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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.
The process produces a quantity of fluoride waste: perfluorocarbons and hydrogen fluoride as gases, and sodium and aluminium fluorides and unused cryolite as particulates. This can be as small as 0.5 kg per tonne of aluminium in the best plants in 2007, up to 4 kg per tonne of aluminium in older designs in 1974.
Aluminium recycling is the process in which secondary commercial aluminium is created from scrap or other forms of end-of-life or otherwise unusable aluminium. [1] It involves re-melting the metal, which is cheaper and more energy-efficient than the production of virgin aluminium by electrolysis of alumina (Al 2 O 3 ) refined from raw bauxite ...
The same year, in the United States, Charles Martin Hall (1863–1914) was discovering the same process. Because of this, the process was called the Hall–Heroult process . Héroult's second most important contribution is the first commercially successful electric arc furnace (EAF) for steel in 1900.
The Wöhler process was one of the first routes for producing aluminium metal. It involves the reduction of anhydrous aluminium chloride with potassium , produced powdered aluminium: [ 1 ] AlCl 3 + 3 K → Al + 3 KCl
Molten cryolite is used as a solvent for aluminium oxide (Al 2 O 3) in the Hall–Héroult process, used in the refining of aluminium. It decreases the melting point of aluminium oxide from 2000–2500 °C to 900–1000 °C, and increases its conductivity [ 18 ] thus making the extraction of aluminium more economical.
[h] Hall co-founded the Pittsburgh Reduction Company in 1888 and initiated production of aluminium. [88] Hall's patent was granted in 1889. [74] [i] In 1889, Hall's production began to use the principle of internal heating. [j] By September 1889, Hall's production grew to 385 pounds (175 kilograms) at a cost of $0.65 per pound. [91]
Julia Brainerd Hall (November 11, 1859 – September 4, 1926) [1] was the sister of American scientist Charles Martin Hall. She supported him in his discovery of the Hall process for extracting aluminium from its ore. [2] She was also a still-life painter who exhibited at the Edgar Adams Gallery in Cleveland. [3]