Scientists have created a new membrane technology to remove carbon dioxide (CO 2) more efficiently from mixed gases like power plant emissions.
Rich Spontak, coauthor of the paper, said that the new membranes could be demonstrated by examining mixtures of nitrogen dioxide and CO 2. This is because the CO 2/nitrogen dioxide combinations are especially relevant for reducing greenhouse gas emission from power plants. We have shown that membranes can be greatly improved to remove CO 2, while maintaining a high level of CO 2 permeability.
We also examined mixtures of CO 2 and methane. This is an important consideration for the natural gas industry,” Spontak says. He is a Distinguished Professor in Chemical and Biomolecular Engineering and Professor Materials Science & Engineering at North Carolina State University. These CO 2-filtering membranes are also suitable for any situation where CO 2 is needed to be removed from mixed gases, such as a biomedical application, or to clean CO 2 from the submarine’s air.
Membranes are attractive because they don’t take up much space and can be made in many sizes. They can also be replaced easily. Chemical absorption is another technology used to remove CO 2. This involves bubbling mixed gases through a column containing a liquidamine. Absorption technologies are more compact, and liquid amines can be toxic and corrosive.
These membrane filters allow CO 2 to pass through them faster than any other components of the mixed gas. The gas that exits the membrane from the other side has a higher percentage of CO 2 than that entering it. Capturing the gas leaving the membrane captures more CO 2 than any other constituent gases.
This trade-off between selectivity and permeability has been a problem for membranes like these. Higher permeability means that gas can be moved through the membrane more quickly. However, a higher permeability means that selectivity decreases. This means that other components, such as nitrogen, can pass through the membrane faster, reducing the ratio between CO 2 and other gases. Also, selectivity decreases which means that you capture less CO 2.
Researchers from the U.S., Norway and other countries addressed the problem by creating chemically active polymer chains that were both hydrophilic AND CO 2-philic on existing membranes. This improves CO 2 selectivity, and results in relatively low permeability.
“In short, we have demonstrated that with very little change in permeability we can increase selectivity up to about 150 times,” Marius Sandru, coauthor of the paper, and senior research scientist at SINTEF Industry in Norway, an independent research organisation. “So, we are capturing more CO 2 than the other species in gas mixtures.”
Cost is another challenge for membrane CO 2 filters. The cost of membrane COsub>2/sub> filters has been a challenge. They were more efficient than previous membrane technologies, but they were more costly.
Spontak says, “Because our goal was to create a technology that could be commercially viable,” Spontak says that the membranes were modified to increase selectivity. While this may increase the cost of the membranes, we believe that the modified membranes will still prove to be economically viable.
Sandru states that the next steps will be to determine if the techniques developed here can be applied to other polymers in order to achieve comparable or superior results. Also, to improve the nanofabrication process. Although the results have been quite exciting, we have not yet optimized this modification process. “Our paper presents proof-of-concept results.”
Researchers are also keen to explore other uses of the membrane technology, including whether it could be used in biomedical ventilators or aquaculture filtration devices.
Researchers say that they are open to collaboration with industry partners to explore any of these opportunities or questions to mitigate global climate change and improve the function of devices.