9:30 AM - 9:45 AM
[HSC06-03] Experimental constraints on carbonate precipitation during andesite-CO2-dissolved water interaction
Keywords:Carbon mineralization, Carbon capture and storage, Andesite-CO2-water-interaction, Batch experiment
Carbon mineralization in mafic and ultramafic rocks has been proposed as a promising method in carbon capture and storage (CCS). In contrast, the potential of andesite, a common type of volcanic rocks in Japan, for carbon mineralization remains unclear. Therefore, we conducted a series of hydrothermal batch-type experiments with rock samples under stirring conditions, and analyses of mineral textures and the amount of CO2 fixed in the rock.
Four types of rock samples were prepared: two andesite samples (Andesite_N1 and Andesite_N2) collected from the Nagaoka region in Niigata, an andesite sample (Andesite_Z) from the Zao region in Miyagi, and a basalt sample (Basalt) from Iceland. Andesite_N1 and Andesite_N2 contained a small amount of naturally formed calcite, while Andesite_Z was rather unaltered and contained a small amount of olivine. A batch experiment under stirring conditions was conducted using powdered rock samples (2.0 g), Milli-Q water (50 mL), and gaseous CO2. The experimental pressure was set at 20 MPa, and the temperature was controlled at 150℃ and 200℃ for a duration of 10 days. After the experiment, the solution and rock samples were analyzed using ICP-OES, EPMA, thermogravimetry, and TPD-MS.
The analyses of the solutions after the individual runs showed that the concentrations of Ca and Mg at 200℃ were higher than those at 150℃ for andesite samples (Andesite_Z, Andesite_N1, and Andesite_N2). In contrast, for the basalt sample, the concentrations of Ca and Mg in the solution after the 200℃ experiment were lower than those after the 150℃ experiment.
In all runs, carbonate mineral and smectite. The carbonate minerals precipitated on the surfaces of primary minerals, exhibiting well-defined crystal shapes. In contrast, the clay minerals commonly formed as thin films surrounding the primary minerals. The carbonate minerals in each sample exhibited systematic differences in chemical composition: those in the andesite samples show high Ca and Mg ratios (Ca0.57-0.95Mg0.04-0.42Fe0.00-0.11; calcite-dolomite), while those in the basalt samples show high Mg and Fe ratios (Ca0.15-0.27Mg0.39-0.48Fe0.28-0.45; magnesite). These compositional differences are likely due to variations in the mineral composition and dissolution characteristics of the host rock. In the TG analyses, the mass loss for CO2 occurred in a range of 300℃ -900℃, and the mass loss at 200°C was 1.4 to 2.4 times greater than that at 150℃, respectively. Furthermore, TPD-MS was used to quantify the amount of CO2 fixed in each sample. The results showed that the amount of CO2 fixed in the Andesite_N1 sample during the 200°C experiment was 0.38 mmol/g, which was comparable to the 0.45 mmol/g observed in the Basalt sample at 150℃. The TG-MS results indicate that higher temperatures promote the dissolution of primary minerals, leading to increased precipitation of secondary minerals, suggesting that the dissolution-precipitation process in rock-CO2-water interactions is temperature-dependent. Additionally, the TPD-MS results suggest that under appropriate conditions, carbon mineralization in andesite can proceed effectively, demonstrating a potential for CO2 storage comparable to that of basalt. This suggests that andesite is a viable candidate for consideration as a material for carbon mineralization.
In the future work, geochemical modeling and detailed analysis of the host rock's mineral composition will be utilized to elucidate the timescale of carbonate mineral formation and differences in their chemical composition.
Four types of rock samples were prepared: two andesite samples (Andesite_N1 and Andesite_N2) collected from the Nagaoka region in Niigata, an andesite sample (Andesite_Z) from the Zao region in Miyagi, and a basalt sample (Basalt) from Iceland. Andesite_N1 and Andesite_N2 contained a small amount of naturally formed calcite, while Andesite_Z was rather unaltered and contained a small amount of olivine. A batch experiment under stirring conditions was conducted using powdered rock samples (2.0 g), Milli-Q water (50 mL), and gaseous CO2. The experimental pressure was set at 20 MPa, and the temperature was controlled at 150℃ and 200℃ for a duration of 10 days. After the experiment, the solution and rock samples were analyzed using ICP-OES, EPMA, thermogravimetry, and TPD-MS.
The analyses of the solutions after the individual runs showed that the concentrations of Ca and Mg at 200℃ were higher than those at 150℃ for andesite samples (Andesite_Z, Andesite_N1, and Andesite_N2). In contrast, for the basalt sample, the concentrations of Ca and Mg in the solution after the 200℃ experiment were lower than those after the 150℃ experiment.
In all runs, carbonate mineral and smectite. The carbonate minerals precipitated on the surfaces of primary minerals, exhibiting well-defined crystal shapes. In contrast, the clay minerals commonly formed as thin films surrounding the primary minerals. The carbonate minerals in each sample exhibited systematic differences in chemical composition: those in the andesite samples show high Ca and Mg ratios (Ca0.57-0.95Mg0.04-0.42Fe0.00-0.11; calcite-dolomite), while those in the basalt samples show high Mg and Fe ratios (Ca0.15-0.27Mg0.39-0.48Fe0.28-0.45; magnesite). These compositional differences are likely due to variations in the mineral composition and dissolution characteristics of the host rock. In the TG analyses, the mass loss for CO2 occurred in a range of 300℃ -900℃, and the mass loss at 200°C was 1.4 to 2.4 times greater than that at 150℃, respectively. Furthermore, TPD-MS was used to quantify the amount of CO2 fixed in each sample. The results showed that the amount of CO2 fixed in the Andesite_N1 sample during the 200°C experiment was 0.38 mmol/g, which was comparable to the 0.45 mmol/g observed in the Basalt sample at 150℃. The TG-MS results indicate that higher temperatures promote the dissolution of primary minerals, leading to increased precipitation of secondary minerals, suggesting that the dissolution-precipitation process in rock-CO2-water interactions is temperature-dependent. Additionally, the TPD-MS results suggest that under appropriate conditions, carbon mineralization in andesite can proceed effectively, demonstrating a potential for CO2 storage comparable to that of basalt. This suggests that andesite is a viable candidate for consideration as a material for carbon mineralization.
In the future work, geochemical modeling and detailed analysis of the host rock's mineral composition will be utilized to elucidate the timescale of carbonate mineral formation and differences in their chemical composition.