What is aluminium?
Aluminium is a silvery-white metal, the 13 element in the periodic table. One surprising fact about aluminium is that it's the most widespread metal on Earth, making up more than 8% of the Earth's core mass. It's also the third most common chemical element on our planet after oxygen and silicon.
At the same time, because it easily binds with other elements, pure aluminium does not occur in nature. This is the reason that people learned about it relatively recently. Formally aluminium was produced for the first time in 1824 and it took people another fifty years to learn to produce it on an industrial scale.
The most common form of aluminium found in nature is aluminium sulphates. These are minerals that combine two sulphuric acids: one based on an alkaline metal (lithium, sodium, potassium rubidium or caesium) and one based on a metal from the third group of the periodic table, primarily aluminium.
Aluminium sulphates are used to this day to clean water, for cooking, in medicine, in cosmetology, in the chemical industry and in other sectors. By the way, aluminium got its name from aluminium sulphates which in Latin were called alumen.
Today we know about almost 300 various aluminium compounds and minerals containing aluminium, from feldspar, a key source mineral on Earth, to ruby, sapphire and emerald, which are far less common.
But regardless of how common aluminium may be, it may have remained hidden forever if it hadn't been for electricity. The discovery of aluminium was made possible when scientists were able to use electricity to break down chemical compounds into their elements. In the 19 century the Danish physicist Christian Oersted used electrolysis to obtain aluminium. Electrolysis or electrolytic reduction is the process that is used to produce aluminium today as well.
Another rather common mineral, bauxite, is used today as the primary raw material in aluminium production. Bauxite is a clay mineral comprising various modifications of aluminium hydroxide mixed with iron, silicon, titanium, sulphur, gallium, chromium, vanadium oxides, as well as sulphuric calcium, iron and magnesium carbonates. In other words, your typical bauxite contains almost half the periodic table. By the way, because of the texture of bauxite about a hundred years ago aluminium was often referred to rather poetically as silver obtained from clay. On the average 4-5 tonnes of bauxite are needed to produce 1 tonne of aluminium.
In the first stage of aluminium production bauxite is processed into alumina, or aluminium oxide Al2O3. Alumina looks like white powder and it is then processed into aluminium at aluminium smelters using electrolytic reduction.
Aluminium production requires huge amounts of electricity, about 15 MWH per tonne of output. That's approximately as much as a 100-apartment block consumes in a month. So the best site for an aluminium smelter is next to a powerful, preferably renewable, energy source. Hydroelectric power plants are the best option as they are the most powerful 'green' energy sources available today.
Aluminium offers a rare combination of valuable properties. It is one of the lightest metals in the world: it's almost three times lighter than iron but it's also very strong, extremely flexible and corrosion resistant because its surface is always covered in an extremely thin and yet very strong layer of oxide film. It doesn't magnetise, it's a great electricity conductor and forms alloys with practically all other metals.
Since aluminium easily forms compounds with other chemical elements, a huge variety of aluminium alloys have been developed. Even a very small amount of admixtures can drastically change the properties of the metal, making it possible to use it in new areas. For example, in ordinary life you can find aluminium mixed with silicon and magnesium literally on the road, i.e. in the aluminium alloy wheels, in the engines, chassis and other parts of modern automobiles. As for aluminium zinc alloy, chances are you might be holding it in your hands right now as it's this alloy that's widely used in the production of mobile phones and tablet PCs. In the meantime, scientists keep developing new aluminium alloys.
The modern construction, automotive, aviation, energy, food and other industries would be impossible without aluminium. In addition, aluminium has become a symbol of progress: all cutting edge devices and vehicles are made from aluminium.
