In-situ Leach - Copper

Copper

In-situ leaching of copper was done by the Chinese by 977 AD, and perhaps as early as 177 BC. Copper is usually leached using acid (sulfuric acid or hydrochloric acid), then recovered from solution by solvent extraction electrowinning (SX-EW) or by chemical precipitation.

Ores most amenable to leaching include the copper carbonates malachite and azurite, the oxide tenorite, and the silicate chrysocolla. Other copper minerals, such as the oxide cuprite and the sulfide chalcocite may require addition of oxidizing agents such as ferric sulfate and oxygen to the leachate before the minerals are dissolved. The ores with the highest sulfide contents, such as bornite and chalcopyrite will require more oxidants and will dissolve more slowly. Sometimes oxidation is speeded by the bacteria Thiobacillus ferrooxidans, which feeds on sulfide compounds.

Copper ISL is often done by stope leaching, in which broken low-grade ore is leached in a current or former conventional underground mine. The leaching may take place in backfilled stopes or caved areas. In 1994, stope leaching of copper was reported at 16 mines in the US. At the San Manuel mine in the US state of Arizona, ISL, underground mining, and open-pit mining were being done simultaneously in different parts of the same ore body.