Final answer:
Electro-refining is a process that purifies metals using an electrolytic cell where an electric current causes the impure metal to dissolve from the anode and redeposit in a pure form on the cathode, commonly used for metals like copper to achieve high purity.
Step-by-step explanation:
Electro-refining is an electrochemical process used to purify metals. In this process, impure metal is used as the anode, and a refined pure metal as the cathode. When an electric current is applied, the impure metal dissolves from the anode and deposits in a pure form onto the cathode. This technique is often employed for metals such as copper, where the refined metal is required to have a high degree of purity for electrical applications.
The refining process includes an electrolyte bath that typically contains a soluble form of the same metal. For example, copper electro-refining might use a copper sulfate solution. As electric current passes through the solution, impurities from the anode either fall away to collect at the bottom of the tank or remain in the electrolyte solution. These impurities are referred to as the 'anode slime' and can contain valuable metals like silver and gold, which may be recovered separately.
An important aspect of electro-refining is that it helps in achieving incredibly high purity levels that are difficult to obtain by other means. It also ensures that the final product has improved electrical properties, which is crucial in many applications including wiring and electronic components.