Extractive metallurgy deals with the extraction of metals from naturally occurring compounds and the subsequent refinement to a purity suitable for commercial use. These operations, known as refining of metals, follow mining and beneficiation of the ore (see Figure). The selection and design of the extractive processes depend on the raw materials available, and conditions for the refining steps are related to the ultimate use of the metal. Production of a metal is usually achieved by a sequence of chemical processes represented as a flow sheet.
Extractive metallurgy is usually divided into three principal areas:
- Hydrometallurgy: These are the wet methods, characterized by the use of aqueous solutions and inorganic solvents to achieve the desired reactions. It is usually conducted at ambient conditions but also sometimes at the boiling point of the solution and under pressure.
- Pyrometallurgy: These are the dry methods, which consist of high temperatures processes to carry out smelting and refining reactions.
- Electrometallurgy: These are the processes based on the use of electric current for effecting a chemical transformation for metal recovery or refining. Electrometallurgy may be carried out either at high temperatures or in aqueous solution.
An integrated metallurgical flowsheet may include pyrometallurgical, hydrometallurgical, and/or electrometallurgical steps.
The pure metal obtained is treated by various specialists before marketing. The specialists include physical metallurgists, mechanical metallurgists, engineering metallurgists, and powder metallurgists (see Figure). Industrial minerals may be a by-product of extractive metallurgical processes or an ore may be treated specifically for their recovery.
- Duby, Paul F. “Metallurgy, Extractive.” KirkâOthmer Encyclopedia of Chemical Technology (2000).
