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Dec. 10, 2018
Membranes – thin barriers that allow some things to pass through, but stop others – occur naturally in cells and tissues. Artificial membranes modeled after natural ones are used in a number of applications, including separating and removing carbon dioxide (CO2) from waste gases released in energy production.
An investigation on the International Space Station looks at whether making artificial membranes in microgravity can help reduce greenhouse gas emissions on Earth.
Image above: Cemsica calcium silicate nanoparticles, which have diameters as small as a few nanometers. Image Credits: Cemsica.
The Cemsica investigation uses particles of calcium-silicate to make membranes with openings or pores smaller than 100 nanometers, known as nanoporous membranes, to separate carbon dioxide molecules from air and other gases. These membranes are as thin as a human hair. Membranes already represent one of the most energy-efficient and cost-effective technologies for separating and removing CO2 from waste gases.
The investigation takes its name from Houston-based Cemsica, LLC, a company that is commercializing this gas separation membrane technology. “Our technology not only controls the shape and size of the membrane pores,” said Negar Rajabi, principal investigator and Cemsica founder and CEO. “It also creates an affinity to certain gases such as CO2, meaning those gases are drawn to the membrane.” That gives the membranes significantly greater separation capability.
Creating these membranes in microgravity may resolve current challenges in the technology, including high-cost and manufacturing difficulties, Rajabi added. Resolving those challenges could lead to development of lower-cost membranes with improved performance and stability, as well as improved manufacturing techniques.
Large gaps or separation of the calcium-silicate particles and substrate material adversely affect membrane performance. Microgravity minimizes these problems since calcium-silicate crystals grow larger and in more organized structures in space, creating organized, defect-free pores and higher surface area.
Image above: The rise of carbon dioxide in the atmosphere. In 2013, CO2 levels surpassed 400 ppm for the first time in recorded history. Image Credits: National Oceanic and Atmospheric Administration.
Surface area plays a key role in gas separation in microgravity, where separation occurs only through diffusion. The higher surface area remains a significant factor in improved gas separation even in Earth’s gravity because it creates higher surface tension that facilitates affinity-based gas separation.
This investigation was sponsored by the International Space Station U.S. National Laboratory. “Cemsica’s novel approach to gas separation membranes in microgravity conditions provides the energy community a new avenue for evaluating unique ways to reduce the effects of CO2 emissions on our planet,” said Patrick O’Neill with the National Lab. “The project also could reduce energy consumption while improving the chemical stability of products on Earth.”
Lessons learned from the investigation may enable Earth-based production of membranes that can separate and capture CO2 from fossil-fuel power plants using half the energy of current methods. Roughly 40 percent of CO2 emissions in the U.S. come from these power plants. Other potential applications include oil and gas production and water treatment.
These membrane pores may be tiny, but they have very big potential.
Related links:
Cemsica, LLC: http://www.cemsica.com/
International Space Station U.S. National Laboratory: http://www.iss-casis.org/
Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html
International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html
Images (mentioned), Text, Credits: NASA/Michael Johnson/JSC/International Space Station Program Science Office/Melissa Gaskill.
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