Nanoconfinement matters in humidified CO2 interaction with metal silicates,Environmental Science: Nano

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Nanoconfinement matters in humidified CO2 interaction with metal silicates
Environmental Science: Nano ( IF 5.8 ) Pub Date : 2022-08-22 , DOI: 10.1039/d2en00148a
Siavash Zare ₁ , K. M. Salah Uddin ₂ , Andreas Funk _{2,

3} , Quin R. S. Miller ₄ , Mohammad Javad Abdolhosseini Qomi ₁

Affiliation

With enigmatic observations of enhanced reactivity of wet CO₂-rich fluids with metal silicates, the mechanistic understanding of molecular processes governing carbonation proves critical in designing secure geological carbon sequestration and economical carbonated concrete technologies. Here, we use the first principle and classical molecular simulations to probe the impact of nanoconfinement on physicochemical processes at the rock–water–CO₂ interface. We choose nanoporous calcium–silicate–hydrate (C–S–H) and forsterite (Mg₂SiO₄) as model metal silicate surfaces that are of significance in cement chemistry and geochemistry communities, respectively. We show that while a nanometer-thick interfacial water film persists at unsaturated conditions consistent with in situ infrared spectroscopy, the phase behavior of the water–CO₂ mixture changes from its bulk counterpart depending on the surface chemistry and nanoconfinement. We also observe enhanced solubility at the interface of water and CO₂ phases, which could amplify the CO₂ speciation rate. Through free energy calculations, we show that CO₂ could be found in a metastable state near the C–S–H surface, which can potentially react with surface water and hydroxyl groups to form carbonic acid and bicarbonate. These findings support the explicit consideration of nanoconfinement effects in reactive and non-reactive pore-scale processes.

中文翻译：

纳米限制在加湿 CO2 与金属硅酸盐的相互作用中很重要

_{随着对富含 CO 2}的湿流体与金属硅酸盐的反应性增强的神秘观察，对控制碳化的分子过程的机械理解证明对于设计安全的地质碳封存和经济的碳化混凝土技术至关重要。在这里，我们使用第一原理和经典分子模拟来探索纳米限制对岩石-水-CO ₂界面物理化学过程的影响。我们选择纳米多孔硅酸钙水合物 (C-S-H) 和镁橄榄石 (Mg ₂ SiO ₄）作为模型金属硅酸盐表面，分别在水泥化学和地球化学界具有重要意义。我们表明，虽然纳米厚的界面水膜在与原位红外光谱一致的不饱和条件下持续存在，但水-CO ₂混合物的相行为与其本体对应物的相行为不同，取决于表面化学和纳米限制。_{我们还观察到水和 CO 2}相界面处的溶解度增加，这可以放大 CO ₂形态速率。通过自由能计算，我们证明了 CO ₂可以在 C-S-H 表面附近发现处于亚稳态，它可能与地表水和羟基反应形成碳酸和碳酸氢盐。这些发现支持在反应性和非反应性孔隙尺度过程中明确考虑纳米限制效应。

更新日期：2022-08-22

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