- 27 July 2024
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Aluminum is one of the most abundant elements in the Earth's crust. It is obtained from bauxite, i.e. sedimentary rock, in which it mainly occurs in the form of oxide.
Aluminum has been known for more than 2,000 years and has a wide range of technical applications. In industry, aluminum is mainly used in alloys with other elements, which improves its functional properties. It is a versatile structural material with very versatile applications. Among aluminum alloys, we can distinguish in particular casting alloys and alloys used for plastic processing. In addition to aluminum, they contain elements such as copper, magnesium, silicon and manganese. Aluminum alloys are used especially in aviation, chemical, automotive and even shipbuilding industries.
Aluminum in its pure form is widely used in industry for the production of household items, such as mirrors, beverage and food cans, kitchen utensils and aluminum foil. It is also used in the manufacture of chemical equipment, electrical wiring and even explosives. In order to isolate this element from aluminum ore, the Bayer process, which produces aluminum oxide from aluminum ore, must be carried out. This compound is then subjected to electrolysis, resulting in pure aluminum.
Pure aluminum does not occur because of its ability to passivate. This phenomenon involves oxidation of the metal in the presence of air, resulting in the formation of a passive protective layer on its surface. The aluminum is coated with a layer of aluminum oxide (Al 2 O 3 ) up to a few nm thick. Then, under the influence of moisture, the outer layer is partially hydrolyzed, resulting in the formation of a hydroxide, i.e. Al(OH). As a result, aluminum deposits are various mineral rocks. For the production of pure aluminum, mainly clay bauxite ore is used. It is mainly formed in places where aluminosilicate rocks are weathered and also contains iron compounds. It is a rock with a characteristic red or brown color, which comes in two types: silicate and carbonate.
Certain climatic conditions, namely high temperature and water, are necessary for aluminum deposits to form. Based on their origin, they are divided into lateritic and redeposited (sedimentary). And if these two processes overlap, mixed-type bauxites are obtained. Aluminum ore is mainly formed in tropical climates. That's why aluminum deposits in Poland are so rare.
Leterite bauxites are formed by deep weathering of rocks, for example, basalts, syenites, shales and feldspars. Under the influence of the hot sun and warm tropical rains, these rocks have lost calcium, magnesium and silicon. What remained was aluminum oxide along with aqueous iron oxides. This results in the formation of residual (lateritic) bauxites.
Initially, bauxite was formed only in the equatorial zone of the planet, but then with the movement of the continents it moved north and south of the equator. Today, bauxite deposits are known, including in Europe, the Urals and North America. The five largest countries in terms of bauxite resources are Guinea, Australia, Vietnam, Brazil and Jamaica. The largest bauxite deposits are located in Guinea. According to various sources, between 26 and 29% of the planet's total proven bauxite reserves lie within the territory of this African country. Guinean bauxite is of high quality, contains minimal impurities and occurs close to the surface. The average alumina content of the ore ranges from 52 to 65%. The situation is somewhat different in bauxite mining than in deposits. The lead in production is held by Asian countries (India and China), followed by Australia, then Latin American countries and only after that by countries of the African continent. Aluminum deposits in Poland are found, among others, near Nowa Ruda in Lower Silesia. At the same time, there have been no aluminum smelters in Poland for several years. The last one in Konin was closed for economic reasons.
