Recycling
When evaluating whether it is viable to recycle materials it is necessary to consider:
- balancing the use of the raw materialBasic material that goods are made from such as crops, metals, wood and animal products such as wool and leather., such as finiteSomething that has a limited number of uses before it is depleted. For example, oil is a finite resource. resources like crude oil or metal ores, with the need to conserve their supply
- availability of the material to be recycled
- economical and practical issues with collecting the material
- removal of impurities
- energy use for transport and processing
- environmental impact of the processes
- level of demand for the recycled material
Recycling metals
recyclingReusing materials or reprocessing waste materials to produce new materials. a metalShiny element that is a good conductor of electricity and heat, and which forms basic oxides. involves collecting used metal items and producing new metal from them. The steps usually needed are:
- collecting used items and transporting the used items to a recycling centre
- breaking up the items and sorting the different metals
- melting the metal and removing impurities from the moltenA term used to describe a liquid substance (eg rock, glass or metal) formed by heating a solid. metal
- solidifying the metal in ingots (slabs of metal)
The ingots can then be used to manufacture new metal items.
Advantages of recycling
The advantages of recycling compared to producing metals from metal oreA rock containing enough quantities of a mineral for extraction to be possible. include:
- fewer quarryAn area of land that is used to remove rocks for use in industries. and mines are needed
- less noise, dust and heavy traffic are produced
- smaller areas of natural habitatA place where plants, animals and microorganisms live. are damaged
- metal ores are conserved so will last longer
In addition, less energyThe capacity of a system to do work or the quantity required for mechanical work to take place. Measured in joules (J). For example, a man transfers 100 J of energy when moving a wheelbarrow. is usually needed to produce a metal by recycling than is needed to produce it from an ore.
Question
This table shows the percentage of energy saved by recycling compared to extractionThe process of obtaining a metal from a mineral, usually by reduction or electrolysis. from a metal ore:
| Metal | Energy saved (%) |
| Iron | 70 |
| Aluminium | 92 |
| Metal | Iron |
|---|---|
| Energy saved (%) | 70 |
| Metal | Aluminium |
|---|---|
| Energy saved (%) | 92 |
Suggest an explanation for the difference.
Aluminium is extracted from its ore using electrolysisThe decomposition (breakdown) of a compound using an electric current. 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
Disadvantages of recycling arise from the recycling process itself:
- the collection and transport of used items needs organisation, workers, vehicles and fuel
- it can be difficult to sort different metals from one another
- the sorted metal may need to be transported to where it can be turned into ingots
Question
Describe a simple way to separate aluminium from iron.
A magnet or electromagnetA magnet made by wrapping a coil of wire around an iron bar and passing an electric current through the coil. will attract iron but not aluminium.