Q:

How are metals extracted from their ores?

A:

Metal extraction from ores occurs in many different ways involving physical, chemical and electrical means. Even ores of the same metal sometimes require different methods of separation depending on the concentration of the metal and its chemical composition within the ore.

Ores are naturally occurring sources of metal. From a practical standpoint, ores include materials from which extracting the metal is economically feasible. Aluminum is the most common metal in the Earth's crust. However, all sources of aluminum are not equal. Due to the high cost of refining and the relatively low value of the metal, extraction is limited to bauxite, an aluminum ore containing 50 to 70 percent of aluminum oxide.

Copper ores generally contain sulfides or oxides and copper in the 0.5 to 2.0 percent range. Because of the greater value of copper metal, refining ores at these levels is profitable. Refiners crush copper sulfide ores mechanically and use froth floatation to bring copper-containing particles to the surface of a water solution. The material is then heated to over 930 degrees Fahrenheit to burn off the sulfur and create 60 percent pure copper in a calcine mixture of copper oxides and sulfides. The calcine mixture is heated again to over 2100 degrees Fahrenheit with a flux. At this temperature, slag floats to the surface and workers skim it away. Refiners oxidize the liquid copper to remove iron and remaining sulfur components, resulting in 97 percent pure copper. Electroplating is the final step in producing 99.99 percent pure copper. Processing copper oxides requires a completely different process, involving leaching.

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