Rare earth elements used in smartphones and electric vehicles could be extracted from the ground more sustainably using electric fields.

Today, most rare earth metals used in electronics are mined by using toxic chemicals to extract the elements from mineral ore. During the mining process, thousands of tonnes of chemical waste are released, which can pollute nearby groundwater and soil. But concentrating those elements together using electric charges could drastically cut the amount of environmentally damaging chemicals needed.

“Imagine a crowd being guided through a maze by directional lights – similarly, rare earth elements are driven from the ore by the electric field toward specific collection points,” says Jianxi Zhu at the Guangzhou Institute of Geochemistry in China. “This controlled movement ensures efficient mining with minimal environmental disruption.”

Zhu and his colleagues created flexible, sheet-like plastic electrodes – each 10 centimetres wide with customisable lengths – made from non-metallic materials that can conduct electricity. At a rare earth deposit in southern China, they inserted 176 electrodes into individual holes drilled 22 metres into the rock.

Next, they injected ammonium sulphate, a type of inorganic salt, into the ore to dissolve and separate out the rare earth elements as charged ions. They then activated the electrodes to create an electric field between positively and negatively charged electrodes. That electric field moved the rare earth elements toward the positively charged electrodes, concentrating them together. The elements could then be transferred to treatment ponds for additional purification and separation processes.

The approach enabled the researchers to greatly reduce the amount of harmful chemicals used in extracting the rare earth elements, slashing the related ammonia emissions by 95 per cent. That could help prevent much of the water and soil contamination that today’s rare earth mining operations produce.

This electric field process also proved 95 per cent efficient in extracting rare earth elements from 5000 tonnes of ore, whereas chemical processes alone usually achieve just 40 to 60 per cent efficiency, says Zhu.

But the new mining method would also raise electricity costs for rare earth mining operations – and increased electricity consumption could mean more carbon emissions. The researchers have already shown how to reduce electricity costs by powering just one-third of the electrodes at any given time. Access to renewable power and improvements in electrode technology could also help bring down the energy demands and emissions of the mining process, says Zhu.

This technology has potential to be a sustainable solution in the near future, says Amin Mirkouei at the University of Idaho. But he warned that it faces practical challenges, including the energy costs of the method and the long time – 60 days – it requires to ramp up to 95 per cent efficiency.

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