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Silica purification method

250 22.Jun.2022 KZ Editor

The main mineral of silica is quartz, and it generally also contains various impurity minerals such as feldspar, mica, clay and iron. To make high-purity and ultra-high-purity quartz raw materials, it is necessary to remove all impurities other than silica. The main harmful impurities are minerals containing iron and aluminum. Therefore, how to purify silica sand raw materials is mainly reflected in the treatment of iron and aluminum. Effective removal of impurities.

According to the impurity components of silica raw materials and the occurrence state of inclusions on the surface of silica mineral particles, the purification process is mainly divided into scrubbing, magnetic separation, flotation, acid leaching, etc. The following editor will give a brief introduction to these processes.

Silica scrub purification

Scrub is a purification method that removes the thin film iron and mud-containing impurities on the silica surface through mechanical force and friction between mineral particles. The shale impurities in the silica minerals can be effectively removed through the classification operation. The main scrubbing methods are mechanical scrubbing, rod friction scrubbing, high-efficiency strong scrubbing and ultrasonic scrubbing.

01  Mechanical scrubbing

Mechanical scrubbing of iron is a process of removing thin-film iron and other impurity minerals on the surface of ore particles by means of external force and friction and collision between silica ore particles through equipment. Studies have shown that when the concentration of silica scrubbing pulp is between 50-60%, a better purification effect can be obtained.

02  stick friction scrub

This process can strengthen the scrubbing effect, and at the same time change the particle size of silica minerals, which provides a mineralogy basis for further sorting of silica. The factors affecting the scrubbing effect of rod friction are the concentration of silica slurry, scrubbing time, the amount of rods added and the ratio of rods. The rod friction scrubbing process is selective, and the particle size of the mineral products after scrubbing is relatively uniform, and the phenomenon of over-grinding is less.

03 Dosing high-efficiency and strong scrubbing

The electric repulsion between the silica and the surface of the impurity mineral particles is increased by the drug, and the separation effect between the mineral particles is enhanced.

04 Ultrasonic Scrub

The secondary iron film is the main reason that the silica sand iron is too high and difficult to purify. The process can remove the secondary iron film on the surface of the silica mineral particles, and use the action of ultrasonic waves to remove the impurity minerals adhering to the surface of the silica particles to achieve impurity removal and purification.

Silica Magnetic Separation and Purification

Magnetic separation and purification of silica can effectively remove magnetic minerals including conjoined bodies, such as hematite, limonite, biotite, ilmenite, pyrite and garnet, etc., and also remove mineral particles wrapped by magnetic minerals. Magnetic separation and purification can be classified into two categories: dry and wet. The higher the magnetic field strength, the higher the impurity detachment rate of dry magnetic separation and purification of silica. The test proves that when the magnetic field strength is controlled at 10000Oe, the obtained SiO2 is ≥99%, and the Fe2O3 content is ≤0.07%. The effect of magnetic separation to remove iron and purify silica is directly related to the number of magnetic separations and the strength of the magnetic field. The increase has little effect on the iron removal rate. In addition, the finer the silica particles, the better the iron removal effect.

Silica flotation purification

In order to further remove impurities and improve the purity of silica, the flotation method is usually used for purification. Silica flotation purification is mainly used to remove non-magnetic associated minerals such as feldspar and mica in ores.

01 Feldspar mineral impurity removal

Silica and feldspar have similarities in physical properties, structure and chemical composition, and they can be effectively separated by flotation. The conventional flotation process is divided into three categories: "fluorine-free acid", "fluorine-free acid-free" and "fluorine-free acid-free".

Fluorine and acid: Silica-feldspar flotation separation is carried out with hydrofluoric acid activator and cationic collector in an acidic pH environment. The flotation effect is good, easy to control, and the index is stable.

Fluorine-free and acid: avoids the damage of fluoride ions to the environment, but the strong acid liquid in the flotation process will corrode the mineral processing equipment to a certain extent.

Fluorine-free and acid-free: Under natural pH conditions, through reasonable deployment, anions and cations are used as collectors to preferentially flotate impurity minerals.

02Mica mineral impurity removal

The basic charge mechanism of mica is the same as that of feldspar, so in the process of feldspar impurity removal on silica, a large amount of mica ore is removed by flotation along with feldspar. E-8 collector can also be used, and the flotation is carried out by using the charge characteristics of mica lattice. In the slurry with pH value of 2-3, the silica silica hardly floats, so that the mica impurities are floated.

Silica acid leaching purification

Acid leaching purification is to use the principle that quartz is insoluble in acid (except HF) and impurity minerals can be dissolved by acid, to realize the further proposal of silica. Commonly used acid solvent oil HCI, HNO3, H2S04, HFF, etc., the reducing agent can be used sulfurous acid and its salts.

For different metal impurities, the types and concentrations of applicable acids are different. It is generally believed that various dilute acids have significant effects on the removal of iron, aluminum and magnesium; relatively concentrated H2SO4, aqua regia or HF acid can remove titanium and chromium; iron and titanium on the surface of silica particles can be obtained by HF. The purification effect of acid leaching is related to mineral components, acid concentration, soaking time, temperature, mineral particle size, etc., and different acid solutions should be used for purification operations according to the actual situation.

The purification process of silica should be determined according to the occurrence state of impurity minerals in raw materials, the cost of beneficiation, and the use and requirements of the finished concentrate. The editor recommends that enterprises reasonably formulate the process flow of silica beneficiation and purification according to the beneficiation test report of the regular laboratory. Purchase professional and standardized production equipment to ensure that the silica purification achieves the desired effect.

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