In the context of the topic ‘Sources of materials and their
Extractions’, before starting with the actual description we
must clarify the definition of ‘Materials’.
We would like to converge the boundary of word ‘Materials’ to
We are going to discuss metals only because out of three vast
categories of Engineering Materials:
The only materials that can be extracted are the ‘Metals’.
3. Converging the ‘Materials’ furthermore from category of
‘Metals’, to make the topic more precise we will be discussing
the Sources and Extractions of the following metals:
6. GENERAL TERMINOLOGY RELATED TO METALS
A solid element or compound which occurs naturally in the
Earth's crust is called a mineral.
A mineral from which metals can be extracted profitably is
called a metal ore. Profitable extraction means that the cost of
getting the metal out of the ore is sufficiently less than the
amount of money made by selling the metal. So All Ores Are
Minerals But All Minerals Are Not Ores.
The most common metal ores are oxides and sulphides. Metals
are obtained from their ores by reduction.
7. Metals seldom occur in nature in their pure form
commonly found as ores (ionic compounds of the metal
+ a non-metal)
• Native Metals:
Gold and platinum occur in the Earth as native metal,
which means that they are found as the element, not
the compound, and so do not need to be reduced. Silver
and copper may also be found as native metal. These
metals occur in nature in their pure form.
Metals are often extracted from the Earth by means of mining.
Ore is located by prospecting techniques, followed by the
exploration and examination of deposits.
Mineral sources are generally divided into surface mines,
which are mined by excavation using heavy equipment,
and subsurface mines.
Once the ore is mined, the metals must be extracted, usually
by chemical or electrolytic reduction. The methods used
depend on the metal and their contaminants.
12. RECYCLING RESOURCES
Demand for metals is closely linked to economic growth.
During the 20th century, the variety of metals uses in society
grew rapidly. Today, the development of major nations, such as
China and India, and advances in technologies, are fuelling
ever more demand.
More and more of the world's metal stocks are above ground
in use, rather than below ground as unused reserves. An
example is the in-use stock of copper. Between 1932 and 1999,
copper in use in the USA rose from 73g to 238g per person.
13. Metal ore deposits are a finite resource (there are only a
certain amount of them) and non-renewable (once used, they
are gone and will not be replaced). Many metals are obtained
today from recycling (melting and refining) scrap metals.
Metals are inherently recyclable, so in principle, can be used
over and over again, minimizing these negative environmental
impacts and saving energy at the same time.
Metal stocks in society can serve as huge mines above
The World Bank reports that China was the top importer
of ores and metals in 2005 followed by the United States and
METAL AND ORE IMPORTS IN 2005
17. • The method used to extract metals from the ore in which they
are found depends on their reactivity. For example, reactive
metals such as aluminum are extracted by electrolysis, while a
less-reactive metal such as iron may be extracted by
reduction with carbon or carbon monoxide.
19. Ways Of Extraction
electrolysis of molten
electrolysis of molten
Al2O3 dissolved in
reduction of oxides
Roasting ore by
22. • Iron is very reactive and is found in nature in form of its oxides,
carbonates and sulphates.
• The main iron ore is Haematite (iron (III) oxide - Fe2O3).
23. The raw materials for extracting iron and their function in the process
Raw material Contains Function
iron ore (hematite) iron oxide a compound that contains iron
coke carbon burns in air to produce heat,
and reacts to form carbon
monoxide (needed to reduce the
limestone calcium carbonate helps to remove acidic
impurities from the iron by
reacting with them to form
air oxygen allows the coke to burn, and so
produces heat and carbon
24. Step1: Concentration
The ore is crushed in crushers and is broken to small pieces. It is concentrated with
gravity separation process in which it is washed with water to remove clay, sand, etc.
The ore is then heated in absence of air (calcined). This results in decomposition of
carbonates into oxides and then ferrous oxide is converted into Ferric Oxide.
2 2 3
The concentrated ore is mixed with calculated quantity of coke, limestone and the
mixture is put in the Blast Furnace from top.
25. BLAST FURNACE
•It is a tall cylindrical furnace
made of steel.
• It is lined inside with fire bricks.
• It is narrow at the top and has
an arrangement for the
introduction of ore and outlet for
• Heated with help of Hot Gases.
26. Chemical Reactions that take place in a Blast Furnace
1. Formation of Carbon Monoxide:
C O CO
2. Reduction of Haematite to Iron:
2 3 2 Fe O 3CO2Fe 3CO
3. Functions of limestone:
CaCO heat CaO
28. • The current method for extracting aluminum is expensive because
it involves several stages and uses large amounts of costly electrical
• Aluminum is very abundant in the Earth's crust but it is always
found as very stable compounds .
• Bauxite has the highest concentration of aluminum in these
sources and is mined extensively around the world.
29. Raw materials for the electrolysis process:
• Bauxite ore of impure aluminum oxide [Al2O3 made up of
Al3+ and O2– ions]
• Carbon (graphite) for the electrodes.
• Cryolite reduces the melting point of the ore and saves
energy, because the ions must be free to move to carry the
current and less energy is needed to melt the aluminum oxide
obtained from the bauxite ore.
•When p.d is applied,
Al3+ is attracted to the negative
O2- is attracted to the positive anode
•At the cathode,
Al3+ gains 3 electrons from the
cathode to form molten aluminum,
which is tapped off
Al3+(l) + 3e- Al (l)
•At the anode,
O2- loses 2 electrons to the anode to
2O2-(l) O2(g) + 4e-
Oxygen released attacks carbon
anode, to form Carbon
monoxide/dioxide. Carbon anode
dissolved. Needs to be replaced
•Aluminum when exposed in air forms a thin protective coat of
•For better protection, a thicker coat is made
•Through the process: Anodising
•Make aluminum the anode in sulphuric acid bath
•Oxygen produced at the anode then combines with aluminum
to form a protective porous layer aluminum oxide 1000 times
thicker, compared when exposed to air
•Pores can be sealed by dipping into hot water or colored by
using dyes which can be absorbed into it.
33. • Copper is extracted usually from the sulphide ore chalcopyrite
(CuFeS2) by smelting process.
•Ores containing 4% or more copper are treated by smelting
34. There are following steps for the Hydrometallurgical extraction of copper from Chalcopyrite:
Crushed ore is suspended in water containing pine oil. The pine oil binds to the copper
compounds, but not to the unwanted rocky material. A blast of air is passed through the
suspension. The particles of ore get wetted by oil and floats as a froth which is
skimmed. The gangue sinks to the bottom.
35. 2. ROASTING
The concentrated ore is roasted in the furnace in the presence of oxygen. Sulfur is oxidized to
SO2 and impurities of arsenic and antimony are removed as volatile oxides. The following
reactions take place:
2CuFeS2 + O2
Cu2S + 2FeS + SO2
S + O2
4As + 3O2
4Sb + 3O2
Cu2S + O2
Cu2O + SO2
FeS + O2
FeO + SO2
The roasted ore is mixed with coke and silica sand (SiO2) and is introduced into a blast furnace.
The hot air is blasted and FeO is converted into ferrous silicate (FeSiO3)
FeO + SiO2
Cu2O + FeS Cu2S + FeO
FeSiO3 (slag) floats over the molten matte of copper.
The resulting product of smelting is the combination of copper sulfate and iron sulfide called
matte (Copper matte).
36. 4. BESSEMERIZATION
Copper metal is extracted from molten matte through bessemerization . The matte is introduced
in to Bessemer converter which uphold by tuyeres. The air is blown through the molten matte.
Blast of air converts Cu2S partly into Cu2O which reacts with remaining Cu2S to give molten
2Cu2S + 3O2
2Cu2O + 2SO2
2Cu2O + Cu2S 6Cu + SO2
The product of Bessemerization is called as “Blister
Copper” because, as it solidifies, SO2 hidden in it
escapes out producing blister on its surface.
37. 5. REFINING OF BLISTER COPPER
• Blister copper is refined by electrolysis.
• The copper is cast into copper anodes and placed in an electrolytic cell. Once charged, the
pure copper collects on the cathode and is removed as 99% pure.
• Blocks of blister copper are used as anodes and thin sheets of pure copper act as cathodes.
The cathode plates are coated with graphite in order to remove depositing copper.
• The electrolyte is copper sulfate (CuSO4) mixed with a little amount of H2SO4 to increase
the electrical conductivity.
• Optimum potential difference is 1.3 volt for this electrolytic process.
Fe(s) → Fe2+(aq) + 2e–
Zn(s) → Zn2+(aq) + 2e–
38. EXTRACTION OF PRECIOUS METALS FROM ANODE SLUDGE
Impurities, such as Ag, Au, and Pt, are less easily oxidized than Cu. These remain in metallic
form and fall to the bottom of the cell, forming “anode sludge” from which they can later
be recovered. The anode sludge from copper-refining cells provide one fourth of U.S. silver
production and about one eighth of U.S. gold production.
42. From the above report we learned about the importance of Metallic Materials. We
selected 3 extensively used metallic elements that are iron, aluminum and copper,
took notice of their existence and sources, their ores and the extraction processes the
ores must go through so that we may attain pure metals to be used for Engineering
purposes in industries.