Which of the following process is used in the extractive metallurgy of magnesium?

Fused salt electrolysis

The correct answer is option 1. Fused salt electrolysis.

The correct process used in the extractive metallurgy of magnesium is Fused salt electrolysis.

Magnesium is typically extracted from its ores using fused salt electrolysis, also known as the Pidgeon process or the Magnetherm process. In this process, magnesium oxide \((MgO)\) is reduced to magnesium vapor by heating it with ferrosilicon or other reducing agents in a high-temperature electric furnace. The magnesium vapor is then condensed to produce magnesium metal. This method is efficient for producing high-purity magnesium.

The other options:

(2) Self reduction - This process involves the reduction of a metal oxide by the metal itself, which is not commonly used for magnesium extraction

(3) Aqueous solution electrolysis - This process involves the electrolysis of an aqueous solution, which is not typically used for magnesium extraction.

(4) Thermite reduction - This process involves the reduction of a metal oxide by aluminum in a highly exothermic reaction, which is not commonly used for magnesium extraction.

Therefore, the correct answer is option (1) Fused salt electrolysis.

Additional Information

The extractive metallurgy of magnesium involves the process of converting magnesium compounds, typically magnesium oxide (MgO) found in minerals like magnesite or dolomite, into elemental magnesium metal. Among the various methods available, the primary process used for magnesium extraction is fused salt electrolysis, also known as the Pidgeon process or the Magnetherm process.
Here's how fused salt electrolysis works in the extractive metallurgy of magnesium:

1. Preparation of Feedstock: The process starts with obtaining a suitable source of magnesium oxide \((MgO)\), which is typically obtained from minerals like magnesite or dolomite.

2. Reduction in High-Temperature Furnace: The magnesium oxide is mixed with a reducing agent, often ferrosilicon (an alloy of iron and silicon) or a similar material, to facilitate the reduction process. This mixture is then heated in a high-temperature electric furnace.

3. Formation of Magnesium Vapor: At the high temperatures inside the furnace, the reducing agent reacts with the magnesium oxide, causing it to be reduced to magnesium vapor according to the following reaction:
   \( \text{MgO} + \text{Si} \rightarrow \text{Mg(g)} + \text{SiO}_2 \)

4. Condensation of Magnesium: The magnesium vapor produced in the reaction is then allowed to condense in a separate chamber of the furnace or in a condenser, where it solidifies into pure magnesium metal.

5. Collection and Further Processing: The solidified magnesium metal is collected, often in the form of ingots, and subjected to further purification and processing steps as needed to meet desired quality standards.

The use of fused salt electrolysis offers several advantages for magnesium extraction:

It allows for the production of high-purity magnesium metal.

It can be scaled up for large-scale industrial production.

It offers relatively high energy efficiency compared to alternative methods.

Other methods such as self-reduction, aqueous solution electrolysis, and thermite reduction are not commonly used in the extractive metallurgy of magnesium due to various limitations such as efficiency, purity, and practicality.

In summary, fused salt electrolysis is the primary process used in the extractive metallurgy of magnesium, offering an efficient and scalable method for producing high-quality magnesium metal from its compounds.