Description du sujet de thèse

Aqueous foams are easily obtained by mixing a few surfactant molecules, a little liquid and a lot of gas. These are self-organizing, multi-scale systems in which the liquid is distributed between films, Plateau edges and nodes, which lie respectively at the intersection of two, three and four bubbles. Foams are characterized by low density, unusual rheological properties and high specific surface area, which is notably used in the foam flotation process for separating hydrophobic and hydrophilic materials suspended in a liquid [Can, Stev]. The relevance of developing a similar process for gas mixtures, which would enable two gases of different chemical nature to be separated, one remaining in the bubble while the other is solubilized in the liquid aqueous phase, has never been successfully quantified, despite some promising work [Wat, Jan] and the urgency of atmospheric CO2 reduction targets to limit climate disruption.
In this context, the aim of this thesis is to study the potential of aqueous foams loaded with microalgae to separate CO2 from other atmospheric gases and convert it into biomass within the foam. The study geometry selected combines i) the high specific surface area of foams, which ensures separation of CO2 from other gases, and ii) the ability of microalgae to convert CO2 into biomass via photosynthesis. The study geometry allows counter-flow of the two inputs required for photosynthesis, with CO2 supplied by the bubbles, while the various nutrients are supplied via the flow of the liquid phase.
This subject raises several questions. Firstly, we need to quantify the photosynthetic activity of microalgae in the various foam elements, particularly in soap films whose thickness is of the same order of magnitude as that of the algae. Next, we need to study how the microalgae distribute themselves in the different foam elements, so as to optimize the distribution of the liquid containing the nutrients. Finally, we need to quantify the efficiency of the process in terms of capturing and converting CO2 into biomass. To answer these questions, we propose a multi-scale study based on a single film and an assembly of films, organized in 2D or 3D (aqueous foam). These studies will be carried out experimentally using the functionalities offered by microfluidics, as well as on a larger scale using a dedicated cell recently developed at LIPhy for measuring and controlling the CO2 concentration of a gaseous atmosphere and its humidity. The results will be analyzed via scaling law approaches, model development or numerical simulation (COMSOL type) in collaboration with theoreticians.


[Can] Cantat et al., Foams Structure and dynamics, Oxford University Press.
[Stev] Stevenson Foam Engineering: fundamentals and applications, Wiley & Sons (2012)
[Wat] Watsona et al. Carbon dioxide capture using Escherichia coli expressing carbonic anhydrase in a foam bioreactor Env. Tec. 37, 3186 (2016).
[Jan] Janoska et al. A liquid foam-bed photobioreactor for microalgae production Chem. Eng. J. 313, 1206 (2017)

Contexte de travail

By replacing a thermal gas separation process with a membrane process, it is expected that the energy consumption associated with this separation can be reduced by a factor of up to 10. Our aim is to investigate the potential of flowing aqueous liquid films as membranes for filtration and CO2 conversion. To increase the films' storage capacity and ensure CO2 conversion, we aim to functionalize the films by seeding them with microalgae with a high affinity for the gas to be filtered, in which case the filtrate can be easily transported to its place of storage or use.

This interdisciplinary project will be supervised by Gwennou Coupier and Elise Lorenceau at LIPhy, in collaboration with researchers at LCPV, as part of an ANR project funded in 2024. LIPhy is a laboratory of Grenoble Alpes University, whose campus is considered one of the most beautiful in Europe. The student will be in charge of all aspects of the project: experimental set-up, data measurement and analysis, discussion, synthesis and writing of articles, with the aim of making him or her fully autonomous and the leader of the research project. To help the student in this task, a follow-up meeting between the student and the researchers will take place every week at a regular time. This meeting will provide an opportunity to discuss the progress of work over the past week, as well as to determine the work program for the week ahead. A meeting will be held with all ANR consortium members every two months. In addition, informal interactions and joint work sessions (particularly for setting up experiments) will take place according to the student's needs. The student will also benefit from the tutoring system in place at LIPhy, and an assessment of progress made by an individual thesis monitoring committee in accordance with the rules of the doctoral school (CIST).

We are looking for a student with an interest in fluid mechanics, hydrodynamics and soft matter experiments, as well as a solid background in physics or physical chemistry or fluid mechanics. Good presentation and interaction skills are also expected, as the project will involve numerous collaborations, particularly with biologists.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.