Pickling process for preparing high-purity quartz sand by using mixed waste acid of hydrofluoric acid and hydrochloric acid

Abstract

The invention discloses a pickling process for preparing high-purity quartz sand by using mixed waste acid of hydrofluoric acid and hydrochloric acid, and belongs to the technical field of purification production of high-purity quartz sand. Comprising the steps of ore selection, surface cleaning, jaw breaking, hammer breaking, screening, magnetic separation, impurity removal through flotation, gas-liquid inclusion removal through high-temperature microwaves, primary filtration of waste acid, fine filtration of waste acid, compounding of mixed waste acid, calcination, magnetic separation and the like. The pickling process has high purification efficiency, the acid liquor consumption can be further reduced by combining the recycling of the waste acid, the comprehensive cost is lower than that of the traditional process, the acid leaching waste liquor of the process can be repeatedly used for 2-3 times by supplementing 5-8% of the new acid after simple pH regulation, the comprehensive acid consumption is reduced by 55% or above, less pollutant emission is realized, and the method is suitable for industrial production. The treatment cost of the waste acid is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-purity quartz sand production, and relates to an acid washing process for preparing high-purity quartz sand by using mixed waste acid of hydrofluoric acid and hydrochloric acid. Background Art

[0002] High-purity quartz sand is a national strategic product, with the SiO2 content generally higher than 99.99%, and is widely used in high-tech industries such as integrated circuits, medicine, military, aerospace, optical communication, lasers, and the electronics industry, especially high-end optical electronics engineering. After physical purification, almost all mineral impurities existing in monomer form can be removed, and the content of impurity elements after impurity removal is at a relatively low level. The main impurity sources that cannot be removed by physical purification are gas-liquid inclusions and isomorphic impurities inside the crystal lattice, and these impurities are the key factors restricting the preparation of high-purity quartz products, so chemical deep purification is required. The acid treatment method is an important purification method in chemical purification. Acid treatment mainly removes the impurities existing on the surface of quartz sand particles in the form of inclusions or embedded in the particles. There are still a small amount of impurity minerals at grain boundaries, microcracks, and inside the crystal. The acid treatment method is mainly to remove this part of the impurities. Among them, the acid leaching method is the most widely used, and a mixed solution of hydrofluoric acid, sulfuric acid, hydrochloric acid, and nitric acid is often used to purify quartz sand.

[0003] At present, a large amount of hydrofluoric acid and hydrochloric acid are used for purifying quartz sand. The large amount of acid used generates a large amount of waste acid, which not only pollutes the environment, but also the cost of using acid solution is relatively high. Therefore, on the premise of ensuring the purification purity of quartz sand, it is very necessary to recycle the waste acid and reduce the cost. Summary of the Invention

[0004] In order to fill the gap in the existing technology, the present invention provides an acid washing process for preparing high-purity quartz sand by using mixed waste acid of hydrofluoric acid and hydrochloric acid to overcome the deficiencies existing in the prior art.

[0005] The technical solution of the present invention: An acid washing process for preparing high-purity quartz sand by using mixed waste acid of hydrofluoric acid and hydrochloric acid, comprising the following steps: S1: Primary filtration, using a 20-mesh sieve to remove large particle suspensions in the waste acid; S2: Precision filtration, using a 5μm ceramic membrane filtration system to intercept micron-sized impurities to obtain first-stage waste acid; S3: Add 5%-10% industrial hydrofluoric acid to the first-stage waste acid to obtain mixed waste acid, and the mixed waste acid is prepared by mixing the first-stage waste acid and industrial hydrofluoric acid at a molar ratio of 20:1-3; S4: Add mixed waste acid to pickle the water-quenched quartz sand. After shaking the mixed waste acid evenly, add it to the pickling reactor and shake well. The liquid-solid ratio of the mixed waste acid to the quartz sand is 2-4:1, and the temperature is controlled at 100-120 °C for acid leaching reaction. The pickling reactor rotates once every 1-3 minutes. After pickling for 6-10 hours, drain the water from the quartz sand and then add ultrapure water to wash the sand containing residual acid solution, and then calcine it; S5: Conduct magnetic separation on the calcined quartz sand 4-8 times. The feeding temperature for magnetic separation is ≤50 °C. After magnetic separation, high-purity quartz sand is obtained.

[0006] Furthermore, in S3, the concentration of industrial hydrofluoric acid is ≥49%.

[0007] Furthermore, the water-quenched quartz sand in S4 is prepared by the following steps: Step 1: Select high-grade quartz ore and wash the surface of the ore to remove non-mineral impurities such as surface soil and other attachments; Step 2: Through the processes of jaw crushing and hammer crushing, break the large ore into small ores, and then through crushing and screening, collect particles with a mesh size of 50-200 as the raw material for crushed semi-finished products; Step 3: Conduct magnetic separation on the raw material for crushed semi-finished products through a magnetic separator to remove magnetic substances; Step 4: Use flotation to remove impurities in the sand, including iron impurities and associated ore impurities such as feldspar and mica; Step 5: Release the gas-liquid inclusions and isomorphic impurities inside the crystal lattice through two methods of high-temperature and microwave heating, and then conduct water quenching treatment.

[0008] Furthermore, in Step 1, the quartz ore is vein quartz or pegmatite.

[0009] Furthermore, in Step 4, the flotation process is as follows: First, add water to the flotation machine to wash and drain the raw material for crushed semi-finished products after magnetic separation; then add sodium hydroxide as a pH adjuster and use it in combination with QS flotation collector for rough flotation to remove impurities, including associated ores such as feldspar and mica and non-magnetic associated ores; then add sulfuric acid as a pH adjuster and use it in combination with 608 anionic collector and kerosene foaming agent for fine flotation to remove iron impurities; finally, add sulfuric acid as an adjuster and use it in combination with dodecylamine cationic collector for fine flotation to remove associated ore impurities such as feldspar and mica.

[0010] Furthermore, in Step 5, use a microwave heating rotary furnace to heat the quartz sand to a high temperature of 600-1300 °C. Utilize the selective heating characteristics of microwaves to release the gas-liquid inclusions and isomorphic impurities inside the crystal lattice, and then conduct water quenching treatment.

[0011] Further, the mixed waste acid in S3 is prepared from primary waste acid and industrial hydrofluoric acid with a molar ratio of 20:1 - 3.

[0012] Further, the solid - liquid ratio of quartz sand and mixed waste acid in S4 is 3:1. Further, in S4, the pickling reactor rotates once every 1 - 3 minutes. After 8 hours of pickling.

[0013] Further, the number of magnetic separation times in S5 is 6 times, and the magnetic separation temperature is 45 °C.

[0014] The beneficial effects of the present invention are as follows: By recycling waste acid, the present invention reduces the discharge of hazardous waste. In traditional pickling processes, it is difficult to treat waste acid. However, the recycling of waste acid can convert the low - concentration acid solution after pickling into raw materials for other production processes, achieving less pollutant emissions and reducing the treatment cost of waste acid; The present invention recycles the waste acid after pickling and re - uses it in the process of quartz sand purification, enabling the utilization rate of the acid solution to reach 90% - 95%. This significantly reduces the cost of purchasing new acid. The pickling process itself has a high purification efficiency. Combining the recycling of waste acid can further reduce acid solution consumption, and the comprehensive cost is lower than that of traditional processes. After simply adjusting the pH of the acid - leaching waste liquid of this process, adding 5 - 8% new acid can make it reusable 2 - 3 times, and the comprehensive acid consumption is reduced by more than 55%.

[0015] The waste acid purification technology of the present invention is combined with pre - treatment processes of quartz sand such as flotation and magnetic separation to form a comprehensive purification plan. After pickling and purification by this process, the Fe content is stably ≤0.5 ppm, and the purification effect reaches the 4N9 level, with outstanding purification effects. On the premise of ensuring the purification effect, low pollution and low cost are achieved. Specific Embodiments

[0016] The following details the specific embodiments of the present invention. Example 1

[0017] Production of water - quenched quartz sand (i.e., quartz sand rough material): Select high - grade vein quartz or pegmatite or other quartz ore, and use a cleaning machine to clean the surface of the ore to remove non - mineral impurities such as surface soil and other attachments; Through the jaw crusher and hammer crusher processes, large ore is broken into small ore, and then through crushing and screening, particles with a size of 50 - 200 meshes are collected as the crushed semi - finished raw material; Use a magnetic separator to perform magnetic separation on the crushed semi - finished raw material to remove magnetic substances; Flotation to remove impurities: First, add water to the flotation machine to wash and drain the crushed semi-finished raw materials after magnetic separation; then add sodium hydroxide as a pH adjuster and use it in combination with QS flotation collector for rough flotation to remove impurities, including associated ores such as feldspar and mica and non-magnetic associated ores; then add sulfuric acid as a pH adjuster and use it in combination with 608 anionic collector and kerosene foaming agent for fine flotation to remove iron impurities; finally, add sulfuric acid as an adjuster and use it in combination with dodecylamine cationic collector for fine flotation to remove associated impurities such as feldspar and mica in the ore. Using a microwave heating rotary furnace, heat the quartz sand to a high temperature of 600 - 1300 °C. Utilize the selective heating characteristic of microwaves to remove the gas-liquid inclusions inside the quartz sand, so that the impurities therein are released. This step is to release the gas-liquid inclusions and isomorphic impurities inside the crystal lattice through two methods of high temperature and microwave heating, and then perform water quenching treatment.

[0018] Compound preparation of mixed waste acid: Primary filtration: Use a 20-mesh sieve to remove large particle suspensions in the waste acid; Precision filtration: Use a 5μm ceramic membrane filtration system to intercept micron-sized impurities to obtain the first-stage waste acid; Mixing and compounding: Add 5% industrial hydrofluoric acid to the first-stage waste acid to obtain the mixed waste acid, and the mixed waste acid is prepared by mixing the first-stage waste acid and industrial hydrofluoric acid in a molar ratio of 20:1.

[0019] Pickling process: Add the mixed waste acid to pickle the water-quenched quartz sand. After shaking the mixed waste acid evenly, add it to the pickling reaction kettle and shake well. The liquid-solid ratio of the mixed waste acid and quartz sand is 2:1, and the temperature is controlled at 100 °C for acid leaching reaction. The pickling reaction kettle rotates one week every 1 minute. After pickling for 6 hours, drain the water from the quartz sand, add ultrapure water to wash the sand containing residual acid solution, and then calcine; Perform magnetic separation on the calcined quartz sand 4 times. The magnetic separation feeding temperature is 50 °C, and high-purity quartz sand is obtained after magnetic separation.

[0020] Testing: Detect the elements of the pickled and dried sample through an ICP inductively coupled plasma emission chromatograph for the pickled quartz sand. The test results of the elements show that the leaching effect of the mixed acid is good, and it has a good removal effect on the ore containing element impurities such as Na, K, and Fe.

[0021] Through the magnetic separation process, substances such as Na, K, and Fe in the sand can be well removed, and the purity grade of the prepared high-purity quartz sand exceeds the 4N8 level and reaches the 4N9 level. Example 2

[0022] Compound preparation of mixed waste acid: Primary filtration: Use a 20-mesh sieve to remove large particle suspensions in the waste acid; Precise filtration: A 5μm ceramic membrane filtration system is used to intercept micron-sized impurities to obtain primary waste acid; Mixing and compounding: 7.5% industrial hydrofluoric acid is added to the primary waste acid to obtain mixed waste acid, and the mixed waste acid is prepared from primary waste acid and industrial hydrofluoric acid with a molar ratio of 20:1.6.

[0023] Pickling process: Add the mixed waste acid to pickle the water-quenched quartz sand. After shaking the mixed waste acid evenly, add it to the pickling reaction kettle and shake well. The liquid-solid ratio of the mixed waste acid to the quartz sand is 3:1, and the temperature is controlled at 110°C for acid leaching reaction. The pickling reaction kettle rotates once every 2 minutes. After 8 hours of pickling, drain the water from the quartz sand and add ultrapure water to wash the sand containing residual acid solution, and then calcine; Perform magnetic separation on the calcined quartz sand 6 times. The magnetic separation feeding temperature is 45°C, and high-purity quartz sand is obtained after magnetic separation.

[0024] Testing: Pass the pickled and dried sample through an ICP inductively coupled plasma emission chromatograph to detect the elements of the pickled quartz sand. The test results of the elements show that the leaching effect of the mixed acid is good, and it has a good removal effect on the ore containing element impurities such as Na, K, and Fe.

[0025] Through the magnetic separation process, substances such as Na, K, and Fe in the sand can be removed well, and the purity grade of the prepared high-purity quartz sand exceeds the 4N8 level and reaches the 4N9 level. Example 3

[0026] Compound preparation of mixed waste acid: Primary filtration: Use a 20-mesh sieve to remove large particle suspensions in the waste acid; Precise filtration: A 5μm ceramic membrane filtration system is used to intercept micron-sized impurities to obtain primary waste acid; Mixing and compounding: 10% industrial hydrofluoric acid is added to the primary waste acid to obtain mixed waste acid, and the mixed waste acid is prepared from primary waste acid and industrial hydrofluoric acid with a molar ratio of 20:3.

[0027] Pickling process: Add the mixed waste acid to pickle the water-quenched quartz sand. After shaking the mixed waste acid evenly, add it to the pickling reaction kettle and shake well. The liquid-solid ratio of the mixed waste acid to the quartz sand is 4:1, and the temperature is controlled at 120°C for acid leaching reaction. The pickling reaction kettle rotates once every 3 minutes. After 10 hours of pickling, drain the water from the quartz sand and add ultrapure water to wash the sand containing residual acid solution, and then calcine; Perform magnetic separation on the calcined quartz sand 8 times. The magnetic separation feeding temperature is 40°C, and high-purity quartz sand is obtained after magnetic separation.

[0028] Test: After pickling and drying the samples, the elements in the pickled quartz sand were detected by an ICP inductively coupled plasma emission chromatograph. The test results of the elements showed that the pickling effect of the mixed acid was good, and it had a good removal effect on the elemental impurities such as Na, K, and Fe in the ore.

[0029] Through the magnetic separation process, substances such as Na, K, and Fe in the sand can be removed well. The purity grade of the prepared high-purity quartz sand exceeds the 4N8 level and reaches the 4N9 level.

[0030] Based on the above embodiments, a cost comparison was made with the traditional pickling process. After the waste acid recycling of the present invention, the procurement cost of the acid solution decreased by 50 - 75%; the treatment cost of the waste acid (including the waste acid treatment cost of our company and the treatment cost of a third-party hazardous waste treatment company) decreased by 60 - 80%. The details are shown in the following table: Through the waste acid recycling of the present invention, the discharge of hazardous waste is reduced. In the traditional pickling process, it is difficult to treat waste acid, while the recycling of waste acid can convert the low-concentration acid solution after pickling into raw materials for other production links, realizing less or zero discharge of pollutants; The present invention recycles the waste acid after pickling and reuses it in the process of quartz sand purification, so that the utilization rate of the acid solution reaches 90% - 95%, greatly reducing the procurement cost of new acid. The pickling process itself has a high purification efficiency. Combining the recycling of waste acid can further reduce the acid solution consumption. The comprehensive cost is lower than that of the traditional process. After simple pH adjustment of the acid leaching waste liquid of this process, adding 5 - 8% new acid can make it reusable 2 - 3 times, and the comprehensive acid consumption is reduced by more than 55%.

[0031] The waste acid purification technology of the present invention is combined with the pretreatment processes of quartz sand such as flotation and magnetic separation to form a comprehensive purification plan. After pickling and purification by this process, the Fe content is stably ≤0.5 ppm, and the purification effect reaches the 4N9 level, with outstanding purification effect. On the premise of ensuring the purification effect, low pollution and low cost are achieved.

[0032] The above shows and describes the basic principles, main features and advantages of the present invention. The present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. An acid pickling process for preparing high-purity quartz sand using a mixed waste acid of hydrofluoric acid and hydrochloric acid, characterized in that: It includes the following steps: S1: Primary filtration, using a 20-mesh sieve to remove large particulate suspensions in the waste acid; S2: Precision filtration, using a 5μm ceramic membrane filtration system to intercept micron-sized impurities to obtain primary waste acid; S3: Add 5%-10% industrial hydrofluoric acid to the primary waste acid to obtain a mixed waste acid, and the mixed waste acid is prepared from the primary waste acid and industrial hydrofluoric acid in a molar ratio of 20:1-3; S4: Add the mixed waste acid to pickle the water-quenched quartz sand. After shaking the mixed waste acid evenly, add it to the pickling reaction kettle and shake well. The liquid-solid ratio of the mixed waste acid to the quartz sand is 2-4:1, and the temperature is controlled at 100-120°C for acid leaching reaction. The pickling reaction kettle rotates one week every 1-3 minutes. After pickling for 6-10 hours, drain the water from the quartz sand and add ultrapure water to wash the sand containing residual acid solution, and then calcine; S5: Conduct magnetic separation on the calcined quartz sand 4-8 times, and the magnetic separation feeding temperature ≤ 50°C. After magnetic separation, high-purity quartz sand is obtained.

2. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as described in claim 1, characterized in that: The concentration of industrial hydrofluoric acid in S3 ≥ 49%.

3. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as described in claim 1, wherein: The water-quenched quartz sand in S4 is prepared by the following steps: Step 1: Select high-grade quartz ore and wash the surface of the ore to remove non-mineral impurities such as surface soil and other attachments; Step 2: Through the jaw crusher and hammer crusher processes, break the large ore into small ores, and then through crushing and screening, collect particles of 50-200 meshes as the crushed semi-finished raw material; Step 3: Conduct magnetic separation on the crushed semi-finished raw material by a magnetic separator to remove magnetic substances; Step 4: Flotation to remove impurities in the sand, including iron impurities and ore associated impurities such as feldspar and mica; Step 5: Release the gas-liquid inclusions and isomorphic impurities inside the crystal lattice through two methods of high-temperature and microwave heating, and then conduct water quenching treatment.

4. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as described in claim 3, characterized in that: The quartz ore in Step 1 is vein quartz or pegmatite.

5. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as described in claim 3, characterized in that: In Step 4, the flotation process is as follows: First, add water to the flotation machine to wash and drain the crushed semi-finished raw material after magnetic separation; then add sodium hydroxide as a pH adjuster and use it in combination with a QS flotation collector for rough flotation to remove impurities, including associated ores such as feldspar and mica and non-magnetic associated ores; then add sulfuric acid as a pH adjuster and use it in combination with a 608 anionic collector and kerosene foaming agent for fine flotation to remove iron impurities; finally, add sulfuric acid as an adjuster and use it in combination with a dodecylamine cationic collector for fine flotation to remove ore associated impurities such as feldspar and mica.

6. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as described in claim 1, characterized in that: In Step 5, a microwave heating rotary furnace is used to heat the quartz sand to a high temperature of 600-1300°C, and using the microwave selective heating characteristic, release the gas-liquid inclusions and isomorphic impurities inside the crystal lattice and then conduct water quenching treatment.

7. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as described in claim 1, characterized in that: In S3, the mixed waste acid is prepared from the primary waste acid and industrial hydrofluoric acid in a molar ratio of 20:1-3.

8. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as claimed in claim 1, characterized in that: In S4, the solid-liquid ratio of the quartz sand to the mixed waste acid is 3:

1.

9. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as described in claim 1, characterized in that: In S4, the pickling reaction kettle rotates one week every 1-3 minutes, and after pickling for 8 hours.

10. The pickling process for preparing high-purity quartz sand using the mixed waste acid of hydrofluoric acid and hydrochloric acid as described in claim 1, characterized in that: In S5, the number of magnetic separation times is 6 times, and the magnetic separation temperature is 45°C.