title: In Situ Natural Abundance17O and25Mg NMR Investigation of Aqueous Mg(OH)2Dissolution in the Presence of Supercritical CO2.
abstract: We report an in situ high-pressure NMR capability that permits natural abundance17O and25Mg NMR characterization of dissolved species in aqueous solution and in the presence of supercritical CO2fluid (scCO2). The dissolution of Mg(OH)2(brucite) in a multiphase water/scCO2fluid at 90 atm pressure and 50 °C was studied in situ, with relevance to geological carbon sequestration.17O NMR spectra allowed identification and distinction of various fluid species including dissolved CO2in the H2O-rich phase, scCO2, aqueous H2O, and HCO3-. The widely separated spectral peaks for various species can all be observed both dynamically and quantitatively at concentrations as low as 20 mM. Measurement of the concentrations of these individual species also allows an in situ estimate of the hydrogen ion concentration, or pCH+values, of the reacting solutions. The concentration of Mg2+can be observed by natural abundance25Mg NMR at a concentration as low as 10 mM. Quantum chemistry calculations of the NMR chemical shifts on cluster models aided in the interpretation of the experimental results. Evidence for the formation of polymeric Mg2+clusters at high concentrations in the H2O-rich phase, a possible critical step needed for magnesium carbonate formation, was found.
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Mary Y
authors.initials: MY
authors.lastname: Hu
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Xuchu
authors.initials: X
authors.lastname: Deng
authors.affiliation: Department of Chemistry, The University of Alabama , Shelby Hall, Tuscaloosa, Alabama 35487, United States.
authors.forename: K Sahan
authors.initials: KS
authors.lastname: Thanthiriwatte
authors.affiliation: Department of Chemistry, The University of Alabama , Shelby Hall, Tuscaloosa, Alabama 35487, United States.
authors.forename: Virgil E
authors.initials: VE
authors.lastname: Jackson
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Chuan
authors.initials: C
authors.lastname: Wan
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Odeta
authors.initials: O
authors.lastname: Qafoku
authors.affiliation: Department of Chemistry, The University of Alabama , Shelby Hall, Tuscaloosa, Alabama 35487, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Dixon
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Felmy
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Rosso
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Jian Zhi
authors.initials: JZ
authors.lastname: Hu
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D057965:Carbon Sequestration; D009682:Magnetic Resonance Spectroscopy; D012995:Solubility; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D002245:Carbon Dioxide