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Bauxite is the main source of the rare metal gallium. [17] During the processing of bauxite to alumina in the Bayer process, gallium accumulates in the sodium hydroxide liquor. From this it can be extracted by a variety of methods. The most recent is the use of ion-exchange resin. [18]
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]
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 ...
In the 1970s, the increased demand for aluminium made it an exchange commodity; it entered the London Metal Exchange, the oldest industrial metal exchange in the world, in 1978. [95] The output continued to grow: the annual production of aluminium exceeded 50,000,000 metric tons in 2013. [102]
In the 1970s, the increased demand for aluminium made it an exchange commodity; it entered the London Metal Exchange, the world's oldest industrial metal exchange, in 1978. [98] Since then, aluminium has been traded for United States dollars and its price fluctuated along with the currency's exchange rate. [134]
The liquid aluminium is removed from the cell via a siphon every 1 to 3 days in order to avoid having to use extremely high temperature valves and pumps. Alumina is added to the cells as the aluminum is removed. Collected aluminium from different cells in a factory is finally melted together to ensure uniform product and made into metal sheets.
Mining for aluminum and the subsequent industrial usage disrupts the natural burial processes of the aluminum cycle. By the year 2050 the need for aluminum is expected to increase by 200-300%. [7] Aluminum is mined in the form of bauxite ore. Bauxite is only 40-60% aluminum oxide. [8] The elements that make up the rest of bauxite are also very ...
The first stage is the calcination of the bauxite at 1200 °C with sodium carbonate and coke. The alumina is converted in sodium aluminate. Iron oxide remains unchanged and silica forms a polysilicate. In the second stage sodium hydroxide solution is added, which dissolves the sodium aluminate, leaving the impurities as a solid residue. The ...