Lesson 3: Conversion of Ore to Metal
This lesson focuses on the core reduction step, where the concentrated ore is converted into its metallic form.
- Calcination: This process involves heating a carbonate or hydroxide ore in a limited supply of air or oxygen to a high temperature. It removes volatile impurities and converts the ore into a more reducible oxide. For example, .
- Roasting: This process involves heating a sulfide ore in the presence of excess air at a high temperature. It converts the sulfide ore into an oxide, which is easier to reduce. For example, .
- Smelting: This is a pyrometallurgical process where the roasted or calcined ore is heated with a flux and a reducing agent (e.g., carbon) in a furnace. The flux combines with the gangue to form a fusible material called slag. For example, in iron metallurgy, limestone () acts as a flux.
- Electrolytic Reduction: This method is used for highly reactive metals (e.g., Al, Na, K) that cannot be reduced by carbon. The metal is extracted from its molten salt or ore by passing an electric current through it. The Hall-Héroult process for aluminum extraction is a classic example
