Method for removing Ca element in high-purity quartz sand sample and high-purity quartz sand prepared by method

Abstract

The invention provides a method for removing Ca element in a high-purity quartz sand sample and high-purity quartz sand prepared by the method. The method comprises the following steps: S1, carrying out primary hydrochloric acid leaching; s2, acid leaching with hydrofluoric acid; s3, secondary hydrochloric acid leaching; and S4, acid leaching with hydrochloric acid and hydrofluoric acid. The method disclosed by the invention has the beneficial effects that fine cracks can be generated in the quartz by utilizing the difference of dielectric constants of impurities and a quartz matrix through microwave acid leaching, and the contact reaction of the impurities and acid liquor is promoted, so that solid inclusions in the quartz are removed; and different acids are used for gradient synergistic acid leaching, so that the removal efficiency of Ca impurity elements in the quartz is improved, and the high-purity and stable high-purity quartz sand is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of quartz sand purification methods. Specifically, it relates to a method for removing Ca element from high-purity quartz sand samples and the high-purity quartz sand thus produced. Background Art

[0002] High-purity quartz sand is an essential key basic material for strategic emerging industries such as electronic information, photovoltaic energy, and aerospace. Its purity directly affects the performance and quality of downstream products.

[0003] The quartz crucible used for preparing photovoltaic single-crystalline silicon requires high-purity quartz sand, but only a few deposits can be naturally purified into high-purity quartz sand. Alaskite-type high-purity quartz has the characteristics of large scale and high quality, and is expected to be used as the raw material for high-purity quartz sand. Ca is a key impurity element that restricts the application of high-purity quartz products in the semiconductor manufacturing process and needs to be strictly controlled. However, there are few reports on the deep removal of Ca element for alaskite-type high-purity quartz raw materials. The occurrence state of Ca is an important index for evaluating its purity and processing and purification performance. Ca element mainly exists in quartz minerals in the form of impurities, and its content and distribution directly affect the preparation and application of high-purity quartz. Usually, Ca impurities may exist in the form of gangue mineral impurities, fluid inclusion impurities, or crystal structure impurities. During the processing of high-purity quartz, Ca element often becomes a key factor affecting product quality due to its difficult complete separation.

[0004] Research shows that Ca element may exist in quartz in the form of tiny mineral inclusions, such as carbonate minerals symbiotic with quartz. In addition, Ca may enter the quartz lattice through isomorphous substitution, resulting in lattice distortion and charge imbalance. This substitution not only increases the difficulty of separating Ca, but may also introduce other impurity elements, such as Na, K, etc. In high-purity quartz, the occurrence state of Ca has a significant impact on its performance. Ca element mainly exists in the form of fluid inclusions or lattice impurities, which not only increase the alkali metal content in quartz, but may also cause lattice distortion, thus affecting the chemical stability and high-temperature resistance of quartz.

[0005] The invention patent with the publication number CN102126727A discloses a method for purifying vein quartz under non-acid-washing conditions. The main steps of this method include crushing, calcination, magnetic separation, flotation, microwave complexation method, and ultrasonic separation and cleaning for impurity removal technology. Although this method reduces the use of acid in the purification process and has a certain protective effect on the environment, the high-purity quartz sand purified by this method needs to be further purified before being used in industries such as photovoltaic crucibles.

[0006] The invention patent with the publication number CN110398402B discloses a method for purifying quartz applicable to rocks or sand samples with different mineral compositions. The purification method includes the following steps: thickness measurement and rock and mineral identification, crushing the sample and sieving, rinsing fine particles, the first magnetic separation, treatment with aqua regia, cleaning with ultrapure water, the second magnetic separation, flotation separation, etching with HCl-H2SiF6, separation with a poly-tungstate heavy liquid, ultrasonic cleaning, polarizing microscope detection, and ICP-AES measurement of the Al content. Although this method reduces the amount of hydrofluoric acid used, it is not very applicable to high-purity quartz sand raw materials with many impurity minerals, and there is no research on the removal of Ca impurity elements.

[0007] The invention patent with the publication number CN117483092A discloses a process for purifying natural ground quartz to produce 4N grade high-purity fine-grained quartz sand. The invention mainly includes the following steps: screening, magnetic separation, reverse flotation, forward flotation, calcination-water quenching, and mixed acid leaching. Although this method has a certain effect on quartz purification, the removal effect of Ca impurity elements is average, resulting in a seriously high content of Ca impurity elements, which affects the application of high-purity quartz.

[0008] In summary, to solve the current problems and enable the stable and efficient production of albite-type high-purity quartz sand, there is an urgent need to provide a method for removing Ca elements from high-purity quartz sand samples and the high-purity quartz sand made therefrom. Summary of the Invention

[0009] The purpose of the present invention is to solve at least one of the above deficiencies existing in the prior art. For example, one of the purposes of the present invention is to provide a method for removing Ca elements from high-purity quartz sand samples and the high-purity quartz sand made therefrom. This method removes Ca elements from high-purity quartz sand samples through processes such as gradient microwave acid leaching, and can solve the problem of high content of Ca impurity elements after the purification of albite-type high-purity quartz raw materials, and obtain high-purity and stable high-purity quartz sand.

[0010] To achieve the above purpose, the present invention provides a method for removing Ca elements from high-purity quartz sand samples, including the following steps:

[0011] S1. First hydrochloric acid acid leaching

[0012] Place the preliminarily purified high-purity quartz sample in a microwave device, and perform the first microwave acid leaching treatment with hydrochloric acid to obtain the first leached sample; then repeatedly rinse the first leached sample with deionized water until the aqueous solution is neutral, filter, wash, and dry to obtain the first product;

[0013] S2. Hydrofluoric acid acid leaching

[0014] Place Product 1 in a microwave device and perform a second microwave acid leaching treatment with hydrofluoric acid to obtain Leaching Sample 2; then repeatedly rinse Leaching Sample 2 with deionized water until the aqueous solution is neutral, filter, wash, and dry to obtain Product 2;

[0015] S3. Secondary hydrochloric acid leaching

[0016] Place Product 2 in a microwave device and perform a third microwave acid leaching treatment with hydrochloric acid to obtain Leaching Sample 3; then repeatedly rinse Leaching Sample 3 with deionized water until the aqueous solution is neutral, filter, wash, and dry to obtain Product 3;

[0017] S4. Hydrochloric acid and hydrofluoric acid leaching

[0018] Place Product 3 in a microwave device and perform a fourth microwave acid leaching treatment with a mixed acid solution of hydrochloric acid and hydrofluoric acid to obtain Leaching Sample 4; then repeatedly rinse Leaching Sample 4 with deionized water until the aqueous solution is neutral, filter, wash, and dry to obtain high-purity quartz products.

[0019] In a preferred embodiment of this solution, in step S1, the solid-liquid ratio of the first microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrochloric acid used in the first microwave acid leaching is 5% to 20%.

[0020] In a preferred embodiment of this solution, in step S1, the time of the first microwave acid leaching is 1 to 8 h, the temperature of the first microwave acid leaching is 30°C to 100°C, and the microwave power used in the first microwave acid leaching is 100 to 800 W.

[0021] In a preferred embodiment of this solution, in step S2, the solid-liquid ratio of the second microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrofluoric acid used in the second microwave acid leaching is 5% to 20%.

[0022] In a preferred embodiment of this solution, in step S2, the time of the second microwave acid leaching is 1 to 8 h, the temperature of the second microwave acid leaching is 30°C to 100°C, and the microwave power of the second microwave acid leaching is 100 to 800 W.

[0023] In a preferred embodiment of this solution, in step S3, the solid-liquid ratio of the third microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrochloric acid used in the third microwave acid leaching is 5% to 20%.

[0024] In a preferred embodiment of this solution, in step S3, the time of the third microwave acid leaching is 1 to 8 h, the temperature of the third microwave acid leaching is 30°C to 100°C, and the microwave power used in the third microwave acid leaching is 100 to 800 W.

[0025] In a preferred embodiment of this solution, in step S4, the solid-liquid ratio of the fourth microwave acid leaching is 1:2 to 1:6, the mass fraction of the mixed acid solution used in the fourth microwave acid leaching is 5% to 20%, and the mass ratio of hydrochloric acid to hydrofluoric acid is 9:1 to 1:9.

[0026] In a preferred embodiment of this solution, in step S4, the time of the fourth microwave acid leaching is 1 to 8 h, the temperature of the fourth microwave acid leaching is 30°C to 100°C, and the microwave power used in the fourth microwave acid leaching is 100 to 800 W.

[0027] The present invention also provides a high-purity quartz sand, which is prepared by the above method, and the purity of the high-purity quartz sand is greater than 99.9980%.

[0028] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0029] 1) A method for removing Ca elements in a high-purity quartz sand sample provided by the present invention can utilize the difference in the dielectric constants of impurities and the quartz matrix through microwave acid leaching to generate fine cracks inside the quartz, promoting the contact reaction between impurities and the acid solution, thereby removing solid inclusions in the quartz;

[0030] 2) The present invention uses different acids for cascade synergistic acid leaching, improving the removal efficiency of Ca impurity elements in quartz and obtaining high-purity and stable high-purity quartz sand. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Through the following description with reference to the accompanying drawings, the above and other objects and / or features of the present invention will become clearer, wherein:

[0032] Figure 1 Shows the SEM scanning diagram of the original sand of the method for removing Ca elements in the high-purity quartz sand sample of the present invention and the high-purity quartz sand made therefrom.

[0033] Figure 2 Shows the SEM scanning diagram of the quartz sand after multi-gradient microwave acid leaching in Example 3 of the method for removing Ca elements in the high-purity quartz sand sample of the present invention and the high-purity quartz sand made therefrom.

[0034] Figure 3 Shows the process flow diagram of the method for removing Ca elements in the high-purity quartz sand sample of the present invention and the high-purity quartz sand made therefrom. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Hereinafter, the method for removing Ca elements in the high-purity quartz sand sample of the present invention and the high-purity quartz sand made therefrom will be described in detail with reference to exemplary embodiments.

[0036] It should be noted that "first", "second", "third", "fourth", etc. are only for convenience of description and differentiation, and should not be construed as indicating or implying relative importance.

[0037] It should be noted that the microwave acid leaching treatment described in the present invention refers to acid leaching treatment carried out in a microwave environment.

[0038] It should be noted that the high-purity quartz sample after preliminary purification described in the present invention refers to a purified sample obtained by processing the raw ore through conventional processes such as crushing, screening, sample preparation, magnetic separation, flotation, and acid leaching.

[0039] Exemplary embodiments

[0040] Reference Figure 3 As shown, the method for removing Ca element from the high-purity quartz sand sample includes the following steps:

[0041] S1. Hydrochloric acid acid leaching

[0042] Using the high-purity quartz sample after preliminary purification as the raw material, a microwave acid leaching test with a certain concentration is carried out in a microwave device at a certain temperature, time, and microwave power to obtain Leaching Sample 1;

[0043] Then, Leaching Sample 1 is repeatedly rinsed with deionized water until the aqueous solution is neutral, filtered, washed, and dried to obtain Product 1;

[0044] S2. Hydrofluoric acid acid leaching

[0045] Product 1 is subjected to a microwave acid leaching test with a certain concentration in a microwave device at a certain temperature, time, and microwave power to obtain Leaching Sample 2;

[0046] Then, Leaching Sample 2 is repeatedly rinsed with deionized water until the aqueous solution is neutral, filtered, washed, and dried to obtain Product 2;

[0047] S3. Hydrochloric acid acid leaching

[0048] Product 2 is subjected to a microwave acid leaching test with a certain concentration in a microwave device at a certain temperature, time, and microwave power to obtain Leaching Sample 3;

[0049] Then, Leaching Sample 3 is repeatedly rinsed with deionized water until the aqueous solution is neutral, filtered, washed, and dried to obtain Product 3;

[0050] S4. Hydrochloric acid and hydrofluoric acid acid leaching

[0051] Product 3 is subjected to a microwave acid leaching test with a certain ratio and a certain concentration in a microwave device at a certain temperature, time, and microwave power to obtain Leaching Sample 4;

[0052] Then, the leached sample IV is repeatedly rinsed with deionized water until the aqueous solution is neutral, filtered, washed, and dried to obtain a high-purity quartz product.

[0053] In this exemplary embodiment, in step S1, during microwave heating, due to the presence of inclusions and lattice impurities inside the quartz, there are significant differences in the dielectric constants between these impurities and the quartz matrix. The quartz matrix is transparent to microwaves, while the internal impurities in the quartz will rapidly convert electromagnetic energy into internal energy due to their large dielectric constants, which causes the internal impurities in the quartz to rapidly heat up and drive the temperature rise of the quartz matrix. The microwave selective heating will generate a large temperature difference between the inclusions inside the quartz and the quartz matrix, causing the inclusions to undergo thermal explosion. The tiny cracks generated by the thermal explosion will continuously diffuse outward along with the migration of the lattice impurities and phase transformation inside the quartz. The increase in cracks makes it easier for the internal impurities to react and be removed during the acid leaching process. Using hydrochloric acid for microwave acid leaching can react with Ca impurity elements to form CaCl2, but hydrofluoric acid easily reacts with Ca impurity elements to form CaF2 precipitate, which is likely to clog the fissures and increase the difficulty of removing impurity elements. Therefore, preferably, in step S1, hydrochloric acid is selected for microwave acid leaching. The solid-liquid ratio of the first microwave acid leaching is 1:2 to 1:6 (such as 1:3, 1:4, 1:5, etc.), the mass fraction of hydrochloric acid in the first microwave acid leaching is 5% to 20% (such as 5%, 10%, 15%, 20%, etc.), the time of the first microwave acid leaching is 1 to 8 h (such as 2 h, 6 h, 7 h, etc.), the temperature of the first microwave acid leaching is 30°C to 100°C (such as 40°C, 50°C, 90°C, etc.), and the microwave power of the first microwave acid leaching is 100 - 800 W (such as 200 W, 500 W, 700 W, etc.).

[0054] Preferably, in this exemplary embodiment, in step S2, after the hydrochloric acid microwave acid leaching, the generated CaCl2 diffuses outward. Due to the too-small fissures, some CaCl2 impurity ions are not easily diffused. Therefore, hydrofluoric acid is used for microwave acid leaching to expand the fissure channels and make it easier for the impurity elements to be diffused and removed. The solid-liquid ratio of the second microwave acid leaching is 1:2 to 1:6 (such as 1:3, 1:4, 1:5, etc.), and the mass fraction of hydrofluoric acid used in the second microwave acid leaching is 5% to 20% (such as 5%, 10%, 15%, 20%, etc.); the time of the second microwave acid leaching is 1 to 8 h (such as 2 h, 6 h, 7 h, etc.), the temperature of the second microwave acid leaching is 30°C to 100°C (such as 40°C, 50°C, 90°C, etc.), and the microwave power of the second microwave acid leaching is 100 - 800 W (such as 200 W, 500 W, 700 W, etc.).

[0055] Preferably, in this exemplary embodiment, in step S3, since new pits are generated and the fissures are enlarged after microwave acid leaching with hydrofluoric acid, new impurity elements will be exposed. Therefore, microwave acid leaching with hydrochloric acid is continued to remove Ca impurity elements, and the conditions refer to step S1; the solid-liquid ratio of the third microwave acid leaching is 1:2 to 1:6 (such as 1:3, 1:4, 1:5, etc.), and the mass fraction of hydrochloric acid used in the third microwave acid leaching is 5% to 20% (such as 5%, 10%, 15%, 20%, etc.); the time of the third microwave acid leaching is 1 to 8 h (such as 2 h, 6 h, 7 h, etc.), the temperature of the third microwave acid leaching is 30°C to 100°C (such as 40°C, 50°C, 90°C, etc.), and the microwave power used in the third microwave acid leaching is 100 to 800 W (such as 200 W, 500 W, 700 W, etc.).

[0056] Preferably, in this exemplary embodiment, in step S4, a mixed acid solution of hydrochloric acid and hydrofluoric acid is added for microwave acid leaching again to further remove Ca impurity elements; the solid-liquid ratio of the fourth microwave acid leaching is 1:2 to 1:6 (such as 1:3, 1:4, 1:5, etc.), the mass fraction of the mixed acid solution used in the fourth microwave acid leaching is 5% to 20% (such as 5%, 10%, 15%, 20%, etc.), and the mass ratio of hydrochloric acid to hydrofluoric acid is 9:1 to 1:9 (such as 3:1, 1:1, 1:5, 1:8, etc.); the time of the fourth microwave acid leaching is 1 to 8 h (such as 2 h, 6 h, 7 h, etc.), the temperature of the fourth microwave acid leaching is 30°C to 100°C (such as 40°C, 50°C, 90°C, etc.), and the microwave power used in the fourth microwave acid leaching is 100 to 800 W (such as 200 W, 500 W, 700 W, etc.).

[0057] To better understand the above exemplary embodiment of the present invention, it is further described below with examples.

[0058] The analysis results of the quartz sand products obtained from a certain albite-type high-purity quartz raw material are shown in Table 1.

[0059] Table 1 Multi-element analysis results of purified samples

[0060]

[0061]

[0062] Example 1

[0063] The method for removing Ca element from high-purity quartz sand samples includes the following steps:

[0064] S1. Acid leaching with hydrochloric acid

[0065] Using the preliminarily purified high-purity quartz sample as raw material, a microwave acid leaching test with a solid-liquid ratio of 1:2 and 5% hydrochloric acid was carried out in a microwave equipment at 30°C and a microwave power of 300W (for 1h) to obtain Leaching Sample 1;

[0066] Then, Leaching Sample 1 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 1;

[0067] S2. Hydrofluoric acid leaching

[0068] Product 1 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:2 and 5% hydrofluoric acid in a microwave equipment at 30°C and a microwave power of 300W (for 1h) to obtain Leaching Sample 2;

[0069] Then, Leaching Sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 2;

[0070] S3. Hydrochloric acid leaching

[0071] Product 2 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:2 and 5% hydrochloric acid in a microwave equipment at 30°C and a microwave power of 300W (for 1h) to obtain Leaching Sample 3;

[0072] Then, Leaching Sample 3 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 3;

[0073] S4. Hydrochloric acid and hydrofluoric acid leaching

[0074] Product 3 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:2 and a mixed acid (HCl:HF = 9:1) of 5% in a microwave equipment at 30°C and a microwave power of 300W (for 1h) to obtain Leaching Sample 4;

[0075] Then, Leaching Sample 4 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain high-purity quartz product.

[0076] Table 2 Chemical analysis results of high-purity quartz sand sample in Example 1

[0077] Element Al B Ca Cu Fe K Li Mg <![CDATA[Content / 10 -6 > 10.96 0.10 1.05 0.05 0.86 0.70 0.04 0.12 Element Mn Na Ni P Ti Zn Total <![CDATA[SiO2]]> <![CDATA[Content / 10 -6 > 0.02 1.45 <0.01 0.47 2.22 0.07 18.12 99.9982％

[0078] Example 2

[0079] The method for removing Ca element from high-purity quartz sand sample includes the following steps:

[0080] S1. Hydrochloric acid leaching

[0081] Using the preliminarily purified high-purity quartz sample as the raw material, a microwave acid leaching test with a solid-liquid ratio of 1:4 and 10% hydrochloric acid was carried out in a microwave equipment at 60 °C, for 5 hours and with a microwave power of 500 W (for 5 hours) to obtain Leaching Sample 1;

[0082] Then, Leaching Sample 1 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 1;

[0083] S2. Hydrofluoric acid leaching

[0084] Product 1 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:4 and 10% hydrofluoric acid in a microwave equipment at 60 °C and with a microwave power of 500 W (for 5 hours) to obtain Leaching Sample 2;

[0085] Then, Leaching Sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 2;

[0086] S3. Hydrochloric acid leaching

[0087] Product 2 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:4 and 10% hydrochloric acid in a microwave equipment at 60 °C and with a microwave power of 500 W (for 5 hours) to obtain Leaching Sample 3;

[0088] Then, Leaching Sample 3 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 3;

[0089] S4. Hydrochloric acid and hydrofluoric acid leaching

[0090] Product 3 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:4 and a mixed acid of 10% (where HCl:HF = 6:4) in a microwave equipment at 60 °C and with a microwave power of 500 W (for 5 hours) to obtain Leaching Sample 4;

[0091] Then, Leaching Sample 4 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain the high-purity quartz product.

[0092] Table 3 Chemical analysis results of the high-purity quartz sand sample in Example 2

[0093] Element Al B Ca Cu Fe K Li Mg <![CDATA[Content / 10 -6 > 10.55 0.12 0.77 <0.01 0.44 0.62 0.03 0.19 Element Mn Na Ni P Ti Zn Total <![CDATA[SiO2]]> <![CDATA[Content / 10 -6 > <0.01 1.35 0.02 0.35 2.02 0.05 16.53 99.9983％

[0094] Example 3

[0095] The method for removing Ca element from the high-purity quartz sand sample includes the following steps:

[0096] S1. Hydrochloric acid leaching

[0097] Using the preliminarily purified high-purity quartz sample as the raw material, a microwave acid leaching test with a solid-liquid ratio of 1:6 and 20% hydrochloric acid was carried out in a microwave equipment at 100°C and a microwave power of 800W (for 8 hours) to obtain Leaching Sample 1;

[0098] Then, Leaching Sample 1 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 1;

[0099] S2. Hydrofluoric acid leaching

[0100] Product 1 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:6 and 20% hydrofluoric acid in a microwave equipment at 100°C and a microwave power of 800W (for 8 hours) to obtain Leaching Sample 2;

[0101] Then, Leaching Sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 2;

[0102] S3. Hydrochloric acid leaching

[0103] Product 2 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:6 and 20% hydrochloric acid in a microwave equipment at 100°C and a microwave power of 800W (for 8 hours) to obtain Leaching Sample 3;

[0104] Then, Leaching Sample 3 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain Product 3;

[0105] S4. Hydrochloric acid and hydrofluoric acid leaching

[0106] Product 3 was subjected to a microwave acid leaching test with a solid-liquid ratio of 1:6 and 20% mixed acid (where HCl:HF = 1:9) in a microwave equipment at 100°C and a microwave power of 800W (for 8 hours) to obtain Leaching Sample 4;

[0107] Then, Leaching Sample 4 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed, and dried to obtain the high-purity quartz product.

[0108] Table 4 Chemical analysis results of the high-purity quartz sand sample in Example 2

[0109] Element Al B Ca Cu Fe K Li Mg <![CDATA[Content / 10 -6 > 10.73 0.1 0.52 0.02 0.24 0.57 0.05 0.15 Element Mn Na Ni P Ti Zn Total <![CDATA[SiO2]]> <![CDATA[Content / 10 -6 > <0.01 1.37 0.02 0.24 1.89 0.03 15.94 99.9984％

[0110] The invention principle of the present invention is:

[0111] During the microwave heating process of quartz, the inclusions and lattice impurities contained therein will exhibit significant differences in dielectric properties from the quartz matrix. Since the quartz matrix is transparent to microwaves, while the impurities can rapidly absorb electromagnetic energy and convert it into heat due to their higher dielectric constant, this causes the temperature in the impurity regions to rise sharply and conduct to the quartz matrix. This selective heating effect will form a significant temperature gradient between the impurities and the matrix, triggering the thermally induced cracking of the inclusions. The generated microcracks will gradually expand along with the migration of impurities in the lattice and the process of phase change. The development of this crack network creates favorable conditions for the efficient removal of impurities in the subsequent acid leaching process. Using hydrochloric acid for microwave acid leaching can react with Ca impurity elements to form CaCl2, but hydrofluoric acid easily reacts with Ca impurity elements to form CaF2 precipitate, which is likely to block the fissures and increase the difficulty of removing impurity elements. Therefore, hydrochloric acid microwave acid leaching is first used to remove the exposed Ca impurities. During the acid leaching process, the generated CaCl2 diffuses outwards. Due to the too small fissures, part of the Ca 2+ impurity ions are not easily diffused. Therefore, after hydrochloric acid microwave acid leaching, the sample is cleaned, and then hydrofluoric acid microwave acid leaching is used to expand the fissure channels, making it easier for impurity elements to diffuse and be removed. At the same time, new pits will be generated after hydrofluoric acid microwave acid leaching, which will expose new Ca impurity elements. Therefore, hydrochloric acid microwave acid leaching is continued to remove Ca impurity elements. Finally, a mixed acid solution of hydrochloric acid and hydrofluoric acid is added for microwave acid leaching to further reduce the content of Ca impurity elements.

[0112] Figure 1 It is the SEM scanning image of the original sand of the high-purity quartz sample. Figure 2 It is the SEM scanning image of the quartz sand after multi-gradient microwave acid leaching in Example 3. From Figure 1 and Figure 2 it can be seen that after multi-gradient acid leaching, the crack channels are significantly enlarged, increasing the contact between the acid solution and the impurity elements and improving the removal efficiency.

[0113] Although the present invention has been described above in conjunction with exemplary embodiments and the accompanying drawings, those of ordinary skill in the art should clearly 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 removing Ca element from high-purity quartz sand samples, characterized in that, It includes the following steps: S1. First hydrochloric acid leaching Place the preliminarily purified high-purity quartz sample in a microwave device, and perform the first microwave acid leaching treatment with hydrochloric acid to obtain the first leached sample; Then repeatedly rinse the first leached sample with deionized water until the aqueous solution is neutral, filter, wash, and dry to obtain the first product; S2. Hydrofluoric acid leaching Place the first product in a microwave device, and perform the second microwave acid leaching treatment with hydrofluoric acid to obtain the second leached sample; Then repeatedly rinse the second leached sample with deionized water until the aqueous solution is neutral, filter, wash, and dry to obtain the second product; S3. Second hydrochloric acid leaching Place the second product in a microwave device, and perform the third microwave acid leaching treatment with hydrochloric acid to obtain the third leached sample; Then repeatedly rinse the third leached sample with deionized water until the aqueous solution is neutral, filter, wash, and dry to obtain the third product; S4. Hydrochloric acid and hydrofluoric acid leaching Place the third product in a microwave device, and perform the fourth microwave acid leaching treatment with a mixed acid solution of hydrochloric acid and hydrofluoric acid to obtain the fourth leached sample; Then repeatedly rinse the fourth leached sample with deionized water until the aqueous solution is neutral, filter, wash, and dry to obtain the high-purity quartz product.

2. The method according to claim 1, wherein: In the step S1, the solid-liquid ratio of the first microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrochloric acid used for the first microwave acid leaching is 5% to 20%.

3. The method according to claim 1, characterized in that: In the step S1, the time of the first microwave acid leaching is 1 to 8 h, the temperature of the first microwave acid leaching is 30°C to 100°C, and the microwave power used for the first microwave acid leaching is 100 to 800 W.

4. The method according to claim 1, wherein: In the step S2, the solid-liquid ratio of the second microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrofluoric acid used for the second microwave acid leaching is 5% to 20%.

5. The method according to claim 4, wherein: In the step S2, the time of the second microwave acid leaching is 1 to 8 h, the temperature of the second microwave acid leaching is 30°C to 100°C, and the microwave power of the second microwave acid leaching is 100 to 800 W.

6. The method according to claim 1, characterized in that: In the step S3, the solid-liquid ratio of the third microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrochloric acid used for the third microwave acid leaching is 5% to 20%.

7. The method according to claim 1, characterized in that: In the step S3, the time of the third microwave acid leaching is 1 to 8 h, the temperature of the third microwave acid leaching is 30°C to 100°C, and the microwave power used for the third microwave acid leaching is 100 to 800 W.

8. The method according to claim 1, characterized in that: In the step S4, the solid-liquid ratio of the fourth microwave acid leaching is 1:2 to 1:6, the mass fraction of the mixed acid solution used for the fourth microwave acid leaching is 5% to 20%, and the mass ratio of hydrochloric acid to hydrofluoric acid is 9:1 to 1:

9.

9. The method according to claim 1, characterized in that: In the step S4, the time of the fourth microwave acid leaching is 1 to 8 h, the temperature of the fourth microwave acid leaching is 30°C to 100°C, and the microwave power used for the fourth microwave acid leaching is 100 to 800 W.

10. A high-purity quartz sand, characterized in that, The high-purity quartz sand is prepared by the method described in any one of claims 1 to 9, and the purity of the high-purity quartz sand is greater than 99.9980%.

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