Department of Energy, Environmental, and Chemical Engineering, Washington University , St. Louis, Missouri 63130, United States.
Environ Sci Technol. 2015 Feb 3;49(3):1946-54. doi: 10.1021/es504586u. Epub 2015 Jan 20.
Geologic CO2 sequestration (GCS) is one of the most promising methods to mitigate the adverse impacts of global climate change. The performance of GCS can be affected by mineral dissolution and precipitation induced by injected CO2. Cosequestration with acidic gas such as SO2 can reduce the high cost of GCS, but it will increase the sulfate's concentration in GCS sites, where sulfate can potentially affect plagioclase dissolution/precipitation. This work investigated the effects of 0.05 M sulfate on plagioclase (anorthite) dissolution and subsequent mineral precipitation at 90 °C, 100 atm CO2, and 1 M NaCl, conditions relevant to GCS sites. The adsorption of sulfate on anorthite, a Ca-rich plagioclase, was examined using attenuated total reflectance Fourier-transform infrared spectroscopy and then simulated using density functional theory calculations. We found that the dissolution rate of anorthite was enhanced by a factor of 1.36 by the formation of inner-sphere monodentate complexes between sulfate and the aluminum sites on anorthite surfaces. However, this effect was almost completely suppressed in the presence of 0.01 M oxalate, an organic ligand that can exist in GCS sites. Interestingly, sulfate also inhibited the formation of secondary mineral precipitation through the formation of aluminum-sulfate complexes in the aqueous phase. This work, for the first time, reports the surface complexation between sulfate and plagioclase that can occur in GCS sites. The results provide new insights for obtaining scientific guidelines for the proper amount of SO2 coinjection and finally for evaluating the economic efficiency and environmental safety of GCS operations.
地质封存二氧化碳（GCS）是缓解全球气候变化不利影响的最有前途的方法之一。注入的二氧化碳引起的矿物溶解和沉淀会影响 GCS 的性能。与 SO2 等酸性气体共封存可以降低 GCS 的高成本，但会增加 GCS 场地中硫酸盐的浓度，硫酸盐可能会影响斜长石的溶解/沉淀。本工作研究了在 90°C、100 大气压 CO2 和 1 M NaCl 条件下，0.05 M 硫酸盐对斜长石（钙长石）溶解及其后续矿物沉淀的影响，这些条件与 GCS 场地相关。采用衰减全反射傅里叶变换红外光谱法（ATR-FTIR）研究了硫酸盐在富钙斜长石上的吸附，并采用密度泛函理论（DFT）计算进行了模拟。结果表明，在富铝斜长石表面，硫酸盐与铝位之间形成内球单齿配合物，使斜长石的溶解速率提高了 1.36 倍。然而，在存在 0.01 M 草酸盐（一种可能存在于 GCS 场地的有机配体）的情况下，这种作用几乎完全被抑制。有趣的是，硫酸盐还通过在水相形成铝硫酸盐配合物来抑制次生矿物沉淀的形成。本工作首次报道了在 GCS 场地中可能发生的硫酸盐与斜长石之间的表面络合作用。研究结果为获得关于适量 SO2 共注入的科学指导方针提供了新的见解，最终为评估 GCS 操作的经济效益和环境安全性提供了依据。
