The dissolution rates of gibbsite in the presence of chloride, nitrate, silica, sulfate, and citrate in open and closed systems at 20°C

M. Dietzel*, G. Böhme

*Corresponding author for this work

Research output: Contribution to journalArticle

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.

Original languageEnglish
Pages (from-to)1199-1211
Number of pages13
JournalGeochimica et Cosmochimica Acta
Volume69
Issue number5
DOIs
Publication statusPublished - 1 Mar 2005

ASJC Scopus subject areas

  • Geochemistry and Petrology

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