砂岩型铀矿石无氧化剂碱法浸出特征

为研究无氧化剂条件下砂岩铀矿碱法溶浸水岩作用过程及铀浸出特征,在实验室开展了蒸馏水浸泡和无氧化剂碱法浸出试验。结果表明,无试剂的水岩作用盐离子综合体及水中天然溶氧作用,可使铀向水中弱迁移;无氧化剂碱法浸出铀迁移强度与HCO3-浓度正相关,HCO3-浓度700～900mg/L是对浸铀影响相对显著的区间;UO2(CO3)22-和UO2(CO3)34-是无试剂和碱法浸出溶解铀的主要存在形式,两者占比与HCO3-浓度和pH相关。缺少氧化作用的碱法浸铀强度较弱,液固比1.5∶1浸出40d铀回收率17.17%～22.37%,且浸出速度衰减较快,这与矿石中的铀以四价占优有关。尽管如此,在碱性地下水体系尤其是碱法地浸退役采区,长时间内铀的迁移仍不可忽视。

Alkali Leaching Characteristics of Sandstone-Type Uranium Ore without Oxidant

In order to study process of water - rock reaction and uranium leaching characteristics of sandstone-type uranium deposit during leaching without oxidant, two lab study of distilling water immersion and alkali leaching without oxidant was carried out. The results show that reagent-free water-rock salt ion complex and natural dissolved oxygen in water can weakly migrate uranium into water. Uranium migration intensity in oxidant-free alkali leaching is positively correlated with HCO3- concentration. The HCO3- concentration of 700~900 mg/L is a relatively significant interval for uranium migration. UO2(CO3)22- and UO2(CO3)34- are main dissolved forms of uranium complex in these two lab leaching study, and their proportion is related to HCO3- concentration and pH value. The alkali-impregnated uranium concentration is low since lacking oxidation. Uranium leaching rate for 40 days with L/S=1.5 is 17.17%~22.37%. Uranium leaching rate decays fast, which probably is related to tetravalent uranium content in ore. Nevertheless, the total migration amount of uranium over a long period of time cannot be ignored in alkaline groundwater systems, especially in alkali-drained mining areas.