Waste materials such as polymers and metals are often disposed of in landfill sites. Waste polymers may be incinerated. However, these disposal methods waste valuable resources, including these raw materials:
Recycling involves collecting used items and producing new materials from them. The first steps usually needed are:
Recycling polymers also involves:
Recycling metals also involves:
The ingots can then be used to manufacture new metal items.
Describe a simple way to separate aluminium from iron.
A magnet or electromagnet will attract iron but not aluminium.
The advantages of recycling include:
In addition, less energy is usually needed to produce a material by recycling than is needed to produce it from its raw materials.
This table shows the percentage of energy saved by recycling two metals compared to extraction from their ores:
|Metal||Energy saved (%)|
Suggest an explanation for the difference.
Aluminium is extracted from its ore using electrolysis but iron is extracted by heating with carbon. Electrolysis uses more energy, so more energy is used to extract aluminium in the first place. Aluminium has a lower melting point than iron, so less energy is needed to melt it during recycling.
Disadvantages of recycling arise from the recycling process itself: