Chemistry · Ch 13 — General Principles and Processes of Isolation of Elements
Magnetic Separation
Magnetic Separation
Magnetic separation exploits a difference in magnetic behaviour between the ore mineral and its gangue. It only works, of course, when one of the two — either the wanted mineral or the unwanted gangue — is actually attracted to a magnetic field while the other is not.
The classic example: iron ores
Iron ores are themselves magnetic, so any non-magnetic rocky impurity mixed in with them can be pulled away using this method. This makes magnetic separation a particularly natural fit for iron metallurgy, well before the ore ever reaches a furnace.
The apparatus
As Fig. 6.1 shows, the setup is a conveyor belt that runs over two rollers, with one of them — the one nearer the discharge end — built as a magnetic roller:
- Finely powdered ore is dropped onto the moving belt.
- As the belt carries the mixture over the magnetic roller, the magnetic particles cling to the roller and drop close to the belt in a short arc. …
What this figure shows. A conveyor belt viewed side-on, carrying finely ground ore that is dropped onto it from the upper left (arrow labelled 'Finely ground ore' pointing down onto the belt). The belt runs over two rollers; the one near the discharge (right) end is labelled 'Magnetic roller' and marked with a dot showing it rotates. As the ore stream leaves the belt past this roller it splits into two arcs: darker-shaded 'Magnetic particles' are pulled toward the roller and fall in a short arc close to the belt, while lighter-shaded 'Non-magnetic particles' are flung further out in a longer arc. Two separate heaps of partic …