Original paper

Thermodynamic properties of the aluminate ion and of bayerite, boehmite, diaspore and gibbsite

Verdes, Giles; Gout, Robert; Castet, Sylvie

European Journal of Mineralogy Volume 4 Number 4 (1992), p. 767 - 792

57 references

published: Aug 11, 1992
manuscript accepted: Jan 16, 1992
manuscript received: Aug 19, 1991

DOI: 10.1127/ejm/4/4/0767

BibTeX file

ArtNo. ESP147050404009, Price: 29.00 €

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Abstract A critical review of the literature concerning the solubility of aluminium hydroxides and oxyhydroxides has revealed some problems concerning the measurements in alkaline solutions ; in addition, it has led us to regard the solubility measurements of gibbsite in acid solutions as being very questionable. As a result of this review, solubility measurements have been made in weakly concentrated alkaline solutions (which allow for easy thermodynamic modelling) for : - synthetic bayerite: dissolution and precipitation between 21 and 65°C ; - synthetic gibbsite: dissolution between 21 and 70°C ; - synthetic boehmite: dissolution and precipitation between 70 and 300°C ; - natural diaspore: dissolution between 130 and 300°C. Our measurements permit the determination of the solubility products of these minerals with good accuracy and allow for the calculation of their thermodynamic properties as well as of the Gibbs free energy of formation of the aluminate ion, Al(OH)4. The following values are proposed for the Gibbs free energy of formation at 298.15 K : Al(OH)4: -1 305.42 kJ/mol ; gibbsite: -154.889 kJ/mol ; bayerite: -1 149.80 kJ/mol ; boehmite: -917.82 kJ/mol ; diaspore: -924.59 kJ/mol. Therefore, we can propose that the order of increasing stability of the aluminium hydroxides and oxyhydroxides at 25°C is : diaspore > boehmite ~ gibbsite > bayerite


solubilitythermodynamic propertiesaluminiumhydroxideoxyhydroxidebayeriteboehmitediasporegibbsite