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CN-120553721-B - High-purity quartz sand alkali metal targeted deep removal method

CN120553721BCN 120553721 BCN120553721 BCN 120553721BCN-120553721-B

Abstract

The invention relates to the technical field of purification or refining of silicon compounds, in particular to a high-purity quartz sand alkali metal targeted depth removal method, which comprises the steps of mixing quartz sand with silicon carbide abrasive, dry grinding, and then immersing ammonium fluoborate, nano titanium dioxide and graphene quantum dot in solution for etching; then complex leaching alkali metal in microwave field with compound solution containing HEDP, EDTMPA, crown ether and beta-cyclodextrin, decomposing the complex in the cooperation of ultraviolet light and electric field in a photoelectric desorption reactor, three-stage countercurrent washing with super-gravity rotating bed, repairing lattice with RF plasma, high temperature dehydroxylation in hydrogen atmosphere, and multistage cooperation to eliminate alkali metal deeply. The invention reduces the total alkali metal content of quartz sand, reduces energy consumption and waste liquid by the technologies of surface modification, composite complexation, photoelectric desorption and the like, improves the purity and performance of the material, and is suitable for the high-end fields of semiconductors and the like.

Inventors

  • XIA CHUNXIN
  • LU YI

Assignees

  • 河南皓新科技有限公司

Dates

Publication Date
20260512
Application Date
20250613

Claims (10)

  1. 1. The high-purity quartz sand alkali metal targeted depth removing method is characterized by comprising the following steps of: S1, surface nano-structured pretreatment Mixing quartz sand with silicon carbide abrasive, dry grinding in a planetary ball mill to form a micro-nano structure with the surface roughness Ra=0.2-0.5 mu m, then immersing into a mixed solution containing ammonium fluoborate (NH 4 BF 4 ), nano titanium dioxide and Graphene Quantum Dots (GQDs), and treating under an ultrasonic field to generate etching pits with uniform depth on the quartz surface, wherein the GQDs are adsorbed on the quartz surface through pi-pi accumulation, and the reaction formula is as follows: ; s2, double complexing agent co-leaching Preparing a composite complexing solution containing hydroxyethylidene diphosphonic acid (HEDP), ethylenediamine tetramethylene phosphonic acid (EDTMPA), beta-cyclodextrin and crown ether-18-crown-6, adding pretreated quartz sand, and stirring in a microwave field to form a triple complexing system; s3, photocatalysis-electrochemistry combined desorption Transferring the leaching solution to a photoelectric desorption reactor, taking quartz sand as a cathode, taking a platinum sheet as an anode, adding potassium persulfate (K 2 S 2 O 8 ) and FeCo-MOF-74, and reacting under the synergistic effect of ultraviolet light and a direct current electric field; s4, super-gravity reinforced washing Three-stage countercurrent washing is carried out by adopting a super-gravity rotating bed, deionized water is used for washing with the liquid-solid ratio of 10:1-15:1, and the single residence time is 10-30 seconds; S5, plasma assisted lattice repair And (3) placing the washed quartz sand into a radio frequency plasma reactor, treating for 10-30 minutes under the vacuum degree of 10-100Pa, repairing lattice defects by utilizing argon ion bombardment, and then carrying out heat treatment for 1-2 hours at the temperature of 1100-1200 ℃ in the hydrogen atmosphere.
  2. 2. The method for removing the high-purity quartz sand alkali metal targeted depth according to claim 1 is characterized by further comprising an S0 pre-dispersing step, wherein nano titanium dioxide and graphene quantum dots are mixed according to a mass ratio of 1:0.1-0.3, ethanol-water is used for ultrasonic dispersion to form a stable suspension, and the stable suspension is mixed with ammonium fluoborate solution to enable GQDs to be uniformly loaded on the surface of TiO 2 , so that a GQDs-TiO 2 composite catalyst is formed.
  3. 3. The method for removing the alkali metal targeted depth from the high-purity quartz sand according to claim 1, further comprising the step of adding perfluorooctanoic acid (PFOA) accounting for 0.5-2% of the volume of the complexing solution in S2, and forming an alkali metal ion-crown ether-PFOA ternary complex by utilizing the synergistic effect of a hydrophobic chain segment and crown ether.
  4. 4. The method for removing the high-purity quartz sand alkali metal targeted depth according to claim 1, wherein the metal site density of FeCo-MOF-74 in S3 is more than or equal to 1.5mmol/g, and Fe 3 +/Fe 2 + and Co 3 +/Co 2 + redox couple are generated under the action of an electric field.
  5. 5. The method for removing the high-purity quartz sand alkali metal targeted depth according to claim 1, wherein the mass transfer coefficient of the hypergravity washing in S4 is 5-8 times that of the traditional stirring washing.
  6. 6. The method for removing the alkali metal targeted depth from the high-purity quartz sand according to claim 1, wherein the ion bombardment flux of the plasma treatment in the step S5 is 10 13 -10 14 ions/cm 2 , the surface energy of the quartz sand after the treatment is reduced from 45mJ/m 2 to 28mJ/m 2 , and the subsequent adsorption of impurities is reduced.
  7. 7. The method for removing the alkali metal from the high-purity quartz sand in the targeted depth manner according to claim 1, wherein the Li content in the prepared high-purity quartz sand is less than or equal to 0.5ppm, the Rb content and the Cs content are less than or equal to 0.1ppm, and the total alkali metal content is less than or equal to 5ppm.
  8. 8. The method for removing the alkali metal from the high-purity quartz sand in the targeted depth mode according to claim 1, wherein the microwave-assisted mode in S2 reduces the activation energy of the complexing reaction from 65kJ/mol to 42kJ/mol, and the directional migration of alkali metal ions is realized through a dielectric heating effect, and the leaching selectivity coefficient is more than or equal to 50.
  9. 9. The method for removing the high-purity quartz sand alkali metal targeted depth according to claim 1, wherein the heating rate of the hydrogen heat treatment in the step S5 is controlled to be 8-15 ℃ per minute, and liquid nitrogen is introduced during cooling to enable the quartz sand to be cooled to room temperature within 30 minutes, so that a gradient structure with 100-150MPa of surface compressive stress is formed.
  10. 10. The method for removing the alkali metal targeted depth from the high-purity quartz sand according to claim 1, wherein when the prepared quartz sand is used for preparing a deep ultraviolet optical element, the absorption coefficient at 193nm wavelength is less than or equal to 0.01cm -1 , the fluorescence intensity is less than or equal to 10 3 cps, and the ArF photoetching objective lens material requirement is met.

Description

High-purity quartz sand alkali metal targeted deep removal method Technical Field The invention relates to the technical field of purification or refining of silicon compounds, in particular to a high-purity quartz sand alkali metal targeted deep removal method. Background The high-purity quartz sand is a core raw material for preparing high-end materials such as semiconductor wafers, deep ultraviolet optical glass, optical fiber preformed bars and the like, and the content of alkali metal (Na, K, li and the like) directly determines the dielectric constant, the thermal stability and the optical uniformity of the materials. For example, in a 193nm photoresist quartz substrate, na + content is less than or equal to 1ppm, otherwise, the expansion coefficient of the substrate in the photoetching process is fluctuated, and the pattern transfer accuracy is affected. However, the alkali metal impurities in the quartz sand mainly exist in two forms of lattice substitution (such as Na + to replace Si 4+) and surface adsorption, and the deep removal is difficult to realize by the traditional process, and the specific bottlenecks are as follows: Conventional hydrofluoric acid (HF) or hydrochloric acid leaching can only remove surface-adsorbed alkali metals, and is ineffective against impurities in the lattice. For example, conventional HF acid leaching typically has a Na content of 20-50ppm, which is not satisfactory for semiconductor grade (≤5 ppm). HF can indifferently etch quartz crystal lattice, so that SiO 2 has high loss rate, and simultaneously released Al 3+、Fe3+ and other impurities need secondary treatment. The stability constant of the hydroxycarboxylic acid complexing agent (such as EDTA) to alkali metal is low (log K 1n is less than or equal to 3), and the use of high concentration (more than or equal to 2 mol/L) is needed, so that the cost of waste liquid treatment is greatly increased. Alkali metal ions in micropores (aperture <20 nm) of quartz sand are difficult to diffuse into a solution body, and the effective mass transfer coefficient is less than 10 -9 m/s under the conventional stirring condition, and the reaction time is more than 12 hours. The traditional process consumes 50-100kg of HF (40%) per ton of quartz sand, generates 10-20m <3 > of acid waste liquid, and the treatment cost accounts for more than 30% of the total process cost. In order to promote the diffusion of deep impurities, the leaching temperature is required to be raised to 150-200 ℃, the energy consumption is up to 500-800 kWh/ton, and excessive damage to quartz crystal lattices is easy to cause. The single TiO 2 photocatalyst has low quantum efficiency under visible light and can not effectively decompose alkali metal complex. The supercritical fluid technology has high cost, the supercritical CO 2 extraction needs to maintain high pressure of more than 20MPa, the equipment investment is large, and the large-scale application is difficult. Disclosure of Invention (One) solving the technical problems Aiming at the defects of the prior art, the invention provides a high-purity quartz sand alkali metal targeted depth removal method. (II) technical scheme The high-purity quartz sand alkali metal targeted deep removal method comprises the following steps: S1, surface nano-structured pretreatment Mixing quartz sand with quartz silicon carbide abrasive, dry grinding in a planetary ball mill to form a micro-nano structure with surface roughness Ra=0.2-0.5 mu m, then immersing into a mixed solution containing ammonium fluoborate (NH 4BF4), nano titanium dioxide and Graphene Quantum Dots (GQDs), and processing under an ultrasonic field to generate etching pits with uniform depth on the quartz surface, wherein the GQDs are adsorbed on the quartz surface through pi-pi accumulation, and the reaction formula is as follows: ; s2, double complexing agent co-leaching Preparing a composite complexing solution containing hydroxyethylidene diphosphonic acid (HEDP), ethylenediamine tetramethylene phosphonic acid (EDTMPA), beta-cyclodextrin and crown ether-18-crown-6, adding pretreated quartz sand, and stirring in a microwave field to form a triple complexing system; s3, photocatalysis-electrochemistry combined desorption Transferring the leaching solution to a photoelectric desorption reactor, taking quartz sand as a cathode, taking a platinum sheet as an anode, adding potassium persulfate (K 2S2O8) and iron-cobalt bimetallic MOF (FeCo-MOF-74), and reacting under the synergistic effect of ultraviolet light and a direct current electric field; s4, super-gravity reinforced washing Three-stage countercurrent washing is carried out by adopting a super-gravity rotating bed, deionized water is used for washing with the liquid-solid ratio of 10:1-15:1, and the single residence time is 10-30 seconds; S5, plasma assisted lattice repair And (3) placing the washed quartz sand into a radio frequency plasma reactor, treating for 10-30 minutes under the vacuum