某砂岩铀矿床矿石中性浸出性能试验

Neutral Leaching of Uranium Ore from a Sandstone-type Deposit

对某砂岩型铀矿石开展不同O2剂量的中性浸出试验。结果表明,试验矿石中性浸出性能较差,铀浓度基本低于20mg/L,在25.2的高液固比条件下,铀浸出率仅为35.36%~41.85%;前期以六价铀浸出为主,浸出强度与HCO3^-浓度正相关;六价铀基本被浸出后,有O2、无O2的浸出差别明显,但O2剂量在30~200mg/L变化时浸出差别并不显著;相对高的pH有利于形成更稳定的铀酰络合物和降低铀的氧化还原临界电位,但应避免高pH引起碳酸钙沉淀。在地浸生产保持不低于800mg/L的HCO3^-和维持浸出液10~20mg/L的余氧是合适的。

A neutral multi-return leaching experiment was carried out on a sandstone-type uranium ore in Xinjiang under different O2 dose conditions.The results show that neutral leaching efficiency is poor for the interest ore.Peak of uranium concentration is generally lower than 20 mg/L,and uranium recoveries are only 35.36%-41.85 % under L/S of 25.2;Leaching intensity positively correlate with HCO3^- concentration significantly during early stage of leaching and the leached uranium is dominated by hexavalent uranium.Effect of O2 on uranium dissolution had been shown after hexavalent uranium in the ore exhausted.Difference of leaching results between test with O2 and without O2 is obvious.However,it is noteworthy that effect of O2 with different doses between 30 mg/L and 200 mg/L is not significant.Higher pH is beneficial for formation of uranyl dicarbonate and uranyl tricarbonate,and lowering redox critical potential of uranium oxidizing,but it is also needed to avoid high pH value which may lead to calcium carbonate precipitation.Maintaining more than 800 mg/L of HCO3^- in lixivant solution and 10-20 mg/L of dissolved oxygen in pregnant solution is recommended for neutral in-situ leaching process of that deposit.