Bacteria help extract rare earths from mine slag heaps

Klondyke lead mine slag heaps. (Reference image by Terry Hughes, Flickr).

Researchers at the French Geological Survey are looking at ways to extract rare earth elements from mine slag heaps using bacteria found in the subsoil.

According to a report by the agency AFP, the process starts by pulverizing mine tailings and dissolving them in liquid.

Then, the scientists inject different bacteria depending on the metal they are looking for. They also inject oxygen and nutrients like potassium or nitrogen to feed the microorganisms.

These solutions are immediately heated at between 30 and 50 degrees Celsius and agitated by a bioreactor, which kicks off the extraction process without the need for pressurizing.

Given that they have achieved success in the lab, the French group said it is now ready to launch tests for large-scale production, extracting rare earths, as well as cobalt, copper, and nickel from slag heaps in Finland and New Caledonia.

They said the process can be used anywhere there are piles of ore that contain metal. However, since specialized equipment is required to remove the metals from the liquid using electrolysis, the key now is for industrial partners to step in.

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