May 25 2014
Magnetic separation is the process by which magnetically susceptible material is separated from a mixture by the application of a strong magnetic field.
Iron ores are usually subjected to the magnetic separation process, due to the high magnetic susceptibility of iron. Magnetic separation was first applied to the separation of wolframite from cassiterite.
The first magnetic separator, invented by John Prince, consisted of two pairs of electromagnets with a feed belt running over them.
Magnetic separation takes advantage of the differences in magnetic properties of minerals. Most minerals fall into one of these categories: ferromagnetic, paramagnetic, and diamagnetic.
Among these categories, ferromagnetic materials show the highest magnetic susceptibility, hence they can be easily separated by the magnetic separation method.
Technique of Magnetic Separation
Each mineral is separated based on its magnetic susceptibility.
- Ferromagnetic minerals - The poles of a magnet are wrapped in paper and passed over the mineral mixture. Ferromagnetic minerals will stick to the magnets and, thus, get separated from the ore mixture
- Paramagnetic minerals – These are weakly attracted to magnets, hence when the ore mixture containing paramagnetic mineral is passed through a magnetic field the mineral gets attracted. Since paramagnetic materials exhibit different magnetic susceptibility they can be separated from each other by passing a varying magnetic field
- Diamagnetic minerals – These minerals are repelled by a magnetic field; hence they can be separated from a mixture by the passing of a magnetic field
The most commonly used magnetic separator is the Frantz Isodynamic Magnetic Separator. It consists of a large electromagnet, through which mineral mixtures are passed on a metal trough. By varying the strength of the magnetic field or the slope of the tough, different minerals can be separated.
The magnetic separation process is widely used in recycling, the chemical industry, and mining.
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