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Issue 42, 2013
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A mechanistic understanding of plagioclase dissolution based on Al occupancy and T–O bond length: from geologic carbon sequestration to ambient conditions

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Abstract

A quantitative description of how the bulk properties of aluminosilicates affect their dissolution kinetics is important in helping people understand the regulation of atmospheric CO2 concentration by silicate weathering and predict the fate and transport of geologically sequestered CO2 through brine–rock interactions. In this study, we employed a structure model based on the C[1 with combining macron] space group to illustrate how differences in crystallographic properties of aluminosilicates, such as T–O (Tetrahedral site–Oxygen) bond length and Al/Si ordering, can result in quantifiable variations in mineral dissolution rates. The dissolution rates of plagioclases were measured under representative geologic carbon sequestration (GCS) conditions (90 °C, 100 atm of CO2, 1.0 M NaCl, and pH ∼ 3.1), and used to validate the model. We found that the logarithm of the characteristic time of the breakdown of Al–O–Si linkages in plagioclases follows a good linear relation with the mineral's aluminum content (nAl). The Si release rates of plagioclases can be calculated based on an assumption of dissolution congruency or on the regularity of Al/Si distribution in the constituent tetrahedra of the mineral. We further extended the application of our approach to scenarios where dissolution incongruency arises because of different linkage reactivities in the solid matrix, and compared the model predictions with published data. The application of our results enables a significant reduction of experimental work for determining the dissolution rates of structurally related aluminosilicates, given a reaction environment.

Graphical abstract: A mechanistic understanding of plagioclase dissolution based on Al occupancy and T–O bond length: from geologic carbon sequestration to ambient conditions

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Publication details

The article was received on 28 Jun 2013, accepted on 21 Aug 2013 and first published on 21 Aug 2013


Article type: Paper
DOI: 10.1039/C3CP52722K
Citation: Phys. Chem. Chem. Phys., 2013,15, 18491-18501
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    A mechanistic understanding of plagioclase dissolution based on Al occupancy and T–O bond length: from geologic carbon sequestration to ambient conditions

    Y. Yang, Y. Min and Y. Jun, Phys. Chem. Chem. Phys., 2013, 15, 18491
    DOI: 10.1039/C3CP52722K

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