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Issue 11, 2011
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The effects of initial acetate concentration on CO2brine-anorthite interactions under geologic CO2 sequestration conditions

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Abstract

Acetate is one of the most abundant organic compounds in many formation waters and is likely to be present in deep saline aquifers suitable for geologic CO2 sequestration (GCS). This work studied the effect of initially present acetate on the dissolution of anorthite (CaAl2Si2O8) and on subsequent secondary mineral precipitation under GCS conditions (35 °C and 74.8 atm). Anorthite was chosen as a model mineral because of the abundance of feldspar in clayey sandstones and the possibility of metal carbonation. In this study, acetate was found to decrease the cumulative aqueous concentrations of Al, Si, and Ca upon CO2 injection by inhibiting anorthite dissolution and increasing the amount of secondary mineral precipitates. The extent of the effect of acetate on metal concentration changes was element-specific (Al > Si > Ca), and the effect was found to be more significant in systems with lower salinity and lower pH. For anorthite dissolution, acetic acid inhibited the proton-mediated decomposition of the Al/Si-containing feldspar framework, while acetate anions may have facilitated the ion-exchange between interstitial Ca and aqueous cations. For secondary mineral precipitation, stoichiometry analysis of aqueous metal concentrations suggested the formation of Al-containing mineral(s). The presence of kaolinite as a secondary mineral was confirmed using high resolution transmission electron microscopy's electron diffraction data. An increase in the relative amount of precipitation due to the initial presence of acetate was suggested by mass balancing and verified on the cleaved anorthite surfaces by atomic force microscopy analysis. These results provide new insights for understanding and predicting GCS system evolution upon scCO2 injection in the initial presence of acetate.

Graphical abstract: The effects of initial acetate concentration on CO2–brine-anorthite interactions under geologic CO2 sequestration conditions

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Publication details

The article was received on 04 Jun 2011, accepted on 08 Aug 2011 and first published on 21 Sep 2011


Article type: Paper
DOI: 10.1039/C1EE01890F
Citation: Energy Environ. Sci., 2011,4, 4596-4606
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    The effects of initial acetate concentration on CO2brine-anorthite interactions under geologic CO2 sequestration conditions

    Y. Yang, C. Ronzio and Y. Jun, Energy Environ. Sci., 2011, 4, 4596
    DOI: 10.1039/C1EE01890F

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