Quantitative Identification of Metastable Magnesium Carbonate Minerals by Solid-State 13C NMR Spectroscopy

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• 作者：Jeremy K. Moore ; J. Andrew Surface ; Allison Brenner ; Philip Skemer ; Mark S. Conradi ; Sophia E. Hayes
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：January 6, 2015
• 年：2015
• 卷：49
• 期：1
• 页码：657-664
• 全文大小：308K
• ISSN：1520-5851

文摘

In the conversion of CO₂ to mineral carbonates for the permanent geosequestration of CO₂, there are multiple magnesium carbonate phases that are potential reaction products. Solid-state ¹³C NMR is demonstrated as an effective tool for distinguishing magnesium carbonate phases and quantitatively characterizing magnesium carbonate mixtures. Several of these mineral phases include magnesite, hydromagnesite, dypingite, and nesquehonite, which differ in composition by the number of waters of hydration or the number of crystallographic hydroxyl groups. These carbonates often form in mixtures with nearly overlapping ¹³C NMR resonances which makes their identification and analysis difficult. In this study, these phases have been investigated with solid-state ¹³C NMR spectroscopy, including both static and magic-angle spinning (MAS) experiments. Static spectra yield chemical shift anisotropy (CSA) lineshapes that are indicative of the site-symmetry variations of the carbon environments. MAS spectra yield isotropic chemical shifts for each crystallographically inequivalent carbon and spin鈥搇attice relaxation times, T₁, yield characteristic information that assist in species discrimination. These detailed parameters, and the combination of static and MAS analyses, can aid investigations of mixed carbonates by ¹³C NMR.