Magnetic Separation Process

Magnetic separation is an industrial process that uses a magnetic field to separate magnetic separator from non-magnetic ones. Iron, for example is highly magnetic; magnetic separation is sometimes used to separate iron ore from surrounding silicate rock. Magnetic separation can also be used to separate ferrous materials, or materials that contain iron, from industrial waste streams before they can contaminate water supplies.
Magnetic fields
When any mineral is exposed to a magnetic field, it is either drawn by the field or not. Particles that are drawn to the field are called magnetic. There are different sorts of magnetic separators, but the most common is the drum. Essentially a stream of material is dropped onto the outside of a magnetic drum. Non-magnetic or weakly magnetic particles bounce or fall off of the drum. The remaining magnetic particles stick to it until they are scraped off.
Impact grinding
Sometimes, after passing around the first drum, the remaining material hits what is called an impact grinder or impact mill. The impact grinder contains a rapidly spinning wheel that increases the speed of the falling material. The particles then strike what is called an impact block, shattering into even smaller bits. Some mining companies order custom-made grinders that reach several stories high. The smashing of the non-metallic leftovers often reveals particles that are metallic but were covered in non-metallic matter and did not stick to the drum originally.
Sieving
The pieces, which can be as small as half an inch around, then fall onto a screen. The tiniest bits, which are most likely sand particles, are sieved through the screen. These bits of worthless rock and other silicates are called gangue. The gangue is generally discarded. After this screening process, the remaining material is then further dropped onto a second magnetic drum where the process repeats. What material remains will be metal concentrate.
Cost and Types
Magnetic separation is a popular and low-cost method of recovering metals. In addition to the drum method, many other types of separators exist. These include, but are not limited to, pulleys, discs, belts and rings. Flotation machine is used primarily by mining industries but also by environmentalists on industrial wastes and even by those who study space materials. Magnetic separators can be used either "wet" or "dry" and come in countless shapes and sizes.