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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 is a raw material used primarily in the production of aluminium. The bauxite ore is refined into alumina before being smelted into aluminium. [3] Australia is known for its high-grade ore, especially in the Weipa and Gove deposits. [2] The quality of bauxite ore is determined by its available alumina (Al 2 O 3) content.
Alumina is extracted from the ore bauxite by means of the Bayer process at an alumina refinery. This is an electrolytic process, so an aluminium smelter uses huge amounts of electric power; smelters tend to be located close to large power stations, often hydro-electric ones, in order to hold down costs and reduce the overall carbon footprint ...
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.
Red mud near Stade Bauxite, an aluminium ore (Hérault department, France).The reddish colour is due to iron oxides that make up the main part of the red mud.. Red mud, now more frequently termed bauxite residue, is an industrial waste generated during the processing of bauxite into alumina using the Bayer process.
Gibbsite is an important ore of aluminium in that it is one of three main phases that make up the rock bauxite. Gibbsite has three named structural polymorphs or polytypes: bayerite (designated often as α-Al(OH) 3, [2]: 2 but sometimes as β-Al(OH) 3) [citation needed], doyleite, and nordstrandite.
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]