Heavy Metals as Impurities in the Bayer Production Cycle of the Aluminum Hydroxide from Sierra Leone Bauxite. Preliminary Study

Dobra, Gheorghe; Iliev, S.; Cotet, Lucian; Boiangiu, Alina; Hulka, Iosif; Kim, Lidia; Alina, Catrina Gina; Filipescu, Laurentiu

doi:10.17516/1999-494x-0296

Cited by 7 publications

(5 citation statements)

References 8 publications

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“…The lanthanides and (additionally) scandium and yttrium content in a fluid and solid phases from the aluminum hydroxide production cycle were measured after the onset of all research facilities to develop of a technology for obtaining dry, milled and classified aluminum hydroxide. Representative samples of bauxite concentrated and spent Bayer liquors and different sorts of aluminum hydroxide dried, milled and classified were collected in many rounds for different purposes [65,66]. From this large number of samples, there were selected two sets of data representing the best results concerning: the mineralogy of both Sierra Leone bauxite (BA1, BA2) and bauxite residues (BR1, BR2), the composition of concentrated Bayer liquor and, impurity concentration in some of in the commercial grades of aluminum hydroxide.…”

Section: Experimental Part Materialsmentioning

confidence: 99%

“…Bauxite from Sierra Leone is still a little-known raw material for the Bayer's alumina production, even if the first information about its composition and petrography were published many years ago [61,62]. In the last 10 years, only a few papers were published by Alum SA, Tulcea, Romania, mainly related to the use of this bauxite as raw material for the production of Bayer alumina [63][64][65][66]. For a careful analysis of the minor elements from materials with complex mineralogy, such as the bauxite and bauxite residue, the literature recommends two ways of preliminary treatment: alkali fusion followed by the acid digestion [67][68][69], respectively, the acid baking followed by extraction with water [70][71][72].…”

Section: Introductionmentioning

confidence: 99%

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Lanthanides as impurities in the Bayer production cycle of the aluminum hydroxide from Sierra Leone bauxite

Kim¹,

Dobra²,

Isopescu³

et al. 2022

RJEEC

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This paper is describing a careful study of the content and distribution of rare elements in the fluid and solid phases involved in dry and classified aluminum hydroxide production through the Bayer process at Alum SA, Tulcea, Romania. The source of rare elements in the Bayer process is the bauxite from Sierra Leone, a particular type of aluminous goethite-lateritic bauxite, not fully studied yet. Rare earth elements are fairly abundant in nature, but their distribution is very large, encompassing hundreds of types of minerals where the rare element appears as minor crystalline and amorphous compounds, solid solutions, or as ions adsorbed on the surface of common natural rocks. This study data show that Sierra Leone bauxite has only a small content in rare elements. Mainly, only the scandium and cerium concentrations (44.84 mg/kg and 11.49 mg/kg in bauxite residue) may reach the expected values required for eventual valorization. On the Bayer cycle, the rare metals enter with bauxite and concentrate in bauxite residues. Solubility of the rare element compounds in the Bayer process fluid phases is close to zero. In the final product, the aluminum hydroxide dried, milled and classified grades, the rare metals appear only as occlusion contaminants.

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Section: Experimental Part Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Lanthanides as impurities in the Bayer production cycle of the aluminum hydroxide from Sierra Leone bauxite

Kim¹,

Dobra²,

Isopescu³

et al. 2022

RJEEC

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“…The removal of other sources of AH has been done by several approaches, such as crystallization, washing with water or weak acid to reduce the amount of the impurities in the samples [5][6][7][8][9][10]. Acetic acid has been used to remove sodium compounds from AH in several work, however, the concentration of acetic acid is rather high, up to 5 N or higher is required to get the designated removal effects [11][12].…”

Section: Introductionmentioning

confidence: 99%

PURIFICATION OF TAN RAI ALUMINUM HYDROXIDE WITH ACETIC ACID AND PREPARATION OF HIGH PURE NANOSIZE Α-Alumina

2022

Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.

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Gibbsite is the most common form of aluminum hydroxide (AH) as commercial product of Bayer process. However, it usually contains some impurities such as sodium, iron, calcium, and silicon compounds that may not meet requirements for preparation of advanced materials or functional ones which need very high pure raw materials. In this paper, we present some results on the purification of commercial AH from Tan-rai alumina company (Vietnam) using dilute acetic acid solution. The removal yields of 93.19, 91.75, 100, and 86.03% are obtained for Na2O, CaO, Fe2O3, and SiO2 respectively, whereas the recovery of clean AH is almost quantitative. The clean AH is then used for preparation of high pure nanosize α-alumina via chemical processes of dissolution, precipitation ammonium aluminium carbonate hydroxide (AACH) with ammonium carbonate solution. After washing the excess reagents, the precipitate of AACH is then decomposed at elevated temperature to get high pure nanosize α-alumina. The obtained product rather regular and most of particles are not agglomerated. The laser scattering data on the prepared sample show that the particle sizes of the prepared α-alumina from 60 – 90 nm are obtained which are in good agreement with the data from XRD and morphology measurements. The α-alumina structure of the final product is confirmed by the XRD measurement data.

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“…Aluminum hydroxide, as an intermediary wet product (gibbsite, Al2O3•3H2O), is industrially produced by Bayer process from different kinds of bauxites. The gibbsite quality, particle size, crystallinity and crystals morphology are strongly influenced by the Bayer process parameters [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Short review on mechanical activation in non-metallurgical alumina production

Kim¹,

Dobra²,

Isopescu³

et al. 2022

RJEEC

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The terms mechano-chemistry and mechanical activation of solid materials were introduced in chemical literature by Ostwald at the beginning of the XX century. Both terms cover a whole range of interconnected phenomena taking place during the mechanical action on solids or their separate parts participating in chemical reactions, phase transitions, mixing and creating composite materials, alloying and crystal growth in the solid state, deformation and changing physical and thermal properties, all of them at low temperature. The common effects of the mechanical activation on solid material are fracturing and reduction of particle sizes, generation of new reactive surfaces, diffusion of atoms of the reactant phase through the product phase, and quite significantly, accumulating energy in crystalline or amorphous structure (enough twists in atomic and molecular networks, tensions in atomic bond and active sites to trigger the nucleation of new phases). Mechanical activation is very used to produce all clean alumina mineralogical phases with uniform particle size dimensions from nano to macro size. Also, mechanical activation may extend the specific surface of some minerals, enhancing the yields in the solid-liquid extraction process. With adequate precursors, all phase transitions from amorphous to alfa α-Al2O3 can be carried out on the same route as in thermally activated alumina, but some other routes, impossible by thermal activation, might be followed. The difference between the two activation ways is that mechanical activation is made at room temperature.

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Heavy Metals as Impurities in the Bayer Production Cycle of the Aluminum Hydroxide from Sierra Leone Bauxite. Preliminary Study

Cited by 7 publications

References 8 publications

Lanthanides as impurities in the Bayer production cycle of the aluminum hydroxide from Sierra Leone bauxite

Lanthanides as impurities in the Bayer production cycle of the aluminum hydroxide from Sierra Leone bauxite

PURIFICATION OF TAN RAI ALUMINUM HYDROXIDE WITH ACETIC ACID AND PREPARATION OF HIGH PURE NANOSIZE Α-Alumina

Short review on mechanical activation in non-metallurgical alumina production

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