Modelling the solubility in Bayer liquors: A critical review and new models

Nortier, Patrice; Chagnon, P.; Lewis, Alison

doi:10.1016/j.ces.2011.03.004

Cited by 10 publications

(8 citation statements)

References 16 publications

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“…The broadening is not likely due to the existence of multiple aluminum species, because only Al(OH) 4 – is detected under these conditions with Raman spectroscopy (Figure ). ,,, …”

Section: Resultsmentioning

confidence: 99%

“…− is detected under these conditions with Raman spectroscopy (Figure 7). 25,47,48,51 Since the chemical shift change is small with increasing deuteroxide (Figure 6A), it could be argued that broadening of the peak in the deuterated solutions is caused by varying degrees of deuterium substitution on the aluminate ion. However, this is also unlikely because an increase in the fwhm is observed going from the 1:1 to the 0:1 H/D ratio experiments, where it is expected that the variance in the degree of deuterium substitution would be highest in the 1:1 H/D ratio experiment.…”

Section: Liquid State Nmr Andmentioning

confidence: 99%

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Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)₃) Crystallization from Alkaline Aqueous Solution

Krzysko

Graham

Dembowski

et al. 2022

ACS Earth Space Chem.

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Understanding molecular-scale factors governing the precipitation of aluminum hydroxides, such as gibbsite, under alkaline conditions is important for the formation of laterite deposits, as well as aluminum processing. However, mechanisms enabling tetrahedral aluminate ions to assemble into octahedral sites of the gibbsite lattice remain unclear. Formation of oligomeric complexes has been hypothesized as a critical intermediate step. Here, we report a study of gibbsite solubility in highly alkaline solutions using deuterium substitution to probe equilibrium and kinetic factors that could affect oligomeric intermediate formation, including the reactivity and the diffusivity of aluminate ions. When substituting sodium hydroxide with sodium deuteroxide, solution analysis shows a nearly 40% and 50% increase in gibbsite solubility in 2.4 and 3.3 mol·kg–1 total sodium solutions, respectively. Raman spectroscopy indicated that monomeric aluminate ions are the predominant species in solution irrespective of deuteration. However, both 27Al and 23Na nuclear magnetic resonance (NMR) spectroscopy revealed significant differences in chemical shifts in deuterated solutions, and analysis of 1H, 23Na, and 27Al diffusion coefficients with pulsed-field gradient, stimulated echo NMR spectroscopy shows a decrease in ion diffusivity with increasing total deuterium in solution, consistent with the notion of increasing strength in the hydrogen/deuterium bonding network. Because the relative change in 1H diffusion coefficients are commensurate with the difference in apparent solubility constants, there is evidence for an oligomeric intermediate whose steady-state concentration is maintained by the collision frequency of aluminate ions.

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“…The broadening is not likely due to the existence of multiple aluminum species, because only Al(OH) 4 – is detected under these conditions with Raman spectroscopy (Figure ). ,,, …”

Section: Resultsmentioning

confidence: 99%

Section: Liquid State Nmr Andmentioning

confidence: 99%

Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)₃) Crystallization from Alkaline Aqueous Solution

Krzysko

Graham

Dembowski

et al. 2022

ACS Earth Space Chem.

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“…Since the Al(OH) 4 – ion is the only important species in the low concentration of KOH solutions at temperatures less than 373.15 K, and the exact ionic species of aluminate are not clear at higher concentrations of KOH, some works are focused on the thermodynamic calculation of the system of the aluminate with low KOH concentrations by using the Pitzer theory. − In this paper, considering that the Al 2 O 3 ·3H 2 O crystallization region in the ternary phase diagram was important for the preparation of the aluminum hydroxide product from the complex system by using seeded precipitation, the measured solubility equilibrium data corresponding to the crystallization region of Al 2 O 3 ·3H 2 O at the low K 2 O concentration (below 30 wt %) were used to achieve model parameters by utilizing the Pitzer theory first, and then the equilibrium data were calculated with these model parameters. For the theoretical calculation, the solubility of Al 2 O 3 ·3H 2 O in aqueous solution containing excess OH – can be described by the following dissolution reaction, as shown in eq . For the ternary system K 2 O–Al 2 O 3 –H 2 O, only the K + , OH – , and Al(OH) 4 – ions are assumed to exist in the alkali solution at the low K 2 O concentration.…”

Section: Computational Modeling Sectionmentioning

confidence: 99%

Phase Equilibrium in the Ternary System K₂O–Al₂O₃–H₂O at 323.15, 333.15, 343.15, and 353.15 K

Luo

Xue

et al. 2020

J. Chem. Eng. Data

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Phase equilibrium of ternary system K2O–Al2O3–H2O is the key in realizing seeded precipitation process of aluminum hydroxide product from alkaline leaching solution in the alunite tailings metallurgical industry. However, little work has been carried out about the solubility of the K2O–Al2O3–H2O system, especially for the concentrated alkali solution region. The corresponding phase equilibria at 323.15, 333.15, 343.15, and 353.15 K were researched by using the isothermal dissolution method and the Pitzer ion-interaction model. The calculated Al2O3·3H2O solubilities corresponding to the crystallization region of Al2O3·3H2O in the ternary system at each temperature basically agree with experimental values when K2O concentration is below 30 wt %. Furthermore, the ternary system at each temperature contains two invariant points, three univariant isothermal dissolution curves, and five crystallization fields corresponding to Al2O3·3H2O (gibbsite), K2O·Al2O3·3H2O, KOH·H2O, Al2O3·3H2O + K2O·Al2O3·3H2O, and K2O·Al2O3·3H2O + KOH·H2O. According to the phase diagrams of the ternary system, it can be indicated that the low alkali concentration and temperature are in favor of the crystallization of Al2O3·3H2O, while the high alkali concentration and low temperature are beneficial to the crystallization of K2O·Al2O3·3H2O.

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“…Significant effort has been expended to model the solubility of aluminum solutions of the Bayer process in the hopes of increasing efficiency. 10,11,12 The plethora of modeling attempts found in the literature indicates the difficulty in satisfactorily modeling aluminum solubility and precipitation.…”

Section: Literature Reviewmentioning

confidence: 99%

Equilibrium studies of oxalate and aluminum containing solutions

Hay

King

Peters

et al. 2015

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Most of the OLI predictions for the oxalate concentrations in the sodium oxalate tests were much lower than the measured concentrations. For solutions with 5 M sodium or higher, the OLI predictions were 5-10X lower than the measured concentrations. The OLI modeling predictions for the aluminum concentrations in the gibbsite tests were generally ~20-30% lower or higher than the measured concentrations depending on the test method. Interestingly, the OLI predictions match reasonably well with the average aluminum concentration from the two test methods.

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Modelling the solubility in Bayer liquors: A critical review and new models

Cited by 10 publications

References 16 publications

Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)₃) Crystallization from Alkaline Aqueous Solution

Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)₃) Crystallization from Alkaline Aqueous Solution

Phase Equilibrium in the Ternary System K₂O–Al₂O₃–H₂O at 323.15, 333.15, 343.15, and 353.15 K

Equilibrium studies of oxalate and aluminum containing solutions

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Modelling the solubility in Bayer liquors: A critical review and new models

Cited by 10 publications

References 16 publications

Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)3) Crystallization from Alkaline Aqueous Solution

Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)3) Crystallization from Alkaline Aqueous Solution

Phase Equilibrium in the Ternary System K2O–Al2O3–H2O at 323.15, 333.15, 343.15, and 353.15 K

Equilibrium studies of oxalate and aluminum containing solutions

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Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)₃) Crystallization from Alkaline Aqueous Solution

Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)₃) Crystallization from Alkaline Aqueous Solution

Phase Equilibrium in the Ternary System K₂O–Al₂O₃–H₂O at 323.15, 333.15, 343.15, and 353.15 K