Transcript Slide 1
EXTRACTING METALS FROM THEIR ORES CONTENTS • • • • • What Are Ores ? Metal Ores How To Extract Metals From Ores ? Reduction Of Metal Ores Effects On Environment WHAT ARE ORES ? • An ore is any naturallyoccurring source of a metal that you can economically extract the metal from. • Aluminium, for example, is the most common metal in the Earth's crust, occurring in all sorts of minerals. An Ore METAL ORES • Metals are usually found in ores containing mineral. • They are combined with Oxygen or Sulphur to form Oxides or Sulphides. • Sulphide Ores are converted to Oxides by heating them in air (called roasting) • Eg : Zinc Sulphide to Zinc Oxide Zinc Sulphide Oxygen Zinc Oxide ZnS (s) 1 ½ O2 (g) ZnO (s) Sulphur Dioxide SO2 (g) HOW TO EXTRACT METALS FROM ORES ? • To obtain a metal , it’s ore , a reducing agent is used to remove the Oxygen , in a reduction reaction . • Examples of some reducing agents : An impure form of carbon Made from Methane and Water REDUCTION OF METAL ORES • Iron , Manganese And Copper Carbon and Carbon monoxide are the reducing agents in the extraction of Fe , Mn & Cu These are cheap because coke can be used which is cheaply produced by heating coal in absence of air Extraction of Iron is done in a blast furnace which reaches temperatures of 2000K Haematite Fe2O3(s) Carbon Monoxide 3CO (g) Iron 2Fe(I) Carbon Dioxide 3 CO2 Manganese is produced by the reduction of its Oxide with Carbon. 2MnO(s) C(s) 2MnI(s) CO2(g) Copper used to be produced this way but nowadays some ores are converted into solutions containing Cu2+ ions. The copper is extracted by reducing with scrap iron This is “greener” as no CO2 is produced and scrap iron is cheap and readily available Also , solution can be made from low grade ore so it is readily available • Extracting Of Other Metals Some metals can’t be extracted using carbon reduction such as Aluminium , Titanium , and Tungsten. Aluminium cannot be extracted because it is more reactive than carbon. Titanium and Tungsten also can’t be extracted using carbon because they will form a metal carbide which would make the metal brittle. • Extraction Of Aluminium Aluminium is extracted from purified bauxite ore (mainly Al2O3) Al2O3 is dissolved in molten cryolite , which forms a solution which melts at around 1240K (Al2O3 melts at 2435K) Therefore less energy is required Aluminium is produced at the negative electrode Oxygen is produced at the positive electrode This gives us an equation : Al2O3(I) 2Al(I) 1 ½ O(g) • Extraction Of Titanium As Titanium can’t be reduced by Carbon it is reduced by Sodium or Magnesium. It is an expensive process as Titanium Oxide is first converted to Titanium Chloride by reacting it with coke and Chlorine at 1173K Titanium Chloride is then reduced by Sodium or Magnesium into Titanium under an inert argon atmosphere at 1300K • Extraction Of Tungsten Tungsten is extracted from it’s Oxide , WO3 by reduction with H2 at high temp. However , there is some risk as H2 is a flammable gas , so using it as a reducing agent is a last resort EFFECTS ON ENVIRONMENT • Recycling scrap metals has many environmental and economic advantage. • It reduces the amount of scrap metal in landfill and it has already been extracted from its ore so energy is not required again. THANK YOU