New metal extraction technique could offer an eco-friendly solution for battery waste

As global energy demands continue to rise, the role of batteries is becoming increasingly critical. However, the improper disposal of spent batteries poses significant environmental hazards due to their metal content.

According to the researchers, recycling these metals not only mitigates environmental risks but also provides a sustainable source of valuable materials.

The paper, published in the Journal of Chemical Technology and Biotechnology, presents a technique for the extraction of potassium, zinc and manganese that the researchers claim is cheaper and more energy-efficient than other existing methods.

In a statement, Noelia Muñoz García, a researcher at the Université de Sherbrooke, Canada, and lead author of the study, said: “We focused on the extraction of the main minerals present in alkaline batteries because they represent over 70 per cent of the volume of spent batteries in North America.

“This research supports the principles of the circular economy, where materials are reused and recycled, creating a closed-loop system. This reduces waste and can lead to long-term economic sustainability by maximising the utility of resources, which is one of the main objectives in current treaties such as the Paris Agreement.”

According to the researchers, 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.

The study’s technique draws on hydrometallurgy, which uses aqueous solutions to extract the metals – known as ‘leaching’. Hydrometallurgy can be carried out at room temperature, making it more energy-efficient than methods that require high temperatures.

In other hydrometallurgical processes, all metals can be extracted in one leaching step, producing a complex leachate composition that is costly to separate out into its components. The researchers said that their method instead uses three separate steps for the extraction.

By removing the metals in three phases using different leaching agents, the researchers were able to produce higher quality leachates, lowering the costs of downstream purification.

Overall, the process resulted in a total extraction efficiency of 99.6 per cent for zinc and 86.1 per cent for manganese.

“The most important factor was to find a suitable leaching agent [sulfuric acid] and a reducing agent [hydrogen peroxide], which increased the extraction of these minerals,” said Antonio Avalos Ramirez, a researcher at the Université de Sherbrooke and corresponding author of the study.

Looking ahead, the researchers want to scale up their extraction technique at an industrial and commercial scale, and develop separation and purification units for obtaining zinc and manganese at a quality good enough to introduce them to the market.