Copper is purified by electrolysis. This process uses electricity to refine the metal.
Electrolytic Purification of Copper Explained
The process of electrolytic copper refining involves using an electrolytic cell with a copper-containing solution.
The Electrolytic Cell Setup:
- Anode: Impure copper serves as the anode (positive electrode).
- Cathode: A thin sheet of pure copper acts as the cathode (negative electrode).
- Electrolyte: A solution of copper sulfate ($CuSO_4$) functions as the electrolyte, conducting electricity between the electrodes.
The Electrolysis Process:
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Dissolving the Impure Copper: When an electric current is passed through the cell, the impure copper anode dissolves into the copper sulfate solution, releasing copper ions ($Cu^{2+}$).
$Cu(s) \longrightarrow Cu^{2+}(aq) + 2e^-$
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Selective Deposition: The copper ions ($Cu^{2+}$) in the solution migrate towards the cathode. Here, they gain electrons and deposit as pure copper onto the cathode.
$Cu^{2+}(aq) + 2e^- \longrightarrow Cu(s)$
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Impurities Settling: Impurities present in the impure copper anode, such as gold, silver, and platinum, do not dissolve in the electrolyte. Instead, they fall to the bottom of the cell as "anode sludge," which can be further processed to recover these valuable metals.
Simplified Process in Bullet Points:
- Electricity is passed through copper sulfate solution ($CuSO_4$).
- At the anode (impure copper), copper dissolves into the solution as copper ions.
- At the cathode (pure copper), copper ions from the solution deposit as pure copper.
- Impurities from the anode settle as "anode sludge".
Example: Copper Sulfate Electrolysis
In a typical copper purification setup, electricity is passed through solutions containing copper compounds, such as copper sulfate. The copper ions in the solution are attracted to the cathode, where they are reduced to form pure copper metal. Meanwhile, at the anode, copper from the impure copper electrode dissolves into the solution to replace the copper ions that were plated onto the cathode.
