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