blister copper [NCERT]

Extraction of copper from cuprous oxide [copper(I) oxide]

➡️In the graph of DeltaG⁻ vs T for the formation of oxides (Fig. 6.4), the Cu2O

line is almost at the top. So it is quite easy to reduce oxide ores of copper

directly to the metal by heating with coke. The lines (C, CO) and

(C, CO2) are at much lower positions in the graph particularly after

500 – 600K. However, many of the ores are sulphides and some may

also contain iron. The sulphide ores are roasted/smelted to give oxides:

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➡️The oxide can then be easily reduced to metallic copper using coke:

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➡️In actual process, the ore is heated in a reverberatory furnace after
mixing with silica. In the furnace, iron oxide ‘slags of’ as iron slicate is
formed. Copper is produced in the form of copper matte. This contains
Cu2S and FeS.

➡️Copper matte is then charged into silica lined convertor. Some

silica is also added and hot air blast is blown to convert the remaining FeS, FeO and Cu2S/Cu2O to the metallic copper. Following reactions

take place:

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➡️The solidified copper obtained has blistered appearance due to the

evolution of SO2 and so it is called blister copper.

Electrolytic refining

➡️Copper is refined using an electrolytic method. Anodes are of

impure copper and pure copper strips are taken as cathode. The

electrolyte is acidified solution of copper sulphate and the net result

of electrolysis is the transfer of copper in pure form from the anode

to the cathode:

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➡️Impurities from the blister copper deposit as anode mud which

contains antimony, selenium, tellurium, silver, gold and platinum;

recovery of these elements may meet the cost of refining. Zinc may

also be refined this way.