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Title: Brucite [Mg(OH2)] Carbonation in Wet Supercritical CO2: An in situ High Pressure X-Ray Diffraction Study

Abstract

Understanding mechanisms and kinetics of mineral carbonation reactions relevant to sequestering carbon dioxide as a supercritical fluid (scCO2) in geologic formations is crucial to accurately predicting long-term storage risks. Most attention so far has been focused on reactions occurring between silicate minerals and rocks in the aqueous dominated CO2-bearing fluid. However, water-bearing scCO2 also comprises a reactive fluid, and in this situation mineral carbonation mechanisms are poorly understood. Using in situ high-pressure x-ray diffraction, the carbonation of brucite [Mg(OH)2] in wet scCO2 was examined at pressure (82 bar) as a function of water concentration and temperature (50 C and 75 C). Exposing brucite to anhydrous scCO2 at either temperature resulted in little or no detectable reaction over three days. However, addition of trace amounts of water resulted in partial carbonation of brucite into nesquehonite [MgCO3 3H2O] within a few hours at 50 C. By increasing water content to well above the saturation level of the scCO2, complete conversion of brucite into nesquehonite was observed. Tests conducted at 75 C resulted in the conversion of brucite into magnesite [MgCO3] instead, apparently through an intermediate nesquehonite step. Raman spectroscopy applied to brucite reacted with 18O-labeled water in scCO2 show it was incorporatedmore » into carbonate at relatively high concentration. This supports a carbonation mechanism with at least one step involving a direct reaction between the mineral and water molecules without mediation by a condensed aqueous layer.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1029068
Report Number(s):
PNNL-SA-78165
Journal ID: ISSN 0016-7037; GCACAK; 39947; KC0303020; TRN: US1105540
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 75; Journal Issue: 1; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CARBON DIOXIDE; CARBONATES; DIRECT REACTIONS; GEOLOGIC FORMATIONS; KINETICS; RAMAN SPECTROSCOPY; SATURATION; SILICATE MINERALS; STORAGE; TRACE AMOUNTS; WATER; X-RAY DIFFRACTION; carbon sequestration, mineralization, brucite; Environmental Molecular Sciences Laboratory

Citation Formats

Schaef, Herbert T., Windisch, Charles F., McGrail, B. Peter, Martin, Paul F., and Rosso, Kevin M. Brucite [Mg(OH2)] Carbonation in Wet Supercritical CO2: An in situ High Pressure X-Ray Diffraction Study. United States: N. p., 2011. Web. doi:10.1016/j.gca.2011.09.029.
Schaef, Herbert T., Windisch, Charles F., McGrail, B. Peter, Martin, Paul F., & Rosso, Kevin M. Brucite [Mg(OH2)] Carbonation in Wet Supercritical CO2: An in situ High Pressure X-Ray Diffraction Study. United States. doi:10.1016/j.gca.2011.09.029.
Schaef, Herbert T., Windisch, Charles F., McGrail, B. Peter, Martin, Paul F., and Rosso, Kevin M. Tue . "Brucite [Mg(OH2)] Carbonation in Wet Supercritical CO2: An in situ High Pressure X-Ray Diffraction Study". United States. doi:10.1016/j.gca.2011.09.029.
@article{osti_1029068,
title = {Brucite [Mg(OH2)] Carbonation in Wet Supercritical CO2: An in situ High Pressure X-Ray Diffraction Study},
author = {Schaef, Herbert T. and Windisch, Charles F. and McGrail, B. Peter and Martin, Paul F. and Rosso, Kevin M.},
abstractNote = {Understanding mechanisms and kinetics of mineral carbonation reactions relevant to sequestering carbon dioxide as a supercritical fluid (scCO2) in geologic formations is crucial to accurately predicting long-term storage risks. Most attention so far has been focused on reactions occurring between silicate minerals and rocks in the aqueous dominated CO2-bearing fluid. However, water-bearing scCO2 also comprises a reactive fluid, and in this situation mineral carbonation mechanisms are poorly understood. Using in situ high-pressure x-ray diffraction, the carbonation of brucite [Mg(OH)2] in wet scCO2 was examined at pressure (82 bar) as a function of water concentration and temperature (50 C and 75 C). Exposing brucite to anhydrous scCO2 at either temperature resulted in little or no detectable reaction over three days. However, addition of trace amounts of water resulted in partial carbonation of brucite into nesquehonite [MgCO3 3H2O] within a few hours at 50 C. By increasing water content to well above the saturation level of the scCO2, complete conversion of brucite into nesquehonite was observed. Tests conducted at 75 C resulted in the conversion of brucite into magnesite [MgCO3] instead, apparently through an intermediate nesquehonite step. Raman spectroscopy applied to brucite reacted with 18O-labeled water in scCO2 show it was incorporated into carbonate at relatively high concentration. This supports a carbonation mechanism with at least one step involving a direct reaction between the mineral and water molecules without mediation by a condensed aqueous layer.},
doi = {10.1016/j.gca.2011.09.029},
journal = {Geochimica et Cosmochimica Acta},
issn = {0016-7037},
number = 1,
volume = 75,
place = {United States},
year = {2011},
month = {11}
}