Environmental Engineering Reference
In-Depth Information
20
Erosion
The Perpetual Disruptive
Forces of Water and Wind
ALUMINIUM
Although it was not discovered until the 18th century, aluminium is the third most
abundant element in the Earth's crust. It is light weight but strong and ductile, with a low
melting point and silver-white colour. It is highly reactive but difficult to extract from most
of the minerals in which it occurs. Virtually all aluminium is extracted from bauxite, a
lateritic ore containing gibbsite-a hydrated aluminium oxide. The process involves digestion
in caustic soda followed by calcination to produce alumina; subsequently aluminium is
obtained from the alumina by electrolytic reduction. Accordingly, production of aluminium
is highly energy intensive. Aluminium is used in a variety of light weight alloys, particularly in
transportation where light weight equates with reduced energy consumption, thus
offsetting the energy used in its extraction. Aluminium compounds are widely used in water
treatment, paper manufacture, in medicine and as refractory materials.
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