Method for preparing ultra-high purity quartz sand by deep purification

Abstract

The present application relates to a kind of methods for preparing ultra-high purity quartz sand by deep purification, belong to high-purity quartz high-efficiency preparation and non-metallic mineral fine and deep processing technical field.The method is placed in supercritical reaction device with quartz sand raw material, and mixed fluid of composite entraining agent and supercritical carbon dioxide is introduced into the device to carry out reaction, after separation, washing and drying, high-purity quartz sand product is obtained;The composite entraining agent is the combination of acid medium and metal complexing agent;The volume fraction of the acid medium in the mixed fluid is 0.5%~5%, and the acid medium is hydrogen fluoride and / or hydrogen chloride.The method has the advantages of simple process flow, high purification efficiency, controllable purification degree and stable product performance.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing ultra-high-purity quartz sand through deep purification, and belongs to the technical fields of high-purity quartz efficient preparation and non-metallic ore deep processing. BACKGROUND

[0002] High-purity quartz is an indispensable key basic material for the information industry such as semiconductors, photovoltaics and optical communications. With the rapid development of photovoltaic and semiconductor technologies, the demand for 4N8-grade (SiO2 content is greater than or equal to 99.998%) and above ultra-high-purity quartz sand is increasing day by day.

[0003] According to different element occurrence forms, the impurities in quartz sand can be divided into associated mineral impurities, inclusion impurities and crystal structure impurities. The associated mineral impurities can be removed by flotation, magnetic separation and the like, and the inclusion impurities can be removed by roasting, acid leaching and the like, but the removal degree is restricted by the types, quantity and process parameters of the inclusions. The crystal structure impurities exist in the quartz crystal lattice in the form of isomorphism or charge balance, and form strong chemical bonding, and acid leaching, chlorination roasting and the like have a certain removal effect, but there are uncontrollable removal effect, high process energy consumption and strict requirements on the quality of raw materials.

[0004] A purification method for removing quartz inclusions is disclosed in a Chinese patent (publication number CN120774427 A), which comprises the following steps: calcining quartz sand raw materials at high temperature for a certain period of time, and then taking them out and quickly putting them into cold water for quenching; after the quartz sand is dehydrated, it is sent into a microwave reactor, heated to a set temperature and kept for a period of time; after the reaction is completed, the quartz sand is washed with ultrapure water; the quartz sand is loaded into a high-temperature and high-pressure reactor, and a mixed gas of supercritical carbon dioxide and hydrogen fluoride is introduced, and the temperature and pressure are kept for a period of time; after the reaction is completed, the gas is discharged, and a high-purity quartz is obtained. The scheme pre-treats the quartz sand raw materials through two-stage heat processing, the first-stage heat treatment causes the quartz crystal form to change, improves the brittleness and weakens the strength of the quartz particles; the second-stage heat treatment uses microwaves to heat the inclusions, under the action of thermal expansion, the force is transmitted from the inside of the inclusion to the outside, so that cracks are generated and notches communicating with the outside are formed; finally, the high diffusivity and solubility of the supercritical gas enable it to enter the inside of the inclusions through the tiny cracks and dissolve the impurities such as salts in the inclusions, so as to realize the removal of the inclusion impurities. The scheme needs two-stage high-temperature heat treatment and quenching, and the removal of the inclusion impurities is realized by using the supercritical gas through the generation of cracks, which has high equipment complexity and operation difficulty and a complex process, and the high-temperature treatment also causes damage to the crystal structure of the material.

[0005] Therefore, efficient, deep and controllable removal of inclusions and crystal structure impurities has become the key to the preparation of ultra-high purity quartz. SUMMARY

[0006] In view of the low removal efficiency, uncontrollable removal degree and high energy consumption of high-temperature treatment of inclusions and crystal structure impurities in the existing preparation process of ultra-high purity quartz sand, the purpose of the present application is to provide a method for deep purification and preparation of ultra-high purity quartz sand.

[0007] To achieve the above-mentioned purpose, the first aspect of the present application provides a method for deep purification and preparation of ultra-high purity quartz sand, comprising the following steps:

[0008] The quartz sand raw material is placed in a supercritical reaction device, a mixed fluid of a composite entraining agent and supercritical carbon dioxide is introduced into the device for reaction, and after separation, washing and drying, a high-purity quartz sand product is obtained.

[0009] The composite entraining agent is a combination of an acid medium and a metal complexing agent.

[0010] The volume fraction of the acid medium in the mixed fluid is 0.5% to 5%, and the acid medium is hydrogen fluoride and / or hydrogen chloride.

[0011] The technical scheme of the present application is realized through the synergistic effect of efficient mass transfer of supercritical carbon dioxide fluid, directional micro-etching of quartz lattice by acid medium, and immediate extraction of released metal ions by metal complexing agent. Among them, supercritical carbon dioxide as a transport medium, with its diffusion coefficient close to that of gas and its solubility close to that of liquid, can efficiently transport the reaction reagents to the quartz inclusion and crystal structure impurity sites, and the acid medium as the etching medium can dissociate the inclusions and crystal structure impurities. Excessive acid concentration per unit volume not only causes reagent waste, but also causes the reaction system to be too wet locally, which may even separate from the supercritical homogeneous phase, thereby losing the advantage of high mass transfer of supercritical CO2, and when the acid concentration is higher than 5%, it will cause the quartz main body to dissolve, especially in the HF-containing system, even new defects may be generated in the quartz sand. If the acid concentration is too low, the reaction concentration is too low, the mass transfer driving force is insufficient, the reaction rate is slow, a longer time or larger reactor is needed, which affects the equipment utilization and production efficiency, and when the acid concentration is lower than 0.5%, it is difficult to effectively release impurities, resulting in poor purification effect. Further, CO2, H2O and other components in the inclusion can be dissolved in supercritical CO2, the metal impurities combine with the metal complexing agent in the system to form stable complexes, and then dissolve in the supercritical CO2 phase, so that they are continuously carried away from the reaction system by the flowing fluid, realizing the deep removal of impurities. The problems of slow diffusion and low efficiency of traditional strong acid in quartz sand body phase are effectively overcome.

[0012] As a preferred scheme, the mass ratio of the quartz sand raw material to the mixed fluid is 1:5 to 1:15. If the ratio is too low, the fluid volume corresponding to unit mass of quartz sand will be too large, although it can provide extremely sufficient flow and mass transfer conditions to ensure that the impurity complex is quickly carried away, but it will lead to low production efficiency and poor economy. If the ratio is too high, the solid load per unit volume of fluid will be too large, and the supercritical fluid will be difficult to uniformly and fully wrap and penetrate the quartz sand particles, especially at high solid content, the particles are easy to agglomerate, leading to uneven reaction and affecting the consistency of product purity. The volume ratio in this preferred case can ensure that the reaction interface always maintains effective etching and complexing under the condition of continuous flow of supercritical CO2, thereby optimizing the amount of reagents while ensuring reaction efficiency.

[0013] As a preferred solution, the metal complexing agent is selected from at least one of acetylacetone, 1,1-difluoroacetylacetone, hexafluoroacetylacetone and trifluoroacetylacetone. The carbonyl and enol groups in the molecular structure of the metal complexing agent in the preferred case can provide two coordinated oxygen atoms to form a stable six-membered ring chelate with the target metal ions such as Al, Fe, etc., and the chelate structure is stable, electrically neutral, and wrapped by an organic group, showing high hydrophobicity and being soluble in non-polar supercritical CO2. The preferred solution can transfer ionic impurities from the quartz solid phase structure to the supercritical CO2 fluid phase.

[0014] As a preferred solution, the mass fraction of the metal complexing agent in the mixed fluid is 1% to 10%. When the concentration of the metal complexing agent is lower than 1%, the dissociated metal ions cannot be effectively captured in time, and the uncomplexed ions will be re-adsorbed or deposited on the quartz surface and micropores, affecting the purification effect. When the concentration is higher than 10%, not only is the reagent wasted, but also competitive aggregation between metal complexing agent molecules is likely to occur, which affects the coordination efficiency with metal ions and increases the burden of subsequent separation.

[0015] The acid concentration and the metal complexing agent concentration are set based on the balance between deep removal of impurities and minimization of quartz dissolution loss. The present application efficiently realizes the removal of inclusions and crystal structure impurities through the synergistic optimization of acid medium and metal complexing agent concentration, and in combination with the remaining technical features of the present application, providing a new technical path for the preparation of semiconductor and electronic-grade ultra-high purity quartz sand.

[0016] As a preferred solution, the temperature of the reaction is 40 to 80℃, the pressure is 10 to 25MPa, and the time is 0.5 to 4h. In the present application, the synergistic deep impurity removal can be more efficiently realized under the preferred conditions. If the reaction temperature is lower than 40℃, the supercritical CO2 density is too high, the viscosity is relatively large, and the diffusion performance is reduced, which will make the kinetics rate of acid etching reaction and complexing reaction too slow, requiring a long purification time. If it is higher than 80℃, although the reaction rate can be improved, the non-selective etching rate of acid to the quartz body will increase exponentially, intensifying the risk of non-selective etching of the quartz body and damaging the microstructure of the quartz body, and also increasing the energy consumption of the system. Controlling the pressure in the range of 10 to 25MPa can ensure that CO2 is in a stable supercritical state, and the supercritical CO2 has a moderate density, which can not only ensure sufficient solubility of the entraining agent and metal complex, but also maintain high diffusivity close to gas, which is beneficial to the penetration into the particle interior.

[0017] As a preferred solution, the purity of the acid medium is ≥99.99%, and the purity of the metal complexing agent is ≥99.5%. If the purity of the acid medium and the metal complexing agent is low, impurity elements will be introduced during the purification process, affecting the purity of the product.

[0018] As a preferred scheme, the SiO2 content of the quartz sand raw material is ≥99.99%, and the particle size is 70-350 μm. In this preferred case, the purification method of the present application is more economical and has higher purification efficiency. The purity of the quartz sand raw material determines the impurity load of the subsequent treatment. When the SiO2 content is less than 99.99%, the impurity content of the raw material is high, and even residual associated mineral impurities are not removed. These impurities will consume a large amount of reagent, greatly increasing the invalid consumption of the acid medium and the difficulty of subsequent separation and purification. 70-350 μm is the typical particle size range of ultra-high purity quartz sand. Although the powder with a particle size less than 70 μm has a large specific surface area, it is easy to be cemented in the reaction system, hindering the uniform penetration of the supercritical fluid, resulting in uneven local reaction. At the same time, the fine powder is easily entrained by the gas flow when it is discharged, causing material loss and safety risk. The particles with a particle size greater than 350 μm have a long path for the internal impurities to diffuse to the surface, and a very long reaction time is required to achieve deep purification, which is inefficient.

[0019] As a preferred scheme, the SiO2 content of the quartz sand product is ≥99.995%.

[0020] As a more preferred scheme, the SiO2 content of the quartz sand product is ≥99.998%, which is 4N8 grade quartz sand. The quartz sand product obtained by the purification method of the present application has complete crystal shape and no significant structural damage, and is suitable for the manufacture of high-end semiconductors, photovoltaics and precision optical devices.

[0021] Compared with the prior art, the present application has at least the following advantages:

[0022] (1) The present application creatively applies supercritical fluid extraction technology to the deep removal of quartz sand inclusions and crystal structure impurities for the first time. Through the synergistic mechanism of acid medium etching and metal complexing agent extraction, deep controllable removal of impurities that cannot be achieved by traditional acid leaching and chlorination is achieved, breaking through the technical bottleneck of ultra-high purity quartz preparation.

[0023] (2) Compared with the prior art of CN111874913A, CN120117613A, CN117623320A and the like, the present application is carried out at a temperature much lower than chloridizing roasting, the energy consumption is significantly reduced, and the problems of quartz phase change, lattice damage and thermal stress caused by high temperature are completely avoided, and the product quality is better. Compared with the prior art of CN120774427A and the like, by coupling the metal complexing agent with the acid, the impurities in the inclusions can be effectively dissolved, and the internal impurities of the crystal can be removed, that is, by using one-step supercritical reaction, the deep purification of quartz sand is realized. In addition, the present application does not need two-stage high-temperature heat treatment and quenching, which not only reduces the complexity and difficulty of operation, but also reduces the high energy consumption and damage to the crystal structure of the material caused by high-temperature treatment. Compared with the prior art of CN1894050A and the like, by constructing a composite entraining agent and supercritical CO2, that is, the synergy of efficient mass transfer of critical carbon dioxide fluid, etching of acid medium and extraction of metal complexing agent, the internal impurities of quartz sand are removed, while CN1894050A is based on surface dissolution reaction to clean the surface of semiconductor devices, so benzene and / or alcohol and / or organic acid are used, and the reaction is limited to solder residue, metal oxides and etching residue produced on the surface in semiconductor manufacturing, and does not involve internal inclusions or lattice impurities, and the reaction type and process are essentially different.

[0024] (3) The process of the present application is green and environmentally friendly, supercritical CO2 is non-toxic and easy to recycle and use, and the reagent consumption is much lower than that of traditional acid leaching process, which reduces the generation and treatment pressure of acid wastewater from the source and is environmentally friendly.

[0025] (4) The process flow of the present application is simple, the parameters are controllable, the supercritical equipment used is mature, it is easy to integrate with the existing high-purity quartz production line, and it has broad prospects for large-scale industrial application. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values disclosed in this document are not limited to the precise values recited as the exact dimensions are not critical to the present application. The endpoints of the ranges and the values of individual points are not to be understood as limited to the precise values recited as the exact dimensions are not critical to the present application. The ranges and individual points within the ranges can be combined to form new ranges, and the new ranges are to be considered disclosed herein.

[0027] The present application will be further described in conjunction with specific examples, but the protection scope of the present application is not limited to the following specific examples. Obviously, the following described examples are only a part of the examples, and all other examples obtained by those skilled in the art without creative labor still belong to the protection scope of the present application.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0029] Example 1

[0030] Quartz sand with a SiO2 content of 99.993% and a particle size of 100~220μm was fed into a supercritical reactor. A mixed fluid of HF, acetylacetone, hexafluoroacetylacetone, and supercritical carbon dioxide was introduced into the reactor for reaction. The purity of HF was 99.99%, acetylacetone was 99.5%, and hexafluoroacetylacetone was 99.7%. The mass ratio of quartz sand to the mixed fluid was 1:8. The volume concentration of HF in the mixed fluid was 2%, the mass fraction of acetylacetone was 3%, and the mass fraction of hexafluoroacetylacetone was 2%. The reaction temperature was maintained at 60℃, the pressure at 22 MPa, and the reaction time was 2h. After the reaction, the product was separated, washed with ultrapure water, and dried to obtain ultrapure quartz sand. The SiO2 content was found to be 99.9986%.

[0031] Example 2

[0032] Quartz sand with a SiO2 content of 99.994% and a particle size of 250~350μm was fed into a supercritical reactor. A mixed fluid of HCl, acetylacetone, and supercritical carbon dioxide was introduced into the reactor for reaction. The purity of HCl was 99.99%, the purity of acetylacetone was 99.5%, the mass ratio of quartz sand to the mixed fluid was 1:5, the volume concentration of HCl in the mixed fluid was 5%, and the mass fraction of acetylacetone was 8%. The reaction temperature was maintained at 80℃, the pressure at 10 MPa, and the reaction time was 4h. After the reaction, the product was separated, washed with ultrapure water, and dried to obtain ultrapure quartz sand. The SiO2 content was found to be 99.9993%.

[0033] Example 3

[0034] Quartz sand with a SiO2 content of 99.99% and a particle size of 70-150 μm was fed into a supercritical reactor. A mixed fluid of HF, HCl, 1,1-difluoroacetylacetone, hexafluoroacetylacetone, and supercritical carbon dioxide was introduced into the reactor for reaction. The purity of HF and HCl was 99.99%, the purity of hexafluoroacetylacetone was 99.6%, the mass ratio of quartz sand to the mixed fluid was 1:15, the volume concentration of HF in the mixed fluid was 1.0%, the volume concentration of HCl was 2.5%, the mass fraction of 1,1-difluoroacetylacetone was 7%, and the mass fraction of hexafluoroacetylacetone was 2%. The reaction temperature was maintained at 40℃, the pressure at 25 MPa, and the reaction time was 1 h. After the reaction, the product was separated, washed with ultrapure water, and dried to obtain ultrapure quartz sand. The SiO2 content was found to be 99.9988%.

[0035] Example 4

[0036] Quartz sand with a SiO2 content of 99.993% and a particle size of 120~220μm was fed into a supercritical reactor. A mixed fluid of HF, acetylacetone, hexafluoroacetylacetone, and supercritical carbon dioxide was introduced into the reactor for reaction. The purity of HF was 99.99%, and the purity of acetylacetone and hexafluoroacetylacetone was 99.5%. The mass ratio of quartz sand to the mixed fluid was 1:10. The volume concentration of HF in the mixed fluid was 0.5%, the mass fraction of acetylacetone was 0.7%, and the mass fraction of hexafluoroacetylacetone was 0.3%. The reaction temperature was maintained at 75℃, the pressure at 18MPa, and the reaction time was 2h. After the reaction, the product was separated, washed with ultrapure water, and dried to obtain ultrapure quartz sand. The SiO2 content was found to be 99.9995%.

[0037] Example 5

[0038] Quartz sand with a SiO2 content of 99.995% and a particle size of 150~220μm was fed into a supercritical reactor. A mixed fluid of HF, HCl, trifluoroacetylacetone, and supercritical carbon dioxide was introduced into the reactor for reaction. The purity of HF and HCl was 99.99%, the purity of trifluoroacetylacetone was 99.7%, the mass ratio of quartz sand to the mixed fluid was 1:13, the volume concentration of HF in the mixed fluid was 2%, the volume concentration of HCl was 2%, and the mass fraction of trifluoroacetylacetone was 6%. The reaction temperature was maintained at 60℃, the pressure at 20MPa, and the reaction time was 0.4h. After the reaction, the product was separated, washed with ultrapure water, and dried to obtain ultrapure quartz sand. The SiO2 content was found to be 99.9986%.

[0039] Example 6

[0040] The only difference compared to Example 1 is that the reaction temperature was set to 35°C.

[0041] The purified quartz sand has a SiO2 content of 99.9961%.

[0042] Example 7

[0043] The only difference compared to Example 4 is that the system pressure is 7 MPa.

[0044] The purified quartz sand has a SiO2 content of 99.9955%.

[0045] Comparative Example 1

[0046] The only difference compared to Example 1 is that HF ​​is replaced with acetic acid.

[0047] The purified quartz sand product has a SiO2 content of 99.9932%.

[0048] Comparative Example 2

[0049] The only difference compared to Example 1 is that HF ​​is not added.

[0050] The purified quartz sand product has a SiO2 content of 99.9931%.

[0051] Comparative Example 3

[0052] The only difference compared to Example 1 is that no metal complexing agent is added.

[0053] The purified quartz sand product has a SiO2 content of 99.9947%.

[0054] Comparative Example 4

[0055] The only difference from Example 1 is that the metal complexing agent is difluoroacetone.

[0056] The purified quartz sand product has a SiO2 content of 99.9942%.

[0057] Comparative Example 5

[0058] The only difference compared to Example 4 is that the HF volume concentration in the mixed fluid is 0.3%.

[0059] The purified quartz sand has a SiO2 content of 99.9959%.

[0060] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for producing ultra-high purity quartz sand by deep purification, characterized by: The method comprises the following steps: The quartz sand raw material is placed in a supercritical reaction device, a mixed fluid of a composite entraining agent and supercritical carbon dioxide is introduced into the device for reaction, and then high-purity quartz sand products are obtained through separation, washing and drying; The composite entraining agent is a combination of an acid medium and a metal complexing agent; The volume fraction of the acid medium in the mixed fluid is 0.5%-5%, and the acid medium is hydrogen fluoride and / or hydrogen chloride; The metal complexing agent is at least one selected from acetylacetone, 1,1-difluoroacetylacetone, hexafluoroacetylacetone and trifluoroacetylacetone; The mass fraction of the metal complexing agent in the mixed fluid is 1%-10%.

2. The method for preparing ultra-high purity quartz sand by deep purification according to claim 1, characterized in that: The reaction temperature is 40-80℃, the pressure is 10-25MPa, and the time is 0.5-4h.

3. The method for preparing ultra-high purity quartz sand by deep purification according to claim 1 or 2, characterized in that: The purity of the acid medium is ≥99.99%, and the purity of the metal complexing agent is ≥99.5%.

4. The method for preparing ultra-high purity quartz sand by deep purification according to claim 1 or 2, characterized in that: The SiO2 content of the quartz sand raw material is ≥99.99%, and the particle size is 70μm-350μm.

5. The method for preparing ultra-high purity quartz sand by deep purification according to claim 1 or 2, characterized in that: The SiO2 content of the quartz sand product is ≥99.995%.

6. The method for preparing ultra-high purity quartz sand by deep purification according to claim 1 or 2, characterized in that: The mass ratio of the quartz sand raw material to the mixed fluid is 1:5-1:15.