The mining of rare earth metals has environmental consequences
Joe Buglewicz/Bloomberg via Getty Images
Rare earth elements used in smart phones and electric vehicles could be more permanently extracted from the earth using electric fields.
Today, most of the rare earth metals used in electronics are extracted using toxic chemicals to extract the elements from ores. During the mining process, thousands of tons of chemical waste are released, which can contaminate the surrounding ground water and soil. But concentrating these elements together using electrical charges could significantly reduce the amount of chemicals that harm the environment.
“Imagine a crowd being led through a maze by directional lights, similarly the electric fields from the rare earth element ore to specific collection points,” he 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 centimeters wide and customizable in length, made of non-metallic materials that can conduct electricity. At a rare earth deposit in southern China, 176 electrodes were inserted into individual holes drilled 22 meters into the rock.
Ammonium sulfate, a type of inorganic salt, was then injected into the ore to dissolve and separate the rare earth elements as charged ions. They then activated the electrodes to create an electric field between the positively and negatively charged electrodes. This electric field drove the rare earth elements to the positively charged electrodes, concentrating them together. The elements can then be transported to treatment ponds for additional purification and separation processes.
This approach allowed the researchers to greatly reduce the amount of harmful chemicals used to extract the rare earth elements, reducing the associated ammonia emissions by 95 percent. This could help prevent much of the water and soil pollution caused by today’s rare earth mining operations.
This electric field process also demonstrated 95 percent extraction efficiency rare earth elements From 5,000 tons of ore, while chemical processes alone achieve 40 to 60 percent efficiency, Zhu says.
But the new mining method would also raise electricity costs rare earth mining operations – and increased electricity consumption can lead to more carbon emissions. Researchers have already shown how to reduce electricity costs by powering only a third of the electrodes at any given time. Access to renewable energy and improvements in electrode technology can also help lower the energy demands and emissions of the mining process, Zhu says.
He says this technology has the potential to be a permanent solution in the near future Amin Mirkouei at the University of Idaho. But he warned that it faces practical challenges, including the method’s energy costs and the long time it takes (60 days) to reach 95 percent efficiency.
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