Biomining: Researchers Use Viruses to Extract Rare Earth Metals

Rare earth metals are coveted raw materials needed for many technical devices. However, there are only a few places where they are mined and refined, mainly in China. Researchers are looking for alternative extraction methods. A team from the University of California (UC) in Berkeley wants to use viruses for this purpose.

Seung-Wuk Lee calls the process, which he and his describe in the journal Nano Letters, biomining. It uses "a programmable biological tool" to perform a task that currently requires toxic chemicals and a lot of energy, he said. "Our method is not only environmentally friendly, but also incredibly simple and requires little more than a mixing container and a heater."

For their project, the researchers use bacteriophages. These are viruses that attack bacteria but are harmless to humans. The researchers have genetically modified these phages to extract rare earth elements from water.

A peptide to bind them

To do this, the researchers attached two proteins to the surface: One is a lanthanide-binding peptide, which ensures that it binds to rare earths in the water.

The other protein ensures that the virus also releases the raw materials again. It is an elastin-motif peptide, which functions like a temperature-sensitive switch: when the virus is slightly warmed, it precipitates along with its cargo.

The researchers tested the process by adding the viruses to a tank of mine water. The viruses reacted as planned: they exclusively bound to the rare earth ions. When the water was heated, they sank to the bottom of the tank. After draining the liquid, a sediment of viruses and metals remained. By changing its pH value, the viruses finally released the rare earth metals. The viruses themselves were then reusable and were just as effective as before.

Common Rare Earths

In fact, the 17 elements classified as rare earth metals are not that rare at all: one kilogram of soil contains an average of 200 milligrams of them. But that is the problem: their even distribution in the soil makes mining difficult, which is only worthwhile at high concentrations.

Therefore, other extraction methods are being sought, such as biomining. Other researchers rely on phytomining. Instead of viruses, they use plants to extract the coveted raw materials from the earth.

"This is an important step towards more sustainable mining and raw material extraction," said Lee. "Our biological solution offers a more environmentally friendly, cost-effective, and recyclable way to secure the critical materials we need for a clean energy future while protecting the environment."

The team assumes that the viruses can also be used in the recycling of electronic waste.

(wpl)