Metallurgy

Metallurgy

Metallurgy is an art, science and technique of extracting metals from their ores and to give them certain desired properties for use.

Steps for Metal Extraction:

Steps taken for the Extraction of metals from their ores are as follows:

1. Pulverization or Crushing or Grinding of ore :

It is a mechanical process used to convert huge lumps of ore into powdered form. 

Another process comes just after crushing the ore is sewing which means to separate particle ores from undesired particles. 

2. Concentration of Ore (Benefication, dressing or conditioning of ore) :

This process involves the concentration of ores i.e separation of ores from hard impurities.

(a) Lavigation or Gravity Suppression:

This process is generally used for oxide ore and is used when impurity and ore particles are differ by weight. 

(b) Froth-Floatation Process:

This process is generally used for sulphide ores. The ore particles is separated from impurities by adding oil and water. After agitation, the ore particles is separated easily.

(c) Magnetic Separation:

This process is generally used for magnetic powdered ores like W, Fe, etc. 

(d) Leeching or Hydro-metallurgy:

This process is used for the concentration of native metals like Au, Cu, Ag, etc. This can be done by adding desired soluble complex which displace the desired metal from complex and in this way native metals are concentrated.

3. Pyrometallurgy:

This is a high temperature process. This includes high temperature for the conversion of ore to oxide ore.

(a) Roasting:

In this process, the ore is heated below its melting point in the presence of large amount of oxygen supply and is only done for sulphide ores. 

2PbS + 3O2 → 2PbO + 2SO2

(b) Calcination:

In this process, the ore is also heated below its melting point but is done in the absence of oxygen and is done only for carbonate ores. 

ZnCO3 → ZnO + CO2

4. Reduction of Oxide Ore to Metal:

Metals are formed from reduction. So we converted the ore to the oxide form to get metal from reduction.

(a) Smelting:

It is a process for the production of metal or metal rich phase known as matte along with gangue particles known as Slag. Reduction of metal oxide is done by smelting process. The reducing agents used in smelting process is charcoal, carbon, coke, etc. 

(b) Electrometallurgy or Electrolysis:

This process is used for the reduction of alkali or alkaline earth metals. These metals are taken in electrolytic tank with electrolytes and metal is made deposited on the cathode. 

(c) Hydro-metallurgy or Leeching:

This process is used for the concentration of native metals like Au, Cu, Ag, etc. This can be done by adding desired soluble complex which displace the desired metal from complex and in this way native metals are concentrated.

Ag-complex + Zn → Zn-complex + Ag

5. Electrolytic Refining:

This involves the refining of metal from electrolysis. In this process, anode is made of impure metal and cathode is made of pure taken metal. And, we start electrolysis and this way metal is refined to a desired value.