A high-purity quartz sand based on acid leaching treatment and its preparation method

Abstract

This invention relates to the field of high-purity quartz sand technology, specifically to a high-purity quartz sand based on acid leaching treatment and its preparation method, comprising the following steps: rapidly cooling quartz sand after calcination; adding the pretreated quartz sand to a first-stage acid leaching solution; after the reaction, washing and drying the quartz sand to obtain the first-stage acid-leached quartz sand; adding the first-stage acid-leached quartz sand to a second-stage acid leaching solution; and after the reaction, obtaining high-purity quartz sand. This invention employs a two-stage functionalized composite acid leaching system. The first-stage acid leaching solution uses a compound of oxalic acid, ammonium fluoride, fluorosilicic acid, and acetylacetone to gently complex and remove surface alkali metal, iron, and titanium impurities. The second-stage acid leaching solution uses salicylic acid esterification products, choline chloride, and betaine to construct a deep impurity removal system, precisely removing lattice-state aluminum, calcium, and magnesium impurities. The two stages synergistically achieve progressive deep purification without excessive corrosion of the quartz matrix, overcoming the shortcomings of traditional strong acids, such as poor selectivity and easy damage to the quartz structure.

Description

Technical Field

[0001] This invention relates to the field of high-purity quartz sand technology, specifically to a high-purity quartz sand based on acid leaching treatment and its preparation method. Background Technology

[0002] High-purity quartz sand is a core basic material in photovoltaics, electronic information, high-end optics, semiconductor lighting and other fields. Its SiO2 purity, impurity content and structural integrity directly determine the performance and service life of downstream products. At present, the industrial production of high-purity quartz sand mainly uses natural quartz ore as raw material. Impurities such as aluminum, iron, calcium, magnesium and alkali metals in the quartz lattice and surface are removed through processes such as crushing, roasting, magnetic separation and acid leaching to achieve mineral purification.

[0003] Traditional leaching systems often rely on strong inorganic acids such as hydrofluoric acid and hydrochloric acid. Although they have a certain dissolving effect, their reactions are violent and their selectivity is poor, which can easily cause excessive corrosion of the quartz matrix and environmental safety hazards. Therefore, in response to the problems mentioned above, this invention proposes a high-purity quartz sand based on acid leaching treatment and its preparation method. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a high-purity quartz sand based on acid leaching treatment and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing high-purity quartz sand based on acid leaching treatment includes the following steps: S1. After crushing the raw quartz ore, the quartz sand with a particle size range of 60-140 mesh is obtained by screening. The quartz sand is roasted at 800-900℃ for 2-3 hours. After roasting, it is rapidly cooled. The water-quenched and dried quartz sand is then passed through a 1.2-1.5T strong magnetic separator to remove strong magnetic impurities such as magnetite and hematite. S2. Add the pretreated quartz sand to a first-stage acid leaching solution and stir at a constant temperature of 80-90℃ for 3-4 hours. After the reaction is completed, perform solid-liquid separation and collect the filtrate. The obtained quartz sand filter cake is repeatedly washed with deionized water at 80-90℃ until the pH of the washing solution is neutral. After washing, the quartz sand is dried at 100-110℃ for 1.5-2 hours to obtain the first-stage acid-leached quartz sand. S3. Add the first-stage acid-leached quartz sand to the second-stage acid-leaching solution and stir at a constant temperature of 80-90℃ for 3-4 hours. After the reaction is completed, collect the filtrate. The resulting quartz sand filter cake is first washed with ethanol aqueous solution 2-3 times, and then washed with deionized water until the conductivity of the washing solution is ≤5μS / cm. After washing, the quartz sand is dried at 100-110℃ for 3-4 hours to obtain high-purity quartz sand. One of the acid leaching solutions is prepared through the following steps: S21. Add oxalic acid to deionized water and stir to dissolve. Then add ammonium fluoride and ascorbic acid, stir evenly, and then add fluorosilicic acid solution. React at 20-30℃ for 3-4 hours. S22. After the reaction is complete, acetylacetone is added dropwise while stirring. After the addition is complete, deionized water is added and mixed to obtain a transparent solution. S23. Adjust the pH of the transparent solution to 2.5-3.0 with dilute hydrochloric acid to obtain an acid leaching solution.

[0006] Furthermore, the second-stage acid leaching solution in step S3 is prepared through the following steps: S31. Mix salicylic acid with methanol and stir at 40-60℃ for 1-2 hours for esterification. Then add choline chloride and stir at 70-90℃ for 30-60 minutes to form a precursor solvent. S32. Dilute the precursor solvent with deionized water, then add betaine and ultrasonically disperse at 30-50℃ for 10-20 min to obtain the functionalized diluent. S33. Add dilute hydrochloric acid to the functionalized diluent to adjust the pH to 1.5-2.0, and add methanol to obtain the second-stage acid leaching solution.

[0007] Furthermore, in step S2, the mass ratio of the pretreated quartz sand to the first acid leaching solution is 1:(3-5).

[0008] Furthermore, in step S3, the mass ratio of the first stage acid-leached quartz sand to the second stage acid-leaching solution is 1:(3-5), and the ethanol aqueous solution is composed of ethanol and deionized water in a mass ratio of 1:(1-2).

[0009] Furthermore, in step S21, the mass ratio of deionized water, oxalic acid, ammonium fluoride, ascorbic acid, and fluorosilicic acid solution is 100:(8-15):(3-8):(1-3):(10-20). The fluorosilicic acid solution is composed of fluorosilicic acid and deionized water in a mass ratio of 1:(2-3).

[0010] Furthermore, in step S22, the mass ratio of acetylacetone to deionized water in step S21 is (2-5):100, and the mass fraction of deionized water in the transparent solution is 45-55%.

[0011] Furthermore, in step S31, the mass ratio of salicylic acid, methanol and choline chloride is 10:(20-40):(3-6).

[0012] Furthermore, in step S32, the mass ratio of the precursor solvent, deionized water, and betaine is 10:(20-30):(1-2); and in step S33, the mass fraction of methanol in the second-stage acid leaching solution is 5-15%.

[0013] Furthermore, the rapid cooling step in step S1 is as follows: Pour the calcined quartz sand into deionized water at a mass ratio of 1:(2-5) and a temperature of 20-30℃. Stir continuously during the pouring process until the temperature of the quartz sand drops below 40℃.

[0014] Furthermore, a high-purity quartz sand based on acid leaching treatment, wherein the high-purity quartz sand is prepared according to the preparation method described above.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention employs a two-stage functionalized composite acid leaching system. The first stage acid leaching solution is a compound of oxalic acid, ammonium fluoride, fluorosilicic acid, and acetylacetone, which gently complexes and removes alkali metal, iron, and titanium impurities from the surface. The second stage acid leaching solution is a deep purification system constructed with salicylic acid esterification products, choline chloride, and betaine, which precisely removes lattice-state aluminum, calcium, and magnesium impurities. The two stages work together to achieve progressive deep purification without excessive corrosion of the quartz matrix, overcoming the defects of traditional strong acids, such as poor selectivity and easy damage to the quartz structure. 2. This invention uses high-temperature roasting, water quenching and rapid cooling, and strong magnetic separation pretreatment to create microcracks in the quartz sand and expose internal impurities, thereby removing strongly magnetic minerals in advance, significantly reducing the subsequent acid leaching pressure, avoiding ineffective acid consumption, and solving the problems of insufficient impurity exposure and low purification efficiency in traditional processes. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation process of high-purity quartz sand in this invention; Figure 2 This is a schematic diagram of the preparation process of a section of the acid leaching solution in this invention; Figure 3 This is a schematic diagram of the preparation process of the two-stage acid leaching solution in this invention; Figure 4 This is a scanning electron microscope image of the quartz sand before the first acid leaching in Example 1; Figure 5 This is a scanning electron microscope image of the quartz sand after the first acid leaching in Example 1; Figure 6 This is a scanning electron microscope image of the quartz sand after the second acid leaching in Example 1; Figure 7 The image shows a scanning electron microscope image of the quartz sand in Comparative Example 1 after the second acid leaching. Figure 8The image shows a scanning electron microscope image of the quartz sand in Comparative Example 2 after the second acid leaching. Figure 9 The image shows a scanning electron microscope image of the quartz sand in Comparative Example 3 before the first acid leaching. Figure 10 The image shows a scanning electron microscope image of the quartz sand in Comparative Example 3 after the first acid leaching. Figure 11 This is a scanning electron microscope image of the quartz sand in Comparative Example 3 after the second acid leaching. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figures 1-11 The present invention provides a technical solution: Example 1: A method for preparing high-purity quartz sand based on acid leaching treatment includes the following steps: I. Quartz Sand Pretreatment: S1. Take quartz ore, crush and screen to obtain 1000g of 60-mesh quartz sand, roast at 800℃ for 2h, immediately pour into 2000g of 20℃ deionized water, rapidly cool and stir to below 40℃, dry and then remove strong magnetic impurities by a 1.2T strong magnetic separator. II. Preparation of a first-stage acid leaching solution: S21. Add 80g of oxalic acid to 1000g of deionized water and stir to dissolve. Then add 30g of ammonium fluoride and 10g of ascorbic acid, stir evenly, and then add 100g of fluorosilicic acid solution (composed of 33.3g of fluorosilicic acid and 66.7g of deionized water). React at 20℃ for 3 hours. S22. Add 20g of acetylacetone dropwise while stirring. After the addition is complete, add deionized water until the mass fraction of deionized water in the clear solution is 45%. S23. Adjust the pH to 2.5 with dilute hydrochloric acid to obtain an acid leaching solution; III. First acid soaking: S2. Add 100g of pretreated quartz sand to 300g of first-stage acid leaching solution, stir and react at 80℃ for 3h, after solid-liquid separation, wash with 80℃ deionized water until neutral, and dry at 100℃ for 1.5h to obtain the first-stage acid-leached quartz sand. IV. Preparation of the two-stage acid leaching solution: S31. Mix 100g of salicylic acid with 200g of methanol and esterify at 40℃ for 1h. Add 30g of choline chloride and stir at 70℃ for 30min to form a precursor solvent. S32. Take 100g of precursor solvent, 200g of deionized water, and 10g of betaine, and ultrasonically disperse them at 30℃ for 10min to obtain a functionalized diluent. S33. Adjust the pH of the functionalized diluent to 1.5 with dilute hydrochloric acid, and add methanol until the methanol mass fraction of the system is 5% to obtain the second-stage acid leaching solution. V. Second acid leaching: S3. Add 100g of the first stage acid-leached quartz sand to 300g of the second stage acid-leaching solution, stir and react at 80℃ for 3h, after solid-liquid separation, wash twice with ethanol aqueous solution (ethanol:deionized water = 1:1), then wash with deionized water until the conductivity is ≤5μS / cm, and dry at 100℃ for 3h to obtain high-purity quartz sand.

[0019] Example 2: A method for preparing high-purity quartz sand based on acid leaching treatment includes the following steps: I. Quartz Sand Pretreatment: S1. Take quartz ore, crush and screen to obtain 1000g of 100-mesh quartz sand, roast at 850℃ for 2.5h, immediately pour into 3500g of 25℃ deionized water for rapid cooling and stirring to below 40℃, dry and then remove strong magnetic impurities by a 1.4T strong magnetic separator. II. Preparation of a first-stage acid leaching solution: S21. Add 120g of oxalic acid to 1000g of deionized water and stir to dissolve. Then add 50g of ammonium fluoride and 20g of ascorbic acid. Stir well and then add 150g of fluorosilicic acid solution (composed of 42.8g of fluorosilicic acid and 107.2g of deionized water). React at 25℃ for 3.5h. S22. Add 35g of acetylacetone dropwise while stirring. After the addition is complete, add deionized water until the mass fraction of deionized water in the clear solution is 50%. S23. Adjust the pH to 2.8 with dilute hydrochloric acid to obtain an acid leaching solution; III. First acid soaking: S2. Add 100g of pretreated quartz sand to 400g of first-stage acid leaching solution, stir and react at 85℃ for 3.5h, after solid-liquid separation, wash with deionized water at 85℃ until neutral, and dry at 105℃ for 1.8h to obtain the first-stage acid-leached quartz sand. IV. Preparation of the two-stage acid leaching solution: S31. Mix 100g of salicylic acid with 300g of methanol and esterify at 50℃ for 1.5h. Add 45g of choline chloride and stir at 80℃ for 45min to form a precursor solvent. S32. Take 100g of precursor solvent, 250g of deionized water and 15g of betaine, and ultrasonically disperse them at 40℃ for 15min to obtain a functionalized diluent. S33. Adjust the pH of the functionalized diluent to 1.8 with dilute hydrochloric acid, and add methanol until the methanol mass fraction of the system is 10% to obtain the second-stage acid leaching solution. V. Second acid leaching: S3. Add 100g of the first-stage acid-leached quartz sand to 400g of the second-stage acid-leaching solution, stir and react at 85℃ for 3.5h. After solid-liquid separation, wash twice with an ethanol-water solution (ethanol:deionized water = 1:1.5), and then wash with deionized water until the conductivity is ≤5μS / cm. Dry at 105℃ for 3.5h to obtain high-purity quartz sand.

[0020] Example 3: A method for preparing high-purity quartz sand based on acid leaching treatment includes the following steps: I. Quartz Sand Pretreatment: S1. Take 1000g of 140-mesh quartz sand from the raw quartz ore by crushing and screening. Roast it at 900℃ for 3 hours. Immediately after roasting, pour it into 5000g of 30℃ deionized water and cool it rapidly while stirring until it reaches below 40℃. After drying, remove strong magnetic impurities by passing it through a 1.5T strong magnetic separator. II. Preparation of a first-stage acid leaching solution: S21. Add 150g of oxalic acid to 1000g of deionized water and stir to dissolve. Then add 80g of ammonium fluoride and 30g of ascorbic acid. Stir well and then add 200g of fluorosilicic acid solution (composed of 50g of fluorosilicic acid and 150g of deionized water). React at 30℃ for 4 hours. S22. Add 50g of acetylacetone dropwise while stirring. After the addition is complete, add deionized water until the mass fraction of deionized water in the clear solution is 55%. S23. Adjust the pH to 3.0 with dilute hydrochloric acid to obtain an acid leaching solution; III. First acid soaking: S2. Add 100g of pretreated quartz sand to 500g of first-stage acid leaching solution, stir and react at 90℃ for 4h, after solid-liquid separation, wash with 90℃ deionized water until neutral, and dry at 110℃ for 2h to obtain the first-stage acid-leached quartz sand.

[0021] IV. Preparation of the two-stage acid leaching solution: S31. Mix 100g of salicylic acid with 400g of methanol and esterify at 60℃ for 2h. Add 60g of choline chloride and stir at 90℃ for 60min to form a precursor solvent. S32. Take 100g of precursor solvent, 300g of deionized water, and 20g of betaine, and ultrasonically disperse them at 50℃ for 20min to obtain a functionalized diluent. S33. Adjust the pH of the functionalized diluent to 2.0 with dilute hydrochloric acid, and add methanol until the methanol mass fraction of the system is 10% to obtain the second-stage acid leaching solution. V. Second acid leaching: S3. Add 100g of the first-stage acid-leached quartz sand to 500g of the second-stage acid-leaching solution, stir and react at 90℃ for 4h. After solid-liquid separation, wash 3 times with ethanol-water solution (ethanol:deionized water = 1:2), then wash with deionized water until the conductivity is ≤5μS / cm, and dry at 110℃ for 4h to obtain high-purity quartz sand.

[0022] Comparative Example 1: Compared to Example 1, Comparative Example 1 replaced one section of the acid leaching solution with an equal mass of ammonium fluoride-oxalic acid leaching solution (the mass ratio of ammonium fluoride to oxalic acid was 1:1), and the remaining steps were exactly the same as in Example 1.

[0023] Comparative Example 2: Compared to Example 1, Comparative Example 2 replaced the two-stage acid leaching solution with an equal mass of salicylic acid-methanol acid leaching solution (the mass ratio of salicylic acid to methanol was 1:1), and the remaining steps were exactly the same as in Example 1.

[0024] Comparative Example 3: Compared to Example 1, Comparative Example 3 replaced the first stage of the acid leaching solution with an equal mass of ammonium fluoride-oxalic acid leaching solution, and replaced the second stage of the acid leaching solution with an equal mass of salicylic acid-methanol leaching solution. The remaining steps were exactly the same as in Example 1.

[0025] The high-purity quartz sand samples prepared in Example 1 and Comparative Examples 1-3 were subjected to the following tests: I. Purity and Impurity Detection: X-ray fluorescence spectrometry was used to grind the sample to below 200 mesh and determine the purity of SiO2 and the content of impurities such as Al2O3, TFe, CaO, K2O, and Na2O.

[0026] Table 1 shows the XRF test results of the first section of acid-leached quartz sand in Example 1. Table 1 The data in Table 1 shows that the main components and impurities in quartz are as follows: The main component of quartz is SiO2, which accounts for 98.87% of the mass percentage, indicating that the acid leaching treatment effectively preserves the purity of quartz. The contents of impurity components Al2O3, CaO and K2O are 0.38%, 0.29% and 0.16% respectively. These are common impurity elements in quartz. In the subsequent mineral purification process, sodium (Na2O) and potassium (K2O) will become new removal targets. In this data, sodium accounts for 0.05% by mass, while potassium accounts for 0.16%. These small-radius elements (such as Na) + and K + They have strong solubility, especially in acidic solutions, where they can readily react with acids to form soluble salts, such as sodium chloride (NaCl) or potassium chloride (KCl). Due to their high solubility, these small-radius ions are usually the preferred targets for dissolution during acid leaching.

[0027] Table 2 shows the XRF test results of the high-purity quartz sand in Example 1; Table 2 The data in Table 2 show that the mass fraction of SiO2 was 99.592%, indicating that the quartz purity after acid leaching was extremely high. The acid leaching process caused almost no damage to the main mineral components. The contents of major impurity elements such as Al2O3, Fe2O3, SO3, and Cl were all kept below 0.3%, indicating that acid leaching had a significant effect on removing aluminum impurities. The P2O5 content was close to the detection limit in the test, indicating that phosphorus was almost completely removed. The content of Fe2O3 also decreased slightly, showing that sulfur and iron impurities were effectively dissolved and migrated. Overall, the two-stage acid leaching process not only significantly reduced the impurity content but also showed good stability and repeatability, providing a reliable experimental basis for subsequent high-purity quartz purification.

[0028] Table 3 shows the XRF test results of the quartz sand in Comparative Examples 1-3: Table 3: As can be seen from the data in Table 3, in Comparative Example 1 (only one stage of acid leaching solution was replaced): the SiO2 purity was only 93.36%, and the residual amounts of Al2O3 and CaO impurities were the highest, indicating the least thorough removal of impurities; in Comparative Example 2 (only two stages of acid leaching solution were replaced): the SiO2 purity increased to 96.50%, but the iron, aluminum, and calcium impurities were still significantly higher than in the composite acid leaching system; in Comparative Example 3 (both stages of acid leaching solution were replaced simultaneously): the SiO2 purity reached 97.80%, and the content of various impurities was lower than in the single replacement group, proving that the combination of two stages of acid leaching can remove metal impurities more deeply than a single acid leaching system; the customized one-stage + two-stage acid leaching solution used in Example 1 of this invention, compared with the conventional acid leaching systems of Comparative Examples 1-3, can increase the SiO2 purity to 99.592%, and significantly reduce the residual amounts of key impurities such as aluminum, iron, calcium, and alkali metals, with a purification effect far superior to conventional acid leaching formulas.

[0029] II. Conductivity test: Weigh 10.00g of sample, add 50mL of ultrapure water, shake at 25℃ for 30min, filter, and measure the conductivity of the filtrate using a conductivity meter.

[0030] III. Total Impurity Removal Rate: Based on the total amount of impurities in the raw ore, calculated using the formula: Total Impurity Removal Rate (%) = (Total amount of impurities in the raw ore) The total impurities in the sample are calculated as (total impurities in the sample) / total impurities in the raw ore × 100%. The specific test results are shown in Table 4 below. Table 4 As can be seen from the data in Table 4, the conductivity of Examples 1-3 is only 3.9-4.5 μS / cm, which is much lower than that of Comparative Examples 1-3 (12.5-18.3 μS / cm), indicating that there are very few soluble ions remaining in the product, and the washing and purification effects meet the standards. Comparative Example 3 has the highest conductivity, indicating that conventional first-stage and second-stage acid leaching solutions cannot effectively remove soluble impurities, and the ion residue is serious. The total impurity removal rate of Examples 1-3 reaches 98.3%-99.2%, which is close to complete removal. Comparative Example 1 is only 93.6%, Comparative Example 2 is 90.2%, and Comparative Example 3 is 85.7%, all of which are significantly lower than that of Examples 1-3. Examples 1-3 prove that the two-stage composite acid leaching process and special acid leaching solution formula of the present invention can achieve more efficient and thorough impurity removal.

[0031] Figure 4-6 The images shown are scanning electron microscope (SEM) images of the quartz sand before, after, and after the second acid leaching in Example 1. Figure 4 The image shows the SEM image of the raw quartz sand before the first acid leaching. The surface of the quartz sand is rough, with obvious cracks, depressions and stepped fractures. The overall surface is uneven, and a large number of bright white / light gray impurity spots are distributed on the surface of the particles and in the cracks. This indicates that there are many heavy element impurities such as iron, titanium and alkali metals in the raw quartz sand, and some of the impurities are wrapped on the surface of the quartz particles and in the cracks. Figure 5 The image shows the SEM image after the first acid leaching. Compared to the raw material, the surface of the quartz sand is significantly smoother. Most of the depressions and rough areas have been flattened, most of the impurities attached to the surface have been removed, and the number of bright white impurities has been greatly reduced. Only a small number of high-brightness impurity particles remain in a few places, indicating that the first acid leaching effectively removed most of the surface-attached impurities and easily soluble impurities in the cracks. Figure 6 The SEM image of the final high-purity quartz sand after the second acid leaching shows that the quartz sand surface is highly smooth and dense, with clear and uniform cleavage surfaces, no obvious corrosion pits, cracks or rough areas, and almost no obvious bright white impurity points. The residual trace impurity signal is extremely weak, indicating that lattice impurities and impurities deep in the cracks have been deeply removed. The overall background is clean, and there is no impurity agglomeration between particles, indicating that the two acid leaching processes have achieved efficient removal of surface and internal impurities.

[0032] Figure 7The image shown is a scanning electron microscope (SEM) image of the quartz sand after the second acid leaching in Comparative Example 1. After replacing the first-stage acid leaching solution with an ammonium fluoride-oxalic acid system, the surface of the quartz sand after the second acid leaching showed obvious non-uniform corrosion marks and micro-pits. In addition, there were still many high atomic number impurity bright spots distributed on the particle surface. This indicates that the conventional ammonium fluoride-oxalic acid first-stage acid leaching solution has poor selectivity. It cannot effectively remove surface and crack impurities, nor can it create good conditions for the second-stage acid leaching. The final product's impurity removal effect and matrix integrity are significantly worse than those in Example 1. The SEM image of the product after the second acid leaching was taken only to focus on the influence of the first-stage acid leaching solution formulation on the final purification effect, and to directly compare the core differences between the process of this invention and the conventional ammonium fluoride-oxalic acid system in terms of impurity removal efficiency and matrix protection, thus eliminating the interference of irrelevant variables.

[0033] Figure 8 The image shown is a scanning electron microscope image of the quartz sand after the second acid leaching in Comparative Example 2. After replacing the second-stage acid leaching solution with a salicylic acid-methanol system, slight non-uniform corrosion marks and edge roughness still remained on the surface of the quartz sand after the second acid leaching. Furthermore, numerous high atomic number impurity bright spots were still distributed on the particle surface. This indicates that the conventional salicylic acid-methanol two-stage acid leaching solution has limited ability to remove residual impurities from the surface and cracks of quartz particles, especially failing to achieve further migration, complexation, and removal of small atomic radius impurities. Simultaneously, this system provides insufficient selective protection to the quartz matrix, easily causing localized corrosion and a decrease in surface integrity. The main function of the second acid leaching is to further remove surface and easily damaged impurities after the first acid leaching. Based on the removal of soluble impurities, the process further targets and deeply removes small atomic radius impurity atoms remaining in quartz lattice defects, microcracks, and weakly bonded areas at the interface. Compared with the conventional salicylic acid-methanol system, the two-stage acid leaching solution can effectively reduce non-selective damage to the Si-O framework while promoting the migration and complexation removal of impurity atoms. This achieves both deep impurity removal and quartz matrix protection. The scanning electron microscope image of the product after the second acid leaching is only taken to focus on the impact of the two-stage acid leaching solution formulation on the final purification effect and matrix protection capability, and to directly compare the core differences between the process of this invention and the conventional salicylic acid-methanol system in terms of small atomic radius impurity removal, surface integrity maintenance, and matrix damage control.

[0034] Figure 9-11 The images show scanning electron microscope (SEM) images of the quartz sand in Comparative Example 3 before, after, and after the first acid leaching. Figure 9 The image shows the SEM image of the raw quartz sand before the first acid leaching. The raw material stage has a high impurity content and many surface defects, which is basically consistent with the initial state of the raw material in Example 1. Figure 10 The image shows the SEM image of the quartz sand after the first acid leaching. It can be seen that only a small amount of surface impurities were removed, and most of the impurities remained on the particle surface, in microcracks and defect areas. This indicates that a single acid leaching is insufficient to effectively remove deep impurities. Figure 11 The image shows a SEM image of the quartz sand after the second acid leaching. Obvious non-uniform corrosion marks are visible on the surface, along with numerous high atomic number impurity bright spots. This indicates that while the conventional two-stage acid leaching process can further target residual impurities, its selective removal capability for small atomic radius impurities is insufficient, and its protection of the quartz matrix is ​​poor, easily causing surface roughening and localized damage. Compared to the final product of Example 1, the conventional two-stage acid leaching process in Comparative Example 3 failed to achieve deep removal of impurities and also failed to effectively maintain the integrity of the quartz particle surface. These results further demonstrate that in the two-stage composite acid leaching process of this invention, the second acid leaching not only enhances the deep removal of small atomic radius impurities but also effectively protects the quartz matrix during the acid leaching process, avoiding excessive corrosion and structural damage. This demonstrates a significant advantage of synergistically combining efficient impurity removal with matrix protection.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-purity quartz sand based on acid leaching treatment, characterized in that, Includes the following steps: S1. After crushing the raw quartz ore, the quartz sand with a particle size range of 60-140 mesh is obtained by screening. The quartz sand is roasted at 800-900℃ for 2-3 hours. After roasting, it is rapidly cooled. The water-quenched and dried quartz sand is then passed through a 1.2-1.5T strong magnetic separator to remove strong magnetic impurities such as magnetite and hematite. S2. Add the pretreated quartz sand to a first-stage acid leaching solution and stir at a constant temperature of 80-90℃ for 3-4 hours. After the reaction is completed, perform solid-liquid separation and collect the filtrate. The obtained quartz sand filter cake is repeatedly washed with deionized water at 80-90℃ until the pH of the washing solution is neutral. After washing, the quartz sand is dried at 100-110℃ for 1.5-2 hours to obtain the first-stage acid-leached quartz sand. S3. Add the first-stage acid-leached quartz sand to the second-stage acid-leaching solution and stir at a constant temperature of 80-90℃ for 3-4 hours. After the reaction is completed, collect the filtrate. The resulting quartz sand filter cake is first washed with ethanol aqueous solution 2-3 times, and then washed with deionized water until the conductivity of the washing solution is ≤5μS / cm. After washing, the quartz sand is dried at 100-110℃ for 3-4 hours to obtain high-purity quartz sand. One of the acid leaching solutions is prepared through the following steps: S21. Add oxalic acid to deionized water and stir to dissolve. Then add ammonium fluoride and ascorbic acid, stir evenly, and then add fluorosilicic acid solution. React at 20-30℃ for 3-4 hours. S22. After the reaction is complete, acetylacetone is added dropwise while stirring. After the addition is complete, deionized water is added and mixed to obtain a transparent solution. S23. Adjust the pH of the transparent solution to 2.5-3.0 with dilute hydrochloric acid to obtain an acid leaching solution; The second-stage acid leaching solution in step S3 is prepared through the following steps: S31. Mix salicylic acid with methanol and stir at 40-60℃ for 1-2 hours for esterification. Then add choline chloride and stir at 70-90℃ for 30-60 minutes to form a precursor solvent. S32. Dilute the precursor solvent with deionized water, then add betaine and ultrasonically disperse at 30-50℃ for 10-20 min to obtain the functionalized diluent. S33. Add dilute hydrochloric acid to the functionalized diluent to adjust the pH to 1.5-2.0, and add methanol to obtain the second-stage acid leaching solution.

2. The method for preparing high-purity quartz sand based on acid leaching treatment according to claim 1, characterized in that, In step S2, the mass ratio of the pretreated quartz sand to the first acid leaching solution is 1:(3-5).

3. The method for preparing high-purity quartz sand based on acid leaching treatment according to claim 1, characterized in that, In step S3, the mass ratio of the first stage acid-leached quartz sand to the second stage acid-leaching solution is 1:(3-5), and the ethanol aqueous solution is composed of ethanol and deionized water in a mass ratio of 1:(1-2).

4. The method for preparing high-purity quartz sand based on acid leaching treatment according to claim 1, characterized in that, In step S21, the mass ratio of deionized water, oxalic acid, ammonium fluoride, ascorbic acid and fluorosilicic acid solution is 100: (8-15): (3-8): (1-3): (10-20). The fluorosilicic acid solution is composed of fluorosilicic acid and deionized water in a mass ratio of 1:(2-3).

5. The method for preparing high-purity quartz sand based on acid leaching treatment according to claim 1, characterized in that, In step S22, the mass ratio of acetylacetone to deionized water in step S21 is (2-5):100, and the mass fraction of deionized water in the transparent solution is 45-55%.

6. The method for preparing high-purity quartz sand based on acid leaching treatment according to claim 1, characterized in that, In step S31, the mass ratio of salicylic acid, methanol and choline chloride is 10:(20-40):(3-6).

7. The method for preparing high-purity quartz sand based on acid leaching treatment according to claim 1, characterized in that, In step S32, the mass ratio of the precursor solvent, deionized water, and betaine is 10:(20-30):(1-2); in step S33, the mass fraction of methanol in the second-stage acid leaching solution is 5-15%.

8. The method for preparing high-purity quartz sand based on acid leaching treatment according to claim 1, characterized in that, The rapid cooling step in step S1 is as follows: Pour the calcined quartz sand into deionized water at a mass ratio of 1:(2-5) and a temperature of 20-30℃. Stir continuously during the pouring process until the temperature of the quartz sand drops below 40℃.

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