New polymer membrane tech improves efficiency of CO2 capture

Date:
April 1, 2022
Source:
North Carolina State University
Summary:
Researchers have developed a new membrane technology that allows
for more efficient removal of carbon dioxide (CO2) from mixed gases,
such as emissions from power plants.



FULL STORY ========================================================================== Researchers have developed a new membrane technology that allows for
more efficient removal of carbon dioxide (CO2) from mixed gases, such
as emissions from power plants.


==========================================================================
"To demonstrate the capability of our new membranes, we looked at
mixtures of CO2 and nitrogen, because CO2/nitrogen dioxide mixtures
are particularly relevant in the context of reducing greenhouse gas
emissions from power plants," says Rich Spontak, co-corresponding author
of a paper on the work.

"And we've demonstrated that we can vastly 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," says Spontak, who is a Distinguished Professor of Chemical and Biomolecular Engineering and Professor of Materials Science & Engineering at North Carolina State University. "In addition, these CO2- filtering membranes can be used in any situation in which one needs to
remove CO2 from mixed gases -- whether it's a biomedical application or scrubbing 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 made in a wide variety of sizes, and
they can be easily replaced. The other technology that is often used for
CO2 removal is chemical absorption, which involves bubbling mixed gases
through a column that contains a liquid amine -- which removes CO2 from
the gas. However, absorption technologies 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
more quickly than the other constituents in the mixed gas. As a result,
the gas passing out the other side of the membrane has a higher proportion
of CO2 than the gas entering the membrane. By capturing the gas passing
out of the membrane, you capture more of the CO2 than you do of the
other constituent gases.

A longstanding challenge for such membranes has been a trade-off between permeability and selectivity. The higher the permeability, the more
quickly you can move gas through the membrane. But when permeability goes
up, selectivity goes down -- meaning that nitrogen, or other constituents,
also pass through the membrane quickly -- reducing the ratio of CO2 to
other gases in the mixture. In other words, when selectivity goes down
you capture relatively less CO2.



==========================================================================
The research team, from the U.S. and Norway, addressed 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've demonstrated
that we can increase selectivity by as much as about 150 times," says
Marius Sandru, co- corresponding author of the paper and senior research scientist at SINTEF Industry, an independent research organization in
Norway. "So we're capturing much more CO2, relative to the other species
in gas mixtures." Another challenge facing membrane CO2 filters has
been cost. The more effective previous membrane technologies were,
the more expensive they tended to be.

"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 engineered the surface of these membranes to improve selectivity. And while this does increase the cost, we think the modified membranes will still be cost effective." "Our next steps are to
see the extent to which the techniques we developed here could be applied
to other polymers to get comparable, or even superior, results; and to
upscale the nanofabrication process," Sandru says. "Honestly, even though
the results here have been nothing short of exciting, we haven't tried
to optimize this modification process yet. Our paper reports proof-of-
concept results." The 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
in exploring any of these questions or opportunities to help mitigate
global climate change and improve device function.

The paper is published in the journal Science. The paper was co-authored
by Wade Ingram, a former Ph.D. student at NC State; Eugenia Sandru and
Per Stenstad of SINTEF Industry; and Jing Deng and Liyuan Deng of the
Norwegian University of Science & Technology.

The work was done with support from the Research Council of Norway;
UEFSCDI Romania; the National Science Foundation, under grant number ECCS-2025064; and Kraton Corporation.


========================================================================== Story Source: Materials provided by
North_Carolina_State_University. Original written by Matt Shipman. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Marius Sandru, Eugenia M. Sandru, Wade F. Ingram, Jing Deng, Per M.

Stenstad, Liyuan Deng, Richard J. Spontak. An integrated
materials approach to ultrapermeable and ultraselective CO 2
polymer membranes.

Science, 2022; 376 (6588): 90 DOI: 10.1126/science.abj9351 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220401122134.htm

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