Wollastonite belongs to a kind of chain like metasilicate, which is generally in the form of fiber and needle. Due to its special crystal morphology and crystal structure, wollastonite has good insulation, high whiteness, good dielectric property, high heat resistance and weather resistance. Wollastonite is widely used in ceramics, chemical industry, metallurgy, papermaking, plastics, coatings and other fields.
2、 Processing of Wollastonite
The main methods of wollastonite beneficiation at home and abroad are hand beneficiation, single magnetic separation, flotation, magnetic separation flotation (or electro separation) combined process. The main purpose of beneficiation is to reduce iron content and separate calcite.
(1) Hand selection
In the mining area, the rich ore block is manually selected or crushed on the conveyor belt, and the rich wollastonite ore block is manually selected. Hand dressing is suitable for better quality ores.
(2) Single magnetic separation
The main associated minerals in wollastonite rocks, such as diopside and garnet, are weakly magnetic minerals, but wollastonite does not show magnetism. Therefore, the dry or wet high-intensity magnetic separation technology can be used to separate wollastonite from each other, so a large number of iron-bearing minerals can be separated and the product purity can be improved.
(3) Single flotation
According to the difference of physical and chemical properties between wollastonite and calcite, flotation can effectively separate them, thus improving the purity of wollastonite products.
(4) Combined process of magnetic separation and flotation
This method is suitable for the treatment of low grade wollastonite. Firstly, the weak magnetic minerals are separated by dry or wet magnetic separation. Then the wollastonite is separated from calcite, quartz and other minerals by flotation. Flotation separation of wollastonite and calcite. There are two main processes for quartz and other minerals.
① Reverse flotation scheme of anionic collector
Calcite is carbonate mineral, wollastonite and quartz belong to silicate mineral. According to the difference of surface electric property between them, by changing the pH value of pulp medium and using adjusting agent to restrain wollastonite, calcite is separated by flotation. Then quartz and wollastonite are separated by flotation. Generally, oxidized paraffin soap is used as the collector of calcite and sodium silicate as the inhibitor of wollastonite and quartz.
② Positive flotation scheme of cationic collector
This method is mainly to adjust the surface electrical properties of wollastonite and calcite minerals, so as to make them with different electric potential, so that wollastonite can be preferentially floated out through electrostatic adsorption with cation collector, while calcite is retained in the flotation tank as tailings. The flotation operation is divided into two sections: the first stage uses amine collectors to float the wollastonite and silicate minerals as foam products, while calcite is retained in the tank. The second stage uses amine ions and anionic collectors to flotation silicate impurities, while wollastonite is recycled as products in the tank.
（2） Grinding and processing of acicular wollastonite
Wollastonite powder is a kind of short fibrous inorganic powder. In some application fields, such as ceramics, microcrystalline glass, metallurgical protective slag and so on, only for Asbestos Substitutes, paper pulp substitutes, reinforced fillers of plastics and rubber, and some coating fillers, there are requirements not only for particle size discovery and distribution, but also for the length diameter ratio of fibrous particles. Wollastonite powder with high aspect ratio (> 10) can replace asbestos fiber, papermaking fiber and high-grade reinforced filler of polymer based composite materials such as plastic and rubber, etc., which has great application value and economic value. Therefore. The processing technology of high aspect ratio wollastonite needle powder is one of the main deep processing technologies of wollastonite.