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Metallothermic reduction

Principle

Metallothermic reduction uses certain metals (such as calcium, magnesium, aluminum, and sodium) as reducing agents to reduce oxides, salts, or other compounds of the target metal to its elemental form.

The key point is:

The reducing metal has a stronger chemical affinity for the non-metallic elements (such as oxygen, sulfur, and halogens) in the compound than the target metal.

As a result, the target metal is "released," while the reducing agent combines with the non-metallic element to form a stable compound.

Typical Reducing Agents

Calcium (Ca)

Magnesium (Mg)

Aluminum (Al)

Sodium (Na)

Process Characteristics

Because both the reducing agent and the resulting metal react violently with oxygen in air, the process must be performed under one of the following conditions:

1. Vacuum environment

2. Reducing medium (to prevent oxidation)

3. Inert gas shielding (such as argon)

This method is known as thermal reduction or metallothermic reduction in practice. Notable applications include:

Aluminothermic process: Iron is produced by reducing iron oxide with aluminum powder (exothermic and often used for welding rails).

Magnesothermic process: Used to prepare reactive metals such as titanium, zirconium, and hafnium.