Mining rare earth metals has environmental impacts
Joe Bagwitz/Bloomberg via Getty Images
Rare earth elements used in smartphones and electric cars could be extracted from the ground in a more sustainable way using electric fields.
Currently, most rare earth metals used in electronics are mined by extracting the elements from ores using toxic chemicals. During the mining process, thousands of tons of chemical waste are released, which can contaminate nearby groundwater and soil. However, using electrical charges to concentrate these elements together could significantly reduce the amount of environmentally harmful chemicals needed.
“Imagine a crowd being guided through a maze by directional lights,” said Jianxi Zhu of the Guangzhou Institute of Geochemistry in China. It will be discovered,” he said. “This controlled movement ensures efficient mining with minimal environmental damage.”
Zhu and his colleagues created flexible sheet plastic electrodes 10 centimeters wide and customizable in length, made from non-metallic materials that can conduct electricity. At a rare earth deposit in southern China, researchers inserted 176 electrodes into individual holes drilled 22 meters into the rock.
They then injected ammonium sulfate, an inorganic salt, into the ore to dissolve the rare earth elements and separate them as charged ions. The electrodes were then activated to create an electric field between the positively and negatively charged electrodes. That electric field moved the rare earth elements toward the positively charged electrode, concentrating them together. The elements can then be transferred to a treatment pond for additional purification and separation processes.
This approach allowed the researchers to significantly reduce the amount of harmful chemicals used to extract the rare earth elements and reduce associated ammonia emissions by 95%. This could help prevent much of the water and soil pollution caused by today’s rare earth mining operations.
The electric field process also proved to be 95% efficient in extracting rare earth elements from 5,000 tons of ore, whereas chemical processes alone typically only achieve 40 to 60% efficiency, Zhu said. says Mr.
However, new mining methods also increase electricity costs for rare earth mining operations, and increased electricity consumption could mean increased carbon emissions. Researchers have already shown how to reduce electricity costs by powering only one-third of the electrodes at any given time. Access to renewable electricity and improvements in electrode technology could also help reduce the energy demands and emissions of the mining process, Zhu said.
Amin Mirkuei of the University of Idaho says this technology could become a sustainable solution in the near future. But he warned that this method faces practical challenges, including high energy costs and the long 60-day time it takes to reach 95% efficiency.
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