i. The metallurgy used in the extraction of copper is called pyrometallurgy, which involves the use of heat to extract and purify metals. Copper is typically extracted from oxide ores, such as chalcopyrite (CuFeS2) through a process called smelting.
ii. The steps involved in the extraction of copper from chalcopyrite include:
Crushing and grinding: The ore is crushed and ground into a powder to expose the copper minerals.
Concentration: The powder is mixed with water and chemicals to create a slurry, which is then treated with reagents that bind to the copper minerals and cause them to float to the top. This process, called flotation, separates the copper minerals from the rest of the slurry.
Roasting: The concentrated ore is then roasted, which involves heating it in the presence of oxygen to remove moisture and sulfur. The resulting product is called a "calcine."
Smelting: The calcine is then smelted in a furnace to produce a molten substance called a "blister copper," which is about 98% pure copper.
Refining: The blister copper is then refined through a process called electrolysis, in which an electric current is passed through the copper to remove impurities. The resulting product is called "electrolytic copper," which is about 99.9% pure.
The pertinent chemical reactions involved in these steps include:
The roasting process involves the following reaction:
CuFeS2 + O2 -> Cu2S + FeO + SO2
The smelting process involves the following reactions:
Cu2S + O2 -> 2Cu + SO2
Cu + FeS -> Cu2S + Fe
iii. Silica plays a role in the metallurgy of copper as a flux, which is a substance that is added to the ore to lower the melting point of the impurities. This allows them to be more easily removed from the molten copper.
iv. Copper matte is put in a silica-lined converter because silica is resistant to the high temperatures and corrosive gases produced during the conversion process. The converter is used to further purify the copper matte and produce a product called "converter copper," which is about 99.5% pure. The silica lining helps to protect the converter and extend its lifespan.