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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