Title METALLURGY.pdf ✅

 Digital www.allendigital.in [ 173 ] Introduction Metallurgy : The branch of chemistry which deals with the method of extraction of metals from their ores by profitable means. Metal : The element which tends to form positive ion is called a metal. Minerals : The various compounds of metals which occur in the earth's crust and are obtained by mining are called minerals. In earth crust order of abundance of elements is. O > Si > Al > Fe A mineral may be single compound or a mixture. Ore : The mineral from which a metal can be extracted profitably and easily is called an ore. All ores are minerals but all minerals are not ores. Gangue or matrix : The undesirable impurities present in an ore are called gangue. Type of Ores : (I) Combined Ore : Metals placed above H in electrochemical series are generally reactive i.e. why they generally found in combined state. (a) Halide ore / Sulphate ore / Oxy ore : Metals are highly reactive (b) Oxide ore : Reactive metal (Al to Sn) (c) Sulphide ore : Metal placed near H or below H. (Pb, Hg, Cu, Ag) (II) Native Ore : Metal placed below H in electrochemical series are generally found in native state. (Ag, Au, Cu, Pt etc.) Types of metallurgy Pyrometallurgy Hydrometallurgy Electro metallurgy Temp. is involved Solution is involved Electricity involved For heavy metals According to E.C.S IA, IIA, Al Fe, Zn, Cu, Hg, For metals placed below H Sn, etc Cu, Ag, Au Metallurgy 04
NEET : Chemistry [ 174 ] www.allendigital.in  Digital Types of ores and their names TYPES OF ORES S.N. FORMULA OF THE ORE NAME Oxide Ore 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. ZnO (Philosopher's Wool) MnO2 SnO2 Cu2O Fe2O3 Al2O3.2H2O FeO. Cr2O3 Fe3O4 Fe2O3.3H2O TiO2 Zincite Pyrolusite Cassiterite (Tin stone) Cuprite (Ruby Copper) Haematite Bauxite Chromite Magnetite Limonite Rutile Sulphide Ore 1. 2. 3. 4. 5. 6. 7. 8. 9. ZnS HgS PbS Ag2S FeS2 CuFeS2 Cu2S.Ag2S Ag2S.Sb2S3 Cu2S (Copper glance) Zinc Blende (Sphalerite) Cinnabar Galena Argentite or Silver glance Iron pyrite (Fool's gold) Copper pyrite (Chalcopyrites) Copper silver glance Pyrargyrite (Ruby silver) Chalcocite Halide Ore 1. 2. 3. 4. 5. NaCl AgCl CaF2 AlF3.3NaF KCl.MgCl2.6H2O Rock Salt Horn Silver Flourspar Cryolite Carnalite Carbonate Ore 1. 2. 3. 4. 5. 6. 7. 8. MgCO3 CaCO3 MgCO3.CaCO3 ZnCO3 (Smithosonite) PbCO3 FeCO3 CuCO3. Cu(OH)2 2CuCO3.Cu(OH)2 Magnesite Lime stone Dolomite Calamine Cerrusite Siderite Malachite green Azurite Sulphate Ore 1. 2. 3. CaSO4.2H2O MgSO4.7H2O K2SO4.Al2(SO4)3.24H2O Gypsum Epsomite Or Epsom salt Alum Nitrate Ore 1. 2. NaNO3 KNO3 Chile- Salt Peter Salt peter or Indian salt peter Phosphate Ore 1. Ca3(PO4)2 Rock Phosphate
Metallurgy  Digital www.allendigital.in [ 175 ] (A) concentration of the ore or benefaction or dressing of ore: The removal of impurities from the ore is called its concentration or to increase the concentration of ore in ore sample. Two process – (1) Physical (2) Chemical 1. Physical Concentration : (I) Gravity Separation (Levigation) : This method of concentration of the ore is based on the difference in the gravities of the ore and the gangue particles. Powdered ore is agitated with a running stream of water. The lighter gangue particles are taken away by water while heavier ore particles settle down. Used for concentration of oxygenated ores. (II) Froth Floatation Method This method is mainly employed for the concentration of sulphide ores. The method is based on the different wetting characteristics of the gangue and the sulphide ore with water and oil. The gangue particles are preferentially wetted by water and the ore particles by oil. The crushed ore along with water is taken in a floatation cell. Various substances are added depending on the nature of the ore and a current of air is blown in. The substances added are – (i) Frothers :– They generate a stable froth which rises to the top of the tank. Example of frother is pine oil, Eucalyptus oil, fatty acids etc. (ii) Collectors or floating agents :– They attach themselves by polar group to the granules of the ores which then become water repellent and pass on into the froth. Example: sodium ethyl xanthate, pine oil and fatty acid. (iii) Froth stabilisers :- They stabilise froth. Ex. Cresol, Aniline etc. (iv) Depressants :– These reagents depress the floatation property and help in the separation of different sulphide ores present in a mixture. for eg. in case of an ore containing ZnS and PbS the depressant used is NaCN. It selectively prevents ZnS from coming to the froth but allows PbS to come with the froth. NaCN + (ZnS + PbS) ⎯⎯→ Na2[Zn(CN)4] + PbS (remain in the solution) (comes to the froth Powdered Ore + Oil + Water Compressed air Light ore particle in froth Concentrated Ore Gangue [Froth floatation process]
NEET : Chemistry [ 176 ] www.allendigital.in  Digital (III) Magnetic Separation :- If either the ore or the gangue (one of these two) is capable of being attracted by a magnetic field, then such separations are carried out (e.g. in case of iron ores) e.g. • SnO2 which is non-magnetic having the impurities of FeWO4 + MnWO4 (Magnetic) • FeO.Cr2O3 (Magnetic) having the impurities of SiO2 (Non-magnetic) Magnetic roller Magnetic particles Non-magnetic particles Finely ground ore Fig. 6.1: Magnetic separation [Schematic] 2. Chemical Concentration (Leaching) : In this process we use suitable reagent which react with ore to form water soluble complex while impurities remain insoluble. Applicable for Al, Ag, Au. (a) for Al Red Bauxite ⎯⎯→ Al2O3.2H2O + Fe2O3/FeO (Major impurities) White Bauxite ⎯⎯→ Al2O3.2H2O + SiO2 (Major impurities) for red bauxite : (i) Bayer's process : NaOH is used. Al2O3 + NaOH ⎯→ NaAlO2 ⎯⎯⎯⎯⎯⎯⎯→ H O(excess)&CO 2 2 Al(OH)3 + NaOH Fe2O3/FeO + NaOH ⎯⎯→ insoluble (Basic) (ii) Hall's process : Na2CO3 is used. Al2O3 + Na2CO3 ⎯→ 2NaAlO2 ⎯⎯⎯→ 2 HOH CO Al(OH)3 + Na2CO3 for white bauxite (i) Serpeck's process : a mixture of (C + N2) is used Al2O3 + N2 ⎯⎯⎯⎯→ 1800°C -CO AlN ⎯⎯⎯→ H O2 Al(OH)3 + NH3 C + SiO2 ⎯→ CO2 + Si  (b) for Ag and Au (Cyanide Process) (I) for Ag Ag2S + 4NaCN ⎯⎯⎯→2 2O 2Na [Ag (CN)2] + Na2SO4 [in absence of O2, reaction become reversible] 2Na[Ag (CN)2] + Zn ⎯→ Na2 [Zn (CN)4] + 2Ag  (II) for Au Au + KCN + H2O ⎯⎯⎯→ O2 K [Au (CN)2] + KOH K[Au (CN)2] + KOH + Zn ⎯→ K2ZnO2 + KCN + H2O + Au 