In one proposed method of carbon capture, magnesium oxide crystals on the ground bind to carbon dioxide molecules in the surrounding air, triggering the formation of magnesium carbonate. The magnesium carbonate is then heated to convert it back to magnesium oxide and release the carbon dioxide for placement underground or sequestration. Credit: Adam Malin/ORNL, US Department of Energy. Oak Ridge National Laboratory
Magnesium oxide is a promising material for capturing carbon dioxide directly from the atmosphere and injecting it deep down to limit the effects of climate change. But making the method economical will require discovering how quickly carbon dioxide is absorbed and how environmental conditions affect the chemical reactions involved.
Scientists at the Department of Energy’s Oak Ridge National Laboratory analyzed one set of samples of magnesium oxide crystals exposed to the atmosphere for decades, and another for days or even months, to assess reaction rates. They found that carbon dioxide is absorbed more slowly over longer periods of time due to a reaction layer that forms on the surface of the magnesium oxide crystals.
The results are published in the journal Environmental science and technology.
“This reacted layer is a complex mixture of different solids, which limits the ability of carbon dioxide molecules to find fresh magnesium oxide to react with. To make this technology economical, we are now looking at ways to overcome this shielding effect,” ORNL said. Juliane Weber, principal investigator of the project.
ORNL scientist Andrew Stack, a member of the project team, said: “If we can do it, this process could help achieve the Carbon Negative Energy Earthshot goal of capturing multi-gigaton levels. of carbon dioxide in the air for less than $100 per year. metric ton of carbon dioxide.
Most previous research aimed at understanding the rate at which the chemical reactions of magnesium oxide and carbon dioxide occur has relied on rough calculations rather than testing of materials. The ORNL study marks the first time a multi-decade test has been performed to determine reaction speed over long time scales. Using transmission electron microscopy at ORNL’s Center for Nanophase Materials Science, or CNMS, the researchers found that a reacted layer formed. This layer consists of a variety of complex crystalline and amorphous hydrated and carbonate phases.
“Additionally, by performing computer simulations of reactive transport modeling, we determined that as the reacted layer builds up, it becomes increasingly better at blocking carbon dioxide from finding fresh magnesium oxide. to react with,” said ORNL researcher Vitaliy Starchenko. “So, in the future, we are investigating ways to bypass this process to allow carbon dioxide to find a new surface to react with.”
Computer simulations help scientists and engineers understand how the reacted layer evolves and changes the way substances pass through it over time. Computer models are used to predict the reactions and movement of materials in natural and artificial systems, such as materials science and geochemistry.
More information:
Juliane Weber et al, Shielding MgO with a passivation layer prevents CO2 from being directly captured in the air, Environmental science and technology (2023). DOI: 10.1021/acs.est.3c04690
Provided by Oak Ridge National Laboratory
Quote: Proven magnesium oxide: unveiling the dynamics of CO₂ absorption (December 7, 2023) retrieved on December 7, 2023 from
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