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Title: In Situ Natural Abundance 17 O and 25 Mg NMR Investigation of Aqueous Mg(OH) 2 Dissolution in the Presence of Supercritical CO 2

Abstract

We report the development of an in situ high pressure NMR capability that permits natural abundance 17O and 25Mg NMR characterization of dissolved species in aqueous solution and in the presence of supercritical CO2 fluid (scCO2). The dissolution of Mg(OH)2 (brucite) in a multiphase water/scCO2 fluid 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 CO2 in 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 of 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 abundance 25Mg 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, wasmore » found. The approach and findings enable insight into metal carbonation reactions associated with geological carbon sequestration that cannot be probed by ex situ methods.« less

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1339836
Report Number(s):
PNNL-SA-118648
Journal ID: ISSN 0013-936X; 47824; KC0302060
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 50; Journal Issue: 22; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Environmental Molecular Sciences Laboratory

Citation Formats

Hu, Mary Y., Deng, Xuchu, Thanthiriwatte, K. Sahan, Jackson, Virgil E., Wan, Chuan, Qafoku, Odeta, Dixon, David A., Felmy, Andrew R., Rosso, Kevin M., and Hu, Jian Zhi. In Situ Natural Abundance 17 O and 25 Mg NMR Investigation of Aqueous Mg(OH) 2 Dissolution in the Presence of Supercritical CO 2. United States: N. p., 2016. Web. doi:10.1021/acs.est.6b03443.
Hu, Mary Y., Deng, Xuchu, Thanthiriwatte, K. Sahan, Jackson, Virgil E., Wan, Chuan, Qafoku, Odeta, Dixon, David A., Felmy, Andrew R., Rosso, Kevin M., & Hu, Jian Zhi. In Situ Natural Abundance 17 O and 25 Mg NMR Investigation of Aqueous Mg(OH) 2 Dissolution in the Presence of Supercritical CO 2. United States. https://doi.org/10.1021/acs.est.6b03443
Hu, Mary Y., Deng, Xuchu, Thanthiriwatte, K. Sahan, Jackson, Virgil E., Wan, Chuan, Qafoku, Odeta, Dixon, David A., Felmy, Andrew R., Rosso, Kevin M., and Hu, Jian Zhi. 2016. "In Situ Natural Abundance 17 O and 25 Mg NMR Investigation of Aqueous Mg(OH) 2 Dissolution in the Presence of Supercritical CO 2". United States. https://doi.org/10.1021/acs.est.6b03443.
@article{osti_1339836,
title = {In Situ Natural Abundance 17 O and 25 Mg NMR Investigation of Aqueous Mg(OH) 2 Dissolution in the Presence of Supercritical CO 2},
author = {Hu, Mary Y. and Deng, Xuchu and Thanthiriwatte, K. Sahan and Jackson, Virgil E. and Wan, Chuan and Qafoku, Odeta and Dixon, David A. and Felmy, Andrew R. and Rosso, Kevin M. and Hu, Jian Zhi},
abstractNote = {We report the development of an in situ high pressure NMR capability that permits natural abundance 17O and 25Mg NMR characterization of dissolved species in aqueous solution and in the presence of supercritical CO2 fluid (scCO2). The dissolution of Mg(OH)2 (brucite) in a multiphase water/scCO2 fluid 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 CO2 in 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 of 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 abundance 25Mg 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. The approach and findings enable insight into metal carbonation reactions associated with geological carbon sequestration that cannot be probed by ex situ methods.},
doi = {10.1021/acs.est.6b03443},
url = {https://www.osti.gov/biblio/1339836}, journal = {Environmental Science and Technology},
issn = {0013-936X},
number = 22,
volume = 50,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2016},
month = {Tue Nov 15 00:00:00 EST 2016}
}