Extraction of Copper from Oxidised Copper Ore

Aim:
To analyse how copper is obtained from oxidised copper ore using the processes of leaching, solid-liquid separation, displacing and electrowinning.

Method:
Refer to ‘Extraction of Copper from oxidised Copper Ore’ document pages 1-2

Results:
Leaching:
The blue particles in the copper ore which is copper was dissolved in the sulphuric acid and the solution turned into a blue colour. There was also sediment that was floating around in the solution. Solid-liquid separation:

Sedimentation took place and after leaving the beaker for a while, the sediment went from floating around in the beaker to slowly moving towards the bottom of the beaker and settling there. The liquid in the solution remained the blue colour from before. Cementation:

The steel wool turned into a brown colour where it had been in contact with the sulphuric acid with copper dissolved into it. The copper attached onto the steel wool and it was replaced by the steel wool. The liquid was not blue anymore and it was a clear colour. Electrowinning:

Bubbles formed around the electrodes as soon as they entered the solution. Bubbles formed around both of the electrodes but more on the black electrode. The light bulb turned on which meant that electricity was being conducted. The copper plated on the black coloured electrode and the liquid tuned into a greenish colour.

Discussion:
1.During the cementation process (displacement reaction):
a)Why did the solution lose its blue colour over time?

The solution lost its blue colour over time because the solution was originally a clear colour because of the sulphuric acid but during the leaching process, the copper was dissolved into the sulphuric acid giving it its blue colour. During the cementation process, the copper was replaces with the iron as it was more reactive, therefore the copper swapped places with the iron, as shown by the brown colour and then the solution became clear and lost its blue colour. b)Write a balanced equation for the displacement reaction between copper (II) sulphate and iron metal. CuSO4(aq) + Fe(s) FeSO4(aq) + Cu(s)

2.Electrolysis is never used commercially to produce copper. Why? Electrolysis is never used commercially to produce copper because the process is very expensive and it is only ever used when copper needs to be refined to a very pure state and most things that need copper don’t need to be pure as they can be recycled and melted. Electrolysis is only used when copper is needed to be very pure and when profit is gained such as some metals in cars. 3.Which common metal is always extracted from its ore (bauxite) by electrolysis? Why couldn’t we use the cementation (displacement reaction) process that we have used here for this particular ore? The common metal that is always extracted from its ore by electrolysis is aluminium.

The process of cementation cannot be used for this particular ore because unlike copper which is not very reactive, aluminium is a highly reactive metal and to use the process of cementation, a high reacting metal than aluminium would have to be used and it would still be very hard and also very expensive. With copper, it is easier to find a metal that is more reactive so we could use the process of cementation to extract the copper. 4.Copper is sometimes found in ores called pyrites; chalcopyrite or peacock ore (see samples). These are much more pure forms of the metal and require less processing than the extraction of the oxidised mineral we have looked at here. a)What method would be used to extract the copper from these ores (hint: we have discussed this in class)?

The method that would be used to extract copper from these ores is called roasting. Roasting involves the ore being roasted in a furnace with oxygen and during the process; the metal is converted into a copper oxide and then later, the oxide is removed. b)Write a balanced chemical equation for the process used to extract copper from these ores. The balanced chemical equation for the process used to extract copper from these ores is: 4CuFeS2 + SO2 2CuS2 + 2FeO + 2FeS + 2SO2

Conclusion
From this experiment, the extraction of copper was analysed with different processes used. It was found that when copper ore is dissolved in sulphuric acid, the solution would turn a blue colour, and then after that processes, the liquid part could be used in two different methods to extract the copper which are cementation or electrowinning. One part of the method which did not work well was the solid-liquid separation as sediment stuck onto the side of the conical flask and when pouring out the liquid, it brought sand with it. It was found that electrolysis is a very expensive process so it is never used commercially. An improvement is that instead of using the method of electrolysis, cementation could be used as it is easier and it is not so expensive.

Bibliography:

•http://resources.schoolscience.co.uk/cda/14-16/cumining/copch2pg4.html •http://www.chemguide.co.uk/inorganic/extraction/aluminium.html •http://www.citycollegiate.com/IX_copper.htm