The dissolution rate of albite as a function of chemical affinity and the stoichiometry of activated complexes in aluminosilicate dissolution reactions

Conference · Wed Jan 01 00:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5690806

Oelkers, E H; Schott, J ^[1]

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1. Univ. Paul Sabatier, Toulouse (France). Lab. de Geochimie

The dissolution rate of aluminosilicate minerals is commonly believed to follow transition state theory with the assumption that the activated complex has the same Al/Si ratio as the dissolving mineral. To assess the validity of this assumption, the dissolution rate of albite was measured at more than 50 different solution saturation states and Al/Si ratios at pH 9 and 150 C in a titanium mixed flow reactor. All experiments were carried out in NaCl solutions with a constant ionic strength of 0.1 molal. Stoichiometric dissolution was observed in all experiments. In contrast with the behavior typically predicted from transition state theory, the measured dissolution rates are a strong function of chemical affinity (A) at far from equilibrium conditions (A < [minus]10 kcal/mol). This behavior is apparently a consequence of the effect of Al concentration on the overall rate of reaction. At constant A, the albite dissolution rate decreases dramatically with increasing Al concentration which indicates that this reaction may be controlled by an aluminum deficient activated complex. This result is consistent with the kaolinite dissolution rates at pH 2 and pH 7.8 reported by Devidal et al. (1992). It follows that the dissolution of all aluminosilicate minerals may be controlled by similar aluminum deficient activated complexes, and the rate of geochemical processes in the Earth may be far different from that deduced from the traditional extrapolation of dissolution rate data obtained in stoichiometric solutions at far from equilibrium conditions by assuming activated complexes with the same Al/Si ratios as the dissolving minerals.

• OSTI ID: 5690806
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
ALBITE
DISSOLUTION
ALUMINIUM COMPLEXES
ALUMINIUM SILICATES
CHEMICAL REACTIONS
MEASURING METHODS
PH VALUE
ROCK-FLUID INTERACTIONS
SODIUM CHLORIDES
ALKALI METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CHLORIDES
CHLORINE COMPOUNDS
COMPLEXES
FELDSPARS
HALIDES
HALOGEN COMPOUNDS
MINERALS
OXYGEN COMPOUNDS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SODIUM COMPOUNDS
152003* - Geothermal Data &amp; Theory- Rock-Water-Gas Interactions