Researchers have developed a new membrane technology that enables more efficient removal of carbon dioxide (CO.)2) from mixed gases, such as emissions from power plants.
“To demonstrate the capacity of our new membranes, we looked at mixtures of CO2 and nitrogen, since CO2/ nitrogen dioxide mixtures are particularly relevant in reducing greenhouse gas emissions from power plants “, says Rich Spontak, co-author of an article on the work.” And we have shown that we can significantly improve the selectivity of membranes to remove CO2 while retaining relatively high CO2 permeability.”
“We also looked at mixtures of CO2 and methane, which is important to the natural gas industry, “said Spontak, a leading professor of chemical and biomolecular technology and professor of materials science and technology at North Carolina State University.2-filtration membrane can be used in all situations where CO needs to be removed2 from mixed gases – whether it is a biomedical application or scrubbing of CO2 from the air in a submarine. “
Membranes are an attractive technology for removing CO2 from mixed gases because they do not take up much physical space, they can be manufactured in a variety of sizes and they can be easily replaced. The second technology often used for CO2 removal is chemical absorption, which means that mixed gases are bubbled through a column containing a liquid amine – which removes CO2 from the gas. However, absorption techniques have a significantly larger footprint, and liquid amines tend to be toxic and corrosive.
These membrane filters work by allowing CO2 to pass through the membrane faster than the other constituents of the mixed gas. As a result, the gas passing out on the other side of the membrane has a higher proportion of CO2 than the gas entering the membrane. By capturing the gas that passes out of the membrane, you capture more of the CO2 than you do with the other gases.
A long-standing challenge for such membranes has been a trade-off between permeability and selectivity. The higher the permeability, the faster you can pass gas through the membrane. But when the permeability goes up, the selectivity decreases – which means that nitrogen or other constituents also pass through the membrane quickly – which reduces the ratio of CO2 to other gases in the mixture. In other words, when selectivity drops, you capture relatively less CO2.
The research team, from the USA and Norway, solved this problem by growing chemically active polymer chains that are both hydrophilic and CO2-philic on the surface of existing membranes. This increases CO2 selectivity and causes relatively little reduction in permeability.
“In short, with little change in permeability, we have shown that we can increase selectivity by as much as about 150 times,” says Marius Sandru, co-author of the article and senior researcher at SINTEF Industry, an independent research organization in Norway. “So we capture a lot more CO2in relation to the other species in gas mixtures. “
Another challenge for membrane CO2 filters have cost. The more efficient previous membrane technologies were, the more expensive they tended to become.
“Because we wanted to create a technology that is commercially viable, our technology started with membranes that are already in widespread use,” says Spontak. “We then designed the surface of these membranes to improve selectivity. And even if this increases the cost, we believe that the modified membranes will still be cost-effective.”
“Our next steps are to see the extent to which the technologies we have developed here can be applied to other polymers to achieve comparable, or even superior, results; and to scale up the nanomaterials process,” says Sandru. “Honestly, although the results here have been nothing short of exciting, we have not tried to optimize this modification process yet. Our paper reports proof-of-concept results.”
Researchers are also interested in exploring other applications, such as whether the new membrane technology could be used in biomedical ventilator devices or filtration devices in the aquaculture sector.
The researchers say they are open to working with industry partners to explore any of these issues or opportunities to help mitigate global climate change and improve the unit’s functioning.
The essay is published in the journal Science. The essay was co-authored by Wade Ingram, a former Ph.D. student at NC State; Eugenia Sandru and Per Stenstad from SINTEF Industri; and Jing Deng and Liyuan Deng from the Norwegian University of Science and Technology.
The work was done with support from the Research Council of Norway; UEFSCDI Romania; National Science Foundation, under grant number ECCS-2025064; and Kraton Corporation.