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Fungi can help recycle battery by leaching out metals from it, says a study

Old batteries often wind up in landfills or incinerators, potentially harming the environment. And valuable materials remain locked inside.

Growing demand for rechargeable lithium batteries used in consumer electronics and electric vehicles is driving efforts to expand battery recycling, primarily to recover lithium, cobalt, and other valuable metals.

But typical battery recycling methods, such as smelting and acid leaching, have significant disadvantages: Smelting is a high-temperature, energy intensive process and both processes generate harmful waste.

Now, a team of researchers is working to use naturally-occurring fungi for an environment-friendly recycling process to extract cobalt and lithium from waste batteries.

“The idea first came from a student who had experience extracting some metals from waste slag left over from smelting operations,” said Jeffrey A. Cunningham, Ph.D. and the project’s team leader.

“We were watching the huge growth in smartphones and all the other products with rechargeable batteries, so we shifted our focus. The demand for lithium is rising rapidly, and it is not sustainable to keep mining new lithium resources,” he said.

While other methods exist to separate lithium, cobalt and other metals, they require high temperatures and harsh chemicals.

To drive the process, Mr. Cunningham and Valerie Harwood, both at the University of South Florida, are using three strains of fungi — Aspergillus niger, Penicillium simplicissimum and Penicillium chrysogenum.

“We selected these strains of fungi because they have been observed to be effective at extracting metals from other types of waste products,” Mr. Cunningham said. “Fungi are a very cheap source of labour.”

The team first dismantles the batteries and pulverises the cathodes. Then, they expose the remaining pulp to the fungus. “Fungi naturally generate organic acids, and the acids work to leach out the metals,” Mr. Cunningham said.

“Through the interaction of the fungus, acid and pulverised cathode, we can extract the valuable cobalt and lithium,” he said.

Results so far show that using oxalic acid and citric acid, two of the organic acids generated by the fungi, up to 85 per cent of the lithium and up to 48 per cent of the cobalt from the cathodes of spent batteries can be extracted.

Now the team plans to study the effectiveness of the fungi-produced versions of the acids, determine how well the fungi tolerate the extracted metals, and evaluate the economic viability of using fungi to recycle battery metals.

The research presented in this study could “potentially lead to a green transformative solution for leaching metals from batteries,” commented Wen Zhang, who attended the symposium.

Zhang, a professor of civil and environmental engineering at New Jersey Institute of Technology, remarked that this process largely mimics natural degradation processes in which acids and enzymes from microbes play important roles in breaking down waste substances. He added that this fungal route seems promising for avoiding the use of hazardous compounds but may suffer from slow kinetics.

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