Extracting metal using electrolysis
Metals can be extracted from their ore using electrolysis. Electrolysis is used to extract metals that are more reactive than carbon, such as aluminum. These more reactive metals can’t be extracted by heating them with carbon. Metals that are less reactive than carbon, such as iron, can be extracted by heating with carbon, or with electrolysis. They are usually extracted by heating with carbon because electrolysis uses more electricity, so is a more expensive process to use.
Aluminum is the most abundant metal on Earth, but it is most commonly found as its ore, aluminum oxide (Al2O3). We can extract aluminum from its ore, with the industrial set up of the electrolytic cell shown in Figure 1.
The electrolyte is molten aluminum oxide, and the electrodes are graphite. The aluminum (Al3+) cations are attracted to the cathode, where they are reduced to form molten aluminum. The reduction reaction is:
The aluminum is deposited on the bottom of the cell and drains away. The oxygen (O2-) anions are attracted to the anode, where they are oxidised to release oxygen gas. The oxidation reaction is:
Figure 1 - Electrolysis of aluminum oxide to extract aluminum.