Purification process for improving sodium ion removal rate of high-purity quartz sand

Abstract

The invention relates to the technical field of quartz sand purification processing, in particular to a purification process for improving the sodium ion removal rate of high-purity quartz sand. The technology aims at solving the technical problems that when soluble sodium salt and lattice embedded state sodium (such as Al < 3 + > charge compensation type) coexist in high-purity quartz sand, removal is not thorough through a traditional technology, and precipitates are likely to be generated. Efficient removal is achieved through a hydrothermal dissolution-acid pickling impurity removal-flotation separation synergistic mechanism. Firstly, soluble sodium salt is dissolved out preferentially under the hydrothermal condition of 65 DEG C, so that it is avoided that in subsequent acid pickling, HF reacts with the sodium salt to generate Na2SiF6 sediment; then, an HF-HCl mixed acid system is adopted to selectively etch lattice channels at 70 DEG C and open a gas-liquid inclusion, so that embedded sodium is promoted to migrate and dissolve out; and finally, separating sodium-containing gangue (such as albite) exposed by pickling through flotation. According to the process, the hydrothermal times (2-3 times) can be dynamically adjusted according to the ore characteristics, stable production of semiconductor-grade quartz sand is achieved with low energy consumption which saves more than 30% of energy compared with a chloridizing roasting process, and the process is suitable for high-valued utilization of domestic vein quartz ore.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of quartz sand purification processing, and particularly relates to a purification process for improving the sodium ion removal rate of high-purity quartz sand. TECHNICAL BACKGROUND

[0002] High-purity quartz sand is a key basic material for semiconductor wafer manufacturing and photovoltaic monocrystalline silicon growth, and the impurity content directly affects the high-temperature stability of a quartz crucible and the quality of a monocrystalline silicon product. Among the many impurity elements, sodium ions (Na + ) are one of the key indicators of purity control because of their high-temperature migration activity and the fact that they can easily cause quartz glass to crystallize and cause device failure. The limit value requirement for sodium ions is extremely strict for semiconductor-grade products (4N8 grade), and although China is rich in vein quartz resources, the occurrence state of sodium impurities in different resources is significantly different - sodium in some resources is mainly in the form of a lattice-embedded state (such as Al 3+ replacing Si 4+ to form a charge compensation structure), and sodium in other resources is mainly in the form of a chloride or silicate mineral in a gas-liquid inclusion. This complexity makes it difficult for a single purification process to achieve deep sodium removal, which is one of the bottlenecks restricting the development of high-end quartz sand.

[0003] Existing processes face multiple challenges in sodium ion removal: physical separation methods (such as scrubbing and magnetic separation) can remove free-state sodium and sodium-containing vein minerals, but have limited effect on lattice-embedded sodium; high-temperature chloridizing roasting can partially volatilize sodium impurities, but has high energy consumption and insufficient selectivity for specific occurrence states of sodium, and the residual amount still cannot meet the needs of high-end products. In particular, the acid washing process - in the conventional HF-HCl mixed acid treatment, the fluorosilicic acid (H2SiF6) generated by the reaction of HF with quartz easily combines with sodium ions to form sodium fluorosilicate (Na2SiF6) precipitates. The precipitates are difficult to dissolve in water, not only blocking the microcracks on the surface of the quartz to hinder the dissolution of sodium ions, but also possibly introducing secondary pollution, resulting in a significant reduction in the sodium removal efficiency. SUMMARY

[0004] The application aims to provide a purification process for improving the sodium ion removal rate of high-purity quartz sand, which, based on the different occurrence characteristics of lattice-embedded sodium and soluble sodium salts, achieves efficient dissolution of soluble sodium salts through a hydrothermal dissolution process, removes inclusion bodies and lattice migration state sodium based on the penetration of HF in the acid washing process, and removes residual impurities such as mica and feldspar stripped by acid washing through a physical separation method such as flotation.

[0005] The specific technical solutions adopted are as follows:

[0006] A purification process for improving the sodium ion removal rate of high-purity quartz sand, comprising the following steps:

[0007] S1, hydrothermal dissolution

[0008] Pour 65°C hot water into the hydrothermal reaction tank, add quartz sand under stirring conditions (150 rpm), maintain a solid-liquid ratio of 1-2:1, and continue stirring for 30 minutes;

[0009] S2, pickling

[0010] The quartz sand treated in step S1 is centrifuged and dehydrated, and then transferred to a pickling reactor. A mixed acid (a combination of hydrofluoric acid and hydrochloric acid) is added, and the heating and stirring functions of the reactor are turned on for pickling;

[0011] S3, flotation

[0012] The quartz sand after the acid washing in step S2 is rinsed to neutrality, placed in a flotation machine, and the pulp concentration is adjusted to 25-30% and flotation separation is performed.

[0013] Preferably, in step S1, the hydrothermal dissolution treatment can be repeated 2-3 times depending on the original sodium content of the quartz ore.

[0014] Preferably, in step S2, the mixed acid consists of hydrofluoric acid and hydrochloric acid in a volume ratio of 1:1, and the temperature is kept constant during pickling.

[0015] Preferably, in step S3, hydrochloric acid is used to adjust the pH of the pulp to 2-3 before flotation, and the collector is selected from at least one of mixed ammonium, dodecylamine and rosin amine, and the flotation treatment is performed 2-3 times according to the impurity content.

[0016] Preferably, in step S3, after flotation, the quartz sand is washed with pure water, centrifuged and dehydrated, and dried to obtain high-purity quartz sand.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention aims to solve the problem of removing sodium ions with complex occurrence forms (coexistence of soluble sodium salts and lattice embedded sodium) in high-purity quartz sand. The invention realizes efficient targeted removal through a synergistic process of hydrothermal dissolution-mixed acid activation-flotation separation: hydrothermal dissolution (65°C) preferentially dissolves soluble sodium salts such as NaCl, significantly reduces the concentration of free sodium, and avoids the micropore blockage caused by sodium fluorosilicate (Na2SiF6) precipitation generated during the pickling process from the source; the HF-HCl mixed acid system opens the gas-liquid inclusions at a certain temperature and selectively etches the lattice channels, promoting the charge compensation type Na + Migration and dissolution; the flotation process uses amine collectors such as dodecylamine to target and separate sodium-containing gangue (such as albite) exposed by acid washing. This process dynamically adjusts the number of hydrothermal times (2-3 times) and flotation intensity based on the characteristics of the ore, achieving stable removal of sodium ions to semiconductor-grade standards (Na2O3) with low energy consumption (saving more than 30% compared to 1200℃ chlorination roasting). + <1ppm), taking into account both high efficiency and mineral source universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The process flow chart of the present invention is shown DETAILED DESCRIPTION

[0020] The following examples all use a domestic natural vein quartz coarse sand with a particle size of 80-200 mesh.

[0021] Implementation 1

[0022] (1) Pour 65°C hot water into the hydrothermal reaction tank, add quartz sand under stirring conditions (150 rpm), maintain a solid-liquid ratio of 1:2, and continue stirring for 30 minutes.

[0023] (2) The quartz sand obtained in step (1) is placed in a centrifuge for dehydration and then transferred into a polytetrafluoroethylene-lined reactor, and a mixed acid of 10% hydrochloric acid and 12% hydrofluoric acid is added; the reactor is set to turn upside down at a slow speed of 90 seconds per revolution for 24 hours, and the volume ratio of the mixed quartz sand and the acid solution is controlled to be 2:1.

[0024] (3) The quartz sand obtained in step (2) after pickling is washed with pure water until neutral and adjusted to a 25% quartz sand slurry, which is added to a flotation machine for flotation operation, hydrochloric acid is added to the slurry to adjust the pH value to 3.0, and a collector composed of rosin amine and dodecylamine is added in an amount of 150 g / t. After stirring to generate foam, the flotation is carried out for 20 minutes by scraping the foam.

[0025] (4) The quartz sand treated in step (3) is placed in a drying kettle and heated and dried in a vacuum state, wherein the drying temperature is 90° C. and the drying time is 9 hours.

[0026] Implementation 2

[0027] (1) Pour 65°C hot water into the hydrothermal reaction tank, add quartz sand under stirring conditions (150 rpm), maintain a solid-liquid ratio of 1:2, and stir continuously for 30 minutes; after the stirring time is up, turn off the stirring and open the overflow outlet of the reaction tank. After the water is drained, re-inject the same proportion of 65°C hot water and stir for the same 30 minutes.

[0028] (2) The quartz sand obtained in step (1) is placed in a centrifuge for dehydration and then transferred into a polytetrafluoroethylene-lined reactor, and a mixed acid of 10% hydrochloric acid and 12% hydrofluoric acid is added; the reactor is set to turn upside down at a slow speed of 90 seconds per revolution for 24 hours, and the volume ratio of the quartz sand and the acid solution after mixing is controlled to be 1:1.

[0029] (3) The acid-washed quartz sand obtained in step (2) is washed with pure water to neutral and adjusted to 25% quartz sand slurry, and then added to a flotation machine for flotation operation. Hydrochloric acid is added to adjust the pH value to 3.0. A collector composed of rosin amine and dodecylamine is added, and the amount of the collector is 150 g / t. After the stirring produces foam, the foam is scraped and floated for 20 min. After the flotation is completed, it is repeated once.

[0030] (4) The quartz sand treated in step (3) is loaded into a drying kettle and heated and dried under vacuum, wherein the drying temperature is 90°C, and the drying time is 9 hours.

[0031] As shown in the data in Table 1, the hydrothermal dissolution time of Example 2 is longer than that of Example 1, the amount of acid washing solution is increased, and an additional flotation treatment is added. The test results show that after the optimization of the process, the total amount of sodium ions and other impurities in the quartz sand is significantly reduced. The key lies in the dynamic regulation of process parameters (hydrothermal reaction intensity, acid washing solution ratio and flotation frequency) according to the characteristics of the ore, and the selective removal of sodium ions is realized. The process provides an innovative solution for the green and efficient purification of medium and low-grade quartz sand.

[0032] Table 1 Impurity content in natural vein quartz before purification and in the product quartz sand in the examples

[0033]

Claims

1. A purification process for improving the sodium ion removal rate of high-purity quartz sand, characterized in that: The following steps are involved: S1. Hydrothermal dissolution: Pour 65°C hot water into a hydrothermal reaction tank, add quartz sand under stirring conditions (150 rpm), maintain a solid-liquid ratio of 1-2:1, and continue stirring for 30 minutes; S2. Pickling: The quartz sand treated in step S1 is centrifuged and dehydrated, transferred to a pickling reactor, and mixed acid (a combination of hydrofluoric acid and hydrochloric acid) is added. The heating and stirring functions of the reactor are turned on to carry out pickling; S3. Flotation: The quartz sand after the pickling in step S2 is rinsed to neutrality, placed in a flotation machine, and the pulp concentration is adjusted to 25-30% for flotation separation.

2. A purification process for improving the sodium ion removal rate of high-purity quartz sand according to claim 1, characterized in that: In step S1, the hydrothermal dissolution treatment may be repeated 2-3 times depending on the original sodium content of the quartz ore.

3. A purification process for improving the sodium ion removal rate of high-purity quartz sand according to claim 1, characterized in that: In step S2, the mixed acid is composed of hydrofluoric acid and hydrochloric acid in a volume ratio of 1-2:1, and is heated to maintain a constant temperature during pickling.

4. A purification process for improving the sodium ion removal rate of high-purity quartz sand according to claim 1, characterized in that: In step S3, hydrochloric acid is used to adjust the pH of the pulp to 2-3 before flotation, mixed amines are selected as collectors, and flotation treatment is performed 2-3 times according to the impurity content.

5. A purification process for improving the sodium ion removal rate of high-purity quartz sand according to claim 1, characterized in that: In step S3, after flotation, the quartz sand is washed with pure water, centrifuged and dehydrated, and dried to obtain high-purity quartz sand.

Images