C1 3.4: Extracting copper

• The two main methods for extracting copper from copper-rich ores are:

Sulphuric acid is added to produce copper sluphate solution, then the copper is extracted .Smelting (roasting)- copper ore is heated strongly in a furnace with air to produce crude copper.

• E.g. Copper can be found in an ore called chalcocite (contains copper (l) sulfide). If heated in air, it decomposes to give copper metal:

Copper (l) sulfide + oxygen → copper + sulfer dioxide.

• Then impure copper as the positive electrode in electrolysis cells is used to make pure copper.
• Metal ions are always positively charged so in electrolysis they are attracted to the negative electrode.
• This means that metals are always decomposed at the negative electrode.
• Electrolysis is also used to purify the impure copper extracted by smelting.
• Copper can also be extracted from copper sulfate solution by adding scrap iron because iron is more reactive than copper so it can displace the copper from its solutions:

Iron + copper sulfate → iron sulfate + copper

• Scientists are developing new ways to get copper from low-grade ores.
• Bacteria (bioleaching) and plants (phytomining) can be used to extract copper.

Phytomining:

• Plants can absorb copper ions from low grade copper ore as they grow, the plants are then burnt and the copper is extracted from the ash.
• Copper ions can be dissolved from the ash by adding sulfuric acid making the solution copper sulfate.
• Displacement by scrap iron and electrolysis can be used to extract the pure copper metal.

Bioleaching:

• Bacteria feed on low grade metal ores.
• By a combination of biological and chemical processes, a solution of copper ions can be gained from waste copper ore.
• 20% of copper comes from bioleaching.