Scientists create a mineral in the lab that captures carbon dioxide [View all]

[sandensea]

Scientists are one step closer to a long-sought way to store carbon dioxide in rocks.

A new technique speeds up the formation of a mineral called magnesite that, in nature, captures and stores large amounts of the greenhouse gas CO². And the process can be done at room temperature in the lab, researchers reported August 14 at the Goldschmidt geochemistry conference, held in Boston.

If the mineral can be produced in large quantities, the method could one day help fight climate change.

“A lot of carbon on Earth is already stored within carbonate minerals, such as limestone,” says environmental geoscientist Ian Power of Trent University in Canada, who presented the research. “Earth knows how to store carbon naturally and does this over geologic time. But we’re emitting so much CO² now that Earth can’t keep up.”

Researchers have been seeking ways to boost the planet’s capacity for CO² storage. One possible technique: Sequester the CO² gas by converting it to carbonate minerals.

Magnesite, or magnesium carbonate, is a stable mineral that can hold a lot of CO² naturally: A metric ton of magnesite can contain about half a metric ton of the greenhouse gas.

But magnesite isn’t quick to make — at least, not at Earth’s surface.

Another option is to try to make magnesite in the laboratory — but at room temperature, that can take a very long time.

Under very high temperatures, scientists can quickly create magnesite in the lab, using olivine as a feedstock. But that process uses a lot of energy, Power says, and could be very costly.

The problem with making magnesite quickly, Power’s team found, is that water gets in the way. “It’s difficult to strip away those water molecules,” Power says. “That’s one of the reasons why magnesite forms very slowly.”

To get around this problem, Power and his colleagues used thousands of tiny polystyrene microspheres, each about 20 micrometers in diameter, as catalysts to speed up the reaction. The microspheres were coated with carboxyl, molecules with a negative charge that can pull the water molecules away from the magnesium, freeing it up to bond with the carbonate ions.

Thanks to these microspheres, Power says, the researchers managed to make magnesite in just about 72 days. Theoretically, he adds, the microspheres would also be reusable, as the spheres weren’t used up by the experiments.

That result doesn’t mean the technique is ready for prime time, Power says. So far, the scientists have made only a very small amount of magnesite in the lab — about a microgram or so. “We’re very far away from upscaling,” or making the technology commercially viable.

At: https://www.sciencenews.org/article/lab-mineral-magnesite-captures-carbon-dioxide

A Magnesite mine in China. Can manufacturing the highly absorbent mineral help slow climate change?