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 language | English |
|---|---|
| Pages (from-to) | 1199-1211 |
| Number of pages | 13 |
| Journal | Geochimica et Cosmochimica Acta |
| Volume | 69 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 1 Mar 2005 |
Fingerprint
ASJC Scopus subject areas
- Geochemistry and Petrology
Cite this
The dissolution rates of gibbsite in the presence of chloride, nitrate, silica, sulfate, and citrate in open and closed systems at 20°C. / Dietzel, M.; Böhme, G.
In: Geochimica et Cosmochimica Acta, Vol. 69, No. 5, 01.03.2005, p. 1199-1211.Research output: Contribution to journal › Article › Research › peer-review
}
TY - JOUR
T1 - The dissolution rates of gibbsite in the presence of chloride, nitrate, silica, sulfate, and citrate in open and closed systems at 20°C
AU - Dietzel, M.
AU - Böhme, G.
PY - 2005/3/1
Y1 - 2005/3/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=14844321636&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2004.08.027
DO - 10.1016/j.gca.2004.08.027
M3 - Article
VL - 69
SP - 1199
EP - 1211
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
SN - 0016-7037
IS - 5
ER -