IMPROVEMENT OF BIOLEACHING EFFICIENCY BY THE GAS PHASE CONTROL

点击翻译按钮获取中文摘要

In this study, it was examined that ratio of gas composition supplied reaction chambers was controlled in order to improve the efficiency of the bioleaching. First, the effect of ratio of concentration of gas composition on ferrous ion oxidizing activity of Thiobacillus ferrooxidans was examined. Ferrous ion oxidizing activity was most improved at 7% of carbon dioxide concentration and 5〜10% of oxygen concentration. Bioleaching with Leptospirillum ferrooxidans was carried out, using the pyrite as a model sulfide mineral. It was possible that the pyrite almost perfectly dissolved, while the generation of the sulfuric acid in the leaching was suppressed. Bioleaching experiments on the copper concentrate including poor solubility copper minerals such as enargite and chalcopyrite were also carried out. When the concentrate was not treated with silver ion, only pyrite was dissolved and copper minerals were not almost dissolved. When the bio leaching was carried out, after this concentrate was treated with silver ion, the dissolution of copper minerals was promoted and the dissolution of the pyrite was suppressed. It was proven that both of substitution reaction in mineral surface by silver ion and oxidation reaction by ferric ion were necessary to promote the dissolution of these copper minerals. Since Thiobacillus ferrooxidans and/or Leptospirillum ferrooxidans rapidly reproduces the ferrous ion produced by the mineral dissolution with ferric ion, the control of the gas composition is important in order to promote this regeneration reaction. Though in the conventional pyrometallurgy method, the processing of the copper concentrate including arsenic minerals was difficult, the handling in the real operation becomes possible by bioleaching method developed this time.