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

Lead Research Organisation: University of Nottingham
Department Name: Sch of Chemistry


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.

Planned Impact

This CDT will deliver impact aligned to the following agendas:

A2P will provide over 60 PhD graduates with the skill sets required to deliver innovative sustainable products and processes into the UK chemicals manufacturing industry. A2P will inspire and develop leaders who will:
- understand the needs of industrial end-users;
- embed sustainability across a range of sectors; and
- catalyse the transition to a more productive and resilient UK economy.

A2P will promote a step change towards a circular economy that embraces resilience and efficiency in terms of atoms and energy. The benefits of adopting more sustainable design principles and smarter production are clear. For example, the global production of active pharmaceutical ingredients (APIs) has been estimated at 65,000-100,000 tonnes per annum. The scale of associated waste is > 10 million tonnes per annum with a disposal cost of more than £15 billion. Consequently, even a modest efficiency increase by applying new, more sustainable chemical processes would deliver substantial economic savings and environmental wins. A2P will seek and deliver systematic gains across all sectors of the chemicals manufacturing industry. Our goals of providing cross-scale training in chemical sciences with economic and life- cycle awareness will drive uptake of sustainable best practice in UK industry, leading to improved economic competitiveness.

This CDT will deliver significant new knowledge in the development of more sustainable processes and products. It will integrate the philosophy of sustainability with catalysis, synthetic methodology, process engineering, and scale-up. Critical concepts such as energy/resource efficiency, life cycle analysis, recycling, and sustainability metrics will become seamlessly joined to what is considered a 'normal' approach to new molecular products. This knowledge and experience will be shared through publications, conferences and other engagement activities. A2P partners will provide efficient routes to market ensuring the efficient translation and transferal of new technologies is realised, ensuring impact is achieved.

The chemistry-using industries manufacture a rich portfolio of products that are critical in maintaining a high quality of life in the UK. A2P will provide highly trained people and new knowledge to develop smarter, better products, whilst increasing the efficiency and sustainability of chemicals manufacture.
To amplify the impacts of our CDT, effective public engagement and technology transfer will become crucially important. As a general comment, 'sustainability' styled research is often regarded in a positive light by society, however, the science that underpins its effective implementation is often poorly appreciated. The University of Nottingham has developed an effective communication portfolio (with dedicated outreach staff) to tackle this issue. In addition to more traditional routes of scientific communication and dissemination, A2P will develop a portfolio of engagement and outreach activities including blogs, webpages, public outreach events, and contribution of material to our award-winning YouTube channel,

A2P will build on our successful Sustainable Chemicals and Processes Industry Forum (SCIF), which will provide entry to networks with a wide range of chemical science end-users (spanning multinationals through to speciality SMEs), policy makers and regulators. We will share new scientific developments and best practice with leaders in these areas, to help realise the full impact of our CDT. Annual showcase events will provide a forum where knowledge may be disseminated to partners, we will broaden these events to include participants from thematically linked CDTs from across the UK, we will build on our track record of delivering hi-impact inter-CDT events with complementary centres hosted by the Universities of Bath and Bristol.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S022236/1 01/10/2019 31/03/2028
2763648 Studentship EP/S022236/1 01/10/2022 30/09/2026 Christine Paul