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Innovative Method for Sustainable Metal Separation Enhances Battery Technology
Researchers at the University of Pennsylvania have developed a new technique aimed at improving sustainable practices in the extraction of essential metals necessary for battery technologies. This research signifies a substantial step toward deriving value from materials traditionally seen as waste.
The book “Cobalt Red: How the Blood of Congo Powers Our Lives” by Siddarth Kara sheds light on the troublesome sourcing of cobalt, a key element in lithium-ion batteries that fuel a wide array of modern technologies, from smartphones to electric cars.
Eric Schelter, the Hirschmann-Makineni Professor of Chemistry at Penn, emphasizes the importance of understanding how the materials used in these batteries are sourced. He points out ethical and environmental concerns surrounding cobalt mining, particularly in the Democratic Republic of Congo, which accounts for approximately 70% of global cobalt supply. This mining often leads to severe environmental damage and poses health risks to local workers due to unsafe working conditions. As the demand for batteries surges, a potential cobalt shortage could further strain the supply chain.
In response, Schelter’s lab is investigating methods for the efficient separation of critical battery metals, including nickel and cobalt. Their recent publication in the journal Chem highlights a novel “easier, more sustainable, and cost-effective” technique to extract these metals from waste materials.
“Our chemistry is appealing because it is straightforward, effective, and addresses the complex challenge of separating nickel and cobalt,” Schelter explains. This new approach not only has the potential to enhance cobalt purification efforts with minimal environmental impact but also adds value to discarded batteries through efficient metal recovery.
The right ingredients for selective separation
Traditionally, cobalt is obtained as a byproduct of nickel mining through energy-intensive methods like acid leaching and solvent extraction, which can generate hazardous waste. The strategy developed by Schelter and his collaborators uses a chemical separation method that exploits the differences in charge density and bonding between two molecular complexes: cobalt (III) hexammine and nickel (II) hexammine.
“The key to successful separation lies in identifying the unique properties of the materials you wish to differentiate,” Schelter notes. They found that ammonia, a simple and inexpensive reagent, exhibits different binding characteristics with nickel and cobalt hexammine complexes.
By incorporating a negatively charged molecule such as carbonate, the researchers formulated a solid structure that allows the cobalt complex to precipitate out from the solution while leaving the nickel complex dissolved. Their findings indicate that the carbonate anion selectively interacts with cobalt, forming stable hydrogen bonds and facilitating its separation. Post-precipitation, the team filters, washes, and dries the cobalt-rich solid, allowing the remaining nickel solution to be further processed.
“This method results in exceptional purity levels of 99.4% for cobalt and over 99% for nickel, while avoiding the hazardous solvents and acids prevalent in earlier separation techniques,” says Boyang (Bobby) Zhang, a graduate student in Penn’s School of Arts & Sciences and a fellow at the Vagelos Institute for Energy Science and Technology. “It is a straightforward and scalable method that promises significant environmental and economic benefits.”
Techno-economic and life cycle analyses
The research team, led by Marta Guron, conducted comprehensive techno-economic analysis and life-cycle assessments to evaluate the practicality of their proposed separation method. Preliminary findings suggest that the production cost for purified cobalt is approximately $1.05 per gram, significantly lower than the $2.73 per gram typical of current separation processes.
“We concentrated on reducing chemical costs while utilizing widely available reagents, positioning our method as a competitive alternative to existing technologies,” Schelter adds.
Life-cycle analysis further confirmed that the elimination of volatile organic chemicals and hazardous solvents drastically minimizes environmental and health risks. The assessment showed that their process significantly outperforms traditional methods based on metrics such as Smog Formation Potential and Human Toxicity by Inhalation Potential, achieving improvements by an order of magnitude or more.
“This translates into fewer greenhouse gas emissions and reduced hazardous waste production, which is a substantial win for environmental integrity and public health,” Zhang remarks.
Cleaner path forward
Given the innovative nature of their separation technique, Schelter believes that this research opens avenues for further studies into metal separation challenges. “The fundamental principles of molecular recognition identified through our work could potentially be adapted to a wider range of metal separation issues, driving forward advancements in sustainable chemistry and materials recovery,” he proposes.
Eric Schelter is the Hirschmann-Makineni Professor of Chemistry in the Department of Chemistry at the School of Arts & Sciences at the University of Pennsylvania.
Boyang (Bobby) Zhang is a Vagelos Institute for Energy Science and Technology Graduate Fellow in the Schelter Group at Penn Arts & Sciences.
Marta Guron is an adjunct lecturer in the Department of Chemistry and manages projects in the Office of Environmental and Radiation Safety.
The research was supported by various institutions, including the Vagelos Institute for Energy Science and Technology, the National Science Foundation, and the U.S. Department of Energy.
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