6 Essential Methods for Magnesite Beneficiation

Magnesite is a carbonate mineral of magnesium, in which magnesium oxide has strong fire resistance and adhesion. Magnesite is the raw material for the production of refractory materials, as well as the main raw material for refining magnesium. The purpose of beneficiation of magnesite is to remove impurities and improve product grade. This article will introduce you to the 6 beneficiation processes of magnesite.

01 Flotation Process

Flotation method is the process that uses the difference of physical and chemical properties of the surface of the target mineral for separation. It is one of the main methods for processing magnesite at present.

The impurities in magnesite can be roughly divided into silicate and carbonate. Silicate includes talc, quartz, serpentine, etc. Carbonate includes dolomite, calcite, etc. The commonly used flotation method is the alternate use of reverse flotation and obverse flotation. First, amine collectors are used for reverse flotation of siliceous minerals, and then fatty acid collectors are used for obverse flotation of magnesite. Obverse flotation is suitable for alkaline conditions. Adding sodium silicate, sodium hexametaphosphate or aspergillus can selectively inhibit some calcium minerals such as dolomite.

02 Magnetic Separation Process

Magnetic separation method uses the magnetic difference of various minerals for separation. The main purpose of magnesite is as the refractory material, but the iron in its ore will endanger the performance and quality of its refractory products. Therefore, magnesite ore used as a refractory material has strict requirements on its iron impurity content. The magnetic separation process can effectively remove the iron in the raw ore and the iron impurities mixed in the crushing and grinding process.

03 Gravity Separation Process

Gravity separation method is to use the density difference between magnesite and associated minerals for separation. The main methods include jigging, shaking table and heavy medium separation. Because the density difference between magnesite and associated minerals is not large, the effect of single gravity separation is very poor. Calcination before gravity separation can reduce the density of magnesite, and the separation effect will be greatly improved.

04 Roasting Process

The roasting method uses the thermodynamic properties of different minerals for separation. When magnesite is roasted to 800-1000℃, it will decompose and escape CO2. and the caustic calcined magnesite produced is brittle, soft and fragile. And the gangue mineral talc will become hard as the temperature rises. Therefore, the separation of the two minerals can be achieved by using the hardness difference between them to selectively crushing and then screening. The roasting method has low cost and simple process, but it also has some limitations. Especially when processing ores with complex mineral composition or high calcium, the effect is relatively poor. Therefore, roasting method is generally used as the pretreatment or preconcentration of other separation processes.

05 Electric Separation Process

Electric separation is a method of separation in a high-voltage electric field according to the different conductivity of the target mineral and gangue mineral particles. For example, a Japanese mine used the critical potential difference of magnesite, talc, and calcite to achieve effective separation of magnesite, calcite, and talc by adjusting the high-voltage positive potential of the electrostatic concentrator.

06 Chemical Separation Process

Chemical separation methods are generally used in the processing of magnesite ore with fine particle size and similar impurities in the ore. The extraction of basic magnesium carbonate from magnesite by chemical processing can be divided into hydrochloric acid method, ammonia method and carbonization method. The process is as follows:

1. First, calcining magnesite at high temperature to increase its surface activity and increase its solubility.

2. Then leaching using hydrochloric acid, nitric acid, sulfuric acid, ammonium salt and bicarbonate

3. According to the leaching degree of magnesium and impurities, different methods can used to precipitate and separate the impurities to obtain high purity MgO products.

07To Wrap Up

The above are 6 processing methods of magnesite. A single beneficiation process generally cannot meet the production requirements, and multiple combined processes are often used in actual production. It is recommended that all mineral processing plants conduct beneficiation tests first, and determine the appropriate beneficiation plan based on the test data, so as to ensure the grade and recovery rate of the concentrate.

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