Abstract: In order to determine the effect of shear friction caused by different pulp concentrations on the biooxidation performance of leaching bacteria, silica microsphere particles (100 μm) with a particle size close to that of ore particles were used instead of ore as the solid phase to study the biooxidation performance of two moderately thermophilic bacteria Leptospirillum ferrooxidans (L.f) and Acidithiobacillus caldus (A.c). The tolerance of these two moderately thermophilic leaching bacteria to shear friction was preliminarily determined. The density of silica microspheres was close to that of pulp, giving them a similar solid phase sedimentation rate. They were stable in the acidic environment of bioleaching, did not release metal ions or consume nutrient substrates, and can maintain the stable microenvironment required for the metabolism of bioleaching bacteria. In this study, a down-pressure four-pitched impeller stirred tank reactor was used for testing. It was found that for L.f, with the increase of silica solid holdup, the increase rate of redox potential value slowed down, the reaction time extends, and its oxidation performance was reduced by shear friction. When the solid holdup reached 25% (w/v), L.f showed obvious damage. As a sulfur-oxidizing bacteria, an increase in solid holdup also resulted in intensified shear friction within the A.c reaction system, as well as a reduction in bacterial oxygen uptake rate. However, when excessive elemental sulfur powder was initially added, residual sulfur powder remained when the oxidation of A.c was completed. Even at 30% (w/v), where oxidation time was significantly prolonged, the bacteria still maintained good oxidation activity. The addition of the baffle was beneficial to the uniform dispersion of the gas and improved the dissolved oxygen concentration and oxygen mass transfer efficiency, but the shear friction effect was enhanced accordingly, causing further damage to bacteria. As the solid holdup increased to 20% (w/v) and above, the baffles inflicted severe damage on L.f, resulting in a marked increase in oxidation time. For A.c, the baffle improved the mixing uniformity of elemental sulfur powder, and effectively broke up bubbles, which was conducive to the uptake of oxygen by A.c, and exerted a certain compensatory effect on the oxidation reaction. At 30% (w/v), the oxidation time of A.c was not significantly prolonged.

Key words: biological pre-oxidation, stirring tank, oxidizability, mechanical damage, solid holdup, moderately thermophilic bacteria

摘要： 为确定固含率导致的剪切摩擦作用对生物氧化微生物活性的影响，本研究采用粒径接近矿石颗粒的100 μm二氧化硅微球颗粒作为固相替代物，在10 L搅拌反应釜中，对工业常用的氧化亚铁钩端螺旋菌(Leptospirillum ferrooxidans, L.f)和喜温嗜酸硫杆菌(Acidithiobacillus caldus, A.c)的微生物氧化性能进行探究。实验表明，对于L.f，随着体系中固含率提升，其氧化速率显著减缓，反应时间延长，微生物氧化活性有所降低。在挡板作用下，剪切摩擦对微生物造成的损伤效应更加明显，当固含率达25% (w/v)时已造成明显活性损伤。而对于A.c，固含率的提高强化了剪切摩擦作用，也会使其氧化性能下降。挡板的加入有利于破碎气泡，提高溶解氧浓度，对A.c的氧化过程有一定补偿作用，即使在30% (w/v)的高固含率下，该菌种仍可保持较好的氧化效果。

关键词: 生物预氧化, 搅拌槽, 氧化性能, 机械损伤, 固含率, 中度嗜热菌