IMPROVEMENT OF BIOLEACHING EFFICIENCY BY THE GAS PHASE CONTROL

为了提高生物浸出效率，研究了控制反应室供气比例的方法。首先考察了气体组成浓度比对氧化亚铁硫杆菌氧化亚铁离子活性的影响。在7%的二氧化碳浓度和5 ~ 10%的氧气浓度下，亚铁离子的氧化活性得到最大的提高。以黄铁矿为模型硫化物矿物，进行了氧化亚铁钩端螺旋体的生物浸出试验。有可能黄铁矿几乎完全溶解，而浸出过程中硫酸的生成受到抑制。对含难溶性铜矿物如铝辉石、黄铜矿的铜精矿进行了生物浸出试验。精矿未加银离子处理时，只有黄铁矿被溶解，铜矿物几乎未被溶解。进行生物浸出时，该精矿经银离子处理后，促进了铜矿物的溶解，抑制了黄铁矿的溶解。结果表明，银离子在矿物表面的取代反应和铁离子的氧化反应都是促进这些铜矿物溶解的必要条件。由于氧化亚铁硫杆菌和/或氧化亚铁钩端螺旋体快速地将矿物溶解产生的亚铁离子与铁离子进行再生，因此为了促进这种再生反应，控制气体组成是重要的。传统火法处理含砷铜精矿难度较大，而采用生物浸出法处理含砷铜精矿使其在实际操作中处理成为可能。

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.