What is the reason for the poor effect of magnetic separation?

For the purification of non-metallic minerals such as quartz, kaolin, bentonite, wollastonite, feldspar, talc and attapulgite, 

magnetic separation is the most widely used and effective means to remove iron impurities and magnetic minerals, 

and the effect of magnetic separation directly affects the product quality. Practice shows that the main factors affecting the 

effect of magnetic separation are as follows:

01，Magnetic separation is based on the magnetic separation of minerals. 

The greater the magnetic susceptibility (magnetism) of minerals, the more favorable the magnetic separation; 

At the same time, minerals need to have obvious magnetic differences, otherwise magnetic separation 

and purification cannot be carried out.

02，Magnetic separation is mainly applicable to the separation and purification of coarse and 

medium-sized minerals. When the minerals themselves can reach monomer dissociation,

 they should be as coarse as possible, generally greater than 0.074mm, and the particle size 

should be as uniform as possible. At present, the lower limit of effective magnetic separation

 fineness is 0.035mm. When it is too fine, strong magnetic minerals are easy to be taken away 

by water, while weak magnetic minerals are not easy to be effectively captured. With high 

magnetic field strength and high gradient, the lower limit can reach 10-15 μ m. However, 

the effect of magnetic separation for weakly magnetic minerals is limited.

03，Some minerals, such as hematite and limonite, are prone to argillization and often form 

a slime cover. In addition, their magnetism is weak, which will greatly affect the effect of

 magnetic separation. Measures such as proper cleaning or control of grinding fineness shall be taken.

04，Generally, the mechanical ferromagnetism mixed in the crushing process is strong. 

Weak magnetic separation equipment shall be used to remove it first, and then strong 

magnetic separation equipment shall be used to remove the weak magnetic impurities; 

When the content of strong magnetic substances is large, strong magnetic separation 

equipment is directly used to remove iron.

05，The performance of magnetic separation equipment is an important factor affecting 

the effect of magnetic separation, mainly including magnetic field strength, magnetic field 

gradient and structural characteristics, which should be selected appropriately according to 

different mineral characteristics.

Electromagnetic and permanent magnetic equipment is simple and effective, low cost and widely used,

 but the magnetic field is weak, and the effect on the treatment of weak magnetic minerals is very poor.

The high gradient magnetic separator has a strong magnetic field, which can separate many mineral 

impurities containing iron from the mud. It has been extended from the fields of conventional magnetic 

separation and kaolin purification to the fields of environmental protection, biochemistry and so on.

Superconducting magnetic separator is an equipment that uses superconducting magnet to separate minerals.

 In the beneficiation of non-metallic ores, conventional magnetic separator can better remove paramagnetic 

minerals or ferromagnetic minerals with high magnetic susceptibility, and the lower limit of separation particle 

size can be as low as 20 μ m. But the cost is high.