Parameters Affecting the Precipitation of Al Phases from Aluminate Solutions of the Pedersen Process: The Effect of Carbonate Content

Marinos, Danai; Vafeias, Michail; Sparis, Dimitris; Kotsanis, D.; Balomenos, Efthymios; Panias, D.

doi:10.1007/s40831-021-00403-w

Cited by 5 publications

(5 citation statements)

References 17 publications

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“…3 and 4, this can perhaps be attributed to the precipitation and aging being conducted at elevated temperatures. A study [23] has shown that temperatures over 40 • C do favor dawsonite formation. In the case of test no.…”

Section: Precipitation Of Aluminum Tri-hydroxidementioning

confidence: 99%

“…The most notable outcomes from the ENSUREAL studies were the observations of the formation of a calcium-containing passivation layer around the slag grains, limiting the extraction of Al during leaching [21]. Further, leaching solutions with a Na 2 CO 3 concentration higher than 100 g/L were observed to promote dawsonite [NaAlCO 3 (OH) 2 ] precipitation over the desired Al tri-hydroxides gibbsite and bayerite [22][23][24]. Additionally, it was noted that the precipitation process had to be a combination of carbonation and aging (allowing the precipitate to sit in solution for at least 24 h after carbonation) to convert boehmite to bayerite and gibbsite [9,23,24].…”

Section: Introductionmentioning

confidence: 99%

“…Further, leaching solutions with a Na 2 CO 3 concentration higher than 100 g/L were observed to promote dawsonite [NaAlCO 3 (OH) 2 ] precipitation over the desired Al tri-hydroxides gibbsite and bayerite [22][23][24]. Additionally, it was noted that the precipitation process had to be a combination of carbonation and aging (allowing the precipitate to sit in solution for at least 24 h after carbonation) to convert boehmite to bayerite and gibbsite [9,23,24]. Furthermore, other studies [17,25] have reported that elevated temperatures exceeding 60 • C promote gibbsite formation.…”

Section: Introductionmentioning

confidence: 99%

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Investigating Aluminum Tri-Hydroxide Production from Sodium Aluminate Solutions in the Pedersen Process

et al. 2022

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This study investigates applying the principles of the long-discontinued Pedersen process as a possible route for producing metallurgical grade alumina from low-grade and secondary feed materials. The investigation focused on the hydrometallurgical steps in the process, namely leaching, desilication, and precipitation, and adapting it to valorize bauxite residue. The test material used was a calcium–aluminate slag made by the smelting-reduction of a mixture of bauxite residue (dewatered red mud) and a calcium-rich bauxite beneficiation by-product. Samples of the slag were leached in a 1 L jacketed glass reactor with Na2CO3 solution, varying Na2CO3 concentration and leaching time. Additionally, different approaches to leaching involving mechanical treatment of the leached slag and re-leaching using either fresh or recycled solution were also explored. The desilication step was carried out by treating the leachate solution with powdered CaO, varying the amounts of CaO used. Finally, the desilicated leach solution was sparged with a CO2 gas mixture, after which the precipitate was allowed to age in the solution. The carbonation and aging temperatures and times were varied. As much as 67% of the Al was leached from the slag. The desilication process successfully removed 88% of the Si. The precipitation process produced a product composed mostly of bayerite [Al(OH)3], but some tests had considerable amounts of the unwanted phase dawsonite [NaAlCO3(OH)2]. The results indicated that the highest Al recovery was obtained using low concentrations of Na2CO3 solutions, and aluminum tri hydroxide is formed from these solutions at low temperatures at a fast rate compared to higher solution concentrations and temperatures.

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Section: Precipitation Of Aluminum Tri-hydroxidementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigating Aluminum Tri-Hydroxide Production from Sodium Aluminate Solutions in the Pedersen Process

et al. 2022

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“…Jiang et al and Xiaobin et al found that sodium hydroxide promotes the growth of gibbsite and trihydrate aluminum hydroxide crystals. Marinos et al , discovered that high concentrations of sodium carbonate are conducive to the formation of sodalite aluminum hydroxide, and temperatures above 65 °C favor the direct precipitation of sodalite aluminum hydroxide.…”

Section: Introductionmentioning

confidence: 99%

Study on Controlled Synthesis of Mesoporous Pseudoboehmite via Carbonation Reaction

Zhang,

Liu,

et al. 2024

Ind. Eng. Chem. Res.

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Pseudoboehmite is a precursor for mesoporous-activated alumina and is widely employed in catalysis and adsorption applications. The carbonation reaction is recognized as the most environmentally friendly and cost-effective production method. However, its susceptibility to impurity formation poses challenges in practical applications. The control of the reaction end point pH is crucial for ensuring purity. Currently, there is a lack of research on the influence of sodium aluminate solution concentration and composition ratio (α k ) on the reaction end point pH and its impact on the crystallization mechanism. This research extensively explored the effects of the sodium aluminate solution concentration and α k on the carbonation process. Analysis of crystalline phases under different conditions emphasized the critical influence of concentration and α k on the critical end point pH of pseudoboehmite synthesis and its impact on the crystallization mechanism. The results revealed significant effects of the concentration and α k on the pH change during the carbonation reaction. Increasing concentration raised both the maximum and minimum end point pH values, while elevated α k had the opposite effect. Increasing α k and concentration led to a narrowing of the pH range at the end point of the carbonation reaction for preparing pseudoboehmite. The study revealed that pseudoboehmite and Bayerite crystals were generated from two different sodium aluminate decomposition pathways, which challenges the conventional understanding of the crystalline growth mechanism of aluminum hydroxide. Reducing the pH value of the reaction end point accelerated the nucleation of pseudoboehmite and inhibition of Bayerite. Ultimately, successfully synthesizing mesoporous pseudoboehmite and activated alumina, with a pore volume of 0.44 cm 3 /L, surface area of 242.76 m 2 /g, and average pore diameter of 7.3 nm, this study not only supported precise reaction control and enhanced production efficiency but also offered insights for eco-friendly utilization of CO 2 , thus contributing to a more sustainable and environmentally friendly production process.

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“…Further details on the process can be found in the available bibliographic sources [5][6][7]. Significant research has been conducted recently in the framework of the EnsureAl EU project for modernizing the Pedersen process [8][9][10][11][12][13][14][15]. As an example in our earlier work, the partial replacement of coke with charcoal was studied and it was found to ease the smelting process [16].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Calcium Aluminate Slags and Pig Irons Produced from the Smelting-Reduction of Diasporic Bauxite

2021

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This work evaluates the characteristics of calcium aluminate slag and pig iron samples obtained from the smelting of calcined and reduced diasporic bauxite ore. The study is conducted in the Pedersen process framework, which is a method to produce alumina from low-grade resources. Parameters such as the effect of crucible type, lime addition, and atmospheric conditions are studied considering the characteristics of the product pig irons and calcium aluminate slags for further uses. The behavior of the bauxite and distribution of the species between slag and metal was assessed based on the applied analytical techniques and thermodynamic calculations. Iron was reduced and separated from the slags in the presence of carbon (graphite crucible) for both the reduced and calcined bauxite. Si and Ti were mainly concentrated in the slags. Iron was separated from the slag in the absence of carbon (alumina crucible) for the H2-reduced bauxite. The results show that slags with increased lime additions are composed mainly of 5CaO.Al2O3 and CaO.Al2O3, that are considered highly leachable compounds. An optimum CaO/Al2O3 mass ratio of 1.12 was suggested. The presence of O2 and/or OH- in the furnace atmosphere will result in the formation of 12CaO.7Al2O3.

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Parameters Affecting the Precipitation of Al Phases from Aluminate Solutions of the Pedersen Process: The Effect of Carbonate Content

Cited by 5 publications

References 17 publications

Investigating Aluminum Tri-Hydroxide Production from Sodium Aluminate Solutions in the Pedersen Process

Investigating Aluminum Tri-Hydroxide Production from Sodium Aluminate Solutions in the Pedersen Process

Study on Controlled Synthesis of Mesoporous Pseudoboehmite via Carbonation Reaction

Evaluation of Calcium Aluminate Slags and Pig Irons Produced from the Smelting-Reduction of Diasporic Bauxite

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