Metallurgy
The extraction of metals from
their ores and the production of
pure metals and alloys
Production of metals
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Mining
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Most metals are found as ions in ionic compounds
mixed with other components like rock (called the
ore)
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Gold, Platinum, Silver and sometimes Copper are
found as elements (pure atomic form)
Metallurgy- process of extracting and
processing the metal from the ore
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Concentration- uses various physical and chemical
processes
Metal extraction- uses various physical and chemical
processes
Example of Ores
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Malachite
Formula Cu2CO3(OH)2
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Bauxite: bauxite can include:
gibbsite Al(OH)3, boehmite AlO(OH) and
diaspore, AlO(OH).
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Hematite
Fe2O3
Mining
Five main types of mining:
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Open cast mining
Underground mining
Open pit mining
Dredging
Solution mining
Open cast mining
Underground mining
Open pit mining
Dredging
Solution mining
Ore concentration
Also called ore dressing, the aim is to increase
the amount of metal in each tonne of ore. The
ore is crushed then ground and concentrated,
the following methods may be used:
 Gravity concentration
 Flotation
 Magnetic separation
Gravity concentration
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Some ores are heavier than the waste. The
ore is shaken by a jolting box, or similar,
while wet.
Particles will separate into layers depending
on weight, the metal may be removed as a
layer.
Gold panning is an example of gravity
concentration
Flotation
The fine particles of ore are swirled around in large
tanks with air blown in and flotation agents added. The
particles attach to the bubbles and float to the surface
where the froth is skimmed off. Copper and lead are
separated this way.
Magnetic seperation
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In the seperation of ores that
have magnetic properties, the
ore is ground and passed
over a rotating drum.
The drum has a magnet
inside it which holds the
magnetic ore particles as the
waste falls outside the screen.
The ore held on the drum can
be released or scraped off.
Iron is separated this way.
Magnetic separation
http://www.youtube.com/watch?v=XZjPr8WZtas
Metal extraction- the ionic compound that
has a metal ion needs have a chemical
process to change the metal ion into a
metal atom (like a single displacement rxn)
The process of extracting metals from
concentrates:
 Smelting – furnace heat is used with a
reducing agent (iron uses coke, mostly
carbon) and strong continual air flow to
produce metal and slag waste.
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Many times these are synthesis, decomposition
and single displacement reactions
Steps involved in purifying iron using
a blast furnace- Smelting
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Oxygen in the air reacts with coke (C solid) to give carbon dioxide:
synthesis
The limestone breaks down to form carbon dioxide: (decomposition)
Carbon dioxide produced in 1 + 2 react with more coke to produce carbon
monoxide: (synthesis)
The carbon monoxide reduces the iron in the ore to give molten iron: (single
displacement)
The limestone from 2, reacts with the sand to form slag (calcium silicate):
(synthesis)
Both the slag and iron are drained from the bottom of the furnace. (iron is at
the very bottom then slag above it…due to density of each)
The slag is mainly used to build roads.
The iron whilst molten is poured into moulds and left to solidify - this is
called cast iron and is used to make railings and storage tanks.
About 90% pure
The rest of the iron is used to make steel. (Higher purity needed)
Blast furnace
Further refining may be necessary for
the mineral
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Electrolysis
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Electricity is used to purify the metal from the mineral
Two different metals are plunged in an aqueous solution of
the ionic compound (example CuSO4 (aq))
The ion acquires the necessary electrons from the electricity
to change back to the atom. (Cu+2 + 2 e- → Cu (s))
The metal atom accumulates on one of the metals immersed
in the solution…99% pure
This process is scaled up industrially to produce sheets of
copper
Canadian Mint recognized all over the world for its 4 nine
gold….99.9999% gold
After refining…it is now the metal at high conc. (90+%)
Common Alloys
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The new purified metals are sometimes remixed in
specific percent ratios to make alloys…these are
mixtures and not compounds
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Stainless steel is mostly iron with about 10% chromium
Bronze= mostly copper and some tin
Brass= mostly copper and some zinc
Pewter=mostly tin and some copper
White gold= 90%gold, 10% nickel
Steel= iron and 2% carbon
Impact on the environment
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+ (jobs, metals)
- disruption of the land from the mining
process itself…like dust and rubble as a
result of surface mining are released into the
atmosphere
- accidental release of dangerous chemicals
like cyanide (used to purify gold)
- release of acidic oxides from the smelting
process (Sudbury example…new
technologies addressing this issue)
Impact
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- accidents to trap miners
- mine tailings are acidic…caused by newly
exposed rock and iron pyrite (FeS, fool’s
gold) reacting with oxygen and water and can
sometimes be accidentally released in the
ground water and harm aquatic ecosystems
- Tailings in tar sands have thunderous shot
gun sounds every minute to dissuade ducks
from landing on the acidic ponds
Alberta Tar Sands
Alberta Tar Sands
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https://www.youtube.com/watch?v=61X4IQqn
md0&feature=player_detailpage
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https://www.youtube.com/watch?feature=play
er_detailpage&v=Sjia7BsP4Bw