09:15 〜 09:30
[HSC06-02] Surface Chemistry and Carbon Mineralization Potential of Pyroxene Basalt
キーワード：carbon mineralization, surface complexation model, pyroxene basalt
Understanding the chemical interactions between CO2 and basaltic mineral surfaces is essential for evaluating carbon mineralization potential. To bridge the gap between slow carbonate precipitation kinetics and fast mineralization rates in field experiments, a novel surface reaction mechanism that CO2 molecules can react with nonbridging oxygen sites on basaltic mineral surfaces is proposed. This study focuses on pyroxene as a representative basaltic mineral, developing a surface complexation model (SCM) validated by experimental zeta potential data. We investigate the role of key CO2 surface reaction pathways in mineralization storage potential under CO2 aqueous solution and humidified supercritical CO2 conditions.
Our findings show that in CO2 aqueous solution without cations, optimal mineralization (0.61 kg CO2/m3) through surface reactions is achieved at pH 6, primarily through CO32- adsorption onto surface metal ions (>MgOH0, >CaOH0) (Figure 1). High metal ion concentrations (100 mg/L Mg2+ and 100 mg/L Ca2+) significantly enhance CO2 reactivity with nonbridging oxygens, increasing reaction ratios from 0.55% to 9.69%. Therefore, the optimal mineralization storage potential increases to 0.85 kg/m3 compared to 0.61 kg/m3 without cations. In contrast, supercritical CO2 conditions favor CO2 surface reactions with nonbridging oxygens with neglectable CO32- adsorption onto surface metal ions. The reaction ratio of nonbridging oxygens increases exponentially with CO2 volume fraction. The maximum CO2 storage capacity achieved through surface reactions is 0.41 kg CO2/m3 basalt at 90% CO2 volume fraction.
At early injection stages, the acidic environment and rate-limiting metal ion dissolution restrict carbonate precipitation and favor storage through surface reactions. The formation of surface carbonates provides nucleation sites for carbonate precipitation. Based on experiments[1], the annual storage potential through carbonate precipitation is 1.24 kg/m3, showing that surface reaction potential is critical in CO2 sequestration, complementing traditional carbonate precipitation mechanisms. This work provides a refined understanding of mineral carbonation pathways and vital insights for optimizing CO2 mineralization strategies in basaltic reservoirs.
Reference
[1] Xiong, W.; Wells, R. K.; Horner, J. A.; Schaef, H. T.; Skemer, P. A.; Giammar, D. E. CO2 Mineral Sequestration in Naturally Porous Basalt. Environ. Sci. Technol. Lett. 2018, 5, 142-147. https://doi.org/10.1021/acs.estlett.8b00047.
Our findings show that in CO2 aqueous solution without cations, optimal mineralization (0.61 kg CO2/m3) through surface reactions is achieved at pH 6, primarily through CO32- adsorption onto surface metal ions (>MgOH0, >CaOH0) (Figure 1). High metal ion concentrations (100 mg/L Mg2+ and 100 mg/L Ca2+) significantly enhance CO2 reactivity with nonbridging oxygens, increasing reaction ratios from 0.55% to 9.69%. Therefore, the optimal mineralization storage potential increases to 0.85 kg/m3 compared to 0.61 kg/m3 without cations. In contrast, supercritical CO2 conditions favor CO2 surface reactions with nonbridging oxygens with neglectable CO32- adsorption onto surface metal ions. The reaction ratio of nonbridging oxygens increases exponentially with CO2 volume fraction. The maximum CO2 storage capacity achieved through surface reactions is 0.41 kg CO2/m3 basalt at 90% CO2 volume fraction.
At early injection stages, the acidic environment and rate-limiting metal ion dissolution restrict carbonate precipitation and favor storage through surface reactions. The formation of surface carbonates provides nucleation sites for carbonate precipitation. Based on experiments[1], the annual storage potential through carbonate precipitation is 1.24 kg/m3, showing that surface reaction potential is critical in CO2 sequestration, complementing traditional carbonate precipitation mechanisms. This work provides a refined understanding of mineral carbonation pathways and vital insights for optimizing CO2 mineralization strategies in basaltic reservoirs.
Reference
[1] Xiong, W.; Wells, R. K.; Horner, J. A.; Schaef, H. T.; Skemer, P. A.; Giammar, D. E. CO2 Mineral Sequestration in Naturally Porous Basalt. Environ. Sci. Technol. Lett. 2018, 5, 142-147. https://doi.org/10.1021/acs.estlett.8b00047.