In the past few years, experimental studies have shown that CO₂ is roughly 5 times more soluble in water-saturated clay interlayer water than in bulk liquid water. The fundamental basis of this selectivity remains unknown, as does its relevance to other gases. Here, we use molecular dynamics (MD) simulations and gravimetric adsorption experiments to determine the solubilities of CO₂, CH₄, H₂, and noble gases in clay interlayer water. Our results confirm that clay minerals, despite their well-known hygroscopic nature, have a significant hydrophobic character at the atomistic scale. The affinity of dissolved gases for the clay surface shows significant variations related to the size and shape of the adsorbing molecules and the structuring of interfacial water by clay surfaces. Our results indicate that dissolved gases likely do not behave as inert tracers in fine-grained sedimentary rocks such as shale and mudstone, as routinely assumed in groundwater hydrology studies. Our results have implications for the fundamental science of hydrophobic adsorption, for the use of dissolved gases as tracers of fluid migration in the subsurface, and for low-carbon energy technologies that rely on fine-grained sedimentary rocks, such as carbon capture and storage, nuclear energy, and the transition from coal to natural gas.

中文翻译：

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粘土层间纳米孔中气体（CO ₂，CH ₄，H ₂，稀有气体）的疏水溶剂化

在过去的几年中，实验研究表明，CO ₂在水饱和粘土夹层水中的溶解度大约是在散装液态水中的5倍。这种选择性的基本基础以及与其他气体的相关性仍然未知。在这里，我们使用分子动力学（MD）模拟和重量吸附实验来确定CO ₂，CH ₄，H ₂的溶解度以及粘土夹层水中的稀有气体。我们的结果证实，尽管粘土矿物质具有众所周知的吸湿性，但它们在原子尺度上仍具有显着的疏水性。溶解气体对粘土表面的亲和力显示出与吸附分子的大小和形状以及粘土表面的界面水结构有关的显着变化。我们的结果表明，在地下水水文学研究中通常假设的情况下，在页岩和泥岩等细颗粒沉积岩中，溶解气体可能不会表现出惰性示踪剂的作用。我们的研究结果对疏水吸附的基础科学，使用溶解气体作为地下流体运移的示踪剂以及依赖于细粒沉积岩的低碳能源技术具有重要意义，