Biogeochemistry, Bioextraction and Biorecovery of Rare Earth Elements

稀土元素(REE)是一组17种金属(La-Lu、Y、Sc)，已被发现具有许多有用的化学和物理性质，并已被一系列工业利用。稀土在生产日常用品(计算机、智能手机等)、陶瓷、合金、磁铁、LCD屏幕，甚至用于医学成像的造影剂(如核磁共振扫描期间)中都有关键用途。虽然稀土在世界各地的矿石中都有发现，但目前从矿石中提取和分离稀土的方法只适用于相对于岩石含量而言含有大量稀土的矿石(“高品位矿石”)，而世界各地的大多数稀土矿床含有低稀土和高岩石(“低品位矿石”)。如果没有有效的低品位矿石提取方法，全球稀土供应链依赖于中国等少数几个拥有高品位矿藏的国家。这意味着，英国和欧盟每年都在以高昂的成本(稀土价格每天都在上涨)从中国手中进口大量稀土，而且不仅需要相关的运输成本，还会对环境造成影响，并产生较高的“碳足迹”。生物ORE是由普利茅斯大学、曼彻斯特大学、伯明翰大学以及英国地质调查局牵头的一个多学科项目，最终目标是探索从英国和欧盟发现的低品位矿石中提取稀土的方法。为了尝试并为我们提供这些重要金属的安全供应，普利茅斯大学开发了一种生物提取程序，在这种程序中，低品位的稀土矿石可以在严格控制的反应堆中被“吃岩石”的细菌分解，留下少量的岩石废物(可以回收利用)和含有稀土混合物的溶液。这一程序相对便宜，不使用任何有害化学品或产品任何污染物-如果在此过程中细菌产生的二氧化碳被捕获回收，而不释放到环境中。普利茅斯大学和伯明翰大学共同开发了一种进一步的生物回收工艺，在该工艺中，可以选择性地从生物提取产生的混合物中回收稀土--也就是说，该工艺将金属从溶液中分离出来。这是使用含有嵌入在一种塑料中的细菌的受控反应堆来实现的，稀土溶液流过塑料。细菌在新陈代谢过程中会产生大量的磷酸盐，这些磷酸盐与稀土元素发生反应，产生稀土磷酸盐生物矿物质，在塑料基质中的细胞上形成晶体。通过使用一系列不同的细菌和不同的条件，我们可以从混合物中选择性地生物回收稀土。这些生物矿物既可以直接供需要它们的行业使用，也可以进行化学或生物深加工，以满足行业需求。BioORE将把一系列国际行业聚集在一起，并将与它们合作开发、优化和扩大这两项生物技术，目标是开发一种从低品位矿石中提取稀土的有效方法。生物技术的使用不仅是一种快速和选择性地分离稀土的手段；它也是一种“绿色”技术，不会产生与目前的稀土分离方法相关的有害污染物。这些技术将能够从世界各地发现的低品位矿石中生产清洁、绿色的稀土元素，允许使用这些矿石的国家进行当地生产，并减少与全球运输相关的二氧化碳负担。

The rare earth elements (REEs) are a group of 17 metals (La-Lu, Y, Sc) that have been discovered to have a number of useful chemical and physical properties and have been harnessed by a range of industries. REEs have critical uses in production of electronic components used in every-day items (computers, smartphones etc), ceramics, alloys, magnets, LCD screens and even in contrast agents used in medical imaging, such as during MRI scans. Whilst REEs are found in ores all over the world, current methods for extraction and separation of REEs from ores only work efficiently with ores containing large amounts of REEs relative to the amount of rock present ("high-grade ores"), whereas the majority of REE ore deposits worldwide contain low amounts of REEs and high amounts of rock ("low-grade ores"). Without effective extraction methods for low-grade ores, the global REE supply chain is dependent upon the few countries that have high-grade ore deposits, such as China. This means that the UK and EU are importing enormous amounts of these metals from China each year, at great cost (REE prices increase daily) and with not just associated shipping costs but an environmental impact of that transit and a high "carbon footprint".BioORE is a multi-disciplinary project lead by the University of Plymouth alongside the Universities of Manchester and Birmingham and the British Geological Survey, with the ultimate goal of exploring methods for extraction of REEs from low-grade ores found in the UK and EU, in order to try and provide us with a secure supply of these vital metals.The University of Plymouth has developed a bioextraction procedure in which low-grade REE ores can be broken down by 'rock eating' bacteria in carefully controlled reactors, leaving behind a small amount of rock waste (that could be recycled) and a solution containing a mixture of REEs. This procedure is relatively inexpensive and does not use any harmful chemicals or product any pollutants -event the CO2 produced by the bacteria during the process is trapped for recycling and not released into the environment. A further biorecovery process has been co-developed by the Universities of Plymouth and Birmingham in which REEs can be recovered back out of the mixture produced in bioextraction in a selective manner - that is to say that the process separates out the metals from the solution. This is achieved using controlled reactors containing bacteria embedded in a type of plastic, over which the REE solution flows. The bacteria produce large amounts of phosphate during their metabolism, which reacts with REEs producing REE phosphate biominerals, which form crystals all over the cells in the plastic matrix. By using a range of different bacteria and different conditions, we can selectively biorecovery REEs from mixtures. The biominerals can either be used directly by industries that need them or can be further processed either chemically or biologically to meet industry's needs.BioORE will bring together a range of international industries and will work with them to develop, optimise and scale-up these two biotechnologies with the goal of developing an effective method for REE extraction from low-grade ores. Use of a biotechnology is not only a means to fast and selective REE separation; it is also a 'green' technology, producing none of the harmful pollutants associated with current REE separation methods. These technologies will enable clean, 'green' REE production from low-grade ores found worldwide, permitting local production in countries that use them and reducing the CO2-burden associated to global transport.