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Mineral Deposits
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Typical granites contain about 8 wt% aluminum. Chemical weathering, such as described above, can increase the aluminum concentration to between 25 and 30 wt%—a concentration factor of three to four. Thus, a warm climate and lots of water can transform normal granite into a reddish aluminum-rich soil, like the soil shown in Figure 13.13. This aluminum-rich soil is called laterite. Laterites commonly lithify partly, or completely, to become a rock, and some geologists use the term laterite as both a soil name and a rock name. Lateritic rocks that are particularly enriched in aluminum, like the deposit shown in Figure 13.13, are called bauxite. Thus, laterites and bauxites are the residue left behind after chemical weathering of granite. And, in bauxite, the aluminum that was originally in orthoclase and albite is in aluminum hydroxide minerals, including primarily boehmite, diaspore, and gibbsite.
Gender in the Mining Industry
Published in Karlheinz Spitz, John Trudinger, Mining and the Environment, 2019
Although it was not discovered until the 18th century, aluminium is the third most abundant element in the Earth’s crust. It is light weight but strong and ductile, with a low melting point and silver-white colour. It is highly reactive but difficult to extract from most of the minerals in which it occurs. Virtually all aluminium is extracted from bauxite, a lateritic ore containing gibbsite-a hydrated aluminium oxide. The process involves digestion in caustic soda followed by calcination to produce alumina; subsequently aluminium is obtained from the alumina by electrolytic reduction. Accordingly, production of aluminium is highly energy intensive. Aluminium is used in a variety of light weight alloys, particularly in transportation where light weight equates with reduced energy consumption, thus offsetting the energy used in its extraction. Aluminium compounds are widely used in water treatment, paper manufacture, in medicine and as refractory materials.
Matrices
Published in Marios Soutsos, Peter Domone, Construction Materials, 2017
Matrices for construction frp tend to be drawn from the thermosetting family of composites, with polyesters, vinylesters and epoxies being most popular, depending on the manufacturing method to be used. In terms of preparing these matrices for use in composites in the construction industry, the need to reduce specific costs (compared to the relatively high-margin, low-volume industries in which composites are traditionally used) leads to the extensive use of fillers. The need to provide fire resistance means that additives such as aluminium hydroxide (ATH, gibbsite) are also common. The long-term nature of construction applications means that proper curing to promote maximal cross-linking within the polymer (and thus weathering resistance) is essential (Halliwell, 2000). In particular, the correct mix ratio between the resin and the curing agent must be used to prevent unreacted remnants of either from remaining in the matrix (Holloway, 2010).
The relation between particle size and transformation temperature of gibbsite to αLPHA-alumina
Published in Mineral Processing and Extractive Metallurgy, 2022
Mohsen Nasiri Ahmadabadi, Ali Nemati, Kaveh Arzani, Saeid Baghshahi
Gibbsite, Al(OH)3, a common polymorph of aluminium trihydroxide, is produced commercially from bauxite by the Bayer process and is used as a precursor for the manufacture of α-alumina powder (Cardarelli 2008; Lee et al. 1996). The gibbsite precipitated in the Bayer process from seeded sodium aluminate solutions often occurs as agglomerates of tabular and hexagonal shaped crystals (Lee et al. 1996). The Bayer process conditions (crystallization temperature, type of alkali ions in the caustic aluminate solution, supersaturation, seed mass, stirring rate, etc) affect the size and the morphology of gibbsite particles (Seyssiecq et al. 1998). The crystal structure of gibbsite is based on double layers of a hexagonal close-packed array of hydroxyl ions in which Al3+ ions occupy two-thirds of the octahedral interstices. The double layers of hydroxyl groups are stacked in an AB-BA- sequence (Alex et al. 2014). Before the gibbsite transforms to α-Al2O3 phase, several transition aluminas may form, depending on atmosphere, temperature, heating rate, particle size of the gibbsite, etc. It is accepted that, in the presence of air, fine-grained gibbsite transforms successively to χ-, κ- and then α-Al2O3, whereas coarse-grained gibbsite, especially in the presence of water vapour, transforms to γ-,δ-, θ- and then α-Al2O3 (Figure 1) (Favaro et al. 2010; Zsolt et al. 2013; Rivas Mercury et al. 2020; Malki et al. 2014).
Synthesis and structural characterization of alumina nanoparticles
Published in Phase Transitions, 2020
Puneet Kaur, Atul Khanna, Nirmal Kaur, Priyanka Nayar, Banghao Chen
Petlinger et al. reported the structural description of these alumina phases [14]. Al(OH)3, commonly known as gibbsite, consists of layers of AlO6 octahedra that share one edge along the plane whereby each oxygen atom is bonded to a hydrogen atom. Bohemite or aluminum oxy-hydroxide (AlOOH) contains oxygen and aluminum ions in a double layer of octahedra with hydrogen atoms located in a zig-zag fashion [14]. The structure of γ-alumina is generally described as having defective cubic spinel-like structure, whose oxygen lattice is built by cubic closed packing of oxygen layers with vacancies existing on cationic sites with AlO6 and AlO4 structural units (denoted as Al[6] and Al[4] respectively) [16, 17]. θ-alumina consists of equally distributed aluminum ions at the octahedral and tetrahedral sites i.e. Al[4] =Al[6] = 50% [14, 18]. α-alumina (corundum) contains only Al[6], and can be described as having hexagonal close packing of spheres in which aluminum ions occupy two-thirds of octahedral interstitial sites [10, 17]. Further, the different alumina phases have different applications based on their physical properties. Ultrafine particle size, large surface area and high porosity of γ-alumina serves applications as catalysts, adsorbents, coatings, soft abrasives, catalysts in industrial activities like petroleum refining, alcohol dehydration, oxidation of CO into CO2 and reduction of automotive pollutants such as NOx [9, 12, 19]. Corundum is a widely used ceramic due to its high resistance to electricity, temperature and corrosion [14].
Gibbsite as low-temperature hydrothermal overprint on lateritised Cenozoic sediments, Quadrilátero Ferrífero of Minas Gerais, Brazil
Published in Applied Earth Science, 2020
Alexandre Raphael Cabral, Matheus Luís de Sales Oliveira, Thaís Keuffer Mendonça
A challenge for exploration geologists working on lateritic areas is to distinguish low-temperature hydrothermal minerals from those formed in deeply weathered profiles. This is because weathering-derived minerals can also form under low-temperature hydrothermal conditions. Gibbsite, monoclinic Al(OH)3, is common in lateritic soils and bauxite as a weathering product of aluminosilicate minerals, but it is also found as a low-temperature hydrothermal mineral filling veins and cavities in igneous rocks (Deer et al. 1992), and in carbonate rocks (Hewett et al. 1968; Segev 1984). It seems that no gibbsite of hydrothermal origin has ever been reported from lateritised sediments.