"Dilute separation processes are the most challenging separations to perform for two key reasons. First, due to the low concentration, the kinetics (speed) of chemical reactions targeting the removal of the dilute component are very slow. Second, concentrating the dilute component requires a lot of energy," explained Prof Ian Metcalfe, Royal Academy of Engineering Chair in Emerging Technologies in the School of Engineering, Newcastle University, UK, and lead investigator.
To address these challenges, researchers at Newcastle University, along with colleagues from Victoria University of Wellington, Imperial College London, Oxford University, Strathclyde University, and UCL, developed a novel membrane process. This membrane uses natural humidity differences to pump carbon dioxide from the air, solving the energy challenge, while the presence of water accelerates carbon dioxide transport through the membrane, addressing the kinetic challenge.
Dr Greg A. Mutch, Royal Academy of Engineering Fellow in the School of Engineering, Newcastle University, UK, stated, "Direct air capture will be a key component of the energy system of the future. It will be needed to capture the emissions from mobile, distributed sources of carbon dioxide that cannot easily be decarbonised in other ways."
"In our work, we demonstrate the first synthetic membrane capable of capturing carbon dioxide from air and increasing its concentration without a traditional energy input like heat or pressure. I think a helpful analogy might be a water wheel on a flour mill. Whereas a mill uses the downhill transport of water to drive milling, we use it to pump carbon dioxide out of the air," added Dr. Mutch.
Separation processes are crucial for modern life, affecting everything from the food we eat to the medicines we take and the fuels we use. They also play a vital role in reducing waste and supporting environmental remediation, such as direct air capture of carbon dioxide. As we move towards a circular economy, separation processes will become even more important. Direct air capture could provide carbon dioxide as a feedstock for producing hydrocarbon products in a carbon-neutral or carbon-negative cycle. Achieving climate targets, like the 1.5 C goal set by the Paris Agreement, requires direct air capture alongside transitioning to renewable energy and traditional carbon capture from sources like power plants.
Dr Evangelos Papaioannou, Senior Lecturer in the School of Engineering, Newcastle University, UK, described the innovative membrane, "In a departure from typical membrane operation, and as described in the research paper, the team tested a new carbon dioxide-permeable membrane with a variety of humidity differences applied across it. When the humidity was higher on the output side of the membrane, the membrane spontaneously pumped carbon dioxide into that output stream."
With the help of X-ray micro-computed tomography conducted with collaborators at UCL and the University of Oxford, the team precisely characterized the membrane's structure, allowing robust performance comparisons with other state-of-the-art membranes.
A significant aspect of the research was modeling the processes occurring in the membrane at the molecular scale. Using density-functional-theory calculations, the team identified 'carriers' within the membrane that uniquely transport both carbon dioxide and water. Water is needed to release carbon dioxide from the membrane, and carbon dioxide is needed to release water, allowing the energy from a humidity difference to drive carbon dioxide through the membrane from a low to a higher concentration.
"This was a real team effort over several years. We are very grateful for the contributions from our collaborators, and for the support from the Royal Academy of Engineering and the Engineering and Physical Sciences Research Council," said Prof Metcalfe.
Research Report:Separation and concentration of CO2 from air using a humidity-driven molten-carbonate membrane
Related Links
Newcastle University
Carbon Worlds - where graphite, diamond, amorphous, fullerenes meet
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
