Department of Energy, Environmental, and Chemical Engineering, Washington University in St Louis, Campus Box 1180, One Brookings Drive, St Louis, Missouri 63130, USA.
Environ Sci Technol. 2013 Jan 2;47(1):168-73. doi: 10.1021/es301231n.
The rates and mechanisms of magnesium silicate dissolution can control the aqueous chemistry in ways that influence carbonate mineral precipitation during geologic carbon sequestration (GCS). A series of batch experiments was performed with forsterite (Mg(1.81)Fe(0.19)SiO(4)) powder to determine the effects of pressure (10-100 bar CO(2)), temperature (25-100 °C), and salinity (0-50,000 mg/L NaCl) on its dissolution rate at conditions relevant to GCS. Dissolution rates and products were determined by analysis of the aqueous phase, equilibrium and reaction path modeling, and solid phase characterization by scanning electron microscopy and X-ray diffraction. After an initially rapid dissolution period, the dissolution rate declined significantly, an effect that is attributed to the formation of a silica-rich layer at the forsterite surface. The initial dissolution rate increased with increasing temperature and increasing CO(2) pressure; the effect of CO(2) was through its influence on the pH. The dissolution rate was enhanced by NaCl, which may have been due to its inhibition of the formation of a silica-rich surface layer. The experimental results provide information about magnesium silicate dissolution at conditions that will be encountered during GCS that can be used to predict the fate of CO(2) and the evolution of subsurface geochemistry following CO(2) injection.
硅酸镁的溶解速率和机制可以通过影响地质碳封存（GCS）过程中碳酸盐矿物沉淀的方式来控制水化学。我们进行了一系列方镁石（Mg(1.81)Fe(0.19)SiO(4)）粉末的间歇实验，以确定压力（10-100 巴 CO(2)）、温度（25-100°C）和盐度（0-50,000 mg/L NaCl）对 GCS 相关条件下其溶解速率的影响。通过分析水相、平衡和反应路径建模以及扫描电子显微镜和 X 射线衍射对固相的表征来确定溶解速率和产物。在初始快速溶解期后，溶解速率显著下降，这一效应归因于方镁石表面形成了富含二氧化硅的层。初始溶解速率随温度和 CO(2)压力的增加而增加；CO(2)的影响是通过其对 pH 值的影响。NaCl 增强了溶解速率，这可能是由于其抑制了富含二氧化硅表面层的形成。实验结果提供了有关 GCS 过程中会遇到的硅酸镁溶解情况的信息，可用于预测 CO(2)的命运和 CO(2)注入后地下地球化学的演变。
