High-purity quartz prepared by removing quartz lattice impurities through calcination and preparation method thereof

Abstract

This invention provides a method for preparing high-purity quartz by removing lattice impurities from quartz using a roasting method. The method includes: 1) pretreating quartz ore to obtain coarse quartz particles; 2) mixing the coarse quartz particles with borax and then roasting to obtain a roasted quartz product; 3) crushing and sand-making the roasted quartz product and reacting it with a dilute hydrochloric acid solution, filtering after the reaction to obtain refined quartz particles; 4) placing the refined quartz particles in a reaction vessel and subjecting them to hot-press acid leaching with a mixed acid solution, followed by post-treatment to obtain high-purity quartz. This invention uses an additive to roast quartz followed by pressurized and heated acid leaching to purify the quartz, which can effectively remove lattice impurities and inclusions from the quartz. The prepared high-purity quartz has a SiO2 mass percentage of 99.99%~99.999%, and the quartz cell parameter can be obtained from the theoretical standard value of 113.01 Å. 3 Reduced to 112.87 Å 3 .

Description

Technical Field

[0001] This invention relates to the field of high-purity quartz sand material preparation, specifically to a method for preparing high-purity quartz by removing quartz lattice impurities through calcination. Background Technology

[0002] High-purity quartz is a cornerstone material for high-tech industries such as semiconductors, optical communications, and photovoltaics. Its purity directly determines the performance and yield of end products. With industrial upgrading, the requirements for quartz purity (such as SiO2 mass percentage > 99.998%) are becoming increasingly stringent. Against this backdrop, lattice impurities have become the last and most difficult key bottleneck to overcome in improving the quality of high-purity quartz.

[0003] Lattice impurities refer to aluminum (Al), titanium (Ti), sodium (Na), and potassium (K) ions that directly replace silicon (Si) sites in the quartz lattice in an isomorphic manner. This state of occurrence causes the impurity elements to form strong chemical bonds with the quartz matrix, making them difficult to remove using conventional physical beneficiation methods (such as magnetic separation and flotation) or even ordinary acid washing. This prevents further improvement in the quality of most high-purity quartz products on the market, resulting in a large amount of low-quality quartz not being utilized at high value. Previous studies have confirmed that chlorination roasting is effective in removing lattice impurities of Na and K in quartz, achieving the migration of impurities outward through high-temperature and chlorination treatment. However, this method currently has several shortcomings: 1. Chlorination roasting has a certain effect on alkali metal elements such as Na and K, but it is most detrimental to the properties of quartz glass, particularly Al. 3+ and Ti 4+ The removal effect of high-valence ions is relatively small because of their high valence and ionic radius compared to Si. 4+ 1. Smaller differences and stronger binding energy with lattice oxygen result in extremely slow migration and chlorination reaction kinetics at high temperatures, leading to far less than ideal removal rates and limited removal capacity. This makes it more suitable for high-purity quartz sand with low lattice impurity content. 2. To achieve limited purification effects, chlorination roasting typically requires extremely high temperatures (>1000℃) and long holding times. This not only results in huge energy consumption but also places extreme demands on the refractory materials of the roasting kiln, leading to extremely high equipment investment and operation and maintenance costs, severely impacting technical and economic efficiency. 3. The chlorine and hydrogen chloride gases used in chlorination roasting are highly corrosive at high temperatures, posing a serious threat to reaction equipment and piping systems, shortening equipment lifespan. Furthermore, the storage, use, and exhaust gas treatment of these highly toxic and corrosive gases all pose significant safety and environmental risks, presenting a huge challenge to the plant's safety and environmental management.

[0004] Therefore, developing a novel calcination method that can efficiently disrupt the quartz lattice and promote the selective migration and fixation of key impurities (especially Al and Ti) under relatively mild conditions is of great significance for breaking through the technical bottleneck in the preparation of high-purity quartz. Summary of the Invention

[0005] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of this invention is to provide a method for preparing high-purity quartz by removing quartz lattice impurities through calcination; another objective of this invention is to provide a high-purity quartz.

[0006] To achieve the above objectives, the present invention provides a method for preparing high-purity quartz by removing quartz lattice impurities through calcination, the method comprising the following steps: 1) Pre-treat the quartz ore to obtain coarse quartz particles; 2) The coarse quartz particles are mixed with borax and then calcined to obtain the calcined quartz product; 3) The quartz roasting product is crushed and sanded, then reacted with dilute hydrochloric acid solution. After the reaction is completed, it is filtered to obtain refined quartz particles. 4) The refined quartz particles are placed in a reaction vessel and subjected to hot-press acid leaching with a mixed acid solution. After post-treatment, high-purity quartz is obtained.

[0007] Optionally, the quartz ore mentioned in step 1) is a low-quality quartz raw material containing lattice impurities or inclusions inside the quartz, including one of natural crystal, granite pegmatite, vein quartz and quartzite; the pretreatment includes crushing-sand making, scrubbing, magnetic separation, flotation, acid leaching, water washing and drying.

[0008] Optionally, the coarse quartz particles have a particle size of -70 to +150 mesh and a SiO2 mass percentage content of ≥99.9%.

[0009] Optionally, the crushing-sand making refers to a crushing-grinding process with inspection screening and grading screening; the scrubbing includes one or both of mechanical scrubbing and ultrasonic scrubbing, the slurry ratio during scrubbing is 1:3~1:8 kg / L of solid-liquid mass volume ratio of quartz particles after grinding to scrubbing medium, and the scrubbing time is 10min~60min; the magnetic separation is carried out using one or both of superconducting magnetic separator, high gradient vertical ring magnetic separator and wet high intensity magnetic separator, the magnetic field strength of the magnetic separation is 1.3~2.3T, and the magnetic separation needs to be circulated 3~6 times.

[0010] Optionally, the flotation is reverse flotation, the pulp concentration during the flotation is 10-30%, the pH of the pulp is 1.5-3.5, and the pH is adjusted by hydrofluoric acid or dilute sulfuric acid. The flotation uses dodecylamine as a collector, and the amount of dodecylamine added is 100-200g per ton of quartz particles. The flotation froth products during the flotation process include feldspar and mica, and the bottom product is quartz particles.

[0011] Optionally, the acid leaching is carried out using a mixed acid solution, wherein the molar concentration of hydrofluoric acid is 0.2~2.0 mol / L, the molar concentration of hydrochloric acid is 1.2~3.2 mol / L, the molar concentration of nitric acid is 1.6~4.8 mol / L, and the molar concentration of sulfuric acid is 0.5~2.0 mol / L; the solid-liquid mass-volume ratio of quartz particles to the mixed acid solution during the acid leaching is 1:2~1:5 kg / L; the acid leaching temperature is 80~120℃, and the time is 360~600 min.

[0012] Optionally, the water washing is performed by washing the quartz particles after acid leaching with deionized water, and the washing endpoint is when the pH of the filtrate after washing is 6.5~7.0; the drying includes one or two of sun drying, electric heating drying and vacuum drying.

[0013] Optionally, the borax in step 2) is sodium tetraborate pentahydrate or sodium tetraborate decahydrate, and the particle size of the borax is -120 to +200 mesh; the roasting step includes: weighing and mixing the coarse quartz particles with the borax, thoroughly mixing the proportioned coarse quartz particles with the borax, and roasting the thoroughly mixed particles to obtain the quartz roasting product.

[0014] Optionally, the mass ratio of the coarse quartz particles to the borax is 6:1 to 10:1; the mixing is carried out using a mixer, drum mixer, or dynamic reactor at a speed of 20 to 40 r / min for 3 to 10 min; the calcination is carried out in a calcination furnace, which includes one of an atmosphere sintering furnace, a tube furnace, a rotary kiln, and a suspension furnace; the calcination temperature is 750 to 850°C for 1 to 3 h; and the calcined quartz product is a porous, brittle quartz block coated with borosilicate glass.

[0015] Optionally, the crushing-sand making mentioned in step 3) refers to a crushing-grinding process with inspection screening and grading screening, wherein the particle size of the quartz particles after crushing-grinding is -70 to +150 mesh; the solid-liquid mass-volume ratio of the quartz particles after crushing-sand making to the dilute hydrochloric acid solution is 1:2 to 1:5 kg / L, and the mass concentration of the dilute hydrochloric acid solution is 4% to 10%.

[0016] Optionally, the reaction in step 3) includes thorough stirring, heating and dissolution, wherein the thorough stirring time is ≥30 min, the heating temperature is ≥95℃, and the purpose of dissolution is to dissolve the borosilicate glass coated on the surface of the quartz particles in the dilute hydrochloric acid solution.

[0017] Optionally, the equipment used for hot-press acid leaching in step 4) is either a dynamic hot-press acid leaching reactor or a static hydrothermal reactor; the molar concentration of hydrofluoric acid in the mixed acid solution is 0.5~1.5 mol / L, the molar concentration of hydrochloric acid is 0.8~3.2 mol / L, and the molar concentration of nitric acid is 1.2~3.4 mol / L.

[0018] Optionally, during the hot-press acid leaching, the solid-liquid mass-to-volume ratio of the refined quartz particles to the mixed acid solution is 1:2 to 1:5 kg / L, the temperature of the hot-press acid leaching is 150 to 200°C, and the time is 300 to 600 min.

[0019] Optionally, the post-treatment in step 4) includes filtering, washing, and drying the acid-leaching product after hot-pressing and acid leaching; the filtering and washing is performed by using a filter press with a rinsing device to filter the acid-leaching product and washing the filter residue with deionized water, with the endpoint of washing being that the pH of the filtrate is 6.5~7; the drying is performed by air drying, electric heating drying, or vacuum drying of the quartz particles after filtering and washing, with the endpoint of drying being that the moisture content of the dried product is less than 0.1%.

[0020] In another aspect, the present invention provides a high-purity quartz, which can be prepared by the above-described method of removing quartz lattice impurities by calcination.

[0021] Alternatively, the high-purity quartz has a SiO2 mass percentage content of 99.99% to 99.999%, and compared with conventional methods, the quartz unit cell parameter can be improved from the theoretical standard value of 113.01 Å. 3 Reduced to 112.87 Å 3 .

[0022] Compared with the prior art, the beneficial effects of the present invention include at least one of the following: (1) This invention introduces borax (Na2B4O7·10H2O) as a highly efficient reaction aid. At high temperatures, its molten borate can effectively penetrate and destroy the crystal lattice structure of quartz, significantly reducing Al 3+ Ti 4+ The activation energy for the migration and precipitation of high-valence impurity ions from the crystal lattice. Compared to chlorination roasting, which is only effective for Na and K, this invention can precisely target and remove Al and Ti lattice impurities that are most detrimental to the performance of quartz glass. It achieves a leap from "weak selectivity" to "precise and efficient" impurity removal, clearing a key obstacle for the preparation of higher purity quartz products (such as 4N8 and above).

[0023] (2) The addition of borax significantly lowers the melting point of quartz, allowing effective lattice reactions and impurity migration to occur at temperatures far below chlorination roasting (typically >1000℃) (e.g., 600℃~1000℃). This not only significantly reduces energy consumption but also lowers the high-temperature resistance requirements of the roasting equipment, thereby significantly reducing equipment investment costs and production operating costs, making this technology have excellent prospects for industrial application and economic viability.

[0024] (3) The borax used in this invention is a solid, stable, and low-toxic chemical raw material, which completely avoids the use of highly toxic and corrosive gases such as chlorine (Cl2) and hydrogen chloride (HCl) that must be used in chlorination roasting. This not only fundamentally eliminates major safety and environmental risks, but also reduces the special anti-corrosion requirements for equipment materials, simplifies the operation process and exhaust gas treatment system, and makes the production process greener and safer.

[0025] (4) Many domestic quartz raw materials are abandoned because of the high content of impurities inside the quartz. This invention provides a method to improve the final quality of such low-quality quartz raw materials. By reducing the melting point of quartz, the impurities inside the quartz are promoted to migrate outward, so that the low-quality quartz restricted by lattice impurities or encapsulation is transformed into high-quality quartz and thus achieved high-value utilization. Attached Figure Description

[0026] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 Photographs of the appearance of the quartz ore used in Examples 1-3 of the present invention are shown; Figure 2 A comparison chart showing the products calcined at the same temperature with and without the addition of borax additive is shown; Figure 3 A comparison diagram is shown before and after the calcined product was added to hot water and stirred to disperse it. Figure 4 The microstructure of the product after calcination without the addition of borax additive in Example 1 is shown. Figure 5 The microstructure of the product after calcination with borax additive in Example 2 is shown. Figure 6 The microstructure of the high-purity quartz sand prepared in Example 1 is shown. Figure 7 The microstructure of the high-purity quartz sand prepared in Example 2 is shown. Detailed Implementation

[0027] In the following, a method for preparing high-purity quartz by removing quartz lattice impurities using a calcination method and the present invention will be described in detail with reference to exemplary embodiments.

[0028] Exemplary Example 1 Borax is a commonly used flux that can improve the meltability and fluidity of quartz, making it easier to separate and precipitate impurities. At high temperatures, areas of quartz with more impurities will preferentially melt to form a glassy state, which is easily dissolved by acid.

[0029] This exemplary embodiment provides a method for preparing high-purity quartz by removing quartz lattice impurities through calcination, the preparation method including the following steps: S1. Pre-treat the quartz ore to obtain coarse quartz particles.

[0030] In this embodiment, the quartz ore is a low-quality quartz raw material containing lattice impurities or inclusions, including one of natural crystal, granite pegmatite, vein quartz, and quartzite; the pretreatment includes crushing-sand making, scrubbing, magnetic separation, flotation, acid leaching, water washing, and drying.

[0031] In this embodiment, the coarse quartz particles have a particle size of -70 to +150 mesh and a SiO2 mass percentage content of ≥99.9%.

[0032] In this embodiment, the crushing-sand making refers to a crushing-grinding process with inspection screening and grading screening. The particle size of the target product after crushing-grinding is -70 to +150 mesh. Obtaining quartz ore particles with a particle size of -70 to +150 mesh is to ensure the feed particle size of the strong magnetic separation process and to maximize the contact area of ​​the particles in the magnetic field to reduce the speed of the particles passing through the magnetic field, so as to make the magnetic separation of the material more complete.

[0033] In this embodiment, the scrubbing includes one or both of mechanical scrubbing and ultrasonic scrubbing. The slurry ratio during scrubbing is a solid-liquid mass-to-volume ratio of quartz particles after grinding to scrubbing medium of 1:3 to 1:8 kg / L, such as 1:3.1 kg / L, 1:4 kg / L, 1:5.5 kg / L and 1:7.9 kg / L. The scrubbing medium is one or both of industrial water and oxalic acid solution.

[0034] In this embodiment, the scrubbing time is 10 min to 60 min, such as 11 min, 25 min, 44 min and 59 min; wherein, scrubbing can effectively wash away the impurity mineral powder and some amorphous impurities attached to the surface, and minimize the impact of these impurities on the surface of quartz ore particles on the subsequent flotation effect.

[0035] In this embodiment, the magnetic separation is performed using one or two of the following: a superconducting magnetic separator, a high-gradient vertical ring magnetic separator, and a wet high-intensity magnetic separator. The magnetic separation can be multi-stage, with a magnetic field strength of 1.3~2.3T, and requires 3~6 cycles. Specifically, wet magnetic separation utilizes industrial ultrapure water to prepare a slurry with a concentration of 10~60% from the washed hydrous quartz ore particles; for example, the magnetic field strength of dry / wet magnetic separation is 1.5T and 2T, respectively; the number of cycles is 2, 4, and 6. The purpose of magnetic separation is to remove magnetic impurities such as tourmaline, magnetite, and hematite from the raw ore, minimizing their adhesion to the surface of the quartz ore particles and thus affecting the subsequent flotation effect.

[0036] In this embodiment, the flotation is reverse flotation. The pulp concentration during flotation is 10-30%, and the pH of the pulp is adjusted to 1.5-3.5 using hydrofluoric acid or dilute sulfuric acid. Dodecylamine is used as the collector, with 100-200g added per ton of direct flotation extract. During flotation, the flotation foam product consists of gangue minerals such as feldspar and mica, while the bottom product is quartz. Although scrubbing and desliming of the quartz particles can remove some clay minerals, feldspar and mica impurities remain on the surface of the quartz particles. Therefore, the purpose of flotation is to remove silicate minerals such as feldspar and mica from the ore particles, minimizing the impact of gangue minerals on the quartz particles during subsequent roasting.

[0037] In this embodiment, the acid leaching is carried out using a mixed acid solution. The molar concentration of hydrofluoric acid in the mixed acid solution is 0.2~2.0 mol / L, for example, 0.25 mol / L, 0.5 mol / L, 1.3 mol / L, and 1.9 mol / L, etc.; the molar concentration of hydrochloric acid is 1.2~3.2 mol / L, for example, 1.25 mol / L, 1.5 mol / L, 2.3 mol / L, and 3.1 mol / L, etc.; and the molar concentration of nitric acid is 1.6~4.8 mol / L, for example, 1. The concentrations of sulfuric acid are 65 mol / L, 2.5 mol / L, 3.6 mol / L, and 4.7 mol / L, etc., and the molar concentration of sulfuric acid is 0.5~2.0 mol / L, such as 0.55 mol / L, 0.9 mol / L, 1.4 mol / L, and 1.9 mol / L, etc.; the solid-liquid mass-volume ratio of quartz particles to mixed acid solution during the acid leaching is 1:2~1:5 kg / L, such as 1:2.1 kg / L, 1:3 kg / L, 1:3.5 kg / L, and 1:4.9 kg / L, etc.

[0038] In this embodiment, the acid leaching temperature is 80~120℃, such as 81℃, 90℃, 105℃ and 119℃; the acid leaching time is 360~600min, such as 365min, 400min, 510min and 590min.

[0039] In this embodiment, the water washing step involves washing the flotation-processed quartz concentrate with deionized water, and the washing endpoint is when the pH of the filtrate after washing is 6.5~7.0; the drying step involves drying the quartz concentrate after filtration using one or two of the following methods: sun drying, electric heating drying, and vacuum drying, and the drying endpoint is when the moisture content of the quartz concentrate after filtration is less than 0.1%.

[0040] S2. The coarse quartz particles are mixed with borax and then roasted to obtain the calcined quartz product.

[0041] In this embodiment, the borax is sodium tetraborate pentahydrate or sodium tetraborate decahydrate, and the particle size of the borax is -120 to +200 mesh. The roasting step includes: weighing and mixing the coarse quartz particles with the borax, thoroughly mixing the proportioned coarse quartz particles with the borax, and roasting the thoroughly mixed particles to obtain the quartz roasted product.

[0042] The purpose of thoroughly mixing coarse quartz particles with borax is to avoid insufficient reaction during the roasting process.

[0043] In this embodiment, the mass ratio of the coarse quartz particles to the borax is 6:1 to 10:1; the mixing is carried out using a mixer, drum mixer, or dynamic reactor at a speed of 20 to 40 r / min for 3 to 10 min; the calcination is carried out in a calcination furnace, which includes one of an atmosphere sintering furnace, a tube furnace, a rotary kiln, and a suspension furnace; the calcination temperature is 750 to 850°C for 1 to 3 h; the quartz calcination product is a porous, brittle quartz block coated with borosilicate glass, which has high acid solubility.

[0044] In this embodiment, the dehydration of borax begins at around 400°C, while decomposition requires a higher temperature, such as above 800°C. Quartz has a high melting point of approximately 1700°C, but its reaction with alkaline oxides can proceed at a lower temperature. Therefore, the reaction temperature is between 750 and 850°C. During this process, borax is first dehydrated to become anhydrous borax, then decomposes to generate Na₂O and B₂O₃; subsequently, SiO₂ reacts with these oxides to form silicates or borosilicates. For example, Na₂O and SiO₂ react to form sodium silicate (Na₂SiO₃), while B₂O₃ and SiO₂ react to form borosilicate glass. The reaction process includes: 1. Dehydration and decomposition of borax: When borax is heated, it first loses its water of crystallization, forming anhydrous sodium tetraborate (Na₂B₄O₇). Na2B4O7·10H2O Na₂B₄O₇ + 10H₂O↑ If the temperature is further increased to approximately 800℃ or higher, anhydrous borax decomposes into sodium oxide (Na₂O) and boric anhydride (B₂O₃). Na2B4O7 Na₂O + 2B₂O₃ 2. Reaction of quartz with oxides: The generated Na₂O and B₂O₃ react with quartz (SiO₂) at high temperature to produce sodium borosilicate glass or other composite silicates. SiO2 + Na2O + B2O3 Na2O·B2O3·SiO2 (borosilicate glass), Specifically, the specific ratio of reactants can also affect the composition of the product. For example, an excess of SiO2 will lead to the formation of more silicates, while a higher proportion of borax will increase the content of B2O3, forming different glass phases. Furthermore, an excess of borax will cause all the quartz to react and form sodium borosilicate, making it difficult to remove boron impurities in the subsequent process.

[0045] In addition, optical microscopy revealed that the quartz particles in the calcined product exhibited some adhesion. This is because borax acts as a flux during the calcination process, which can improve the meltability and fluidity of quartz, making it easier to separate and precipitate impurities from the quartz particles. At high temperatures, areas with more quartz impurities will preferentially melt to form a glassy state. As the temperature decreases, the quartz particles will adhere to each other.

[0046] S3. The quartz roasting product is crushed and sanded, then reacted with dilute hydrochloric acid solution. After the reaction is completed, it is filtered to obtain refined quartz particles.

[0047] In this embodiment, the crushing-sand making refers to a crushing-grinding process with inspection screening and grading screening. The particle size of the quartz particles after crushing-grinding is -70 to +150 mesh. The solid-liquid mass-volume ratio of the quartz particles after crushing-sand making to the dilute hydrochloric acid solution is 1:2 to 1:5 kg / L, and the mass concentration of the dilute hydrochloric acid solution is 4% to 10%.

[0048] In this embodiment, the reaction includes thorough stirring, heating, and dissolution. The thorough stirring time is ≥30 min, the heating temperature is ≥95°C, and the purpose of dissolution is to dissolve the borosilicate glass coated on the surface of the quartz particles in the dilute hydrochloric acid solution.

[0049] Borax is readily soluble in hot water; at 60°C, 100 grams of water can dissolve 20.3 grams of borax. A better approach is to first separate the quartz from the borax and borosilicate glass by crushing and sand-making the calcined product, and then dissolve the remaining borax and borosilicate glass on the quartz by heating and stirring with dilute hydrochloric acid.

[0050] S4. The refined quartz particles are placed in a reaction vessel and subjected to hot-press acid leaching with a mixed acid solution. After post-treatment, high-purity quartz is obtained.

[0051] In this embodiment, the equipment used for hot-press acid leaching is either a dynamic hot-press acid leaching reactor or a static hydrothermal reactor.

[0052] In this embodiment, the molar concentration of hydrofluoric acid in the mixed acid solution is 0.5~1.5 mol / L, for example 0.51 mol / L, 0.8 mol / L, 1.3 mol / L and 1.45 mol / L, etc.; the molar concentration of hydrochloric acid is 0.8~3.2 mol / L, for example 0.85 mol / L, 15 mol / L, 2.3 mol / L and 3.1 mol / L, etc.; and the molar concentration of nitric acid is 1.2~3.4 mol / L, for example 1.25 mol / L, 1.5 mol / L, 2.3 mol / L and 3.3 mol / L, etc.

[0053] In this embodiment, the solid-liquid mass-volume ratio of the refined quartz particles to the mixed acid solution during the hot-pressing acid leaching is 1:2 to 1:5 kg / L, for example, 1:2.1 kg / L, 1:3 kg / L, 1:3.5 kg / L and 1:4.9 kg / L.

[0054] In this embodiment, the temperature of the hot-press acid leaching is 150~200℃, such as 152℃, 170℃, 185℃ and 195℃; the time of the hot-press acid leaching is 300~600min, such as 365min, 400min, 510min and 590min.

[0055] In this embodiment, the post-processing includes filtering, washing, and drying the acid-leaching product after hot-pressing and acid leaching. The filtering and washing process involves using a filter press with a rinsing device to filter the acid-leaching product and washing the filter residue with deionized water. The washing endpoint is when the pH of the filtrate is 6.5-7. The drying process involves drying the quartz particles after filtering and washing by air drying, electric heating, or vacuum drying. The drying endpoint is when the moisture content of the dried product is less than 0.1%.

[0056] The hot-press acid leaching process involves, on the one hand, leaching out impurity elements in the heat-treated quartz particles, including element B introduced by borax, and on the other hand, dissociating the quartz particles that adhered during the heat treatment process and corroding the precipitated impurity defect areas, thereby achieving the effects of lattice impurity precipitation and erosion.

[0057] This invention has a significant effect on removing lattice impurities and inclusions from quartz during the purification process, and reducing the content of Al, Ti, Na, and K impurities in quartz. It provides a method to improve the final quality of low-quality quartz raw materials. By lowering the melting point of quartz, it promotes the migration of impurities from inside the quartz to the outside, and provides a new technology for preparing high-purity quartz by high-temperature heat treatment in industrial production.

[0058] Exemplary Example 2 This exemplary embodiment provides a high-purity quartz, which can be prepared by a method for removing quartz lattice impurities by calcination as described in Exemplary Embodiment 1.

[0059] In this embodiment, the SiO2 mass percentage of the high-purity quartz is 99.99%~99.999%. Compared with conventional methods, the quartz unit cell parameter can be improved from the theoretical standard value of 113.01 Å. 3 Reduced to 112.87 Å 3 .

[0060] To better understand the exemplary embodiments of the present invention described above, further explanation is provided below with reference to specific examples.

[0061] Example 1 The quartz ore used in Examples 1-3 is sample Q-1, such as Figure 1 As shown, this is vein quartz, which contains a large number of quartz inclusions and lattice impurities.

[0062] The high-purity quartz in this example is prepared using a conventional purification method, which includes the following steps: 1) The raw ore is ground into powder using a rod mill with a zirconium oxide lining, and the grinding time is 90 seconds.

[0063] 2) Screening: Use 70 mesh and 150 mesh vibrating screens for screening. Collect the products under the 70 mesh screen and over the 150 mesh screen as concentrate. Collect the products over the 70 mesh screen and grind them again to finally obtain quartz ore particles of -70 to +150 mesh.

[0064] 3) Scrubbing: The sieved product is scrubbed to remove mud. The scrubbing solution is a 5% oxalic acid solution, and the scrubbing method is mechanical scrubbing.

[0065] 4) Magnetic separation: The quartz ore particles after scrubbing and desliming are subjected to wet magnetic separation, wherein the slurry concentration of the wet magnetic separation is 40% and the magnetic field strength of the wet magnetic separation is 1.5T.

[0066] 5) Acid reverse flotation: The magnetic separation product of -70~+150 mesh is subjected to flotation. The flotation conditions are as follows: the pH of the pulp is adjusted to 2.5 with hydrofluoric acid, dodecylamine is used as the collector, the pulp concentration is 20%, and the dodecylamine concentration is 150 g / t. Quartz flotation concentrate is obtained.

[0067] 6) Washing and drying: Wash the quartz flotation concentrate obtained in step 5) with deionized water until the pH returns to neutral. Place the washed quartz ore particles into an oven for electric heating and drying.

[0068] 7) Segmented Roasting: The dried quartz flotation concentrate from step 6) is subjected to segmented roasting. Ammonium chloride is mixed with the quartz flotation concentrate and coated, with a mass ratio of ammonium chloride to quartz flotation concentrate of 1:40. After mixing for 50 minutes, roasting is carried out under N2 gas protection. The roasting process is set in two stages: the first stage roasting temperature is 600℃ and the holding time is 180 minutes; the second stage roasting temperature is 1200℃ and the holding time is 180 minutes. Borax-free roasted product is obtained as follows: Figure 2 As shown in the upper middle figure, its microstructure is as follows: Figure 4 As shown.

[0069] 8) Acid leaching: The roasted product obtained in step 7) is subjected to acid leaching in a mixed acid solution, wherein the molar concentration of hydrofluoric acid in the mixed acid solution is 1.5 mol / L, the molar concentration of hydrochloric acid is 2.0 mol / L, the concentration of nitric acid is 4.0 mol / L, the concentration of sulfuric acid is 1.5 mol / L, the solid-liquid mass ratio of acid leaching is 1:4 kg / L, the acid leaching temperature is 180℃, and the acid leaching time is 600 min.

[0070] 9) Washing and drying: The quartz flotation concentrate obtained in step 8) is washed with deionized water until the pH returns to neutral. The washed quartz particles are then placed in an oven for electrically heated drying. The microstructure of the prepared high-purity quartz sand is as follows. Figure 6 As shown.

[0071] 10) Testing: The prepared quartz sand was ground to below 200 mesh using an agate mortar and pestle for XRD phase composition analysis. X-ray diffraction was performed using an X'pert Pro X-ray diffractometer manufactured by Panaco GmbH, Netherlands. Test conditions: Cu target, tube voltage 40kV, tube current 40mA, emission slit (DS): (1 / 2)°, anti-scattering slit (SS): 0.04 rad; receiving slit (AAS): 5.5mm; scan step: 0.02°; scan range: 3°~80°, continuous scanning. The XRD test data were refined, the cell volume was calculated, and the lattice impurity content was evaluated. The test results were fitted using X'pert HighScore Plus software, with the fitting referenced to the theoretical value of α-quartz (Reference code: 00-046-1045) in the Cell + zero shift mode. The relevant fitting results are shown in Table 1.

[0072] Table 1. Results of XRD cell parameter fitting calculation after sample purification.

[0073] Samples were sent to the National Silicon Inspection Center for testing. Each sample weighed 10g. The testing and judgment were based on JY / T 0567-2020, "General Rules for Inductively Coupled Plasma Emission Spectrometry Analysis." The test results are shown in Table 2. The total impurity content of the prepared high-purity quartz was 66.18 ppm, and the quartz cell parameter was 113.03 Å. 3 The value is greater than the theoretical standard value, indicating that it still contains a large number of lattice impurities that have not been completely removed.

[0074] Table 2. ICP test results of the final purified product of the concentrate obtained from the conventional high-purity quartz preparation process of sample Q-1.

[0075] Example 2 This example demonstrates the preparation of high-purity quartz using a calcination method described in this invention to remove impurities from the quartz lattice. The preparation method includes the following steps: 1) The quartz ore was ground using a rod mill with a zirconium oxide lining, and the grinding time was 90 seconds.

[0076] 2) Screening: Use 70 mesh and 150 mesh vibrating screens for screening. Collect the products under the 70 mesh screen and over the 150 mesh screen as concentrate. Collect the products over the 70 mesh screen and grind them again to finally obtain quartz ore particles of -70 to +150 mesh.

[0077] 3) Scrubbing: The sieved product is scrubbed to remove mud. The scrubbing solution is a 5% oxalic acid solution, and the scrubbing method is mechanical scrubbing.

[0078] 4) Magnetic separation: The quartz ore particles after scrubbing and desliming are subjected to wet magnetic separation, wherein the slurry concentration of the wet magnetic separation is 40% and the magnetic field strength of the wet magnetic separation is 1.5T.

[0079] 5) Acid reverse flotation: Quartz ore particles of -70 to +150 mesh are subjected to flotation. The flotation conditions are as follows: the pH of the pulp is adjusted to 2.5 with hydrofluoric acid, dodecylamine is used as the collector, the pulp concentration is 20%, and the dodecylamine concentration is 150 g / t. Quartz flotation concentrate is obtained.

[0080] 6) Acid leaching: The quartz flotation concentrate obtained in step 5) is subjected to acid leaching with a mixed acid solution, wherein the molar concentration of hydrofluoric acid is 1.2 mol / L, the molar concentration of hydrochloric acid is 2.0 mol / L, the concentration of nitric acid is 2.0 mol / L, the concentration of sulfuric acid is 1.5 mol / L, the solid-liquid mass-volume ratio of acid leaching is 1:4 kg / L, the acid leaching temperature is 100℃, and the acid leaching time is 480 min.

[0081] 7) Washing and drying: The quartz acid leaching concentrate obtained in step 6) is washed with deionized water until the pH returns to neutral. The washed quartz ore particles are then placed in an oven for electric heating and drying.

[0082] 8) Calcination: Thoroughly mix the dried quartz acid-leached concentrate from step 7) with borax (sodium tetraborate pentahydrate), with a quartz to borax mass ratio of 6:1. Pour the mixture into a quartz boat and place it in a tube furnace for calcination at 850℃ for 3 hours to obtain the calcined product, such as... Figure 2 As shown in the lower middle figure.

[0083] 9) The roasted product is crushed and sanded. The quartz blocks are crushed with a mortar and pestle, and then ground with a rod mill lined with zirconium oxide for 20 seconds.

[0084] 10) Screening: Use a 70-mesh vibrating screen for screening. Collect the material under the 70-mesh screen as concentrate and collect the product over the 70-mesh screen and grind it again to finally obtain quartz ore particles smaller than 70 mesh.

[0085] 11) Heating and stirring with dilute hydrochloric acid: Pour the crushed quartz particles from step 10) into a 5% dilute hydrochloric acid solution. The solid-liquid mass-to-volume ratio of the quartz particles to the dilute hydrochloric acid solution is 1:2 kg / L. Heat the solution to boiling using a hot plate and stir continuously for 30 minutes. Then, pour off the supernatant and add 100℃ hot water. Repeat this process twice to obtain quartz concentrate. The process is as follows: Figure 3 As shown, the microstructure of quartz concentrate is as follows: Figure 5 As shown.

[0086] 12) Hot-press acid leaching: The quartz concentrate obtained in step 11) is subjected to mixed acid leaching, wherein the molar concentration of hydrofluoric acid is 1.5 mol / L, the molar concentration of hydrochloric acid is 3 mol / L, the concentration of nitric acid is 3 mol / L, the solid-liquid ratio of acid leaching is 1:2, the acid leaching temperature is 200℃, the acid leaching time is 360 min, and the equipment used is a static hydrothermal reactor.

[0087] 13) Filtration, washing, and drying: The acid leaching product obtained in step 12) is filtered using a filter press equipped with a rinsing device, and the filter residue is washed with deionized water. The washing endpoint is when the pH of the filtrate after washing is 6.5-7.0. After filtration, the quartz concentrate is dried using one or two methods: sun-drying, electric heating drying, or vacuum drying. The drying endpoint is when the moisture content of the quartz concentrate after filtration is less than 0.1%. The microstructure of the prepared high-purity quartz sand is as follows: Figure 7 As shown.

[0088] 14) Testing: The prepared quartz sand was ground to below 200 mesh using an agate mortar and pestle for XRD phase composition analysis. X-ray diffraction was performed using an X'pert Pro X-ray diffractometer manufactured by Panaco GmbH, Netherlands. Test conditions: Cu target, tube voltage 40kV, tube current 40mA, emission slit (DS): (1 / 2)°, anti-scattering slit (SS): 0.04 rad; receiving slit (AAS): 5.5mm; scan step: 0.02°; scan range: 3°~80°, continuous scanning. The XRD test data were refined, the cell volume was calculated, and the lattice impurity content was evaluated. The test results were fitted using X'pert HighScore Plus software, with the fitting referenced to the theoretical value of α-quartz (Reference code: 00-046-1045) in the Cell + zero shift mode. The relevant fitting results are shown in Table 3.

[0089] Table 3. Results of XRD cell parameter fitting calculation after sample purification.

[0090] Samples were sent to the National Silicon Inspection Center for testing. Each sample weighed 10g. The testing and judgment were based on JY / T 0567-2020, "General Rules for Inductively Coupled Plasma Emission Spectrometry Analysis." The test results are shown in Table 4. The total impurity content of the prepared high-purity quartz was 45.13 ppm, and the quartz cell parameter was 112.87 Å. 3 The amount of impurities is reduced compared to Q-1-1, demonstrating a significant effect on the removal of lattice impurities.

[0091] Table 4. ICP test results of the final purified product of the concentrate obtained by the high-purity quartz preparation process of sample Q-1 in this application.

[0092] Example 3 This example demonstrates the preparation of high-purity quartz using a calcination method described in this invention to remove impurities from the quartz lattice. The preparation method includes the following steps: 1) The quartz ore was ground using a rod mill with a zirconium oxide lining, and the grinding time was 90 seconds.

[0093] 2) Screening: 70-mesh and 150-mesh vibrating screens are used for screening. The products under the 70-mesh screen and over the 150-mesh screen are collected as concentrate. The products over the 70-mesh screen are collected and ground again to finally obtain quartz ore particles of -70 to +150 mesh.

[0094] 3) Scrubbing: The sieved product is scrubbed to remove mud. The scrubbing solution is a 5% oxalic acid solution, and the scrubbing method is mechanical scrubbing.

[0095] 4) Magnetic separation: The quartz ore particles after scrubbing and desliming are subjected to wet magnetic separation, wherein the slurry concentration of the wet magnetic separation is 40% and the magnetic field strength of the wet magnetic separation is 1.5T.

[0096] 5) Acid reverse flotation: Quartz ore particles of -70 to +150 mesh are subjected to flotation. The flotation conditions are as follows: the pH of the pulp is adjusted to 2.5 with hydrofluoric acid, dodecylamine is used as the collector, the pulp concentration is 20%, and the dodecylamine concentration is 150 g / t. Quartz flotation concentrate is obtained.

[0097] 6) Acid leaching: The quartz flotation concentrate obtained in step 5) is subjected to acid leaching with a mixed acid solution, wherein the molar concentration of hydrofluoric acid is 1.8 mol / L, the molar concentration of hydrochloric acid is 3.0 mol / L, the concentration of nitric acid is 3.5 mol / L, the concentration of sulfuric acid is 1.8 mol / L, the solid-liquid mass-volume ratio is 1:3 kg / L, the acid leaching temperature is 80℃, and the acid leaching time is 600 min.

[0098] 7) Washing and drying: The quartz acid leaching concentrate obtained in step 6) is washed with deionized water until the pH returns to neutral. The washed quartz ore particles are then placed in an oven for electric heating and drying.

[0099] 8) Calcination: The dried quartz acid-leached concentrate from step 7) is thoroughly mixed with borax, which is sodium tetraborate pentahydrate. The mass ratio of quartz to borax is 9:1. The mixture is poured into a quartz boat and placed in a tube furnace for calcination. The calcination temperature is 800℃ and the calcination time is 3 hours to obtain the calcined product.

[0100] 9) The roasted product is crushed and sanded. The quartz blocks are crushed with a mortar and pestle, and then ground with a rod mill lined with zirconium oxide for 20 seconds.

[0101] 10) Screening: Use a 70-mesh vibrating screen for screening. Collect the material under the 70-mesh screen as concentrate and collect the product over the 70-mesh screen and grind it again to finally obtain quartz ore particles smaller than 70 mesh.

[0102] 11) Heating and stirring with dilute hydrochloric acid: Pour the crushed quartz particles from step 10) into an 8% dilute hydrochloric acid solution. The solid-liquid mass-volume ratio of the quartz particles to the dilute hydrochloric acid solution is 1:5 kg / L. Heat the solution to boiling using a hot plate and stir continuously for 30 minutes with a stir bar. Then pour off the upper layer of liquid and add 100℃ hot water. Repeat this process twice.

[0103] 12) Hot-press acid leaching: The quartz concentrate obtained in step 11) is subjected to mixed acid leaching, wherein the molar concentration of hydrofluoric acid is 1.5 mol / L, the molar concentration of hydrochloric acid is 3 mol / L, the concentration of nitric acid is 3 mol / L, the solid-liquid ratio of acid leaching is 1:2, the acid leaching temperature is 200℃, the acid leaching time is 360 min, and the equipment used is a static hydrothermal reactor.

[0104] 13) Filtration, washing and drying: The acid leaching product obtained in step 12) is filtered using a filter press with a rinsing device and the filter residue is washed with deionized water. The washing endpoint is when the pH of the filtrate after washing is 6.5~7.0. After filtration, the quartz concentrate is dried by one or two of the following methods: sun drying, electric heating drying and vacuum drying. The drying endpoint is when the moisture content of the quartz concentrate after filtration is less than 0.1%.

[0105] 14) Testing: The prepared quartz sand was ground to below 200 mesh using an agate mortar and pestle for XRD phase composition analysis. X-ray diffraction was performed using an X'pert Pro X-ray diffractometer manufactured by Panaco GmbH, Netherlands. Test conditions: Cu target, tube voltage 40kV, tube current 40mA, emission slit (DS): (1 / 2)°, anti-scattering slit (SS): 0.04 rad; receiving slit (AAS): 5.5mm; scan step: 0.02°; scan range: 3°~80°, continuous scanning. The XRD test data were refined, the cell volume was calculated, and the lattice impurity content was evaluated. The test results were fitted using X'Pert HighScore Plus software, with the fitting referenced to the theoretical value of α-quartz in PDF card number Reference code: 00-046-1045. The fitting mode was Cell + zero shift mode, and the relevant fitting results are shown in Table 5.

[0106] Table 5. Results of XRD cell parameter fitting calculation after sample purification.

[0107] Samples were sent to the National Silicon Inspection Center for testing. Each sample weighed 10g. The testing and judgment were based on JY / T 0567-2020, "General Rules for Inductively Coupled Plasma Emission Spectrometry Analysis." The test results are shown in Table 6. The total impurity content of the prepared high-purity quartz was 32.70 ppm, and the quartz cell parameter was 112.95 Å. 3 The amount of impurities is reduced compared to Q-1-1, demonstrating a significant effect on the removal of lattice impurities.

[0108] Table 6. ICP test results of the final purified product of the concentrate obtained by the high-purity quartz preparation process of sample Q-1 in this application.

[0109] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing high-purity quartz by removing quartz lattice impurities through calcination, characterized in that, The method includes the following steps: 1) Pre-treat the quartz ore to obtain coarse quartz particles; 2) The coarse quartz particles are mixed with borax and then calcined to obtain the calcined quartz product; 3) The quartz roasting product is crushed and sanded, then reacted with dilute hydrochloric acid solution. After the reaction is completed, it is filtered to obtain refined quartz particles. 4) The refined quartz particles are placed in a reaction vessel and subjected to hot-press acid leaching with a mixed acid solution. After post-treatment, high-purity quartz is obtained.

2. The method for preparing high-purity quartz by removing quartz lattice impurities by calcination according to claim 1, characterized in that, The quartz ore mentioned in step 1) is a low-quality quartz raw material containing lattice impurities or inclusions inside the quartz, including one of natural crystal, granite pegmatite, vein quartz and quartzite; the pretreatment includes crushing-sand making, scrubbing, magnetic separation, flotation, acid leaching, water washing and drying; The coarse quartz particles have a particle size of -70 to +150 mesh and a SiO2 mass percentage content of ≥99.9%.

3. The method for preparing high-purity quartz by removing quartz lattice impurities through calcination according to claim 2, characterized in that, The crushing-sand making refers to a crushing-grinding process with inspection screening and grading screening; the scrubbing includes one or both of mechanical scrubbing and ultrasonic scrubbing, and the slurry ratio during scrubbing is 1:3~1:8 kg / L of solid-liquid mass volume ratio of quartz particles after grinding to scrubbing medium, and the scrubbing time is 10min~60min; the magnetic separation is carried out using one or both of superconducting magnetic separator, high gradient vertical ring magnetic separator and wet high intensity magnetic separator, the magnetic field strength of the magnetic separation is 1.3~2.3T, and the magnetic separation needs to be circulated 3~6 times.

4. The method for preparing high-purity quartz by removing quartz lattice impurities by calcination according to claim 2, characterized in that, The flotation is reverse flotation. The pulp mass concentration during the flotation is 10-30%, and the pH of the pulp is 1.5-3.

5. The pH is adjusted by hydrofluoric acid or dilute sulfuric acid. Dodecylamine is used as the collector in the flotation. The amount of dodecylamine added is 100-200g per ton of quartz particles. The flotation foam products include feldspar and mica, and the bottom product is quartz particles.

5. The method for preparing high-purity quartz by removing quartz lattice impurities by calcination according to claim 2, characterized in that, The acid leaching is carried out using a mixed acid solution, wherein the molar concentration of hydrofluoric acid is 0.2~2.0 mol / L, the molar concentration of hydrochloric acid is 1.2~3.2 mol / L, the molar concentration of nitric acid is 1.6~4.8 mol / L, and the molar concentration of sulfuric acid is 0.5~2.0 mol / L; the solid-liquid mass-to-volume ratio of quartz particles to the mixed acid solution during the acid leaching is 1:2~1:5 kg / L; the acid leaching temperature is 80~120℃, and the time is 360~600 min; The water washing refers to washing the quartz particles after acid leaching with deionized water, and the washing endpoint is when the pH of the filtrate after washing is 6.5~7.0; the drying includes one or two of sun drying, electric heating drying and vacuum drying.

6. The method for preparing high-purity quartz by removing quartz lattice impurities by calcination according to claim 1, characterized in that, The borax mentioned in step 2) is sodium tetraborate pentahydrate or sodium tetraborate decahydrate, and the particle size of the borax is -120~+200 mesh; the roasting step includes: weighing and mixing the coarse quartz particles and the borax, mixing the proportioned coarse quartz particles and the borax thoroughly, and roasting after thorough mixing to obtain the quartz roasting product; The mass ratio of the coarse quartz particles to the borax is 6:1 to 10:1; the mixing is carried out using a mixer, drum mixer, or dynamic reactor at a speed of 20 to 40 r / min for 3 to 10 min; the calcination is carried out in a calcination furnace, which includes one of an atmosphere sintering furnace, a tube furnace, a rotary kiln, and a suspension furnace; the calcination temperature is 750 to 850℃ for 1 to 3 h; and the calcined quartz product is a porous, brittle quartz block coated with borosilicate glass.

7. The method for preparing high-purity quartz by removing quartz lattice impurities by calcination according to claim 1, characterized in that, The crushing-sand making process mentioned in step 3) refers to a crushing-grinding process with inspection screening and grading screening. The particle size of the quartz particles after crushing-grinding is -70 to +150 mesh. The solid-liquid mass-volume ratio of the quartz particles after crushing-sand making to the dilute hydrochloric acid solution is 1:2 to 1:5 kg / L, and the mass concentration of the dilute hydrochloric acid solution is 4% to 10%. The reaction described in step 3) includes thorough stirring, heating and dissolution. The thorough stirring time is ≥30 min, the heating temperature is ≥95℃, and the purpose of dissolution is to dissolve the borosilicate glass coated on the surface of the quartz particles in the dilute hydrochloric acid solution.

8. The method for preparing high-purity quartz by removing quartz lattice impurities by calcination according to claim 1, characterized in that, The equipment used for hot-press acid leaching in step 4) is either a dynamic hot-press acid leaching reactor or a static hydrothermal reactor; the molar concentration of hydrofluoric acid in the mixed acid solution is 0.5~1.5 mol / L, the molar concentration of hydrochloric acid is 0.8~3.2 mol / L, and the molar concentration of nitric acid is 1.2~3.4 mol / L. During the hot-press acid leaching process, the solid-liquid mass-volume ratio of the refined quartz particles to the mixed acid solution is 1:2~1:5 kg / L, the acid leaching temperature is 150~200℃, and the time is 300~600 min.

9. The method for preparing high-purity quartz by removing quartz lattice impurities by calcination according to claim 1, characterized in that, The post-treatment described in step 4) includes filtering, washing, and drying the acid-leaching product after hot-pressing and acid leaching. The filtering and washing process involves using a filter press with a rinsing device to filter the acid-leaching product and washing the filter residue with deionized water. The washing endpoint is when the pH of the filtrate is 6.5-7. The drying process involves drying the quartz particles after filtering and washing by air drying, electric heating, or vacuum drying. The drying endpoint is when the moisture content of the dried product is less than 0.1%.

10. A high-purity quartz, characterized in that, The high-purity quartz is prepared by a calcination method according to any one of claims 1-9 to remove quartz lattice impurities. The high-purity quartz has a SiO2 mass percentage content of 99.99%~99.999%, and the quartz unit cell parameter can be obtained from the theoretical standard value of 113.01 Å. 3 Reduced to 112.87 Å 3 .

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