Permanent magnet magnetic separator

PTMS magnetic separation

what is magnetic separation method？

Calcination whitening
Coal-based kaolin, often containing carbon and organic matter, is grayish black. Diatomaceous earth also often contains organic matter and clay minerals, which are gray or even dark gray. Black talc is dark gray or even black because it contains organic matter or graphite. The most effective way to whiten these non-metallic minerals is calcination. The method is simple, no waste water pollution, and the effect is good.
For example, the coal-based kaolin is whitened, and the organic matter is easily burned at a high temperature. The calcination can remove most of the organic charcoal in the kaolin powder, so that the whiteness is greatly improved. Advantages of calcined kaolin: high whiteness, low density, large oil absorption, increased specific surface area, good insulation, and improved wear resistance and high temperature stability.
When kaolin is calcined at different temperatures, the chemical changes that occur are as shown in the following equation:

Chemical iron removal and whitening
The so-called chemical iron removal is a method of selectively dissolving iron-containing minerals in a material with a chemical agent and then removing it.

Reduction method
Insurance powder reduction method. At present, the reducing agent commonly used in the industry is sodium dithionite, commonly known as insurance powder, and its molecular formula is Na2S2O4. It is a strong reducing agent, iron oxide is soluble in acid but requires a large amount of acid, and in the presence of the insurance powder, the ferric iron in the iron oxide can be reduced to divalent iron ions.

For example, illite, the essence of reduction whitening is to reduce the insoluble Fe3+ in illite clay to soluble Fe2+, and then remove it by washing. Although the method has low cost and quick reaction, it has large amount of insurance powder and heavy environmental pollution. Shortcomings such as harsh process conditions.

Acid leaching method.

Acid-leaching bleaching usually uses hydrochloric acid or sulfuric acid as the leaching agent, or organic acid and complexing agent as the leaching agent, and converts the insoluble iron into easily soluble iron ions under heating conditions, thereby obtaining higher whiteness. Clay minerals.
For example, for iron impurities containing extremely fine intercalated crystal structure in feldspar ore, it is difficult to remove by general iron removal method, and acid leaching can achieve better results. Zheng Yu et al. discovered through experiments that iron, which exists in the form of minerals such as magnetite, hematite, and pyrite, is easily removed by sulfuric acid leaching, while iron is present in the form of sodium iron amphibole and biotite. It is more difficult to remove. The whitening effect of the zeolite by the acid leaching method is good. Sulfuric acid has better effect than hydrochloric acid and oxalic acid, high concentration, long acid leaching time, lower concentration and shorter time.
Acid-soluble hydrogen reduction method. The basic principle of the acid-dissolved hydrogen reduction method is that the active metal element such as zinc powder or aluminum powder is used as a reducing agent, and H+ in an acidic medium such as hydrochloric acid, sulfuric acid or oxalic acid is replaced to form H2 gas, and then the hydrogen which is continuously formed is insoluble in color. The Fe3+ becomes soluble Fe2+ and is removed with the filtrate.
Oxidation
When minerals contain pyrite and organic matter, the minerals are often gray. These materials are difficult to remove by both pickling and reduction bleaching, which requires bleaching by oxidation. The oxidative bleaching method uses a strong oxidizing agent to oxidize pyrite or the like in a reduced state into a water-soluble ferrous ion in an aqueous medium; at the same time, the dark organic matter is oxidized to become a colorless oxide which can be washed away by water. .
Microbial whitening
Mineral microbial processing technology is an emerging mineral processing technology, which is characterized by low investment, low cost, low energy consumption and light environmental pollution. The microbial oxidation method uses Thiobacillus ferrooxidans as an oxidant to oxidize iron and sulfur in pyrite to soluble Fe2+ and SO2-4 in an acidic medium to separate them from clay minerals.
Surface inorganic coating
There are many methods for surface modification of powders. Among them, liquid phase chemical deposition is very suitable for the preparation of new composite materials. It is a chemical reaction method to deposit certain oxides such as ZnO, Al2O3, SiO2 and CaCO3 on the surface of mineral particles. One or more layers of "modified layer" are formed, so that a new functional material which is not possessed by the original powder, such as mica titanium pearlescent pigment, can be prepared, and the performance cost ratio of the powder material can be increased, and the cost can be reduced. The whitening treatment of the mineral filler can also be realized by using the coating; the SiO2 coating of the ultrafine CaCO3 can make the SiO2 property to a certain extent, surface smoothness, whiteness, acid resistance, dispersibility, specific surface area, etc. There is a big increase; after the wollastonite powder is coated with Al2O3, its dispersibility, fluidity and whiteness are improved.
Natural minerals have a great decrease in whiteness due to the presence of organic matter and impurities such as Fe and Ti. The whiteness of the mineral filler can be improved by a calcination treatment, a chemical method, a microbial method, and a surface coating method. At present, several major whitening technologies have outstanding advantages, but each has obvious shortcomings. The surface coating method can not only improve the whiteness of the product, but also can prepare new functional materials, which can be used as a substitute for high-grade fillers or coatings, increase the performance-price ratio of the powder materials, reduce the cost, and thus have a good development prospect.