Instead of chemicals, electric currents may help mine the valuable raw materials.
Researchers at the Chinese Academy of Sciences have developed a more environmentally friendly method for mining rare earths. This could shorten the mining time by about 70 percent and increase the extraction rate by about 30 percent, China’s Global Times reports. In addition, impurities are to be reduced by 70 percent. The method was developed by a team led by Professor He Hongping of the Guangzhou Institute of Geochemistry.
The new mining technology is to be used primarily in so-called ion adsorption clays, a type of deposit that is particularly typical for southern China. Rare earths are deposited in clay layers that have formed on the surface of rocks over the course of time as a result of weathering. Ion adsorption clays have a high content of heavy rare earths such as terbium and yttrium, which are used in a wide variety of technologies.
Until now, the raw materials have been dissolved from the rock with the help of leaching, usually based on ammonium salts. However, this is considered polluting and of low efficiency; problems that He Hongping’s team wanted to address. The process they developed uses electric currents to accelerate the movement of the extracted metals, leaching agents and other materials such as water. According to the scientists, the need for chemicals and the resulting water pollution can be greatly reduced.
The method, which has been tested through experiments and field trials, was first presented in November in the journal Nature Sustainability. Now the first industrial trial has taken place using a demonstration plant with 5,000 tons of soil, the Global Times writes. The researchers presented their findings Sunday at a meeting in Meizhou City in southern China’s Guangdong Province. The next step is to push for industrial application of the findings.
New Process Could be ‘Game Changer’
Given the critical role of rare earths in the energy transition, any reduction in the environmental impact of mining is welcome, Henning Prommer, an environmental engineer at the University of Western Australia familiar with electrokinetic mining, told Science magazine. The strategy is a “game changer” provided it is feasible on a large scale, the Global Times quotes Anouk Borst, a geologist at Belgium’s KU Leuven.
In recent decades, China has become the market leader in the mining and processing of rare earths. Due to less strict environmental regulations and cheaper production in the People’s Republic, competitors from the USA, for example, have found it increasingly difficult to keep up. Given the currently growing efforts of Western countries to revive their domestic raw material value chains, China is now increasingly researching innovations in rare earth mining to secure its position and counter the new competition.
This involves both more environmentally friendly and more efficient mining methods. The rare earth industry is also to be upgraded in terms of quality, as more can be earned from intermediate or end products such as electric cars or wind turbines than from unprocessed raw materials (we reported). At the same time, Beijing is securing more influence on pricing and reducing internal competitive pressure through the ongoing consolidation of the industry. In this context, the government is also taking stricter action against illegal mining.
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