Sandia National Laboratories, 1515 Eubank, Albuquerque, New Mexico 87123, United States.
Environ Sci Technol. 2014;48(3):2035-42. doi: 10.1021/es404075k. Epub 2014 Jan 15.
Capture and subsequent geologic storage of CO2 in deep brine reservoirs plays a significant role in plans to reduce atmospheric carbon emission and resulting global climate change. The interaction of CO2 and brine species with mineral surfaces controls the ultimate fate of injected CO2 at the nanoscale via geochemistry, at the pore-scale via capillary trapping, and at the field-scale via relative permeability. We used large-scale molecular dynamics simulations to study the behavior of supercritical CO2 and aqueous fluids on both the hydrophilic and hydrophobic basal surfaces of kaolinite, a common clay mineral. In the presence of a bulk aqueous phase, supercritical CO2 forms a nonwetting droplet above the hydrophilic surface of kaolinite. This CO2 droplet is separated from the mineral surface by distinct layers of water, which prevent the CO2 droplet from interacting directly with the mineral surface. Conversely, both CO2 and H2O molecules interact directly with the hydrophobic surface of kaolinite. In the presence of bulk supercritical CO2, nonwetting aqueous droplets interact with the hydrophobic surface of kaolinite via a mixture of adsorbed CO2 and H2O molecules. Because nucleation and precipitation of minerals should depend strongly on the local distribution of CO2, H2O, and ion species, these nanoscale surface interactions are expected to influence long-term mineralization of injected carbon dioxide.
将二氧化碳捕获并随后地质存储在深层卤水中，在减少大气碳排放和由此导致的全球气候变化的计划中发挥着重要作用。二氧化碳和卤水物种与矿物表面的相互作用通过地球化学在纳米尺度上控制注入二氧化碳的最终命运，通过毛管捕集在孔隙尺度上，通过相对渗透率在现场尺度上。我们使用大规模分子动力学模拟来研究超临界二氧化碳和水溶液在高岭石亲水和疏水基面的行为，高岭石是一种常见的粘土矿物。在存在大量水相的情况下，超临界二氧化碳在高岭石亲水表面上方形成不润湿的液滴。该二氧化碳液滴与矿物表面通过水的明显层隔开，这阻止了二氧化碳液滴与矿物表面直接相互作用。相反，二氧化碳和水分子都直接与高岭石的疏水表面相互作用。在存在大量超临界二氧化碳的情况下，非润湿水液滴通过吸附的二氧化碳和水分子的混合物与高岭石的疏水表面相互作用。由于矿物的成核和沉淀应该强烈依赖于 CO2、H2O 和离子物种的局部分布，因此这些纳米尺度的表面相互作用预计会影响注入二氧化碳的长期矿化作用。
