Microbially mediated functionalised magnetic nanoparticles from acid mine drainage

酸性矿井水污染是全球危害仅次于气候变化的巨大生态问题。AMD是一种酸性溶液，含有高浓度的有毒金属，是采矿和其他工业过程的直接结果。将旨在清理污染区域的AMD修复策略与回收具有高经济价值的有价金属相结合，具有相当大的机会。AMD通常含有一系列金属（Fe, Co, Zn， Cu等），这些金属浓度低，但仍是未开发的资源，特别是当考虑到总量时。从AMD中回收特定金属是一项重大挑战，目前缺乏技术解决方案。然而，一个主要的未开发的机会在于高浓度的铁，可以用来通过微生物过程生产磁性纳米颗粒。这个提议将开发一条路线，通过它可以大规模生产功能化的、高纯度的、生物磁性纳米颗粒。纳米颗粒的全球市场正在迅速扩大，价值已达250亿美元，其中磁性纳米颗粒是一种特别重要的类型，可用于饮用水的修复、农业、医疗或催化等领域。然而，目前生产磁性纳米颗粒的方法依赖于高成本，不可持续的线性多步骤过程。相比之下，细菌可以在环境条件下生产具有可调谐特性的磁性纳米颗粒。通过将细菌作为“迷你工厂”，我们可以开发一种循环方法，在这种方法中，像AMD这样的废物可以作为原料来生产一种备受追捧的商品。该项目将利用两种能够代谢铁的细菌，这两种细菌在环境中无处不在。我们将使用趋磁细菌，通过生物控制矿化产生细胞内磁性纳米颗粒。这些细菌利用磁性颗粒进行导航，由于存在负责吸收铁的特定通道，往往会产生纯度极高的磁性纳米颗粒。通过这种途径产生的磁性纳米颗粒被有机涂层功能化，从而增强了它们的反应性。这种方法的一个缺点是产生的纳米颗粒浓度相对较低。因此，我们也将利用铁还原细菌，通过生物诱导矿化产生磁性纳米颗粒的细胞外颗粒。这些纳米颗粒的纯度往往低于趋磁细菌，但可以在更大的规模上生产。通过开发两种生产AMD磁性纳米颗粒的方法，该项目提供了独特的机会来解决缩放和纯度问题，同时提供符合循环经济目标的高价值产品。

Pollution caused by acid mine drainage (AMD) is an enormous ecological problem which is second only to climate change in terms of global risk. AMD is an acidic solution containing high concentrations of toxic metals as a direct result of mining and other industrial processes. There is a considerable opportunity to combine remediation strategies of AMD, aimed at cleaning up contaminated areas, with the recovery of valuable metals with high economic value. AMD typically contains a range of metals (Fe, Co, Zn, Cu etc.) that are present at low concentrations but remain an untapped resource, especially when the total volumes are taken into consideration. Recovering specific metals from AMD poses a significant challenge, of which technological solutions are currently deficient. However, a major untapped opportunity lies in the high concentration of iron which could be used to produce magnetic nanoparticles through microbiological processes. This proposal will develop a route through which functionalised, high purity, biogenic magnetic nanoparticles can be produced at scale. The global market for nanoparticles is expanding rapidly and is already worth $25 billion, with magnetic nanoparticles an especially important type that can be used for remediation of drinking water, in agriculture, medical therapies, or catalysis amongst others. Nevertheless, current approaches to producing magnetic nanoparticles rely on high cost, unsustainable linear multi-step processes. In contrast, bacteria can be exploited to produce magnetic nanoparticles with tuneable properties under ambient conditions. By turning to bacteria as "mini-factories" we can develop a circular approach where waste, such as AMD, can be used as a feed stock to produce a highly sought after commodity.This project will take advantage of two types of bacteria which are able to metabolise iron and are ubiquitous in the environment. We will use magnetotactic bacteria, which produce intracellular grains of magnetic nanoparticles via biologically controlled mineralisation. These bacteria use the magnetic grains for navigation and due to the presence of specific channels responsible for the uptake of iron, tend to produce magnetic nanoparticles with extremely high purity. The magnetic nanoparticles produced via this pathway are functionalised with organic coatings that enhance their reactive properties. One draw back of this method though is the relatively low concentration of nanoparticles which are produced. Consequently, we will also exploit iron reducing bacteria, which produce extracellular grains of magnetic nanoparticles via biologically induced mineralisation. These nanoparticles tend to exhibit lower purity than from magnetotactic bacteria but can be produced at much larger scale. By developing two methods of producing magnetic nanoparticles from AMD, this project offers unique opportunities to tackle both scaling and purity issues, whilst simultaneously delivering a high value product which meets the goals of a circular economy.