High-Tech Metals Distribution in Bauxites: From the Ore Genesis to the Bayer Process Residue

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (31 May 2019) | Viewed by 17909

Special Issue Editor

Department of Sciences, University of Basilicata, Viale dell'Ateneo Lucano, 10 - 85100 Potenza, Italy
Interests: ore geochemistry; sedimentary geochemistry; environmental geochemistry; water-rock interaction; applied mineralogy

Special Issue Information

Dear Colleagues,

Bauxite is a residual rock, consisting mainly of a mixture of aluminum hydroxides, of which industrial significance is primarily due to its profitably exploitable alumina contents. In the last few decades, bauxite ores have also been considered as a possible resource for a great number of economically-interesting elements, including some High-Tech Metals (HTM) such as REEs+Y+Sc, V, Co, Ni, Ga, Ge, and In. HTM, which are generally “co-elements”, mainly recovered as byproducts of other metallic ores, are important in a wide range of modern technologies, and their availability is generally poor relative to the current demand. Assuring supplies of HTM, largely used in modern engineered materials but subject to supply risks or concerns about availability, is a compelling challenge. This Special Issue aims to publish papers dealing with HTM behavior in bauxites and in the residue of the Bayer process developed on bauxite ores (Red Muds). Papers providing the assessment of HTM content in bauxite ores and their residue and the evaluation of the structural bonding of HTM into the supergene ore minerals, in the perspective of the determination of the best treatment for making HTM amenable to low-cost recovery are also welcome.

Dr. Giovanni Mongelli
Guest Editor

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Keywords

  • Bauxite ores
  • Red muds
  • High tech metals distribution and recovery
  • Mineralogical control

Published Papers (4 papers)

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Research

18 pages, 11622 KiB  
Article
Rare Earth Elements (REE) in Al- and Fe-(Oxy)-Hydroxides in Bauxites of Provence and Languedoc (Southern France): Implications for the Potential Recovery of REEs as By-Products of Bauxite Mining
Minerals 2019, 9(9), 504; https://doi.org/10.3390/min9090504 - 22 Aug 2019
Cited by 21 | Viewed by 5052
Abstract
Bauxites in southern France (Provence and Languedoc) have been exploited since the beginning of the last century. Though most of the deposits are now subeconomic or mined-out, these bauxites represent model analogs for other economic bauxites of the world. These Cretaceous karst-type deposits [...] Read more.
Bauxites in southern France (Provence and Languedoc) have been exploited since the beginning of the last century. Though most of the deposits are now subeconomic or mined-out, these bauxites represent model analogs for other economic bauxites of the world. These Cretaceous karst-type deposits lie directly on Jurassic carbonates, and have been formed through a combination of different processes: in-situ alteration of siliciclastic sediments deposited on carbonate platforms, and reworking of early bauxites in the karst network. In this study, we present preliminary bulk rock geochemical and in-situ laser ablation (LA) -ICP-MS analyses on Al- and Fe-oxy-hydroxides of Provence (Les Baux-de-Provence) and Languedoc (Villeveyrac, Loupian) bauxites, with the aim of evaluating the concentrations of rare earth elements (REEs) and their deportment in these minerals. REEs have total average concentrations of 700 mg/kg in the analyzed samples, which are mostly composed of boehmite, γ-AlO(OH), and Fe-oxy-hydroxides (hematite and goethite). Maximum REEs concentrations are commonly associated with positive Ce anomalies in chondrite-normalized patterns. In contrast with other examples from the literature, it has been observed that high REE concentrations also occur in samples apparently devoid or poor of REE-minerals. In these samples, the total amount of REEs is positively correlated with that of Ga (commonly contained in boehmite). LA-ICP-MS trace element analyses on boehmite and Fe-oxy-hydroxides have shown that while the Al-hydroxide contains the suite of REEs, goethite and hematite are preferentially enriched only in Ce. Considering that Al-hydroxides are digested during the Bayer process, an interesting issue to develop in the future is whether (and how) REEs released during Al-hydroxide digestion could be recovered together with Al from the pregnant leach liquor, as routinely done for Ga. Full article
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13 pages, 924 KiB  
Article
Optimizing Conditions for Scandium Extraction from Bauxite Residue Using Taguchi Methodology
Minerals 2019, 9(4), 236; https://doi.org/10.3390/min9040236 - 17 Apr 2019
Cited by 20 | Viewed by 3963
Abstract
Bauxite residue is the voluminous by-product of alumina production after Bayer process. Its high alkalinity causes disposal problems and harmful environmental impacts. However, the residue contains significant amounts of valuable elements, such as rare earth elements, including scandium. Greek bauxite residue contains a [...] Read more.
Bauxite residue is the voluminous by-product of alumina production after Bayer process. Its high alkalinity causes disposal problems and harmful environmental impacts. However, the residue contains significant amounts of valuable elements, such as rare earth elements, including scandium. Greek bauxite residue contains a high amount of scandium close to its main resources. Taking into account scandium’s limited availability coupled with its high demand in modern technology, bauxite residue could be considered as a potential resource for scandium recovery. In this study, the optimization of scandium extraction from bauxite residue with sulfuric acid is investigated using Taguchi methodology. Based on previous studies, acid molarity, leaching time, solid/liquid ratio, and reaction temperature were selected as control parameters for the selective Sc recovery. Method optimization targeted the highest concentration of scandium combined with the lowest concentration of iron without taking into account application constraints. Maximization of scandium concentration can be achieved only by reduced selectivity. The predicted values resulted from the Taguchi methodology were affirmed by a confirmation experiment conducted at optimal conditions. Regression analysis provided the respective equations to be applied on several conditions, depending on different applications. Full article
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16 pages, 8152 KiB  
Article
Semi-Smelting Reduction and Magnetic Separation for the Recovery of Iron and Alumina Slag from Iron Rich Bauxite
Minerals 2019, 9(4), 223; https://doi.org/10.3390/min9040223 - 09 Apr 2019
Cited by 17 | Viewed by 3710
Abstract
This work presents a semi-smelting reduction and magnetic separation process for the recovery of iron and alumina slag from iron rich bauxite ore. The effect of the process parameters on the recovery rate of iron, maximum particle size of the iron nugget, and [...] Read more.
This work presents a semi-smelting reduction and magnetic separation process for the recovery of iron and alumina slag from iron rich bauxite ore. The effect of the process parameters on the recovery rate of iron, maximum particle size of the iron nugget, and the Al2O3 content of the alumina slag was investigated and optimized. The results show that the iron nuggets and alumina slag can be obtained in a short time through a semi-smelting reduction and magnetic separation process. The maximum particle size of iron nugget is about 15 mm, and the recovery rate of the iron and Al2O3 grade of the alumina slag are 96.84 wt % and 43.98 wt %, respectively. The alumina slag consisted mainly of alumina (α-Al2O3), calcium hexaluminate (CaAl12O19), gehlenite (Ca2Al2SiO7), and small amounts of hercynite (FeAl4O7), and metallic iron (M.Fe). Full article
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15 pages, 17257 KiB  
Article
Increased As Adsorption on Maghemite-Containing Red Mud Prepared by the Alkali Fusion-Leaching Method
Minerals 2019, 9(1), 60; https://doi.org/10.3390/min9010060 - 20 Jan 2019
Cited by 20 | Viewed by 4774
Abstract
This study investigates the use of red muds as adsorbents for As (V) removal. Red mud is a waste that contains a large amount of iron oxides and hydroxides, which are excellent adsorbents of arsenic, especially those possessing magnetic properties and a large [...] Read more.
This study investigates the use of red muds as adsorbents for As (V) removal. Red mud is a waste that contains a large amount of iron oxides and hydroxides, which are excellent adsorbents of arsenic, especially those possessing magnetic properties and a large specific surface area. The purpose of the experiments was to study the possibility of obtaining an effective adsorbent by the direct extraction of alumina from bauxite using the caustic alkali fusion method and to compare the arsenic removal effectiveness and other properties of these red muds with industrial samples. Red muds were described using methods such as X-ray diffraction spectrometry (XRD), X-ray fluorescence spectrometry (XRF), SEM, vibrating sample magnetometry (VSM), and the Brunauer–Emmett–Teller (BET) method. The main iron-containing phase of the red muds obtained by fusing bauxite with caustic alkali is maghemite, which has a large specific surface area. The specific surface area of the obtained samples varied in the range of 6.1–54.9 m2/g. Arsenic adsorption experiments were carried out using five different types of red muds: industrial Bayer, industrial sintering, and red mud obtained through bauxite alkali fusion at 300, 500, and 700 °C. The red muds obtained by fusing bauxite with caustic alkali at 300 and 500 °C had the highest effectiveness removing arsenic; their As(V) uptake capacity was over 30 mg/g. Full article
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