General Principles and processed Isolation of Metals (Metallurgy)

In the present day, we use different metals but at starting means in ancient times (Stone Age) first known metals are silver, copper, and gold. This occurred in the metallic or native state in form of sand and gravels of riverbeds. 

Elements are found to occur in nature either in the Free State (also called the native state) or in the combined state i.e., in the form of their compounds.

Native state: – elements which are not attacked by moisture, oxygen, and carbon dioxide of the air, occur in the native state for example carbon, Sulphur, gold, platinum, and noble gases.

Combined state: – elements that are readily attacked by moisture, oxygen, and carbon dioxide of the air, occur in the combined state in form of their compounds called minerals.

In the combined state non-metals are found in the reduced form while metals are found in the oxidized form.

The majority of the metals occur in earth crust of the earth in the combined state in form of compounds called minerals.

Minerals are naturally occurring substances that contain metal with impurities Iron is the second most abundant metal (4.7% by mass) in the earth’s crust, it is a very important metal because it forms a large number of compounds that have a variety of uses. Iron is also one of the essential elements in the biological systems (i.e., hemoglobin in blood).

Metal may be found in form of several minerals, but every mineral is not suitable for the extraction of that metal. This is because it may contain either a very low concentration of metal or may contain impurities that may be difficult to remove or the process of extraction from that mineral. Thus, the mineral from which the metal is conveniently and economically extracted is called an ore, thus all ores are minerals but all minerals are not ores.

For example, iron is found in the crust of the earth as oxides, carbonates, and sulfides out of these minerals of iron, oxides of iron are employed for the extraction of the metal because they are most abundant and do not produce polluting gases (like SO2 that is produced in case of iron pyrites). Thus, oxides of iron are called ores of iron.

Electrometallurgy 

The process of extraction of metals by electrolysis of their fused salts is called electrometallurgy, in this process, electron serves as reducing agents.

For example, extraction of aluminum from alumina: – in this process fused alumina (Al2O3) is a bad conductor of electricity. Therefore, to make alumina a good conductor we add cryolite and fluorspar to purified alumina but also reduce the melting point of the mix to around 1140 K.

The electrolysis of the molten mass is carried out in an electrolytic cell or tank made of iron using carbon electrodes. The molten electrolyte is covered with a layer of powdered coke to prevent oxidation and loss of heat due to radiation and the temperature is maintained at around 1173 K. 

Conclusion

Metallurgy is the art and science of extracting metals from their ores, it is usually used commercially rather than in the lab.

Metals are extracted from the crude in two phases: – 

1. Mineral processing or ore-dressing: – Metals are extracted from ores that occur in nature in form of big lumps, these lumps are broken into small pieces with the help of a grinder or crushers and this process is called crushing.
2. Process metallurgy: – many metals can be easily obtained from their respective oxides by reduction; therefore, the extraction of metals involves chemical processes.