JpGU-AGU Joint Meeting 2020

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-GC Geochemistry

[S-GC49] Solid Earth Geochemistry, Cosmochemistry

convener:Gen Shimoda(Geological Survey of Japan, AIST), Katsuhiko Suzuki(Submarine Resources Research Center, Japan Agency for Marine-Earth Science and Technology), Katsuyuki Yamashita(Graduate School of Natural Science and Technology, Okayama University), Akira Ishikawa(Department of Earth and Planetary Sciences, Tokyo Institute of Technology)

[SGC49-P01] Particle size control of olivine alteration pathway and rate for simultaneous H2 generation and CO2 storage

*Jiajie Wang1, Noriaki Watanabe1, Atsushi Okamoto1, Kengo Nakamura1, Takeshi Komai1 (1.Tohoku University)

Keywords:Olivine, grain size, hydrogen, carbon storage

The hydrothermal alteration of olivine [(Mg,Fe)2SiO4] has attracted considerable attention as it represents not only a potential way to produce hydrogen (H2) by the oxidation of Fe(II) in it, but also to store CO2 by its carbonation. The combination of the strategies of H2 production and CO2 storage during H2O-olivine-CO2 reaction may be a promising way to contribute to low-carbon society development. During H2O-olivine-CO2 reaction, the olivine grain size is a key parameter in controlling olivine dissolution and products generation rates.

In this study, three experiments with olivine particles of 28-53, 53-90 and 90-160 µm were conducted in 0.5 mol/L NaHCO3 solution at 300 °C for 72 h. Olivine alteration rate (r, wt%/h) was closely related to its geometric surface area (GS, m2/g), with the linear relationship of r=4.097GS. H2 production was much higher with the simultaneous CO2 storage [in magnesite, (Mg,Fe)CO3] in the experiment with an olivine grain size of 28-53 µm than those with larger olivine grain sizes. The highest cumulative H2 yield was 118 mmol/kgolivine in 72 h. The inhibited magnesite precipitation in experiments with olivine grain size >53 µm was attributed to the low Mg concentrations caused by the slow olivine dissolutions. The results also suggest olivine serpentinization proceeded faster than carbonation, and the covering of olivine with serpentines [(Mg,Fe)3Si2O5(OH)4] may inhibited further olivine alteration and H2 production.
Therefore, decrease the olivine grain size to < 53 µm is an efficient way not only to enhance olivine alteration with H2 production but also to realize simultaneous H2 production and CO2 storage during H2O-olivine-CO2 reaction.