The Bayer process is the principal industrial means of producing alumina, itself important in the Hall-Héroult process for producing aluminum. Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... The Hall-Héroult process is the major industrial process for the production of aluminum. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ...

Bauxite, the most important ore of aluminum, contains only 40-60% alumina, Al₂O₃, the rest being a mixture of silica, various iron oxides, and titanium dioxide. The alumina must be purifed before it can be refined to aluminum metal. In the Bayer process, bauxite is washed with a hot solution of sodium hydroxide, NaOH, at 250°C. This converts the alumina to aluminium hydroxide, Al(OH)₃, which dissolves in the hydroxide solution according to the chemical equation Jump to: navigation, search Bauxite Bauxite is a naturally occurring, heterogeneous material composed primarily of one or more aluminium hydroxide minerals, plus various mixtures of silica, iron oxide, titania, aluminium silicates, and other impurities in minor or trace amounts. ... Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Iron oxide pigment There are a number of iron oxides: Iron oxides Iron(II) oxide or ferrous oxide (FeO) The black-coloured powder in particular can cause explosions as it readily ignites. ... Jump to: navigation, search Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2. ... Jump to: navigation, search Flash point non flammable Supplementary data page Structure and properties n, εr, etc. ... Aluminium hydroxide, Al(OH)3, is the most stable form of aluminium in normal conditions. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

Al₂O₃ + 2 OH^- + 3 H₂O → 2 [Al(OH)₄]^-

The other components of bauxite do not dissolve and can be filtered out as solid impurities. Next, the hydroxide solution is cooled, and the aluminium hydroxide dissolved in it precipitates out as a white, fluffy solid. When then heated to 1050°C, the aluminium hydroxide decomposes to alumina, giving off water vapor in the process: Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... Jump to: navigation, search Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: −O−H It has a charge of −1. ... Jump to: navigation, search Water (from the Old English word wæter; c. ...

2 Al(OH)₃ → Al₂O₃ + 3 H₂O

Aluminium hydroxide, Al(OH)3, is the most stable form of aluminium in normal conditions. ... Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... Jump to: navigation, search Water (from the Old English word wæter; c. ...

History

The Bayer process was invented in 1888 by the Austrian chemist Karl Bayer. Working in Saint Petersburg, Russia to develop a method for supplying alumina to the textile industry (it was used as a mordant in dyeing cotton), Bayer discovered in 1887 that the aluminium hydroxide that precipitated from alkaline solution was crystalline and could be easily filtered and washed, while that precipitated from acid medium by neutralization was gelatinous and difficult to wash. Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... Aluminium hydroxide, Al(OH)3, is the most stable form of aluminium in normal conditions. ...

A few years earlier, Louis Le Chatelier in France develpoed a method for making alumina by heating bauxite in sodium carbonate, Na₂CO₃, at 1200°C, leaching the sodium aluminate formed with water, then precipitating aluminium hydroxide by carbon dioxide, CO₂, which was then filtered and dried. This process was abandoned in favor of the Bayer process. Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ... Aluminium hydroxide, Al(OH)3, is the most stable form of aluminium in normal conditions. ... Jump to: navigation, search Carbon dioxide is an atmospheric gas composed of one carbon and two oxygen atoms. ...

The process began to gain importance in metallurgy together with the invention of the electrolytic aluminum process invented in 1886. Together with the cyanidation process invented in 1887, the Bayer process marks the birth of the modern field of hydrometallurgy Hydrometallurgy involves the use of aqueous chemistry to purify metals or mineral concentrates. ...

Today, the process is virtually unchanged and it produces nearly all the world's alumina supply as an intermediate in aluminum production.

After Habashi, F. "A short history of hydrometallurgy", Hydrometallurgy 79, pp. 15-22, 2005.