Fungi extracts precious elements from batteries

Researchers in the US have used fungi to extract metals from rechargeable batteries.

The research began in order to tackle the issue of increasing numbers of rechargeable batteries being incinerated or going to landfill. Using fungi is a more environmentally friendly way to separate the desired metals than other methods that require high temperatures and harsh chemicals.

Dr Jeffrey Cunningham, team leader from the University of South Florida, said: “The idea first came from a student who extracted some metals from waste slag left over from smelting operations. 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.”

With the use of Aspergillus niger, Penicillium simplicissimum and Penicillium chrysogenum, the scientists extracted cobalt and lithium from waste batteries. These fungi were chosen as they were known to be effective at extracting metals from other waste products.

The batteries were first taken apart before the cathodes were pulverised and the pulp exposed to the fungi. They create oxalic and citric acid and the study showed they were able to extract up to 85% of the lithium and 48% of the cobalt present inside the spent battery cathodes.

Cunningham said: “Fungi naturally generate organic acids, and the acids work to leach out the metals. Through the interaction of the fungus, acid and pulverised cathode, we can extract the valuable cobalt and lithium. We are aiming to recover nearly all of the original material.”

The next step for the scientists is to separate the cobalt and lithium — which along with other substances — is in a liquid medium.

Cunningham told Laboratory News: “There are some technologies that are already available for removal of ions from liquid solution, such as ion exchange onto a solid resin. While I was at the American Chemical Society (ACS) national meeting, I also saw a presentation by a team developing liquid surfactants for extraction of metal ions from liquid solution. The ions are chelated by an ionic end of the surfactant, with air bubbled into the solution, creating a foam with ions that can be harvested. ”

However this was not the only possible way to separate out the cobalt ions and so at the moment the researchers are focusing on the chemical reactions caused by the fungi.

The study was presented at the ACS national meeting in Philadelphia this month.