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The aluminium compounds in the bauxite may be present as gibbsite (Al(OH) 3), böhmite (γ-AlO(OH)) or diaspore (α-AlO(OH)); the different forms of the aluminium component and the impurities dictate the extraction conditions. Aluminium oxides and hydroxides are amphoteric, meaning that they are both acidic and basic. The solubility of Al(III ...
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.
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 social and environmental impacts of bauxite extraction are well documented. 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]
The production of aluminium starts with the extraction of bauxite rock from the ground. The bauxite is processed and transformed using the Bayer process into alumina , which is then processed using the Hall–Héroult process , resulting in the final aluminium.
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.
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]
The aluminium hydroxide is calcined to produce alumina. The process was used in France at Salindres until 1923 and in Germany and Great Britain until the outbreak of the Second World War. [5] While it has largely been replaced by the Bayer process, an updated version is still in use for processing high-silica bauxite. [6]: 90, 92–93