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Researchers at Southern Illinois University may have discovered a substantial rare earth site in their own backyard — the Hicks Dome in Hardin County, Ill. — and a sustainable method for extracting the critical minerals using algae.
Daniel Hummer, an associate professor of geology at the university, said the Hicks Dome location is the site of a crypto volcano. Essentially, a volcano that failed to penetrate the Earth’s surface, causing the magma to harden underground.
“It seems the magma came from very deep in the Earth, shot up, and formed these ‘fingers’ of dark colored rock where we’re finding rare earth elements,” said Hummer, who specializes in mineral crystallization. “We’re also finding rare earth in surrounding rock called breccia, where very hot water carrying minerals came out of the magma and snaked its way through shattered rock.”
ALGAE ABSORPTION
How did the idea of using algae for extraction come about?
Scott Hamilton-Brehm, an associate professor of microbiology at SIU, said plants can absorb minerals from the ground and incorporate them into their tissues. However, plants have several limitations, including the land space they require, the time it takes for a seed to grow into a plant, and the subsequent growing seasons after the plant matures.
“You need a liquid type of organism that can absorb the minerals,” Hamilton-Brehm said. “This is where microalgae come in. They’re a liquid plant. They require sunlight, they need a source of CO2, and they absorb metals and minerals.”
To conduct the experiment, Hamilton-Brehm and his students created a mini riverbed by filling a cow trough with 50 gallons of water and installing a pump to circulate the water, mimicing a river current. LED lights over the trough acted as the sun.
Geology graduate student Kristina Kohl and Hummer pulverized rock samples containing rare earth into a fine powder and added it to the flowing “riverbed.” Then Hamilton-Brehm’s team added the microalgae to the water. After a few short weeks, the yet-to-be-explained happened.
“When we received the analysis from the state lab, it became evident that the algae did interact with the rare earth,” Hamilton-Brehm said. “We don’t know how. We don’t know why. We’re going to have to figure it out.”
SUSTAINABLE IMPACT
The algae did more than absorb the rare earth metals — its concentration more than doubled. The researchers made this discovery after separating the rare earth from the algae using a patented process that breaks down organic molecules.
“You’re getting your rare earths, but in addition you’re left with dissolved algae,” Hamilton-Brehm said. “This can be used for bio-stimulants, which are agricultural additives that support plant growth. Or you can extract the lipids out of it and make biodiesel. Now you’re talking about a sustainable process that could be profitable at the industrial level.”
On top of this, using algae to refine the rare earth metals is more environmentally friendly than the current standard, noted the professor, where chemicals such as sulfuric acid are used to dissolve the minerals around the rare earth elements.
Another benefit is that rare earth elements are often found in coal slag and electronic waste. This new algae process could clean the environment while extracting rare earth elements.
NEXT STEPS
Next steps include conducting additional experiments with different types of algae to determine whether they affect rare earth concentration levels. Hamilton-Brehm and Hummer are preparing a proposal to the National Science Foundation for grant funding to support this lab work.
Hummer believes discoveries like this are possible when departments across campus work together.
“I think these interdisciplinary projects are incredibly valuable. While they do happen on campus, I think that they should happen more. It exposes students to new topics and career options, and it leads to more creative thinking and collaboration among faculty,” he concluded.
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