21.5: Ore Extraction
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How can you save energy and materials?
Getting ore from rock takes a lot of energy. Getting ore from preexisting materials uses a lot less. It turns out that if you recycle just 40 aluminum cans, you will save the energy in one gallon of gasoline. You will save aluminum too!
When the ore leaves the mine, it is not yet a useful material (Figure below). Most ores are a combination of metal and other elements. The rocks are full of valuable minerals. They also contain rock that isn't valuable, which is called waste rock. The valuable minerals must be separated from the waste rock.
Enormous trucks haul rock containing ore from a mine site to where the rock is processed.
To separate the ore from the waste rock, first the rocks are crushed. Then the minerals are separated out of the ore. There are a few methods for doing this:
- Heap Leaching: the addition of chemicals, such as cyanide or acid, to remove ore. This is often done at very high temperatures.
- Flotation: the addition of a compound that attaches to the valuable mineral and floats.
- Smelting: roasting rock at a temperature greater than 900oC. This causes it to segregate into layers. The valuable minerals are then extracted. This requires a lot of energy.
Extracting metal from rock is so energy-intensive that it's much better to recycle. We use over 80 billion aluminum cans each year. If all of these cans were recycled, we would save the energy in 2 billion gallons of gasoline!
- To extract ore from rock, the rock is first crushed.
- Ore is extracted from rock by heap leaching, flotation, or smelting.
- Extracting ore from rock can take a lot of energy.
- Why does ore need to be extracted from rock?
- How is ore extracted from rock?
- Why does extracting ore from rock take a lot of energy?