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.
So Jeffrey A. Cunningham of the University of South Florida is looking for a greener way to recycle lithium batteries. At the American Chemical Society national meeting in Philadelphia on Sunday, Cunningham reported on research that may pave the way for fungi to play a role in future battery recycling.
The idea is to promote growth of fungal colonies on pulverized batteries. As these microbes grow, they produce organic acids that would then help leach out the valuable metals from the batteries, making the metals easy to isolate for further processing.
In work toward that goal, the South Florida team has identified conditions for quickly growing three candidate strains of fungi; has analyzed the organic acids they generate as they multiply; and has evaluated the effectiveness of commercial versions of those acids in leaching battery metals.
Oxalic acid and citric acid, which are less harsh than common mineral acids, can extract up to 85% of the lithium and nearly half of the cobalt from cathodes of spent batteries, according to data Cunningham presented during a session sponsored by the Division of Environmental Chemistry. In contrast, gluconic acid is ineffective in extracting either metal.
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.
This article is reproduced with permission from Chemical & Engineering News (© American Chemical Society). The article was first published on August 23, 2016.