4. Minerals:The combined state of metal in the
earth’s crust.
Ex: Oxides ,Carbonates.
• Ore: The Mineral from which the metal
economically and commercially extracted.
• Ex: Al- Bauxite,Fe-Haematite.
• Gangue: Impurities present in minerals.
• Ex: silicates,rock pieces………..
All ores are minerals ,but all minerals are not
ores.
5. Metallurgy
It is process of extraction of metal from its ores
1. Concentration of the Ore
2. Production of Crude metal
3. Refining of the Crude metal
4. Crushing & Pulverisation
7. 2.Concentration of the Ore
Removal of impurities from the pulverised ore
• A) Gravity Separation(hydraulic washing)
• B) Froth floation
• C) Magnetic Seperation
• D) Leaching
12. D)Leaching is the process in which the
ore is concentrated by chemical
reaction with a suitable reagent
Eg: Leaching of alumina from bauxite ore
13. 3.Production of Crude metal
• 1. Conversion to oxide.
• 2. Reduction of the oxides to metal.
Calcination-heat
• Conversion to oxide ( absence of air)
Roasting-heat
(Excess of air)
14. . Reduction of the oxides to metal
• (i) Smelting (reduction with carbon)
• Flux: During smelting a substance. called flux is
added which removes the non-fusible impurities
as fusible slag. [Flux + Gangue = Slag]
• Acidic flux For basic impurities, acidic flux is
added.
• e.g., CaO + SiO2 → CaSiO3
15. Refining of the Crude metal:
The process of removing impurities from the crude
metal
(i) Liquation :This method is used for
refining the metals having low melting
points (such as Sn. Pb, Hg, Bi) than the
impurities,
→ The impure metal is placed on the sloping
hearth and is gently heated.
→ The metal melts and flows down leaving
16. ii) Distillation:
This is useful for low boiling metals such
as Zn, Hg. The impure liquid metal is
evaporated to obtain the pure metal as
distillate.
iii)Electro-refining :
In this method, impure metal forms the
anode while the cathode is a rod or sheet of
pure metal.The electrolytic solution consists
of a soluble salt of the metal.
17. • (iii) Zone-refining :
• Difference in solubilities of impurities in molten
and solid state of metal.
• Semiconductors like silicon, germanium,
gallium are purified by this method.
• Elements of very high purity are obtained by
this method.
18. Vapour phase refining
• * Van Arkel Method for Refining Zirconium
or Titanium
• * Mond’s process for Refining Nickel
26. Different irons:
• The iron obtained from blast furnace is called pig
iron. It contains about 4% C and smaller
amounts of impurities (e.g. S, P, Si, Mn etc.)
• When pig iron is melted with scrap iron and coke
in presence of hot air blast, cast iron is formed.It
is extremely hard and brittle.
• Wrought iron or malleable iron is the purest
form of commercial iron. It is prepared from
cast iron.
27. Extraction of zinc from zinc oxide
(ZnO)
• The ores of Zn are zincite (ZnO), Zinc blende
(ZnS), calamine (ZnCO3) etc. Zn is mainly
extracted from ZnO.
• The reduction of zinc oxide is done using
coke.
ZnO + C(coke) 673 K Zn + CO
28. Thermodynamic Principles of Metallurgy
• ΔG = ΔH – TΔS
• ΔH is the enthalpy change ,ΔS is the entropy change.
• The reaction will proceed only when the value of ΔG
is negative in the above equation.
• This can be possible in the following ways:
• 1. If ΔS is positive, on increasing the temperature
(T), the value of TΔS would increase (i.e. TΔS > ΔH )
and then ΔG will become –ve.
• 2. If two reactions having different ΔG values are
coupled, the net ΔG of the reactions becomes –ve
29. Ellingham Diagram
• The graphical representation of Gibbs energy vs
Temperature was first given by H.J.T.Ellingham and
these graphs are known as Ellingham Diagram.
• It gives a sound basis for considering the
choice of reducing agent in the reduction of
oxides.
• These diagrams help us in predicting the
feasibility of thermal reduction of an ore.
(The criterion of feasibility is that at a given
temperature, Gibbs energy of the reaction
must be negative.)
