Dissolution kinetics of diopside as a function of solution saturation state: Macroscopic measurements and implications for modeling of geological storage of CO2 | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Dissolution kinetics of diopside as a function of solution saturation state: Macroscopic measurements and implications for modeling of geological storage of CO2

Type de publication:

Journal Article

Source:

Geochimica Et Cosmochimica Acta, Volume 74, Ticket 9, p.2615-2633 (2010)

ISBN:

0016-7037

Numéro d'accès:

ISI:000276493900006

URL:

http://www.sciencedirect.com/science/article/pii/S0016703710000621

Mots-clés:

UMR 7154 ; Minéralogie

Résumé:

Measurements of the dissolution rate of diopside (r) were carried out as a function of the Gibbs free energy of the dissolution reaction (Delta G(r)) in a continuously stirred flow-through reactor at 90 degrees C and pH(90 degrees C) = 5.05. The overall relation between r and Delta G(r) was determined over a free energy range of -130.9 < Delta G(r) < -47.0 kJ mol(-1). The data define a highly non-linear, sigmoidal relation between r and Delta G(r). At far-from-equilibrium conditions (Delta G(r) <= -76.2 kJ mol(-1)), a rate plateau is observed. In this free energy range, the rates of dissolution are constant, independent of [Ca], [Mg] and [Si] concentrations, and independent of Delta G(r). A sharp decrease of the dissolution rate (similar to 1 order of magnitude) occurs in the transition Delta G(r) region defined by -76.2 < Delta G(r) <= -61.5 kJ mol(-1). Dissolution closer to equilibrium (Delta G(r) > -61.5 kJ mol(-1)) is characterised by a much weaker inverse dependence of the rates on Delta G(r). Modeling the experimental r-Delta G(r), data with a simple classical transition state theory (TST) law as implemented in most available geochemical codes is found inappropriate. An evaluation of the consequences of the use of geochemical codes where the r-Delta G(r), relation is based on basic TST was carried out and applied to carbonation reactions of diopside, which, among other reactions with Ca- and Mg-bearing minerals, are considered as a promising process for the solid state sequestration of CO2 over long time spans. In order to take into account the actual experimental r-Delta G(r), relation in the geochemical code that we used, a new module has been developed. It reveals a dramatic overestimation of the carbonation rate when using a TST-based geochemical code. This points out that simulations of water-rock-CO2 interactions performed with classical geochemical codes should be evaluated with great caution. (C) 2010 Elsevier Ltd. All rights reserved.

Notes:

Daval, Damien Hellmann, Roland Corvisier, Jérôme Tisserand, Delphine Martinez, Isabelle Guyot, Francois