It is a chemistry related presentation on metallurgy process and their extraction procedure with diagrams. it will be useful to all school students and under graduate level students

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2. METALLURGY AND BASIC
EXTRACTION TECHNIQUES
BY
SAKTHIBALAJI C S
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3. WHAT IS METALLURGY?
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• Metallurgy relate to the science and
technology of metals.
The branch of science and technology
concerned with the properties of metals and
their production and purification.
• Metallurgy comprises of 3 steps:
i. Concentration of Ore
ii. Isolation of metal from the concentrated Ore
iii. Purification of the metal

4. BASIC TERMINOLOGIES
• Mineral: A naturally occurring substance obtained by
mining which contains the metal in free
state or in the form of compounds like oxides, sulphides
etc... is called a mineral
• Ore: Minerals that contains a high percentage of metal,
from which it can be extracted conveniently
andeconomically are called ores
• Flux: a chemical substance that forms an easily fusible slag
with gangue.
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5. BASIC TERMINOLOGIES (contd…)
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• Slag: Waste matter separated from metals during the
extraction of ores.
• Gangue: In mining, gangue is the commercially
worthless material that surrounds, or is closely mixed
with, a wanted mineral in an ore deposit.
• The separation of mineral from gangue is known as
mineral processing.

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7. EXTRACTIVE TECHNIQUES
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• It is the process of removing impurities or
undesired materials from the ore leaving behind
the required metal.
• Different process followed are
i. Hydraulic washing OR Gravity seperation
ii. Magnetic separation
iii. Froth floatation
iv. Leaching

8. GRAVITY SEPERATION
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9. FROTH FLOATATION
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10. MAGNETIC SEPERATION
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11. LEACHING
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• It involves the use of aqueous solutions to
extract metal from metal bearing materials
which is brought into contact with a material
containing a valuable metal. aqueousThe
vary in termssolution conditions
oxidation-reduction
of pH,
potential, presence of
chelating agents and temperature.

12. TYPES OF LEACHING
 CYANIDE LEACHING
4Au(s)+8CN-(aq)+O2(g)+2H2O(l)4[Au(CN)2]-(aq)+4OH-(aq)
Zn (s) + 2Au(CN)2]- (aq) [Zn(CN)4]2-(aq) + 2Au (s)
 AMMONIA LEACHING
Ammonia selectively leaches these metals by forming
their soluble complexes viz. [Ni(NH3)6]2+, [Cu(NH3)4]2+, and
[Co(NH3)5H2O]3+
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13. TYPES OF LEACHING( conti…)
 ALKALI LEACHING
 Al2O3(s)+2NaOH(aq)+3H2O(l)2Na[Al(OH)4](aq)
 2Na[Al(OH)4](aq)+CO2(g)Al2O3.xH2O(s)+2NaHCO3(aq)
 ACID LEACHING
 2ZnS(s) +2H2SO4(aq)+O2(g)  2ZnSO4 (aq)+2S(s) + H2O(l)
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14. METALS AND ITS EXTRACTING
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TECHNIQUES
Metals - in decreasing order of
reactivity
Reactivity
Potassium
Sodium
Calcium
Magnesium
Aluminium
extract by electrolysis
Carbon
Zinc
Iron
Tin
Lead
extract by reaction
with carbon or carbon monoxide
Hydrogen
Copper
Silver
Gold
Platinum
extracted by various chemical reactions

15. CLASSIFICATION
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Metallurgy
categories:
• Roasting
• Calcination
• Smelting
• Refining
is classified into following

16. ROASTING
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• The processing of strong heating of the ore in
presence of excess amount of air below its melting
point.
• Purpose of roasting:
i.
ii.
To convert the sulphide into oxide and sulphate
To remove impurities like S, As, Sb.
iii. To remove moisture
iv. To Oxidise easily oxidisable substances

17. ROASTING
• It is mainly used for sulphide ores
• it converts the sulphides into oxides
• 2ZnS+3O2  2ZnO+SO2
• 2Cu2S + 3O2  2Cu2O + 2SO2
• Roasting also removes impurities such as As,S,P by converting
them into their volatile oxides.
4As + 3O2  2As2O3
• S8 + 8O2  8SO2
P4 + 5O2 P4O10
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18. CALCINATION
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• Calcination is heating to high
temperatures in the absence of
air or oxygen.
• The main purpose of calcination
of ores are to convert carbonates
and hydroxides ores into oxides.
• ZnCO3 → ZnO + CO2
• CaCO3 → CaO + CO2
• Al2O3.3H2O Al2O3 + 3H2O

19. i. Remove the volatile impurities
ii. To remove moisture
iii. Make the mass porous
Purpose of calcination
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20. CALCINATIONVS
ROASTING
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CALCINATION ROASTING
It is the process of heating in absence
of air
It is the process of heating in presence
of air to oxidise the impurities
It is employed for carbonate ores It is employed for sulphide ores
Calcination produces carbon dioxide
along with metal oxide
Roasting produces sulphur dioxide
along with metal oxide

21. SIMILARITIES
•Both are processes of heating the ore
below its melting point.
•Both aim at removal of impurities in the
ore.
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22. SMELTING
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• Smelting is a form of extractive metallurgy; its
main use is to produce a base metal from its ore.
• Smelting makes use of heat and a chemical
reducing agent to decompose the ore, driving off
other elements as gases or slag and leaving only
the metal base behind.
• The reducing agent is commonly a source of
carbon such as coke, or in earlier times charcoal.

23. PROCESS
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• 2𝐶 + 𝑂2 → 2𝐶𝑂(Burning of fuel to CO)
• 𝐹𝑒2 𝑂3+ 3𝐶𝑂→ 2𝐹𝑒+ 3𝐶𝑂2( CO reduces
hematite to iron)
• 𝐶𝑎𝐶𝑜3 → 𝐶𝑎𝑂+ 𝐶𝑂2 (Decomposition)
• 𝐶𝑎𝑂+ 𝑆𝑖 𝑂2 → 𝐶 𝑎𝑆𝑖 𝑂3(Impuritiesareremoved)

24. REDUCTION OF METALS
• AUTO REDUCTION
• CARBON REDUCTION
• METAL REDUCTION
• REDUCTION BY HYDROGEN
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25. REDUCTION BY METALS
• Metallic oxides such as Cr2O3 can be reduced by an
aluminothermite process. In this process, the metal
oxide is mixed with aluminium powder and placed in
a fire clay crucible. An ignition mixture (usually
magneisium and barium peroxide)
is used.
• Cr2O3 + 2Al  2Cr + Al2O3
• B2O3 + 6Na  2B + 3Na2O
• Rb2O3 + 3Mg  2Rb + 3MgO
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26. REDUCTION BY HYDROGEN
• This method can be applied to the oxides of the
metals (Fe, Pb, Cu) having less electropositive
character than hydrogen.
•
Ag2O (s)+ H2 (g)  2Ag (s) + H2O (l)
• 2NiO(s)+CO(g) + H2(g) 2Ni (s)+CO2(g)+H2O (l)
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27. AUTO REDUCTION
• Simple roasting of some of the ores give the
crude metal. In such cases, the use of
reducing agents is not necessary. For example,
mercury is obtained by roasting of its ore
cinnabar (HgS)
• HgS (s) + O2 (g)  Hg (l) + SO2(g)
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28. METAL RECOVERY BY PURIFICATION
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• Sometimes, however, further refining is required
if ultra-high purity metals are to be produced.
• The primary types of metal recovery processes
are
• i) electrolysis
• ii) gas phase reduction.
• iii) zone refining

29. Thermodynamics of metallurgy
 Harold Ellingham used the
above relationship to
calculate the ΔG⁰ values at
various temperatures for
the reduction of metal
oxides by treating the
reduction as an equilibrium
process.
 ΔG= Δ H-T Δ S
 ΔG= -RT ln Kp
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31. OBSERVATIONS
 For most of the metal oxide formation, the slope is
positive
 The graph for the formation of carbon monoxide is a
straight line with negative slope. It indicates that CO is
more stable at higher temperature
 As the temperature increases, generally ΔG value for
the formation of the metal oxide become less
negative and becomes zero at a particular
temperature.
 Below this temperature, ΔG is negative and the oxide
is stable and above this temperature ΔG is positive
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32. Applications
 Ellingham diagram for the formation of Ag2O and HgO is at
upper part of the diagram -decompose on heating even in
the absence of a reducing agent.
 Any metal can reduce the oxides of other metals that are
located above it in the diagram.
 Formation of chromium oxide lies above that of the
aluminium, meaning that Al2O3 is more stable
than Cr2O3
 The carbon line cuts across the lines of many metal oxides
and hence it can reduce all those metal oxides at sufficiently
high temperature.
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33. LIMITATIONS
 1. It gives information about the thermodynamic
feasibility of a reaction. It does not tell anything
about the rate of the reaction.
 2. The interpretation of ΔG is based on the
assumption that the reactants are in equilibrium
with the product which is not always true.
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34. EXTRACTION OF ALUMINIUM -
HALL-HEROLD PROCESS
• carbon attached with tank - cathode.
• The carbon blocks immersed in the electrolyte –
anode
• 10% CaCl2 helps to lower the M.P of the mixture
• 4Al3+ (melt) + 6O2- (melt)+ 3C(s) 4Al(l) + 3CO2(g)
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35. REFINING PROCESS OF METALS
• Distillation
low boiling volatile metals like zinc
(boiling point 1180 K) and mercury (630 K)
•
• Liquation
The crude metal is heated to form fusible
liquid and allowed to flow on a sloping surface
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36. ELECTROLYTIC REFINING
• Anode - impure metal (silver)
• 2Ag(s)  2Ag+ (aq)+ 2e-
• Cathode - pure metal (silver)
• 1Ag+ (aq)+ 1e-  Ag (s)
• Electrolyte - Acidified salt solution of metal ( AgNO3)
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38. ZONE REFINING
• ELEMENTS SUCH AS GERMANIUM (GE), SILICON (SI) AND
GALIUM (GA) THAT ARE USED AS SEMICONDUCTOR ARE
REFINED USING THIS PROCESS.
• METAL IS TAKEN IN THE FORM OF A ROD. ONE END OF
THE ROD IS HEATED USING A MOBILE INDUCTION HEATER
WHICH RESULTS IN MELTING OF THE METAL ON THAT
PORTION OF THE ROD.
• WHEN THE HEATER IS SLOWLY MOVED TO THE OTHER END
THE PURE METAL CRYSTALLISES WHILE THE IMPURITIES
WILL MOVE ON TO THE ADJACENT MOLTEN ZONE FORMED
DUE TO THE MOVEMENT OF THE HEATER.
• AS THE HEATER MOVES FURTHER AWAY, THE MOLTEN
ZONE CONTAINING IMPURITIES ALSO MOVES ALONG WITH
IT
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40. VAPOUR PHASE METHOD
•MOND PROCESS - NICKEL:
IMPURE NICKEL WITH CO AT 350 K TO GIVE NICKEL
TETRACARBONYL. THE SOLID IMPURITIES ARE LEFT BEHIND.
NI (S) + 4 CO (G)  NI(CO)4 (G)
• NICKEL TETRACARBONYL AROUND 460 K, THE COMPLEX
DECOMPOSES TO GIVE PURE METAL.
NI(CO)4 (G) NI (S) + 4 CO (G)
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41. VAN-ARKEL METHOD - ZR/TI
• THE IMPURE TITANIUM METAL WITH IODINE AT 550 K TO
FORM VOLATILE TITANIUM TETRA-IODIDE.(TII4)
• TI (S) + 2I2 (S)  TII4 (G)
• TITANIUM TETRAIODIDE IS PASSED OVER A TUNGSTEN
FILAMENT AT 1800 K GIVES PURE TITANIUM WHICH IS
DEPOSITED ON THE FILAMENT
• TII4 (G)  TI (S) + 2I2 (S)
• THE IODINE IS REUSED
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Thank
you