Bacteria enlisted in French push for rare earths autonomy

Glass jars containing pulverised electronics are injected with bacteria at a lab in western France by engineers aiming to extrac
Glass jars containing pulverised electronics are injected with bacteria at a lab in western France by engineers aiming to extract rare earth metals.

As Europe seeks to reduce its reliance on China for the rare earth metals needed for modern batteries and electronics, French researchers have found a potentially potent ally: bacteria that can help extract the elements from mine slag heaps.

The tonnes of discarded ore, which contain nickel, copper and cobalt, are the continent's only domestic source of , along with discarded phones, computers and other tech gear.

"Europeans have woken up to this dependence on China and said, 'We need to find alternative supply sources'," said Anne-Gwenaelle Guezennec, an engineer with the French Geological Survey (BRGM) in Orleans.

The 17 , also vital for magnets, and other advanced applications, are found in minute quantities within various ores, most of which are in Asia.

Gritty powders in their pure states, they have unique physical and that can enhance a range of materials, from chemical catalysts to magnets and glass.

But the mining and extraction techniques to obtain them are difficult, requiring applied at and temperatures, consuming significant amounts of energy.

The French geologists are exploring instead more environmentally-friendly approaches.

"We enlist the very specific properties of certain micro-organisms, bacteria that we find in the subsoil," Guezennec said.

Rare earth metals are needed for modern batteries and electronics
Rare earth metals are needed for modern batteries and electronics.

Rock soup

At the Orleans lab, the process starts by pulverising mounds of rocks, or "tailings," left over from traditional mining and dissolving them in liquid.

Different bacteria are then injected, depending on the metal sought, along with oxygen and common nutrients like potassium or nitrogen to "feed" the bacteria.

A bioreactor machine then heats and rapidly agitates the solutions, in colours like grey-green or mustard yellow, setting the extraction process in motion.

"The bacteria allows 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 pressurised, so these are very stable processes that are not very expensive."

After years of testing, the lab is preparing to launch tests for large-scale production, extracting rare earths and cobalt, copper and nickel from slag heaps in Finland and New Caledonia.

Europe is seeking to reduce its reliance on China for the rare earth metals needed for modern batteries and electronics
Europe is seeking to reduce its reliance on China for the rare earth metals needed for modern batteries and electronics.

"This is really aimed at being used anywhere there are slag heaps that contain metal," Guezennec said.

But that process, requiring specialised equipment to remove the metals from the liquid using electrolysis, is beyond the lab's capacities.

"We're waiting for industrial players" to step in, Guezennec said.

'Urban mine'

At a noisier part of the Orleans lab, piles of electronic trash clatter onto conveyor belts where powerful magnets pick out other magnets and other metallic parts from the rest of the detritus.

"Normally magnets make up 1.5 to 3 percent of a ," said Nour-eddine Menad, an engineer at the lab's waste and raw materials unit.

"That means in two tonnes, you can recover 30 to 35 kilogrammes (65-75 pounds) of magnets," he said. "And a magnet contains 30 percent of rare earths."

Preparing to separate magnets and other usable parts from tech trash at the lab
Preparing to separate magnets and other usable parts from tech trash at the lab.

Once anti-corrosion coatings of nickel and copper are removed, the magnets go through a multi-step process to separate the rare earths and other metals, this time using standard—and more energy-consuming—acidic solutions.

Exploiting this "urban mine" is crucial, said Yannick Menard, the head of the Survey's recycling programme.

"It's basically our only alternative to make an economy less dependent on Asian suppliers."


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Citation: Bacteria enlisted in French push for rare earths autonomy (2021, July 20) retrieved 28 July 2021 from https://phys.org/news/2021-07-bacteria-french-rare-earths-autonomy.html
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