嗜酸氧化亚铁硫杆菌在沥青铀矿石浸出中的作用

Leaching mechanism of pitchblende by Acidithiobacillus ferrooxidans

为了研究沥青铀矿石的细菌浸出机理,设计了有菌有铁、有菌无铁及无菌无铁3种矿粉浸出试验及有菌无铁、无菌无铁两种试块浸出试验,检测了矿粉浸出体系中细菌的浓度、pH值、Eh、亚铁离子浓度、总铁离子浓度及铀浓度的变化,分析了浸出尾渣中O、Mg、K、P、S、Fe、U等元素的含量,观测了浸出前后试块表面形貌的变化。结果表明,在沥青铀矿石浸出过程中,嗜酸氧化亚铁硫杆菌可以高效氧化浸出体系中的亚铁、还原态硫及元素硫,使得浸出体系中的Eh升高和pH值降低;有菌有铁浸出体系中,高浓度的细菌、高浓度的铁、低pH值和高Eh可加速铀矿石的浸出和提高铀矿石的浸出率;有菌无铁浸出体系中,即使总铁离子浓度很低,但由于有细菌的存在,同样可以加速铀矿石的浸出和提高铀矿石的浸出率。有菌无铁的试块浸出中,试块表面出现了许多溶蚀坑,这表明细菌对铀矿石具有直接氧化作用。

In order to study the mechanism for bacteria leaching of pitchblende, several leaching experiments were conducted, including three powder leaching experiments with bacteria and iron, with bacteria and without iron, without bacteria and iron, and two specimen leaching experiments with bacteria and without iron, without bacteria and iron. Variations in the concentrations of bacteria, ferrous ions, total iron ions and uranium ions, pH value and redox potential of the leaching solutions were monitored in the powder leaching systems. The contents of O, Mg, K, P, S, Fe and U in the tailings from powder leaching experiments were analyzed and the surface morphology of the samples after leaching were observed. Results of the powder leaching experiments show that Acidithiobacillus ferrooxidans can effectively oxidize ferrous ions, sulfur in reduction state and elemental sulfur, resulted in the increase in redox potential and the decrease in pH value. In the leaching system with bacteria and iron, the leaching of uranium from the ore can be accelerated and the leaching rate is increased with the higher concentrations of bacteria and total iron ions, the lower pH value and the higher redox potential. Although the concentration of the total iron ions is relatively low in the leaching system with bacteria and without iron, the bacteria can also accelerate the leaching of uranium from the ore and increase the leaching rate. Results of the specimen leaching experiments indicate that the pitchblende ore has been directly oxidized by the bacteria, since corrosion pits can be observed on the specimen surface in the leaching system with bacteria and without iron. Corrosion pits have not been observed on the specimen surface in the leaching system without bacteria and iron.