Extractive Metallurgy of Magnesium

Fused Salt Electrolysis
Fused salt electrolysis is the process that is used in the extractive metallurgy of magnesium. In this process, the compound from which magnesium is to be extracted is dissolved in a molten salt electrolyte. The compound used for magnesium extraction is usually magnesium chloride (MgCl2) or magnesium oxide (MgO). The molten salt electrolyte is typically a mixture of magnesium chloride and potassium chloride.

Process Explanation
The process of fused salt electrolysis involves the following steps:

1. Preparation of Electrolyte: The electrolyte is prepared by heating a mixture of magnesium chloride and potassium chloride to a high temperature until it becomes molten.

2. Electrolysis Cell Setup: An electrolysis cell is set up, consisting of a container made of a suitable material (such as graphite) that can withstand the high temperatures and corrosive nature of the molten salt electrolyte. The container is filled with the molten electrolyte.

3. Electrodes: Two electrodes are inserted into the molten electrolyte. The cathode is usually a graphite rod, while the anode can be made of either graphite or a more inert material like titanium.

4. Electromagnetic Field: A direct current (DC) is passed through the electrodes, creating an electromagnetic field within the molten electrolyte.

5. Electrolysis: When the current is applied, magnesium ions (Mg2+) from the dissolved magnesium compound migrate towards the cathode (negative electrode), where they gain electrons and are reduced to form metallic magnesium. The chlorine ions (Cl-) from the magnesium compound migrate towards the anode (positive electrode) and are oxidized to form chlorine gas (Cl2).

6. Collection of Magnesium: The metallic magnesium formed at the cathode is collected, usually by draining it from the bottom of the electrolysis cell.

Advantages of Fused Salt Electrolysis
- High purity: Fused salt electrolysis allows for the production of high-purity magnesium.
- Energy efficiency: This process is relatively energy-efficient compared to other methods of magnesium extraction.
- Scalability: Fused salt electrolysis can be easily scaled up for large-scale production of magnesium.

Conclusion
Fused salt electrolysis is the preferred process for the extractive metallurgy of magnesium. It involves the dissolution of a magnesium compound in a molten salt electrolyte and the application of a direct current to extract metallic magnesium at the cathode. This process offers advantages such as high purity, energy efficiency, and scalability.