Bauxite production in Indonesia was 1.4 million tons compared with 4,72,000 tons in 2015, 2.56 million tons in 2014, and 57 million tons in 2013, as mines that supplied two alumina refineries ramped up production. A ban on exporting bauxite and other unprocessed mineral ores took effect on January 12, 2014. The export ban was part of …
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Different ways for alkaline recovery of aluminum from bauxite residue are considered from the literature and examined in experiments. The advantages and disadvantages of a high-temperature digestion via Bayer process and soda-lime sintering process are elaborated and compared. As a hybrid process, bauxite residue undergoes …
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bauxite processing . Flow Measurement of Sodium Hydroxide Solution in Bauxite Processing. After crushing and milling, the bauxite ore is heated in a pressure vessel along with a sodium hydroxide solution (NaOH) at a temperature of 150 to 200 °C to extract the aluminium as a sodium aluminate solution. احصل على السعر
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The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated. The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the …
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Associated with any bauxite source is some component of water, whose quantity depends on climate and geography, or the bauxite beneficiation processes. The …
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The Bayer process is the main method of alumina production worldwide. The use of low-quality bauxites for alumina production results in the formation of a significant amount of technogenic waste—bauxite residue (BR). The Bayer reductive method is one possible way to eliminate BR stockpiling, but it requires high-pressure leaching at …
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Bauxite is a sedimentary rock mineral that is the primary source of aluminum. It is formed through the weathering of aluminum-rich rocks in tropical and subtropical regions. The name bauxite is derived from the French village of Les Baux, where it was first discovered in 1821 by geologist Pierre Berthier. Bauxite is typically found in layers …
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A solution of hot concentrated sodium hydroxide (NaOH, i.e. caustic soda) liquor, taken from the recycled caustic liquor circuit, is added to the bauxite during grinding to …
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Bauxite residue neutralisation is intended to reduce the environmental impact of this highly alkaline material. Also, it can potentially reduce the need for on-going management of disposal impoundments post-closure, as well as open opportunities for re-use of the residue material. ... (NaOH), sodium carbonate (Na 2 CO 3) and sodium …
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Bauxite is not a mineral but a rock with minerals in it. It is a clay-like substance which is pinkish, whitish or reddish in color depending on the amount and type of impurities. It is soft and, when struck with a hammer, does not produce a metallic sound. Its specific gravity is generally around 2.6 and it has a Mohs hardness of 1 to 3.
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A new process of Al2O3 production from low-grade diasporic bauxite based on the reactive silica dissolution and stabilization in concentrated NaOH-NaAl(OH)4 solutions is proposed and proved feasible. NaOH and Al2O3 concentrations and leaching temperature were found to be the main factors affecting the leaching process of reactive silica. The …
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Bauxite is the most widely distributed ore used for alumina production. It is named after the small town in southern France called Les Baux, where it was first mined. Bauxite is typically a mixture of hydroxides of aluminium with iron oxides, silica and aluminosilicates. It results from the weathering, over geological time, of the parent rock ...
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The equilibrium solution pH and composition (24 h after bauxite addition) are reported in Table 12.4.India bauxite had a significantly higher equilibrium pH (pH 8.1 ± 0.1), compared to Guinea, Ghana, and USA bauxites (pH 6.6 ± 0.1, 6.5 ± 0.1, and 6.2 ± 0.4 respectively), which coincided with substantially higher concentrations of Ca and …
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Bauxite residue is a kind of strong alkaline waste produced in the production of alumina. Its long-term storage poses a potential threat to the environment. ... In the step I, 87.8 % aluminum oxide was extracted at 200 °C and 0.8 MPa for 3.5 h, NaOH concentration of 45 % with liquid-to-solid ratio of 0.9, 25 % CaO addition (relative to the ...
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Thus we obtain the product of the actual Bayer process: the aluminium oxide trihydrate Al 2 O 3 – H 2 O, or aluminium hydroxide Al (OH) 3 – both terms and both formulae are chemically correct. In analogy to the use in practice, we will use both terms. Aluminium hydroxide contains from 60% to 65% aluminium oxide, a small proportion of …
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WEBThe process he invented involved the pressure leaching of bauxite with NaOH solution to obtain sodium aluminate from which aluminum hydroxide was …
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In the Bayer process, bauxite ore is heated in a pressure vessel along with a sodium hydroxide solution (caustic soda) at a temperature of 150 to 200 °C. At these temperatures, the aluminium is dissolved as sodium aluminate (primarily [Al(OH)4]−) in an extraction process.
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Alumina is produced from bauxite, which contains a mixture of various oxides, such as aluminum (Al), iron (Fe), silicon (Si), and titanium (Ti). Bauxite can also be considered a source of several other valuable metals, such as scandium (Sc), vanadium (V), and gallium (Ga). The composition and mineralogy of alumina determine their …
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This is achieved by adding blended and ground bauxite, for consistent infeed, to a pressure vessel at 145–265°C, c.3.5 MPa, with sodium hydroxide (NaOH), conditions are chosen dependent on the aluminium compounds present [38, 39].
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Experimental Method. In this study, the recovery of precious metals from bauxite ore was examined by a two-stage leaching process. The stages of this process were Stage I: Removing iron to a large extent and revealing the solubility conditions of titanium by treating the bauxite ore with oxalic acid, Stage II: Determining the recovery …
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Abstract. Bauxite is processed in alumina refineries by the Bayer process in which Al-containing minerals are dissolved in hot NaOH. The insoluble solids (bauxite processing residue mud and sand) are washed, sometimes partially neutralized (using CO 2 or seawater treatment), and deposited in impoundments surrounding the refinery using …
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Compared with 650 and 700 °C, the pre-desilication results of low-grade bauxite after thermal activation at 600 °C had a significant improvement. Only after 30 min of leaching, the ratio of alumina to silica of low-grade bauxite can be increased from 2.39 to 6.78. This study may have a certain significance for selecting a suitable thermal ...
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In the Bayer process, bauxite is leached with a hot solution of sodium hydroxide (NaOH) at temperature of 150–240°C and at 1–6 atm pressure [ 7 ]. The …
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on dissolution kinetics of gibbsitic bauxite under atmospheric pressure in NaOH solution [J]. Journal of Central South Journal of Central South University, 2017, 24(3): 489 − 495.
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When this "bauxite" is treated with NaOH solution, the following reversible reaction takes place . ... The'flash' tank (Fig. 4.26) is a pressure vessel designed to allow depressurization of the incoming slurry from a pressure normally corresponding to its vapour pressure, to a lower pressure. In this depressurization process, steam is ...
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Bauxite and solid residue after NaOH leaching were characterized using XRD, SEM-EDS, and Möss spectroscopy methods. ... The high-pressure reactors were hermetically sealed steel vessels placed in an air thermostat with mixing through the head.
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Modeling the compensation effect for different bauxite types leaching in NaOH solution. December 2010. Chemical Engineering Communications 197 (12):1485-1499. DOI: …
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Bauxite is reacted with a conc. solution of NaOH under pressure for 2 hrs as a first step in obtaining Al 2 O 3. The impurities present in bauxite mainly Fe 2 O 3 and SiO 2 remain unaffected with conc. NaOH as impurities are not amphoteric. Bauxite, being amphoteric reacts with the base forming sodium salt [sodium aluminate] and water.
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The raw material used for alumina preparation is bauxite. This impure mineral is treated in the so-called Bayer Process in which the aluminum is dissolved in NaOH and separated from the impurities present in the original ore. The resultant sodium aluminate solution is then treated to precipitate aluminum hydroxide (bayerite) from which alumina ...
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Bauxite ore is a mixture of hydrated aluminium oxides and compounds of other elements such as iron. In the Bayer process, bauxite ore is heated in a pressure vessel along with a sodium hydroxide solution (caustic soda) at a temperature of 150 to 200 °C.
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Bauxite is a mixture of minerals which contain, as well as impurities, different concentrations of hydrated aluminium oxides. Gibbsite (alumina trihydrate), boehmite, and diaspore (alumina monohydrates) are the main ore minerals. Bauxite is a high-aluminium-content rock. That is the main ore that aluminium is mined from.
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Practically most of alumina produced commercially by bauxite is obtained via a process patented by Karl Josef Bayer in 1888. In the Bayer process, the aluminium-bearing minerals in bauxite – gibbsite, boehmite and diaspore – are selectively extracted from the insoluble components (mostly oxides) by dissolving them in a solution of sodium …
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Bauxite is the ideal raw material for the manufacturing of alumina. Aside from the primary constituents of aluminum and silicon, bauxite is frequently coupled with many valuable elements such as gallium (Ga), titanium (Ti), scandium (Sc), and lithium (Li). The bauxite residue and circulating spent liquor in alumina production typically include …
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ii. Crushed bauxite is leached with hot sodium hydroxide solution. iii. Impurities are removed from the sodium aluminate solution for filtration. iv. Solution is diluted after adding a little aluminium hydroxide, to precipitate aluminium hydroxide.
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1. Introduction. Microwave-assisted sample digestion is an important routine technique for the effective and safe dissolution of solid samples and subsequent elemental composition or isotope ratio analyses of a wide variety of matrices such as soils [1,2,3], sediments [4,5], minerals [1,6,7] and biota [8,9,10].Generally, the solid samples are …
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Wet grinding of the bauxite ore in rod mills, ball mills, or semiautogenous grinding mills to produce fine slurry. Digestion of the slurry by caustic soda (NaOH) at strengths exceeding 170 g/L in vessels under pressure at temperatures ranging from 145 to 265°C depending on the type of bauxite being processed.
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The Bayer Process was patented in 1888 in Germany by the Austrian chemist, Karl Joseph Bayer [].The simple chemistry of the process is that the hydrated forms of aluminum in bauxite, readily dissolve in heated caustic (NaOH) solutions (the DIGESTION step, see Chap. 4).The advantage is that nearly all of the minerals in …
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