A team of chemical engineers at MIT have come up with a way to continuously remove carbon dioxide from a stream of gas, it could even be applied to the air we breathe. In their work, the key component is a membrane that can be switched on and off by electrochemical assistance. There are no moving parts involved in the process and it uses relatively little energy.
The membranes are made of anodized aluminum oxide, they are hexagonal — like a honeycomb — and allow gas molecules to permeate in and out when open. Their work is published in the latest issue of Science Advances journal.
While it has a possible application on the ambient air around us, this "gas gating" technique could also be applied to industrial exhaust systems too.
The device utilizes a redox-active carbon-adsorbent material. This material is sandwiched between two switchable gas gating membranes. The sorbent (adsorbing material) and the gating membranes are in close proximity with each other and immersed in an organic electrolyte to provide zinc ions a medium to shuttle to and fro.
Two gating membranes we've mentioned are switched on and off via a switch that controls the voltage polarity. When the switch is flicked, zinc ions shuttle to the other side. So the ions block one side by forming a film of metal over it while opening the other side, dissolving the film of metal on that side.
When the sorbent layer is open for business, the material soaks in carbon dioxide until it reaches maximum saturation. Then, when we switch the polarity a concentrated stream of almost pure carbon dioxide is released. Setting up a system with this contraption which alternates half the sections to be on at all times could make it into a continuous filtering device.
In an interview with the MIT News, Alan Hatton, Professor and Director at David H. Koch School of Chemical Engineering Practice, said “That means that you have a feed stream coming into the system at one end and the product stream leaving from the other in an ostensibly continuous operation."
The device also utilizes a very minuscule amount of materials according to Yayuan Liu, a Postdoc Associate at MIT Chemical Engineering Department. She remarks another significant advantage: It doesn't require energy to actually operate, it just needs a small amount of electricity to switch states.
Such systems could be made into a system to drive down greenhouse gas emissions in factory/manufacturer settings. It could even potentially filter out ambient air in places with low air quality.