Microstructural Response of Variably Hydrated Ca-rich Montmorillonite to Supercritical CO2

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• 作者：Mal-Soon Lee ; B. Peter McGrail ; Vassiliki-Alexandra Glezakou
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：August 5, 2014
• 年：2014
• 卷：48
• 期：15
• 页码：8612-8619
• 全文大小：522K
• ISSN：1520-5851

文摘

First-principles molecular dynamics simulations were carried out to explore the mechanistic and thermodynamic ramifications of the exposure of variably hydrated Ca-rich montmorillonites to supercritical CO₂ and CO₂鈥揝O₂ mixtures under geologic storage conditions. In sub- to single-hydrated systems (鈮?W), CO₂ intercalation causes interlamellar expansion of 8鈥?2%, while systems transitioning to 2W may undergo contraction (7%) or remain almost unchanged. When compared to 2W hydration state, structural analysis of the 鈮?W systems, reveals more Ca-CO₂ contacts and partial transition to vertically confined CO₂ molecules. Infrared spectra and projected vibrational frequency analysis imply that intercalated Ca-bound CO₂ are vibrationally constrained and contribute to the higher frequencies of the asymmetric stretch band. Reduced diffusion coefficients of intercalated H₂O and CO₂ (10^鈥?鈥?0^鈥? cm²/s) indicate that Ca-montmorillonites in 1W hydration states can be more efficient in capturing CO₂. Simulations including SO₂ imply that 0.66 mmol SO₂/g clay can be intercalated without other significant structural changes. SO₂ is likely to divert H₂O away from the cations, promoting Ca-CO₂ interactions and CO₂ capture by further reducing CO₂ diffusion (10^鈥? cm²/s). Vibrational bands at 1267 or 1155 cm^鈥? may be used to identify the chemical state (oxidation states +4 or +6, respectively) and the fate of sulfur contaminants.