Electrolysis refines copper by using an electrochemical process to separate pure copper from impure copper.
Electrolytic Refining of Copper Explained
Electrolytic refining is a process where electricity is used to purify copper. This method is based on the principle that when an electric current is passed through an electrolyte solution containing copper ions, copper will dissolve from an impure copper anode and deposit as pure copper onto a cathode.
The Process: A Step-by-Step Guide
The refining of copper through electrolysis involves the following key steps:
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Electrolyte Preparation: An acidified copper sulphate solution acts as the electrolyte.
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Setting up the Electrolytic Cell:
- Anode: The anode is made of impure copper.
- Cathode: The cathode is made of pure copper.
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Applying Electric Current: When electricity is passed, the following reactions occur:
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At the Anode (Oxidation): The impure copper from the anode gets dissolved in the electrolyte. Copper atoms lose electrons and become copper ions (Cu2+).
Cu(s) → Cu2+(aq) + 2e-
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At the Cathode (Reduction): Pure copper gets deposited on the cathode. Copper ions from the electrolyte gain electrons and become solid copper atoms.
Cu2+(aq) + 2e- → Cu(s)
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Summary in Table Format
| Component | Description |
|---|---|
| Electrolyte | Acidified copper sulphate solution |
| Anode | Impure copper |
| Cathode | Pure copper |
| Anode Reaction | Impure copper dissolves into the electrolyte as copper ions (Cu → Cu2+ + 2e-) |
| Cathode Reaction | Copper ions from the electrolyte deposit as pure copper on the cathode (Cu2+ + 2e- → Cu) |
Impurities
During electrolysis, impurities present in the impure copper anode behave differently:
- More Reactive Metals: Metals more reactive than copper (e.g., zinc, iron) also dissolve into the electrolyte as ions. However, under the specific conditions, these ions do not get deposited at the cathode.
- Less Reactive Metals: Less reactive metals (e.g., gold, silver, platinum) do not dissolve and instead collect as "anode sludge" at the bottom of the electrolytic cell. This sludge is valuable as it contains precious metals that can be recovered.
Outcome
The result of this process is a high purity copper cathode, often reaching 99.99% purity. Electrolytic refining is essential in producing copper for electrical applications where high conductivity is crucial.
