18:15 〜 19:30
[U05-P03] 超塩基性岩－水相互作用における水素生成に対する鉱物の役割
Hydrogen generation by high temperature serpentinization is understood as hydration of mafic and ultramafic rocks, owing to the oxidation of reduced iron present in the olivine or pyroxene. On the other hand, in the Oman Ophiolite and Lost City Hydrotherrmal Field (LCHF) in the Mid-Atlantic Ridge, hydrogen is generated via low temperature serpentinization. Moreover, previous experimental study shown generating hydrogen at low temperatures (<100 degrees C). However, since even the rate of hydrogen generation by high temperature serpentinization is slow, the mechanism of hydrogen generation by low temperature in short period is yet to be explained. Therefore, the objective of this study is to clarify the mechanism of hydrogen generation via low temperature serpentinization for a short period. Batch experiments were conducted at 30 degrees C, 60 degrees C and 90 degrees C using minerals which constitute ultramafic rocks (olivine, Magnetite, Fe-Ni alloy), and serpentinite. Samples were taken after various reaction times (3h, 6h, 12h, 24h, and 1week). Liquid samples were analyzed by ICP-AES, ion chromatography, UV-Vis, pH, and ORP. Mineral phase changes in the solid samples were characterized by TG-DTA, SEM-EDX and XRD. The concentration of hydrogen gas was determined by GC-RGD.
Hydrogen generation was observed in all samples. Highest concentration of hydrogen gas was observed in the experiment using Fe-Ni alloy. In the experiment using Fe-Ni alloy, apparent surface change was not observed at the surface of Fe-Ni alloy. Therefore, hydrogen gas was generated by catalysis of Fe-Ni. The generation of hydrogen gas by this catalysis would be higher than that of generated hydrogen accomplished by the dissolution of olivine, which is the dominant mineral in the ultramafic rocks.
In this study, the hydrogen generation was confirmed at a temperature of less than 90 degrees C. The hydrogen generation process is catalyzed by Fe-Ni alloys or magnetite present in secondary minerals by serpentinization.
Hydrogen generation was observed in all samples. Highest concentration of hydrogen gas was observed in the experiment using Fe-Ni alloy. In the experiment using Fe-Ni alloy, apparent surface change was not observed at the surface of Fe-Ni alloy. Therefore, hydrogen gas was generated by catalysis of Fe-Ni. The generation of hydrogen gas by this catalysis would be higher than that of generated hydrogen accomplished by the dissolution of olivine, which is the dominant mineral in the ultramafic rocks.
In this study, the hydrogen generation was confirmed at a temperature of less than 90 degrees C. The hydrogen generation process is catalyzed by Fe-Ni alloys or magnetite present in secondary minerals by serpentinization.