The beneficiation of sulfide ore using bacteria and their metabolites shows promise for reducing the use of chemicals during froth flotation. The role of growth conditions in the efficiency of bio-flotation is required prior to trialling larger scale experiments. In this study, scanning electron microscopy (SEM) was used to investigate the selective attachment of Leptospirillum ferrooxidans, L.f, to pentlandite and pyrrhotite. Bio-flotation tests were used to investigate the impact of bacterial growth conditions on extracellular polymeric substances (EPS) effectiveness as a depressant. The surface speciation resulting from exposure to EPS extracted from Po and PN rich cultures was investigated using X-ray photoelectron spectroscopy (XPS). The results show L.f exhibits selective attachment to pyrrhotite between 2 h and 168 h exposure via both indirect contact and non-contact mechanisms. Separation of pyrrhotite from pentlandite was achieved by exposing the minerals to L.f culture grown on pyrrhotite for 72 h in the absence of a PIPX collector and for 48 h in the presence of a PIPX collector. The results produced 45.2 and 94.4 % recovery of pyrrhotite, respectively. However, EPS supernatant extracted from L.f grown on pentlandite, conditioned for 72 h in the presence of a PIPX collector, provided the best separation efficiency through the selective depression of pentlandite, resulting in 95.8 % pyrrhotite recovery. Within 72 h, pentlandite exposed to EPS has hydrophilic complex carbon structures, significantly high concentrations of chemisorbed, physiosorbed water, and small concentrations of hydrophobic elemental sulfur at the surface. The EPS acts as a depressant decreasing pentlandite’s floatability and ensuring a successful separation with a PIPX collector.

中文翻译：

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通过生物浮选分离镍铁松石和磁黄铁矿

使用细菌及其代谢物对硫化物矿石进行选矿，有望减少泡沫浮选过程中化学品的使用。在试验更大规模的实验之前，需要了解生长条件在生物浮选效率中的作用。在本研究中，扫描电子显微镜 （SEM） 用于研究 Leptospirillum ferrooxidans， L.f 与镍铁矿和磁黄铁矿的选择性附着。生物浮选试验用于研究细菌生长条件对细胞外聚合物物质 （EPS） 作为抑制剂的有效性的影响。使用 X 射线光电子能谱 （XPS） 研究了暴露于从富含 Po 和 PN 的培养物中提取的 EPS 导致的表面形态。结果表明，L.f 在暴露 2 h 至 168 h 之间通过间接接触和非接触式机制表现出对磁黄铁矿的选择性附着。通过将矿物暴露在磁黄铁矿上生长的 L.f 培养物中 72 小时，在没有 PIPX 收集器存在的情况下暴露 48 小时，实现磁黄铁矿与喷黄铁矿的分离。结果分别产生了 45.2% 和 94.4% 的磁黄铁矿回收率。然而，从镍黄铁矿上生长的 L.f 中提取的 EPS 上清液，在 PIPX 收集器存在下活化 72 小时，通过镍黄铁矿的选择性凹陷提供了最佳分离效率，导致 95.8% 的磁黄铁矿回收率。在 72 小时内，暴露于 EPS 的镍铁矿具有亲水性络合碳结构，表面有明显高浓度的化学吸附、物理吸附水和低浓度的疏水性元素硫。EPS 起到抑制剂的作用，降低镍铁矿的可浮性，并确保与 PIPX 捕收剂成功分离。