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General Principles And Processes Of Isolation Of Metals

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General Principles and Processes of Isolation of Metals, PDF Notes, Important Questions and Formulas

General Principles and Processes of Isolation of Metals

Metallurgy

General Principles up to Purification Minerals: Naturally occurring chemical substance in which metal exist either in its free state or in combined state is called mineral. Ore: Mineral from which metal can be conventionally and economically extracted is called ore & impurities associated with it is called gangue or matrix

Types of Ores:

  • Sulphide Ores:

  Galena: PbS,                Cinnabar: HgS,

 Zinc blend: Zns,           Chalcopyrite: CuFeS2

 Copper glance: Cu2S     Fool’s Gold: FeS2     

  • Oxide Ores:

 Bauxite: Al2O3.2H2O        Haematite: Fe2O3

 Limonite: Fe2O3. 3H2O     Tin stone or Cassiterite: SnO2  

  • Carbonate Ores:

 Siderite: FeCO3 Calamine: Fe2O3

 Malacite: Cu (OH) 2, CuSO4 Dolomite CaCO3-

                   MgCO3- 2H2O

 lime stone: CaCO3 

  • Sulphate Ores:

 Gypsom: CaSO4.2H2O Anylesite PbSO4

 Glauber’s salt: Na2SO4- 10 H2O Mohr’s salt: Feso4. (NH4)2SO4. 6H2O  

  • Halide Ores:

 Rock Salt: NaCl        Cryolite: Na3AlF6 

Fluorspar: CaF2          Carnallite: KCl.MgCl2.6H2O  

  • Nitrate Ores: 

Chiele Saltpeter: NaNO3    Indian Salt petre: KNO3  

  • Native Ores: 

Those metals which are chemically less reactive. They occur in the earth crust in form of free state (lumbs)

e.g.: Cu, Ag, Au, Hg, Pd, Pt, Bi

General principles and processes involved in the extraction of metal from its ore:

The extraction of metal from its ore is completed in five steps:

Step I: Pulverization: The crushing of ore to powdered state is called pulverisation.

Step II: concentration or Dressing or Beneficiation of ore

Step III: Conversion of Concentrated ore into oxide form

Step IV: Reduction of oxide to the metal

Step V: Purification or refining of crude metal


Step I: Pulverization:

         The crushing of ore to powdered state is called pulverization

         This process in stamp mill or ball mill

Step II: Concentration or Dressing or beneficiation of Ore

(a) By gravity Separation: Ore particles are heavier than gangue particles. This is used for the separation of most of the gangue particles:

⟹By Wilfley Table Method

Aq. Supersion of powdered/Crushed ore

⟹By Hydraulic Classifier

Step III: Conversion of Concentrated ore into oxide form:

It is done either by calcination or by roasting.

(i) Calcination:

  • Calcination is carried out for carbonate, hydrated metal oxide & metal hydroxide ores.
  • It is carried out in the absence of air i.e., heating in absence of air.
  • Due to calcination ore becomes porous.
  • Volatile organic impurities get evaporated eg.

         begin mathsize 12px style table attributes columnalign left end attributes row cell CaCO subscript 3 left parenthesis straight delta right parenthesis end subscript rightwards arrow with straight capital delta on top CaO plus CO subscript 2 end cell row cell CaCO subscript 3 MgCO subscript 3.2 straight H subscript 2 straight O rightwards arrow with straight capital delta on top CaO plus MgO plus 2 CO subscript 2 upwards arrow plus 2 straight H subscript 2 straight O end cell row cell 2 Al left parenthesis OH right parenthesis subscript 3 rightwards arrow with straight capital delta on top Al subscript 2 straight O subscript 3 plus 2 straight H subscript 2 straight O upwards arrow end cell row cell Al subscript 2 straight O subscript 3.2 straight H subscript 2 straight O rightwards arrow with straight capital delta on top Al subscript 2 straight O subscript 3 plus 2 straight H subscript 2 straight O upwards arrow end cell row cell Pb left parenthesis OH right parenthesis subscript 2. PbCO subscript 3 rightwards arrow with straight capital delta on top 2 Pbo plus CO subscript 2 upwards arrow plus straight H subscript 2 straight O end cell row cell FeSO subscript 3 rightwards arrow with straight capital delta on top FeO plus CO subscript 2 upwards arrow end cell row cell Fe subscript 2 straight O subscript 3.3 straight H subscript 2 straight O rightwards arrow with straight capital delta on top Fe subscript 2 straight O subscript 3 plus 2 straight H subscript 2 straight O upwards arrow end cell row cell Cu left parenthesis OH right parenthesis subscript 2. CuCO subscript 3 rightwards arrow with straight capital delta on top 2 CuO plus CO subscript 2 upwards arrow plus straight H subscript 2 straight O end cell row cell text                                                           Black power end text end cell row cell text ZnCO end text subscript 3 rightwards arrow with straight capital delta on top ZnO plus CO upwards arrow end cell end table
end style

Roasting: In the presence of air the sulphide are heated in free supply of air below m.p. Impurities of sulphur, phosphorus, arsenic & antimony are converted into their corresponding volatile oxide & thus get removed. Moisture & water of crystallization are also removed.

eg. (1)begin mathsize 12px style table attributes columnalign left end attributes row cell Pbs plus 3 over 2 straight O subscript 2 rightwards arrow with straight capital delta on top PbO plus SO subscript 2 upwards arrow end cell row cell Pbs plus 2 straight O subscript 2 rightwards arrow with straight capital delta on top PbSO subscript 4 end cell end table end style

(2)begin mathsize 12px style ZnS plus 3 over 2 straight O subscript 2 rightwards arrow with straight capital delta on top ZnO plus SO subscript 2 upwards arrow end style

                       (Utilised in manufacturing of H2SO4)

               ZnS+2O2ZnSO4

Step IV: Reduction of oxide to the metal:

(a) eduction of metal oxide/ Conc. Ore into free metal.

This can be carried out

  1. Chemical reduction
  2. By self reduction or auto reduction or Air Reduction
  3. Metal-displacement method
  4. By electrolytic Reduction
  5. By amulgamation

(i)  (i) & (ii) method are collectively known as Pyrometallury e.g. Sn, Pb, Fe, Hg, Cu, B, Zn, (Based on Ellinghum diagram)

(ii)  step is called hydrometallurgy - Cu, Ag, Au are extracted

(iii) Step is called hydrometallurgy, Alkali, Alkaline earth metals & Al & base electrolysis

(iv) is used for Ag & Au

Step V: Purification or refining of crude metal

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