Name the main method of purification employed for the purification of `Cu`, `Zn` and `Al`.

Explanation

To answer the question regarding the main method of purification employed for the purification of Copper (Cu), Zinc (Zn), and Aluminium (Al), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Metals**: The metals in question are Copper (Cu), Zinc (Zn), and Aluminium (Al).

2. **Determine the Purification Method**: The main method of purification for these metals is **electrolytic refining**. This method is also referred to as **electrolysis**.

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