Purification method of high-purity quartz sand

Abstract

The invention discloses a method for purifying high-purity quartz sand, which belongs to the technical field of preparation of high-purity quartz sand, and comprises the following steps: (1) sequentially carrying out high-pressure water jet scrubbing, gradient screening classification and dielectric separation on sandstone type quartz ore raw ore with SiO2 content of 85-90% to remove feldspar to obtain quartz particles with feldspar content of less than or equal to 2%; (2) sequentially carrying out microwave field pretreatment, infrared light field crack propagation and pulse laser implosion stripping on the quartz particles obtained in the step (1), and regulating and controlling technological parameters of the three fields through linkage of a PLC (Programmable Logic Controller) system, so that the stripping rate of an impurity inclusion is greater than or equal to 92%; according to the invention, aiming at quartz particles with different particle sizes, a plurality of process parameters are automatically optimized and adjusted through the PLC system, accurate control and adaptive production are realized, and high-purity products can be stably produced from sandstone type quartz raw materials with different grades in different regions. And the inclusion is opened from inside to outside through a multi-field synergistic effect, and the completeness of the quartz particles is retained to the greatest extent by combining with an optimized fluoride-free acid leaching condition.

Description

Technical Field

[0001] This invention relates to the field of high-purity quartz sand preparation technology, specifically a method for purifying high-purity quartz sand. Background Technology

[0002] High-purity quartz sand is a key basic material for high-tech industries such as semiconductors, photovoltaics, fiber optic communications, and high-end optical devices. Its purity directly affects the performance and reliability of downstream products. Currently, the main raw materials for high-purity quartz sand are natural crystal and high-quality granite, but these resources are increasingly depleted, and mining costs are high, making it difficult to meet market demand. Therefore, shifting to sandstone-type quartz mines with abundant reserves and lower costs has become an industry trend.

[0003] However, sandstone-type quartz deposits are usually associated with large amounts of feldspar, clay minerals, and impurities such as Al, Fe, K, Na, and B existing in the form of inclusions. In particular, B can form boron-oxygen vacancy defects at high temperatures, severely affecting the performance of quartz glass. Traditional quartz sand purification methods mainly include physical beneficiation and chemical purification. Among these methods, conventional acid leaching has limited effectiveness in removing impurities from inclusions, especially for light metals such as B, K, and Na; it often uses highly corrosive reagents such as hydrofluoric acid (HF), making waste acid treatment difficult and prone to causing fluoride pollution; and high-temperature chlorination requires temperatures above 1200℃, resulting in high energy consumption and demanding equipment requirements. Consequently, waste acid and residue are not effectively recovered, leading to resource waste and secondary pollution.

[0004] Therefore, we propose a purification method for high-purity quartz sand to solve the problems mentioned above.

[0005] The information disclosed above in this background section is only for enhancing the understanding of the background section of this invention, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for purifying high-purity quartz sand, thereby solving one of the problems of incomplete impurity removal, high energy consumption, and low resource utilization rate in the current purification methods on the market, as mentioned in the background art.

[0007] To achieve the above objectives, a method for purifying high-purity quartz sand includes the following steps:

[0008] (1) The sandstone-type quartz ore with SiO2 content of 85%-90% is subjected to high-pressure water jet washing, gradient screening and classification and dielectric separation to remove feldspar, to obtain quartz particles with feldspar content ≤2%.

[0009] (2) The quartz particles obtained in step (1) are subjected to microwave field pretreatment, infrared light field crack propagation and pulsed laser implosion ablation in sequence. The process parameters of the three fields are controlled by the PLC system to make the ablation rate of impurity inclusions ≥92%.

[0010] (3) The quartz particles after breaking the packaging in step (2) are subjected to pre-complexation to remove Al and Ti, pressure swing chlorination to remove B, K and Na, and fluorine-free acid leaching to remove impurities, so that Al≤5ppm, Ti≤2ppm and B≤0.1ppm.

[0011] (4) The waste liquid generated from the fluorine-free acid leaching in step (3) is subjected to acid recovery, heavy metal adsorption and evaporation crystallization in sequence.

[0012] Furthermore, in step (1), the pressure of the high-pressure water jet is 80-100MPa, and ultrasonic waves of 40-50kHz are simultaneously introduced for assisted scrubbing, with a processing time of 15-20min; the gradient sieving uses three-level screens of 50μm, 100μm, and 200μm; the electric field strength of the dielectric separation is 5-8kV / cm, and the medium is dry air.

[0013] Furthermore, in step (2), the frequency of the microwave field is 2.45 GHz, the power density is 500-800 W / kg, and the processing time is 5-8 min; the wavelength of the infrared light field is 2.5-5 μm, the focusing diameter is 0.4-0.6 mm, and the processing time is 3-5 min; the wavelength of the pulsed laser is 1064 nm, the energy density is 5-8 J / cm², and the frequency is 10-20 Hz.

[0014] Furthermore, the specific steps for pre-complexing and removing Al and Ti in step (3) are as follows:

[0015] Quartz particles were added to a pre-complexing solution at a solid-liquid ratio of 1:5. The pre-complexing solution was composed of 0.2-0.3 mol / L acetylacetone and 0.4-0.6 mol / L citric acid, with the pH value adjusted to 3.0-4.0. The mixture was stirred and reacted at 50-60℃ for 2-2.5 hours.

[0016] Furthermore, the specific steps for removing B, K, and Na by pressure swing chlorination in step (3) are as follows:

[0017] The pre-complexed quartz particles are preheated in air at 900-950℃ for 30-40 minutes; then the pressure inside the furnace is reduced to 10℃. -2 -10 -1 Pa, a mixture of HCl and Cl2 in a volume ratio of 3:1-4:1 is introduced and reacted at 900℃ for 2-2.5h; after restoring to normal pressure, Ar gas is introduced at a flow rate of 1.5-2.5L / min to purge for 30min.

[0018] Furthermore, the specific steps for removing impurities through fluoride-free acid leaching in step (3) are as follows:

[0019] Chlorinated quartz particles were added to a compound acid at a solid-liquid ratio of 1:8. The compound acid was composed of 2-2.5 mol / L H2SO4 and 0.4-0.6 mol / L H3PO4, with 0.1%-0.2% hexadecyltrimethylammonium bromide added. The mixture was stirred and leached at 80-85℃ for 2-2.5 hours, resulting in a quartz dissolution rate of <1%.

[0020] Furthermore, in step (4), the acid recovery uses a DF-120 anion exchange membrane for diffusion dialysis, with an H2SO4 recovery rate ≥95% and an H3PO4 recovery rate ≥92%; the heavy metal adsorption uses a D401 chelating resin for Fe... 3+ Al 3+ The adsorption capacity is ≥120mg / g; the evaporation and crystallization are carried out under a vacuum of -0.08 to -0.09MPa to obtain industrial-grade Al2(SO4)3 and FePO4.

[0021] Furthermore, in step (2), when the PLC system controls the three process parameters in a coordinated manner, for quartz particles with a particle size of 50-100μm, the microwave power density is set to 500-650W / kg, the infrared wavelength is 2.5-3.5μm, and the pulsed laser frequency is 15-20Hz; for quartz particles with a particle size of 100-200μm, the microwave power density is set to 650-800W / kg, the infrared wavelength is 3.5-5μm, and the pulsed laser frequency is 10-15Hz.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention utilizes a three-field coordinated, PLC-linked de-packaging technology to achieve efficient and controllable removal of inclusions within quartz particles, with a removal rate exceeding 92%. Combined with a targeted impurity removal process involving pre-complexation, pressure swing chlorination, and fluorine-free acid leaching, it effectively removes, especially, difficult-to-remove, light metal impurities such as B, K, and Na.

[0024] This invention employs a compound acid system of H2SO4 and H3PO4 in the acid leaching step, avoiding the use of traditional hydrofluoric acid (HF), eliminating the problems of fluoride pollution and fluoride waste gas treatment, and making the production environment safer. Waste acid is efficiently recovered through diffusion dialysis technology, and the recovered acid solution can be recycled back into the production process, significantly reducing the consumption of fresh acid and the wastewater treatment load. Valuable metal ions in the waste liquid are adsorbed and enriched, and then converted into industrial-grade Al2(SO4)3, FePO4, and other byproducts through evaporation and crystallization, achieving high-value utilization of waste and essentially achieving near-zero emissions of waste gas, wastewater, and solid waste. Furthermore, the pressure swing chlorination reaction temperature used is much lower than that of traditional high-temperature chlorination processes, reducing energy consumption and equipment requirements. The improved impurity stripping and removal efficiency shortens the processing time, and the recycling of acid solution reduces raw material consumption.

[0025] This invention targets quartz particles of different sizes, automatically optimizing and adjusting various process parameters through a PLC system to achieve accurate control and adaptive production. It can stably produce high-purity products from sandstone-type quartz raw materials of different regions and grades, demonstrating strong versatility. Furthermore, it opens inclusions from the inside out through a multi-field synergistic effect, rather than through strong external mechanical crushing. Combined with optimized fluoride-free acid leaching conditions, it maximizes the preservation of quartz particle integrity, resulting in a low particle breakage rate and improved particle strength and yield of the final product.

[0026] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0027] Figure 1 This is a flowchart of step one in the purification method of high-purity quartz sand of the present invention;

[0028] Figure 2 This is a flowchart of step two in the purification method of high-purity quartz sand of the present invention;

[0029] Figure 3 This is a flowchart of step three in the purification method of high-purity quartz sand of the present invention;

[0030] Figure 4 This is a flowchart of step four in the purification method of high-purity quartz sand of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the drawings are schematic and not illustrated to scale. For clarity and convenience, the relative sizes and proportions of the parts shown in the drawings have been exaggerated or reduced in size. Any size is only illustrative and not limiting.

[0032] Example 1: Using Xinjiang sandstone-type quartz ore with 85% SiO2 content as raw material

[0033] The raw ore contains 85.2% SiO2, 6.8% Al2O3, 1.5% Fe2O3, 3.2% K2O+Na2O, 12ppm B, 8% montmorillonite clay, and particle size ≤5mm.

[0034] The purification method for high-purity quartz sand includes the following steps:

[0035] (1) The sandstone-type quartz ore with SiO2 content of 85%-90% is subjected to high-pressure water jet washing, gradient screening and classification and dielectric separation to remove feldspar, to obtain quartz particles with feldspar content ≤2%.

[0036] Specifically, the high-pressure water jet scrubbing equipment is the XSC-100 high-pressure scrubbing machine with a power of 75kW; the water jet pressure is 100MPa, the jet angle is 30°, and 50kHz ultrasonic waves are simultaneously introduced with a power of 2.5kW and a processing time of 20min; resulting in a clay removal rate of 98.5% and a particle surface cleanliness of 95%.

[0037] The equipment used for gradient screening and grading is a 3YK1860 three-layer vibrating screen with a screen material of 316L stainless steel. The screen mesh is 200μm, the middle layer is 100μm, and the bottom layer is 50μm. Three-stage particles are obtained, of which 42% are 50-100μm, 38% are 100-200μm, and 20% are <50μm. The grading efficiency is 96.3%.

[0038] The equipment used for dielectric separation to remove feldspar was a JDF-5 dielectric separator with an electrode spacing of 50mm. The electric field strength was 8kV / cm, the material flow rate was 0.5m / s, the ambient temperature was 25℃, and the medium was dry air with a humidity of ≤30%. This reduced the content of 50-100μm feldspar particles from 15.2% to 1.9% and the content of 100-200μm feldspar particles from 14.8% to 1.7%.

[0039] (2) The quartz particles obtained in step (1) are sequentially subjected to microwave field pretreatment, infrared light field crack propagation and pulsed laser implosion ablation. The process parameters of the three fields are controlled by the PLC system to make the impurity inclusion ablation rate ≥92%. The process is mainly for 50-100μm and 100-200μm particles.

[0040] The equipment used for microwave field pretreatment was a WBZ-6 type microwave reactor; for 50-100μm particles, the power density was 650W / kg and the treatment time was 6min; for 100-200μm particles, the power density was 800W / kg and the treatment time was 8min; finally, initial cracks were generated on the particle surface, and the temperature difference between the inclusions and the matrix reached 60℃.

[0041] The equipment used for infrared crack propagation was an HWG-10 infrared heating furnace; for 50-100μm particles, the infrared wavelength was 3.5μm, the focusing diameter was 0.5mm, and the processing time was 4min; for 100-200μm particles, the infrared wavelength was 5μm, the focusing diameter was 0.6mm, and the processing time was 5min; this resulted in crack propagation to 250-300nm and the internal pressure of the inclusions rising to 1.2MPa.

[0042] The equipment used for pulsed laser implosion ablation was an ML-20 pulsed laser with a wavelength of 1064 nm; the energy density of 50-100 μm particles was 6.5 J / cm³. 2 Frequency 15Hz, scanning speed 20mm / s; energy density of 100-200μm particles 8J / cm³ 2 The frequency was 10 Hz and the scanning speed was 15 mm / s, resulting in an inclusion removal rate of 92.8%. The residual amount of inclusions on the particle surface was observed to be ≤7.2% by scanning electron microscopy (SEM).

[0043] The PLC linkage control adopts an S7-1200 PLC system, which collects particle size signals in real time, monitors them online with a laser particle size analyzer, and automatically matches microwave and infrared laser parameters with a parameter fluctuation range of ≤±3%.

[0044] (3) The quartz particles after breaking the packaging in step (2) are subjected to pre-complexation to remove Al and Ti, pressure swing chlorination to remove B, K and Na, and fluorine-free acid leaching to remove impurities, so that Al≤5ppm, Ti≤2ppm and B≤0.1ppm.

[0045] The equipment used for pre-complexation Al / Ti removal was a 500L enamel-lined reactor equipped with an internal stirrer at a speed of 150 r / min. The pre-complexation solution was prepared as 0.3 mol / L acetylacetone (analytical grade) + 0.6 mol / L citric acid (analytical grade), with the pH adjusted to 4.0 using 1 mol / L HCl. Quartz particles were added at a solid-liquid ratio of 1:5, and the mixture was heated in a 55℃ water bath with stirring for 2.5 h. Finally, the Al removal rate was 75.3%, and the Ti removal rate was 72.1%.

[0046] The equipment used for pressure swing chlorination to remove B / K / Na is a GSL-1700X type tube furnace with an inner diameter of 80mm in the quartz tube;

[0047] Preheating at atmospheric pressure in an air atmosphere, heating to 950℃ at a rate of 5℃ / min, and holding at that temperature for 40min; then reducing the furnace pressure to 10℃ using a vacuum pump. -1 Pa, a HCl / Cl2 mixed gas with a volume ratio of 4:1 was introduced at a flow rate of 0.8 L / min, and the reaction was carried out at 900 °C for 2.5 h; the chlorination gas was turned off, and Ar gas was introduced at a flow rate of 2.5 L / min for purging for 30 min; finally, the removal rate of B was 82.5%, and the removal rate of K2O+Na2O was 96%.

[0048] The equipment used for deep purification by fluorine-free acid leaching was a 1000 LPP material reactor. The compound acid was prepared as 2.5 mol / L H2SO4 (analytical grade) + 0.6 mol / L H3PO4 (analytical grade), with 0.2% hexadecyltrimethylammonium bromide (chemically pure) added. The chlorinated particles were added at a solid-liquid ratio of 1:8, heated to 85°C, stirred at 120 r / min, and leached for 2.5 h. Finally, Al was reduced to 4.8 ppm, Ti to 1.9 ppm, and the quartz dissolution rate was 0.9%.

[0049] (4) The waste liquid generated from the fluorine-free acid leaching in step (3) is subjected to acid recovery, heavy metal adsorption and evaporation crystallization in sequence.

[0050] The equipment used for acid recovery is a DS-10 diffusion dialysis unit with a DF-120 anion exchange membrane and an effective area of ​​0.5 m². 2 The waste liquid with an acid concentration of approximately 1.8 mol / L H2SO4 + 0.4 mol / L H3SO4 was introduced into the membrane module at a flow rate of 0.8 L / h, and the recovery liquid flow rate was 0.6 L / h.

[0051] Ultimately, the recovery rate of H2SO4 was 95.6%, the recovery rate of H3PO4 was 92.8%, and the regenerated acid solution could be directly reused in step (3).

[0052] The equipment used for heavy metal adsorption is a Φ100×1000mm resin column, filled with D401 type chelating resin, with a packing volume of 5L; the diffusion dialysis permeate (containing Fe)3+ =250mg / L, Al 3+ =180mg / L) was passed through the column at a flow rate of 1.5BV / h; finally, the Fe in the effluent was... 3+ =0.09mg / L, Al 3+ =0.07mg / L, resin adsorption capacity 125mg / g.

[0053] The equipment used for evaporating and crystallizing the product is a triple-effect evaporator, with an evaporation area of ​​5m². 2 Vacuum degree -0.09MPa; resin regeneration waste liquid (containing Al2(SO4)3=8% and FePO4=5%) is evaporated and concentrated to a solid content of 30%, and then cooled and crystallized; finally, industrial-grade Al2(SO4)3 and FePO4 by-products are obtained.

[0054] Example 2: Using Henan sandstone-type quartz ore with a SiO2 content of 88% as raw material.

[0055] Raw material characteristics: raw ore SiO2=88.1%, Al2O3=4.5%, Fe2O3=0.9%, K2O+Na2O=2.1%, B=8ppm, clay content 5%, particle size ≤5mm.

[0056] The purification method for high-purity quartz sand includes the following steps:

[0057] (1) The sandstone-type quartz ore with SiO2 content of 85%-90% is subjected to high-pressure water jet washing, gradient screening and classification and dielectric separation to remove feldspar, to obtain quartz particles with feldspar content ≤2%.

[0058] Specifically, the high-pressure water jet scrubbing pressure was 90 MPa, the ultrasonic treatment was 45 kHz, and the treatment time was 18 min, resulting in a clay removal rate of 98.2%. In the gradient sieving, the proportion of 50-100 μm particles was 45%, and the proportion of 100-200 μm particles was 40%, with a classification efficiency of 96.5%. In the dielectric separation, the electric field strength was 7 kV / cm, and the feldspar content decreased to 1.8% (50-100 μm) and 1.6% (100-200 μm).

[0059] (2) The quartz particles obtained in step (1) are subjected to microwave field pretreatment, infrared light field crack propagation and pulsed laser implosion ablation in sequence. The process parameters of the three fields are controlled by the PLC system to make the ablation rate of impurity inclusions ≥92%.

[0060] In microwave pretreatment, 50-100μm particles were treated with 600W / kg for 5 min; 100-200μm particles were treated with 700W / kg for 7 min. In infrared spreading, 50-100μm particles were treated with a 3μm wavelength for 3.5 min; 100-200μm particles were treated with a 4μm wavelength for 4.5 min. In laser ablation, 50-100μm particles were treated with 6J / cm². 2 18Hz; 7J / cm for 100-200μm particles. 2 12Hz; ultimately, the inclusion removal rate was 93.5%.

[0061] (3) The quartz particles after breaking the packaging in step (2) are subjected to pre-complexation to remove Al and Ti, pressure swing chlorination to remove B, K and Na, and fluorine-free acid leaching to remove impurities, so that Al≤5ppm, Ti≤2ppm and B≤0.1ppm.

[0062] In the pre-complexation process, 0.25 mol / L acetylacetone + 0.5 mol / L citric acid (pH=3.5) was reacted at 55℃ for 2.2 h, achieving an Al removal rate of 74.2%. In the pressure swing chlorination process, HCl / Cl2 = 3.5:1, with a negative pressure of 10... -2 Pa, reaction time 2.2h, B removal rate 83.1%; in fluorine-free acid leaching, 2.2mol / LH2SO4+0.5mol / LH3SO4+0.15%CTAB, leaching at 82℃ for 2.2h, Al=3.1ppm, Ti=1.4ppm.

[0063] (4) The waste liquid generated from the fluorine-free acid leaching in step (3) is subjected to acid recovery, heavy metal adsorption and evaporation crystallization in sequence.

[0064] Ultimately, the green circulating acid recovery rates were 95.2% for H2SO4 and 92.5% for H3PO4; the purity of the byproduct Al2(SO4)3 was 98.5%.

[0065] Example 3: Anhui sandstone-type quartz ore with a SiO2 content of 90% was used as raw material.

[0066] Raw material characteristics: raw ore SiO2=90.3%, Al2O3=3.2%, Fe2O3=0.6%, K2O+Na2O=1.5%, B=5ppm, clay content 3%, particle size ≤5mm.

[0067] (1) The sandstone-type quartz ore with SiO2 content of 85%-90% is subjected to high-pressure water jet washing, gradient screening and classification and dielectric separation to remove feldspar, to obtain quartz particles with feldspar content ≤2%.

[0068] High-pressure water jet scrubbing at 80 MPa and 40 kHz ultrasound for 15 min resulted in a clay removal rate of 98.0%. During gradient sieving, 50-100 μm particles accounted for 48%, and 100-200 μm particles accounted for 42%, with a classification efficiency of 97.0%. During dielectric separation, with an electric field strength of 5 kV / cm, the feldspar content decreased to 1.5% (50-100 μm) and 1.4% (100-200 μm).

[0069] (2) The quartz particles obtained in step (1) are subjected to microwave field pretreatment, infrared light field crack propagation and pulsed laser implosion ablation in sequence. The process parameters of the three fields are controlled by the PLC system to make the ablation rate of impurity inclusions ≥92%.

[0070] For microwave pretreatment, 500 W / kg for 5 min was used for 50-100 μm particles, and 650 W / kg for 6 min was used for 100-200 μm particles. For infrared expansion, 2.5 μm wavelength was used for 50-100 μm particles, and 3.5 μm wavelength was used for 3 min; for 100-200 μm particles, 3.5 μm wavelength was used for 4 min. For laser ablation, 5 J / cm² was used for 50-100 μm particles. 2 20Hz; 6J / cm for 100-200μm particles. 2 15Hz; ultimately, the inclusion removal rate was 94.2%.

[0071] (3) The quartz particles after breaking the packaging in step (2) are subjected to pre-complexation to remove Al and Ti, pressure swing chlorination to remove B, K and Na, and fluorine-free acid leaching to remove impurities, so that Al≤5ppm, Ti≤2ppm and B≤0.1ppm.

[0072] During pre-complexation, 0.2 mol / L acetylacetone + 0.4 mol / L citric acid (pH=3.0) were reacted at 50℃ for 2 h, achieving an Al removal rate of 73.5%. During pressure swing chlorination, HCl / Cl2 = 3:1, and a negative pressure of 10... -2 Pa, reaction time 2h, B removal rate 84.0%; leaching with 2mol / L H2SO4 + 0.4mol / L H3SO4 + 0.1% CTAB at 80℃ for 2h, Al = 2.9ppm, Ti = 1.2ppm.

[0073] (4) The waste liquid generated from the fluorine-free acid leaching in step (3) is subjected to acid recovery, heavy metal adsorption and evaporation crystallization in sequence.

[0074] Ultimately, the acid recovery rates were 96.0% for H2SO4 and 93.0% for H3PO4; the purity of the byproduct FePO4 was 98.0%.

[0075] Comparative Example

[0076] (a) Using the traditional techniques of high-temperature calcination, magnetic separation, and hydrofluoric acid leaching as a comparative example, the experimental procedure was as follows:

[0077] Step 1: Raw material pretreatment

[0078] Jaw crusher: PEX150×250 jaw crusher is used to crush the raw ore to a particle size of ≤1mm. There is no high-pressure water jet scrubbing, only mechanical stripping of surface clay.

[0079] Single-stage screening: A 100μm stainless steel screen is used to retain only particles ≥100μm, and the screening recovery rate is recorded.

[0080] High gradient magnetic separation: SLon-100 high gradient magnetic separator with a magnetic field strength of 1.0T is used for wet separation to remove magnetic impurities Fe2O3 and to test the feldspar content after magnetic separation.

[0081] Step 2: High-temperature calcination to break the package

[0082] After magnetic separation, the particles were fed into an SX2-12-10 box-type resistance furnace and heated to 900℃ at 5℃ / min in an air atmosphere, and held for 2 hours. Then, they were quickly quenched in 80℃ hot water to generate cracks by thermal expansion and contraction. The peeling of the inclusions was observed by SEM and the peeling rate was calculated.

[0083] Step 3: Hydrofluoric acid leaching to remove impurities

[0084] Acid solution preparation: Mix 1 mol / L hydrofluoric acid (HF, analytical grade) and 0.5 mol / L hydrochloric acid (HCl, analytical grade) at a volume ratio of 1:1 to prepare the leachate;

[0085] Leaching operation: Add the calcined particles to a 500 LPP reactor at a solid-liquid ratio of 1:6, heat in a 60°C water bath, stir at 100 r / min, and leach for 4 hours.

[0086] Water washing and neutralization: After leaching, wash repeatedly with deionized water until pH=6-7 to remove residual acid. After collecting the wastewater, test the fluoride ion concentration.

[0087] Drying test: The washed particles were dried in an oven at 110℃ for 4 hours, and the purity of SiO2 and the content of impurities B, Al and Ti were tested.

[0088] Step 4: Wastewater Treatment

[0089] The leachate was mixed with lime slurry (Ca(OH)2) to adjust the pH to 8-9, which produced CaF2 precipitate. The supernatant after precipitation was passed through a D401 chelating resin column to adsorb heavy metals. The fluoride ion concentration in the treated wastewater was measured and the wastewater treatment cost was recorded.

[0090] (ii) The experimental data of Example 2 were used as the comparative example, and the experimental process was the same as that of Example 2.

[0091] The experimental results are shown in Tables 1-3:

[0092] Index Comparative Example (Traditional Technology) Invention (Example Two) Difference Rate (Invention Relative to Comparative Example) Raw Material Screening Recovery Rate (%) 70.2 (<100 μm waste) 92.5 (Full Particle Size Utilization) +31.8% Feldspar Content After Pretreatment (%) 7.2 1.7 -76.4% Fe2O3 content (ppm) after magnetic separation 180 85 -52.8% Inclusion Peeling Rate (%) 64.8 (SEM Statistics) 93.5 (SEM Statistics) +44.3% Particle Breakage Rate (%) 15.3 (Laser Particle Size Analyzer) 2.8 (Laser Particle Size Analyzer) -81.7%

[0093] Table 1 Comparison of Raw Material Processing and Packaging Breaking Effects

[0094] Product Index Comparative Example (Traditional Technology) Invention (Example Two) Difference (Invention Advantage) SiO2purity (%) 99.985 (4N8 Grade) 99.9993 (5N2 Grade) 0.0143 Percentage Points Increased B Content (ppm) 0.5 0.07 86.0% Reduced Al Content (ppm) 12.0 3.1 74.2% Reduced Ti Content (ppm) 5.0 1.4 72.0% Reduced Hydroxyl Content (ppm) 12.5 1.8 85.6% Reduced

[0095] Table 2 Comparison of Core Product Indicators

[0096] Index Comparative Example (Traditional Technology) Invention (Example Two) Difference Rate (Invention Relative to Comparative Example) Core Decontamination Reagent 1 mol / L HF (Highly Toxic) Fluorine-free Compound Acid (Safe) Eliminate the Risk of Highly Toxic Wastewater Fluoride Concentration (mg / L) 528 (Before Treatment) 4.2 (Before Treatment) -99.2% Wastewater Treatment Cost (Yuan / Ton of Sand) 121.5 34.8 -71.3% Acid Liquid Recovery Rate (%) 0 (Direct Discharge) 95.2 (H2SO4) +95.2% Raw Material Cost (Yuan / Ton) 2850 (Only ≥100 μm) 980 (Full Particle Size Utilization) -65.6% Comprehensive Ton of Sand Cost (Ten Thousand Yuan) 8.2 3.3 -60.9%

[0097] Table 3 Comparison of Environmental Protection and Economic Efficiency

[0098] Experimental results show that traditional techniques, lacking pretreatment procedures such as ultrasonic scrubbing and single-stage sieving, have a raw material recovery rate of only 70.2% and incomplete feldspar removal. This invention, through gradient sieving and dielectric separation, increases the recovery rate to 92.5% and reduces the feldspar content to 1.7%, making it suitable for low-grade sandstone deposits.

[0099] Traditional techniques are limited by low inclusion removal rates and poor HF leaching selectivity, achieving only 4N8-level purity with B impurities far exceeding semiconductor standards. By using three-field synergistic encapsulation breaking and targeted deimpurification, 5N2-level purity with B ≤ 0.07 ppm is achieved, meeting high-end requirements.

[0100] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for purifying high-purity quartz sand, characterized in that, Includes the following steps: (1) The sandstone-type quartz ore with SiO2 content of 85%-90% is subjected to high-pressure water jet washing, gradient screening and classification and dielectric separation to remove feldspar, so as to obtain quartz particles with feldspar content ≤2%. (2) The quartz particles obtained in step (1) are subjected to microwave field pretreatment, infrared light field crack propagation and pulsed laser implosion ablation in sequence. The process parameters of the three fields are controlled by the PLC system to make the ablation rate of impurity inclusions ≥92%. (3) The quartz particles after breaking the packaging in step (2) are subjected to pre-complexation to remove Al and Ti, pressure swing chlorination to remove B, K and Na, and fluorine-free acid leaching to remove impurities, so that Al≤5ppm, Ti≤2ppm and B≤0.1ppm. (4) The waste liquid generated from the fluorine-free acid leaching in step (3) is subjected to acid recovery, heavy metal adsorption and evaporation crystallization in sequence.

2. The purification method for high-purity quartz sand according to claim 1, characterized in that: In step (1), the pressure of the high-pressure water jet is 80-100MPa, and ultrasonic waves of 40-50kHz are simultaneously introduced for assisted scrubbing, with a processing time of 15-20min; the gradient sieving uses three-level screens of 50μm, 100μm, and 200μm; the electric field strength of the dielectric separation is 5-8kV / cm, and the medium is dry air.

3. The purification method for high-purity quartz sand according to claim 1, characterized in that: In step (2), the microwave field has a frequency of 2.45 GHz, a power density of 500-800 W / kg, and a processing time of 5-8 min; the infrared light field has a wavelength of 2.5-5 μm, a focusing diameter of 0.4-0.6 mm, and a processing time of 3-5 min; the pulsed laser has a wavelength of 1064 nm and an energy density of 5-8 J / cm². 2 The frequency is 10-20Hz.

4. The purification method for high-purity quartz sand according to claim 1, characterized in that: The specific steps for pre-complexing and removing Al and Ti in step (3) are as follows: Quartz particles were added to a pre-complexing solution at a solid-liquid ratio of 1:

5. The pre-complexing solution was composed of 0.2-0.3 mol / L acetylacetone and 0.4-0.6 mol / L citric acid, with the pH value adjusted to 3.0-4.

0. The mixture was stirred and reacted at 50-60℃ for 2-2.5 hours.

5. The purification method for high-purity quartz sand according to claim 1, characterized in that: The specific steps for removing B, K, and Na by pressure swing chlorination in step (3) are as follows: The pre-complexed quartz particles are preheated in air at 900-950℃ for 30-40 minutes; then the pressure inside the furnace is reduced to 10℃. -2 -10 -1 Pa, a mixture of HCl and Cl2 in a volume ratio of 3:1-4:1 is introduced and reacted at 900℃ for 2-2.5h; after restoring to normal pressure, Ar gas is introduced at a flow rate of 1.5-2.5L / min to purge for 30min.

6. The purification method for high-purity quartz sand according to claim 1, characterized in that: The specific steps for removing impurities through fluorine-free acid leaching in step (3) are as follows: Chlorinated quartz particles were added to a compound acid at a solid-liquid ratio of 1:

8. The compound acid was composed of 2-2.5 mol / L H2SO4 and 0.4-0.6 mol / L H3PO4, with 0.1%-0.2% hexadecyltrimethylammonium bromide added. The mixture was stirred and leached at 80-85℃ for 2-2.5 hours, resulting in a quartz dissolution rate of <1%.

7. The purification method for high-purity quartz sand according to claim 1, characterized in that: In step (4), the acid recovery uses a DF-120 anion exchange membrane for diffusion dialysis, with H2SO4 recovery rate ≥95% and H3PO4 recovery rate ≥92%; the heavy metal adsorption uses a D401 chelating resin for Fe... 3+ Al 3+ The adsorption capacity is ≥120mg / g; the evaporation and crystallization are carried out under a vacuum of -0.08 to -0.09MPa to obtain industrial-grade Al2(SO4)3 and FePO4.

8. The purification method for high-purity quartz sand according to claim 1, characterized in that: In step (2), when the PLC system controls the three process parameters in a coordinated manner, for quartz particles with a particle size of 50-100μm, the microwave power density is set to 500-650W / kg, the infrared wavelength is set to 2.5-3.5μm, and the pulsed laser frequency is set to 15-20Hz; for quartz particles with a particle size of 100-200μm, the microwave power density is set to 650-800W / kg, the infrared wavelength is set to 3.5-5μm, and the pulsed laser frequency is set to 10-15Hz.

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