Baths beget better battery recycling

A team of Canadian researchers has found a more efficient and environmentally friendly way to recycle alkaline batteries.

The method, which involves bathing spent batteries in water-based solutions, can effectively extract potassium, manganese, and zinc.

“We focused on the extraction of the main minerals present in alkaline batteries because they represent more than 70% of the volume of spent batteries in North America,” says Noelia Muñoz García, a researcher at the Université de Sherbrooke, Canada, and lead author on a paper published in the Journal of Chemical Technology and Biotechnology.

“The main problem of improper disposal of spent alkaline batteries is that compounds of potassium, zinc and manganese can leach into the soil and pollute groundwater, posing threats to the environment and human health, such as ecotoxicity and abiotic depletion,” says García.

The technique uses hydrometallurgy, where a water-based solution is used to leach metals out of a substance.

Unlike other battery-recycling processes, hydrometallurgy doesn’t need high temperatures and pressures to work, which makes it much less energy intensive.

Traditionally it’s also rarely cost-effective, because it tends to leach all metals from a substance into one solution, which then needs to be painstakingly separated.

These researchers dodged the problem by using three different leaching steps, all with a different bath, on their batteries.

In the first step, they used water to remove most of the potassium. In the second sulphuric acid helped remove most of the manganese. And in the third step, they combined sulphuric acid with hydrogen peroxide, which bound to and removed most of the zinc.

Using this technique, they could extract 76.8% of the original potassium, 86.1% of the manganese, and 99.6% of the zinc from their batteries.

“The most important factor was to find a suitable leaching agent (in this case sulphuric acid) and a reducing agent (hydrogen peroxide), which increased the extraction of these minerals,” says corresponding author Antonio Avalos Ramirez, also at the Université de Sherbrooke.

“The next steps will be to develop separation and purification units for obtaining zinc and manganese at a quality good enough to introduce them to the market and use them in the production of new goods,” says Ramirez.

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