K-feldspar,kaolinite,pyrite and core ore samples related to uranium leaching are selected according to the leaching process and mineral composition characteristics of the ore.The static leaching kinetics experiment of"CO2+O2-groundwater-mineral"was carried out in the laboratory with pressure reactor at room temperature.The kinetic characteristics of mineral leaching and its hydrogeochemical influence law under different p H values（6.20～7.00）were studied,which provided theoretical basis for solving the problem of in-situ leaching precipitation blockage in this uranium mine.The results show that:（1）The dissolution of calcite is negatively correlated with the p H value of the system,while the dissolution of pyrite is positively correlated with the p H value;The dissolution of potash feldspar is less affected by p H value,while kaolin is insoluble in CO2+O2 leaching system.Kaolin is formed in the leaching process of potash feldspar,and the generated trace kaolin also has adsorption capacity,which shows strong adsorption at p H≥6.60.Its adsorption capacity of K+is greater than that of potash feldspar.In the kaolin leaching system,the mineral shows strong adsorption of K+,Na+,HCO3-and SO42-,and the higher the p H value is,the stronger the adsorption performance is.Iron hydroxide formed after pyrite oxidation at p H=7.00 can inhibit pyrite oxidation to a certain extent.（2）The dissolution rates of calcite and potash feldspar are linearly related to the logarithm of time,while pyrite is linearly related to the logarithm of time.The lower the dissolution p H of calcite is,the higher the p H of pyrite is,and the faster the dissolution rate is.The p H value of potash feldspar has relatively little influence on the dissolution rate.（3）The dissolution of calcite shows corrosion micropores or pits;The wavy dissolution of potash feldspar is found,and the clay mineral structure is found in the liquid phase.Kaolin exhibits its unique adsorbability,which results in the surface adsorption sites being occupied and the structure becoming dense and rigid.The surface of the pyrite becomes rough and tiny"droplet"particles rise,resulting in Fe（OH）3 precipitation and hematite adhering to the surface of the pyrite.（4）The leaching kinetics characteristics of pure minerals such as calcite,potash feldspar and pyrite are also presented in uranium leaching;However,compared with the leaching system of pure minerals,the dissolution rates of the four minerals in the leaching system of uranium ore are unstable to a certain extent,which may be related to the complex forms and occurrence states of minerals in the ore.（5）the hydrogeochemical simulation is the study of mineral dissolution,precipitation process is better,but I can’t fully meet the actual numerical simulation test process water rock system of solid and liquid state,causing the differences between simulation and actual data,it is still the current and future hydrogeochemical simulation to further study and solve the problem. |
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