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As Europe seeks to reduce its dependence on China for rare earth metals needed by modern batteries and electronics, French researchers have found a potentially powerful ally: bacteria that can help extract the elements of the mining slag heaps.
Tons of discarded ore, which contain nickel, copper and cobalt, are the continent’s only national source of rare earths, along with discarded phones, computers and other tech equipment.
“The Europeans realized this dependence on China and said: ‘We have to find alternative sources of supply” “, said Anne-Gwenaelle Guezennec, engineer at the French Geological Service (BRGM) in Orleans.
The 17 rare earth metals, also vital for magnets, wind turbines and other advanced applications, are found in trace amounts in various ores, most of which are found in Asia.
Pure granular powders, they have unique physical and electronic properties that can enhance a range of materials, from chemical catalysts to magnets and glass.
But the extraction and extraction techniques to obtain them are difficult, requiring toxic chemicals applied at high pressures and temperatures, consuming significant amounts of energy.
French geologists are instead exploring more environmentally friendly approaches.
“We use the very specific properties of certain micro-organisms, bacteria that are found in the subsoil”, specifies Guezennec.
– Rock soup –
At the Orleans laboratory, the process begins by pulverizing mounds of rock, or “tailings”, left over from traditional mining and dissolving them in a liquid.
Different bacteria are then injected, depending on the desired metal, as well as oxygen and common nutrients such as potassium or nitrogen to “feed” the bacteria.
A bioreactor machine then heats up and rapidly agitates the solutions, in colors like gray-green or mustard yellow, starting the extraction process.
“The bacteria allow us to do this at relatively low temperatures, between 30 and 50 degrees (85-120 Fahrenheit),” Guezennec said.
“And it doesn’t need to be pressurized, so it’s very stable processes that aren’t very expensive.”
After years of testing, the laboratory is preparing to launch large-scale production tests, extracting rare earths and cobalt, copper and nickel from waste heaps in Finland and New Caledonia.
“This is really meant to be used wherever there are slag heaps that contain metal,” Guezennec said.
But this process, requiring specialized equipment to remove metals from the liquid by electrolysis, is beyond the capabilities of the laboratory.
“We are waiting for the intervention of industrial players,” said Guezennec.
– ‘Urban mine’ –
In a noisier part of the Orleans lab, piles of electronic waste crash onto conveyor belts where powerful magnets pick up other magnets and other metal parts from the rest of the trash.
“Normally magnets make up 1.5 to 3% of a hard drive,” said Nour-eddine Menad, engineer in the laboratory’s waste and raw materials unit.
“This means that in two tonnes you can recover 30-35 kilograms (65-75 pounds) of magnets,” he said. “And a magnet contains 30 percent rare earths.”
With the anti-corrosion nickel and copper coatings removed, the magnets undergo a multi-step process to separate the rare earths and other metals, this time using standard acidic solutions – and more energy-hungry.
The operation of this “urban mine” is crucial, said Yannick Menard, head of the Inquiry’s recycling program.
“This is basically our only alternative to make an economy less dependent on Asian suppliers.”
i have / js / cb / kjm
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