It’s electric! Technique could clean up mining of valuable rare earth elements

Electric cars, wind turbines, and lighting can keep the environment clean, but they can also be dirty. Rare earth elements are used in magnets and glowing phosphors in flat screens. In order to capture REEs from the clay deposits that are found, they have to be polluted.

A Chinese group has developed a method of mining that uses electric currents to free the REEs, which is much less harmful to the environment. Anouk Borst, a geologist at KU Leuven, says that the strategy could be a game-changing one.

REEs are plentiful in the Earth's crust. It's difficult to find deposits that are economical. Heavy REEs, those with high atomic numbers, such as dysprosium, yttrium, and terbium, are usually found in the form of clay. The elements are stuck to the clay particles in theion-adsorption deposits. They are usually pulled from the ground by pumping large quantities of Ammonium Sulfate into the ground. The REEs that are pulled from the clay are collected for processing.

Lay waste to large tracts of land can cause a lot of problems. Roughly 80% of the world's supply of heavy REEs come from ion-adsorption deposits in southern China and adjacent parts of Myanmar, where environmental regulations are poorly enforced. The light REEs are found in hard rock and are mined in different ways.

A cleaner alternative was thought to be offered by the Chinese Academy of Sciences. It has been proposed for copper and gold mining to use the approach in which the top and bottom of a volume of soil have an electric field. It has the potential to surpass traditional mining techniques in terms of efficiency, environmental impacts, and economics.

The Chinese team tried the technique on a 14-ton hunk of clay after starting with a bench top experiment. The method used a higher percentage of the REEs. The cleaner the soil, the easier it would be to process it. The process could cut mining costs in half.

It remains to be seen if the technique can be scaled up. Hongping He is the director of GIG and co-author on the paper. He says that they will divide the site into sections to keep the electric current and voltage low so that they don't harm the surrounding flora and fauna. A major rare earth supplier has agreed to test the process on a larger scale.

As with all mining methods, it will impact the environment, according to an environmental engineer at the University of Western Australia. He says that any reduction in the environmental impact of mining is welcome.