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Yuan Lei tells you | 5 common purification methods of high purity quartz sand

Release time:

2024-01-29 09:35

 

Yuan Lei tells you | 5 common purification methods of high purity quartz sand

 

  High-purity quartz sand is the material basis for the development of high-tech industries, and its application fields involve optical fiber, military, and aerospace industries.In these fields, the purity requirements of quartz sand raw materials are extremely strict, and the impurity content in quartz sand is very low, especially for Fe, Al and other impurities.Therefore,Quartz sand purification technology is related to the long-term development of China's high-tech fields.At present, the purification technology of high purity quartz sand is monopolized by the United States, Germany and other countries, and restricts the export of purification technology and products, so it is of great significance to master the purification technology of high purity quartz.

 

The mineral impurities in quartz sand are usually present in the form of non-quartz minerals such as feldspar, mica, garnet, zircon, ilmenite and many others.These impurities exist in the following ways:

(1) As a loose associated mineral, it is not chemically combined with quartz crystal;
(2) As mineral fragments, they are chemically and physically combined with quartz crystals on their surfaces. Such impurities are mainly iron-containing minerals and aluminum-containing minerals;
(3) Minerals wrapped by quartz grains or surrounded by quartz crystals bonded to each other;
(4) As interstitial ions replace silicon, these impurities are mainly: Al3+, Fe2+, Fe3+、B3+Ti Title4+、Ge4+、P5+and so on, these ions replace Si4+Forming a covalent bond. When this happens, it is usually accompanied by Li, K、 Na \ nand HDoping of equal elements to maintain SiO2Electric neutrality of the lattice. Al element is one of the main impurity elements in quartz ore, and Al3+and Si4+Similar radius, easy to replace Si4+, Its content is usually as high as thousands of ppm, so the Al content is an important indicator of the quality of quartz ore.

At present, the purification process of high purity quartz sand mainly includes mechanical crushing, magnetic separation, flotation, acid leaching, calcination, water quenching, high temperature chlorination roasting and so on.

1. Mechanical crushing

 

Mechanical crushing is the use of mechanical force to reduce the mineral particle size method.In the high purity quartz purification process, this process is mainlySeparation of non-structural impurities in quartz minerals from quartzNon-structural impurities refer to mineral inclusions (mineral impurities) and gas-liquid inclusions (fluid inclusions). Mineral impurities are found in quartz grain boundaries. After crushing, the particle size of quartz original minerals decreases and the specific surface area increases, so that the impurities between grain boundaries are exposed on the outer surface of quartz particles, thus improving the purification treatment efficiency of subsequent processes.


In the process of mechanical crushing, due to the relatively hard quartz mineral ground, frequent contact with the equipment impact friction, inevitably introduce impurities, causing pollution. The most effective solutions to this problem are:Self-grinding and high-pressure pulse comminution technology.

Self grinding is the grinding material itself as a grinding medium, which can greatly reduce the grinding medium for the desired mineral pollution. High-voltage pulse crushing technology is an advanced crushing technology in the world, by issuing a high voltage of 90 ~ 200kV, and then in an instant through the high-voltage discharge to the solid sample in the water. High-voltage pulse discharge in the formation of micro-plasma channels in the mineral, a shock wave, quartz ore blocks along the grain boundary fracture, selective separation from the mineral grains, is known to be the only one can directly act on the separation method between the grain boundaries.

2. Magnetic separation

 

The principle of magnetic separation is a means of separating magnetic mineral impurities from quartz ore according to the magnetic properties of quartz minerals. In the purification process of high purity quartz,The use and purpose of magnetic separation is to remove some magnetic minerals in quartz primary ore inclusions with magnetic properties., such as magnetic ilmenite, pyrite, limonite and garnet, some magnetic mineral inclusions can also be removed by magnetic separation. Iron-containing impurities, especially magnetic substances, are easy to be effectively magnetized, while quartz minerals, especially non-metallic magnetic substances, cannot be effectively magnetized. A large number of magnetic quartz impurities can be separated and removed from high-purity quartz metal minerals by using this differential magnetic separation method.

The magnetic separation operation has a good effect on the removal and separation of magnetic impurities such as iron and titanium in quartz ore. The magnetic field strength of the magnetic separator can beTo adjust, also known as gradient magnetic separation, with weak magnetic removal of magnetite, with strong magnetic removal of ilmenite, limonite, hematite, garnet and other magnetic minerals. For the presence of heavy mineral impurities in quartz raw ore (specific gravity greater2.86of terrigenous clastic minerals, such as zircon, epidote, garnet, etc.),General use of re-election, strong magnetic separation and other methods. Usually, after magnetic separation, quartz minerals will be scrubbed again, which will improve the purity and whiteness of quartz sand.

3. Flotation

 

Flotation is a selective separation of hydrophobic and hydrophilic substances based on the difference in wettability of the surface of the ore body after natural or modified.In the purification process of high purity quartz,Flotation is mainly used to remove mica and feldspar minerals symbiotic with quartzIt can also float phosphorus and iron minerals.There are many kinds of flotation reagents, which can be divided into collector, regulator and frother according to the nature and function of quartz sand flotation medium and working environment.

According to the different reagents used, quartz sand flotation can be divided into fluorine quartz sand flotation and fluorine-free quartz sand flotation. Fluorine quartz sand flotation is the use of fluorine-containing agents, such as hydrofluoric acid (HF) as feldspar activator, the use of sulfuric acid as a regulator, so that under the strong acidic conditions of pH = 2~3, with dodecylamine and other cations as a collector, pre-adsorption and separation of feldspar after activation. Similarly, fluorine-free quartz flotation is to take sulfuric acid or hydrochloric acid as an activator of impurity minerals in quartz without using fluorine-containing agents, and then use the corresponding collector to separate quartz and impurity minerals by flotation. In addition, some studies have shown that the flotation effect of mixed collector is better than that of single collector, and it is relatively cost-saving.

4. Acid leaching

 

Acid leaching is a means of purifying quartz according to the different solubility of quartz, mica and feldspar in acidic solutions.Acid leaching can effectively remove the oxide film on the surface of iron ore and quartz particles in quartz, and hydrofluoric acid is generally used for mineral impurities such as mica and feldspar..The commonly used acid medium for acid leaching is hydrochloric acid, sulfuric acid, nitric acid, acetic acid and hydrofluoric acid, among which dilute acid has a better effect on the removal of Al and Fe, while concentrated sulfuric acid, aqua regia and hydrofluoric acid with stronger acidity are used for the removal of Cr and Ti.

Studies have shown that dilute acid and hydrofluoric acid can effectively remove Fe, Al, Mg and other metal impurities, but to control the amount of hydrofluoric acid, this is because hydrofluoric acid can attack quartz particles. The use of different kinds of acids also affects the quality of purification processing, and the processing effect of HCl and HF mixed acid is the best.

The essence of acid leaching is the interaction between acid and impurity minerals, so in the process of acid leaching, the temperature has a great influence on the reaction rate and the final purification effect. Yang et al. used hydrochloric acid and oxalic acid as mixed leaching agents to study the effects of acid leaching temperature, time and concentration on Shi Ying purification effect. Finally, the optimal conditions for acid leaching were determined: acid leaching temperature of 60 ℃, acid leaching time of 8h, oxalic acid concentration of 10g/L,HCl concentration of 5%, liquid-solid ratio of 1:5, and stirring speed of 500rpm. The results showed that the removal ratio of iron reached 50%.

High temperature and high pressure leaching is a leaching process to remove impurities in high temperature and high pressure environment, and it is a more mature hydrometallurgical technology in metal ore processing, which can effectively reduce the consumption of acid at high temperature and high pressure. In recent years, high temperature and high pressure leaching technology has also been applied to the treatment of quartz ore. The high temperature leaching pressure used in this process is provided by the closed environment provided by the reaction kettle composed of stainless steel jacket and PTFE liner. Pressure acid leaching can more effectively remove the symbiosis and inclusions, so the leaching process The purification effect of refractory ore is better than that of magnetic separation and flotation.

5. Heat treatment

 

In the high purity quartz purification process, heat treatment refers to the high temperature calcination of quartz (800~900 ℃).Heat treatment in the quartz purification process has two effects, first of all, quartz mineral hard, Mohs hardness of 7, is difficult to grind minerals.However, there is anisotropy in the crystal structure of quartz minerals, and the expansion coefficient of impurities such as muscovite and silicate minerals in the minerals is different from that of quartz.Therefore, after high-temperature calcination and water quenching, quartz minerals expand rapidly when heated, and stress concentration will be caused during emergency contraction, resulting in cracks in minerals, thus realizing quartz crushing.In addition, high-temperature calcination can effectively destroy the structure of muscovite and silicate quartz minerals, and further promote the fragmentation of quartz and the exposure of internal impurities, which is conducive to the subsequent acid leaching process.

High temperature calcination at the same time add chlorinating agent,That is, the use of chlorination roasting method for quartz purification, has been proved to be the most effective method to remove impurities in the quartz crystal lattice. It is the use of metal oxides in high temperature environment and chlorination agent chlorination reaction, so as to generate gaseous metal chloride and volatile, and then achieve the purpose of removing metal oxide impurities. The type of chlorinating agent can be divided into solid chlorinating agent and gaseous chlorinating agent, solid chlorinating agent is generally NaCl, CaCl2U want it4Cl, gaseous chlorinating agent is generally Cl2、HCl。
 
















Common, quartz, minerals, impurities, purification, flotation, quartz sand, removal, high temperature, magnetic separation

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