Mineral Metastability in the System Al2O3-SiO2-H2O: A Reply

Essene, Eric J.

doi:10.1346/ccmn.1994.0420114

Cited by 9 publications

(6 citation statements)

References 17 publications

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“…The measurements were reproducible, even though different batches of dawsonite were used (see Table 1) and the solutions remained oversaturated with respect to boehmite , which is a relatively stable aluminum phase at temperatures >90°C. Although diaspore is reported to be the most stable aluminum hydroxide under our experimental conditions (e.g., Essene et al, 1994), it is seldom observed, presumably due to kinetic constraints. It will not be considered further in this paper.…”

Section: Resultsmentioning

confidence: 73%

Dawsonite synthesis and reevaluation of its thermodynamic properties from solubility measurements: Implications for mineral trapping of CO2

Bénézeth

Palmer

Anovitz

et al. 2007

Geochimica et Cosmochimica Acta

134

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Section: Resultsmentioning

confidence: 73%

Dawsonite synthesis and reevaluation of its thermodynamic properties from solubility measurements: Implications for mineral trapping of CO2

Bénézeth

Palmer

Anovitz

et al. 2007

Geochimica et Cosmochimica Acta

134

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“…The Al 2 O 3 -H 2 O system in the solid phase is involved in the water cycle on Earth's crust and it has been extensively studied [1,2]. In particular, AlOOH has been observed in three different phases.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, AlOOH has been observed in three different phases. At atmospheric pressure, the α phase (Diaspore) is stable [1,2], while the δ phase becomes stable at high pressures [3,4]. Another structure is also found in nature, the γ phase (Boehmite), which is metastable [1,2].…”

Section: Introductionmentioning

confidence: 99%

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Stability of the different AlOOH phases under pressure

Cedillo¹,

Torrent²,

Cortona³

2016

J. Phys.: Condens. Matter

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The pressure effects on three different AlOOH structures (α, γ, and δ phases) are systematically analyzed by density functional theory with different exchange and correlation energy functional approximations, namely two local, two generalized-gradient approximation (GGA), and two GGA for solids (GGAsol). Phase stability, compressibility and hydrogen bond evolution are studied in a range of pressures from 0 to 30 GPa. In general, the use of GGAsol functionals is mandatory in order to have the correct phase stability order, a good description of the hydrogen bonds, and a close agreement with the experimental lattice parameters at the various pressures. Pressure-induced hydrogen-bond symmetrization is found in γ and δ phases at high compression, while the hydrogen bonds in the α phase remain asymmetric. A detailed analysis of the uncertainties on the values of the bulk moduli and their pressure derivative at zero pressure deduced by fitting calculated or experimental (P,V) data is also presented.

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“…3), whose solubility constant is significantly greater than those of diaspore, boehmite, and gibbsite, as calculated from thermodynamic data [33,34]. This dilute solid-solution model is supported by the fact that diaspore does not normally precipitate from aqueous solution under diagenetic conditions [35]. Although a number of experimental observations, particularly regarding the competition between goethite and hematite precipitation [32], can be explained by kinetic rather than thermodynamic considerations, the present model suggests that the maximum Al content in goethite [x(Al) ≈ 0.27]) is limited by the precipitation of gibbsite, in accordance with experimental results [32].…”

Section: "Primary Saturation" and Hypothetical End-membersmentioning

confidence: 79%

Solid-solute phase equilibria in aqueous solution: Fundamentals and applications

Königsberger¹

2013

Pure and Applied Chemistry

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Carbonates 1 Phase Transitions 1 Solutions 1 ThermodynamicsSolid binary carbonate phases often dissolve congruently in aqueous media, even when they are not stable under the prevailing conditions. From the thermodynamic point of view these dissolution reactions lead to a metastable equilibrium with fixed composition, when neither diffusion in the solid state nor recrystallization from the solution occurs. The solubility of natural huntite, CaMg3(C03)4, was studied potentiometrically at 50°C and I = 3.0 mol kg-' (Na)C104. Since it dissolved congruently the solubility constant log * . Amazingly enough phase equilibria of solid mixtures in aqueous media have seldom been studied in detail, although the corresponding reactions play an important role in geochemistry as well as in hydrometallurgy. Lippmann [S] described the aqueous solubility of binary mineral systems using the total solubility product and the mole fraction as master variables of phase diagrams. These diagrams are based on the solubility products of the pure end members and a simple electrostatic mixing model, but have in most cases not been verified experimentally. One of the reasons for this lack of scientific activity in an obviously interesting field is certainly the fact that the rates of heterogeneous ionic reactions are rather slow at temperatures between the freezing and the boiling point of water at ordinary pressure, and differing results have been obtained when equilibrium was approached from undersaturation and supersaturation respectively. A pertinent example are the contradictory results for the solubilities of magnesian calcites obtained by different research groups [6].In this paper the thermodynamic formalism for solid-solute ionic equilibria in the system CaC03 -MgC03 -H,O is presented with particular emphasis on phase transitions without diffusion in the solid state [7]. It is applied for the determination of the solubility constant, phase equilibria and free enthalpy of formation of huntite, CaMg3(CO&. This mineral occurs naturally although its decomposition into dolomite, CaMg(CO&, and magnesite, MgC03, is thermodynamically favoured.

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Mineral Metastability in the System Al₂O₃-SiO₂-H₂O: A Reply

Cited by 9 publications

References 17 publications

Dawsonite synthesis and reevaluation of its thermodynamic properties from solubility measurements: Implications for mineral trapping of CO2

Dawsonite synthesis and reevaluation of its thermodynamic properties from solubility measurements: Implications for mineral trapping of CO2

Stability of the different AlOOH phases under pressure

Solid-solute phase equilibria in aqueous solution: Fundamentals and applications

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