title: Quantitative identification of metastable magnesium carbonate minerals by solid-state 13C NMR spectroscopy.
abstract: 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 (13)C 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 (13)C NMR resonances which makes their identification and analysis difficult. In this study, these phases have been investigated with solid-state (13)C 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-lattice 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 (13)C NMR.
authors.affiliation: Department of Chemistry, Washington University , One Brookings Drive, Saint Louis, Missouri, 63130, United States.
authors.forename: Jeremy K
authors.initials: JK
authors.lastname: Moore
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Surface
authors.forename: Allison
authors.initials: A
authors.lastname: Brenner
authors.forename: Louis S
authors.initials: LS
authors.lastname: Wang
authors.forename: Philip
authors.initials: P
authors.lastname: Skemer
authors.forename: Mark S
authors.initials: MS
authors.lastname: Conradi
authors.forename: Sophia E
authors.initials: SE
authors.lastname: Hayes
mesh_terms: D016880:Anisotropy; D066241:Carbon-13 Magnetic Resonance Spectroscopy; D008274:Magnesium / Q000032:analysis*; D008903:Minerals / Q000032:analysis*; D011522:Protons; D013997:Time Factors
chemical_list: D008903:Minerals; D011522:Protons; C005479:magnesium carbonate; D008274:Magnesium