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The Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and was developed by Carl Josef Bayer.Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al 2 O 3), the rest being a mixture of silica, various iron oxides, and titanium dioxide. [1]
Most of the world's bauxite deposits can be found within 1 to 20 metres (3 ft 3 in to 65 ft 7 in) of the earths surface. [21] [22] Strip mining is the most common technique used for extracting shallow bauxite. [22] This process involves removing the vegetation, top soil, and overburden to expose the bauxite ore. [22]
Bauxite forms by the weathering of aluminum-rich and silica-poor rocks in hot, humid, climates, at places with good drainage. Under the proper conditions, weathering disintegrates the aluminium silicate minerals, and dissolves and removes the silica, creating bauxite. The mined US bauxite deposits have all been in the southeastern United States.
A mixture of the minerals comprise bauxite ore, including gibbsite (Al(OH) 3), boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH)), along with impurities of iron oxides and hydroxides, quartz and clay minerals. [22] Bauxites are found in laterites. Bauxite is typically purified using the Bayer process: Al 2 O 3 + H 2 O + NaOH → NaAl(OH) 4
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite , aluminium 's chief ore, through the Bayer process ) in molten cryolite and electrolyzing the molten salt bath, typically in a purpose-built cell.
Bauxite was discovered in 1821 by Pierre Berthier who named it after a village named Les Beaux where he found it. [6] To obtain the alumina from the bauxite ore, a process was developed that used acid to dissolve aluminium but resulted in a product that contained large amounts of iron and titanium dissolved within which were difficult to remove. [6]
2023 bauxite production and reserves (thousands of tons) [1] Country Production Reserves World: 400,000: 30,000,000
The Deville–Pechiney process, also known as the Le Châtelier process, [1]: 15 [2]: 86 was the first industrial process used to produce alumina from bauxite. The Frenchman Henri Sainte-Claire Deville invented the process in 1859, in collaboration with Louis Le Châtelier .