Method for preparing high-purity quartz by twice roasting-acid leaching combined process and high-purity quartz

Abstract

The application provides a method for preparing high-purity quartz by twice roasting-acid leaching combined process and high-purity quartz, and the method comprises the following steps: pretreating quartz raw ore to obtain first quartz particles; performing first roasting on the first quartz particles to obtain second quartz particles; performing first acid leaching on the second quartz particles to obtain third quartz particles; mixing the third quartz particles with a roasting aid and then performing second roasting to obtain fourth quartz particles; and performing second acid leaching on the fourth quartz particles, and then washing, drying and obtaining high-purity quartz. The high-purity quartz is prepared by the above method, the content of SiO2 in the high-purity quartz is greater than 99.99%, and the highest content can reach 99.998%. The application adopts the activated roasting-thermal pressure acid leaching-aid roasting-normal pressure acid leaching combined process to realize efficient purification of quartz, reuses heat energy in aid roasting, effectively removes lattice impurities and inert impurities which are difficult to remove in conventional processes, and the roasting aid is environment-friendly, the acid consumption is small, and the product purity is high.

Description

Technical Field

[0001] This invention relates to the field of quartz purification, and more specifically, to a method for preparing high-purity quartz using a combined two-stage roasting-acid leaching process, and the high-purity quartz thereof. Background Technology

[0002] High-purity quartz is a high-purity quartz material, typically obtained through the fine purification of ores such as crystal, vein quartz, and granite pegmatite. Its silicon dioxide (SiO2) content reaches over 99.9%, while maintaining its crystalline structure. As a key raw material for modern silicon-based high-tech industries, high-purity quartz plays a vital role in several strategic emerging industries, such as quartz glass, large-scale integrated circuits, optical fiber communication, solar cells, and aerospace materials. The application characteristics of quartz products are closely related to their purity; higher-purity quartz products not only possess better mechanical properties but also exhibit excellent insulation, corrosion resistance, and arc resistance.

[0003] However, current high-purity quartz purification processes often rely on energy-intensive and polluting methods such as acid leaching and chloride roasting to remove small amounts of residual gangue minerals and some surface impurities. This series of purification processes, especially chloride roasting, typically involves heating the quartz to over 1000°C for several hours followed by cooling and washing, resulting in high energy consumption and long processing times. The subsequent acid leaching process requires additional heating of both the quartz and the acid solution, leading to significant pollution and a lack of targeted removal of impurities. Furthermore, it has limited effectiveness in removing some inert metal oxides and their covering areas. Therefore, developing a new, more efficient, energy-saving, and highly effective high-purity quartz purification process is an urgent need for the industry. 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 provide a novel high-purity quartz purification process that is more efficient, energy-saving, and capable of effectively removing impurities.

[0005] To achieve the above objectives, the present invention provides a method for preparing high-purity quartz using a combined two-stage roasting-acid leaching process.

[0006] The method for preparing high-purity quartz using the combined two-calcination-acid leaching process includes the following steps:

[0007] The raw quartz ore is pretreated to obtain the first quartz particles.

[0008] The first quartz particle was calcined for the first time to obtain the second quartz particle.

[0009] The second quartz particle was subjected to a first acid leaching to obtain the third quartz particle.

[0010] The third quartz particles were mixed with a calcination aid and then calcined a second time to obtain the fourth quartz particles.

[0011] The fourth quartz particle was subjected to a second acid leaching, followed by water washing and drying to obtain the high-purity quartz.

[0012] In an exemplary embodiment of the method for preparing high-purity quartz using a combined two-stage roasting-acid leaching process of the present invention, the pretreatment may include: crushing, grinding, and screening the quartz ore to obtain coarse quartz particles, and performing reverse flotation on the coarse quartz particles to obtain the first quartz particles, wherein the particle size of the coarse quartz particles is +200 mesh to -50 mesh.

[0013] In an exemplary embodiment of the method for preparing high-purity quartz using the combined two-calcination-acid leaching process of the present invention, the reverse flotation may include the following steps:

[0014] The coarse quartz particles are prepared into a slurry with a concentration of 20% to 50%.

[0015] The pH of the slurry is adjusted to 1.0-2.5, and a collector is added to the slurry for reverse flotation treatment.

[0016] The reverse flotation concentrate was collected and washed with water until the pH of the filtrate was 6.5-7. After filtration, the first quartz particles were obtained.

[0017] The added collector is one or more cationic amine collectors, and the amount of the collector added is 100g / t to 200g / t.

[0018] In an exemplary embodiment of the method for preparing high-purity quartz using a combined two-calcination-acid leaching process of the present invention, the first calcination may be an activation calcination, which may include: calcining the first quartz particles at a temperature of 900℃~1100℃ for 0.5h~4h to obtain the second quartz particles.

[0019] In an exemplary embodiment of the method for preparing high-purity quartz using the combined two-stage roasting-acid leaching process of the present invention, the first acid leaching may be hot-press acid leaching, and may include the following steps:

[0020] A first acid leaching solution is prepared in a reaction vessel, wherein the molar concentration of hydrofluoric acid is 1 mol / L to 4 mol / L, the molar concentration of oxalic acid is 0.2 mol / L to 0.4 mol / L, the molar concentration of hydrochloric acid is 0.5 mol / L to 1 mol / L, and the molar concentration of nitric acid is 0.2 mol / L to 0.5 mol / L.

[0021] The second quartz particles are added to the first acid leaching solution for a first acid leaching treatment. The solid-liquid ratio of the second quartz particles to the first acid leaching solution is 0.5 kg / L to 1 kg / L. The temperature of the first acid leaching treatment is 110℃ to 180℃, and the time is 0.5 h to 2 h.

[0022] The product of the first acid leaching treatment is filtered and washed until the pH of the filtrate is 6.5-7 to obtain the third quartz particles, the third quartz particles having a water content of 10%-15%.

[0023] In an exemplary embodiment of the method for preparing high-purity quartz using the combined two-calcination-acid leaching process of the present invention, the second calcination may be an auxiliary agent calcination, and may include the following steps:

[0024] The calcination aid is added to the third quartz particles and stirred evenly to obtain the first wet mixture.

[0025] The first wet mixture is placed at a temperature of 450℃~550℃ and heated for 60min~120min to obtain the fourth quartz particles; wherein the mass ratio of the calcination aid to the third quartz particles is 0.1~0.3, and the calcination aid includes one or both of ammonium sulfate and ammonium bisulfate.

[0026] In an exemplary embodiment of the method for preparing high-purity quartz using the combined two-stage roasting-acid leaching process of the present invention, the second acid leaching may be atmospheric pressure acid leaching and may include the following steps:

[0027] A second acid leaching solution is prepared in the reaction vessel, wherein the molar concentration of hydrofluoric acid in the second acid leaching solution is 0.8 mol / L to 2 mol / L, and the molar concentration of hydrochloric acid is 0.2 mol / L to 1 mol / L.

[0028] The hot fourth quartz particles after the second calcination treatment are added to the reactor, and the amount and rate of addition of the fourth quartz particles are controlled to keep the acid leaching temperature in the reactor at 80℃~90℃. The total amount of the fourth quartz particles added is 0.5kg / L~1kg / L of the solid-liquid ratio of the second acid leaching solution.

[0029] After the fourth quartz particle is added, continue stirring for 0.5h to 3h.

[0030] The product of the second acid leaching treatment is filtered, washed until the pH of the filtrate is 7, and dried to obtain the high-purity quartz.

[0031] In an exemplary embodiment of the method for preparing high-purity quartz using the combined process of two roasting-acid leaching of the present invention, the quartz ore may be quartz ore, the main mineral composition of the quartz ore may be quartz, containing one or more of feldspar, mica, talc, calcite and aluminum-iron-manganese-titanium oxide gangue minerals; the quartz includes lattice impurities and inclusions.

[0032] The fourth quartz particle may include quartz, and one or more soluble sulfates selected from aluminum sulfate, magnesium sulfate, calcium sulfate, and ferric sulfate formed by the reaction.

[0033] In an exemplary embodiment of the method for preparing high-purity quartz using the combined process of two roasting-acid leaching of the present invention, the acid leaching filtrate of the second acid leaching can be recycled to the first acid leaching for reuse after dilution or the addition of mixed acid, wherein the mixed acid can be one or more of hydrofluoric acid, hydrochloric acid, oxalic acid, and nitric acid.

[0034] The heating furnace used for the first and second roasting may be equipped with a tail gas spray collection device, and the spray liquid used by the tail gas spray collection device is industrial water, which is used for the pretreatment.

[0035] In another aspect, the present invention provides a high-purity quartz. The high-purity quartz is prepared by a combined calcination-acid leaching process as described in any one of the above-mentioned methods. The high-purity quartz contains less than 20 ppm Al, less than 1 ppm Na, less than 1 ppm K, and has a SiO2 content of 99.99% to 99.998%.

[0036] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0037] (1) The present invention uses the combined action of activation roasting and one-time pressure acid leaching to cause quartz to undergo a reconstructive phase transformation through activation roasting. During the phase transformation, the quartz breaks along the surface cracks, exposing inclusions and causing some lattice impurities in the quartz to migrate outward. Using hot-press acid leaching, the acid solution can more easily enter the cracks in the quartz, and the acid solution has stronger reactivity, which can efficiently remove impurities in the cracks exposed by activation roasting as well as lattice impurities that migrate outward during roasting.

[0038] (2) The calcination of the additives generates highly acidic ammonium pyrosulfate, which reacts with inert metal oxides on the surface and in the cracks of quartz to transform them into soluble sulfates. The atmospheric pressure acid leaching step specifically removes the soluble sulfates generated in the reaction and the impurities that were originally covered by inert impurities but are now exposed. This invention can simultaneously and efficiently remove lattice impurities and inert impurities from quartz.

[0039] (3) The present invention greatly reduces the energy consumption of the overall process through the auxiliary agent roasting-acid leaching heat cycle process, while reducing the acid consumption and the discharge of acidic wastewater, which has good economic and environmental benefits.

[0040] (4) The quartz product of the present invention has a purity of 99.99% or higher, and the process can be combined with other high-purity quartz preparation processes to achieve better purification effect.

[0041] (5) In this invention, ammonium sulfate or ammonium bisulfate is used as a roasting aid. The roasting temperature is lower than that of traditional chloride salt roasting, and the ammonia gas produced can be recovered and treated to produce ammonia water, reducing the environmental impact of the process. This improves the environmental friendliness and sustainability of the entire process and conforms to the principles of green chemistry. Attached Figure Description

[0042] 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:

[0043] Figure 1 A process step diagram of an exemplary embodiment of the method for preparing high-purity quartz using a combined two-calcination-acid leaching process of the present invention is shown.

[0044] Figure 2 The diagram shows an XRD pattern of an embodiment of the method for preparing high-purity quartz using a combined two-calcination-acid leaching process according to the present invention.

[0045] Figure 3 A process flow diagram of an embodiment of the method for preparing high-purity quartz using a combined two-calcination-acid leaching process of the present invention is shown.

[0046] Figure 4 The diagram shows an XRD pattern of the finished high-purity quartz product prepared by the two-stage roasting-acid leaching combined process of the present invention. Detailed Implementation

[0047] In the following, the method for preparing high-purity quartz using the two-stage roasting-acid leaching combined process of the present invention and the high-purity quartz will be described in detail with reference to exemplary embodiments.

[0048] It should be noted that terms such as "first," "second," and "third" are used merely for ease of description and distinction, and should not be construed as indicating or implying relative importance. The terms "S1," "S2," and "S3" used in this invention are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0049] Exemplary Example 1

[0050] This exemplary embodiment provides a method for preparing high-purity quartz using a combined two-stage roasting-acid leaching process. To achieve high and efficient quartz purification, a combined process of activated roasting, hot-pressing acid leaching, additive roasting, and atmospheric-pressure acid leaching is employed. During activated roasting, the quartz transforms from the α-quartz phase to the β-quartz phase, and then to the α-tridymite phase. During cooling, the α-tridymite phase transforms back into the β-quartz phase and then further back into the α-quartz phase. This lattice restructuring process is accompanied by a lattice rejection reaction. This reaction causes impurities in the lattice to migrate outwards and be expelled from the quartz crystal. Simultaneously, some gangue minerals decompose at high temperatures, making them easier to remove in the subsequent acid leaching step. The hot-pressing acid leaching stage aims to remove lattice impurities that migrated from the interior of the quartz to the surface during the first roasting process. During the calcination stage, the calcination aids used react with weathered inert impurities on the surface of quartz or embedded in the intercrystalline lattice, as well as some gangue minerals that were not removed by flotation or primary acid leaching. The reacted quartz is then directly added to the acid solution. Impurities in the quartz exhibit stronger reactivity at high temperatures, making them more readily react with the acid solution and removing some impurities that were originally encapsulated by inert impurities and difficult to remove. Simultaneously, the high-temperature quartz heats the acid solution, efficiently removing impurities while simultaneously recovering thermal energy. This combined process achieves deep purification of quartz, effectively improving its purity, while optimizing the efficiency and environmental friendliness of the entire purification process.

[0051] The principle of heat energy reuse is as follows:

[0052] According to the heat dissipation formula: Q=A(t) w -t0)F.

[0053] Where Q represents heat dissipation, in W; t w t0 is the surface temperature of the radiator (°C); t0 is the ambient temperature (°C); F is the surface area of ​​the radiator (m²). 2 A is the overall heat transfer coefficient, w / (℃×m). 2 ), generally, the reactor operates at 3000 W / (℃×m 2 )about.

[0054] The specific heat capacity of quartz is temperature-dependent. It is generally considered that the average specific heat capacity of quartz glass is 772 J / (kg·K) in the 0-100℃ range, 964 J / (kg·K) in the 0-500℃ range, and 1052 J / (kg·K) in the 0-900℃ range. The specific heat capacity of water is 4200 J / (kg·K). Assuming the calcination temperature of the additive is 550℃, the temperature of the acid solution and air at room temperature is 20℃, and the acid leaching temperature is 90℃, then: 1052 × (550 - 90) ÷ 4200 ÷ (90 - 20) = 1.64, meaning that the heat contained in each kilogram of quartz decreasing from 550℃ to 90℃ is enough to raise the temperature of 1.64 kilograms of acid solution from room temperature to 90℃. Industrially, a volume of 5m³ is used. 3The reactor vessel typically has a main body radius of 9.2m, a height of 18.4m, and a surface area of ​​1595m². 2 The time required for the quartz and acid solution in the tank to cool down from 90℃ to room temperature is: (90-20)×(772×1829+4200×3000)÷(90-20)÷3000÷1595=2.92h. Therefore, this time is sufficient to maintain the temperature during the stirring of the acid leaching process.

[0055] Specifically, such as Figure 1 As shown, the process flow steps of the method for preparing high-purity quartz using the combined two-calcination-acid leaching process of this exemplary embodiment include:

[0056] S1. Pre-treat the raw quartz ore to obtain the first quartz particles.

[0057] In this exemplary embodiment, the quartz ore may be quartz mineral, the main mineral composition of which may be quartz, and may contain one or more of feldspar, mica, talc, calcite and aluminum-iron-manganese-titanium oxide gangue minerals. The quartz may contain lattice impurities and inclusions.

[0058] In this exemplary embodiment, preprocessing may include:

[0059] S11. The quartz ore is crushed, ground, and screened to obtain coarse quartz particles. These coarse quartz particles are then subjected to reverse flotation to obtain the first quartz particles. The particle size of the coarse quartz particles is +200 mesh to -50 mesh. For example, the particle size of the coarse quartz particles can be 200 mesh, 150 mesh, 50 mesh, etc. If the particle size of the coarse quartz particles is too large, it will lead to incomplete dissociation of quartz monomers, reduced flotation efficiency, insufficient subsequent roasting reaction of additives, and decreased product purity. If the particle size is too fine, it will cause increased quartz loss during acid leaching and flotation, resulting in a lower yield.

[0060] In this exemplary embodiment, the crushing can be performed using one or more of the following: toothed roll crusher, double roll crusher, jaw crusher, gyratory crusher, and cone crusher.

[0061] In this exemplary embodiment, further, anti-floating may include the following steps:

[0062] S111. The coarse quartz particles are adjusted into a slurry with a concentration of 20% to 50%. For example, the slurry concentration can be 20%, 30%, or 50%. Too low a slurry concentration will result in a low concentrate recovery rate. Too high a slurry concentration will worsen the operating conditions of the flotation machine and reduce the flotation effect.

[0063] S112. Adjust the pH of the pulp to 1.0–2.5 and add a collector to the pulp for reverse flotation. For example, the pulp pH can be 1.0, 1.5, or 2.5. The pH adjuster can be hydrofluoric acid. Too low a pH will consume more hydrofluoric acid and generate insoluble impurities such as aluminum fluoride and calcium fluoride during flotation, affecting quartz purity. Too high a pH will cause quartz in the pulp system to exhibit a negative potential, resulting in significant adsorption by the collector and a substantial decrease in concentrate yield and grade. The collector can be one or more cationic amine collectors, and the dosage can be 100 g / t–200 g / t. For example, the collector can be one or more cationic amine collectors such as dodecylamine, hexadecylamine, or octadecylamine, and the dosage can be 100 g / t, 150 g / t, or 200 g / t. Excessive use of collectors will lead to waste of reagents and increase the difficulty of wastewater treatment; insufficient use will make it difficult to completely float out impurities in quartz, resulting in a decrease in the grade of quartz concentrate.

[0064] More specifically, the slurry can be placed in an aerated agitated flotation machine, air is introduced and the mixture is stirred, and a scraper is activated to continuously skim off the upper layer of foam until the flotation endpoint is reached. The air introduction rate is typically 80 L / h to 160 L / h, for example, 80 L / h, 120 L / h, or 160 L / h. An excessively high air introduction rate will reduce bubble stability and waste energy in the later stages of flotation, while an excessively low rate will fail to generate enough bubbles, reducing the flotation efficiency.

[0065] S113. Collect the reverse flotation concentrate and wash it with water until the pH of the filtrate is 6.5-7. After filtration, the first quartz particles are obtained. Wash the slurry with water until the pH of the filtrate is 6.5-7 to ensure the removal of impurities such as collectors.

[0066] S2. The first quartz particle is roasted once to obtain the second quartz particle.

[0067] In this exemplary embodiment, the first calcination is an activation calcination, which may include the following steps:

[0068] The first quartz particles are calcined at 900℃~1100℃ for 0.5h~4h to obtain the second quartz particles. For example, the first calcination temperature can be 900℃, 950℃, 1100℃, etc. If the first calcination temperature is too low, the α-quartz phase cannot be transformed into the α-tridymite phase, and lattice impurities cannot be removed; if the first calcination temperature is too high, energy consumption will increase. The calcination time can be 0.5h, 1.0h, 4h, etc. If the first calcination time is too short, the impurity minerals will not react completely; if the first calcination time is too long, energy consumption will increase.

[0069] More specifically, the first quartz particle can be placed in a heating furnace with a quartz glass or quartz ceramic lining for calcination.

[0070] S3. The second quartz particle is subjected to a first acid leaching to obtain the third quartz particle.

[0071] In this exemplary embodiment, the first acid leaching is a hot-press acid leaching, which includes the following steps:

[0072] S31. Prepare a first acid leaching solution in a reaction vessel. The first acid leaching solution contains hydrofluoric acid at a molar concentration of 1 mol / L to 4 mol / L, oxalic acid at a molar concentration of 0.2 mol / L to 0.4 mol / L, hydrochloric acid at a molar concentration of 0.5 mol / L to 1 mol / L, and nitric acid at a molar concentration of 0.2 mol / L to 0.5 mol / L. For example, the molar concentration of hydrofluoric acid can be 1 mol / L, 2 mol / L, 4 mol / L, etc.; the molar concentration of oxalic acid can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, etc.; the molar concentration of hydrochloric acid can be 0.5, 0.75, 1.0 mol / L, etc.; and the molar concentration of nitric acid can be 0.2, 0.4, 0.5 mol / L, etc. This step efficiently dissolves gangue minerals and their decomposition products adhering to the quartz surface through pressurization, and corrodes weak points on the quartz surface, exposing surface defects. Hydrofluoric acid is used to corrode some defect sites on the quartz surface, exposing inclusions and other impurities. Excessive concentration leads to significant quartz loss and increases wastewater treatment difficulty, while insufficient concentration results in incomplete corrosion and incomplete exposure of impurities, affecting purification efficiency. Oxalic acid is used to dissolve iron impurities in the quartz. Excessive concentration leads to acid waste and increased wastewater treatment difficulty, while insufficient concentration leads to incomplete impurity dissolution. Hydrochloric acid is used to react with other impurities in the quartz to form soluble chloride salts. Excessive concentration increases costs and further complicates subsequent wastewater treatment, while insufficient concentration leads to incomplete impurity dissolution. Nitric acid is used to increase the acid abundance and dissolve small amounts of impurities insoluble in hydrochloric acid. Excessive concentration increases costs and wastewater treatment difficulty, while insufficient concentration leads to incomplete impurity dissolution and may cause the formation of insoluble fluoride salts.

[0073] More specifically, the reactor can be an acid-resistant autoclaved reactor equipped with heating and stirring devices.

[0074] S32. The second quartz particles are added to the first acid leaching solution for the first acid leaching treatment. The solid-liquid ratio of the second quartz particles to the first acid leaching solution is 0.5 kg / L to 1 kg / L. The temperature of the first acid leaching treatment is 110℃ to 180℃, such as 110℃, 150℃, 180℃, etc. Too low a temperature will reduce the acid leaching effect and decrease the impurity dissolution rate, while too high a temperature will lead to energy waste. The acid leaching treatment time is 0.5h to 2h, such as 0.5h, 1h, 2h, etc. Too short an acid leaching time will lead to insufficient reaction and incomplete dissolution of impurities, while too long an acid leaching time will lead to increased energy consumption.

[0075] For example, the solid-liquid ratio can be 0.5 kg / L, 0.75 kg / L, or 1 kg / L. If the solid-liquid ratio is too high, the acid solution and the third quartz particles will not be in sufficient contact, and the impurities will not be completely dissolved. If the solid-liquid ratio is too low, the acid consumption will be high and the energy consumption will be high.

[0076] S33. The first acid leaching product is filtered and washed until the pH of the filtrate is 6.5–7 to obtain third quartz particles. The moisture content of the third quartz particles is 10%–15%, for example, 10%, 13%, or 15%. Too low a moisture content will lead to incomplete wet mixing, while too high a moisture content will lead to hydrolysis of the additives. More specifically, the filtration and washing of the first acid leaching product is carried out using a filter press or a vacuum belt filter equipped with a washing device.

[0077] S4. The third quartz particles are mixed with the calcination aid and then calcined a second time to obtain the fourth quartz particles.

[0078] In this exemplary embodiment, the second calcination is an additive calcination, which may include the following steps:

[0079] S41. Add the calcination aid to the third quartz particles and stir evenly to obtain the first wet mixture.

[0080] S42. Place the first wet mixture at a temperature of 450℃~550℃ and heat for 60min~120min to obtain the fourth quartz particles. For example, the secondary calcination temperature can be 450℃, 500℃, 550℃, etc. If the calcination temperature is too low, the calcination aid will not decompose into strong acidic substances to react with impurities; if the calcination temperature is too high, the strong acidic substances decomposed by the calcination aid will continue to decompose into other substances, and some metal sulfates will also decompose into insoluble substances, reducing the purification effect. The calcination time can be 60min, 70min, 120min, etc. If the calcination time is too short, the reaction will not be complete; if the calcination time is too long, energy consumption will be too high.

[0081] The roasting aid may include one or both of ammonium sulfate and ammonium bisulfate, and the mass ratio of the roasting aid to the third quartz particles may be 0.1 to 0.3. For example, the mass ratio may be 0.1, 0.2, 0.3, etc. A molar ratio that is too low will lead to incomplete reaction and reduced purification effect; a molar ratio that is too high will lead to a large consumption of roasting aid and increased cost. The roasting aids ammonium sulfate and ammonium bisulfate decompose at a suitable temperature to produce highly acidic pyrosulfuric acid (H₂S₂O₇). The pyrosulfuric acid reacts with weathered inert impurities on the quartz surface or embedded in the interstitial crystal lattice, as well as some gangue minerals that have not been removed by flotation or hot-pressing acid leaching, to form soluble sulfates.

[0082] More specifically, heating can be performed using a furnace with a quartz glass or quartz ceramic lining in the heating chamber. The furnace may also be equipped with a tail gas spray collection device, and the spray liquid can be industrial water. In this exemplary embodiment, the fourth quartz particle includes quartz and one or more soluble sulfates selected from aluminum sulfate, magnesium sulfate, calcium sulfate, and ferric sulfate formed by the reaction.

[0083] S5. The fourth quartz particles are subjected to a second acid leaching, followed by water washing and drying to obtain high-purity quartz.

[0084] In this exemplary embodiment, the second acid leaching is an atmospheric pressure acid leaching, which includes the following steps:

[0085] S51. Prepare a second acid leaching solution in the reactor. The molar concentration of hydrofluoric acid in the second acid leaching solution is 0.8 mol / L to 2 mol / L, and the molar concentration of hydrochloric acid is 0.2 mol / L to 1 mol / L. For example, the molar concentration of hydrofluoric acid can be 0.8 mol / L, 1.0 mol / L, 2.0 mol / L, etc., and the molar concentration of hydrochloric acid can be 0.2 mol / L, 0.4 mol / L, 1.0 mol / L, etc. The purpose of hydrofluoric acid is to dissolve the active sites exposed on the surface of the quartz particles after the calcination of the additives. Too high a concentration will lead to extensive corrosion of the quartz, a decrease in yield, and an increase in the difficulty of wastewater treatment. Too low a concentration will lead to incomplete corrosion of surface defect sites and a reduction in purification effect. The purpose of hydrochloric acid is to react with other impurities in the quartz to form soluble chloride salts. Too high a concentration will increase the difficulty of wastewater treatment. Too low a concentration will lead to incomplete dissolution of impurities, a reduction in purification effect, and may lead to the formation of insoluble fluoride salts.

[0086] S52. Add the hot fourth quartz particles after the second calcination treatment to the reactor, and control the amount and rate of addition of the fourth quartz particles to maintain the temperature in the reactor at 80℃~90℃; for example, 80℃, 85℃, 90℃. Too low a temperature will result in slow feeding and insufficient acid leaching reaction; too high a temperature will cause the acid solution to boil violently. The total amount of fourth quartz particles added to the solid-liquid ratio of the second acid leaching solution is 0.5kg / L~1kg / L, for example, 0.5kg / L, 0.8kg / L, 1kg / L.

[0087] S53. After the fourth quartz particle is added, continue stirring in the reactor for 0.5h to 3h, for example, 2h, 2.5h, or 3h. Too short a time will result in incomplete reaction, while too long an acid leaching time will increase energy consumption.

[0088] S54. The product of the second acid leaching treatment is filtered, washed until the pH value of the filtrate is 7, and dried to obtain the high-purity quartz.

[0089] More specifically, the reactor can be an acid-resistant reactor equipped with heating and stirring devices.

[0090] More specifically, the acid leaching products can be filtered and washed using a filter press equipped with a washing device or a vacuum belt filter.

[0091] In this exemplary embodiment, the leaching filtrate from the second acid leaching is diluted or mixed with acid and then recycled back to the first acid leaching for reuse. The mixed acid can be one or more of hydrofluoric acid, hydrochloric acid, oxalic acid, and nitric acid. The heating furnace used for the first and second roasting can be equipped with a tail gas spray collection device. The spray liquid used in the tail gas spray collection device can be industrial water, which can also be used for pretreatment. For example, industrial water can be added to the coarse quartz particles to form a slurry.

[0092] In this exemplary embodiment, the secondary acid leaching stage mainly involves dissolving and removing the sulfates generated during the calcination of the additives, as well as removing some impurities that were originally encapsulated by inert impurities and were difficult to remove.

[0093] Because primary and secondary acid leaching serve different purposes, the mixed acid formulations for primary and secondary acid leaching also differ. Secondary acid leaching uses fewer types of acids, resulting in very few impurities in the leaching solution. The secondary acid leaching filtrate can be recycled back to the primary acid leaching process for reuse after dilution or the addition of new acids (such as one or more of hydrofluoric acid, hydrochloric acid, oxalic acid, and nitric acid).

[0094] Exemplary Example 2

[0095] This exemplary embodiment provides a high-purity quartz, which is prepared by a method for preparing high-purity quartz through a two-stage roasting-acid leaching combined process as described in Exemplary Embodiment 1 above. The SiO2 content in the high-purity quartz can be greater than 99.99%.

[0096] In this exemplary embodiment, the Al content in the high-purity quartz can be less than 20 ppm, the Na content can be less than 1 ppm, the K content can be less than 1 ppm, and the SiO2 content can be 99.99% to 99.998%.

[0097] To better understand the exemplary embodiments of the present invention described above, further explanation is provided below with reference to specific embodiments and accompanying drawings.

[0098] Example 1

[0099] The quartz sample selected for the experiment in this embodiment was powdered quartz, and the XRD results of the raw quartz ore are as follows: Figure 2 As shown, the raw quartz ore mainly contains quartz and talc. The XRF analysis results of the raw ore are shown in Table 1 below. The main impurity elements in the raw ore are Mg, Al, and Ca.

[0100] Table 1. Main chemical components of raw quartz ore

[0101] content(%) 97.85 1.12 0.21 0.10 0.05 0.02

[0102] Note: Elements not listed indicate that their content is less than 0.01%.

[0103] like Figure 3 As shown, the method for preparing high-purity quartz in this embodiment includes the following steps:

[0104] (1) The raw quartz ore was crushed using a toothed roller crusher. After grinding and screening, coarse quartz particles of -50 mesh to +200 mesh were obtained.

[0105] (2) Reverse flotation of coarse quartz particles: The coarse quartz particles are adjusted into a slurry with industrial water and the slurry concentration is 20%; the pH of the slurry is adjusted to 1.0 with hydrofluoric acid; the collector is dodecylamine and the amount of collector is 100g / t; the slurry is placed in an aerated stirred flotation machine, air is introduced and stirred, the air introduction rate is 80L / h, and the scraper is started to continuously scrape off the upper layer of foam until the flotation endpoint is reached; the flotation concentrate is collected and washed with water until the pH of the filtrate is 6.5, and the first quartz particles are obtained after filtration.

[0106] (3) The first quartz particle is placed in a heating furnace with a quartz glass or ceramic lining and activated and calcined at 900°C for 0.5 h. After the reaction is completed, the second quartz particle is obtained.

[0107] (4) The second quartz particles were subjected to hot-press acid leaching: the solid-liquid ratio of the acid leaching solution was 0.5 kg / L; the molar concentrations of hydrofluoric acid, oxalic acid, hydrochloric acid, and nitric acid in the acid leaching solution were 4 mol / L, 0.4 mol / L, 1 mol / L, and 0.5 mol / L; the acid leaching temperature was 180℃; the acid leaching time was 2 h; after the acid leaching reaction was completed, the acid leaching product was filtered and washed until the pH of the filtrate was 7. The filter residue was washed and dried to obtain the third quartz particles. The content of each impurity element in the third quartz particles is shown in Table 2 below. The water content of the third quartz particles was 15%.

[0108] Table 2. Content of various impurity elements in the third quartz particle (unit: μg / g)

[0109] 28.5 1.8 7.6 21.4 - 0.4 - - 0.15 3.5 0.1 0.8 1.8 1.0 2.1 69.15

[0110] (5) Mix ammonium sulfate and the third quartz particles at a mass ratio of 0.3, mix them evenly, and place them in a high-temperature roasting furnace equipped with a gas collection device. Roast at 450°C for 120 minutes to obtain the fourth quartz particles.

[0111] (6) Acid leaching of the fourth quartz particles under normal pressure: A second acid leaching solution is prepared in an acid-resistant reactor equipped with a heating and stirring device. The molar concentration of hydrofluoric acid in the second acid leaching solution is 2 mol / L, and the molar concentration of hydrochloric acid is 1 mol / L. The hot fourth quartz particles after the second calcination treatment are added to the acid-resistant reactor equipped with a stirring device. The reactor is kept under stirring and the amount and rate of addition of the fourth quartz particles are controlled so that the acid temperature in the reactor is kept at 90℃. The total amount of fourth quartz particles added is 1 kg / L of the solid-liquid ratio of the second acid leaching solution. After the fourth quartz particles are added, the reactor is stirred continuously for 2 hours.

[0112] (7) The product of atmospheric pressure acid leaching is filtered and washed until the pH of the filtrate is 7. The filtered product is dried at 105℃ for 24h to obtain high-purity quartz. The atmospheric pressure acid leaching filtrate is recycled to pressurized acid leaching after adding 0.8mol / L oxalic acid, 1mol / L hydrochloric acid and 1mol / L nitric acid.

[0113] The high-purity quartz product was tested using the silicon tetrafluoride volatilization method according to the national standard GB / T32649—2016, and the purity was found to be 99.997%. The content of each element in the high-purity quartz product is shown in Table 3 below.

[0114] Table 3. Content of various impurity elements in high-purity quartz products (unit: μg / g)

[0115] 15.8 0.7 3.6 4.1 - 0.3 - - 0.04 1.3 0.1 0.7 0.9 0.6 0.9 29.04

[0116] Where: - indicates that it is below the ICP detection limit, i.e., ≤0.006.

[0117] The XRD results of high-purity quartz are as follows Figure 4 As shown, the purified high-purity quartz product contains only the characteristic diffraction peaks of quartz, with no diffraction peaks of impurity minerals observed.

[0118] Example 2

[0119] The quartz sample selected for the experiment in this embodiment was vein quartz. The XRF analysis results of the raw ore are shown in Table 4 below. It can be seen that the main impurity elements of the raw ore are Mg, Al, Ca, Fe, etc.

[0120] Table 4. Main chemical components of raw quartz ore

[0121] content(%) 97.59 0.35 1.80 0.05 0.02 0.02 0.01 0.16

[0122] Note: Elements not listed indicate that their content is less than 0.01%.

[0123] like Figure 3 As shown, the method for preparing high-purity quartz in this embodiment includes the following steps:

[0124] (1) The quartz ore was crushed by a double roll crusher, and after grinding and screening, coarse quartz particles of -50 mesh to +200 mesh were obtained.

[0125] (2) Reverse flotation of coarse quartz particles: The coarse quartz particles are adjusted into a slurry with industrial water and the slurry concentration is 50%; the pH of the slurry is adjusted to 2.5 with hydrofluoric acid; the collector is dodecylamine and the amount of collector is 200g / t; the slurry is placed in an aerated stirred flotation machine, air is introduced and stirred, the air introduction rate is 160L / h, and the scraper is started to continuously scrape off the upper layer of foam until the flotation endpoint is reached; the flotation concentrate is collected and washed with water until the pH of the filtrate is 7, and the first quartz particles are obtained after filtration.

[0126] (3) The first quartz particle is placed in a heating furnace with a quartz glass or ceramic lining and activated and calcined at 1100℃ for 4 hours. After the reaction is completed, the second quartz particle is obtained.

[0127] (4) The second quartz particles were subjected to hot-press acid leaching: the solid-liquid ratio of the acid leaching solution was 1 kg / L; the molar concentrations of hydrofluoric acid, oxalic acid, hydrochloric acid, and nitric acid in the acid leaching solution were 1 mol / L, 0.2 mol / L, 0.5 mol / L, and 0.2 mol / L; the acid leaching temperature was 110℃; the acid leaching time was 1 h; after the acid leaching reaction was completed, the acid leaching product was filtered and washed until the pH of the filtrate was 7. The filter residue was washed and dried to obtain the third quartz particles. The content of each impurity element in the third quartz particles is shown in Table 5 below. The water content of the third quartz particles was 10%.

[0128] Table 5. Content of various impurity elements in the third quartz particles (unit: μg / g)

[0129] 45.3 7.3 12.4 30.2 - 0.5 - - 0.50 5.4 1.1 0.5 0.9 1.2 2.3 107.6

[0130] (5) Mix ammonium sulfate and the third quartz particles at a mass ratio of 0.1, mix them evenly, and place them in a high-temperature roasting furnace equipped with a gas collection device. Roast at 550°C for 120 minutes to obtain the fourth quartz particles.

[0131] (6) Acid leaching of the fourth quartz particles under normal pressure: A second acid leaching solution is prepared in an acid-resistant reactor equipped with a heating and stirring device. The molar concentration of hydrofluoric acid in the second acid leaching solution is 0.8 mol / L and the molar concentration of hydrochloric acid is 0.2 mol / L. The hot fourth quartz particles after the second calcination treatment are added to the acid-resistant reactor equipped with a stirring device. The reactor is kept under stirring and the amount and rate of addition of the fourth quartz particles are controlled so that the acid solution temperature in the reactor is maintained at 90℃. The total amount of fourth quartz particles added is 0.5 kg / L of solid-liquid ratio to the second acid leaching solution. After the fourth quartz particles are added, the reactor is stirred continuously for 3 hours.

[0132] (7) The product of atmospheric pressure acid leaching is filtered and washed until the pH of the filtrate is 6.5. The filtered product is dried at 105℃ for 24h to obtain high-purity quartz. The atmospheric pressure acid leaching filtrate is recycled to pressurized acid leaching after adding 3.2mol / L hydrofluoric acid, 0.2mol / L oxalic acid and 0.2mol / L nitric acid.

[0133] The high-purity quartz product was tested using the silicon tetrafluoride volatilization method according to the national standard GB / T32649—2016, and the purity was 99.997%. The content of each element in the high-purity quartz product is shown in Table 6 below.

[0134] Table 6. Content of various impurity elements in high-purity quartz products (unit: μg / g)

[0135] 19.3 0.7 2.4 2.1 - 0.2 - - 0.04 0.8 0.1 0.5 0.7 0.6 0.9 28.34

[0136] Where: - indicates that it is below the ICP detection limit, i.e., ≤0.006.

[0137] Example 3

[0138] The quartz sample selected for the experiment in this embodiment was powdered quartz. The XRF analysis results of the raw ore are shown in Table 7 below. It can be seen that the main impurity elements of the raw ore are Mg, Al, Ca, etc.

[0139] Table 7. Main chemical components of raw quartz ore

[0140] content(%) 97.85 1.12 0.21 0.10 0.05 0.02

[0141] Note: Elements not listed indicate that their content is less than 0.01%.

[0142] like Figure 3 As shown, the preparation method of high-purity quartz in this embodiment includes the following steps:

[0143] (1) The raw quartz ore was crushed by a jaw crusher, and after grinding and screening, coarse quartz particles of -50 mesh to +200 mesh were obtained.

[0144] (2) Reverse flotation of coarse quartz particles: The coarse quartz particles are adjusted into a slurry with industrial water and the slurry concentration is 40%; the pH of the slurry is adjusted to 2.0 with hydrofluoric acid; the collector is dodecylamine and the amount of collector is 150g / t; the slurry is placed in an aerated stirred flotation machine, air is introduced and stirred, the air introduction rate is 120L / h, and the scraper is started to continuously scrape off the upper layer of foam until the flotation endpoint is reached; the flotation concentrate is collected and washed with water until the pH of the filtrate is 7, and the first quartz particles are obtained after filtration.

[0145] (3) The first quartz particle is placed in a heating furnace with a quartz glass or ceramic lining and activated and calcined at 1000℃ for 2 hours. After the reaction is completed, the second quartz particle is obtained.

[0146] (4) The second quartz particles were subjected to hot-press acid leaching: the solid-liquid ratio of the acid leaching solution was 1 kg / L; the molar concentrations of hydrofluoric acid, oxalic acid, hydrochloric acid, and nitric acid in the acid leaching solution were 2 mol / L, 0.3 mol / L, 0.75 mol / L, and 0.4 mol / L; the acid leaching temperature was 150℃; the acid leaching time was 0.5 h; after the acid leaching reaction was completed, the acid leaching product was filtered and washed until the pH of the filtrate was 7. The filter residue was washed and dried to obtain the third quartz particles. The content of each impurity element in the third quartz particles is shown in Table 8 below. The water content of the third quartz particles was 13%.

[0147] Table 8. Content of various impurity elements in the third quartz particles (unit: μg / g)

[0148] 34.3 5.3 8.4 22.2 - 0.7 - - 0.50 3.4 1.0 0.5 0.9 0.8 1.5 79.5

[0149] (5) Mix ammonium sulfate and the third quartz particles at a mass ratio of 0.2, mix them evenly, and place them in a high-temperature roasting furnace equipped with a gas collection device. Roast at 500°C for 100 min to obtain the fourth quartz particles.

[0150] (6) Acid leaching of the fourth quartz particles under normal pressure: A second acid leaching solution is prepared in an acid-resistant reactor equipped with a heating and stirring device. The molar concentration of hydrofluoric acid in the second acid leaching solution is 1.5 mol / L and the molar concentration of hydrochloric acid is 0.8 mol / L. The hot fourth quartz particles after the second calcination treatment are added to the acid-resistant reactor equipped with a stirring device. The reactor is kept under stirring and the amount and rate of addition of the fourth quartz particles are controlled so that the acid solution temperature in the reactor is maintained at 85℃. The total amount of fourth quartz particles added is 0.8 kg / L of solid-liquid ratio to the second acid leaching solution. After the fourth quartz particles are added, the reactor is stirred continuously for 0.5 h.

[0151] (7) The product of atmospheric pressure acid leaching is filtered and washed until the pH of the filtrate is 7. The filtered product is dried at 105℃ for 24h to obtain high-purity quartz. The atmospheric pressure acid leaching filtrate is recycled to pressurized acid leaching after adding 3mol / L hydrofluoric acid, 0.6mol / L oxalic acid, 0.4mol / L hydrochloric acid and 0.5mol / L nitric acid.

[0152] The high-purity quartz product was tested using the silicon tetrafluoride volatilization method according to the national standard GB / T32649—2016, and the purity was 99.996%. The content of each element in the high-purity quartz product is shown in Table 9 below.

[0153] Table 9. Content of various impurity elements in high-purity quartz products (unit: μg / g)

[0154] 18.6 0.5 4.6 4.1 - 0.2 - - 0.04 0.8 0.5 0.9 0.9 0.6 0.5 31.34

[0155] Where: - indicates that it is below the ICP detection limit, i.e., ≤0.006.

[0156] Example 4

[0157] The quartz sample selected for the experiment in this embodiment was powdered quartz, and the XRD results of the raw quartz ore are as follows: Figure 2 As shown in the figure, the raw quartz ore mainly contains quartz and talc. The XRF analysis results of the raw ore are shown in Table 10, which shows that the main impurity elements in the raw ore are Mg, Al, Ca, etc.

[0158] Table 10 Main Chemical Components of Raw Quartz Ore

[0159] content(%) 97.85 1.12 0.21 0.10 0.05 0.02

[0160] Note: Elements not listed indicate that their content is less than 0.01%.

[0161] like Figure 3 As shown, the method for preparing high-purity quartz in this embodiment includes the following steps:

[0162] (1) The quartz ore was crushed by a gyratory crusher, and after grinding and screening, coarse quartz particles of -50 mesh to +200 mesh were obtained.

[0163] (2) Reverse flotation of coarse quartz particles: The coarse quartz particles are adjusted into a slurry with industrial water and the slurry concentration is 30%; the pH of the slurry is adjusted to 2.5 with hydrofluoric acid; the collector is dodecylamine and the amount of collector is 150g / t; the slurry is placed in an aerated stirred flotation machine, air is introduced and stirred, the air introduction rate is 160L / h, and the scraper is started to continuously scrape off the upper layer of foam until the flotation endpoint is reached; the flotation concentrate is collected and washed with water until the pH of the filtrate is 7, and the first quartz particles are obtained after filtration.

[0164] (3) The first quartz particle is placed in a heating furnace with a quartz glass or ceramic lining and activated and calcined at 900°C for 4 hours. After the reaction is completed, the second quartz particle is obtained.

[0165] (4) The second quartz particles were subjected to hot-press acid leaching: the solid-liquid ratio of the acid leaching solution was 0.75 kg / L; the molar concentrations of hydrofluoric acid, oxalic acid, hydrochloric acid, and nitric acid in the acid leaching solution were 1 mol / L, 0.2 mol / L, 0.8 mol / L, and 0.5 mol / L; the acid leaching temperature was 110℃; the acid leaching time was 1 h; after the acid leaching reaction was completed, the acid leaching product was filtered and washed until the pH of the filtrate was 7. The filter residue was washed and dried to obtain the third quartz particles. The content of each impurity element in the third quartz particles is shown in Table 11 below. The water content of the third quartz particles was 15%.

[0166] Table 11. Content of various impurity elements in the third quartz particles (unit: μg / g)

[0167] 32.2 3.5 7.4 15.2 - 0.8 - - 0.8 1.0 0.8 0.8 0.7 0.7 1.2 65.1

[0168] (5) Mix ammonium sulfate and the third quartz particles at a mass ratio of 0.3, mix them evenly, and place them in a high-temperature roasting furnace equipped with a gas collection device. Roast at 450°C for 120 minutes to obtain the fourth quartz particles.

[0169] (6) Acid leaching of the fourth quartz particles under normal pressure: A second acid leaching solution is prepared in an acid-resistant reactor equipped with a heating and stirring device. The molar concentration of hydrofluoric acid in the second acid leaching solution is 2 mol / L, and the molar concentration of hydrochloric acid is 1 mol / L. The hot fourth quartz particles after the second calcination treatment are added to the acid-resistant reactor equipped with a stirring device. The reactor is kept in a stirring state, and the amount and rate of addition of the fourth quartz particles are controlled so that the temperature of the acid solution in the reactor is kept at 90℃. The total amount of the fourth quartz particles added is 0.5 kg / L of the solid-liquid ratio of the second acid leaching solution. After the fourth quartz particles are added, the reactor is stirred continuously for 3 hours.

[0170] (7) The product of atmospheric pressure acid leaching is filtered and washed until the pH of the filtrate is 6.5. The filtered product is dried at 105℃ for 24h to obtain high-purity quartz. The atmospheric pressure acid leaching filtrate is recycled to pressurized acid leaching after adding 1mol / L hydrofluoric acid, 0.8mol / L oxalic acid, 0.3mol / L hydrochloric acid and 0.8mol / L nitric acid.

[0171] The high-purity quartz product was tested using the silicon tetrafluoride volatilization method according to the national standard GB / T32649—2016, and the purity was 99.998%. The content of each element in the high-purity quartz product is shown in Table 12 below.

[0172] Table 12 Content of various impurity elements in high-purity quartz products (unit: μg / g)

[0173] 10.8 0.7 2.4 2.5 - 0.3 - - 0.1 1.1 - 0.4 0.5 - 0.8 19.6

[0174] Where: - indicates that it is below the ICP detection limit, i.e., ≤0.006.

[0175] Example 5

[0176] The quartz sample selected for the experiment in this embodiment was vein quartz. The XRF analysis results of the raw ore are shown in Table 13. It can be seen that the main impurity elements of the raw ore are Mg, Al, Ca, Fe, etc.

[0177] Table 13 Main Chemical Components of Raw Quartz Ore

[0178] content(%) 97.59 0.35 1.80 0.05 0.02 0.02 0.01 0.16

[0179] Note: Elements not listed indicate that their content is less than 0.01%.

[0180] like Figure 3 As shown, the preparation method of high-purity quartz in this embodiment includes the following steps:

[0181] (1) The raw quartz ore was crushed using a cone crusher, and after grinding and screening, coarse quartz particles of -50 mesh to +200 mesh were obtained.

[0182] (2) Reverse flotation of coarse quartz particles: The coarse quartz particles are adjusted into a slurry with industrial water and the slurry concentration is 40%; the pH of the slurry is adjusted to 2.0 with hydrofluoric acid; the collector is dodecylamine and the amount of collector is 200g / t; the slurry is placed in an aerated stirred flotation machine, air is introduced and stirred, the air introduction rate is 120L / h, and the scraper is started to continuously scrape off the upper layer of foam until the flotation endpoint is reached; the flotation concentrate is collected and washed with water until the pH of the filtrate is 7, and the first quartz particles are obtained after filtration.

[0183] (3) The first quartz particle is placed in a heating furnace with a quartz glass or ceramic lining and activated and calcined at 1100℃ for 3 hours. After the reaction is completed, the second quartz particle is obtained.

[0184] (4) The second quartz particles were subjected to hot-press acid leaching: the solid-liquid ratio of the acid leaching solution was 0.1 kg / L; the molar concentrations of hydrofluoric acid, oxalic acid, hydrochloric acid, and nitric acid in the acid leaching solution were 3 mol / L, 0.3 mol / L, 1 mol / L, and 0.2 mol / L; the acid leaching temperature was 150℃; the acid leaching time was 2 h; after the acid leaching reaction was completed, the acid leaching product was filtered and washed until the pH of the filtrate was 7. The filter residue was washed and dried to obtain the third quartz particles. The content of each impurity element in the third quartz particles is shown in Table 14 below, and the water content of the third quartz particles is 15%.

[0185] Table 14. Content of various impurity elements in the third quartz particles (unit: μg / g)

[0186] 53.2 7.5 9.4 20.3 - 0.9 - - 0.7 1.2 0.9 0.8 0.6 0.7 1.5 97.7

[0187] (5) Mix ammonium sulfate and the third quartz particles at a mass ratio of 0.1, mix them evenly, and place them in a high-temperature roasting furnace equipped with a gas collection device. Roast at 550°C for 60 minutes to obtain the fourth quartz particles.

[0188] (6) Acid leaching of the fourth quartz particles under normal pressure: A second acid leaching solution is prepared in an acid-resistant reactor equipped with a heating and stirring device. The molar concentration of hydrofluoric acid in the second acid leaching solution is 2 mol / L, and the molar concentration of hydrochloric acid is 0.2 mol / L. The hot fourth quartz particles after the second calcination treatment are added to the acid-resistant reactor equipped with a stirring device. The reactor is kept in a stirring state, and the amount and speed of the fourth quartz particles added are controlled so that the acid temperature in the reactor is maintained at 80℃. The total amount of the fourth quartz particles added is 1 kg / L of the solid-liquid ratio of the second acid leaching solution. After the fourth quartz particles are added, the reactor is stirred continuously for 2 hours.

[0189] (7) The product of atmospheric pressure acid leaching is filtered and washed until the pH of the filtrate is 7. The filtered product is dried at 105℃ for 24h to obtain high-purity quartz. The atmospheric pressure acid leaching filtrate is recycled to pressurized acid leaching after adding 1.5mol / L hydrofluoric acid, 0.8mol / L oxalic acid, 0.5mol / L hydrochloric acid and 0.8mol / L nitric acid.

[0190] The high-purity quartz product was tested using the silicon tetrafluoride volatilization method according to the national standard GB / T32649—2016, and the purity was 99.995%. The content of each element in the high-purity quartz product is shown in Table 15 below.

[0191] Table 15 Content of various impurity elements in high-purity quartz products (unit: μg / g)

[0192] 15.6 3.5 8.4 4.9 - 0.2 - - 1.5 1.8 0.1 1.4 0.5 1.2 0.9 40.0

[0193] Where: - indicates that it is below the ICP detection limit, i.e., ≤0.006.

[0194] In summary, this invention employs a combined process of activation calcination, hot-press acid leaching, additive calcination, and atmospheric pressure acid leaching to achieve efficient purification of quartz. This process effectively removes lattice impurities and inert impurities that are difficult to remove in conventional processes. Furthermore, the calcination additives used are environmentally friendly, consume little acid, and produce high-purity products, thus effectively solving the problems of high difficulty and high acid consumption in deep purification of quartz in existing technologies.

[0195] 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 using a combined two-stage roasting-acid leaching process, characterized in that, The method includes the following steps: The raw quartz ore is pretreated to obtain the first quartz particles; The first quartz particle is calcined for the first time to obtain the second quartz particle; The second quartz particle was subjected to a first acid leaching to obtain the third quartz particle; The third quartz particles are mixed with a calcination aid and then calcined a second time to obtain the fourth quartz particles. The fourth quartz particle was subjected to a second acid leaching, followed by water washing and drying to obtain the high-purity quartz. The first acid leaching is a hot-press acid leaching, and the temperature of the first acid leaching treatment is 110℃~180℃, and the time is 0.5h~2h; The first acid leaching includes the following steps: A first acid leaching solution is prepared in a reaction vessel, wherein the molar concentration of hydrofluoric acid is 1 mol / L to 4 mol / L, the molar concentration of oxalic acid is 0.2 mol / L to 0.4 mol / L, the molar concentration of hydrochloric acid is 0.5 mol / L to 1 mol / L, and the molar concentration of nitric acid is 0.2 mol / L to 0.5 mol / L. The moisture content of the third quartz particle is 10%~15%; The second roasting includes the following steps: The calcination aid is added to the third quartz particles and stirred evenly to obtain a first wet mixture; The first wet mixture was placed at a temperature of 450℃~550℃ and heated for 60min~120min to obtain the fourth quartz particles; The calcination aid is present in a mass ratio of 0.1 to 0.3 to the third quartz particles, and the calcination aid includes one or both of ammonium sulfate and ammonium bisulfate. The second acid leaching is an atmospheric pressure acid leaching, which includes the following steps: A second acid leaching solution is prepared in the reaction vessel, wherein the molar concentration of hydrofluoric acid in the second acid leaching solution is 0.8 mol / L to 2 mol / L, and the molar concentration of hydrochloric acid is 0.2 mol / L to 1 mol / L.

2. The method for preparing high-purity quartz using a combined two-calcination-acid leaching process according to claim 1, characterized in that, The pretreatment includes: crushing, grinding, and screening the quartz ore to obtain coarse quartz particles, and performing reverse flotation on the coarse quartz particles to obtain the first quartz particles, wherein the particle size of the coarse quartz particles is +200 mesh to -50 mesh.

3. The method for preparing high-purity quartz using a combined two-calcination-acid leaching process according to claim 2, characterized in that, The reverse flotation includes the following steps: The coarse quartz particles are prepared into a slurry with a concentration of 20% to 50%. The pH value of the slurry is adjusted to 1.0-2.5, and a collector is added to the slurry for reverse flotation treatment; Collect the reverse flotation concentrate and wash it with water until the pH of the filtrate is 6.5-7. After filtering and drying, the first quartz particles are obtained. The added collector is one or more cationic amine collectors, and the amount of the collector added is 100g / t to 200g / t.

4. The method for preparing high-purity quartz using a combined two-calcination-acid leaching process according to claim 1, characterized in that, The first calcination is an activation calcination, which includes: calcining the first quartz particles at a temperature of 900℃~1100℃ for 0.5h~4h to obtain the second quartz particles.

5. The method for preparing high-purity quartz using a combined two-calcination-acid leaching process according to claim 1, characterized in that, The first acid leaching also includes the following steps: The second quartz particles are added to the first acid leaching solution for the first acid leaching treatment, and the solid-liquid ratio of the second quartz particles to the first acid leaching solution is 0.5 kg / L to 1 kg / L. The product of the first acid leaching treatment is filtered and washed until the pH of the filtrate is 6.5-7 to obtain the third quartz particles.

6. The method for preparing high-purity quartz using a combined two-calcination-acid leaching process according to claim 1, characterized in that, The second acid leaching also includes the following steps: The hot fourth quartz particles after the second calcination treatment are added to the reactor, and the amount and rate of addition of the fourth quartz particles are controlled to keep the acid leaching temperature in the reactor at 80℃~90℃. The total amount of the fourth quartz particles added is 0.5kg / L~1kg / L to the solid-liquid ratio of the second acid leaching solution. After the fourth quartz particle is added, continue stirring and reacting for 0.5h~3h. The product of the second acid leaching treatment is filtered, washed until the pH of the filtrate is 7, and dried to obtain the high-purity quartz.

7. The method for preparing high-purity quartz using a combined two-calcination-acid leaching process according to claim 1, characterized in that, The acid leaching filtrate from the second acid leaching is diluted or mixed with acid and then recycled back to the first acid leaching for reuse. The mixed acid is one or more of hydrofluoric acid, hydrochloric acid, oxalic acid, and nitric acid. The heating furnaces used for the first and second roasting are equipped with exhaust gas spray collection devices. The spray liquid used by the exhaust gas spray collection devices is industrial water, which is used for the pretreatment.

8. A high-purity quartz, characterized in that, The high-purity quartz is prepared by a combined calcination-acid leaching process as described in any one of claims 1 to 7. The high-purity quartz contains less than 20 ppm Al, less than 1 ppm Na, less than 1 ppm K, and 99.99% to 99.998% SiO2.

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