BY KATIE - MYGREENPOD, 30 August '16

Researchers show fungi can recycle cobalt and lithium from rechargeable batteries

Rechargeable batteries in smartphones, cars and tablets can be charged again and again – but they don’t last forever. Old batteries often wind up in landfills or incinerators – potentially harming the environment – and valuable materials remain locked inside.

Now, a team of researchers is turning to naturally occurring fungi to drive an environmentally friendly recycling process to extract cobalt and lithium from tons of waste batteries.

Demand for lithium

The researchers presented their work this week at the 252nd National Meeting & Exposition of the American Chemical Society (ACS), which features more than 9,000 presentations on a wide range of science topics.

‘The idea first came from a student who had experience extracting 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.’

JEFFREY A. CUNNINGHAM, PH.D.
Project team leader

Electronic waste

Mobile phones, portable music players, laptop computers, tablets and cameras all use rechargeable batteries, with lithium-ion (Li-ion) batteries now dominating the market. It’s uncertain that the demand for lithium (Li) and cobalt (Co), required in the form of LiCoO2 for the cathode of Li-ion batteries, can be met by the available supply.

Although a global problem, the US leads the way as the largest generator of electronic waste. It’s unclear how many electronic products are recycled, but many head to a landfill to break down slowly in the environment or go to an incinerator to be burned, generating potentially toxic air emissions.

It’s estimated that by 2030 we’ll be disposing of 30,000 metric tons of Li-ion batteries per year. From the standpoint of environmental sustainability, we need to find a method for recovering Li and Co from spent Li-ion batteries.

The power of fungi

While other methods exist to separate lithium, cobalt and other metals, they require high temperatures and harsh chemicals. Cunningham’s team is developing an environmentally safe way to do this with organisms found in Nature – in this case fungi – and putting them in an environment where they can do their work.

To drive the process, Cunningham and Valerie Harwood, Ph.D., both at the University of South Florida, are using three strains of fungi – Aspergillus niger (main image), Penicillium simplicissimum and Penicillium chrysogenum.

How it works

The team first dismantles the batteries and pulverises the cathodes before exposing the remaining pulp to the fungus.

‘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.’

JEFFREY A. CUNNINGHAM, PH.D.
Project team leader

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

The cobalt and lithium remain in a liquid acidic medium after fungal exposure, Cunningham notes. Now his focus is on how to get the two elements out of that liquid.

Other researchers are also using fungi to extract metals from electronic scrap, but Cunningham believes his team is the only one studying fungal bioleaching for spent rechargeable batteries.

Cunningham, Harwood and graduate student Aldo Lobos are now exploring different fungal strains, the acids they produce and the acids’ efficiencies at extracting metals in different environments.

Click here to find out more about the 252nd American Chemical Society National Meeting & Exposition.