Metals are found as ores buried in the Earth's crust. So how do we get to the final metal? There are three main stages.
mining
extraction
purification.
Let's look at each of these in more detail.
Picture 4. A copper mine. The size of the trucks in the picture give an idea of the scale.
Mining
The copper ore has to be dug from the ground. The ore contains some copper mineral and lot of waste rock. The copper mine in picture 4 produces 6 tonnes of copper from every 1000 tonnes of ore.
Extraction
An ore has to be changed chemically into the metal. This process is called reduction. How this is done, and how much it costs, depends upon the metal's reactivity (see reactivity properties). In general, the more reactive the metal, the harder it is to extract it from its ore.
Metal
ore
Reactivity
Primary process
aluminium
found mainly as the ore bauxite
high
electrolysis
iron
extracted from the ore
medium
blast furnace
copper
various ores
low
roasting in air
5. Laboratory apparatus for electrolysis.
Purification
Many metals are impure when they are extracted from their ores. Impurities have to be removed. Copper is purified by electrolysis. In this process copper is transferred from an impure anode to the cathode of an electrolytic cell. The insoluble impurities fall to the bottom. The copper produced by this process is 99.99% pure copper.
This is similar to the electrolysis that is done in a school lab.
