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CO2 capture by a blood foam

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In order to limit global warming, several IPCC scenarios are based on an intensive capture of CO2 from the atmosphere to reduce the greenhouse effect induced by it. This is a technically ambitious objective since it will require the development of processes that will allow the separation of CO2 from other gases in the atmosphere and its concentration in order to limit storage volumes. The respiratory system of living beings is however capable of such a challenge since it is able to capture oxygen from the air and concentrate it in the blood.

Several factors contribute to this efficiency: in mammals, the enormous specific surface of the pulmonary alveoli allows the development of a large exchange surface between the liquid and the blood. Secondly, the alternation of the inspiration and expiration cycles allows a mixing of the gas in the atmosphere, which limits the concentration polarizations and finally the selectivity of the red blood cells for oxygen allows to shift the solubility equilibrium of this gas in the plasma in order to concentrate it in the liquid phase. Finally, the hydrodynamic flexibility of the arterial system allows to convey these red blood cells loaded with oxygen to the muscles where it will be consumed.

The objective of this internship is to realize a prototype allowing to capture and concentrate CO2, inspired by the one realized by the respiratory system of the living beings for oxygen. For this, we propose to use aqueous foams. As for the respiratory systems, they present a very large surface of liquid/gas exchange and can be dynamically solicited to mix the gas. Moreover, if the liquid phase is loaded with red blood cells, solubility equilibria can be shifted and red blood cells transported through the foam’s microchannel network to be concentrated.

Figure 1 : On the left, an elementary foam cell fed with foamy liquid loaded with red blood cells at the flow rate Qi will be inserted in a hermetic box (in black). The CO2 content in the chamber as well as in the outgoing liquid will be measured. On the right, a gas flowed at a rate Qg, into blood will produce bubbles, which form a column of foam with a stationary height. This column will be sparged with foaming solution loaded with red blood cells at a flow rate Qi. The CO2 content in the chamber will also be measured.

To test this idea, we propose to realize elementary foam geometries consisting of an assembly of films connected by liquid microchannels (see Fig. 1 left). First, we propose to study experimentally how the liquid distributes between the films and the microchannels. The thickness of the films will be measured by UV-Vis spectroscopy and the flow rate of the red blood cells by dynamic tracking of the red blood cells in the films. Then, we will study the gas transfer between these structures and the atmosphere. For this, the foam geometries will be inserted in a hermetic box where the evolution of the CO2 content can be measured. In particular, we will correlate the amount of CO2 absorbed with the exchange surface of the system, the concentration of red blood cells and the flowing rate. Finally, a study at the scale of a foam will be proposed by bubbling an air/CO2 mixture of given concentration at a gas flow rate Qg in a foaming blood solution (see Fig. 1 right).
All results will be rationalized via advection-diffusion models in the microchannels and films of the foam.

This internship can be followed by a thesis funded by the region AURA.
Contacts : Elise Lorenceau
Gwennou Coupier
Benjamin Dollet