In Faits et croyances (1840), French novelist Victor Hugo said “Chance talks, genius listens.” It is an enlightened wisdom that prompts scientists to explore both the facts of a study and its unpredictable data. It was a small unforeseen event that occurred in a laboratory during a chemistry experiment that initiated the research presented in this article.
Researchers from the Oak Ridge National Laboratory (ONRL) Energy Department found a very simple solution to capture carbon dioxide in the air. Initial experiments focused on purifying water by removing the following contaminants: sulfate, chromate and phosphate. To destroy these negatively charged ions, researchers synthesized a component called guanidine. Guanidine binds strongly to contaminants and forms insoluble crystals that can easily be extracted from water. During the experiment, they accidentally discovered a method of removing carbon dioxide from the air that requires very little energy and few chemicals. Their study, entitled “CO2 Capture from Ambient Air by Crystallization with a Guanidine Sorbent”, was published in the scientific journal Angewandte Chemie International Edition, on December 21, 2016.
Circumstances Leading to Serendipity
Research engineer in crystallography, and specialist in chemical extraction and separation processes, Radu Custelcean, noted that they were concerned by an accidental chemical phenomenon of crystallization. This occurred when an aqueous solution of guanidine was left unintentionally in the open air. While analyzing the crystals that formed on the solution’s surface using a technique called X-ray diffractometry, the team noticed the presence of the carbonate ion. This is a salt that forms when carbon dioxide comes into contact with water. Following this discovery, researchers Michelle Kidder, Radu Custelcean, Charles Seipp and Neil Williams began a study on greenhouse gas reduction by crystallization using guanidine. The research was funded by the Office of Science of the U.S. Department of Energy.
Industrial Outlook for Carbon Dioxide Capture Using Guanidine
Industrial scale carbon dioxide capture and storage processes (particularly for power generation industries) being used currently are technically able to limit the environmental impact of gas emissions. However, additional costs of the industrial equipment needed, and the energy used for residue capture transport and storage, can sometimes reach 70% and can be a deterrent for organizations.
We note, for example, that they are stored in large quantities deep in geological formations. Drilling and injection technologies similar to those used for oil extraction are applied. It is critical that the storage site layers be perfectly leak tight, as the extracted carbon dioxide is transformed into gas or liquid form and may effectively seep through the upper layers.
Custelcean also emphasizes that carbon dioxide conversion prior to transport must be heated up to 900 degrees Celsius (1.652 ºF), a process that often emits more carbon dioxide than that initially removed.
The guanidine-based compound developed by ORNL offers a more effective alternative. In order to release the bound carbon dioxide, the crystals are heated to between 80 and 120 degrees Celsius (176-248 ºF). In fact, this process consumes less energy than current methods. The temperature needed to release carbon dioxide also makes the use of solar power possible, rendering the capture and transformation processes eco-responsible.
According to Custelcean, the guanidine capture process needs to be developed and improved before industrial implementation. To this end, the team is currently studying the crystal structure and spallation of guanidine using a technique known as neutron diffractometry. By analyzing the carbonate bond in the crystals, the researchers hope to understand the molecular mechanism of the carbon dioxide capture process in order to ensure the design optimisation of sorption agents.