High purity fused quartz sand and method for making same

Abstract

The application provides high-purity fused quartz sand and a preparation method thereof, and the preparation method comprises the following steps: pretreating waste quartz glass to obtain crude quartz glass sand with a particle size of greater than 0.18 mm; performing alkali leaching treatment on the crude quartz glass sand, and performing high-temperature calcination on the crude quartz glass sand after the alkali leaching treatment, so that impurities in the crude quartz glass sand migrate to the surface of the particles to obtain crude fused quartz sand; and performing acid leaching treatment on the crude fused quartz sand to obtain high-purity fused quartz sand. The application uses waste quartz glass as raw material, realizes recycling of the waste quartz glass, and is beneficial to solid waste treatment and saving of mineral resources.

Description

Technical Field

[0001] This invention belongs to the field of quartz preparation technology, specifically, it relates to a fused quartz glass sand and its preparation method. Background Technology

[0002] Quartz glass is made from raw quartz through processes such as crushing, washing, drying, hydrolysis, and synthesis. Quartz glass is typically produced using quartz sand with a SiO2 content higher than 95%. Lower-quality opaque quartz glass is often used in the production of quartz glass, while transparent quartz glass and higher-quality synthetic quartz glass are further processed into quartz fibers, tubes, rods, ingots, and other quartz products. However, during the manufacturing process, human error can lead to problems such as quartz glass breakage and the formation of bubbles. Furthermore, prolonged use can result in aging, discoloration, and mechanical breakage. The 95% SiO2 content in quartz glass waste represents a significant waste of resources. Globally, a large amount of quartz glass is used annually, generating substantial amounts of waste, but recycling seems increasingly rare, with large quantities of quartz glass being discarded in nature.

[0003] Fused silica is made by melting high-purity quartz at extremely high temperatures. It features high SiO2 content, low thermal conductivity, high insulation, and stable chemical properties. Therefore, it is commonly used in industries such as refractory materials, precision casting, semiconductor fillers, special coatings, ceramics, and mold making. Summary of the Invention

[0004] The purpose of this invention is to address at least one of the aforementioned shortcomings of the prior art. For example, one objective of this invention is to alleviate the over-mining of raw quartz ore and realize the recycling of quartz sand; another objective is to reduce the use of grinding media and save energy.

[0005] To achieve the above objectives, one aspect of the present invention provides a method for preparing fused silica glass sand. The preparation method may include the following steps: pretreating waste quartz glass to obtain coarse quartz glass sand with a particle size > 0.18 mm; subjecting the coarse quartz glass sand to alkali leaching treatment, and then subjecting the alkali-leached coarse quartz glass sand to high-temperature calcination to allow impurities in the coarse quartz glass sand to migrate to the particle surface, thereby obtaining coarse fused silica sand; and subjecting the coarse fused silica sand to acid leaching treatment to obtain refined fused silica sand.

[0006] The waste quartz glass mentioned above is quartz glass that has cracked and produced bubbles due to human error during the manufacturing process. It also suffers from aging, discoloration, and mechanical cracking during long-term use, and contains 95% SiO2.

[0007] In an exemplary embodiment of the present invention, waste quartz glass is crushed in two stages: the first stage crushes the waste quartz glass into particles of 10-20 mm; the second stage crushes the waste quartz glass into particles smaller than 10 mm; the waste quartz glass particles are washed and dried; the dried waste quartz glass particles are ground and sieved through a perforated sieve to obtain waste quartz glass particles with a particle size > 0.18 mm, and the resulting coarse quartz glass sand is obtained by wiping.

[0008] In an exemplary embodiment of the present invention, the grinding process may include dry or wet grinding, the grinding speed may be 200 to 500 r / min, and the time may be 1 to 20 min.

[0009] For example, the grinding speed can be 210, 320, 380, 457, or 482 r / min; the time can be 1, 5, 10, or 15 min.

[0010] In an exemplary embodiment of the present invention, the concentration of the alkaline solution used in the alkaline leaching treatment can be 0.1–3 mol / L, the alkaline leaching temperature can be 60–90°C, the alkaline leaching time can be 8–15 h, and the solid-liquid ratio of the coarse quartz glass sand to the alkaline solution can be (1–5):(5–25); the alkaline solution may include one or two of potassium hydroxide, sodium hydroxide, etc. Alkaline leaching can corrode certain pores on the surface of quartz particles and effectively remove some alkali metal impurities.

[0011] For example, the concentration of potassium hydroxide can be 0.1, 1, 2, or 3 mol / L, the alkaline leaching temperature can be 60, 70, 80, or 90℃, and the alkaline leaching time can be 8, 10, 12, or 15 hours.

[0012] In an exemplary embodiment of the present invention, the calcination temperature can be 900°C to 1200°C, and the time can be 1 to 6 hours. Calcination can activate impurity sites, causing impurities to accumulate and migrate to the vicinity of the corrosion cavities. It can also remove some suspended impurities.

[0013] For example, the calcination temperature can be 900, 1000, 1100, or 1200℃, and the calcination time can be 1, 3, 5, or 6 hours.

[0014] In an exemplary embodiment of the present invention, the acid leaching treatment may include placing the coarse fused silica sand in an acid-resistant reaction device equipped with heating and stirring functions and adding mixed acid. The solid-liquid ratio of the coarse fused silica sand to the mixed acid may be (1-5):(5-25). The treatment may be carried out in a water bath or oil bath at 60°C-90°C, with a stirring rate of 100-200 r / min, and the acid leaching time may be 8-20 h. Acid leaching can effectively remove metallic impurities.

[0015] For example, the stirring rate can be 110, 125, 136, 147, 175, 185, or 192 r / min, the acid leaching time can be 8, 10, 15, or 20 h, and the acid leaching temperature can be 60, 70, or 80 °C.

[0016] In an exemplary embodiment of the present invention, the preparation method may further include washing the fused silica sand until the pH of the filtrate is neutral, and drying it to obtain high-purity fused silica sand of different particle sizes with a SiO2 content greater than 98%.

[0017] In an exemplary embodiment of the present invention, the preparation method may further include sieving and grading, obtaining the following through a perforated sieve: first-grade fused silica sand with a particle size of 0.18–0.25 mm, used for the production of silicon compounds in the metallurgical raw materials, additives, and chemical industries; second-grade fused silica sand with a particle size of 0.25–0.83 mm, used as raw material for ceramics and refractory materials; and third-grade fused silica sand with a particle size greater than 0.83 mm, used for returning to the pretreatment stage.

[0018] Another aspect of the present invention provides a method for preparing high-purity fused silica sand.

[0019] The fused silica sand can be prepared by the method described above for preparing high-purity fused silica sand. The SiO2 content of the fused silica sand is greater than 98%, wherein the SiO2 content of 98-99% is low-end high-purity fused silica sand, 99-99.9% is mid-end high-purity fused silica sand, and greater than 99.9% is high-end high-purity fused silica sand; the particle size of the high-purity fused silica sand is 0.18-0.83 mm.

[0020] Compared with the prior art, the beneficial technical effects of the present invention include:

[0021] (1) This invention uses waste quartz glass as raw material, which is different from the traditional method of preparing fused quartz sand using quartz ore. It can realize the resource utilization of solid waste and alleviate the current situation of being "strangled" by high-purity quartz raw materials.

[0022] (2) This invention uses waste quartz glass as raw material, eliminating the pre-treatment step of raw ore in the method of preparing high-purity fused quartz sand from quartz ore, thereby improving the economic efficiency of enterprise production and saving production costs.

[0023] (3) This invention makes comprehensive use of waste quartz glass, so that the utilization rate of waste quartz glass reaches more than 95%, and at the same time, it can produce fused quartz sand of different particle sizes to meet the needs of different industries. Attached Figure Description

[0024] Figure 1The XRD pattern of high-purity fused silica sand, an exemplary embodiment of the present invention, is shown.

[0025] Explanation of reference numerals in the attached figures:

[0026] A01 - Fused Quartz. Detailed Implementation

[0027] In the following, a high-purity fused silica sand and its preparation method according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0028] It should be noted that "first," "second," and "third" are used merely for the purpose of distinction and description, and do not indicate or imply importance or order.

[0029] First exemplary embodiment

[0030] In a first exemplary embodiment of the present invention, a method for preparing high-purity fused silica sand is provided. In this exemplary embodiment, the waste silica glass is silica glass discarded due to crystallization, cracking, and stress damage, and its SiO2 purity is above 95%.

[0031] The preparation method includes the following steps:

[0032] Step 1: Pre-treat the waste quartz glass to obtain coarse quartz glass sand with a particle size > 0.18 mm.

[0033] Specifically, the pretreatment steps may include two-stage crushing of the waste quartz glass: the first stage crushing breaks the waste quartz glass into particles of 10-20 mm; the second stage crushing breaks the waste quartz glass into particles smaller than 10 mm. When crushing the waste quartz glass, a zirconia-lined jaw crusher can be used to crush it into glass particles of 1-2 cm. Optionally, a hammer crusher, a double-roll crusher, etc., can also be used.

[0034] Step 2: Clean and dry the waste quartz glass particles.

[0035] Specifically, the waste quartz glass particles are rinsed with clean water to remove surface dust or suspended impurities, and then dried and ground.

[0036] The dried waste quartz glass particles are ground. The grinding mill used in this process employs one or more of the following grinding media: zirconium oxide or agate, such as zirconium oxide balls or agate balls. The particles are then sieved through a perforated sieve to obtain waste quartz glass particles with a diameter > 0.18 mm, and the resulting coarse quartz glass sand is obtained by washing.

[0037] Specifically, the grinding process can be either dry or wet.

[0038] Grinding is an option. Waste quartz glass is placed in a mixing tank, and centrifugal force is used. The grinding media, such as zirconia or agate balls, are used as the lining and grinding media. This causes the abrasive media to collide with the coarse quartz glass sand particles, resulting in coarse fused quartz glass sand that is then sieved. The mixing tank speed can be set to 200–500 r / min, and the grinding time can be 1–15 min. Alternatively, other equipment with mixing and rotation functions can be used instead of the mixing tank.

[0039] For example, the grinding speed can be 210, 320, 380, 457, or 482 r / min; the time can be 1, 5, 10, or 15 min.

[0040] When wet grinding is used, waste quartz glass is placed in a mixing tank. Centrifugal force is utilized, and the grinding media, such as zirconia or agate (e.g., zirconia balls or agate balls), collide with the coarse quartz glass sand particles, resulting in coarse fused quartz glass sand obtained through sieving. The grinding speed can be set to 200–500 r / min, and the grinding time can be 10–20 min. Optionally, the mixing tank can be replaced with other equipment that has stirring and rotation functions.

[0041] For example, the wet grinding speed can be 210, 320, 380, 457, or 482 r / min; the time can be 10, 15, or 20 min.

[0042] Step 3: The coarse quartz glass sand is subjected to alkali leaching treatment, and the alkali-leached coarse quartz glass sand is then calcined at high temperature to allow impurities in the coarse quartz glass sand to migrate to the particle surface, thereby obtaining coarse fused quartz sand.

[0043] Specifically, potassium hydroxide can be used as the alkali solution, with a purity of superior grade and a concentration of 0.1–3 mol / L. The alkali leaching temperature can be 60–90℃, and the alkali leaching time can be 8–15 h. The solid-liquid ratio of the crude quartz glass sand to the alkali solution can be (1–5):(5–25). The alkali solution may include one or two of potassium hydroxide, sodium hydroxide, etc.

[0044] Specifically, for high-temperature calcination, the coarse quartz glass sand can be placed in a high-temperature furnace at a temperature of 900℃ to 1200℃ for a holding time of 1 to 6 hours. Alternatively, molten quartz can be placed in a high-temperature furnace at a conversion temperature of 900℃ to 1200℃.

[0045] For example, the concentration of potassium hydroxide can be 0.1, 1, 2, or 3 mol / L, the alkaline leaching temperature can be 60, 70, 80, or 90℃, the alkaline leaching time can be 8, 10, 12, or 15 h, the calcination temperature can be 900, 1000, 1100, or 1200℃, and the calcination time can be 1, 3, 5, or 6 h.

[0046] Step 4: Acid leaching is performed on the coarse fused silica sand to obtain refined fused silica sand.

[0047] Specifically, the acid leaching treatment may include placing the coarse fused silica sand in an acid-resistant reaction device with heating and stirring functions and adding mixed acid. The solid-liquid ratio of the coarse fused silica sand to the mixed acid may be (1-5):(5-25). The acid leaching treatment may be carried out at 60℃-90℃, the stirring rate may be 100-200 r / min, and the acid leaching treatment time may be 8-20 h.

[0048] For example, the stirring rate can be 110, 125, 136, 147, 175, 185, or 192 r / min, the soaking time can be 8, 10, 15, or 20 h, and the heating temperature can be 60, 70, or 80 °C.

[0049] Optionally, the preparation method may further include drying the obtained high-purity fused silica glass filter cake and classifying it to obtain high-purity fused silica glass sand with different particle sizes and SiO2 content greater than 98%, wherein the SiO2 content of 98-99% is low-end high-purity fused silica sand, 99-99.9% is mid-end high-purity fused silica sand, and greater than 99.9% is high-end high-purity fused silica sand.

[0050] Specifically, the high-purity fused silica glass filter cake can be washed until the pH of the filtrate is neutral, and then dried to obtain fused silica sand with a SiO2 content greater than 98%. Among them, the SiO2 content of 98-99% is low-end high-purity fused silica sand, 99-99.9% is mid-end high-purity fused silica sand, and greater than 99.9% is high-end high-purity fused silica sand.

[0051] Different particle sizes of fused silica glass sand are obtained by sieving and classifying the sand through a perforated sieve.

[0052] Fused silica sand with a particle size of 0.18–0.25 mm is classified as Grade 1 and is used for the production of silicon compounds in the metallurgical raw materials, additives, and chemical industries.

[0053] The second grade is fused silica sand with a particle size of 0.25–0.83 mm, which is used as raw material for ceramics and refractory materials.

[0054] Fused silica sand with a particle size greater than 0.83 mm is classified as the third stage and returned to the pretreatment stage.

[0055] Another aspect of the present invention provides a method for preparing high-purity fused silica sand.

[0056] The fused silica sand can be prepared by the fused silica sand preparation method described above, wherein the SiO2 content of the fused silica sand is greater than 98%; wherein the SiO2 content of 98-99% is low-end high-purity fused silica sand, 99-99.9% is mid-end high-purity fused silica sand, and greater than 99.9% is high-end high-purity fused silica sand, and the particle size of the high-purity fused silica sand is 0.18-0.83 mm.

[0057] Second exemplary embodiment

[0058] In a second exemplary embodiment of the present invention, fused silica sand is provided, characterized in that the fused silica sand is prepared by the fused silica sand preparation method described above, the SiO2 content of the fused silica sand is greater than 98%, and the particle size of the fused silica glass sand particles is 0.18 to 0.83 mm.

[0059] Figure 1 The XRD pattern of fused silica sand according to this exemplary embodiment is shown. In the figure, the horizontal axis represents the 2θ angle, which is used to scan the entire diffraction region at an angle of 2θ; the vertical axis represents the diffraction peak intensity; A01 represents fused silica.

[0060] XRD patterns show that the fused silica sand in this example exhibits an amorphous phase. Analysis reveals that the impurity content of the fused silica sand obtained from waste silica glass decreases with increasing reaction temperature. Therefore, appropriately increasing the reaction temperature is beneficial for removing impurities from waste silica glass; however, higher temperatures also increase energy consumption.

[0061] To better understand the exemplary embodiments of the present invention described above, a high-purity fused silica sand and its preparation method will be described below with reference to specific examples.

[0062] Example 1

[0063] The waste quartz glass selected in this example has the following main impurity element content as shown in Table 1. The unit of element content in the table is ×10⁻¹⁰. -6 The SiO2 content is expressed as a percentage by mass (%).

[0064] Table 1. Impurity element content of waste quartz glass (Example 1)

[0065] Fused Quartz 124.7 62.4 5.77 3 25.8 8.5 18.3 94.85

[0066] Specifically, the following steps are included:

[0067] (1) First, the waste quartz glass is placed in a hammer crusher to crush most of the waste quartz glass to 10-20mm. Then, it is further crushed by a double roll crusher to obtain waste quartz glass sand with a particle size >0.38mm. It is then rinsed with water and dried.

[0068] (2) Dry grinding of waste quartz glass sand: 1000g of waste quartz sand is placed in a mixing tank, the rotation speed is set to 200r / min, the grinding time is 5min, and after the grinding time is completed, it is removed by passing it through a square or round hole sieve with a diameter of 0.18mm and the fine quartz glass powder that is peeled off and ground during the grinding process. The material on the sieve is 950g of quartz glass sand.

[0069] (3) Place 930g of crude fused silica glass sand in a polytetrafluoroethylene stirring tank, add 5000ml of 0.1mol / L potassium hydroxide solution, alkali leaching treatment temperature 60℃, alkali leaching treatment time 10h, and wash it after alkali leaching treatment. Ultrapure water or deionized water can be used for washing. Wash until the filtrate is neutral to obtain crude silica glass sand.

[0070] (4) Put the coarse quartz glass sand into the gold melting cup and put it into the high temperature furnace for high temperature treatment. Heat it to 900℃, keep it at the temperature for 1 hour, and take it out after it cools down naturally.

[0071] (5) Prepare a mixed acid and perform acid leaching treatment on the coarse quartz sand. The coarse quartz glass sand is acid-leached by adding the mixed acid at a solid-liquid ratio of 1:5, and heating and stirring in a stirring tank at 60℃ for 500 minutes to obtain refined fused quartz sand. The mixed acid is formulated as follows: 2000 ml each of 0.5 mol / L oxalic acid solution and 0.5 mol / L acetic acid solution are mixed evenly with 1000 ml of deionized water.

[0072] (6) Filter the acid-treated sample and wash it until the filtrate is neutral. Ultrapure water or deionized water can be used for washing.

[0073] The samples were dried in a drying oven to obtain fused silica with a SiO2 content of 98.31% in different particle sizes. This is considered low-end high-purity fused silica sand, and its impurity element content is shown in Table 2. The unit for impurity element content in the table is ×10⁻¹⁰. -6 The SiO2 content is expressed as a percentage by mass (%).

[0074] Table 2 Impurity element content of high-purity fused silica

[0075] Fused Quartz 115.8 58.4 2.79 3.87 21.4 8.03 16.9 98.31

[0076] Example 2

[0077] The main impurity element contents of the waste quartz glass selected in this example are shown in Table 3, where the unit of impurity element content is ×10. -6 The SiO2 content is expressed as a percentage by mass (%).

[0078] Table 3 Example 2 Impurity Element Content of Waste Quartz Glass

[0079] Fused Quartz 124.7 62.4 5.77 3 25.8 8.5 18.3 94.85

[0080] (1) First, the waste quartz glass is placed in a hammer crusher to crush most of the waste quartz glass to 10-20mm. Then, it is further crushed by a double roll crusher and passed through a square or round hole sieve with a diameter of 0.38mm to obtain waste quartz glass sand with a particle size >0.38mm. It is then rinsed with ultrapure water and dried.

[0081] (2) Dry grinding of waste quartz glass sand: 1000g of waste quartz glass sand is placed in a mixing tank, the rotation speed is set to 300r / min, the grinding time is 4min, and after the grinding time is completed, it is passed through a square or round hole sieve with a diameter of 0.18mm, and the material on the sieve is 970g of quartz glass sand.

[0082] (3) Place the fused silica glass sand in an ultrasonic cleaner, prepare the cleaning solution, add 200g of oxalic acid and 2000ml of water. The amount of cleaning solution added is 4.5 times the mass of the silica glass sand. The cleaning time is 15min and the ultrasonic power is 20kHz. After ultrasonic cleaning, let it pass through a square or round hole sieve with a diameter of 0.18mm. Take 960g of coarse fused silica glass sand from the sieve.

[0083] (4) 930g of crude fused silica glass sand was placed in a polytetrafluoroethylene stirring tank, and 5000ml of 0.5mol / L potassium hydroxide solution was added. The alkaline leaching treatment temperature was 70℃ and the alkaline leaching treatment time was 10h. After the alkaline leaching treatment, it was washed with ultrapure water and filtered until the filtrate was neutral to obtain crude fused silica glass sand.

[0084] (5) Put the coarse quartz glass sand into the gold melting cup and put it into the high temperature furnace for high temperature treatment. Heat it to 1000℃, keep it at the temperature for 1 hour, and take it out after it cools down naturally.

[0085] (6) The coarse quartz glass sand is acid-leached. The mixed acid is added at a solid-liquid ratio of 1:5 and heated and stirred in a stirring tank at 70°C for 8 hours to obtain refined fused quartz sand. The formula of the mixed acid is: 2000 ml each of 0.5 mol / L oxalic acid solution and 1 mol / L acetic acid solution are mixed evenly with 1000 ml of deionized water.

[0086] The acid-leached sample was filtered and washed with ultrapure water until the filtrate was neutral. The sample was then dried in a drying oven to obtain high-purity fused silica with a SiO2 content of 99.15%, classified as mid-range high-purity fused silica sand. The impurity element content is shown in Table 4, where the unit of impurity element content is ×10⁻¹⁰. -6 The SiO2 content is expressed as a percentage by mass (%).

[0087] Table 4. Impurity element content of high-purity fused silica

[0088] Fused Quartz 106.7 37.4 0.67 2.17 16.4 7.53 16.9 99.15

[0089] Example 3

[0090] The main impurity element contents of the waste quartz glass selected in this example are shown in Table 5, where the unit of impurity element content is ×10. -6 The SiO2 content is expressed as a percentage by mass (%).

[0091] Table 5. Impurity element content of waste quartz glass

[0092] Fused Quartz 124.7 62.4 5.77 3 25.8 8.5 18.3 94.85

[0093] (1) First, the waste quartz glass is placed in a hammer crusher to crush most of the waste quartz glass to 10-20mm. Then, it is further crushed by a double roll crusher and passed through a square or round hole sieve with a diameter of 0.38mm to obtain waste quartz glass sand with a particle size >0.38mm. It is then rinsed with ultrapure water and dried.

[0094] (2) Dry grinding of waste quartz glass sand: 1000g of waste quartz glass sand is placed in a mixing tank, the rotation speed is set to 400r / min, the grinding time is 3min, and after the grinding time is completed, it is passed through a square or round hole sieve with a diameter of 0.18mm, and the material on the sieve is 985g of quartz glass sand.

[0095] (3) 980g of crude fused silica glass sand was placed in a polytetrafluoroethylene stirring tank, 5000ml of 1mol / L potassium hydroxide solution was added, the alkaline leaching temperature was 80℃, the alkaline leaching time was 8h, and after the alkaline leaching treatment, it was washed with ultrapure water and filtered until the filtrate was neutral to obtain crude fused silica glass sand.

[0096] (4) Put the coarse quartz glass sand into the gold melting cup and put it into the high temperature furnace for high temperature treatment. Heat it to 1000℃, keep it at the temperature for 4 hours, and take it out after it cools down naturally.

[0097] (5) The coarse quartz glass sand is acid-leached. The mixed acid is added at a solid-liquid ratio of 1:5 and heated and stirred in a stirring tank at 70°C for 8 hours to obtain refined fused quartz sand. The formula of the mixed acid is: 1000 ml each of 1 mol / L oxalic acid solution and 2 mol / L acetic acid solution are mixed evenly with 3000 ml of deionized water.

[0098] The acid-leached samples were filtered and washed with ultrapure water until the filtrate was neutral. The samples were then dried in a drying oven to obtain high-purity fused silica with a SiO2 content of 99.94% in different particle sizes. This is high-end, high-purity fused silica sand. The impurity element content is shown in Table 6. The unit for impurity element content is ×10⁻¹⁰. -6 The SiO2 content is expressed as a percentage by mass (%).

[0099] Table 6. Impurity element content of fused silica

[0100] Fused Quartz 90.7 45.3 1.58 1.67 15.4 5.82 13.5 99.94

[0101] Example 4

[0102] The main impurity element contents of the waste quartz glass selected in this example are shown in Table 7. The unit for impurity element content is ×10⁻¹⁰. -6 The SiO2 content is expressed as a percentage by mass (%).

[0103] Table 7 Example 4 Impurity Element Content of Waste Quartz Glass

[0104] Fused Quartz 124.7 62.4 5.77 3 25.8 8.5 18.3 94.85

[0105] (1) First, the waste quartz glass is placed in a hammer crusher to crush most of the waste quartz glass to 10-20mm. Then, it is further crushed by a double roll crusher and passed through a square or round hole sieve with a diameter of 0.38mm to obtain waste quartz glass sand with a particle size >0.38mm. It is then rinsed with ultrapure water and dried.

[0106] (2) Dry grinding of waste quartz glass sand: 1000g of waste quartz glass sand is placed in a mixing tank, the rotation speed is set to 400r / min, the grinding time is 3min, and after the grinding time is completed, it is passed through a square or round hole sieve with a diameter of 0.18mm, and the material on the sieve is 985g of quartz glass sand.

[0107] (3) 990g of crude fused silica glass sand was placed in a polytetrafluoroethylene stirring tank, 5000ml of 2mol / L potassium hydroxide solution was added, the alkaline leaching treatment temperature was 90℃, the alkaline leaching treatment time was 10h, and after the alkaline leaching treatment, it was washed with ultrapure water and filtered until the filtrate was neutral to obtain crude fused silica glass sand.

[0108] (4) Put the coarse quartz glass sand into the gold melting cup and put it into the high temperature furnace for high temperature treatment. Heat it to 1200℃, keep it at the temperature for 5 hours, and take it out after it cools down naturally.

[0109] (5) The coarse quartz glass sand is acid-leached. The mixed acid is added at a solid-liquid ratio of 1:5 and heated and stirred in a stirring tank at 70°C for 10 hours to obtain refined fused quartz sand. The formula of the mixed acid is: 1000 ml each of 1 mol / L oxalic acid solution and 2 mol / L acetic acid solution are mixed evenly with 3000 ml of deionized water.

[0110] The acid-leached samples were filtered and washed with ultrapure water until the filtrate was neutral. The samples were then dried in a drying oven to obtain high-purity fused silica with a SiO2 content of 99.97% in different particle sizes. This is high-end, high-purity fused silica sand. The impurity element content is shown in Table 8. The unit for impurity element content is ×10⁻¹⁰. -6 The SiO2 content is expressed as a percentage by mass (%).

[0111] Table 8. Impurity element content of high-purity fused silica

[0112] Fused Quartz 90.7 45.3 0.58 0.67 15.4 5.82 13.5 99.97

[0113] In summary, this invention utilizes waste quartz glass to prepare high-purity fused silica, producing high-purity fused silica glass sand and SiO2 with a purity of 98%. This not only enables the resource utilization of waste quartz glass, saving space and protecting the environment, but also offers a simple operating procedure.

[0114] This invention is a short-process, high-efficiency, and low-cost method for preparing high-purity fused silica from waste quartz glass. It has the advantages of high crystal phase transformation, low environmental pollution, and high product quality, which alleviates the environmental pollution and space pressure caused by waste quartz glass and has profound significance for the research on the preparation of high-purity fused silica sand.

[0115] Although the invention has been described above in conjunction with exemplary embodiments, those skilled in the art will understand that various modifications and changes can be made to the exemplary embodiments of the invention without departing from the spirit and scope defined by the claims.

Claims

1. A method for preparing high-purity fused silica sand, characterized in that, The preparation method includes the following steps: Waste quartz glass is pretreated to obtain coarse quartz glass sand with a particle size > 0.18 mm; The coarse quartz glass sand is subjected to alkali leaching treatment, and the alkali-leached coarse quartz glass sand is then calcined at high temperature to allow impurities in the coarse quartz glass sand to migrate to the particle surface, thereby obtaining coarse fused quartz sand. Acid leaching of coarse fused silica sand yields high-purity fused silica sand of mixed particle size; and The mixed-size fused silica sand is classified to obtain high-purity fused silica sand of different sizes; in, The waste quartz glass contains ≥95% SiO2; The alkali used in the alkaline leaching treatment includes one or two of potassium hydroxide and sodium hydroxide. The acids used in the acid leaching treatment are organic acids, including oxalic acid and glacial acetic acid; The calcination involves placing the quartz glass particles, which have been alkali-impregnated and dried, into a high-temperature calcination device and calcining them at a temperature of 1000℃~1200℃ for 1~6 hours. The fused silica sand of mixed particle size is classified into three particle sizes: greater than or equal to 0.18 mm and less than or equal to 0.25 mm, greater than 0.25 mm and less than or equal to 0.83 mm, and greater than 0.83 mm; the fused silica sand is an amorphous phase. The concentration of the alkali aqueous solution used in the alkali leaching treatment is 0.1~3mol / L, the alkali leaching treatment temperature is 80~90℃, the alkali leaching treatment time is 8~15h, and the solid-liquid ratio of the coarse quartz glass sand to the alkali aqueous solution is (1~5):(5~25). The alkaline leaching treatment also includes filtering, washing to a pH value of 7-7.5, and drying the quartz glass particles. The acid leaching treatment involves placing the calcined coarse fused silica sand in an acid-resistant reactor or tank equipped with a heating and stirring device, and adding oxalic acid and glacial acetic acid. The concentration of the oxalic acid is 0.1–2 mol / L, and the concentration of the glacial acetic acid is 0.1–2 mol / L. The solid-liquid ratio of the coarse fused silica sand to the mixed acid is (1–5):(5–25). The acid leaching treatment conditions also include a temperature of 70℃–90℃, a stirring speed of 100–200 r / min, and an acid leaching time of 8–20 h.

2. The method for preparing high-purity fused silica sand according to claim 1, characterized in that, The steps for pre-treating waste quartz glass include: Waste quartz glass is crushed in two stages: the first stage crushes the waste quartz glass into particles of 10-20mm; the second stage crushes the waste quartz glass into particles smaller than 10mm. The quartz glass particles broken to less than 10mm are cleaned and dried. The dried quartz glass particles are finely crushed and then screened to obtain quartz glass particles with a particle size > 0.18 mm, thus obtaining coarse quartz glass sand.

3. The method for preparing high-purity fused silica sand according to claim 2, characterized in that, The grinding and crushing equipment used to finely crush the dried quartz glass particles has a zirconium oxide or agate lining, and the grinding media are zirconium oxide balls or agate balls.

4. The method for preparing high-purity fused silica sand according to claim 1, characterized in that, The acid leaching treatment also includes filtering and washing the acid-leached coarse fused silica sand to a pH of 6.5-7, and drying the washed coarse fused silica sand.

5. The method for preparing high-purity fused silica sand according to claim 4, characterized in that, The preparation method yields mixed-particle-size fused silica glass sand after drying, with a SiO2 content greater than 98%.

6. The method for preparing high-purity fused silica sand according to claim 1, characterized in that, The purpose of the classification treatment of high-purity fused silica sand of mixed particle sizes is as follows: High-purity fused silica with a particle size of 0.18 mm or greater and 0.25 mm or less is used in the production of silicon compounds in the metallurgical raw materials, additives and chemical industries. High-purity fused silica sand with a particle size greater than 0.25 mm and less than or equal to 0.83 mm is used as raw material for ceramics and refractory materials; High-purity fused silica sand with a particle size greater than 0.83 mm is returned to the waste silica glass pretreatment step.

7. A high-purity fused silica sand, characterized in that, The high-purity fused silica sand is obtained by the preparation method described in any one of claims 1 to 6, wherein the SiO2 content of the high-purity fused silica sand is greater than 98%; wherein the SiO2 content is greater than or equal to 98% and less than or equal to 99% is low-end high-purity fused silica sand, the SiO2 content is greater than 99% and less than or equal to 99.9% is mid-end high-purity fused silica sand, and the SiO2 content is greater than 99.9% is high-end high-purity fused silica sand.

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