A greener, cleaner way to extract cobalt from ‘junk’ materials

Siddarth Kara’s best-selling book “Cobalt Red: How Congo’s Blood Powers Our Lives” focuses on the sourcing of cobalt. Core technologies power everything from mobile phones to pacemakers to electric vehicles.

“Perhaps many of us understand how important lithium-ion batteries are to energy storage technology,” said Eric Schelter, the Hirschmann-Makineni Professor of Chemistry at Penn State. “But the sourcing of the materials that make up such batteries may be ethically and The environmental aspects are both worrying and problematic.”

Shelter said that cobalt mining in the Democratic Republic of the Congo accounts for about 70% of global cobalt production. The country has raised concerns about environmental degradation and unsafe working conditions. Large-scale mining will damage the ecosystem and may pollute water sources. Lasting effects on the environment. Additionally, he noted that as demand for battery technology continues to grow, looming cobalt shortages could put pressure on global supply chains.

To that end, one area of ​​research his lab has been focusing on is the separation of key battery metals such as nickel and cobalt. In a new paper published in the journal ChemicalSheldt’s team and collaborators at Northwestern University came up with a “simpler, more sustainable, and cheaper way to separate these two materials from what would otherwise be considered waste.”

“Our chemistry is attractive because it is simple, effective and effectively separates nickel and cobalt – one of the most challenging separation problems in the field,” Sheldt said. “This approach has two main benefits: it increases the ability of mining operations to produce purified cobalt with minimal potential harm to the environment; it solves the nasty problems associated with traditional purification chemicals; and it provides an efficient way to separate nickel and cobalt from waste. Batteries create value.

The right ingredients for selective separation

Typically, cobalt is a by-product of nickel mining, produced through hydrometallurgical methods such as acid leaching and solvent extraction, which separate cobalt and nickel from the ore, the researchers said. This is an energy-intensive method that generates large amounts of hazardous waste.

The process Schelter and his team developed to circumvent this problem is based on a chemical separation technique that exploits the charge density and bonding differences between two molecular complexes: cobalt(III) hexammine and nickel(II) hexammine. things.

“A lot of separation chemistry is about showing the differences between the substances you want to separate,” Shelter said. “In this case, we found the relatively simple and cheap ammonia complexes with nickel and cobalt hexamine The combination is different.

By introducing specific negatively charged molecules or anions, such as carbonate, into the system, they created a molecular solid structure that precipitated the cobalt complex from solution while simultaneously dissolving the nickel complex. Their work showed that carbonate anions selectively interact with cobalt complexes by forming strong “hydrogen bonds”, resulting in stable precipitates. After precipitation, the cobalt-rich solid is isolated by filtration, washed with ammonia, and dried. The remaining solution contains nickel and can be disposed of separately.

First author Boyang said: “This process not only achieves high purity of the two metals – 99.4% purity for cobalt and over 99% purity for nickel – but also avoids the use of organic solvents and strong acids commonly used in traditional separation methods. ” (Bobby) Zhang is a graduate student in the College of Arts and Sciences at the University of Pennsylvania and a graduate student in the Vagelos Institute of Energy Science and Technology. “This is an inherently simple and scalable approach that has environmental and economic advantages.”

Technological Economics and Life Cycle Analysis

In assessing the practical suitability of the new method, the team led by Marta Guron conducted a techno-economic analysis and a life cycle assessment, the former showing an estimated production cost of US$1.05 per gram of purified cobalt, significantly lower than that associated with the reported separation process. That compares to $2.73 per gram.

“Our focus on minimizing chemical costs while also using off-the-shelf reagents makes our approach potentially competitive with existing technologies,” Schelter said.

The life cycle analysis found that the elimination of volatile organic chemicals and hazardous solvents allowed the process to significantly reduce environmental and health risks, which was supported by indicators such as smoke formation potential and inhalation potential for toxicity to humans, where the process scored at least one Orders of magnitude better than traditional methods.

“This means less greenhouse gas emissions and less hazardous waste, which is a huge win for the environment and public health,” Zhang said.

A cleaner path forward

Schelter said there is an exciting basic science aspect to the work because of the way the team accomplished the separation, and he thinks they could go in many different directions and even solve other metal separation problems.

“Based on the unique set of molecular recognition principles that we identified during the course of this work, I think we can extend this work in many different directions,” he said. “We can apply this to other metal separation problems, ultimately driving broader innovation in sustainable chemistry and materials recycling.”

Eric Schhelter is the Hirschmann-Makineni Professor of Chemistry in the University’s Department of Chemistry College of Arts and Sciences at the University of Pennsylvania.

Boyang (Bobby) Zhang is a graduate researcher at the Vagelos Institute of Energy Science and Technology Shelter Group in the College of Arts and Sciences at the University of Pennsylvania.

Marta Guron is an adjunct instructor in the Department of Chemistry and a project manager in the Office of Environmental and Radiation Safety.

Other authors include Andrew J. Ahn, Michael R. Gau, and Alexander B. Webberg from Penn State, and Leighton O. Jones and George C. Schatz from Northwestern University.

This research was supported by the Penn State Vagelos Institute for Energy Science and Technology, the Penn State Vagelos Integrated Energy Research Program, the National Science Foundation Center (Award CHE-1925708), the U.S. Department of Energy Advanced Materials for Energy Water Systems Supported by the Center (Grant 8J-30009-0007A), and the Scientific Advancement Research Corporation (Award #CS-SEED-2024-022).