Thermodynamic determination of the stability area of boehmite in Al2O3-Na2O-H2O and Al2O3-H2O systems

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dc.contributor.author Panias, D en
dc.contributor.author Paspaliaris, I en
dc.date.accessioned 2014-03-01T01:48:48Z
dc.date.available 2014-03-01T01:48:48Z
dc.date.issued 1999 en
dc.identifier.issn 00442658 en
dc.identifier.uri http://hdl.handle.net/123456789/25598
dc.relation.uri http://www.scopus.com/inward/record.url?eid=2-s2.0-0033349647&partnerID=40&md5=a235b76c48d44e47700051d122bf1f24 en
dc.subject.other Alumina en
dc.subject.other Crystallization en
dc.subject.other Phase transitions en
dc.subject.other Reaction kinetics en
dc.subject.other Sodium compounds en
dc.subject.other Supersaturation en
dc.subject.other Thermodynamic stability en
dc.subject.other Boehmite en
dc.subject.other Sodium hydroxide en
dc.subject.other Bauxite deposits en
dc.title Thermodynamic determination of the stability area of boehmite in Al2O3-Na2O-H2O and Al2O3-H2O systems en
heal.type journalArticle en
heal.publicationDate 1999 en
heal.abstract In the system Al2O3-Na2O-H2, boehmite (γ-AlOOH) is considered to be a stable phase at temperatures higher than 100 °C. At lower temperatures the stable phase is either gibbsite or bayerite (Al(OH)3). This observation is based on previous experimental findings concerning the crystallization of the various aluminum hydroxides or oxidehydroxides phases during aluminum hydrolysis or aluminum oxide hydroxylation in aqueous systems. In this work a thermodynamic analysis of the transformation reaction of gibbsite to boehmite is presented. This analysis has shown that boehmite is the thermodynamically stable phase in the system Al2O3-H2O at temperatures as low as 59.9±6.6 °C. In the system Al2O3Na2O-H2O, it has been proved that the stability area of boehmite depends on the sodium hydroxide concentration. It is extended to the lower temperatures as the sodium hydroxide concentration increases. In the case of a 6 m sodium hydroxide solution, boehmite can be considered as a stable phase at temperatures as low as 49.4±6.6 °C. The disagreement between the conclusions of the thermodynamic analysis and the previous experimental findings is attributed to the significant kinetic inhibitions of the chemical reactions taking place during boehmite crystallization under atmospheric conditions. Finally, in this paper a procedure to calculate theoretically the water activity in supersaturated sodium aluminate solutions based on the Bromley monoparametric equation is presented. For the first time, a value for the characteristic constant B of the Bromley equation for NaAl(OH)4 is presented here. en
heal.publisher Verlag fuer Kunst und Touristik GmbH, Leipzig, Germany en
heal.journalName Erzmetall: Journal for Exploration, Mining and Metallurgy en
dc.identifier.volume 52 en
dc.identifier.issue 11 en
dc.identifier.spage 585 en
dc.identifier.epage 595 en

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