Method for preparing high-purity quartz sand by ultrasonic-assisted acid washing

Abstract

The application discloses a method for preparing high-purity quartz sand by ultrasonic-assisted acid pickling, and belongs to the technical field of mineral processing, and comprises the following steps: (1) quartz ore pretreatment, (2) crude quartz sand, (3) magnetic separation, (4) reverse flotation, (5) ultrasonic-assisted acid pickling and (6) purification. On the basis of the existing acid pickling treatment process, the quartz sand is subjected to purification treatment by adopting an intermittent ultrasonic-assisted acid pickling process or a multistage ultrasonic-assisted acid pickling process, and the purity of the obtained product quartz sand can be higher than 99.9985%, the method can be used for removing associated minerals and iron-containing minerals in the quartz sand, and the steps are simple, efficient and good in purification effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mineral processing, and particularly relates to a method for preparing high-purity quartz sand by ultrasonic-assisted pickling. BACKGROUND

[0002] Quartz sand is an important industrial raw material, has good physical and chemical properties, and is widely used in the fields of semiconductor chips, quartz crucibles, optical power, building materials, optical fibers, photovoltaics and the like. High-purity quartz sand, especially high-purity quartz sand with SiO2 content ≥ 99.99%, is mainly obtained by natural crystal processing, quartz mineral purification and impurity removal, or chemical preparation and synthesis method. Among them, the factors such as resource reserves, high processing cost and low production efficiency limit the large-scale industrial application of natural crystal processing and chemical preparation and synthesis, so at present, high-purity quartz sand is mainly produced in large quantities by quartz mineral purification and impurity removal.

[0003] Quartz minerals usually have impurity minerals associated with the surface, and common impurity minerals include mica, feldspar, hematite and clay minerals. Since the associated minerals are distributed on the surface of the quartz crystal, compared with lattice impurities or inclusion impurities, they are more easily separated out by traditional beneficiation methods.

[0004] The chemical properties of quartz are very stable, and it is almost insoluble in any acid except hydrofluoric acid. Therefore, acid washing can be used to effectively reduce impurity elements in quartz. Acid washing is divided into single acid method and mixed acid method. Many studies have found that mixed acid can produce a synergistic effect during the reaction process, and has good impurity removal effect, so strong acids such as hydrochloric acid, sulfuric acid, nitric acid, and oxalic acid are often used as leaching agents to react with impurity metal ions in quartz and dissolve them. K. Y. Lee et al. used hydrochloric acid and hydrofluoric acid mixed acid to wash, and the removal rate of Al and K elements was more than 80%, and the leaching solution could remove about 65% of the main and secondary impurities (“Acid leaching purification and neutron activation analysis of high purity silicas”, K. Y. Lee, Y. Y. Yoon, S. B. Jeong, Y. B. Cae, K. S. Ko. J Radioanal Nucl Chem (2009) 282:629-633). After pretreatment with potassium hydroxide, Hui Shao et al. used hydrochloric acid, nitric acid, and hydrofluoric acid mixed acid to wash quartz sand, and the content of impurity elements was reduced from 73.63 μg / g to 38.85 μg / g, the removal rate of iron (65.84%), potassium (50.26%), sodium (55.96%), lithium (20%), and aluminum (17.12%), and the purity of SiO2 could reach 99.994% (“Prepare and Mechanism of High Purity Quartz by Alkali Corrosion and Acid Leaching Process Using Vein Quartz”, Hui Shao, Fangfang Zang, Mengjiao Ji, Mingming Yu. Silicon (2022) 14:12475-12483).

[0005] The Chinese patent document with publication number CN106892430A discloses a preparation method of ultra-pure quartz sand. In the process of the invention, the calcined quartz sand is rapidly put into a stirring cylinder containing an acid solution at high temperature for acid quenching treatment, and then acid washing is performed using an acid solution (one or several of hydrofluoric acid, nitric acid, hydrochloric acid, and sulfuric acid) to achieve further purification of the quartz sand. The Chinese patent document with publication number CN114392836A discloses a processing technology for high-purity quartz sand. In the acid leaching process of the invention, a preliminary solution of HNO3 with a concentration of 2.3-2.5 mol / L is first prepared, the temperature of the preliminary solution is controlled at 26-32℃, and the sandstone raw material is subjected to primary acid washing, followed by standing for 15 min. Then, a preliminary solution of H2SO4 with a concentration of 1.6-1.8 mol / L is prepared for secondary acid washing treatment. Finally, an HCl solution with a concentration of 0.4-0.5 mol / L is prepared, and an H2C2O4 solution with a concentration of 2-10% is also prepared. The two solutions are mixed, and the sandstone is fully soaked for 5 min, and then is allowed to stand for 30 min.

[0006] Purifying quartz sand by a mixed acid washing process can reduce the content of mineral impurity elements. With the development of science and technology, the purity requirements for quartz sand are becoming higher and higher. It is of great significance to improve and modify the existing purification technology to further improve the purity of quartz sand. SUMMARY

[0007] The present application provides a method for preparing high-purity quartz sand by ultrasonic-assisted acid washing. The method is simple and efficient, has good purification effect, can specifically remove impurities such as iron-containing minerals in quartz sand, and the purity of the obtained product quartz sand can exceed 99.9985%, with less residual impurity elements.

[0008] The specific technical solutions adopted are as follows:

[0009] A method for preparing high-purity quartz sand by ultrasonic-assisted acid washing, comprising the following steps:

[0010] (1) Quartz ore pretreatment: heat the quartz ore to 900-1300℃ and keep it for 1-4h, and then naturally cool it to room temperature;

[0011] (2) Coarse quartz sand: crush and sieve the quartz ore treated in step (1) to obtain coarse quartz sand;

[0012] (3) Magnetic separation: remove the magnetic substances contained in the coarse quartz sand;

[0013] (4) Reverse flotation: add water to the quartz sand treated in step (3) to form a slurry, add a pH adjuster, a collector, and a foaming agent to the slurry, and perform reverse flotation process;

[0014] (5) ultrasonic-assisted acid washing: maintaining normal pressure, temperature 50-85℃, ultrasonic oscillation frequency 35-80kHz, carrying out intermittent ultrasonic-assisted acid washing process or multi-stage ultrasonic-assisted acid washing process on the lower layer slurry after reverse flotation;

[0015] (6) purification: washing the quartz sand treated in step (5), and drying at 1000-1400℃ for 1-4h to obtain high-purity quartz sand.

[0016] After calcination and crushing of the quartz ore, the crystal boundary has micro-cracks and residual stress. After applying ultrasonic waves in the subsequent process, the diffusion speed and reaction rate of the acid solution increase, and the vibration of the ultrasonic waves also produces micro-bubbles and water bubbles. These bubbles and water bubbles continuously expand and break in the vibration, forming a local high-temperature and high-pressure environment, increasing the corrosion ability of the acid solution, and making the micro-cracks grow to expose more impurity interfaces. More importantly, the intermittent ultrasonic-assisted acid washing process can avoid the problem of local over-corrosion of quartz sand, ensure uniformity, help improve acid washing efficiency, and the multi-stage ultrasonic-assisted acid washing process can avoid the formation of standing waves between ultrasonic waves and reflected ultrasonic waves, reduce the phenomenon of local acid washing unevenness, and help further improve the purification effect.

[0017] Preferably, in step (1), the SiO2 content in the quartz ore is not less than 95%.

[0018] Preferably, in step (2), the 50-200 mesh crude quartz sand is obtained after screening.

[0019] Preferably, in step (3), at least one magnetic separation is carried out at a field strength of 20000-22000GS.

[0020] Preferably, in step (4), a single-stage reverse flotation process is used, and the pH regulator used in reverse flotation is at least one of potassium hydroxide, sodium hydroxide, sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid or oxalic acid; the collecting agent is at least one of dodecylamine, rosin amine or oleic acid; and the foaming agent is at least one of No. 2 oil, eucalyptus oil or camphor oil.

[0021] Preferably, in step (5), a mixed acid solution including a first component and a second component is used in the ultrasonic-assisted acid washing process, the first component is at least one of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid and oxalic acid, and the second component is hydrofluoric acid.

[0022] Further preferably, in step (5), the mass concentration of the first component in the mixed acid solution is 10-40wt%, and the mass concentration of the second component is 10-30wt%; the liquid-solid ratio of the mixed acid solution to the slurry is 0.5-2:1.

[0023] Further preferably, in step (5), the duration of each ultrasonic-assisted acid pickling is 0.5-1 h, the pause time between two adjacent ultrasonic-assisted acid pickling is 0.5-1 h, and the total acid pickling time is 2-6 h.

[0024] Further preferably, in step (5), the two ultrasonic acid pickling with frequency f1 and frequency f2 are simultaneously applied during the ultrasonic-assisted acid pickling, 35 kHz≤f1≤50 kHz, 50 kHz≤f2≤80 kHz, and f2 and f1 are in a non-integer multiple relationship.

[0025] The simultaneous application of ultrasonic waves with lower and higher frequencies can deeply act on the micro-cracks on the surface of the quartz particles and the associated minerals on the surface, thereby bringing better impurity removal effect, especially for the removal of impurity elements such as Al and Fe.

[0026] Further preferably, in step (5), the two ultrasonic acid pickling with frequency f1 and frequency f2 are simultaneously applied for 2-6 h during the multi-stage ultrasonic-assisted acid pickling, 35 kHz≤f1≤50 kHz, 50 kHz≤f2≤80 kHz, and f2 and f1 are in a non-integer multiple relationship.

[0027] The purification and drying process in step (6) further reduces the water content in the quartz sand and reduces the residual alkali metals Na and K; preferably, the content of each impurity element in the high-purity quartz sand obtained in step (6) is less than 10 ppm, and the impurity elements are Al, B, Ba, Ca, Cr, Cu, Fe, Ge, K, Li, Mg, Mn, Na, Ni, P, Ti or Zr.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] (1) In view of the problem of excessive residual impurity elements in the acid leaching method in the prior art, the present application adopts an intermittent ultrasonic-assisted acid pickling process or a multi-stage ultrasonic-assisted acid pickling process to purify the quartz sand on the basis of the existing acid pickling process, and the purity of the obtained quartz sand can exceed 99.9985%; specifically, after the application of ultrasonic waves, the reaction ability of the acid solution to the impurities in the quartz sand is further improved due to the increase in the diffusion speed and reaction rate of the acid solution; the surface of the quartz sand produces many micro-cracks under the action of ultrasonic erosion, which helps to expose the impurity minerals contained in the quartz sand particles; the intermittent ultrasonic-assisted acid pickling process or the multi-stage ultrasonic-assisted acid pickling process can make the acid pickling more sufficient and uniform, and the processes such as magnetic separation and reverse flotation reduce the content of impurity elements before the acid pickling step, thereby reducing the loss of acid solution and improving the efficiency of acid pickling.

[0030] (2) The method for preparing high-purity quartz sand through ultrasonic-assisted pickling has simple and efficient steps, high impurity dissolution efficiency, good impurity removal effect, good removal effect on associated minerals and iron-containing mineral impurities in the quartz sand, and high purity of the obtained product quartz sand. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are described clearly and completely. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0032] The present application is further described below in combination with specific embodiments.

[0033] Embodiment 1

[0034] (1) Quartz ore pretreatment: under air atmosphere, the quartz ore (SiO2 content is 95%) is heated to 1100℃ and kept for 2h, and then naturally cooled to room temperature after heating;

[0035] (2) Rough quartz sand: the quartz ore treated in step (1) is mechanically broken and the obvious impurities and foreign matters such as feldspar and mica are removed, and the rough quartz sand with a particle size of 50-200 is obtained through screening, and then the rough quartz sand is washed with deionized water, filtered under reduced pressure and dried to obtain the rough quartz sand;

[0036] (3) Magnetic separation: the magnetic separation is carried out twice under a field strength of 22000GS;

[0037] (4) Reverse flotation: the quartz sand obtained in step (3) is added with water to prepare a slurry with a mass concentration of 40%, and then the slurry is added into a flotation machine for reverse flotation, a pH regulator composed of oxalic acid and sodium hydroxide solution is added to adjust the pH value to 2.0-3.0, a collector composed of dodecylamine, pine oil amine and oleic acid is added, the addition amount of the collector is 650g / t, stirring is carried out, a frother composed of No.2 oil and camphor oil is added, the addition amount of the frother is 80g / t, stirring and froth scraping are carried out, and the reverse flotation process is completed;

[0038] (5) Ultrasonic-assisted acid washing: The lower layer slurry after reverse flotation is put into an ultrasonic acid washing device, and a mixed acid solution is added (the liquid-solid ratio of the mixed acid to the slurry is 1:1). The mixed acid solution includes hydrochloric acid, sulfuric acid and hydrofluoric acid. The mass concentration of hydrochloric acid is 12wt%, the mass concentration of sulfuric acid is 25wt%, and the mass concentration of hydrofluoric acid is 20wt%. The pressure is maintained at 80℃ and the temperature is 80℃. The acid is first washed for 1 hour under ultrasonic vibration at 35kHz. After the ultrasonic wave is turned off, the acid is washed again for 1 hour (that is, the ultrasonic pause time between two adjacent ultrasonic-assisted acid washings is 1 hour). This is repeated three times, and the total acid washing time is 6 hours. After the acid washing is completed, the acid solution is separated by filtration.

[0039] (6) Purification: Wash the quartz sand treated in step (5) with deionized water, purify and dry at 1350℃ for 2 hours to obtain high-purity quartz sand.

[0040] Example 2

[0041] (1) Pretreatment of raw quartz ore: Under air atmosphere, the raw quartz ore (SiO2 content of 95%) is heated to 1100℃ and kept at the temperature for 2 hours, and then naturally cooled to room temperature after heating;

[0042] (2) Coarse quartz sand: The quartz ore processed in step (1) is mechanically crushed and obvious impurities and foreign matter such as feldspar and mica are removed. The quartz sand is screened to obtain 50-200 mesh coarse quartz sand. It is washed with deionized water, filtered under reduced pressure and dried to obtain coarse quartz sand.

[0043] (3) Magnetic separation: Two magnetic separations are performed under an electric field strength of 22000GS;

[0044] (4) Reverse flotation: The quartz sand obtained by magnetic separation in step (3) is mixed with water to form a slurry with a mass concentration of 40%, and added to the flotation machine for reverse flotation. A pH adjuster composed of oxalic acid and sodium hydroxide solution is added to adjust the pH value to 2.0-3.0. A collector composed of dodecylamine, rosin amine and oleic acid is added at a rate of 650 g / t. The mixture is stirred, and then a frother composed of No. 2 oil and camphor oil is added at a rate of 80 g / t. The mixture is stirred and the bubbles are scraped off to complete the reverse flotation process.

[0045] (5) Ultrasonic-assisted acid washing: The lower layer slurry after reverse flotation is fed into the ultrasonic acid washing equipment, and a mixed acid solution is added (the liquid-solid ratio of the mixed acid to the slurry is 1:1). The mixed acid solution includes hydrochloric acid, sulfuric acid and hydrofluoric acid. The mass concentration of hydrochloric acid is 12wt%, the mass concentration of sulfuric acid is 25wt%, and the mass concentration of hydrofluoric acid is 20wt%. The pressure is maintained at 80℃, and a multi-stage ultrasonic-assisted acid washing process is adopted. At the same time, ultrasonic waves at a frequency of 35kHz and 80kHz are continuously applied. The total acid washing time is 6h. After the acid washing is completed, the acid solution is separated by filtration.

[0046] (6) Purification: the quartz sand treated in step (5) is washed with deionized water, and purified at 1350℃ for 2h to obtain high-purity quartz sand.

[0047] Example 3

[0048] (1) Pretreatment of quartz ore: the quartz ore (SiO2 content of 95%) is heated to 1100℃ for 2h under air atmosphere, and then naturally cooled to room temperature;

[0049] (2) Coarse quartz sand: the quartz ore treated in step (1) is mechanically crushed and the obvious impurities and foreign matters such as feldspar and mica are removed, and then sieved to obtain coarse quartz sand with particle size of 50-200 mesh, which is washed with deionized water, filtered under reduced pressure and dried to obtain coarse quartz sand;

[0050] (3) Magnetic separation: the quartz sand obtained in step (3) is subjected to two times of magnetic separation under a field strength of 22000GS;

[0051] (4) Reverse flotation: the quartz sand obtained in step (3) is added with water to prepare a slurry with a mass concentration of 40%, and then added into a flotation machine for reverse flotation, a pH regulator composed of oxalic acid and sodium hydroxide solution is added to adjust the pH value to 2.0-3.0, a collector composed of dodecylamine, abietamine and oleic acid is added, the addition amount of the collector is 650g / t, stirring is performed, a frother composed of No.2 oil and camphor oil is added, the addition amount of the frother is 80g / t, stirring and scraping are performed, and the reverse flotation process is completed;

[0052] (5) Ultrasonic-assisted acid pickling: the lower slurry after reverse flotation is put into an ultrasonic acid pickling device, a mixed acid solution (the liquid-solid ratio of the mixed acid to the slurry is 1:1) is added, the mixed acid solution includes hydrochloric acid, sulfuric acid and hydrofluoric acid, the mass concentration of the hydrochloric acid is 12wt%, the mass concentration of the sulfuric acid is 25wt%, and the mass concentration of the hydrofluoric acid is 20wt%, the pressure is kept constant, the temperature is 80℃, and 35kHz frequency ultrasonic waves and 80kHz ultrasonic waves are continuously applied at the same time, the acid pickling is first performed for 1h under the oscillation of the two kinds of ultrasonic waves, the two kinds of ultrasonic waves are turned off, and then the acid pickling is performed for 1h again (i.e. the ultrasonic pause time between the adjacent two ultrasonic-assisted acid pickling is 1h), the two kinds of ultrasonic waves are turned on again, and the above steps are repeated until the total acid pickling time reaches 6h; after the acid pickling is completed, the acid solution is separated by filtration;

[0053] (6) Purification: the quartz sand treated in step (5) is washed with deionized water, and purified at 1350℃ for 2h to obtain high-purity quartz sand.

[0054] Comparative Example 1

[0055] The difference between the present comparative example and Example 1 is that, in the ultrasonic-assisted acid pickling process in step (5), the intermittent operation is not adopted, and the acid pickling is performed for 3h under the continuous oscillation of 35kHz ultrasonic waves.

[0056] Comparative Example 2

[0057] The present comparative example differs from Example 1 only in that the ultrasonic-assisted acid washing process in step (5) is not operated intermittently, but is carried out for 6 h under ultrasonic oscillation at 35 kHz.

[0058] Comparative Example 3

[0059] The present comparative example differs from Example 1 only in that the ultrasonic-assisted acid washing process in step (5) is not operated intermittently, but is carried out for 6 h under ultrasonic oscillation at 80 kHz.

[0060] Sample analysis

[0061] The products quartz sand prepared in the examples and comparative examples were characterized for impurity content using an inductively coupled plasma optical emission spectrometer (ICP-OES), and the results are shown in Table 1.

[0062] Table 1 Impurity content (ppm) in product quartz sand in the comparative examples and examples

[0063] Item Al B Ba Ca Cr Cu Fe Ge K Comparative Example 1 35.88 0.17 0.06 1.77 0.03 0.06 3.43 0.61 0.13 Comparative Example 2 9.71 0.16 0.06 2.11 0.04 0.01 1.05 0.53 0.14 Comparative Example 3 8.54 0.17 0.05 2.34 0.04 0.03 0.76 0.55 0.13 Example 1 6.09 0.14 0.05 2.84 0.04 0.03 0.69 0.52 0.12 Example 2 5.60 0.15 0.06 2.01 0.04 0.01 0.63 0.56 0.12 Example 3 5.61 0.15 0.06 2.17 0.04 0.03 0.56 0.55 0.10 Item Li Mg Mn Na Ni P Ti Zr ∑ Comparative Example 1 0.34 0.11 0.04 0.69 0.02 0.47 2.52 0.12 46.45 Comparative Example 2 0.41 0.10 0.03 0.41 0.02 0.26 2.85 0.08 17.97 Comparative Example 3 0.30 0.15 0.03 0.47 0.03 0.25 2.68 0.08 16.60 Example 1 0.33 0.10 0.00 0.17 0.04 0.23 2.19 0.07 13.65 Example 2 0.36 0.06 0.05 0.15 0.02 0.21 2.49 0.14 12.66 Example 3 0.33 0.06 0.01 0.16 0.03 0.24 2.22 0.09 12.41

[0064] The above examples have been described in detail for the technical solutions of the present application, and it should be understood that the above examples are only specific embodiments of the present application and are not intended to limit the present application. Any modification, supplement or similar replacement within the principle range of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing high purity quartz sand by ultrasonic acid washing, characterized by, The method comprises the steps of: (1) quartz ore pretreatment: heating the quartz ore to 900-1300℃ for 1-4h, and cooling; (2) crude quartz sand: crushing and screening the quartz ore treated in step (1) to obtain crude quartz sand; (3) magnetic separation: removing the magnetic substances contained in the crude quartz sand; (4) reverse flotation: adding water to the quartz sand treated in step (3) to form a slurry, adding a pH regulator, a collector and a foaming agent to the slurry, and performing a reverse flotation process; (5) ultrasonic-assisted acid pickling: maintaining normal pressure, a temperature of 50-85℃, and an ultrasonic oscillation frequency of 35-80kHz, and performing an intermittent ultrasonic-assisted acid pickling process or a multi-stage ultrasonic-assisted acid pickling process on the lower layer slurry after the reverse flotation; (6) purification: washing the quartz sand treated in step (5), and purifying and drying at 1000-1400℃ for 1-4h to obtain high-purity quartz sand. In step (4), a single-stage reverse flotation process is adopted, the pH regulator used in the reverse flotation is at least one of potassium hydroxide, sodium hydroxide, sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid or oxalic acid; the collector is at least one of dodecylamine, abietamine or oleic acid; and the foaming agent is at least one of No. 2 oil, eucalyptus oil or camphor oil. In step (5), a mixed acid solution comprising a first component and a second component is used in the ultrasonic-assisted acid pickling process, the first component is at least one of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or oxalic acid, and the second component is hydrofluoric acid; in the mixed acid solution, the mass concentration of the first component is 10-40wt%, and the mass concentration of the second component is 10-30wt%. In step (5), in the intermittent ultrasonic-assisted acid pickling process, the duration of each ultrasonic-assisted acid pickling is 0.5-1h, the ultrasonic pause time between adjacent two ultrasonic-assisted acid picklings is 0.5-1h, and the total acid pickling time is 2-6h; two ultrasonic acid picklings with a frequency of f1 and a frequency of f2 are applied simultaneously during the ultrasonic-assisted acid pickling, 35kHz≤f1≤50kHz, 50kHz≤f2≤80kHz, and f2 and f1 are in a non-integer multiple relationship. In step (5), in the multi-stage ultrasonic-assisted acid pickling process, two ultrasonic acid picklings with a frequency of f1 and a frequency of f2 are applied simultaneously for 2-6h, 35kHz≤f1≤50kHz, 50kHz≤f2≤80kHz, and f2 and f1 are in a non-integer multiple relationship.

2. The method of producing high purity quartz sand by ultrasonic acid pickling according to claim 1, wherein In step (1), the SiO2 content in the quartz ore is not less than 95%.

3. The method of producing high purity quartz sand by ultrasonic acid pickling according to claim 1, characterized by, In step (2), the screening obtains the crude quartz sand with a size of 50-200 mesh.

4. The method of producing high purity quartz sand by ultrasonic acid pickling according to claim 1, wherein In step (3), the magnetic separation is performed at least once under a field strength of 20000-22000GS.

5. The method of producing high purity quartz sand by ultrasonic acid pickling according to claim 1, wherein In step (6), the content of each impurity element in the high-purity quartz sand is less than 10ppm, and the impurity elements are Al, B, Ba, Ca, Cr, Cu, Fe, Ge, K, Li, Mg, Mn, Na, Ni, P, Ti or Zr.