Extractive Metallurgy of Copper

Metallurgy Meaning

Metallurgy is viewed as a technique that is used in the extraction of metals in their raw and pure form. Metal compounds mixed with soil, limestone, sand, and rock are known as minerals. Metals for commercial purposes are extracted from minerals at a reasonable cost and with relatively little effort. These minerals are known as ores. A substance that is incorporated into the charge in the kiln to take away the gangue (impurities) is called flux. Metallurgy mainly deals with the process of the formation of alloys and purification of metals.


What Is Copper Mining?

The most common ore used in the copper extraction is Chalcopyrite (CuFeS2), also recognized as Copper Pyrites and other such sulfides. The proportion of copper in the real ore is too limited for straightforward copper extraction to be feasible. The concentration of ore is required, and the Froth Flotation method is used for this process.

Concentration of Ore 

The copper ore is crushed into a fine powder, and the suspension is produced in water. Added to this are Collectors and Froth Stabilizers. Collectors like pine oils, fatty acids, etc. increase the non-wettability of both parts of the metal of the ore and enable it to develop froth and Froth stabilizers like cresols, aniline, etc. in order to maintain the froth. The oil washes the metal, and the gangue is made wet by water. Paddles and air are continuously trying to stir up the suspension to make the froth. This frothy metal is skimmed off onto the edge and left to dry in order to regain the metal.

Smelting of Copper 

Smelting is really a metallurgical technique for extracting base metals from their ores with both the support of heat as well as a chemical reducing agent. Copper Smelting indicates that only the concentrated ore is intensely warmed up by silicon dioxide (silica), calcium carbonate (CaCO3), and air within the kiln. The main steps involved in the copper extraction method are as follows:

  • Reduction of copper in chalcopyrite to copper sulfide

  • Addition of calcium carbonate as a flux just like in blast furnaces, in order to create the slag

  • Removal of iron from chalcopyrite as iron silicate slag

  • Most of the sulphur present in chalcopyrite converts to sulphur dioxide during this process

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The chemical reactions associated with the above-mentioned steps can be written as: 

2SiO2+2CuFeS2+4O2→3SO2+Cu2S+2FeSiO3

The copper produced from that whole procedure is combined with the slag and is termed Matte Copper because of its colour, texture, and appearance. This consists primarily of Cu2S, which is lessened to pure metal by blasting Matte Copper with air.

Cu2S+O2→ SO2 + 2Cu

The Sulphur dioxide leaks out of copper, causing bubbles to show up and burst as and when the SO2 escapes. The above tends to cause the end product to have a really blistery appearance and is therefore called Blister Copper, which is actually 98 – 99.5 percent pure.

Copper is an exceptional conductor of electricity and, integrated with its ductility, is the perfect metal suitable for electrical wiring in both household and commercial areas due to its properties. The age of electricity and technology might have been a fantasy without such great metal. 

Example Questions

Question 1) Which metals occur in nature in their native state? 

Answer) Metals that lie below hydrogen in the electrochemical series like Copper, Silver, Gold, Platinum, etc. are not readily reacted by oxygen and carbon-di-oxide present in the atmosphere and hence these occur in nature in their native state. 

Question 2) What is gangue? And what is the role of a stabilizer in the froth floatation process? 

Answer) The earthy impurities encountered during metal extraction from ores are called gangue. Chemical compounds like cresols and aniline help in stabilizing the froth and hence are called froth stabilizers and are used in the froth floatation process.

FAQ (Frequently Asked Questions)

1. What is the difference between calcination and roasting?

  • Calcination

Calcination involves heating of solids at extreme temperatures for the purpose of eliminating volatile substances, oxidizing a part of the mass, or making them brittle. Calcination is thus occasionally regarded to also be a purification process.

 The production of lime from limestone is a typical example. Throughout this process, the temperature of the limestone is high enough to expel carbon dioxide, generating the lime in a highly crumbly or easily powdered condition. Calcination in specific cases can also be carried out in furnaces constructed for excluding air that might be replaced by inert gases.

  • Roasting 

Roasting is a procedure of heating the sulfide ore at an increased temperature in the presence of air. It is a step in the production of many minerals. In particular, roasting is a metallurgical process that involves gas-solid reactions at extreme temperatures with the objective of purification of metallic parts.


2. Why is the froth floatation method used to extract sulphide ores? Why is roasting carried out in sulphide ores and not in carbonate ores?

It is an ideal method for the concentration of sulphide ores because the froth flotation method is based on the preferential moisturizing properties of the frothing agent and the water, and the sulphide particles of the ore stick to the oil droplets and start rising in the form of the froth.

Roasting is a method in which the sulphides of some of these metals are heated in surplus air. This is conducted on sulphide ores, to oxidize sulphur to form sulphur dioxide, so that it manages to escape, and the compound left behind is a metal oxide, which is possible to reduce easily by reducing agents. It is not used for carbonate ores since carbonate ores have already been oxidized.