Ultrasonic-assisted acid-saving method for refining quartz sand through multi-step pickling

Abstract

The invention belongs to the technical field of quartz sand pickling, and discloses an ultrasonic-assisted acid-saving method for refining quartz sand through multi-step pickling. According to the method, quartz sand is subjected to pre-acid leaching in an acid leaching solution and then subjected to intermittent ultrasonic-assisted acid pickling in an acid pickling solution, and acid-pickled quartz sand is obtained; and washing, drying and screening the pickled quartz sand to obtain a finished product. Pre-acid leaching is firstly carried out, industrial waste acid with low-concentration fluorine content is adopted, and a lattice system of quartz sand is opened through pre-acid leaching, so that hydrofluoric acid can enter the lattice system in the subsequent acid pickling process to dissolve impurities, the concentration of hydrofluoric acid used for acid pickling is reduced, and the amount of acid used for acid pickling is reduced. A complexing agent and organic acid are added in the pickling process, so that the impurity dissolution effect is improved; meanwhile, ultrasonic assistance is adopted, generation of surface microcracks is increased, pre-acid leaching is matched, the diffusion speed and the reaction speed are increased, the impurity removal rate is increased, the reaction time is shortened, and the acid liquor consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of quartz sand pickling, in particular to a method for refining quartz sand by multi-step pickling with ultrasonic assistance and acid saving. Background Art

[0002] Quartz sand is an important industrial mineral raw material, widely used in glass, casting, ceramics and refractory materials, metallurgy, construction, chemical industry, plastics, rubber, abrasives and other industries. The preparation of quartz sand usually uses quartzite as raw material. The surface of quartzite usually contains associated impurities, which can be removed by conventional beneficiation methods. However, lattice impurities and inclusion impurities cannot be removed by conventional beneficiation methods, and these impurities are the key to restricting the purity of quartz sand. At present, the commonly used method for quartz sand purification is pickling, which reduces and dissolves the film iron on the surface of quartz sand and the lattice iron inside, and then rinses with high-purity water. The acid used in this method is usually concentrated hydrochloric acid or high-concentration hydrofluoric acid. The chlorine-containing wastewater formed after pickling with hydrochloric acid is usually prohibited from being discharged according to the current environmental protection policy. Although high-concentration hydrofluoric acid can effectively remove iron impurities, hydrofluoric acid will also react with quartz sand components to form fluorosilicates, thereby corroding quartz sand.

[0003] On this basis, researchers have developed a variety of pickling methods to pickle and purify quartz sand. For example, patent 202410978862.5 discloses a fluorine-free and nitric acid-free leaching process for preparing high-purity quartz sand. After conventional processes such as crushing, magnetic separation, and flotation, the gas-liquid inclusions and isomorphous impurities inside the lattice are released by high temperature of 600 to 1300°C and microwave heating, and then the water-quenched quartz sand is pickled by adding a mixed acid of oxalic acid and hydrochloric acid in a molar ratio of 1:2 to 5. This method removes gas-liquid inclusions and isomorphous impurities inside the lattice by high-temperature heating. The heating temperature is high, which increases the cost, and hydrochloric acid is still required for pickling. The discharge problem of chlorine-containing pickling wastewater cannot be effectively solved. For another example, patent 202210395723.0 discloses a process for preparing high-purity quartz sand by purifying by acid leaching, which includes crushing the raw ore, first pickling, blending with a modification agent and high-temperature calcination, and then sequentially performing microwave treatment and a second pickling. The acid solution used for the first pickling is a mixed acid solution of hydrochloric acid, nitric acid and oxalic acid, and the acid solution used for the second pickling is a mixed acid solution of hydrochloric acid, nitric acid, oxalic acid and fluosilicic acid. This process uses a modification agent to perform infiltration modification treatment on the raw ore powder of quartz sand at high temperature, and then combines microwave treatment to improve the impurity removal rate. The high-temperature calcination time reaches more than 10 hours, the cost is relatively high, and acid solution containing hydrochloric acid is still required for pickling, which cannot fundamentally solve the problem of chlorine-containing pickling wastewater.

[0004] Therefore, how to provide a low-cost, chlorine-free pickling waste liquid, and acid-saving quartz sand pickling purification process is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide an ultrasonic-assisted acid-saving multi-step pickling and refining method for quartz sand, so as to solve the problems that the acid solution used in the existing quartz sand pickling and purification process contains hydrochloric acid, has high cost and large acid solution consumption.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand, comprising the following steps:

[0008] Pre-acid leaching the quartz sand in an acid leaching solution to obtain pre-acid leached quartz sand;

[0009] The pre-acid-leached quartz sand is subjected to intermittent ultrasonic-assisted pickling in a pickling solution to obtain pickled quartz sand;

[0010] The pickled quartz sand is washed, dried and sieved, thus completing the ultrasonic-assisted acid-saving multi-step pickled refined quartz sand;

[0011] Wherein, the acid leaching solution includes fluorine-containing waste sulfuric acid, hydrogen peroxide, and water;

[0012] The pickling solution comprises fluorine-containing waste sulfuric acid, hydrogen peroxide, a complexing agent, an organic acid and water.

[0013] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand method, the pre-acid leaching temperature is 30 to 50° C.; the pre-acid leaching time is 3 to 6 hours.

[0014] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand method, the composition of the fluorine-containing waste sulfuric acid in the acid leaching solution and the pickling solution independently includes, by mass fraction, 70-80% sulfuric acid, 2-6% hydrogen fluoride, and the remainder water.

[0015] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand method, the acid leaching solution contains, by mass fraction, 30-40% fluorine-containing waste sulfuric acid, 1-3% hydrogen peroxide, and the remainder is water.

[0016] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand method, the pickling solution contains, by mass fraction, 30-40% fluorine-containing waste sulfuric acid, 1-3% hydrogen peroxide, 0.1-0.5% complexing agent, 1-10% organic acid, and the remainder is water.

[0017] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining method for quartz sand, the complexing agent is ethylenediaminetetraacetic acid; and the organic acid is one or more of oxalic acid, formic acid, and citric acid.

[0018] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand method, the pickling temperature is 50-100° C.; and the pickling time is 2-5 hours.

[0019] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining method of quartz sand, the conditions of the intermittent ultrasonic wave are: the frequency is 20 to 80 kHz; the intermittent method is: ultrasonic wave for 30 to 60 minutes and pause for 10 to 30 minutes.

[0020] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining method of quartz sand, the usage ratio of the quartz sand and the acid leaching solution is 1-10 g:10 mL.

[0021] Preferably, in the above-mentioned ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand method, the dosage ratio of the pre-acid-leached quartz sand and the pickling solution is 1-5g:3mL.

[0022] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention first performs a pre-acid leaching treatment on the quartz sand before pickling, using industrial waste acid with a low concentration of fluorine content. After a certain period of pre-acid leaching, the lattice system of the quartz sand gradually opens, which is conducive to the entry of hydrofluoric acid into the lattice system in the subsequent pickling process to dissolve impurities, reduce the concentration of hydrofluoric acid used for pickling and reduce the amount of acid used for pickling. In addition, the low concentration of hydrofluoric acid can also avoid reacting with the effective components of the quartz sand to corrode the quartz sand.

[0024] (2) The present invention adds a complexing agent and a small amount of organic acid during the pickling process. The complexing agent can complex the metal ions on the surface of the quartz sand, and the use of the organic acid can improve the dissolution effect of impurities; at the same time, the use of ultrasound assistance can accelerate the diffusion speed and reaction speed of the acid solution, improve the removal rate of quartz sand impurities, shorten the reaction time, and save the amount of acid solution. In addition, ultrasound can also increase the generation of microcracks on the surface of quartz sand, cooperate with the effect of pre-acid leaching to open the quartz sand lattice, enhance the removal effect of gas-liquid inclusions and impurities inside the lattice, and make the pickling more sufficient. The present invention uses a complexing agent and an organic acid in combination with fluorine-containing waste sulfuric acid, ultrasound assistance during the pickling process, and pre-acid leaching to reduce the amount of pickling solution used, and at the same time, it can also improve the purity of quartz sand.

[0025] (3) The acid solution used for pre-acid leaching and pickling in the present invention is industrial waste acid, which not only realizes the resource utilization of industrial waste acid, but also reduces the cost of pickling and purification of quartz sand, turning industrial waste into treasure, which is conducive to large-scale promotion and application; at the same time, no chloride ions are added during the pickling process, and no chlorine-containing wastewater is generated, which effectively solves the problem of wastewater discharge in the traditional hydrochloric acid pickling process. DETAILED DESCRIPTION

[0026] The present invention provides a method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand, comprising the following steps:

[0027] Pre-acid leaching the quartz sand in an acid leaching solution to obtain pre-acid leached quartz sand;

[0028] The pre-acid-leached quartz sand is subjected to intermittent ultrasonic-assisted pickling in a pickling solution to obtain pickled quartz sand;

[0029] The pickled quartz sand is washed, dried and sieved to complete the ultrasonic-assisted acid-saving multi-step pickling and refined quartz sand.

[0030] In the present invention, the acid leaching solution preferably includes fluorine-containing waste sulfuric acid, hydrogen peroxide and water.

[0031] In the present invention, the composition of the fluorine-containing waste sulfuric acid in the acid leaching solution includes, by mass fraction: sulfuric acid is preferably 70-80%, more preferably 75-80%, more preferably 80%, hydrogen fluoride is preferably 2-6%, more preferably 3-5%, more preferably 3%, and the balance is water.

[0032] In the present invention, the acid leaching solution preferably contains 30-40% fluorine-containing waste sulfuric acid, more preferably 30-35%, more preferably 30%, and the hydrogen peroxide is preferably 1-3%, more preferably 1-2%, more preferably 1%, and the balance is water. In the present invention, a small amount of hydrogen peroxide is added to the acid leaching solution to oxidize and digest the trace organic matter in the fluorine-containing waste sulfuric acid.

[0033] In the present invention, the pre-acid leaching temperature is preferably 30-50°C, more preferably 35-45°C, and more preferably 40°C; the pre-acid leaching time is preferably 3-6h, more preferably 4-5h, and more preferably 4h.

[0034] In the present invention, the usage ratio of the quartz sand and the acid leaching solution is preferably 1-10 g:10 mL, more preferably 2-7 g:10 mL, and more preferably 3 g:10 mL.

[0035] In the present invention, the pickling solution preferably includes fluorine-containing waste sulfuric acid, hydrogen peroxide, a complexing agent, an organic acid, and water.

[0036] In the present invention, the composition of the fluorine-containing waste sulfuric acid in the pickling solution includes, by mass fraction: sulfuric acid is preferably 70-80%, more preferably 75-80%, more preferably 80%, hydrogen fluoride is preferably 2-6%, more preferably 3-5%, more preferably 3%, and the balance is water.

[0037] In the present invention, in the pickling solution, the fluorine-containing waste sulfuric acid is preferably 30-40%, more preferably 32-37%, more preferably 35%, the hydrogen peroxide is preferably 1-3%, more preferably 1-2%, more preferably 1%, the complexing agent is preferably 0.1-0.5%, more preferably 0.15-0.3%, more preferably 0.2%, the organic acid is preferably 1-10%, more preferably 5-10%, more preferably 10%, and the balance is water.

[0038] In the present invention, the complexing agent is preferably ethylenediaminetetraacetic acid.

[0039] In the present invention, the organic acid is preferably one or more of oxalic acid, formic acid and citric acid, and more preferably oxalic acid and citric acid.

[0040] In the present invention, the pickling temperature is preferably 50-100°C, more preferably 70-90°C, and more preferably 80°C; the pickling time is preferably 2-5h, more preferably 3-4h, and more preferably 3h.

[0041] In the present invention, the conditions of the intermittent ultrasonic wave are: the frequency is preferably 20-80kHz, more preferably 25-50kHz, and more preferably 40kHz; the intermittent method is preferably: ultrasonic wave 30-60min pause 10-30min, more preferably ultrasonic wave 40-60min pause 20-30min, more preferably ultrasonic wave 60min pause 30min.

[0042] In the present invention, the usage ratio of the pre-acid-leached quartz sand and the pickling solution is preferably 1-5 g:3 mL, more preferably 3-5 g:3 mL, and more preferably 5 g:3 mL.

[0043] In the present invention, the screening is to screen the quartz sand into four specifications of less than 20 meshes, 20-40 meshes, 40-80 meshes, and 80-120 meshes.

[0044] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand, comprising the following steps:

[0047] (1) Pre-acid leaching of quartz sand (iron content of 413 ppm) in an acid leaching solution at a dosage ratio of 3 g:10 mL, the pre-acid leaching temperature is 40° C., and the time is 4 h to obtain pre-acid leached quartz sand;

[0048] The acid leaching solution comprises, by mass fraction, 30% of fluorine-containing waste sulfuric acid, 1% of hydrogen peroxide, and the balance is water; the composition of the fluorine-containing waste sulfuric acid comprises, by mass fraction, 80% of sulfuric acid, 3% of hydrogen fluoride, and the balance is water;

[0049] (2) performing intermittent ultrasonic-assisted pickling of the pre-acid-leached quartz sand in a pickling solution at a dosage ratio of 5 g:3 mL, the pickling temperature being 80° C. for 3 h, and obtaining pickled quartz sand;

[0050] The pickling solution includes, by mass fraction, 35% of fluorine-containing waste sulfuric acid, 1% of hydrogen peroxide, 0.2% of ethylenediaminetetraacetic acid, 5% of oxalic acid, 5% of citric acid, and the balance is water; the composition of fluorine-containing waste sulfuric acid includes, by mass fraction, 80% of sulfuric acid, 3% of hydrogen fluoride, and the balance is water; the frequency of the intermittent ultrasonic wave is 40kHz, and the ultrasonic wave is suspended for 30 minutes after 60 minutes;

[0051] (3) The acid-washed quartz sand is washed with water for multiple times until it is neutral, and then dried in a drying device to a constant weight. The quartz sand is sieved to be divided into four specifications of less than 20 mesh, 20-40 mesh, 40-80 mesh, and 80-120 mesh, and then packaged, thus completing the ultrasonic-assisted acid-saving multi-step acid-washing refined quartz sand.

[0052] After testing, the silica content of the quartz sand obtained after the operation of this embodiment is 99.24%, the iron content is 43 ppm, and the whiteness is 86.2%.

[0053] Example 2

[0054] This embodiment provides a method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand, comprising the following steps:

[0055] (1) Pre-acid leaching of quartz sand (with an iron content of 413 ppm) in an acid leaching solution at a ratio of 5 g:10 mL, at a pre-acid leaching temperature of 30° C. for 5 h, to obtain pre-acid leached quartz sand;

[0056] The acid leaching solution comprises, by mass fraction, 32% of fluorine-containing waste sulfuric acid, 2% of hydrogen peroxide, and the balance of water; the composition of fluorine-containing waste sulfuric acid comprises, by mass fraction, 80% of sulfuric acid, 3% of hydrogen fluoride, and the balance of water;

[0057] (2) performing intermittent ultrasonic-assisted pickling of the pre-acid-leached quartz sand in a pickling solution at a ratio of 4 g:3 mL, the pickling temperature being 60° C. for 4 h, and obtaining pickled quartz sand;

[0058] The pickling solution includes, by mass fraction, 30% of fluorine-containing waste sulfuric acid, 1% of hydrogen peroxide, 0.1% of ethylenediaminetetraacetic acid, 2% of oxalic acid, and the balance is water; the composition of fluorine-containing waste sulfuric acid includes, by mass fraction, 80% of sulfuric acid, 3% of hydrogen fluoride, and the balance is water; the frequency of the intermittent ultrasonic wave is 30kHz, and the ultrasonic wave is performed for 30 minutes and paused for 30 minutes;

[0059] (3) The acid-washed quartz sand is washed with water for multiple times until it is neutral, and then dried in a drying device to a constant weight. The quartz sand is sieved to be divided into four specifications of less than 20 mesh, 20-40 mesh, 40-80 mesh, and 80-120 mesh, and then packaged, thus completing the ultrasonic-assisted acid-saving multi-step acid-washing refined quartz sand.

[0060] After testing, the silica content of the quartz sand obtained after the operation of this embodiment is 98.87%, the iron content is 46 ppm, and the whiteness is 85.5%.

[0061] Example 3

[0062] This embodiment provides a method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand, comprising the following steps:

[0063] (1) Pre-acid leaching of quartz sand (iron content of 413 ppm) in an acid leaching solution at a dosage ratio of 3 g:10 mL, at a pre-acid leaching temperature of 45° C. for 3 h, to obtain pre-acid leached quartz sand;

[0064] The acid leaching solution comprises, by mass fraction, 40% of fluorine-containing waste sulfuric acid, 2% of hydrogen peroxide, and the balance is water; the composition of the fluorine-containing waste sulfuric acid comprises, by mass fraction, 80% of sulfuric acid, 3% of hydrogen fluoride, and the balance is water;

[0065] (2) performing intermittent ultrasonic-assisted pickling of the pre-acid-leached quartz sand in a pickling solution at a dosage ratio of 2 g:3 mL, the pickling temperature being 70° C. for 2 h, and obtaining pickled quartz sand;

[0066] The pickling solution includes, by mass fraction, 36% of fluorine-containing waste sulfuric acid, 3% of hydrogen peroxide, 0.15% of ethylenediaminetetraacetic acid, 7% of formic acid, and the balance is water; the composition of fluorine-containing waste sulfuric acid includes, by mass fraction, 80% of sulfuric acid, 3% of hydrogen fluoride, and the balance is water; the frequency of the intermittent ultrasonic wave is 50kHz, and the ultrasonic wave is suspended for 10 minutes after 60 minutes;

[0067] (3) The acid-washed quartz sand is washed with water for multiple times until it is neutral, and then dried in a drying device to a constant weight. The quartz sand is sieved to be divided into four specifications of less than 20 mesh, 20-40 mesh, 40-80 mesh, and 80-120 mesh, and then packaged, thus completing the ultrasonic-assisted acid-saving multi-step acid-washing refined quartz sand.

[0068] After testing, the silica content of the quartz sand obtained after the operation of this embodiment is 99.06%, the iron content is 47 ppm, and the whiteness is 84.7%.

[0069] Example 4

[0070] This embodiment provides a method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand, comprising the following steps:

[0071] (1) Pre-acid leaching of quartz sand (iron content of 413 ppm) in an acid leaching solution at a dosage ratio of 7 g:10 mL, the pre-acid leaching temperature is 50° C., and the time is 6 h, to obtain pre-acid leached quartz sand;

[0072] The acid leaching solution comprises, by mass fraction, 40% of fluorine-containing waste sulfuric acid, 3% of hydrogen peroxide, and the balance of water; the composition of fluorine-containing waste sulfuric acid comprises, by mass fraction, 80% of sulfuric acid, 3% of hydrogen fluoride, and the balance of water;

[0073] (2) performing intermittent ultrasonic-assisted pickling of the pre-acid-leached quartz sand in a pickling solution at a dosage ratio of 1 g:3 mL, the pickling temperature being 100° C. for 5 h, and obtaining pickled quartz sand;

[0074] The pickling solution includes, by mass fraction, 40% of fluorine-containing waste sulfuric acid, 3% of hydrogen peroxide, 0.4% of ethylenediaminetetraacetic acid, 10% of citric acid, and the balance is water; the composition of fluorine-containing waste sulfuric acid includes, by mass fraction, 80% of sulfuric acid, 3% of hydrogen fluoride, and the balance is water; the frequency of the intermittent ultrasonic wave is 70kHz, and the ultrasonic wave is performed for 30 minutes and then paused for 30 minutes;

[0075] (3) The acid-washed quartz sand is washed with water for multiple times until it is neutral, and then dried in a drying device to a constant weight. The quartz sand is sieved to be divided into four specifications of less than 20 mesh, 20-40 mesh, 40-80 mesh, and 80-120 mesh, and then packaged, thus completing the ultrasonic-assisted acid-saving multi-step acid-washing refined quartz sand.

[0076] After testing, the silica content in the quartz sand obtained after the operation of this embodiment is 99.15%, the iron content is 42 ppm, and the whiteness is 85.8%.

[0077] Comparative Example 1

[0078] This comparative example provides a method for refining quartz sand, which is specifically referred to in Example 1, except that the pre-acid leaching treatment in step (1) is not performed.

[0079] After testing, the silica content of the quartz sand obtained after the operation of this comparative example was 96.52%, the iron content was 117 ppm, and the whiteness was 81.4%.

[0080] Comparative Example 2

[0081] This comparative example provides a method for refining quartz sand, which is specifically described in Example 1, except that intermittent ultrasonic assistance is not performed in step (2).

[0082] After testing, the silica content of the quartz sand obtained after the operation of this comparative example was 97.96%, the iron content was 93 ppm, and the whiteness was 82.3%.

[0083] Comparative Example 3

[0084] This comparative example provides a method for refining quartz sand, which is specifically referred to in Example 1, except that the pre-acid leaching treatment in step (1) and the intermittent ultrasonic assistance in step (2) are not performed.

[0085] After testing, the silica content of the quartz sand obtained after the operation of this comparative example was 95.68%, the iron content was 141 ppm, and the whiteness was 79.6%.

[0086] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand, characterized in that: The following steps are involved: Pre-acid leaching the quartz sand in an acid leaching solution to obtain pre-acid leached quartz sand; The pre-acid-leached quartz sand is subjected to intermittent ultrasonic-assisted pickling in a pickling solution to obtain pickled quartz sand; The pickled quartz sand is washed, dried and sieved, thus completing the ultrasonic-assisted acid-saving multi-step pickled refined quartz sand; Wherein, the acid leaching solution includes fluorine-containing waste sulfuric acid, hydrogen peroxide, and water; The pickling solution comprises fluorine-containing waste sulfuric acid, hydrogen peroxide, a complexing agent, an organic acid and water.

2. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 1, characterized in that: The pre-acid leaching temperature is 30-50° C.; the pre-acid leaching time is 3-6 hours.

3. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 2, characterized in that: In the acid leaching solution and the pickling solution, the composition of the fluorine-containing waste sulfuric acid independently includes, by mass fraction, 70-80% sulfuric acid, 2-6% hydrogen fluoride, and the balance water.

4. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 2 or 3, characterized in that: The acid leaching solution contains 30-40% fluorine-containing waste sulfuric acid, 1-3% hydrogen peroxide, and the balance water, by mass fraction.

5. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 4, characterized in that: The pickling solution contains, by mass fraction, 30-40% of fluorine-containing waste sulfuric acid, 1-3% of hydrogen peroxide, 0.1-0.5% of a complexing agent, 1-10% of an organic acid, and the balance of water.

6. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 3, characterized in that: The complexing agent is ethylenediaminetetraacetic acid; the organic acid is one or more of oxalic acid, formic acid and citric acid.

7. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 2 or 6, characterized in that: The pickling temperature is 50-100° C.; the pickling time is 2-5 hours.

8. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 7, characterized in that: The intermittent ultrasonic conditions are: a frequency of 20 to 80 kHz; and an intermittent method of ultrasonication for 30 to 60 minutes and a pause of 10 to 30 minutes.

9. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 7, characterized in that: The usage ratio of the quartz sand and the acid leaching solution is 1-10 g:10 mL.

10. The method for ultrasonic-assisted acid-saving multi-step pickling and refining quartz sand according to claim 8 or 9, characterized in that: The dosage ratio of the pre-acid-leached quartz sand and the pickling solution is 1-5 g: 3 mL.