Extractive Metallurgy Main Processes

Hydrometallurgy

Purpose: Involves using aqueous solutions to dissolve targeted minerals into a liquid state Steps: Broken rocks are placed on a heap leach pad and dripped with a chemical solution. A rubber lining at the bottom of the leach pad collects the solution with dissolved metals (called a "precipitate"). It is further treated through electrometallurgical processes to make a semi-refined product. Examples: Copper oxide ores are treated on a copper leach pad to make copper cathodes using hydrometallurgy and electrometallurgy. Precious metals can be treated in a similar manner.

Pyrometallurgy

Purpose: Uses high temperatures to extract metals from ores and waste streams. Used in recycling electronic waste or spent automotive catalysts, extracting base and precious metals from ore, and commercial production of metals and alloys. Steps: Roasting (heating in air to convert sulfide ores into oxides), smelting (used to reduce iron ores, as well as tin, copper and lead ores), and incineration and sintering (a thermal treatment used in the pyrometallurgical process) Example: Pyrometallurgical processes are often carried out in specialized furnaces, such as blast furnaces or plasma arc furnaces.

Mineral Processing

Purpose: To increase the concentration of valuable minerals Steps: Crushing, grinding, flotation, and magnetic separation Example: Gold ore benefication

Electrometallurgy

Purpose: Is a technique that uses electricity to extract, refine, and produce metals. It is used for a variety of purposes including: electrowinning, electroplating, electrorefining, and electroforming.

Steps: In electrowinning, an electrical current is passed from an inert anode through a leach solution containing the dissolved metal ions to recover the metal as it is reduced and deposited in an electroplating process onto the cathode. In electrorefining, the anode consists of the impure metal (e.g., copper) to be refined. The impure metallic anode is oxidized, and the metal dissolved into a solution (called an "electrolyte"). The metal ions migrate through the electrolyte toward the cathode, where the pure metal is deposited. Example: Electrometallurgy is often used at the end of the process to produce high-purity metallic products like, precious metals, copper, magnesium, and aluminum.