PETAL: Developing a plant-based platinum group metal recovery system

铂族金属，包括钯，是相对罕见的，并且在纳米级金属颗粒的发展中越来越重要（人的头发大约有8万到10万纳米宽）。金属纳米粒子（NP）被用作化学合成和生物医学科学的催化剂，包括生物传感系统、药物输送和癌症治疗。钯是一种重要的工业金属，应用于催化转化器、化学加工、电导体制造和制药。然而，金属是有限的资源，计算表明，以目前的消费速度，以钯为例，全球储量可能只够用100年。或许更令人担忧的是，这些金属很容易受到地缘政治控制的供应限制的影响；其中99%以上在南非、俄罗斯、赞比亚和美国。由于英国或欧洲没有可观的储量，在许多技术应用中也没有合适的替代品，因此英国现有供应的回收利用至关重要。但是这些储备到哪里去了呢？从历史上看，PGMs作为稀释的金属废物被丢弃在路边，或者作为电子废物被埋在垃圾填埋场。由此产生的混合金属污染净化成本高昂，几乎没有可行的技术能够分离单个金属，目前也没有经济上可行、环境上可持续的方法。植物有一种精妙的能力，可以选择性地从环境中吸收和储存金属，也可以用来从周围环境中清除金属，这一过程被称为植物采矿。虽然利用植物从环境中提取金属并不新鲜，但种植、收获和运输富含金属的植物生物量的费用，以及冶炼贱金属的费用，一直阻碍着这项技术的发展。在约克大学，我们已经证明，在低能量微波步骤之后，植物衍生的含钯np的生物质可以直接用作有效的催化剂。这种用途增加了植物修复过程的价值。该研究的目的是开发能够从土壤中提取Pd的植物，未来的目标是将这项技术转化为可用于从废物中回收pgm的植物物种。我们的工业合作伙伴约克废物有限公司，将提供清扫从道路边缘来测试我们的技术。本研究的主要目标有四个：1。评估产生氰化物的植物和细菌溶解土壤中相对惰性金属的能力，使它们能够被植物吸收。为了做到这一点，我们将使用盆栽实验，在原始土壤中种植拟南芥，并在有Pd和没有细菌的情况下种植，或者间作氰化的日本莲花。2. azurin是一种小的（约14kDa）细菌，含铜蛋白，具有深蓝色的特征。azurin-Pd是一种结合Pd和Pt的突变体，我们将在拟南芥的茎组织中产生表达azurin-Pd的品系。pd特异性肽Q7和Pd4在植物组织中播种NPs研究人员设计了肽（小蛋白质），当与钯溶液混合时，产生NPs。该项目将把制造这些肽的基因转移到植物中，以增加植物组织中钯NPs的数量、大小和形状。富Pd热解生物质催化关键反应的能力测试我们已经证明，在微波低能热解之后，植物源的含Au和Pd np的生物质可以直接用作有效的催化剂。这种用途增加了植物修复过程的价值。

Platinum group metals, including palladium, are relatively rare and increasingly important in developing technologies as nano-sized metal particles (a human hair is approximately 80,000- 100,000 nanometers wide). Metal nanoparticles (NP) are used as catalysts in chemical synthesis, and in biomedical sciences including biosensing systems, drug delivery and cancer treatments. Palladium is an industrially important metal with applications in catalytic converters, chemical processing, the manufacturing of electrical conductors and pharmaceuticals. However, metals are finite resources, and calculations suggest that, at current consumption rates, global reserves of Pd for example, will last perhaps 100 years. Of perhaps even more concern is that these metals are vulnerable to geopolitically-controlled supply restrictions; with over 99% in South Africa, Russia, Zambia, and the United States. With no appreciable reserves in the UK or Europe, and no suitable substitutes in many technological applications, it is critical that exiting supplies in the UK are recycled. But where have these reserves gone? Historically, PGMs have been discarded as diluted metal waste alongside road verges, or buried in landfill as electronics waste. The resulting mixed-metal pollution is expensive to decontaminate, with few viable technologies able to tease-apart the individual metals, and no financially viable, environmentally sustainable methodologies currently available.Plants have an exquisite ability to selectively take-up and store metals from the environment, and can be used to scavenge metals from their surroundings, a process called phytomining. While using plants to extract metals from the environment is not new, the costs of growing, harvesting and transporting metal-rich plant biomass, in addition to the cost of smelting to the base metal, have been prohibitive to the development of this technology. At the University of York, we have demonstrated that, following a low-energy microwave step, plant-derived palladium NP-containing biomass can be used directly as effective catalysts. This use adds value to the phytoremediation process.The purpose of the research is to develop plants that can extract Pd from soils, with future aims to translate this technology into plant species that can be used to recover PGMs from wastes. Our industrial partners Yorkwaste Ltd, will supply sweepings from road verges to test our technology. There are four main objectives of the research:1. To assess the ability of cyanide-producing plants and bacteria to solubilise the relatively inert metals from the soils so that they can be taken up by plants. To do this, we will use pot-based experiments with Arabidopsis plants grown in pristine soil dosed with Pd and with and without the bacteria, or intercropped with cyanogenic Lotus japonicus. 2. Evaluate the efficacy of Arabidopsis plants expressing azurin-PdAzurin is a small (~14kDa) bacterial, copper-containing protein with a characteristic deep-blue colour. A mutant of azurin (azurin-Pd) has been identified that binds Pd and Pt. We will produce Arabidopsis lines expressing azurin-Pd in their shoot tissues.3. Quantification of Pd-specific peptides Q7 and Pd4 to seed palladium NPs in plant aerial tissuesResearchers have designed peptides (small proteins) that when mixed with solutions of palladium seed the production of NPs. This project will transfer the genes that make these peptides into plants to increase the number, size and shape of palladium NPs in the plant tissues.4. Testing ability of Pd-rich pyrolysed biomass to catalyse key reactionsWe have demonstrated that, following a low-energy pyrolysis using microwaves, plant-derived Au- and Pd NP-containing biomass can be used directly as effective catalysts. This use adds value to the phytoremediation process.