Methods for Purifying High-Purity Quartz Sand!

Recently, the Ministry of Natural Resources officially designated high-purity quartz sand as my country's 174th new mineral resource. The requirements stipulate that after beneficiation and purification, the silica purity of high-purity quartz ore must be no less than 99.995% (4N5 grade), and the impurity and inclusion content must meet the stringent requirements of high-tech fields such as semiconductors and photovoltaics. This announcement has injected new vitality into the development of related industries. This article will introduce the standards for high-purity quartz sand and high-purity quartz purification technologies.

01I. Standards and Applications of High-Purity Quartz Sand

Generally, a 4N (99.99%) purity level of high-purity quartz sand is sufficient to meet the material requirements for high-end products. However, in more advanced fields such as semiconductors, the silica purity needs to reach 4N5 (99.995%) or even 5N (99.999%) or higher. The following is a classification table of high-purity quartz sand grades:

4N grade: SiO₂ content > 99.99%, used in optics, optical communication, and other industries for manufacturing high-end optical devices and optical fibers for the optical communication industry;

4N8 grade: SiO₂ content > 99.998%, used in the solar photovoltaic industry for manufacturing monocrystalline silicon crucibles, polycrystalline silicon crucibles, high-quality quartz glass and related products;

5N2 grade: SiO₂ content > 99.9992%, used in the semiconductor industry and chip manufacturing industry for manufacturing CZ crucibles, high-purity quartz glass for semiconductors, and high-end quartz crucibles for semiconductors;

6N grade: SiO₂ content > 99.9999%, used in the semiconductor, military, and aerospace industries for manufacturing sensors, lithography lenses, and aerospace materials.

02II. High-Purity Quartz Sand Beneficiation Methods

The conventional methods for beneficiating high-purity quartz sand are mainly physical and chemical beneficiation methods.

1. Physical Beneficiation Methods for High-Purity Quartz Sand

Quartz Sand Magnetic Separation: This method mainly utilizes the magnetic difference between quartz and other magnetic impurities to achieve enrichment through high-gradient magnetic separation. This type of magnetic separator generates a strong magnetic field of 4-5T, which, combined with stainless steel wool media, forms a high-gradient field strength to remove magnetic impurities such as hematite and magnetite. The iron removal efficiency can reach 98%.

Quartz Sand Flotation: Primarily based on the difference in surface electrical properties between quartz sand and silicate minerals (feldspar, mica, etc.), anionic and cationic flotation methods are used to complete mineral processing. First, cationic direct flotation uses sodium oleate as a collector to adsorb quartz in an alkaline environment (pH=9-10). Then, cationic reverse flotation is used to collect impurities in an acidic environment. Optimizing the reagent ratio and pH value can reduce the content of impurities such as Al₂O₃.

Quartz Sand Gravity separation: This mainly relies on the density difference between quartz sand and other impurity minerals, employing gravity separation equipment such as spiral sluices, shaking tables, and hydrocyclones to achieve separation. Spiral sluices utilize the combined effects of gravity, centrifugal force, and water flow to allow denser quartz sand particles to settle rapidly. Shaking tables utilize the reciprocating motion of the bed surface; under the action of water flow and bed vibration, denser quartz sand first settles at the bottom of the bed. Hydrocyclones, under the action of centrifugal force, allow denser quartz sand particles to move downwards along the vessel wall and be discharged from the bottom flow, thus achieving effective mineral separation.

2. High-purity quartz sand chemical beneficiation method

Acid leaching process: A ternary mixed acid system of HCl-H₂SO₄-HF is used, reacting at 80-90℃ for 6-8 hours to dissolve metal oxide impurities. Ultrasonic enhancement of mass transfer further significantly reduces the content of impurities such as K₂O and Na₂O, improving acid leaching efficiency and impurity dissolution rate.

Chlorination roasting: This involves introducing Cl₂ or HCl gas at a high temperature of 1200-1400℃ to react chemically with impurities such as iron and titanium, generating volatile metal chlorides which are then discharged. After roasting, the quartz sand product is rapidly cooled to prevent impurities from being re-adsorbed or reacting with the quartz sand during cooling. The cooled quartz sand undergoes subsequent processing such as screening and grinding to obtain high-purity quartz sand products.

The above is an introduction to high-purity quartz sand. For a long time, my country has relied on imports in the field of high-purity quartz sand. Now, with continuous technological innovation in my country, strong technical support has been provided for achieving domestic substitution of high-purity quartz sand.

In the future, accelerating mineral exploration and prospecting will allow domestically produced high-purity quartz sand to drive cost reduction and efficiency improvement in the photovoltaic industry, enhancing the global competitiveness of my country's photovoltaic industry. Xinhai Mining Equipment boasts extensive experience in quartz sand mining and beneficiation. We offer clients an integrated, innovative model encompassing mine technology consulting and experimental research, mine design, complete equipment manufacturing and procurement, civil engineering construction, installation, commissioning and delivery, mine construction management, mine production operation management and services. This significantly improves mine efficiency and creates added value for our clients! Please feel free to contact us if you have any needs.