Abstract
The dissolution of well crystallized gibbsite far at from equilibrium was studied in batch and mixed flow through reactors. The dissolution experiments were carried out between pH 2 and 6 in the presence of 10 mmol L-1 citrate, at pH 2 and 3 in the presence of 10 mmol L-1 chloride, nitrate, and sulfate, and at pH 2 and 3 in the presence of 1.5 mmol L-1 silica at 20°C. The dissolution rate of gibbsite, RAl (mol m-2 s-1), increases in the order of chloride ≈ nitrate < silica < sulfate ≈ citrate. In presence of silica, sulphate, and citrate dissolution is catalysed by the formation of aluminium complexes at the gibbsite surface (pH 2 and 3). From pH 2 to 3 no effect of RAl on hydrogen activity is predicted as singly coordinated surface sites at the edges of the platy gibbsite crystals, [≡AlOH2 +0.5] ≈ [≡AlOH], are almost saturated with protons. However at pH >3 dissolution is slowed by a decrease of [≡AlOH2+0.5]. Gibbsite dissolution rates measured in closed and open systems were identical within the experimental and analytical uncertainty. This observation indicates that gibbsite dissolution is a surface controlled process. If dissolution of gibbsite occurs close to equilibrium RAl values may be predicted by an approximately linear function of ΔGr.
Originalsprache | englisch |
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Seiten (von - bis) | 1199-1211 |
Seitenumfang | 13 |
Fachzeitschrift | Geochimica et Cosmochimica Acta |
Jahrgang | 69 |
Ausgabenummer | 5 |
DOIs | |
Publikationsstatus | Veröffentlicht - 1 März 2005 |
ASJC Scopus subject areas
- Geochemie und Petrologie