Extraction of metals

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Extraction of metals
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Principles of Metal extraction

• Most elements do not occur as separate substances
  but exist naturally as compounds.
• Metals tend to exist as metal oxides as part of
  ores which are excavated from the earth.
• To recover the metal from its oxide the metal
  ion is split from the oxygen ion.
• Metals high up on the activity series have more
  stable oxides than those lower down and due to
  this are more difficult to split up than those
  lower down.

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Methods of metal extraction

• 1.Electrolyis
• 2. Reduction with carbon(carbon monoxide)
• 3. Heating of the ore.

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Methods of metal extraction

• 1. Electrolysis this entails the immersing of a
  positively and negatively charged electrical
  poles to a molten or aqueous solution of a
  substance. The passage of the current causes
  positively charged ions to be attracted to the
  negative pole and negatively charged ions to be
  attracted to the positively charged pole. While
  at the Negative pole, positively charged ions
  gain electrons to become neutral atoms and are
  deposited on the negative pole or fall to the
  bottom as a precipitate. The same occurs to
  positively charged ionsat the negative pole. The
  overall effect is that the constituents of the
  substance are separated and usually are deposited
  on the Positive Pole or Anode and the Negative
  pole or Cathode or it may sink to the bottom of
  the container as a precipitate

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Methods of metal extraction
14kilowat hours 1kg of Aluminium

• 1.Electrolyis
• Most powerful means of extraction.
• most expensive.
• Can only be used where electricity is abundant.
• 2. Reduction with carbon(carbon monoxide)
• Cheaper to operate than electrolysis.
• Labor intensive .
• Expensive to startup as large industrial
  equipment is used.
• 3. Heating of the ore.
• Cheap
• Can only be used on the most unreactive of
  metals(Mercury,gold,silver,etc.)

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Extraction of Aluminium
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Extraction of Iron

• The extraction of Iron is a reductive process
  whereby oxygen is removed from the iron oxide by
  carbon monoxide. The process occurs within a
  Steel blast furnace lined with refractive(fire)
  bricks at temperatures from 800C upto 1900C. The
  Chamber is kept hot by jets of hot air at over
  800C, giving it the name Blast furnace.

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• Start materials
• Iron Ore or Hematite
• Lime or Calcium carbonate CaCO3
• Coke a carbonaceous ashy substance

Lime
Iron Ore
Coke
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Extraction of Iron Step1 Burning of Lime

• Iron ore, limestone(CaCO3) and coke are delivered
  to the top of the blast furnace, where the
  temperature is around 800C.
• The lime stone burns at 800C yielding calcium
  oxide(CaO) and Carbon Dioxide(CO2).
• CaCO3 -gt CaO CO2
• The Calcium oxide causes impurities which are
  present with the ore to fall as a precipitate
  near to the bottom producing a layer of slag.

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Extraction of Iron Step 2 Production of Carbon
Monoxide

• The carbon Dioxide yielded from the Burning of
  Lime passes over the coke. Coke is a coal like
  substance produced from the heating of Tar and
  Petrochemicals without heat and contains a high
  percentage of carbon. The Carbon atoms of coke
  remove a single oxygen from each molecule of CO2
  producing carbon monoxide
• CO2 C 2 CO

Coke
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Extraction of Iron Step 3 Reduction of Iron

• The Carbon monoxide yielded from the reaction of
  Carbon dioxide and lime removes the oxygen from
  Iron oxide.
• Each Carbon monoxide molecule is capable of
  binding a single oxygen so 3 are used to
  completely remove all oxygen from the iron oxide.
• Fe2O3 3 CO -gt 2Fe(s) 3 CO2
• The molten iron sinks to the bottom lowest level
  of the furnace, where it can be tapped off.
• The iron produced by this process is called pig
  iron and is 95 pure.

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Extraction of Iron overview

• Production of iron from its ore uses Carbon
  monoxide to reduce Iron oxide to iron atoms.
• 1.Lime burns
• CaCO3 -gt CaO CO2
• 2. CO2 reduced by coke to CO
• CO2 C -gt 2 CO
• 3. Iron oxide reduced by CO
• Fe2O3 3CO -gt 2Fe 3CO2

Removes impuritiies slag production
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Q A

• What is Limestone made of?
• How are impurities from the ore removed?
• What is the layer of precipitated impurities
  called?
• Where does the carbon dioxide produced during the
  process come from?
• What is the function of Coke during the process?
• What substance is responsible fo reducing the
  iron oxide to iron?
• What is the level of purity of the iron produced
  by this process?