In situ AFM investigation of heterogeneous nucleation and growth of sodium oxalate on industrial gibbsite surfaces in concentrated alkaline solution

Fu, Weng; Vaughan, James; Gillespie, Alistair

doi:10.1016/j.ces.2014.12.057

Cited by 6 publications

(2 citation statements)

References 14 publications

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“…The crystal habit of sodium oxalate is determined by the three faces, {200}, {110}, and {001}. Fu et al, who studied Na 2 C 2 O 4 crystallization on gibbsite crystals in synthetic Bayer liquor, suggested that the order of morphological importance (MI) of these faces could be as follows: MI{110} > MI{200} > MI{001}. The MI order could be inversely proportional to the growth rate of individual faces.…”

Section: Resultsmentioning

confidence: 99%

Mechanisms of Polyacrylate Modified Sodium Oxalate Crystallization from Highly Alkaline Solutions

Vaughan

Gillespie

et al. 2016

Crystal Growth & Design

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The shape changes of sodium oxalate (Na2C2O4) crystals in the presence of polyacrylic acids (PAA) with different molecular weights (1800, 5100, 450 000, 1 250 000 g/mol) and propionic acid (74 g/mol) was investigated in a highly alkaline solution (5 M NaOH). Over the entire concentration range tested (0–100 mg/L), propionic acid had no influence on Na2C2O4 shape, indicating that the number of carboxylate functional groups is not the vital factor for Na2C2O4 shape control, despite playing a role in the adsorption. In contrast, with increasing PAA concentrations, Na2C2O4 crystals were significantly modified through distinct shape changes proceeding through a coexisting family of rods, bundles, flower-like structures, irregular spherulites, and eventually spherulites. PAA anions with medium molecular weights (1800, 5100 g/mol) were the most effective in promoting the spherulitic shape. Thus, the mechanisms of Na2C2O4 shape changes can be attributed to PAA adsorption on Na2C2O4 surfaces and their subsequent incorporation into the Na2C2O4 crystal matrix. PAA adsorption is responsible for the inhibition of step train growth on prismatic {110} and {200} faces and nuclei propagation on their top {001} faces. PAA incorporation can lead to multistep-branching growth based on a noncrystallographic crystal branching model.

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Section: Resultsmentioning

confidence: 99%

Mechanisms of Polyacrylate Modified Sodium Oxalate Crystallization from Highly Alkaline Solutions

Vaughan

Gillespie

et al. 2016

Crystal Growth & Design

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“…In this study, in situ atomic force microscopy (AFM) was employed to study the gibbsite growth on basal (001) face and prismatic (100) face of industrial gibbsite crystalsto promote the current understanding of gibbsite growth mechanism.Considering that that the glass window of AFM cantilever holder cannot resist highly caustic Bayer solution (~ 5M NaOH), the synthetic liquor used for in situ AFM investigation contains4M NaCl and 1M NaOH, supersaturated in aluminate at 25°C (Fu et al, 2015a;Fu et al, 2015b). Although thecomposition of this synthetic liquor is different from industrial Bayer liquor, both of liquors provide a high ionic strength and alkaline solutionfor gibbsite crystallization, in which the predominant anion species for aluminium are (Fu et al, 2015a;Fu et al, 2015b;Sposito, 1996).…”

Section: Introductionmentioning

confidence: 99%

In situ AFM investigation of gibbsite growth in high ionic strength, highly alkaline, aqueous media

Vaughan

Gillespie

2016

Hydrometallurgy

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In situ atomic force microscopy (AFM) was used to study the growth mechanism of the gibbsite basal (001) face and prismatic (100) face in high ionic strength () and highly alkaline solution (pH=13.4). The height of the steps on the gibbsite (001) faces can vary from less than one nanometre (elementary steps) to several nanometres (microsteps) and finally to dozens of nanometres (macrosteps). The lateral advancement rates of micro/macrosteps arerelated to the height of steps. Step coalescence occurs during lateral advancement, driven by Ostwald ripening. There are three possible pathways for the formation of micro/macrosteps on basal (001) face, all of which are controlled by layer-by-layer growth mechanism. Gibbsite structure suggests that the frequent and random formation of the elementary steps on basal (001) face can be attributed to weak inter-layer hydrogen bonds along the c-axis of gibbsite unit cell. The prismatic (100) faces are characterised by microstep trains along gibbsite [001] direction. These microsteps grow higher along gibbsite [100] direction, advance laterally and step coalescence also occurs. Two dimensional islands often form on the terrace adjacent to the edges of micro/macrosteps, suggesting that the step edge should be a preferred site for island nucleation due to the Ehrlich-Schwoebel effect.

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Australian Hydrometallurgy Research and Development

Vaughan

Peng

et al. 2018

The Minerals, Metals &Amp; Materials Series

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In situ AFM investigation of heterogeneous nucleation and growth of sodium oxalate on industrial gibbsite surfaces in concentrated alkaline solution

Cited by 6 publications

References 14 publications

Mechanisms of Polyacrylate Modified Sodium Oxalate Crystallization from Highly Alkaline Solutions

Mechanisms of Polyacrylate Modified Sodium Oxalate Crystallization from Highly Alkaline Solutions

In situ AFM investigation of gibbsite growth in high ionic strength, highly alkaline, aqueous media

Australian Hydrometallurgy Research and Development

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