Bio-electrochemical Recovery of Platinum Group Metals from Spent Car Catalysts by Cupriavidus metallidurans.

铂族金属（PGMs），如铂、钯和铑，是汽车、电子和医疗保健应用中必不可少的关键原材料。然而，铂族金属面临着稀缺性、地缘政治供应风险以及采矿和加工对环境的高影响。随着需求的不断增长，从废旧汽车催化剂等二手资源中回收铂族金属对于供应的可持续性至关重要。废旧汽车催化转化器含有比原矿更高浓度的铂族金属，是一个重要的城市矿山。全球回收率仍然很低，有很大的改善潜力。2020年，只有15-20%的铂和钯以及10%的铑被回收利用。PGM回收提供了经济和战略价值，减少了初级采矿对环境的影响，并符合循环经济原则。然而，传统的PGM回收方法存在缺陷。火法冶金涉及高能耗和高排放。湿法冶金使用腐蚀性化学品并产生废物。我们需要更可持续的技术。生物电化学系统（BES）如微生物燃料电池（MFC）可以通过具有较低能量和化学投入优势的微生物金属还原机制回收PGMs。金属铜杆菌是一种耐金属细菌，它能将金属金属金属金属化成金属形式。虽然有研究探索了利用C. metallidurans回收金属，但有限的研究评估了其在mfc中的潜力。工程生物学方法，如金属结合蛋白在细菌表面的过表达，可以进一步提高PGM的生物吸附和回收效率。该项目将研究野生型和转基因C. metallidurans在mfc中的使用，以开发从废汽车催化剂中回收PGM的可持续工艺。评估生物催化和电化学性能以及生命周期影响可以证明该方法的技术可行性、经济可行性和环境效益优于传统技术。该项目涉及设计和优化一种微生物燃料电池（MFC），利用金属还原细菌Cupriavidus metallidurans从废催化剂中回收PGMs。在选择合适的阳极电极材料（如碳布）和阳离子交换膜（如Nafion）以获得最佳的电化学性能后，通过跟踪生长动力学和测量PGM浓度，分析野生型C. metallidurans在废催化剂的间歇培养中对PGM的耐受性和回收率。然后，在不同的pH值、温度、催化剂负载和电极电位条件下，在MFC原型中测试应变，以找到最大发电量和阴极上PGM回收率的最佳水平。详细的电化学分析将阐明其机理。为了进一步提高PGM的生物吸附能力，将对C. metallidurans进行基因工程改造，使其过表达通过组学方法鉴定的内源性金属结合蛋白或金属硫蛋白等异源蛋白。在MFC的不同操作条件下，优化出最佳应变。最后，将使用生命周期评估方法，通过排放、资源消耗和废物产生等影响类别，对基于mfc的技术的可持续性进行评估，以对比传统的火法冶金和湿法冶金回收PGM。

Platinum group metals (PGMs) like platinum, palladium, and rhodium are critical raw materials essential for automotive, electronics, and healthcare applications. However, PGMs face scarcity, geopolitical supply risks, and high environmental impacts from mining and processing. With rising demand, recovering PGMs from secondary sources like spent automotive catalysts is crucial for supply sustainability. Spent car catalytic converters contain PGMs at higher concentrations than primary ores and represent a critical urban mine. Global recycling rates are still low, with significant potential for improvement. In 2020, only 15-20% of platinum and palladium and 10% of rhodium were recycled. PGM recycling provides economic and strategic value, reduces the environmental impacts of primary mining, and aligns with circular economy principles. However, conventional PGM recovery methods have drawbacks. Pyrometallurgy involves high energy use and emissions. Hydrometallurgy utilizes corrosive chemicals and generates waste. There is a need for more sustainable techniques. Bio-electrochemical systems (BES) like microbial fuel cells (MFC) can potentially recover PGMs through microbial metal reduction mechanisms with lower energy and chemical input advantages. Cupriavidus metallidurans, a metal-resistant bacterium, demonstrates biomineralization of PGMs into their metallic forms. While studies have explored metal recovery using C. metallidurans, limited research has evaluated its potential in MFCs. Engineering biology approaches like overexpression of metal binding proteins on bacterial surfaces could further enhance PGM biosorption and recovery efficiency. This project will investigate the use of wild-type and genetically modified C. metallidurans in MFCs to develop a sustainable process for PGM recovery from spent automotive catalysts. Evaluating the biocatalytic and electrochemical performance along with life cycle impacts can demonstrate the method's technical feasibility, economic viability, and environmental benefits over conventional techniques.This project involves designing and optimizing a microbial fuel cell (MFC) to recover PGMs from spent catalysts using the metal-reducing bacterium Cupriavidus metallidurans. After selecting suitable anodic electrode materials like carbon cloth and cation exchange membranes like Nafion for optimal electrochemical performance, the wild-type C. metallidurans will be analyzed for PGM tolerance and recovery in batch cultures with spent catalysts by tracking growth kinetics and measuring PGM concentrations. The strain will then be tested in an MFC prototype under different conditions of pH, temperature, catalyst loading, and electrode potentials to find optimal levels that maximize electricity generation along with PGM recovery on the cathode. Detailed electrochemical analysis will elucidate the mechanisms. To further improve PGM biosorption, C. metallidurans will be genetically engineered to overexpress endogenous metal binding proteins identified through omics approaches or heterologous proteins like metallothioneins. The best-performing strain will be optimized under different operating conditions in the MFC. Finally, the sustainability of the MFC-based technique will be evaluated against conventional pyrometallurgy and hydrometallurgy for PGM recovery using life cycle assessment across impact categories like emissions, resource consumption, and waste generation.