The effect of the total sulphate concentration on the rate of pyrite dissolution was investigated in batch, bioleach tests on a high-grade concentrate at 35 C, 50 C and 65 C. Good microbial activity was achieved for concentrations up to 42 g/L sulphate. However, higher concentrations resulted in decreased ferrous oxidation kinetics, with the solution potential profiles showing "lag periods" at the highest sulphate concentration. The bioleach results showed that the rate of pyrite dissolution decreased markedly above an average sulphate concentration of 55 g/L for all three temperatures, with the adverse effect on the dissolution kinetics being more pronounced at 50 C and 65 C. As a result of this, increased temperature has no beneficial effect on the rate of dissolution at concentrations of sulphate above 55 g/L. High extents of pyrite dissolution (90% to 98%) were achieved at all three temperatures irrespective of sulphate concentration, with almost identical extents of sulphide oxidation. Rates of pyrite dissolution under bioleaching conditions agree well with those derived under similar conditions from abiotic dissolution experiments and electrochemical measurements. This important observation confirms the so-called indirect mechanism for the bioleaching process in the case of pyrite and also that the mixed potential model can be used to quantitatively describe both abiotic dissolution and biotic dissolution of pyrite in acidic solutions.
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机译:分批研究了总硫酸盐浓度对黄铁矿溶解速率的影响,在35 C,50 C和65 C的高品位精矿上进行了生物浸出试验。对于浓度高达42 g / L的硫酸盐,微生物活性良好。但是,较高的浓度会导致亚铁的氧化动力学下降,溶液的电位曲线在最高硫酸盐浓度下显示出“滞后时间”。生物浸出结果表明,在所有三个温度下,黄铁矿的溶解速率均明显高于55 g / L的平均硫酸盐浓度,在50°C和65°C下对溶解动力学的不利影响更为明显。当硫酸盐浓度高于55 g / L时,升高的温度对溶解速率没有有益的影响。不论硫酸盐浓度如何,在所有三个温度下均实现了高度的黄铁矿溶解(90%至98%),并且硫化物的氧化程度几乎相同。黄铁矿在生物浸出条件下的溶解速率与在类似条件下从非生物溶解实验和电化学测量得出的速率非常吻合。这一重要发现证实了在黄铁矿情况下所谓的生物浸出过程的间接机理,并且混合势能模型可用于定量描述酸性溶液中黄铁矿的非生物溶解和生物溶解。
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