Ores and Metallurgy
3.0 Metallurgy
3.0 Metallurgy
The process of extracting a metal from its ore is called Metallurgy.
Classification:
1. Pyro Metallurgy: If heating is involved in extraction of metals from its oxides. Example: $Pb$, $Cu$, $Fe$, $Zn$, $Mn$.
2. Hydro Metallurgy: It involves the solution of metallic ore in suitable chemical reagent in which metallic ore is soluble and impurity is insoluble and metal is further precipitated for filtered by treating it with more electro-positive metal by displacement method. Example: $Au$, $Ag$.
3. Electro Metallurgy: Electrolysis is involved in electro metallurgy. Example: $s$-block elements.
Different reduction methods are involved for different metals in electro-chemical series:
- For highly reactive metals (alkali metals, alkali earth metals, aluminium): Electrolysis is used.
- For moderate reactive metals ($Mn$, $Zn$, $Cr$): Aluminium reduction is used which is a part of pyro metallurgy.
Thermite Process (used in welding): In this reaction, $Al$ is a very strong reducing agent.$$Al + F{e_2}{O_3} \to A{l_2}{O_3} + Fe\quad \left( {\Delta H = - ve;\;{\text{Exothermic Reaction}}} \right)$$
- For weak reactive Metal:
$Fe$, Tin, $Zn$: Carbon reduction method is used.
$Cu$: Self reduction/Auto reduction method is used.
$Pb$: Both Carbon reduction and Self reduction are used.
- For noble metal ($Ag$, $Au$): Hydro metallurgy is used.
