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

铂族金属，包括钯，相对稀有，在开发纳米金属颗粒(人的头发大约有80,000-100,000纳米宽)的技术中越来越重要。金属纳米颗粒(NP)在化学合成和生物医学科学中被用作催化剂，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，在催化转化器、化学加工、电导体制造和制药方面都有应用。然而，金属是有限的资源，计算表明，以目前的消耗速度计算，全球钯的储量可能会持续100年。也许更令人担忧的是，这些金属容易受到地缘政治控制的供应限制；南非、俄罗斯、赞比亚和美国的供应限制超过99%。由于英国或欧洲没有可察觉的储量，在许多技术应用中也没有合适的替代品，关键是英国现有的供应要回收利用。但这些储备到哪里去了呢？从历史上看，PGM曾作为稀释的金属废料被丢弃在路边，或者作为电子垃圾被掩埋在垃圾填埋场。由此产生的混合金属污染的净化成本很高，几乎没有可行的技术能够梳理出单个金属，目前还没有经济上可行的、环境可持续的方法。植物具有从环境中选择性地吸收和储存金属的精妙能力，可以用于从周围环境中清除金属，这一过程被称为植物采矿。虽然使用植物从环境中提取金属并不是什么新鲜事，但种植、收获和运输富含金属的植物生物质的成本，以及冶炼贱金属的成本，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，从植物中提取的含钯NP的生物质可以直接用作有效的催化剂。这一用途增加了植物修复过程的价值。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PGMS的植物种类。我们的工业合作伙伴约克垃圾有限公司将提供道路边缘的清扫设备，以测试我们的技术。这项研究有四个主要目标：1.评估产生氰化物的植物和细菌从土壤中溶解相对惰性金属的能力，以便它们可以被植物吸收。为了做到这一点，我们将使用盆栽实验，种植在原始土壤中的拟南芥植株，在含有和不含有细菌的情况下，或者与生氰莲花间作。2.评价表达天青素的拟南芥植株的有效性-天青素是一种小的(~14 kDa)细菌蛋白，含铜，具有深蓝色的特征。天青素的一个突变体(天青素-钯)已被鉴定为与钯和铂结合。我们将获得在其地上部组织中表达天青素-PD的拟南芥品系。植物气生组织中钯专一性多肽Q7和Pd4的定量研究人员设计了一种多肽(小蛋白)，当它们与钯种子的溶液混合时，就会产生NPs。该项目将把制造这些多肽的基因转移到植物中，以增加植物组织中钯纳米粒子的数量、大小和形状。富Pd热解生物质催化关键反应能力的测试我们已经证明，经过微波低能热解后，植物来源的含Au和Pd NP的生物质可以直接用作有效的催化剂。这种使用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.