Extraction of Metals

Ores are naturally occurring rocks that contain sufficient amounts of metals or metal compounds to make extraction worthwhile.
Common ores include bauxite (for aluminium), haematite (iron), and galena (lead).
The use of ores as a source of metals is known as mining.
Processing the ores to extract metals usually includes crushing and grinding the rocks to a fine powder.

The method used to extract a metal depends largely on its reactivity.
Metals more reactive than carbon, such as aluminium and sodium, need to be extracted using electrolysis.
Metals less reactive than carbon, like iron, zinc, copper, can be extracted from their ores by reduction using carbon.
The least reactive metals, such as silver and gold, often exist as native metals and require little or no extraction process.

Electrolysis is the process of breaking down ionic substances into simpler substances using electricity.
In electrolysis, positive metal ions gain electrons at the negative electrode and form metal atoms. This requires energy, hence these metals are difficult to extract.
Electrolysis of aluminium oxide for aluminium extraction occurs in a specially designed cell called a Hall-Héroult cell.

The process of reduction involves removing oxygen from a metal oxide.
In the blast furnace, haematite is reduced to iron. The carbon reduces the iron(III) oxide in the ore to form iron and carbon dioxide.
This method is more cost-effective and energy-efficient than electrolysis which makes it suitable for less reactive metals.

Microorganisms are used to process low-grade ores and waste rock.
Biological methods for extracting metals involve bacteria which convert compounds in the ore into a form that can be more easily processed.
An example of this method is the use of bacterial action in the leaching of copper from low-grade ores.

Mining and extracting metals has a significant environmental impact. These impacts include deforestation, soil erosion, pollution and biodiversity loss.
Sustainable methods and recycling of metals reduces the need for new mines and has less environmental impact.
Field work and data analysis are crucial for identifying the impact of these activities and for the planning and monitoring of restoration efforts.