Asian Scientist Magazine (Jun. 17, 2022) — Global greenhouse emissions have been on the rise. Recently, the International Energy Agency reported that the global carbon dioxide emissions have increased up to 36.3 billion tons in 2021 from 33 billion tons in 2019. With rising emissions causing temperatures to increase, many mitigation steps are currently in place to either reduce the emissions or capture and remove greenhouse gases from the environment. Researchers in Japan claim to have developed a faster carbon capture system that removes carbon dioxide directly from the air.
In a study published on ACS Environmental Au, principal investigator Dr Seiji Yamazoe and his team from Tokyo Metropolitan University synthesize and test multiple chemicals to absorb carbon dioxide using a system called Direct Air Capture (DAC).
Capturing carbon dioxide from the air is as difficult as it sounds. There is approximately 400ppm carbon dioxide in ambient air – which is 0.04% of total air volume. To separate such a small amount of carbon dioxide, a very potent liquid chemical medium is needed to isolate carbon dioxide from the air before it is separated using high heat.
Using such chemicals and generating the required energy for the system to function creates a high cost, with most DAC systems requiring around $600 to capture one ton of carbon dioxide. Also, most DAC systems are not efficient. The chemicals used to capture carbon dioxide from the air lose their efficiency as the reaction continues for an extended period of time.
Yamazoe’s team tackled this challenge by developing a solid-liquid phase separation system. Rather than extracting carbon dioxide from the air as a liquid or gas, the liquid chemicals used in the medium react with the carbon dioxide and produce insoluble crystals. These crystals are separated from the liquid medium and subsequently heated to slowly release carbon dioxide gas. The carbon dioxide gas can then be stored elsewhere.
The researchers optimized the solid-liquid phase separation system by finding a chemical medium that is efficient in capturing and releasing carbon dioxide. They synthesized multiple different chemicals and measured the rate of insoluble crystal formation over 10 hours as well as the final amount of crystals formed. One of the chemicals they tested, called isophorone diamine (IPDA), could convert almost 99% of the carbon dioxide from ambient air at twice the rate of other conventional chemical medias used in most DAC systems.
Subsequent tests with IPDA also revealed that the resulting crystals completely release carbon dioxide gas by gently heating at 60 degrees Celsius. Not only was this temperature much lower compared to what is used in current DAC systems, the IPDA was fully recoverable – the IPDA could be reused immediately for another reaction.
With this discovery, Yamazoe and team hope that this system could be scaled up and used for efficient removal of excessive carbon dioxide from the air. This could one day form part of the world’s arsenal to reach a net-zero carbon future.
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Source: Tokyo Metropolitan University; Photo: Unsplash
The article can be found at Kikkawa et al. (2022), Direct Air Capture of CO2 Using a Liquid Amine–Solid Carbamic Acid Phase-Separation System Using Diamines Bearing an Aminocyclohexyl Group.
