Soda Incorporation During Hydrate Precipitation

Vernon, Chris; Loh, Joanne; Lau, Daniel; Stanley, Andrew

doi:10.1007/978-3-319-48176-0_83

Cited by 3 publications

(3 citation statements)

References 9 publications

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“…But, the process control parameters should be permanently monitored, because the contamination mechanism, also, includes auto-generation steps of the contamination sources, due to the large and frequent fluctuations in supersaturation along the aluminates decomposition line. Al the experimental data are in good agreement with published literature on this subject [7][8][9][10][11][12].…”

Section: Scanned Particle Insupporting

confidence: 89%

“…This ultimate advantage has led to the application of SEM microscopy coupled with EDX spectroscopy to the analysis of non milled and milled aluminum hydroxide samples [6]. The mechanism of contamination aluminum hydroxide with occluded impurities is simple and is taking place in correlation with three conditions coming from understanding the course of any crystallization process a) the presence of micron size particles in the supersaturated Bayer liquors due to the poor working of red filtration, and especially due to the poor quality of the filtering material -the freshly precipitated tricalcium aluminate; b) the fluctuation of supersaturation (control by the temperature-concentration relationship) in all stages of nucleation, agglomeration and growth of the particles in decomposition line of sodium aluminate, but especially, in the agglomeration stage; c) the crystallinity of the mineralogical phases and the share of amorphous particles fraction in the small size bauxite residue particles, conveyed by super-concentrated liquors in the crystallizing vessels [7][8][9][10][11][12][13].…”

Section: Resultsmentioning

confidence: 99%

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Aluminum Hydroxide Impurities Occlusions and Contamination Sources

Dobra¹,

Garcia-Granda²,

Iliev³

et al. 2020

Rev. Chim.

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This paper is reporting the data concerning impurities occlusion in the dried, milled and classified aluminum hydroxide, the sources of contamination and the ways to control the purity of classified aluminum hydroxide as raw material for special aluminas. Mainly, all the micronic size particles, floating in the super-saturated Bayer liquors, are potential sources of occluded impurities in the aluminum hydroxide particles. There are several mechanisms for embedding the impurities in crystalline substances. Of these, most probable ones in the Bayer alumina process are: a) occlusion of the spent liquor drops containing impurities inside the polycrystalline aluminum hydroxide congregates; b) hetero-nucleation of aluminum hydroxide on the surface of particles or colloids containing one or more impurities (the foreign particles are seized inside a crystals or inside of a crystalline multi-particulate association); c) incorporation of available ions or molecule reactive fragments in the poor crystalline structures of aluminum hydroxide after nucleation, during different growth stages of all already aggregated particles, under certain super-saturations. d) building up bridges between the scanty aggregated particles or filling the inside hollows of these aggregates with new quickly crystallized material, including the particulate impurities, mainly, during large fluctuations of the super-saturation. Using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy EDS (Apollo SSD detector, EDAX), the contributions of each of these mechanisms can be investigated simply and assumed from the collected data. It was shown that well crystallized phases originating directly from bauxite (like the aluminum substituted goethite and substituted hematite, rutile or quartz), as well as the well as the crystallized new born phases during specific Bayer reactions (like cancrinite, are not promoting directly the impurities occlusion. Poor crystalline phases (like sodalite and katoite or other secondary phases and their micronic size fragments are really sustaining impurities occlusion through all the acknowledged mechanisms.

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Section: Scanned Particle Insupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Aluminum Hydroxide Impurities Occlusions and Contamination Sources

Dobra¹,

Garcia-Granda²,

Iliev³

et al. 2020

Rev. Chim.

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“…It was later proved that there is an adsorption layer with a thickness of 0.3 to 10 nm on the surface of the seed in an aluminate solution using modern methods of analysis carried out by Vernon et al [32,33]. Although the nature of this layer is not completely clear, there are assumptions that it consists of polymer ions [25], and Vernon et al [32] suggest that this adsorption layer consists of sodium cations.…”

Section: Table 3 Results Of the Processing Of The Curves Inmentioning

confidence: 99%

Enhanced Precipitation of Gibbsite from Sodium Aluminate Solution by Adding Agglomerated Active Al(OH)<sub>3</sub> Seed

Shoppert¹,

Valeev²,

Alekseev³

et al. 2022

Preprint

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The addition of active seed for increasing the precipitation rate leads to the formation of fine Al(OH)3 particles that complicates separation of solid from the mother liquor. In this study, the enhanced precipitation of coarse Al(OH)3 from sodium aluminate solution using active agglomerated seed was investigated. Aluminum salt (Al2(SO4)3) were used for active agglomerated seed precipitation at the initial of the process. About 50% of precipitation rate was obtained when these agglomerates were used as a seed in the amount of 20 g L–1 at 25 °C within 10 h. The agglomerated active seed and precipitate samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). SEM images showed that agglomerates consist of flake-like particles that can be stick together by bayerite (β-Al(OH)3) acting as a binder. The precipitation temperature above 35 °C and the high concentration of free alkali (αk &gt; 3) lead to the agglomerates refinement that can be associated with the bayerite dissolution.

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Customer Impacts of Na2O and CaO in Smelter Grade Alumina

Lindsay¹

2012

Light Metals 2012

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Soda Incorporation During Hydrate Precipitation

Cited by 3 publications

References 9 publications

Aluminum Hydroxide Impurities Occlusions and Contamination Sources

Aluminum Hydroxide Impurities Occlusions and Contamination Sources

Enhanced Precipitation of Gibbsite from Sodium Aluminate Solution by Adding Agglomerated Active Al(OH)<sub>3</sub> Seed

Customer Impacts of Na2O and CaO in Smelter Grade Alumina

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