基于地球化学模拟分析杂质矿物对酸法地浸采铀的影响

Influence of Impurity Mineral on Acid Leaching Uranium Based on Geochemical Simulation

为探明酸法地浸采铀过程中杂质矿物对铀浸出的影响,以分批浸出试验为基础,采用反应路径模拟探讨杂质矿物对铀浸出机制的影响,利用反应溶质运移模型探讨杂质矿物对铀浸出化学场时空特征的影响。模拟结果表明:方解石、黄铁矿、赤铁矿会与铀矿竞争酸,竞争由强至弱依次为方解石、赤铁矿、黄铁矿,其中黄铁矿在酸浸条件下溶解较弱,但生成的低价硫和亚铁离子能降低溶浸液的Eh值,导致铀浸出减少,赤铁矿在酸浸条件下因耗酸而降低溶浸液的酸度,但又促进黄铁矿的溶解,进而影响铀的浸出;在时间上,杂质矿物会使铀的溶解迁移存在不同程度的滞后,铀的溶解-沉淀旋回周期延长,整个模拟矿层沥青铀矿完全溶解时间更长,铀浸出速率降低;在空间上,杂质矿物会使模拟矿层中铀矿溶解范围减小,铀矿溶解-沉淀旋回过程中沉淀量增加,U(Ⅵ)迁移浸出所需时间延长,浸出铀的迁移累积峰值变化不同。

In order to find out the effect of impurity minerals on uranium leaching in acid leaching process,based on batch leaching test,the mechanism of impurity minerals affecting uranium leaching was discussed by using reaction path simulation,and the time-space characteristics of impurity minerals affecting uranium leaching chemical field was discussed by using reaction solute transport simulation.The simulation results show that calcite,pyrite and hematite compete with uranium ore for acid,and the competition from strong to weak is calcite,hematite and pyrite.Pyrite dissolves weakly in acid leaching,but the generated low valence sulfur and ferrous ions can reduce the Eh of leaching solution,resulting in the reduction of uranium leaching.Hematite consumes acid,reduces the acidity of leaching solution,but promotes the dissolution of pyrite,thus affecting uranium leaching.In time,impurity minerals will delay the dissolution and migration of uranium in varying degrees,prolong the period of dissolution precipitation cycle of uranium and the complete dissolution time of pitchblende in the whole simulated ore bed,and reduce the uranium leaching rate.In space,impurity minerals will reduce the dissolution range of uranium in the simulated ore bed,during the dissolution precipitation cycle with the increase of precipitation,the time required for U(Ⅵ)migration and leaching is prolonged,and the peak value of migration and accumulation of uranium leaching is different.