In situ pilot-scale demonstration of a novel mineral processing biotechnology for recovering metals from lateritic ores (International)

镍和钴是现代文明在许多应用中使用的两种关键金属。尤其是钴，由于其对“绿色技术”（如新一代电动和混合动力汽车所用电池的能量储存）的重要性，以及由于其大部分生产集中在世界上被认为可能不稳定的地区，因此被归类为“战略金属”。开采原生矿石生产的镍和钴大多来自还原（硫化物）矿物，但全球可开采的镍储量（特别是）大部分包含在氧化矿石中，最明显的是红土，广泛分布在（大多数）热带地区。虽然存在从红土矿石中提取有价值金属的技术，但这些技术大多在高温高压下操作，因此能耗高，碳足迹大。最近，已经描述了从褐铁矿红土中提取镍和钴的微生物机理，其在大气压和环境温度（30 - 40 C）下操作，并在实验室规模上进行了证明。生物采矿通常被认为是获得金属的“绿色”方法，并且已经用于获得铜超过50年。班戈尔大学与采矿业联合开发的新技术大大扩展了可生物加工的金属矿石的范围。来自世界不同地区（包括亚洲，非洲和南美洲）的矿山的褐铁矿石已在当前NERC赞助的项目（特别关注钴）的框架内进行了试验，并且所有这些都已被证明适用于使用这种新方法（称为“还原矿物溶解”）的生物处理。其中包括来自巴西皮奥伊州一家新的采矿企业的材料，该企业的所有者是NERC项目财团的积极成员。皮奥伊矿尚未全面投产，生物处理方案与目前设想的作业方案（用浓硫酸堆浸）相比，有几个明显的主要优点。其中包括：（i）消除了将大量浓酸运输到偏远矿场的需要（既昂贵又危险）;（ii）消除了购买用于长期硫酸生产的制酸设备的需要（其成本相当于矿山总资本成本的约25%）;（iii）提高从矿石中提取金属的速度和程度的潜力。在目前的NERC项目中，原始的还原性矿物溶解方案已被微调，以最大限度地减少或消除使用酸来中和褐铁矿石中的矿物溶解时产生的碱度的需要。相反，酸是由专门的细菌从元素硫原位产生的。还原性矿物溶解方法从实验室扩大到中试规模是一个完美的时机，而皮奥伊矿场已经有了所需的大型柱，这大大促进了这一点。该项目将首先生产由该过程中使用的专门细菌定殖的硫，将其从英国运送到皮奥伊的矿山，在那里它将与矿石（和额外的硫）结合并包装成一个大的（4米高）柱。该柱和对照（酸浸）柱将以再循环流动模式运行6-7个月，届时大多数金属将被提取。然后将这些柱拆卸，如果结果符合预期，则用于工艺的下一阶段（堆浸;超出本项目的范围）。该示范工厂将提供必要的数据，有助于促进这种新型生物采矿方法在世界各地红土矿的应用。

Nickel and cobalt are two key metals used by modern civilization in a host of applications. Cobalt, in particular, is categorized as a "strategic metal" in view of its great importance to the development of "green technologies" (such as energy storage in batteries used, for example in new generation electric and hybrid vehicles) and also because of the fact that much of its production is concentrated in parts of the world perceived to be potentially unstable. Most of the nickel and cobalt produced from mining primary ores originates from reduced (sulfidic) minerals, though the bulk of accessible global reserves of nickel (in particular) is contained in oxidized ores, most notably laterites, which are widely distributed throughout (mostly) tropical regions. Although technologies exist for extracting valuable metals from lateritic ores, these mostly operate at high temperatures and pressures and are therefore highly energy consuming and have large carbon footprints. Recently, a microbiological mechanism for extracting nickel and cobalt from limonitic laterites, which operates at atmospheric pressure and ambient (30 - 40C) temperatures has been described and demonstrated at laboratory scale. Biomining is often considered to be a "green" approach for obtaining metals, and has been used for over 50 years to obtain copper. The novel technology developed at Bangor University in conjunction with the mining industry has greatly extended the range of metal ores that can be bioprocessed. Limonitic ores from mines located in different parts of the world (including Asia, Africa and South America) have been trialed in the frame of a current NERC-sponsored project (which focuses specifically on cobalt) and all have been shown to be amenable to bioprocessing using this new approach (referred to as "reductive mineral dissolution"). Among these was material from a new mining enterprise in Brazil, located in Piaui state, the owners of which are active members of the NERC project consortium. The Piaui mine has not yet become a full-scale operation, and the bioprocessing option has several perceived major advantages of what is currently envisaged as the operating protocol (leaching with concentrated sulfuric acid in heaps). These include: (i) eliminating the need to transport in large amounts of concentrated acid to the remote mine site (both costly and hazardous); (ii) removing the need to purchase an acid-generating plant for long-term sulfuric acid generation (the cost of which is equivalent to ~25% of the total capital cost of the mine); (iii) the potential to enhance both rates and extents of metal extraction from the ore. The original reductive mineral dissolution protocol has been fine-tuned in the current NERC project to minimize or eliminate the need to use acid to neutralize the alkalinity generated when minerals in the limonite ores dissolve. Instead the acid is generated in situ from elemental sulfur by specialized bacteria. There is a perfectly timed opportunity to scale up the reductive mineral dissolution approach from laboratory to pilot scale, and this is greatly facilitated by the fact that large columns required for this are already in place at the Piaui mine site. The project will involve firstly producing sulfur colonized by the specialized bacteria used in the process, shipping this from the UK to the mine at Piaui where it will be combined with the ore (and additional sulfur) and packed into a large (4 m high) column. This, and a control (acid-leached) column will be operated in re-circulation flow mode for 6-7 months, by which time most of the metals will have been extracted. The columns will then be dis-assembled and, if results are as anticipated, used for the next stage in the process (heap leaching; beyond the scope of the current project). This demonstration plant will provide essential data that will help promote the application of this novel biomining approach to laterite mines throughout the world.