Carbon capture will play a central role in helping the nations of the world manage and reduce their greenhouse gas emissions. Many materials are being tested for the purpose of capturing carbon dioxide. But now researchers led by the Norwegian Univ. of Science and Technology (NTNU) have found that ordinary clay can work just as effectively as more advanced materials.
“It is quite remarkable that clay can capture as much carbon dioxide as other materials that are being investigated,” says Jon Otto Fossum, professor at NTNU’s Dept. of Physics.
Clay offers many benefits compared to other materials, particularly because other potential materials can be expensive, difficult to produce, toxic and not particularly environmentally friendly.
A possible practical future use of this discovery could be to include clays in carbon dioxide filters for industrial-scale carbon dioxide emissions reduction.
“What we are doing is basic research,” Fossum says. “It will take more research to develop the technology, so we don’t expect clay-based carbon capture to be readily available anytime soon.”
The results are published in Scientific Reports.
Selective, reusable and inexpensive
A good material for capturing carbon dioxide must meet specific requirements. It should have a large surface area and good adsorption capability. It should be able to capture carbon dioxide selectively before it captures other molecules, it should not need a lot of energy for it to work, and it must be reusable. Moreover, it must be inexpensive and environmentally friendly.
Certain clay minerals meet these criteria, particularly smectite, a group of clay minerals that swell in contact with water, which are known as layered nanosilicates.
The researchers used synthetic smectite in their experiments. Artificial clays can actually be inexpensive to make.
Clay surface actively captures carbon dioxide
The researchers found that carbon dioxide in gaseous form binds to smectite, and that it is not only the smectite clay surfaces in themselves that are responsible for binding carbon dioxide, but principally that ions associated with the clay surfaces are the active capturers.
A smectite clay called lithium-fluorohectorite can retain carbon dioxide at temperatures up to 35 C at ambient pressure. The carbon dioxide that is captured by the clay is released when it is heated to temperatures above this limit, which allows carbon capture to be controlled.
“Our experiments show that this kind of smectite can capture and retain as much carbon dioxide as other materials that have been studied for this purpose,” Fossum says.
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