Molds as a battery recycler

Fungal colonies extract valuable metals from old lithium-ion batteries

Batteries, especially lithium-ion batteries, contain valuable metal raw materials - molds can help to regain them. © Farzin Salimi / thinkstock
Read out

Helpers from nature: In the future, mold fungi could help to recover valuable metals from old batteries. As an experiment shows, these mushrooms can extract up to 85 percent of lithium and 48 percent of cobalt from used lithium-ion batteries. This biological extraction is cheap and much more environmentally friendly than previously common methods, as the researchers report.

Whether it's a smartphone, laptop or camera, they all contain lithium-ion batteries - and these batteries eventually all end up in the garbage, along with their valuable ingredients. For although it is already clear that in the future a lithium deficiency threatens, so far only a small part of the metal raw materials from lithium-ion batteries is recycled.

Help from nature

"A method to effectively recover lithium and cobalt from the spent lithium-ion batteries is therefore urgently needed, " explains Jeffrey Cunningham of the University of South Florida. The problem here: So far, high temperatures and corrosive chemicals are needed to extract these metals from the batteries - this is complex and not environmentally friendly.

But the researchers have now discovered helpers from nature who could make this metal recycling much easier and more environmentally friendly in the future. It has long been known that some bacteria and fungi naturally process heavy metal compounds in order to extract energy from them. Whether three of these "metal eaters" can extract lithium and cobalt from the batteries, Cunningham and his colleagues have now tested.

Pulverized battery cathodes as mushroom food

The researchers selected three common mold fungi: Aspergillus niger, Penicillium simplicissimum and Penicillium chrysogenum. "We selected these species because they have already proven to be effective metal collectors in other types of waste products, " explains Cunningham. "Mushrooms produce organic acids and these acids dissolve the metals out of the materials." Display

The fungi Aspergillus niger, Penicillium simplicissimum and Penicillium chrysogenum can extract lithium and cobalt from battery cathodes. Aldo Lobos

For the test, the researchers first pulverized the cathodes of the old batteries and thus the parts containing the valuable metals. This powder gave them a nutrient medium with the mushrooms. "The interaction of the fungi, the acids they produce and the powdered cathodes extract valuable lithium and cobalt, " says Cunningham.

Up to 85 percent of the lithium extracted

And indeed: The molds extracted up to 85 percent of the lithium from the battery cathodes and up to 48 percent of the cobalt, as the researchers report. The fungi achieved this mainly through the oxalic acid and citric acid they produced. A third acid, gluconic acid, proves to be less effective.

After the work of the fungi, the metals are dissolved in the liquid, acidic medium. The next step is to separate lithium and cobalt from this solution. "We already have some ideas on how to do that, " says Cunningham. "The biggest step forward is the metal extraction by the fungi."

According to the researchers, this recycle method could kill two birds with one stone: it helps keep more used batteries out of landfills and waste incinerators and recycle their raw materials instead. That would be necessary, because only recently did a study prove that the recycling of electronic waste in Europe hardly works. At the same time, the fungus method could help to increase the stock of the urgently needed lithium. (252nd National Meeting & Exposition of the American Chemical Society)

(American Chemical Society, 22.08.2016 - NPO)