ENVIRONMENT

ORNL discovers new method to remove carbon from air

Andrew Capps

Knoxville News Sentinel

Using X-ray diffraction, ORNL’s Radu Custelcean analyzed the molecular structure of the simple guanidine compound and was surprised to find carbonate, a crystal that forms when carbon dioxide from air reacts with water.

Researchers at the Oak Ridge National Laboratory have discovered a new method for removing carbon dioxide from ambient air while conducting a study that was intended to help remove contaminants from water.

According to a news release by ORNL, the new method is simple and reliable. The discovery is being billed as a new option to capture and store carbon and help combat global warming.

Scientists at ORNL discovered the new method while trying to use a compound called guanidine to remove contaminants like sulfate, chromate and phosphate from water. Radu Custelcean, a research scientist at ORNL, said in a release that after exposing a solution containing the guanidine to air, researchers found crystals forming in the solution.

“After analyzing their structure by X-ray diffraction, we were surprised to find the crystals contained carbonate, which forms when carbon dioxide from air reacts with water,” Custelcean explained.

The new crystallization method differs from other carbon-capture methods in that it requires considerably less energy to release the carbon from the guanidine solution and transfer it into long-term storage and transportation pipelines.

“Through our process, we were able to release the bound carbon dioxide by heating the crystals at 80-120 degrees Celsius, which is relatively mild when compared with current methods,” Custelcean added.

The crystallization method compares favorably to traditional methods which require carbon capturing materials be heated to 900 degrees Celsius before the captured carbon can be released for transportation and storage. ORNL’s new guanidine-based method requires much less energy and allows the guanidine solution to be re-used as many as three times.

Custelcean added via phone that it would take a concerted government initiative for the new method to become a widespread practice.

“It really all depends on the policies and regulations because there would have to be a nationwide initiative and that requires funding,” he said. “It would have to be initiated by the government.”

ORNL’s Charles Seipp synthesized a simple compound known as guanidine that was found to bind strongly with carbon dioxide directly from the air and form insoluble carbonate crystals that are easily separated from water.

The new method’s potential to remove carbon from the air is strong Custelcean said, but he emphasized that the air is a shared resource and that removing and storing a large amount of carbon would take global cooperation.

“It would require a global effort,” he added. “If only one country were to tackle it, I think the magnitude would be too large.”

The crystals that were found in the guanidine solution are now being studied at ORNL’s Spallation Neutron Source in the hopes of better understanding the mechanism behind guanidine’s ability to absorb and release carbon dioxide.

The study detailing the experiment, titled “CO2 Capture from Ambient Air by Crystallization with a Guanidine Sorbent,” was published in the journal Angewandte Chemie International Edition and included Charles Seipp of the University of Texas at Austin, Neil Williams of the University of Tennessee, and Michelle Kidder and Radu Custelcean, all of whom also work for ORNL.

Funding for the project was provided by the Department of Energy’s Office of Science.