<ul><li>Metals are usually found in ores containing minerals </li></ul><ul><li>They are combined with oxygen or sulfur to ...
<ul><li>When roasting sulfide ores, sulfur dioxide is produced as a waste product </li></ul><ul><li>This is a contributor ...
<ul><li>To obtain the metal its ore, a reducing agent is used to remove the oxygen, in a reduction reaction. </li></ul><ul...
<ul><li>For the extraction of iron, manganese and copper the reducing agents are carbon and carbon monoxide. </li></ul><ul...
<ul><li>Manganese is produced by the reduction of its oxide with carbon.  </li></ul><ul><li>2MnO (s)  + C (s)   2Mn (l)  +...
<ul><li>Some metals can’t be extracted using carbon reduction, such as aluminium, titanium and tungsten. </li></ul><ul><li...
<ul><li>Aluminium is extracted from purified bauxite ore (mainly Al 2 O 3 ) </li></ul><ul><li>The oxide is dissolved in mo...
<ul><li>Aluminium is produced at negative electrode </li></ul><ul><li>2Al 3+  +6e -   2Al </li></ul><ul><li>Oxygen is prod...
<ul><li>As titanium can’t be reduced with carbon, it is reduced by sodium or magnesium </li></ul><ul><li>This is an expens...
<ul><li>Tungsten is extracted from its oxide, WO 3,  by reduction with hydrogen at high temperatures </li></ul><ul><li>WO ...
<ul><li>Recycling scrap metals has many environmental and economic advantages </li></ul><ul><li>It reduces the amount of s...
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Metal extraction

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Metal extraction

  1. 2. <ul><li>Metals are usually found in ores containing minerals </li></ul><ul><li>They are combined with oxygen or sulfur to form oxides or sulfides </li></ul><ul><li>Sulfide ores are converted to oxides by heating them in the air, which is called ‘ roasting ’, e.g. zinc sulfide to zinc oxide </li></ul><ul><li>ZnS (s) + 1½O 2(g) ZnO (s) + SO 2(g) </li></ul>zinc sulfide oxygen zinc oxide sulfur dioxide
  2. 3. <ul><li>When roasting sulfide ores, sulfur dioxide is produced as a waste product </li></ul><ul><li>This is a contributor to acid rain if it is allowed to escape into the atmosphere as it reacts in the air to form sulfuric acid </li></ul><ul><li>However it can be converted to sulfuric acid in controlled conditions which can then be sold for a variety of purposes </li></ul><ul><li>SO 2(g) + H 2 O (g) + ½O 2(g) H 2 SO 4(l) </li></ul>sulfur dioxide oxygen water sulfuric acid
  3. 4. <ul><li>To obtain the metal its ore, a reducing agent is used to remove the oxygen, in a reduction reaction. </li></ul><ul><li>Examples of some reducing agents; </li></ul><ul><li>Coke (an impure form of carbon) </li></ul><ul><li>Hydrogen (made from methane and water) </li></ul><ul><li>A more reactive metal may be used. </li></ul><ul><li>Electrolysis can also be used for more reactive metals. </li></ul>
  4. 5. <ul><li>For the extraction of iron, manganese and copper the reducing agents are carbon and carbon monoxide. </li></ul><ul><li>These are cheap because coke can be used which is cheaply produced by heating coal in the absence of air. </li></ul><ul><li>The extraction of iron is done in a blast furnace which reaches temperatures of 2000K. </li></ul><ul><li>Fe 2 O 3(s) + 3CO (g) 2Fe (l) + 3CO 2(g) </li></ul>Haematite Carbon Monoxide Iron Carbon Dioxide
  5. 6. <ul><li>Manganese is produced by the reduction of its oxide with carbon. </li></ul><ul><li>2MnO (s) + C (s) 2Mn (l) + CO 2(g) </li></ul><ul><li>Copper used to be produced this way but nowadays some ores are converted in to solutions containing Cu 2+ ions. The copper is extracted by reducing with scrap iron. </li></ul><ul><li>Cu 2+ (aq) + Fe (s) Cu (s) + Fe 2+ (aq) </li></ul><ul><li>This is ‘greener’ as no CO 2 is produced and scrap iron is cheap and readily available. </li></ul><ul><li>Also, the solution can be made from low grade ore so it is readily available </li></ul>
  6. 7. <ul><li>Some metals can’t be extracted using carbon reduction, such as aluminium, titanium and tungsten. </li></ul><ul><li>Aluminium can’t because it is more reactive than carbon. </li></ul><ul><li>Titanium and tungsten can’t because it would form a metal carbide which would make the metal brittle. </li></ul>
  7. 8. <ul><li>Aluminium is extracted from purified bauxite ore (mainly Al 2 O 3 ) </li></ul><ul><li>The oxide is dissolved in molten cryolite, which forms a solution which melts at around 1240K (Al 2 O 3 melts at 2435K therefore less energy is required </li></ul><ul><li>The solution is electrolysed so the main cost of the process is electricity which makes economic sense where cheap electricity is available </li></ul>
  8. 9. <ul><li>Aluminium is produced at negative electrode </li></ul><ul><li>2Al 3+ +6e - 2Al </li></ul><ul><li>Oxygen is produced at the positive electrode </li></ul><ul><li>3O2 - 1½O 2 + 6e - </li></ul><ul><li>This gives an overall equation of: </li></ul><ul><li>Al 2 O 3(l) 2Al (l) + 1½O 2(g) </li></ul>
  9. 10. <ul><li>As titanium can’t be reduced with carbon, it is reduced by sodium or magnesium </li></ul><ul><li>This is an expensive process as the titanium oxide is first converted to titanium chloride by reacting it with coke and chlorine at 1173K </li></ul><ul><li>TiO 2(s) + 2C (s) + 2Cl 2(g) TiCl 4(l) + 2CO (g) </li></ul><ul><li>The titanium chloride is then reduced by sodium or magnesium into titanium under an inert argon atmosphere at 1300K </li></ul><ul><li>TiCl 4(l) + 4Na (l) Ti (l) + 4NaCl (l) </li></ul>
  10. 11. <ul><li>Tungsten is extracted from its oxide, WO 3, by reduction with hydrogen at high temperatures </li></ul><ul><li>WO 3 + 3H 2 W + 3H 2 O </li></ul><ul><li>However, there is some risk as hydrogen is a flammable gas, so using it as a reducing agent is a last resort. </li></ul>
  11. 12. <ul><li>Recycling scrap metals has many environmental and economic advantages </li></ul><ul><li>It reduces the amount of scrap metal in landfill and it has already been extracted from its ore so energy isn’t required again </li></ul><ul><li>Melting the scrap metal does not in itself produce carbon dioxide unlike extracting metals from their ores however the energy needed to melt the metal will </li></ul>

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