Study On Acclimating The Bacteria To Oxidize The Heavy Concentration Of Ferrous Ion And Applying It To Ieaching

Bioleaching has some advantages of using resource fully, low cost and little environmental pollution, so it has already been researched widely and been applied to the industry domestic and abroad.In this dissertation, the ability of Thiobacillus Ferrooxidans (T.f) contributing to the process by oxidizing ferrous ions to ferric ions is utilized, the initial concentration of ferrous ions in bacteric solution is enhanced step by step to acclimate bacteria to adapt. And then, the ferric ions-bearing bacteric solutions is used as leaching agent, which acquired from acclimation process to leach the arsenic-bearing sulfide copper concentrate. The two processes of bio-oxidizing and leaching separated are in order to avoid the toxicity of arsenic and reduce the effect of the complicated components in ore.The effect of pH, temperature, initial [Fe2+], reaction time in the bio-oxidizing process and the granularity of grain, the concentration of the pulp, pH, initial [Fe3+], leaching time in the leaching process are investigated.The optimal reactive conditions have been obtained by bio-oxidizing experiment as the following: initial pH is low (Eq. 1.5); solution temperature is 25~30癈; initial [Fe2+] is no heavier than 90g/l; reaction time is 7-8 days. In addition, the well activity of bacterium and enough oxygen supply are two key factors in this process. As a result, when the initial [Fe2+] is 30g/L, the oxidizing ratio of the ferrous ions can reach 72.33%.The optimal reactive conditions have also been obtained by leaching experiment as the following: the granularity of grain is -200mesh~-300mesh, the concentration of the pulp is 3%-5%; initial [Fe3+] is 5~30g/l; leaching time is about 10 days; initial pH is 1.5; the leaching ratio of arsenic is 52.16%. On two compare experiments betweenbacterium-bearing leaching and pure chemical leaching [Fe2(SO4)3], results show that the bacterium plays an important role in leaching process. The reaction mechanism is complex of bacterium contributing to the process by oxidizing ferrous ions to ferric ions, the so-called "indirect mechanism" of bacterial oxidation and bacterium oxidizing the concentrate directly, the so-called "direct mechanism" of bacterial oxidation.