234 Electrolysis of regolith for simultaneous oxygen and metal production

Job title:

234 Electrolysis of regolith for simultaneous oxygen and metal production

Company:

Centre National d’Etudes Spatiales

Job description

25-234 Electrolysis of regolith for simultaneous oxygen and metal productionPostuler25-234 Electrolysis of regolith for simultaneous oxygen and metal production

• Doctorat, 36 mois
• Temps plein
• Indifférent
• Maitrise, IEP, IUP, Bac+4
• Materials and processes

PostulerMissionWorldwide, spatial agencies agree that future missions of exploration on the Moon will require longer stay for activities on the lunar surface than in Apollo missions, implying for these long-duration missions to settle down with permanent lunar bases to sustain technical and scientific activities, with the perspective of as human settlement on Mars. In this context, incorporation of In-Situ Resources Utilization (ISRU) to produce life support consumables and everyday life objects will greatly reduce the mass, the cost and the risk of missions and will lead to expand the human being exploration efforts on the Moon. The ISRU concept considers the resources at the exploration site with the use of lunar regolith (rocks, soils) as a raw material, with the following objectives: extraction of breathing oxygen, – water production and – formation of metals (as feedstocks for in-situ manufacturing).In the current project, our objective is to propose an autonomous electrochemical process to be implemented on Moon sites selected for regolith presence to simultaneously produce metals and oxygen.The consortium has been working together since mid- 2018 with two master’s degree students in Chemical Engineering, supervised by LGC and IRAP. Our effective collaboration was granted by STAE (Fondation Sciences et Technologies pour l’Aéronautique et l’Espace), which supports emerging and challenging issues with the intrinsic need of multi scientific domain collaboration. A thesis scholarship was also obtained and recently defended (Maarten MAES-2024-Université of Toulouse).The process proposed is the electrochemical conversion of regolith into O2 and metals. It is based on regolith dissolution in a LiF-NaF molten fluoride solvent at 800°C, leading to metallic cations and oxide anions, which were then reduced into metal and oxidised into O2 respectively by electrolysis. A basalt-type rock from the Pic d’Ysson site, called Basalt Pic d’Ysson Naturel (BPY-N), was used as an analogue of lunar regolith. It was demonstrated that all metallic elements composing BPY-N were soluble (ICP-AES measurements). Using electrochemical techniques, the production of different metals or alloys was proved (SEM-EDS measurements), whose composition depends on the electrolysis conditions and substrate. Finally, oxygen gas was produced without the electrode degradation and quantified (gaseous oxygen analyser). Optimization of the electrolysis operating conditions leads to a faradic yield of more than 70%. One more interesting result comes from the comparison of the results obtained with BPY-N and a mixture of powders of identical chemical composition: the same behaviour was observed, meaning that the crystalline nature of the lunar regolith simulant does not have a significant impact on the process, opening the possibility of reproducing lunar soil of desired composition by simply mixing oxide powders.We now consider building upon these quite promising results and the proposed scientific program focuses on how to improve the process in term of sustainability, long-term duration experiment and production unit size.First of all, any decrease of the temperature will limit the structure corrosion and the energetic consumption. To achieve that, other alkaline and alkaline earth fluoride mixtures will be tested (e.g. LiF NaF KF melting point 462°C) with the ultimate goal of reaching a temperature around 450°C. A full evaluation in terms of metal deposition composition and oxygen production yield will be done, the experimental apparatus being already in-house. Then, the process will be assessed to precisely quantify the produced oxygen and energy use.Another important aspect in terms of process control is the start-up phase. In our current process, O2 is extracted with Ar carrier gas, meaning that an Ar/O2 separation is needed afterwards: this is difficult to envisage on the Moon. Indeed, experiments in lunar environment are expected to be run under vacuum without Ar. The influence of the pressure on the solvent behaviour and the reaction yields has thus to be studied, as well as the pure O2 extraction.The process dimensioning is also important to estimate the electrode surface area, the salt volume and thus the global volume of the process: our target is to produce enough oxygen gas for 8 days and 4 astronauts. From these results, a O2 production strategy will be adopted, in terms of number of production units needed.Coupled with the dimensioning, a sustainable process is also targeted, with the re-use of the solvent and the electrodes. Long-term duration experiments (with a scale 1 timespan) are thus essential to quantify the production yields, the corrosion effect and the global energy consumption of the process.Industrial fallbacks are not to be neglected as this study will also lead to fundamental and experimental results that are to be of valuable use on Earth in the ongoing industrial processes using a molten solvent (Al, Zr, U…).For more Information about the topics and the co-financial partner (found by the lab !); contact Directeur de thèse –Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online before March 14th, 2025 Midnight Paris time !

Expected salary

Location

Toulouse

Job date

Wed, 05 Feb 2025 00:01:26 GMT

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