High-purity quartz sand purification process

Vein quartz is a vein body composed almost entirely of dense quartz blocks. It is white, milky white, mostly in granular structure, and the SiO2 content is usually about 98%. It is one of the ideal mineral raw materials for processing high-purity quartz.

Generally speaking, firstly, the vein quartz or quartzite is crushed to the required particle size and part of the impurities are removed, and then the impurities are separated or dissolved by physical and chemical means. The whole purification process can be briefly summarized as three processes of pretreatment, physical treatment and chemical treatment, specifically using various beneficiation and purification methods such as crushing, grinding, screening, magnetic separation, pickling, and chlorination roasting.

(1) Preprocessing stage

The purpose of the pretreatment stage is to initially screen impurities or crush the quartz raw material to the required particle size that is conducive to the release of impurities and subsequent processing. Generally, mechanical crushing, electric crushing, optical sorting, ultrasonic crushing, thermal shock crushing and other processing methods are used.

(2) Physical processing stage

Physical beneficiation methods mainly include grinding, color separation, magnetic separation, flotation and other methods, which are generally used to deal with the associated mineral impurities in quartz.

Grinding is to remove the thin film iron, bonded and muddy impurity minerals on the surface of quartz sand by means of mechanical force and grinding and peeling force between sand particles, and further grind the aggregates of minerals that have not become monomers, and then achieve further purification of quartz sand through classification. Effect.

Magnetic separation is a beneficiation method that realizes mineral separation in an uneven magnetic field according to the magnetic difference of minerals in ore. A weak magnetic field can remove impurity minerals with strong magnetic properties, such as magnetite; a strong magnetic field can be used to separate impurity minerals with weak magnetic properties, such as hematite, ilmenite, garnet, etc.

Flotation is a beneficiation process in which solid minerals are floated out of a water suspension (ore slurry) based on the differences in the physical and chemical properties of the mineral surface. Flotation can remove most of the mineral particles except quartz and achieve the purpose of enriching quartz. Flotation is the main method for separating quartz from chemically similar minerals such as feldspar and mica.

(3) Chemical treatment stage

Compared with physical beneficiation, chemical treatment is more efficient in removing impurities. Pickling, leaching and thermal chlorination are the three main chemical treatment processes. Pickling and leaching are effective in treating inclusion impurities, while thermal chlorination can remove difficult-to-handle lattice impurities.

Acid leaching is often used to remove thin film iron on the surface of quartz grains and iron impurities inside quartz grains, as well as other impurities. Due to the fact that quartz is insoluble in acid (except HF), other impurity minerals can be dissolved by acid. Pickling uses acids with low solubility such as hydrochloric acid or sulfuric acid, while leaching uses high-temperature hydrofluoric acid to most effectively remove free impurities on the surface and impurities enriched in microcracks and along dislocations. After calcination, sodium hydroxide leaching and mixed acid (hydrochloric acid, nitric acid, hydrofluoric acid) soaking processes, Lei et al. can prepare 99.991% high-purity quartz.

Chlorination roasting, also known as chlorination degassing, refers to the process of converting certain components in mineral raw materials into gaseous or condensed chlorides under the action of chlorinating agents under certain conditions, so that the components are separated or enriched. process. The chlorination roasting process is an effective method to remove impurities in the quartz lattice.