ZIMSEC O Level Combined Science Notes:Extraction of copper from sulphides

  • Copper is extracted from various types of ore including sulphide ores
  • For example copper ores found on the Great Dyke near Mhangura is of the sulphide type
  • Once the sulphide ore is extracted from the earth
  • It is crushed to form a very fine powder which is then further refined using
  • The flotation process  or the concentration process
  • This is done in flotation/concentration plants
  • The powder is mixed with water and the slurry (porridge) is agitated by passing air through it
  • A foaming agent is added to make bubbles
  • These bubbles attract the fine particles containing copper bearing minerals
  • The front on the surface is skimmed off, filtered and then dried
  • The concentrated material from the flotation plant is then transported to the smelter
  • In Zimbabwe some of the copper is smelted at Alaska mine
  • The concentrate is roasted to burn off some of the sulphur and then smeleted in a furnace using limestone as a flux
  • Flux is a material used to purge impurities from another metal (copper in this case) during the smelting process
  • The sulpher burns off as a gas:
  • \text{copper sulphide+oxygen}\rightarrow\text{copper+sulpher dioxide}
  • Slag which contains most of the unwanted impurities forms a layer at the top of the molten copper and is tapped off
  • The remaining mixture is known as matte
  • It contains most of the copper, iron and sulpher
  • It is transferred to a converter
  • In the converter air is blown through the molten matte, thus oxidizing the iron to form iron oxide slag and
  • the sulpher escapes as a gas sulpher dioxide
  • The resulting metal formed as a result of the process is known as blister copper
  • This is because many blisters are formed on the surface of the metal
  • as gases escape while the copper cools and solidifies
  • The process from the extraction of the copper up until it is turned into blister copper can be summarized as shown below:
  • \text{extraction}\rightarrow\text{flotation plant}\rightarrow\text{roasting}\rightarrow\text{smelting}\rightarrow\text{converter}\rightarrow\text{blister copper}

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