France Discovers Bacteria for Recovering Rare Earths
- Category: tungsten‘s News
- Published on Saturday, 07 August 2021 12:28
As European countries seek to reduce their dependence on rare earths, France's researchers have discovered a potentially powerful ally: bacteria that could help extract the element from slag heaps.
Tons of discarded ores containing nickel, copper, and cobalt are the only domestic source of rare earths on the African continent, as well as discarded mobile phones, computers and other technological equipment. Europeans are aware of this dependence on China. “We need to find alternative sources of supply," said Anne-Gwenaelle Guezennec, an engineer at the French Geological Survey in Orléans.
These 17 rare earth metals are also vital to magnets, wind turbines and other advanced applications. They are found in very small amounts in various ores, most of which are in Asia. Gravel powders in a pure state have unique physical and electronic properties that can reinforce a range of materials, from chemical catalysts to magnets and glass.
However, it is difficult to obtain their mining and extraction technology, which requires the use of toxic chemicals under high pressure and high temperature, and consumes a lot of energy.
Geologists from France are exploring more environmentally friendly methods. "We enlist advantage of the very special properties of certain microorganisms and bacteria found in the subsoil," Guezennec said.
In the Orleans laboratory, the process begins by crushing piles of rocks or "tailings" left over from traditional mining and dissolving them in a liquid.
Then according to the metal you are looking for, different bacterium are injected, as well as common nutrients such as oxygen and potassium or nitrogen to "feed" the bacteria.
Then, the bioreactor machine heats and rapidly stirs the solution in gray-green or mustard-yellow colors to start the extraction process
"Bacteria allows us to do this at relatively low temperatures, between 30 and 50 degrees," Guezennec said.
"And it doesn't need to be pressurized, so these are very stable processes, and the cost is not high."
After years of testing, the laboratory is preparing to launch large-scale production tests to extract rare earths and cobalt, copper and nickel from slag dumps in Finland and New Caledonia. Guezennec said: "This is actually for use in any place where there is a slag pile containing metal."
But this process requires specialized equipment to use electrolysis to remove metal from the liquid, which is beyond the capabilities of the laboratory. Guezennec said: "We are waiting for industrial players " to intervene.
In a noisy place in the Orleans laboratory, piles of electronic waste hit the conveyor belt, and powerful magnets picked out other magnets and other metal parts from other debris.
"Usually, magnets account for 1.5% to 3% of hard drives," said Nour-eddine Menad, an engineer in the laboratory waste and raw materials department.
"This means that with two tons, you can recycle 30 to 35 kilograms of magnets," he said. "And a magnet contains 30% rare earth elements."
Once the anti-corrosion coatings of nickel and copper are removed, the magnet separates rare earths and other metals through a multi-step process, this time using a standard, more energy-intensive solution.
Yannick Maynard, head of the investigation and recovery program, said that the development of this "urban mine" is crucial. "This is basically our only option to reduce the economy's dependence on Asian suppliers."
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