Metallurgy of copper

Metallurgy is the study of techniques and procedures which are used to extract metals from earth crust.
copper is extracted from its pyrite ores.

1. Metallurgy of copper XII CHEMISTRY CHAPTER 5 SIDRA JAVED

2. IMPORTANT ORES OF COPPER Copper pyrite or chalcopyrite CuFeS 2 Chalcocite or copper glance Cu 2 S Malachite green [CuCO 3 .Cu(OH) 2 ] Azurite blue [2CuCO 3 .Cu(OH) 2 ] Bornite or Peacock ore [3Cu 2 S.Fe 2 S 3 ] Cuprite Cu 2 O

3. Extraction of copper Copper is mainly extracted from its sulfide ores by smelting. Following steps are involved in the extraction of copper:

4. concentration Finely crushed ore is concentrated by FROTH FLOATATION PROCESS. Crushed ore is suspended in water containing a little amount of pine oil. A blast of air is passed through the suspension. T he particles mix with the oil and float as a froth which is skimmed. The gangue sinks to the bottom.

5. Froth floatation process

6. roasting The concentrated ore is then roasted in the furnace in the presence of oxygen. During roasting sulfur , arsenic, antimony are converted into oxides and are removed. 2CuFeS 2 + O 2  Cu 2 S + 2FeS + SO 2 S + O 2  SO 2 4As + 3O 2  As 2 O 3 4Sb + 3O 2  2Sb 2 O 3 Cuprous sulfide and ferrous sulfide are further oxidized into their oxides. 2Cu 2 S + 3O 2  2Cu 2 O + 2SO 2 2FeS + 3O 2  2FeO + 2SO 2

7. Roasting

8. smelting Roasted ore is then mixed with coke and sand and is fed into a blast furnace. Hot air converts FeO to iron silicate (FeSiO3 ). FeO + SiO 2  FeSiO 3 (Slag) Cu 2 O + FeS  Cu 2 S + FeO Slag floats over the molten matte of copper.

9. Bessemerization Matte contains Cu 2 S and some unreacted FeO along with silica as impurity. It is converted into copper in a special furnace which is known as "Bessemer converter". When air is blown through the matte, the following reactions take place: 2Cu 2 S + 3O 2    2Cu 2 O + 2SO 2 2Cu 2 O + Cu 2 S   6Cu + SO 2 2FeS + 3O 2  2FeO + 2SO 2 FeO + SiO 2  FeSiO 3 The copper so obtained is called "Blister copper" because, as it solidifies, SO 2 hidden in it escapes out  producing blister on its surface

10. Bessemer converter

11. Impurities in blister copper Blister copper is 99% pure. It contains impurities mainly Fe, As, Zn, Pb , Ag and Au. These impurities adversely affect the electrical as well as mechanical properties of copper .

12. Refining of Blister copper Blister copper is refined by electrolysis. Blocks of blister copper are used as anodes and thin sheets of pure copper act as cathodes. The cathode plates are coated with graphite in order to remove depositing copper . The electrolyte is copper sulfate (CuSO 4 ) mixed with a little amount of H2SO4 to increase the electrical conductivity. Optimum potential difference is 1.3 volt for this electrolytic process.

13. Electrolysis During electrolysis, pure copper is deposited on the cathode plates and impurities which are soluble and fall to the bottom of the cell as anode mud or sludge. At anode: Cu (Blister Copper)  Cu +2 + 2e - At Cathode: Cu +2 + 2e -  Cu (Pure Copper) This electrically refined copper is 100% pure.

14. Electrolytic Refining

15. Pure Copper

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