Study On Mechanism Of Uranium Leaching And Solute Migration During The CO₂+O₂ In-situ Uranium Leach Mining Process In The Mengqiguer Deposit

The Mengqiguer deposit in XINJIANG is the main production base of natural uranium in China.The content of carbonate and pyrite is high and unevenness.Although using CO₂+O₂neutral leaching technology,chemical plugging still exist.In order to prevent chemical clogging and improve the uranium leaching effects,this paper study the mechanisms of uranium leaching and element migration during neutral leaching process.It carried out“Groundwater+NH₄HCO₃+CO₂+O₂”,“tail liquid+CO₂+O₂”and“two pumping and six injecting wells”tests.It used Mineralogy,Hydrogeochemistry,Groundwater dynamics and Numerical simulation methods to study the uranium leaching characteristics,influencing factors and migration mechanism of U,C,S,Fe,Ca,Mg between the fluid and minerals.The Uranium ore are mainly pitchblende,little coffinite and brannerite.The mineral form and occurrence state are suitable for CO₂+O₂neutral leaching.Uranium leaching and migration intensity are positively correlated with ore grade,injection and extraction ratio,oxidation intensity and HCO₃^-ion concentration.During the solid-liquid-gas interactions in the CO₂+O₂in-situ leaching system,the migration intensity of various elements is different.49.6%-53.1%of Fe were oxidized,inflowed into solution and finally precipitated from the solution.17.6%of S in uranium ores migrated from mineral to solution and existed in the form of SO₄^2-.The Ca migrated from the mineral phase to the solution under the action of CO₂.When the p H value was higher than 6.6,it precipitated again.The migration intensity of K,Na,Mg and Al were weaker than Fe and S.During the field leaching test,HCO₃^-ion arrived in pumping wells from injecting wells within 14 or 15 days.After 60 days,it can form the stable seepage field controlled by injecting.H^-ion arrived in pumping wells within 26 days,which lagged behind the HCO₃^-ion.It can form stable weakly acidic chemical fields after 110 days.HCO₃^-and H⁺ion are good indicators for stability seepage field and weak acidic chemical field.The front line of HCO₃^-and SO₄^2-arrived at the pumping well at the same time.It shows the migration of these components is unimpeded.The migration of H⁺,Ca²⁺and Mg²⁺lagged behind the solution seepage,reflecting that H⁺was consumed and Ca²⁺?Mg²⁺precipitated in the migration.Controlling the amount of CO₂and O₂at 550?700 mg/L and 200?300 mg/L,the HCO₃^-concentration can be kept in 800 mg/L,p H value kept between 6.2 to 6.5,Eh value kept higher than 200 m V.It can satisfy the effective leaching and migration for uranium.It can avoid calcium sulfate and calcium carbonate precipitation.It is a reasonable technological parameter for Mengqiguer deposit.