Fungi to help recycle precious metals from waste batteries
Mon 22 Aug 2016
Members of the American Chemical Society (ACS) have designed a new way to extract valuable metals from waste batteries, using three strains of naturally-occurring fungi.
The fungal property which was of particular interest to the researchers was the material’s strong ability to deal with heavy metals. Fungi are resilient, abundant and are quick to replicate, as well as being cheap to buy and maintain.
Applied to battery recycling, a mix of fungi (Aspergillus niger, Penicillium simplicissimum and Penicillium chrysogenum) can be put to work on pulverised battery cathodes to recover precious lithium and cobalt. The mould produces organic acids, such as oxalic and citric acid, which are able to extract up to 85% of the lithium and around 48% of the cobalt.
The cocktail of fungi used in this case, typically used to extract metals in other contexts such as from decommissioned machinery, was chosen over other fungal products like gluconic acid which were found to be ineffective.
Currently, batteries are disposed of in landfills and incinerators, where high temperatures and harsh chemicals can release harmful emissions into the atmosphere. While this environmentally safe, natural method provides a solution, the challenge remains how to collect and process hundreds of millions of spent devices.
Jeffrey Cunningham, the study lead, explained: ‘Fungi are a very cheap source of labour… The idea first came from a student who had experience extracting some metals from waste slag left over from smelting operations…The demand for lithium is rising rapidly, and it is not sustainable to keep mining new lithium resources.’
For now, the method extracts the metals in an inseparable liquid, but the team is investigating new techniques to individually recover all of the original materials.
‘We have ideas about how to remove [them], but at this point, they remain ideas,’ added Cunningham. ‘However, figuring out the initial extraction with fungi was a big step forward.’