A method for eliminating radioactive elements from a quartz crystal

Abstract

The application relates to the technical field of quartz crystal purification, and particularly discloses a method for eliminating radioactive elements in quartz crystals, which comprises the following steps: adding quartz sand into a composite cleaning solution, stirring and cleaning, then performing solid-liquid separation and water washing to obtain pretreated quartz sand; performing heat treatment on the pretreated quartz sand in an oxygen-containing atmosphere at 850-1000 DEG C for 2-4 hours to obtain heat-treated quartz sand; rapidly cooling the heat-treated quartz sand in cooling water at 10-30 DEG C for 15-30 seconds, then crushing and screening to obtain crushed quartz sand; adding the crushed quartz sand into a selective acid cleaning solution under stirring to perform an acid cleaning reaction, then performing solid-liquid separation, washing and drying after the reaction to obtain low-radioactivity quartz sand. The composite cleaning solution and the selective acid cleaning solution are used in cooperation to efficiently remove radioactive elements such as uranium and thorium in the quartz crystals, and the physical and chemical properties of the quartz crystals can meet the requirements of high-end semiconductor and optical applications.

Description

Technical Field

[0001] This invention relates to the field of quartz crystal purification technology, and specifically to a method for eliminating radioactive elements from quartz crystals. Background Technology

[0002] Quartz crystals (especially high-purity quartz sand) are key basic materials in semiconductors, photovoltaics, optical fiber communications and other fields. Their purity directly affects the performance and reliability of end products. Natural quartz ore commonly contains natural radioactive elements such as uranium (U) and thorium (Th) and their decay products. These radioactive impurities not only generate background radiation during subsequent processing and use, affecting the performance of high-precision electronic devices, but also pose a potential threat to the environment and personnel safety.

[0003] Currently, the main methods for removing radioactive impurities from quartz include physical sorting, high-temperature heat treatment, and acid washing. Physical separation (such as flotation and magnetic separation) is effective for radioactive minerals existing in the form of inclusions, but has a very low removal rate for radioactive elements that have entered the quartz lattice in an isomorphic form. High-temperature heat treatment (usually above 1000℃) can cause some radioactive elements to migrate to the crystal surface through diffusion, but it is energy-intensive and a single heat treatment is not enough to reduce the radioactivity to an extremely low level. Acid leaching is a common method to improve the purity of quartz. Hydrofluoric acid is widely used because of its unique etching ability on silicon dioxide. Conventional acid leaching often uses high-concentration mixed acids (such as HF-HCl or HF-HNO3 systems). While it removes impurities efficiently, it often causes excessive corrosion of the quartz matrix, resulting in a high silicon loss rate. It is also difficult to selectively remove radionuclides hidden deep in microcracks or lattice defects. In addition, existing acid leaching processes are often simply connected in series with physical separation or heat treatment. There is insufficient synergy between the steps, the process flow is long, and the removal effect on radioactive elements in complex occurrence states is limited, making it difficult to stably prepare low-radioactivity quartz products.

[0004] Therefore, developing a purification method that is highly efficient, selective, has low silicon loss, and can deeply remove various radioactive elements from quartz crystals is of great significance for meeting the urgent needs of high-end industries for low-radioactive quartz materials. Based on the above, this application proposes a method for eliminating radioactive elements from quartz crystals and a preparation method thereof. Summary of the Invention

[0005] To address the problems in existing acid etching processes for removing radioactive elements from quartz, such as excessive wear of the quartz matrix due to indiscriminate etching, inability to achieve selective removal, lengthy process flow, poor coordination, and difficulty in consistently obtaining low-radioactivity, high-purity quartz products, this invention proposes a method for eliminating radioactive elements from quartz crystals.

[0006] This invention provides a method for eliminating radioactive elements from quartz crystals, employing the following technical solution: A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Add the quartz sand to the composite cleaning solution, stir and clean at 40-60℃ for 30-90 minutes, then perform solid-liquid separation and water washing to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand in an oxygen-containing atmosphere at 850-1000℃ for 2-4 hours to obtain heat-treated quartz sand. Step 3: Immerse the heat-treated quartz sand in cooling water at 10-30℃ for rapid cooling for 15-30 seconds, then crush and screen to obtain crushed quartz sand; Step 4: Under stirring, add crushed quartz sand to selective pickling solution and carry out pickling reaction at 0.2-0.8 MPa. After the reaction is completed, perform solid-liquid separation, washing and drying to obtain low radioactive quartz sand.

[0007] Preferably, the mass ratio of quartz sand to composite cleaning solution in step 1 is 1:3-5.

[0008] Preferably, the stirring rate in step 1 is 200-400 rpm.

[0009] Preferably, the water washing in step 1 refers to spraying and washing with deionized water until the pH value is 6-7.

[0010] Preferably, the composite cleaning solution in step 1 is prepared by the following method: S1. Under stirring, citric acid, sodium gluconate and chelating dispersant are added sequentially to deionized water. The system is then heated to 50-60℃ and stirred for 30-50 minutes to obtain the chelated base solution. S2. Reduce the system temperature to 30-40℃, add hydrogen peroxide and ammonium persulfate to the chelating base solution, stir the reaction for 30-60 min, then introduce inert gas and bubble purge for 20-30 min to obtain the oxidation cleaning solution; S3. Add silane coupling agent and corrosion inhibitor to the oxidative cleaning solution, stir at 30-40℃ for 1-2 hours. After the reaction is completed, cool down to 20-25℃ and stir for 2-4 hours. Then adjust the pH of the system to 4.5-5.5 with an acidity regulator to obtain the composite cleaning solution.

[0011] Preferably, the stirring rate in S1 is 300-500 rpm.

[0012] Preferably, the mass ratio of deionized water, citric acid, sodium gluconate and chelating dispersant in S1 is 100:6-8:2-4:1-3.

[0013] Preferably, the chelating dispersant in S1 is selected from at least one of low molecular weight sodium polyacrylate, maleic acid-acrylic acid copolymer, and polyepoxysuccinic acid.

[0014] Preferably, the chelating dispersant in S1 is low molecular weight sodium polyacrylate.

[0015] Preferably, the low molecular weight sodium polyacrylate has a molecular weight of 3000-5000 and a solid content of 40-45%.

[0016] Preferably, the mass ratio of hydrogen peroxide, ammonium persulfate and chelating base liquid in S2 is 1:0.5-2:0.1-0.5.

[0017] Preferably, the stirring rate in S2 is 150-300 rpm.

[0018] Preferably, the flow rate of the inert gas in S2 is 0.5-1.0 L / min.

[0019] Preferably, the inert gas in S2 is nitrogen, argon, or helium.

[0020] Preferably, the mass ratio of the oxidizing cleaning solution, silane coupling agent, and benzotriazole in S3 is 100:3-5:1-3.

[0021] Preferably, the silane coupling agent in S3 is a mixture of γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0022] Preferably, the silane coupling agent in S3 is γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1-2.

[0023] In this invention, the hydrolysis products of silane coupling agents are used to form functionalized molecular films on the surface of quartz sand and the walls of microcracks. The active functional groups (such as amino and epoxy groups) carried by these films can be used to anchor radionuclides with affinity, thereby changing the wettability inside the cracks. This helps the crown ether and complexing agent in the subsequent selective pickling solution to deeply penetrate and extract uranium and thorium ions from lattice defects.

[0024] Preferably, the corrosion inhibitor in S3 is selected from at least one of benzotriazole, methylbenzotriazole, 2-mercaptobenzothiazole, dodecylamine, and hexadecylamine.

[0025] Preferably, the corrosion inhibitor in S3 is benzotriazole.

[0026] Preferably, the stirring reaction rate in S3 is 200-400 rpm; the stirring and ripening rate is 50-100 rpm.

[0027] Preferably, the cooling rate in S3 is 0.5-1.0℃ / min.

[0028] Preferably, the acidity regulator in S3 is selected from at least one of ammonia, triethanolamine, sodium hydroxide, sodium bicarbonate, and acetic acid.

[0029] Preferably, the acidity regulator in S3 is an ammonia solution with a mass fraction of 20%.

[0030] Preferably, the oxygen volume fraction of the oxygen-containing atmosphere in step 2 is 10-20%.

[0031] Preferably, the particle size of the crushed quartz sand in step 3 is 0.1-0.8 mm.

[0032] Preferably, the stirring rate in step 4 is 100-300 rpm.

[0033] Preferably, the mass ratio of crushed quartz sand to selective pickling solution in step 4 is 1:4-6.

[0034] Preferably, the selective pickling solution in step 4 is an aqueous solution containing crown ether compounds, inorganic acids, alcohol cosolvents, and organic complexing agents.

[0035] Preferably, the selective pickling solution in step 4 is prepared by the following steps: (1) Under stirring, add organic complexing agent and crown ether compound to deionized water in sequence, and stir under ultrasonic action for 10-15 min to obtain complexing agent-crown ether solution; (2) Keep the stirring state unchanged, add alcohol co-solvent to the complexing agent-crown ether solution, heat in a water bath to 40-45℃, stir for 10-15 min, and then cool to 25-30℃ to obtain complexing agent-crown ether-alcohol mixture; (3) After adding inorganic acid to the complexing agent-crown ether-alcohol mixture, degas it under a vacuum of -0.08 to -0.10 MPa for 5-10 min. After degassing, let it stand and age for 12-24 h to obtain selective pickling solution.

[0036] Preferably, the stirring rate in step (1) is 300-400 rpm.

[0037] Preferably, in step (1), the mass ratio of deionized water, organic complexing agent and crown ether compound is 100:1-5:1-2.

[0038] Preferably, the organic complexing agent in step (1) is an aromatic compound containing a sulfonic acid group and an ortho-hydroxyl group.

[0039] Preferably, the organic complexing agent in step (1) is disodium 1,2-dihydroxybenzene-3,5-disulfonic acid or 5-sulfosalicylic acid.

[0040] Preferably, the crown ether compound in step (1) is dibenzo-18-crown-6 or 15-crown-5.

[0041] Preferably, the ultrasound in step (1) refers to controlling the ultrasound power to be 200-300W, the ultrasound frequency to be 30-40KHz, using pulse mode, working for 2-3s, and stopping for 1-2s.

[0042] Preferably, in step (2), the mass ratio of the complex-crown ether solution to the alcohol co-solvent is 100:10-30.

[0043] Preferably, the alcohol co-solvent in step (2) is isopropanol, ethanol or ethylene glycol.

[0044] Preferably, the mass ratio of inorganic acid and complex-crown ether-alcohol mixture in step (3) is 0.5-2:100.

[0045] Preferably, the inorganic acid in step (3) is hydrochloric acid or nitric acid.

[0046] Preferably, the inorganic acid in step (3) is a hydrochloric acid solution with a mass fraction of 36%.

[0047] Preferably, the washing in step 4 refers to washing with deionized water until neutral.

[0048] Preferably, the drying in step 4 refers to drying at 100-150℃ for 2-6 hours.

[0049] Preferably, the acid washing reaction in step 4 is carried out at 60-90°C for 4-8 hours.

[0050] In summary, the present invention has the following beneficial effects: 1. This invention achieves targeted removal of radioactive elements from quartz crystals through a two-step cleaning process. The composite cleaning solution effectively removes organic and common metallic contaminants from the surface, creating conditions for subsequent deep cleaning. The core selective acid pickling solution utilizes the highly efficient and specific complexing ability of disodium 1,2-dihydroxybenzene-3,5-disulfonic acid for radioactive nuclides such as uranium (U) and thorium (Th), combined with the selective phase transfer catalysis of dibenzo-18-crown-6, to remove radioactive ions from the quartz lattice in a mild acidic environment (pH 1.5-2.0) without corroding the silica framework. This fundamentally ensures that the quartz crystal achieves low radioactivity while maintaining its physicochemical properties.

[0051] 2. This invention abandons the highly corrosive and dangerous hydrofluoric acid (HF) used in traditional processes, and uses a dilute hydrochloric acid system as the core, making the operation safer and requiring less equipment. The introduced ultrasonic-assisted dispersion ensures the uniform distribution of hydrophobic crown ethers in the acid solution. The gradient heating and vacuum degassing steps effectively prevent the generation of bubbles and oxidation side reactions, improving the consistency and stability of the cleaning solution. The combination of low-temperature water bath and long-term aging ensures that the complexation reaction is fully carried out, resulting in low energy consumption and good reproducibility.

[0052] 3. The low-radioactivity quartz crystal prepared by this invention can meet the stringent requirements for background radioactivity of materials in fields such as aerospace, high-precision inertial navigation, quantum communication and next-generation extreme ultraviolet (EUV) lithography optical systems. This technology provides key material support for the localization of high-performance quartz resonators, filters and optical components, and breaks through the technical bottleneck of long-term reliance on imported high-end quartz substrates. Detailed Implementation

[0053] The present invention will be further described in detail below with reference to the embodiments.

[0054] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0055] The key raw materials used in this invention are sourced from the following sources: Citric acid: Citric acid monohydrate, CAS No. 5949-29-1, purchased from Henan Mingzhixin Chemical Products Co., Ltd.; Sodium gluconate: CAS No. 527-07-1, purchased from Jinan Mingqi Chemical Co., Ltd.; Low molecular weight sodium polyacrylate: molecular weight 4000, solid content 42%, model PAAS 4000, purchased from Nantong Dayao Chemical Co., Ltd. Ammonium persulfate: CAS No. 7727-54-0, purchased from Guangdong Qiming Chemical Technology Co., Ltd.; γ-aminopropyltriethoxysilane: CAS No. 919-30-2, purchased from Ba Shifu (Shanghai) Biomedical Technology Co., Ltd.; γ-(2,3-epoxypropoxy)propyltrimethoxysilane: CAS No. 2530-83-8, purchased from Tianmen Hengchang Chemical Co., Ltd.; Benzotriazole: CAS No. 95-14-7, purchased from Jinan Xinhong Chemical Technology Co., Ltd.; Disodium 1,2-dihydroxybenzene-3,5-disulfonic acid: CAS No. 149-45-1, purchased from Pande (Shanghai) International Trading Co., Ltd.; Dibenzo-18-crown-6: Product No. D102033-100g, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0056] Preparation Examples 1-3 and Comparative Preparation Examples 1-3 provide a method for preparing a composite cleaning solution.

[0057] Preparation Example 1 The composite cleaning solution is prepared by the following method: S1. Control the mass ratio of deionized water, citric acid, sodium gluconate and low molecular weight polyacrylate to 100:6:2:1. Add citric acid, sodium gluconate and low molecular weight polyacrylate to deionized water in sequence at a stirring speed of 300 rpm. Then heat the system to 50°C and continue stirring for 30 min to obtain chelated base liquid. S2. Control the mass ratio of hydrogen peroxide, ammonium persulfate and chelating base liquid to 1:0.5:0.1, lower the system temperature to 30℃, add hydrogen peroxide and ammonium persulfate to the chelating base liquid, stir the reaction at 150 rpm for 60 min, then introduce nitrogen gas (gas flow rate of 0.5 L / min) and bubble purge for 30 min to obtain the oxidative cleaning solution; S3. Control the mass ratio of the oxidizing cleaning solution, silane coupling agent (including γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1) and benzotriazole to 100:3:1. Add the silane coupling agent and benzotriazole to the oxidizing cleaning solution, and stir at 200 rpm for 2 hours at 30°C. After the reaction is completed, cool down to 20°C at a rate of 0.5°C / min and stir at 50 rpm for 4 hours to mature. Then adjust the pH of the system to 4.5 with a 20% ammonia solution to obtain the composite cleaning solution.

[0058] Preparation Example 2 The composite cleaning solution is prepared by the following method: S1. Control the mass ratio of deionized water, citric acid, sodium gluconate and low molecular weight polyacrylate to 100:7:3:2. Add citric acid, sodium gluconate and low molecular weight polyacrylate to deionized water in sequence at a stirring speed of 400 rpm. Then heat the system to 55°C and continue stirring for 40 min to obtain chelated base liquid. S2. Control the mass ratio of hydrogen peroxide, ammonium persulfate and chelating base liquid to 1:1.2:0.3, lower the system temperature to 35℃, add hydrogen peroxide and ammonium persulfate to the chelating base liquid, stir the reaction at 200 rpm for 45 min, then introduce nitrogen gas (gas flow rate of 0.7 L / min) and bubble purge for 25 min to obtain the oxidative cleaning solution; S3. Control the mass ratio of the oxidizing cleaning solution, silane coupling agent (including γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1.5) and benzotriazole to be 100:4:2. Add the silane coupling agent and benzotriazole to the oxidizing cleaning solution, and stir the mixture at 300 rpm for 1.5 h at 36 °C. After the reaction is completed, cool the mixture to 23 °C at a rate of 0.7 °C / min and stir at 70 rpm for 3 h to mature the mixture. Then adjust the pH of the system to 4.9 with a 20% ammonia solution to obtain the composite cleaning solution.

[0059] Preparation Example 3 The composite cleaning solution is prepared by the following method: S1. Control the mass ratio of deionized water, citric acid, sodium gluconate and low molecular weight polyacrylate to 100:8:4:3. Add citric acid, sodium gluconate and low molecular weight polyacrylate to deionized water in sequence at a stirring speed of 500 rpm. Then heat the system to 60°C and continue stirring for 30 min to obtain chelated base liquid. S2. Control the mass ratio of hydrogen peroxide, ammonium persulfate and chelating base liquid to 1:2:0.5, lower the system temperature to 40℃, add hydrogen peroxide and ammonium persulfate to the chelating base liquid, stir the reaction at 300 rpm for 30 min, introduce nitrogen gas (gas flow rate of 1.0 L / min), bubble and purge for 20 min to obtain the oxidation cleaning solution; S3. Control the mass ratio of oxidative cleaning solution, silane coupling agent (including γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:2) and benzotriazole to 100:5:3. Add silane coupling agent and benzotriazole to the oxidative cleaning solution, and stir at 400 rpm for 1 h at 40 °C. After the reaction is completed, cool down to 25 °C at a rate of 1.0 °C / min and stir at 100 rpm for 2 h to mature. Then adjust the pH of the system to 5.5 with a 20% ammonia solution to obtain the composite cleaning solution.

[0060] Comparative Preparation Example 1 The composite cleaning solution is prepared by the following method: S1. Control the mass ratio of deionized water, citric acid and sodium gluconate to 100:6:2. Add citric acid and sodium gluconate to deionized water in sequence at a stirring speed of 300 rpm. Then heat the system to 50°C and continue stirring for 30 min to obtain a non-dispersible base liquid. S2. Control the mass ratio of hydrogen peroxide, ammonium persulfate and undispersed base liquid to 1:0.5:0.1, lower the system temperature to 30℃, add hydrogen peroxide and ammonium persulfate to the undispersed base liquid, stir the reaction at 150 rpm for 60 min, then introduce nitrogen gas (gas flow rate of 0.5 L / min) and bubble purge for 30 min to obtain undispersed oxidative cleaning solution; S3. Control the mass ratio of the non-dispersible oxidative cleaning solution, silane coupling agent (including γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1) and benzotriazole to be 100:3:1. Add the silane coupling agent and benzotriazole to the non-dispersible oxidative cleaning solution, and stir at 200 rpm for 2 h at 30 °C. After the reaction is completed, cool down to 20 °C at a rate of 0.5 °C / min and stir at 50 rpm for 4 h to mature. Then adjust the pH of the system to 4.5 with a 20% ammonia solution to obtain the non-dispersible composite cleaning solution.

[0061] Comparative Preparation Example 2 The composite cleaning solution is prepared by the following method: S1. Control the mass ratio of deionized water, citric acid, sodium gluconate and low molecular weight polyacrylate to 100:6:2:1. Add citric acid, sodium gluconate and low molecular weight polyacrylate to deionized water in sequence at a stirring speed of 300 rpm. Then heat the system to 50°C and continue stirring for 30 min to obtain chelated base liquid. S2. Control the mass ratio of hydrogen peroxide and chelating base liquid to 1.5:0.1, lower the system temperature to 30℃, add hydrogen peroxide to chelating base liquid, stir the reaction at 150 rpm for 60 min, then introduce nitrogen gas (gas flow rate of 0.5 L / min) and bubble purge for 30 min to obtain single oxygen cleaning solution. S3. Control the mass ratio of the oxidative cleaning solution, silane coupling agent (including γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1) and benzotriazole to be 100:3:1. Add the silane coupling agent and benzotriazole to the oxidative cleaning solution. Stir at 200 rpm for 2 hours at 30°C. After the reaction is completed, cool down to 20°C at a rate of 0.5°C / min and stir at 50 rpm for 4 hours to mature. Then adjust the pH of the system to 4.5 with a 20% ammonia solution to obtain the composite cleaning solution.

[0062] Comparative preparation example 3 The composite cleaning solution is prepared by the following method: S1. Control the mass ratio of deionized water, citric acid, sodium gluconate and low molecular weight polyacrylate to 100:6:2:1. Add citric acid, sodium gluconate and low molecular weight polyacrylate to deionized water in sequence at a stirring speed of 300 rpm. Then heat the system to 50°C and continue stirring for 30 min to obtain chelated base liquid. S2. Control the mass ratio of hydrogen peroxide, ammonium persulfate and chelating base liquid to 1:0.5:0.1, lower the system temperature to 30℃, add hydrogen peroxide and ammonium persulfate to the chelating base liquid, stir the reaction at 150 rpm for 60 min, then introduce nitrogen gas (gas flow rate of 0.5 L / min) and bubble purge for 30 min to obtain the oxidative cleaning solution; S3. Control the mass ratio of oxidative cleaning solution and benzotriazole to 100:1. Add benzotriazole to the oxidative cleaning solution and stir at 200 rpm for 2 hours at 30°C. After the reaction is completed, cool down to 20°C at a rate of 0.5°C / min and stir at 50 rpm for 4 hours to mature. Then adjust the pH of the system to 4.5 with a 20% ammonia solution to obtain the composite cleaning solution.

[0063] Preparation Examples 4-6 and Comparative Preparation Example 4-5 provide a method for preparing a selective pickling solution.

[0064] Preparation Example 4 Selective pickling solution is prepared by the following steps: (1) The mass ratio of deionized water, disodium 1,2-dihydroxybenzene-3,5-disulfonic acid and dibenzo-18-crown-6 was controlled to be 100:1:1. After adding disodium 1,2-dihydroxybenzene-3,5-disulfonic acid and dibenzo-18-crown-6 to deionized water at a stirring speed of 300 rpm, the ultrasonic power was controlled to be 200 W, the ultrasonic frequency was 30 kHz, the pulse mode was used, the working time was 2 s and the stop time was 1 s, and the mixture was stirred for 15 min under ultrasonic action to obtain a complex-crown ether solution. (2) Control the mass ratio of complexing-crown ether solution and isopropanol to 100:10, keep the stirring state unchanged, add isopropanol to complexing-crown ether solution, heat to 40°C in water bath, stir for 15 min, and then cool to 25°C to obtain complexing agent-crown ether-alcohol mixture. (3) The mass ratio of 36% hydrochloric acid solution and complex-crown ether-alcohol mixture is controlled to be 0.5:100. After adding 36% hydrochloric acid solution to complex-crown ether-alcohol mixture, degas it under vacuum of -0.08MPa for 5 min. After degassing, let it stand and age for 12 h to obtain selective pickling solution.

[0065] Preparation Example 5 Selective pickling solution is prepared by the following steps: (1) The mass ratio of deionized water, disodium 1,2-dihydroxybenzene-3,5-disulfonic acid and dibenzo-18-crown-6 was controlled to be 100:3:1.5. After adding disodium 1,2-dihydroxybenzene-3,5-disulfonic acid and dibenzo-18-crown-6 to deionized water at a stirring speed of 350 rpm, the ultrasonic power was controlled to be 250 W, the ultrasonic frequency was 35 KHz, the pulse mode was used, the working time was 2 s and the stop time was 1 s, and the mixture was stirred for 13 min under ultrasonic action to obtain a complex-crown ether solution. (2) The mass ratio of complexing-crown ether solution to isopropanol is 100:20. While keeping the stirring state unchanged, add isopropanol to the complexing-crown ether solution, heat in a water bath to 42°C, stir for 13 min, and then cool to 27°C to obtain a complexing agent-crown ether-alcohol mixture. (3) The mass ratio of 36% hydrochloric acid solution and complex-crown ether-alcohol mixture is controlled to be 1.5:100. After adding 36% hydrochloric acid solution to complex-crown ether-alcohol mixture, degas it under vacuum of -0.09MPa for 7 min. After degassing, let it stand and age for 18 h to obtain selective pickling solution.

[0066] Preparation Example 6 Selective pickling solution is prepared by the following steps: (1) The mass ratio of deionized water, disodium 1,2-dihydroxybenzene-3,5-disulfonic acid and dibenzo-18-crown-6 was controlled to be 100:5:2. After adding disodium 1,2-dihydroxybenzene-3,5-disulfonic acid and dibenzo-18-crown-6 to deionized water at a stirring speed of 400 rpm, the ultrasonic power was controlled to be 300 W, the ultrasonic frequency was 40 kHz, the pulse mode was used, the working time was 3 s and the stop time was 2 s, and the mixture was stirred for 10 min under ultrasonic action to obtain a complex-crown ether solution. (2) The mass ratio of complex-crown ether solution to isopropanol is 100:30. While keeping the stirring state unchanged, add isopropanol to complex-crown ether solution, heat to 45°C in a water bath, stir for 10 min, and then cool to 30°C to obtain complex-crown ether-alcohol mixture. (3) The mass ratio of 36% hydrochloric acid solution and complex-crown ether-alcohol mixture is controlled at 2:100. After adding 36% hydrochloric acid solution to complex-crown ether-alcohol mixture, degas it for 10 min under vacuum of -0.10 MPa. After degassing, let it stand and age for 24 h to obtain selective pickling solution.

[0067] Comparative preparation example 4 Selective pickling solution is prepared by the following steps: (1) Control the mass ratio of deionized water and dibenzo-18-crown-6 to 100:2. Add dibenzo-18-crown-6 to deionized water at a stirring speed of 300 rpm. Control the ultrasonic power to 200 W and the ultrasonic frequency to 30 kHz. Use pulse mode, work for 2 seconds and stop for 1 second. Stir for 15 minutes under ultrasonic action to obtain crown ether solution. (2) Control the mass ratio of crown ether solution and isopropanol to 100:10, keep the stirring state unchanged, add isopropanol to crown ether solution, heat to 40°C in water bath, stir for 15 min, and then cool to 25°C to obtain crown ether-alcohol mixture. (3) The mass ratio of 36% hydrochloric acid solution and crown ether-alcohol mixture is controlled to be 0.5:100. After adding 36% hydrochloric acid solution to crown ether-alcohol mixture, degas it under vacuum of -0.08MPa for 5 minutes. After degassing, let it stand for 12 hours to obtain selective pickling solution.

[0068] Comparative preparation example 5 Selective pickling solution is prepared by the following steps: (1) Control the mass ratio of deionized water and disodium 1,2-dihydroxybenzene-3,5-disulfonic acid to 100:2. Add disodium 1,2-dihydroxybenzene-3,5-disulfonic acid to deionized water at a stirring speed of 300 rpm. Control the ultrasonic power to 200 W and the ultrasonic frequency to 30 kHz. Use pulse mode, work for 2 seconds and stop for 1 second. Stir for 15 minutes under ultrasonic action to obtain complex solution. (2) Control the mass ratio of complexing solution and isopropanol to 100:10, keep the stirring state unchanged, add isopropanol to complexing solution, heat to 40°C in water bath, stir for 15 min, and then cool to 25°C to obtain complexing-alcohol mixture. (3) The mass ratio of 36% hydrochloric acid solution and complex-alcohol mixture is controlled to be 0.5:100. After the 36% hydrochloric acid solution is added dropwise to the complex-alcohol mixture, it is degassed under a vacuum of -0.08MPa for 5 minutes. After degassed, it is left to stand and age for 12 hours to obtain selective pickling solution.

[0069] Example 1 A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Quartz sand (with an initial uranium content of 340 ppb and an initial thorium content of 420 ppb) was added to a composite cleaning solution (prepared from Preparation Example 1) with a mass of 3 times its own weight. The mixture was stirred and cleaned at 200 rpm for 90 min at 40 °C. Solid-liquid separation was then performed, and the mixture was washed with deionized water until the pH value reached 6 to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand at 850℃ in an atmosphere with 10% oxygen by volume for 4 hours to obtain heat-treated quartz sand. Step 3: Heat-treated quartz sand is added to cooling water at 10°C at a mass ratio of 1:12 and rapidly cooled for 15 seconds. Then it is crushed and screened to obtain crushed quartz sand with a particle size of 0.1 mm. Step 4: At a stirring rate of 100 rpm, the crushed quartz sand is added to a selective acid washing solution (prepared from Preparation Example 4) with a mass of 4 times its own weight. The mixture is reacted at 60°C and 0.2 MPa for 8 hours. After the reaction is completed, solid-liquid separation is performed, and the mixture is washed with deionized water until neutral. Then it is dried at 100°C for 6 hours to obtain low radioactivity quartz sand.

[0070] Example 2 A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Quartz sand (with an initial uranium content of 340 ppb and an initial thorium content of 420 ppb) was added to a composite cleaning solution (prepared from Preparation Example 2) with a mass of 4 times its own weight. The mixture was stirred and cleaned at 300 rpm for 50 min at 50 °C. Solid-liquid separation was then performed, and the mixture was washed with deionized water until the pH value reached 6.5 to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand at 900℃ in an atmosphere with an oxygen volume fraction of 15% for 3 hours to obtain heat-treated quartz sand. Step 3: Heat-treated quartz sand is added to cooling water at 20°C at a mass ratio of 1:15 and rapidly cooled for 20 seconds. Then it is crushed and sieved to obtain crushed quartz sand with a particle size of 0.5 mm. Step 4: At a stirring rate of 200 rpm, the crushed quartz sand is added to a selective acid washing solution (prepared from Preparation Example 5) with a mass of 5 times its own weight. The mixture is reacted at 70°C and 0.5 MPa for 6 hours. After the reaction is completed, solid-liquid separation is performed, and the mixture is washed with deionized water until neutral. Then it is dried at 120°C for 4 hours to obtain low radioactivity quartz sand.

[0071] Example 3 A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Quartz sand (with an initial uranium content of 340 ppb and an initial thorium content of 420 ppb) was added to a composite cleaning solution (prepared from Preparation Example 3) with a mass of 5 times its own weight. The mixture was stirred and cleaned at 60°C and 400 rpm for 30 min. Solid-liquid separation was then performed, and the mixture was washed with deionized water until the pH value reached 7 to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand at 1000℃ in an atmosphere with an oxygen volume fraction of 20% for 2 hours to obtain heat-treated quartz sand. Step 3: Heat-treated quartz sand is added to cooling water at 30°C at a mass ratio of 1:18 and rapidly cooled for 30 seconds. Then it is crushed and screened to obtain crushed quartz sand with a particle size of 0.8 mm. Step 4: At a stirring rate of 300 rpm, the crushed quartz sand is added to a selective acid washing solution (prepared from Preparation Example 6) with a mass of 6 times its own weight. The mixture is reacted at 90°C and 0.8 MPa for 4 hours. After the reaction is completed, solid-liquid separation is performed, and the mixture is washed with deionized water until neutral. Then it is dried at 150°C for 2 hours to obtain low radioactivity quartz sand.

[0072] To verify the overall performance of the method for eliminating radioactive elements in quartz crystals provided by this invention, comparative examples 1-5 were set up, wherein: Comparative Example 1 Comparative Example 1 is the same as Example 1, except that the composite cleaning solution prepared in Preparation Example 1 is replaced with the non-dispersible composite cleaning solution prepared in Comparative Preparation Example 1. Specifically: A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Quartz sand (with an initial uranium content of 340 ppb and an initial thorium content of 420 ppb) was added to a non-dispersible composite cleaning solution (prepared from Comparative Preparation Example 1) at 3 times its own weight. The solution was stirred and cleaned at 200 rpm for 90 min at 40 °C. Solid-liquid separation was then performed, and the solution was washed with deionized water until the pH value reached 6 to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand at 850℃ in an atmosphere with 10% oxygen by volume for 4 hours to obtain heat-treated quartz sand. Step 3: Heat-treated quartz sand is added to cooling water at 10°C at a mass ratio of 1:12 and rapidly cooled for 15 seconds. Then it is crushed and screened to obtain crushed quartz sand with a particle size of 0.1 mm. Step 4: At a stirring rate of 100 rpm, the crushed quartz sand is added to a selective acid washing solution (prepared from Preparation Example 4) with a mass of 4 times its own weight. The mixture is reacted at 60°C and 0.2 MPa for 8 hours. After the reaction is completed, solid-liquid separation is performed, and the mixture is washed with deionized water until neutral. Then it is dried at 100°C for 6 hours to obtain low radioactivity quartz sand.

[0073] Comparative Example 2 Comparative Example 2 is the same as Example 1, except that the composite cleaning solution prepared in Preparation Example 1 is replaced with the composite cleaning solution prepared in Comparative Preparation Example 2. Specifically: A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Quartz sand (with an initial uranium content of 340 ppb and an initial thorium content of 420 ppb) was added to a composite cleaning solution (prepared from Comparative Preparation Example 2) with a mass of 3 times its own weight. The mixture was stirred and cleaned at 200 rpm for 90 min at 40 °C. Solid-liquid separation was then performed, and the mixture was washed with deionized water until the pH value reached 6 to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand at 850℃ in an atmosphere with 10% oxygen by volume for 4 hours to obtain heat-treated quartz sand. Step 3: Heat-treated quartz sand is added to cooling water at 10°C at a mass ratio of 1:12 and rapidly cooled for 15 seconds. Then it is crushed and screened to obtain crushed quartz sand with a particle size of 0.1 mm. Step 4: At a stirring rate of 100 rpm, the crushed quartz sand is added to a selective acid washing solution (prepared from Preparation Example 4) with a mass of 4 times its own weight. The mixture is reacted at 60°C and 0.2 MPa for 8 hours. After the reaction is completed, solid-liquid separation is performed, and the mixture is washed with deionized water until neutral. Then it is dried at 100°C for 6 hours to obtain low radioactivity quartz sand.

[0074] Comparative Example 3 Comparative Example 3 is the same as Example 1, except that the composite cleaning solution prepared in Preparation Example 1 is replaced with the composite cleaning solution prepared in Comparative Preparation Example 3. Specifically: A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Quartz sand (with an initial uranium content of 340 ppb and an initial thorium content of 420 ppb) was added to a composite cleaning solution (prepared from Comparative Preparation Example 3) with a mass of 3 times its own weight. The mixture was stirred and cleaned at 40°C and 200 rpm for 90 min. Solid-liquid separation was then performed, and the mixture was washed with deionized water until the pH value reached 6 to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand at 850℃ in an atmosphere with 10% oxygen by volume for 4 hours to obtain heat-treated quartz sand. Step 3: Heat-treated quartz sand is added to cooling water at 10°C at a mass ratio of 1:12 and rapidly cooled for 15 seconds. Then it is crushed and screened to obtain crushed quartz sand with a particle size of 0.1 mm. Step 4: At a stirring rate of 100 rpm, the crushed quartz sand is added to a selective acid washing solution (prepared from Preparation Example 4) with a mass of 4 times its own weight. The mixture is reacted at 60°C and 0.2 MPa for 8 hours. After the reaction is completed, solid-liquid separation is performed, and the mixture is washed with deionized water until neutral. Then it is dried at 100°C for 6 hours to obtain low radioactivity quartz sand.

[0075] Comparative Example 4 Comparative Example 4 is the same as Example 1, except that the selective pickling solution prepared in Preparation Example 4 is replaced with the selective pickling solution prepared in Comparative Preparation Example 4. Specifically: A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Quartz sand (with an initial uranium content of 340 ppb and an initial thorium content of 420 ppb) was added to a composite cleaning solution (prepared from Preparation Example 1) with a mass of 3 times its own weight. The mixture was stirred and cleaned at 200 rpm for 90 min at 40 °C. Solid-liquid separation was then performed, and the mixture was washed with deionized water until the pH value reached 6 to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand at 850℃ in an atmosphere with 10% oxygen by volume for 4 hours to obtain heat-treated quartz sand. Step 3: Heat-treated quartz sand is added to cooling water at 10°C at a mass ratio of 1:12 and rapidly cooled for 15 seconds. Then it is crushed and screened to obtain crushed quartz sand with a particle size of 0.1 mm. Step 4: At a stirring rate of 100 rpm, the crushed quartz sand was added to a selective acid washing solution (prepared from Comparative Preparation Example 4) with a mass of 4 times its own weight. The mixture was reacted at 60°C and 0.2 MPa for 8 h. After the reaction was completed, solid-liquid separation was performed, and the mixture was washed with deionized water until neutral. Then it was dried at 100°C for 6 h to obtain low radioactivity quartz sand.

[0076] Comparative Example 5 Comparative Example 5 is the same as Example 1, except that the selective pickling solution prepared in Preparation Example 4 is replaced with the selective pickling solution prepared in Comparative Preparation Example 5. Specifically: A method for eliminating radioactive elements from quartz crystals includes the following steps: Step 1: Quartz sand (with an initial uranium content of 340 ppb and an initial thorium content of 420 ppb) was added to a composite cleaning solution (prepared from Preparation Example 1) with a mass of 3 times its own weight. The mixture was stirred and cleaned at 200 rpm for 90 min at 40 °C. Solid-liquid separation was then performed, and the mixture was washed with deionized water until the pH value reached 6 to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand at 850℃ in an atmosphere with 10% oxygen by volume for 4 hours to obtain heat-treated quartz sand. Step 3: Heat-treated quartz sand is added to cooling water at 10°C at a mass ratio of 1:12 and rapidly cooled for 15 seconds. Then it is crushed and screened to obtain crushed quartz sand with a particle size of 0.1 mm. Step 4: At a stirring rate of 100 rpm, the crushed quartz sand was added to a selective acid washing solution (prepared from Comparative Preparation Example 5) with a mass of 4 times its own weight. The mixture was reacted at 60°C and 0.2 MPa for 8 h. After the reaction was completed, solid-liquid separation was performed, and the mixture was washed with deionized water until neutral. Then it was dried at 100°C for 6 h to obtain low radioactivity quartz sand.

[0077] The comprehensive performance of the low-radioactivity quartz crystals prepared in Examples 1-3 and Comparative Examples 1-5 of this invention was tested respectively.

[0078] 1. Determination of the content of radionuclides Weigh 100.0 g of quartz sand sample and place it in a 250 mL polytetrafluoroethylene digestion vessel. Add 10 mL of hydrofluoric acid and 5 mL of nitric acid. Digest the sample in a microwave digester with programmed temperature increase (heat to 120 °C within 10 min and hold for 5 min, then heat to 200 °C within 20 min and hold for 30 min). After cooling, dilute to a 50 mL volumetric flask to obtain the test solution. Use an inductively coupled plasma mass spectrometer (RF power 1550 W, carrier gas flow rate 1.05 L / min) to determine the intensity of uranium (U) and thorium (Th) in the test solution. Calculate the content using the standard curve method. Three parallel tests are required, with a relative standard deviation of less than 5%.

[0079] 2. Physical and chemical property determination 2.1 Purity determination The quartz sand sample was dried at 105℃ for 2 hours. 4.0g of the sample was mixed with 0.9g of microcrystalline cellulose and pressed into tablets. The purity of SiO2 was determined by wavelength dispersive X-ray fluorescence spectrometry (voltage 30kV, current 100mA).

[0080] 2.2 Lattice Integrity Measurement The quartz sand sample was dried at 105℃ for 4 hours. After cooling, it was ground into a uniform powder using an agate mortar. An appropriate amount of powder was filled into the groove of the glass sample holder, and the surface was flattened with a glass slide. An X-ray diffractometer was used with a Cu-Kα ray source (λ=1.5406Å), the tube voltage was set to 40kV, the tube current to 40mA, and the scanning range was set to 10°-80° (2θ) in continuous scanning mode, with a step size of 0.02° and a scanning speed of 4° / min. After data acquisition, the characteristic diffraction peak (2θ=26.6°) of the (101) crystal plane of the quartz crystal was located, and its full width at half maximum (FWHM) was calculated using the instrument software.

[0081] 2.3 Deep ultraviolet transmittance A dry quartz sand sample was uniformly mixed with optical-grade epoxy resin at a 1:1 mass ratio. The mixture was then pressed into a transparent sheet with a diameter of 25 mm and a thickness of 2.0 mm in a mold. After curing, both sides of the sheet were optically polished. A dual-beam UV-Vis spectrophotometer was used with air as a reference. The sample sheet was placed vertically in the sample optical path. The spectral scanning range was set to 200-400 nm, the scanning interval was 1 nm, and the slit width was 2 nm. After the instrument was preheated and stabilized, baseline correction was performed. The sample was then scanned, and the transmittance at a wavelength of 250 nm was measured.

[0082] 2.4 Dielectric Loss Quartz sand samples were cut into circular pieces with a diameter of 10 mm and a thickness of 0.5 mm. Gold electrodes were deposited on both sides to form a parallel plate capacitor structure. The dielectric loss (tanδ) of the samples was measured using an impedance analyzer (Agilent 4294A) at a frequency of 1 MHz. The test conditions were room temperature 25°C and oscillation voltage 1.0 V.

[0083] 3. Determination of matrix corrosivity Weigh 50.00 g of quartz crystal sample (denoted as m0), dry it at 105℃ for 4 h to constant weight, and then place it in a desiccator to cool to room temperature; completely immerse the sample in 500 mL of selective acid washing solution (pH 2.0), and react for 3 h at 80℃, 0.5 MPa and a stirring rate of 150 rpm (simulating the core process of the patent); after the reaction, perform solid-liquid separation, wash repeatedly with deionized water until the filtrate is neutral, then dry the solid at 105℃ for 4 h to constant weight, cool it and weigh its mass (denoted as m1), calculate the mass loss according to the formula dissolution rate = (m0-m1) / m0×100%, and take the average value of three parallel tests.

[0084] The test results are shown in Table 1: Table 1. Data on the determination of radionuclide content, physicochemical properties, and matrix corrosivity of low-radioactive quartz sand in Examples 1-3 and Comparative Examples 1-5. As shown in Table 1, the low-radioactivity quartz sands prepared in Examples 1-3 of this invention have uranium and thorium contents reduced to the ppb level (<3ppb), and silica purity significantly improved (≥99.89%), while maintaining excellent physicochemical properties, including high lattice integrity (XRD full width at half maximum ≤0.10). 0 High ultraviolet transmittance (≥92.30%) and extremely low dielectric loss (≤1×10⁻⁻⁶). 4 Furthermore, the matrix erosion rate of the method of the present invention is extremely low (≤0.05%), which is far superior to the traditional strong acid process, proving its high efficiency and selectivity.

[0085] As can be seen from Example 1 and Comparative Examples 1, 2, and 3, the absence of any one of the components, such as the chelating dispersant (Comparative Example 1), the composite oxidant (Comparative Example 2), or the silane coupling agent (Comparative Example 3), will lead to a significant increase in the residual amount of radioactive elements in the final product, and the purity and various performance indicators will be inferior to those of Example 1. This indicates that the synergistic effect of the components of the composite cleaning liquid in this invention to effectively pretreat the surface of quartz sand is a necessary prerequisite for achieving subsequent deep purification and obtaining high-performance products.

[0086] As can be seen from Example 1 and Comparative Example 4, when the selective pickling solution in Comparative Example 4 lacks the organic complexing agent (disodium 1,2-dihydroxybenzene-3,5-disulfonic acid), the removal effect on uranium and thorium is extremely poor, and their content is basically maintained at a high level. The overall performance of the product is the worst. This fully demonstrates that the organic complexing agent has a highly specific complexing ability for radioactive elements, which is the key technology for the targeted removal of radioactive impurities in this invention.

[0087] As can be seen from Example 1 and Comparative Example 5, when crown ether compounds are missing in the selective pickling solution of Comparative Example 5, although the organic complexing agent is still present, the removal efficiency of uranium and thorium is greatly reduced, and the product performance is far inferior to that of Example 1. This confirms that crown ether compounds, as phase transfer catalysts, play an indispensable role in effectively "extracting" and transferring radioactive ion-complexes in lattice defects or microcracks to the main body of the pickling solution, and are an important guarantee for ensuring the depth of purification.

[0088] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for eliminating radioactive elements from quartz crystals, characterized in that, Includes the following steps: Step 1: Add the quartz sand to the composite cleaning solution, stir and clean at 40-60℃ for 30-90 minutes, then perform solid-liquid separation and water washing to obtain pretreated quartz sand. Step 2: Heat-treat the pretreated quartz sand in an oxygen-containing atmosphere at 850-1000℃ for 2-4 hours to obtain heat-treated quartz sand. Step 3: Immerse the heat-treated quartz sand in cooling water at 10-30℃ for rapid cooling for 15-30 seconds, then crush and screen to obtain crushed quartz sand; Step 4: Under stirring, add crushed quartz sand to selective pickling solution and carry out pickling reaction at 0.2-0.8 MPa. After the reaction is completed, perform solid-liquid separation, washing and drying to obtain low radioactive quartz sand.

2. The method for eliminating radioactive elements in quartz crystals according to claim 1, characterized in that, In step 1, the mass ratio of quartz sand to composite cleaning solution is 1:3-5.

3. The method for eliminating radioactive elements in quartz crystals according to claim 1, characterized in that, The composite cleaning solution in step 1 is prepared by the following method: S1. Under stirring, citric acid, sodium gluconate and chelating dispersant are added sequentially to deionized water. The system is then heated to 50-60℃ and stirred for 30-50 minutes to obtain the chelated base solution. S2. Reduce the system temperature to 30-40℃, add hydrogen peroxide and ammonium persulfate to the chelating base solution, stir the reaction for 30-60 min, then introduce inert gas and bubble purge for 20-30 min to obtain the oxidation cleaning solution; S3. Add silane coupling agent and corrosion inhibitor to the oxidizing cleaning solution, stir and react at 30-40℃ for 1-2 hours. After the reaction is completed, cool down to 20-25℃ and stir and mature for 2-4 hours. Then adjust the pH of the system to 4.5-5.5 with an acidity regulator to obtain the composite cleaning solution.

4. The method for eliminating radioactive elements in quartz crystals according to claim 3, characterized in that, The chelating dispersant in S1 is selected from at least one of low molecular weight sodium polyacrylate, maleic acid-acrylic acid copolymer, and polyepoxysuccinic acid.

5. The method for eliminating radioactive elements in quartz crystals according to claim 3, characterized in that, The silane coupling agent in S3 is a mixture of γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

6. The method for eliminating radioactive elements in quartz crystals according to claim 1, characterized in that, The oxygen volume fraction of the oxygen-containing atmosphere in step 2 is 10-20%.

7. The method for eliminating radioactive elements in quartz crystals according to claim 1, characterized in that, The particle size of the crushed quartz sand in step 3 is 0.1-0.8 mm.

8. The method for eliminating radioactive elements in quartz crystals according to claim 1, characterized in that, In step 4, the mass ratio of crushed quartz sand to selective pickling solution is 1:4-6.

9. The method for eliminating radioactive elements in quartz crystals according to claim 1, characterized in that, The selective pickling solution in step 4 is an aqueous solution containing crown ether compounds, inorganic acids, alcohol cosolvents, and organic complexing agents.

10. The method for eliminating radioactive elements in quartz crystals according to claim 1, characterized in that, The selective pickling solution in step 4 is prepared by the following steps: (1) Under stirring, add organic complexing agent and crown ether compound to deionized water in sequence, and stir under ultrasonic action for 10-15 min to obtain complexing agent-crown ether solution; (2) Keep the stirring state unchanged, add alcohol co-solvent to the complexing agent-crown ether solution, heat in a water bath to 40-45℃, stir for 10-15 min, and then cool to 25-30℃ to obtain complexing agent-crown ether-alcohol mixture; (3) After adding inorganic acid to the complexing agent-crown ether-alcohol mixture, degas it under a vacuum of -0.08 to -0.10 MPa for 5-10 min. After degassing, let it stand and age for 12-24 h to obtain selective pickling solution.

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