Beyond Biorecovery: environmental win-win by biorefining of metallic wastes into new functional materials

过去30年关于从废物中生物回收金属的研究很少注意到当代对以下方面的强烈需求：(1)保护日益减少的重要资源(例如铂族金属(PGM)，最近还有稀土元素(REE)、贱金属和铀)和(2)以无污染、低能耗的方式提取和提炼这些资源的明确需要。另一方面，21世纪的技术越来越依赖纳米材料，因为这些材料具有块状材料所没有的新特性。细菌可以制造纳米颗粒，自下而上，一个原子一个原子地制造，通过酶合成和生物支架提供的精细控制，这是化学无法模仿的。生物纳米粒子在绿色化学、低碳能源、环境保护以及潜在的光子应用(如纳米金)方面都有广泛的应用。细菌可以以可伸缩和廉价的方式生长，即在生产简便性、可伸缩性和价格方面进行逐步改变。最近的研究表明，细菌能够从初级和次级废物中制造出这些纳米材料，在某些情况下，会产生一种金属混合物，这种混合物可以显示出比“纯”纳米颗粒更好的活性。结构双金属的制造很难通过化学手段实现。对于一些金属，如稀土和铀，他们从废料(U)和废料(REE)中生物回收成大量结晶矿物，可以制造出浓缩的固体，然后输送到进一步的商业精炼中，以制造新的磁体(REE)或核燃料(U)。生物软化这些固体的能力超出了活细胞的能力，尽管生物生成的纳米磷酸铀可以用来“吸除”贱金属(和放射性核素)，其容量比商业离子交换器大几个数量级。这个项目将在几个复杂程度、成熟度和风险水平上运行。贱金属采矿废物(如铜、镍)将被生物提炼成浓缩的淤泥，以便进行化学后处理，或者用于评估制造贱金属--生物阳极产品的范围。铀矿废料将被生物提炼成磷酸盐矿物，用于商业制造核燃料。贵金属废料将被转化为生物材料，用于催化和能源应用。在所有这些例子中，环境都不会受到原生源污染和从原生原油加工的高能源需求的双重影响。金属废料存在问题，因为它们需要强酸来溶解。方法将包括使用嗜酸性细菌，使用碱化酶或使用细菌首先制造化学催化剂(在良好的条件下)，然后可以将废物渗滤液中感兴趣的目标金属转化为新的纳米材料(一种混合的生物/非生物系统，已经得到证实)。生物、化学、矿物学和物理学之间的接口，以其独特的“生化巢”中的纳米颗粒为例，将受到特别关注，因为这是将有重大发现的地方；因此，尖端技术(例如，具有纳米级元素图谱的X射线显微镜)将被应用，以将结构与功能联系起来，并验证上游废物修正、掺杂或‘混合’对此的贡献，以及已证明可提高生物纳米粒子效率的新材料加工。生物提炼的二次废物将包括磁铁废料(REE)、废汽车催化剂、道路粉尘(贵金属、Fe、Ce)和电子废料(铜、贵金属)。它们的复杂性和耐火性导致了比矿山废物更高的“风险”，但“回报”弥补了这一点，因为体积往往更小，制造/引导工程纳米材料的“掺杂”或“转向”的可能性也相应地更高。B3项目将对选定为特别重点的系统进行嵌入式重要(约15%)生命周期分析评估，并在结合工业平台进行范围研究后进行最终用户试验。

The last 30 years' research on metal biorecovery from wastes paid scant attention to the strong CONTEMPORARY demands for (i) conservation of dwindling vital resources (e.g platinum group metals (PGM) and, recently rare earth elements, (REE), base metals and uranium) and (ii) the unequivocal need to extract and refine them in a non-polluting, low-energy way. On the other hand, 21stC technologies increasingly rely on nanomaterials as these have novel properties not seen in bulk materials. Bacteria can fabricate nanoparticles, bottom up, atom by atom, with exquisite fine control offered by enzymatic synthesis and bio-scaffolding that chemistry cannot emulate. Bio-nanoparticles have proven applications in green chemistry, low carbon energy, environmental protection and in, potentially, photonic applications (e.g. nano-Au). Bacteria can be grown scalably and cheaply, i.e. step changes in facile production, scalability and price. Recent work showed the ability of bacteria to make these nanomaterials from primary and secondary wastes, yielding, in some cases, a metallic mixture which can show better activity than 'pure' nanoparticles. Fabrication of structured bimetallics can be hard to achieve by chemical means. For some metals like REEs and uranium their biorecovery from wastes (U) and scraps (REE) into bulk crystalline minerals can make 'enriched' solids for delivery into further commercial refining to make new magnets (REEs) or nuclear fuel (U). Biofabricating these solids is beyond the ability of living cells although biogenic nano-uranium phosphate can be used to 'hoover' base metals (and radionuclides) with a capacity several orders of magnitude greater than commercial ion exchangers.This project will operate at several levels of complexity, maturity and risk. Base metal mining wastes (e.g. Cu, Ni) will be biorefined into concentrated sludges for chemical reprocessing or alternatively for evaluating the scope to make base metal-bionanoproducts. U-mining waste will be biorefined into phosphate minerals for commercial fabrication into nuclear fuels. Precious metal wastes will be converted into bionanomaterials for catalysis and energy applications. In all of these examples the environment will be spared the dual impact of both the primary source pollution and the high energy demand of processing from primary 'crude'.Metallic scraps present problems as they require strong acids for dissolution. Approaches will include the use of acidophilic bacteria, use of alkalinizing enzymes or using bacteria to first make a chemical catalyst (under benign conditions) which can then convert the target metal of interest from the waste leachate into new nanomaterials (a hybrid living/nonliving system, already proven). The interface between biology, chemistry, mineralogy and physics, exemplified by nanoparticles in their unique 'biochemical nest', will receive special attention as this is where major discoveries are to be made; hence cutting edge technologies (e.g. X ray microscopy with nanoscale elemental mapping) will be applied in order to relate structure to function, and validate the contribution of upstream waste amendment, doping or 'blending' to these, as well as novel materials processing already shown to increase bio-nanoparticle efficacy.Secondary wastes to be 'scoped' for biorefining will include magnet scraps (REEs), spent automotive catalysts, road dusts (precious metals, Fe,Ce) and electronic scrap (Cu, precious metals). Their complexity and refractory nature makes for a higher 'risk' than with mine wastes but the 'payoff' compensates, in that the volumes tend to be lower, and the potential for 'doping' or 'steering' to fabricate/steer engineered nanomaterials is correspondingly higher. The B3 project will have an embedded significant (~15%) Life Cycle Analysis assessment of the systems chosen for special focus, and end-user trialing following scoping studies in conjunction with an industrial platform.