New thermodynamic and kinetic constraints on H2 production during ferroan brucite reaction at low temperature
- 1Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiffel, ISTerre, 38000 Grenoble, France (benjamin.malvoisin@gmail.com)
- 2Storengy (ENGIE), France
- 3Engie Research, ENGIE, France
The alteration of ferroan brucite, a common by-product of serpentinization, has been proposed as a H2 source at low temperature. Here, synthetic ferroan brucite with Fe/(Fe+Mg) = 0.2 was reacted with pure water at temperatures ranging from 348 to 573 K in 29 experiments either conducted in gold capsules or Ti-based reactors. H2 production monitoring with time and characterization of the reaction products revealed the occurrence of the following reaction: 3 Fe(OH)2brucite = Fe3O4 + H2 + 2 H2O. This reaction proceeds completely in ~ 2 months at 378 K and is thermally activated. The small grain size of the synthetic brucite (40-100 nm) is similar to observations in natural samples, and is probably responsible for the high reaction rate measured. H2 production reached a plateau and Fe-bearing brucite also precipitated as a reaction product, suggesting the achievement of equilibrium. The thermodynamic properties of Fe(OH)2 were refined based on the experimental dataset and differ by less than 5 % from previous estimates. However, ferroan brucite is predicted to be stable at an hydrogen activity one order of magnitude lower than previously calculated. As a result, significant H2 production during ferroan brucite alteration at low temperature requires efficient fluid renewal. Such a mechanism strongly differs from olivine serpentinization which can occur even at high activity in H2 and thus with limited water renewal.
How to cite: Malvoisin, B., Carlin, W., Brunet, F., Lanson, B., Findling, N., Lanson, M., Jeannin, L., Fargetton, T., and Lhote, O.: New thermodynamic and kinetic constraints on H2 production during ferroan brucite reaction at low temperature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20271, https://doi.org/10.5194/egusphere-egu24-20271, 2024.