Extractive metallurgy

Extractive metallurgy is the practice of extracting metal from ore, purifying it, and recycling it.

Related Topics:
Metallurgy - Metal - Ore

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Most metals found in the Earth's crust exist as oxide and sulfide minerals. These compounds must be reduced to liberate the desired metal. There are two methods of reduction: electrolytic and chemical.

Related Topics:
Metal - Earth - Crust - Oxide - Sulfide - Mineral - Reduction - Electrolytic - Chemical

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Chemical reduction can be carried out in a variety of processes, including reductive smelting - the process of heating an ore with reducing agent (often, coke or charcoal) and purifying agents to separate the pure molten metal from the waste products. Some other processes for chemical reduction include autoclave hydrogen reduction and converting. The latter though does not produce the pure metal, therefore requiring further treatment of its product.

Related Topics:
Smelting - Reducing agent - Coke - Charcoal - Purifying - Autoclave - Converting

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Electrolytic reduction involves passing a large current through a molten metal oxide or an aqueous solution of the metal's salt. For example, aluminium is electrolysed from bauxite dissolved in molten cryolite via the Hall-Héroult process.

Related Topics:
Electrolytic - Aluminium - Bauxite - Cryolite - Hall-Héroult process

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Prior to reduction, it is often necassary to separate metal compounds to exclude co-reduction of different metals and contamination of the product. There is a great variety of separation processes: roasting, oxidative smelting, converting, leaching and many others.

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Extractive metallurgical technologies are divided into mineral processing, hydrometallurgy and pyrometallurgy areas.

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Extractive metallurgical and mineral dressing operations are divided into:

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• Ferrous metallurgy, which includes reduction of iron ore into iron, and further refinement and alloying with other metals to make steel.
• Non Ferrous metallurgy, which includes all other metals. This can be further broken down into:
• Precious metals. The recovery of gold and silver and the platinum group metals.
• Base metals. The recovery of lead, zinc, copper, and nickel.
• Light metals. The recovery of magnesium, aluminium, tin, and titanium.
• Minor elements. The recovery of arsenic, selenium, bismuth, tellurium, and antimony.
• Industrial minerals. Major examples include clays, sands, silicates, and heavy mineral sands
• Coal. The benficiation and treatment of coal.
• Gems and precious minerals. The recovery of emeralds, diamonds, sapphires, rubies, and others.
 
Extractive metallurgy: Mineral processing ►