One of the potential sources of rareearth elements (REE) is the industrial waste known as red mud (bauxite residue), in which the majority of REE from the initial bauxite are concentrated via the Bayer process. Therefore, the studies of the subject, both in Russia and outside, focus almost exclusively on red mud processing. This article looks into the possibility of REE concentration into red ...
Based on lime sintering method, a novel process of alumina production from lowgrade bauxite containing sulfur or fly ash is carried out in this paper. The phase of alumina transforms from 12CaO·7Al 2 O 3 (C 12 A 7) to 4CaO·3Al 2 O 3 ·SO 3 (C 4 A 3 S), whose alumina leaching property is better, through decreasing sinter temperature and time ...
Because the water leaching process does not consume additional reagents, it is economical. Still, this process is timeconsuming because longterm leaching and repeated dealkalization are necessary for the water leaching process. ... Red mud is a solid waste produced in the process of alumina prodn. from bauxite following the Bayer process ...
Iron and alumina can be separated from bauxite residue and calcite selfhardened reduced pellets through simultaneous magnetic separation and alkali leaching. Bauxite residue and calcite selfhardened pellets were reduced nonisothermally by hydrogen gas to obtain metallic iron. Thereafter, the fine grounded reduced pellet powder was leached with a simultaneous magnetic stirrer, while two ...
This method is based on the leaching of precrushed bauxite in alkaline solutions. After leaching, aluminum hydroxide separates from the aluminate solution and is then calcinated to produce alumina. Highquality bauxites with an Al 2 O 3 to SiO 2 mass ratio of more than 8 are required as a raw material for alumina production by the Bayer process .
The alumina extraction percent was determined at different leaching times (30180 min) and solid/liquid ratios ( g/ml). The purity of kaolin is about 95%.
This article looks into the possibility of REE concentration into red mud by leaching an intermediate product of the bauxite sintering process at Russian alumina refineries, namely electrostatic ...
The leaching process with dilute HNO 3 was performed at pilot scale and optimized for the extraction of scandium from bauxite residue ( OchsenkühnPetropoulou et al., 2002 ). Xue et al. (2010) found that at a reaction temperature of 90 °C and an L/S ratio of 3:1, over 80% of the scandium in bauxite residue could be leached by H 2 SO 4.
As a hybrid process, bauxite residue undergoes a reductive smelting process with lime addition in an electric arc furnace in order to generate aluminaenriched slag. This slag is subsequently treated with highpressure caustic leaching at moderated (200300 g/l) and high (572762 g/l) sodium hydroxide concentrations.
The doublecycle process is pressure leaching of hydrochloric acid—extraction and separation of leaching solution—direct pyrolysis of aluminum chloride solution for producing alumina. Firstly, highiron bauxite is used as raw material to extract aluminum and iron elements in it by hydrochloric acid leaching.
In the extraction of aluminium, the significance of leaching is to concentrate pure alumina (AL2O3) from bauxite ore. Bauxite usually contains silica, iron oxide, and titanium oxide as impurities. In the process of leaching, alumina is concentrated by digesting the powdered ore with a concentrated solution of NaOH at 473523K and 3536 bar.
However, high alumina in the bauxite residue increases the flux and acid consumption. Therefore, alumina needs to be removed by alkali roasting prior to smelting in order to decrease the flux and acid consumption. The alkali roastingsmeltingleaching process allows recovery of aluminum, iron, titanium, and REEs from bauxite residue.
The application of bauxite enrichment in the Bayer process before leaching for bauxites from Guinea and Sierra Leone is due to the loss of alumina or alkali in the red mud.
Hall's process for leaching of alumina from bauxite: (1) Bauxite ore and sodium carbonate are fused toghether to convert aluminium oxide into soluble sodium metaaluminate. The insoluble residue contains the impurities of silica and iron oxide. The fused mass is treated with water.
1. Introduction. Red mud (RM) is a waste generated during bauxite processing for alumina production. The most common method for bauxite processing is the Bayer process, where raw material is digested under high pressure by NaOH to obtain a pregnant sodium aluminate solution [].During highpressure leaching, nonsoluble elements such as iron, titanium, and refractory or precipitated during ...
More than 95% of the global alumina production (134 million tons) in 2021 was from bauxite processed through the Bayer process [ 2 ]. The global reserves of bauxite ore are estimated between 55 and 75 billion tons and are sufficient to meet the world demand well into the future [ 3 ].
Bayer process is a leaching process of bauxite. This process is use to produce high purity alumina (needed in subsequent electrolysis process) by leaching bauxite by NaOH. Leaching is done in autoclave at high presuure ( 2530 atm) and high temperature (220 o C), which produces a soluble aluminate (2NaAlO 2), and from which we precipitate out ...
The Bayer process is used worldwide for the alumina production. This process involves the alkaline leaching of bauxite to extract Al, followed by the precipitation of Al(OH) 3 to recycle the solution [1,2,3].The leaching process results in the formation of a solid residue, commonly referred to as a bauxite residue, which consists of iron minerals, hydrous aluminosilicates, which are formed ...
Aluminum dross samples were found to approximately contain 75wt% Al2O3 and 12wt% SiO2. An acid dissolution process was used to recover the alumina value from the dross. The effects of various parameters,, temperature, acid concentration, and leaching time, on the extraction of alumina were studied to optimize the dissolution process.
In the leaching of Alumina from bauxite, concentration of the ore is done by digesting the powdered ore with NaOH and then it is later reacted with CO2 gas. Consider the major impurities presents related to SiO2 is leached out along with Al2O3 as silicate and aluminate on reaction with Iron oxides and titanium oxide are insoluble in NaOH and are left behind as
A bauxite residue typically contains 1525% of alumina depending on the origin of its ore and process conditions. Along with alumina, it also contains iron, titanium and rare earth elements ...
In some cases, the impure ore is treated with a suitable reagent, such as an acid or a base. Because of that, the ore particles dissolve due to leaching, but the gangue impurities do not react. This process is a solidliquid extraction process, and the following example illustrates the procedure of this process: Leaching of alumina from bauxite:
AD contains a large amount of alumina, which is an important raw material for preparing alumina instead of bauxite. ... The apparent rate constant (k d) was found to be min −1 min −1 and the activation energy of aluminum in the leaching process was evaluated to be kJ/mol. The study of leaching kinetics can reveal ...
This study investigates applying the principles of the longdiscontinued Pedersen process as a possible route for producing metallurgical grade alumina from lowgrade 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 ...
© DZCrusher - كل الحقوق محفوظة
