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1. Different process involved in metallurgical process
The various processes involved in the extraction of metals from their ores and refining are
known as metallurgy. The compounds of various metals mixed with impurities and found in
nature are called minerals. The naturally occurring metals from which metal can be extracted
profitably and conveniently are called ores.
Different process involved in metallurgical process
The process of extracting a metal from its ore and refining it, is called metallurgical process or
simply as metallurgy.
The actual process of extraction of a metal from its ore depends upon the nature of the ore
and the metal. There is no universally operational method for the extraction of metals.
Metallurgy is of three types
A. Pyro metallurgy: –itisthemethod ofextractionof metalsfromthe ore by chemical reduction
at very high temperature.
B. Electro metallurgy:-it is the method of extraction of metals from the ore by electrolytic
reduction in molten state or in aqueous solution.
C. Hydro metallurgy: – it is the method of extraction of metals from the ore by dissolving the
ore with suitable reagent and subsequent precipitation of the metal by
other active metal.
Certain common steps however, are involved in all metallurgical processes.
Steps involved in a metallurgical process
The extraction of a metal from its ore involves the following steps:
a. Mining of ore:
Most ores generally occur deep inside the Earth. Some may occur only a few metres under
the earth's surface. 'Mining' is the process of taking out the ores from the mines. When an
ore occurs near the surface of the Earth, it can be directly dug out.
b. Crushing of the ore:
Extracted ore often occurs in big lumps. It is essential to break it into smaller pieces. The
lumps are crushed to smaller pieces by hammering in a hammer mill or by help of a jaw-
crusher.
c. Grinding and pulverization of the crushed ore:
The crushed ore is then finally pulverized to fine powder state in a stamp mill or a pulveriser.
d. Concentration of theore(ore dressing)
The removal of the undesired foreign impurities i.e., gangue, from the ore is called
concentration of the ore. Either of the following methods is used for concentrating the ores:
1. Hand picking:
If the impurities present are quite distinct from the ore, and are of large size, these may be
removed by hand picking. This method is slow and is generally adopted in the initial stages of
concentration.
2. Gravity or levigation method: The gravity separation is based on the difference in the
density of the ore and the impurities. This method of separation is used for the

2. concentration of oxides ores like bauxite,Al2O3.2H2O, heamatite,Fe2O3etc.In this
process the powdered ore is washed with running stream of water. The heavy ore
particles settle down while lighter impurities are washed away( as shown in diagram).
The powdered ore is dropped from the top, and a streamof water is pushed in fromthe
bottom. The lighter gangue is washed away by water and the heavier ore particles settle down,
and are removed.
.
Fig: gravity seperation
3. Magneticseparation:
Magnetic separation is done especially in the case of haematite ore, whereby the powdered
ore is dropped on to leather or brass conveyer belt, which moves over two rollers one of
these rollers, is magnetic. When the ore passes over the magnetic roller, it sticks to the belt
due to the force of attraction and falls nearer due to the force of attraction of the
magnetized roller. The gangue falls over readily, further away. The ore and the magnetic
impurity are collected as two separate heaps.
Fig: - Magnetic separation
4. Froth flotation process:
This process is used for concentrating sulphide ores, as such ores are preferentially wetted by
oil while the gangue particles are wetted by water. Powdered ore is mixed with water and a
little pine oil and the mixture is vigorously stirred by passing compressed air. The froth, which

3. is produced rises to the surface and carries the ore particles along with it. The gangue is left
behind
Fig: 10.5 - The froth flotation process
5. Leaching process
In this method, the ore is treated chemically with a suitable reagent that preferentially
dissolves the active component of the ore. The concentrated ore form is then recovered from
the solution by a suitable chemical method.
A typical example of ore concentration by leaching process is the purification of bauxite using
NaOH solution as a leachant. The Bauxite is digested with concentrated solution of caustic
soda at 150°C in an autoclave. The Aluminium oxide dissolves in NaOH leaving behind the
insoluble impurities, which are removed by filtration.
The solution of NaAlO2 (sodium meta-aluminate) is then treated with freshly prepared
Al(OH)3 when the entire aluminium in the solution gets precipitated as Al(OH)3
The precipitate of Al(OH)3 is removed, washed and dried to get Al2O3.
e. Calcination:
The concentrated ore is converted into oxide by calcination i.e., heating it strongly in the
absence of air or roasting (heating it strongly in presence of air). This helps in removing
volatile impurities like CO2, SO2, organic matter, and moisture from the ore. For example,
 It removes moisture from bauxite.
 It removes CO2 from carbonate ores e.g.,
f. Roasting:
In this process the ore (usually sulphide) is heated strongly, in the presence of excess of air
but below its melting temperature. The result is
 It removes moisture, CO2, SO2 and organic matter.
 The sulphide ore is converted partly into its oxide or sulphate i.e.,

4. g.Reduction–Inthisprocess the metal oxideobtained fromroasting or calcination isturned
into free metal by the reduction with different reagents according to the nature of the ore.
1. Carbon reduction (smelting) is a process in which carbon used for the reduction of fused
metal oxide into free metals. This method is used for the extraction of metals like iron, copper,
zinc, tin. In this process roasted or calcined ore is mixed with suitable quantity of coke or
charcoal and heated to a very high temperature. This method is also called as smelting. This
process is carried mainly out in a blast furnace in a controlled supply of air.
ZnO + C → Zn + CO
SnO2 + 2C → Sn + 2CO
PbO + C → Pb + CO
Fe2O3 + 3C → 2Fe + 3CO
During reduction, an additional reagent is also added to the ore to remove the impurities still
present in the ore. This additional reagent is called flux. Flux combines with the impurities to
form a fusible product called slag.
Flux + Impurities → Slag
The selection of flux depends upon the nature of impurities. If impurities are acidic in nature,
the flux is basic, lime (CaO). On the other hand, for basic impurities, are acidic flux such as
silica (SiO2) is used.
CaO + SiO2 → CaSiO3
Differences between flux and slag
flux slag
1. Flux is a chemical substance
that is added along with
carbon during smelting to
remove infusible impurities in
order to form the fusible mass.
2. It may be acidic or basic.
3. . Example of flux are CaO , FeO
, SiO2
1. Slag is a chemical substance that is
formed by the combination of the
infusible impurities present in the ore
and a flux which is lighter than molten
metal.
2. It is neutral compound.
3. Example of flux are CaSiO3 , FeSiO3 .

5. Slag is important in metallurgy because being fusible mass it helps to remove infusible
impurities from the concentrated ores during metallurgy.
2. Aluminothermy process –The process of reduction of a metal oxide to the metal with the
help of aluminium powder as the reducing agent is called (aluminothermy or Goldschmidt)
thermite process. Aluminium is used as a reducing agent for the extraction of chromium,
manganese from their respective oxides because aluminium is more electro positive then
chromium and manganese.
2Al + Cr2O3 → Al2O3 + 2Cr
8Al + 3Mn3O4 → Al2O3 + 9Mn
Refining of metals: poling, electro-refinement
Purification of the metal is the last step in metallurgy.
Refining is based on the difference between the properties of metals and their impurities.
Liquation
This method is used for refining metals having a low melting point.
e.g., tin, lead, bismuth

6. Liquation
Process
1. The metal to be refined is placed over the sloping hearth of a furnace
2. The temperature of the furnace is maintained slightly above the melting point of
the metal
3. Pure metal melt and flow down
4. Impurities, having higher melting point, are left behind
Distillation
This method is used for volatile metals having boiling points lower than their impurities. e.g.,
zinc, mercury.
Process
1. The metal to be refined is heated above its boiling point
2. Impurities do not vaporise
3. Pure metal vaporises and is condensed
4. Impurities are left behind
Poling
Oxide impurity of impure metals can be purified by this method. Poles of green wood are
used to stir the molten crude metal sample. The hydrocarbon organic matter in the poles
acts as a reducing agent and reduces the oxide impurities. This method is used for refining
copper.
2Cu2O + CH4 → 8Cu + CO2 + 2H2O
Electrolytic method
A large number of metals e.g., copper, silver, gold, nickel etc. are refined by this method.
In an electrolytic cell the impure metal is made anode and a thin strip of pure metal is
made cathode. A solution of a suitable salt of the concerned metal is used to fill the
electrolytic cell. On passing electricity, the anode undergoes dissolution while the pure

7. metal gets deposited at cathode. Insoluble impurities fall below the anode in the form of
anode mud.
Fig: - Electrolytic purification of a metal