Method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz

Abstract

The present invention provides a method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz. The method comprises the following steps: After sorting the quartz raw ore, quartz concentrate is obtained. The quartz concentrate is subjected to heating acid leaching, washing, and drying to obtain primary quartz sand; The primary quartz sand is calcined, quenched with normal-temperature water, and dried to obtain intermediate minerals; The intermediate minerals are added to an oxidizing or reducing system acid, first subjected to ultrasonic acid leaching at normal temperature, and then subjected to heating acid leaching to obtain a leaching solution and leaching residues; The leaching residues are ultrasonically washed and dried to obtain 4N7 grade high-purity quartz sand. The method of the present invention can significantly reduce the content of impurity elements in muscovite-type granite quartz, and obtain a high-purity quartz sand product with SiO₂ ≥ 99.997%. The preparation method has simple process, low energy consumption, and is easy to operate. This method effectively solves the problem of difficult removal of fine-grained muscovite in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of high-purity quartz sand preparation, and particularly to a method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz. Background Art

[0002] High-purity quartz is widely used in fields such as semiconductor chips, optical fibers, photovoltaics, optics, and electric light sources, and is a key basic material for strategic emerging industries such as new-generation information technology, new energy, and energy conservation and environmental protection. Due to advantages such as large quartz particles and few gas-liquid inclusions, high-purity quartz mainly comes from granite and pegmatite, and a small amount comes from hydrothermal veins and quartzite. Generally, granitic pegmatite contains more muscovite, and most of the muscovite can be removed by gravity separation and flotation. However, high-end high-purity quartz has extremely high requirements for quartz purity. How to remove fine-grained muscovite to the greatest extent has become the key to the purification of high-purity quartz from granitic pegmatite.

[0003] At present, there are many purification methods for high-purity quartz sand. Patent CN 111874914 A adopts the process flow of "grinding-flotation-roasting and water quenching-thermal pressure acid leaching". This method has a high leaching temperature, a large leaching pressure, difficult operation, and prepares 4N grade high-purity quartz sand. Patent CN 112777600 A prepares 4N6 grade high-purity quartz sand by using the process flow of "quartz pretreatment-surface impurity cleaning-increase of surface impurity defects-diffusion and segregation of metal impurities in quartz lattice-stripping of surface impurity segregation zones". This method focuses on the study of the lattice and does not study the fine-grained impurity minerals existing in high-purity quartz. As a result, although the impurity element Al is reduced to 7.8 μg / g, the contents of other elements such as K and Na are high, and Na is even as high as more than 10 μg / g. High-purity quartz has extremely high requirements for alkali metals, and the prepared 4N6 grade high-purity quartz sand cannot meet the application standards of related products. Therefore, it is of great economic benefit and practical significance to develop a production method with simple process, low energy consumption, easy operation, which can effectively remove fine-grained muscovite and prepare high-purity quartz sand with SiO2 purity ≥ 99.997%. Summary of the Invention

[0004] The present invention provides a method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz. This method can significantly reduce the content of impurity elements in muscovite-type granite quartz and obtain high-purity quartz sand products with SiO2 ≥ 99.997%. The preparation method has a simple process, low energy consumption, and easy operation, and effectively solves the problem of difficult removal of fine-grained muscovite in the prior art.

[0005] The technical solution of the present invention is realized as follows: A method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz, comprising the following steps:

[0006] (1) The quartz raw ore is sorted to obtain quartz concentrate, and the quartz concentrate is subjected to heating acid leaching, washing, and drying to obtain primary quartz sand;

[0007] (2) The primary quartz sand is calcined, quenched with normal-temperature water, and dried to obtain intermediate minerals;

[0008] (3) The intermediate minerals are added to an oxidation or reduction system acid, first subjected to ultrasonic normal-temperature acid leaching, and then heated acid leaching to obtain a leaching solution and leaching residues;

[0009] (4) The leaching residues are ultrasonically washed and dried to obtain 4N7 grade high-purity quartz sand.

[0010] Further, in step (2), the calcination temperature is 600 - 700 °C, heating up with the furnace, the heat preservation time is ≥1 h, and immediately quenched with normal-temperature water after calcination.

[0011] Further, in step (1), the acid leaching uses a mixed acid, the mixed acid includes HCl and HF, the concentration of HCl in the mixed acid is 2 - 4 mol / L, the concentration of HF is 0.5 - 2 mol / L, at the same time the molar concentration ratio of HCl and HF is 2:1 - 5:1, and the liquid-solid ratio of the mixed acid and quartz concentrate is ≥3 ml:1 g.

[0012] Further, in step (3), the oxidation or reduction system acid uses a mixed acid, the mixed acid includes HCl and HF, and one of HNO3 and H2C2O4, where the concentration of HNO3 or H2C2O4 is 0.5 - 1 mol / L, the concentration of HCl is 2 - 4 mol / L, the concentration of HF is 0.5 - 2 mol / L, at the same time the molar concentration sum of HNO3 or H2C2O4 and HCl and the molar concentration ratio of HF is 2:1 - 5:1, and the liquid-solid ratio of the mixed acid and quartz concentrate is ≥3 ml:1 g.

[0013] Further, in step (3), the ultrasonic power is 1000 - 1200 W, the ultrasonic mixed acid leaching time is 0.5 - 1.5 h, and the leaching temperature is room temperature.

[0014] Further, in step (1), the heating acid leaching temperature is 60 - 95 °C, and the leaching time is 4 - 8 h.

[0015] Further, in step (3), the heating acid leaching temperature is 60 - 95 °C, and the leaching time is 4 - 8 h.

[0016] Further, in step (4), the ultrasonic washing uses ultrapure water and is washed until Cl cannot be detected - 。

[0017] Further, in step (1), the content of SiO2 in the quartz concentrate is ≥ 99.9 wt%, and the particle size is 0.10 - 0.25 mm.

[0018] Further, the content of SiO2 in the 4N7 grade high-purity quartz sand is ≥ 99.997 wt%.

[0019] The content of muscovite in the muscovite-type granite quartz is 5% - 15%.

[0020] Advantages of the present invention:

[0021] (1) In the present invention, acid leaching is carried out first and then calcination is carried out, and the calcination temperature is controlled at 600 - 700 °C. On the one hand, heating acid leaching is adopted to remove impurity minerals to the greatest extent, avoiding the entry of impurity elements such as Al and Fe into the crystal lattice during high-temperature calcination when the impurity content is relatively high, thus affecting the removal of impurity elements. On the other hand, the calcination temperature is controlled at 600 - 700 °C to avoid too high a calcination temperature, as the formation of new phases will cause the impurities in the high-purity quartz to be difficult to effectively remove. For example, in the temperature range of 700 °C - 1000 °C, muscovite will gradually remove hydroxyl groups, the atomic positions in the unit cell will change, resulting in the separation of lamellae, forming phases such as feldspar and quartz, making it difficult to remove them; in the range of 1000 - 1150 °C, the crystal structure of muscovite is completely destroyed and reconstructed into a melt mixture of mullite, aluminum oxide and a large amount of amorphous silicon oxide compounds.

[0022] (2) Quartz will undergo polymorphic transformation under high-temperature calcination. Under normal pressure conditions, when the temperature is raised to around 573 °C, the bond angle of the Si-O bond in quartz will undergo a displacement transformation, and α-quartz will rapidly transform into β-quartz; when the temperature is further raised to 870 °C, β-quartz will gradually transform into β-tridymite, and this transformation has a greater change in the crystal lattice structure. When quartz passes through these two polymorphic transformation points and is subjected to high-temperature calcination - rapid water quenching, a large number of cracks will be generated. At present, most experimental research results use the second polymorphic transformation temperature of quartz to set the high-temperature roasting temperature at 900 °C. Because the crystal lattice structure changes more, it is conducive to the generation of a large number of cracks. In the present invention, after heating acid leaching, the first polymorphic transformation temperature is used for calcination - water quenching at 600 - 700 °C. While the lamellar structure of muscovite is not destroyed, the impurities in the inclusions and fissures are exposed on the particle surface, making it easy to remove them by subsequent acid leaching.

[0023] (3) After the quartz raw material is calcined - water quenched, in a mixed system of HCl and HF, adding HNO3 forms an oxidation system, which can be coupled with HCl, increasing the strong acidity and strong oxidizing property of the mixed system; adding H2C2O4 forms a reduction system, which can produce a complexing effect and promote the progress of its chemical reaction. Both the oxidation system and the reduction system can greatly improve the leaching efficiency and significantly reduce the content of impurity elements such as Al, Ca, and Na in the quartz concentrate.

[0024] (4) Before high-temperature leaching, ultrasonic-assisted acid leaching is carried out at room temperature and pressure. The cavitation effect of ultrasonic waves in the liquid is used to accelerate the chemical reaction rate between the quartz concentrate and the acid, shorten the reaction time between the quartz and the acid solution, improve the acid leaching effect and capacity, and reduce the pollution caused by the wear of the mixer.

[0025] (5) Compared with other chemical purification methods at room temperature and pressure, the method of the present invention has a lower calcination temperature and less energy consumption; the amount of leaching acid required is small, and the leaching time is short. Compared with hot-press chemical purification, the process is simple, safe, easy to operate, and has low energy consumption. Compared with other chemical purification methods, the method of the present invention has a higher removal rate of metal elements such as Al, Ca, and Na. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 The following is a process flow chart for preparing 4N7 grade high-purity quartz sand according to the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, a method for preparing 4N7 grade high-purity quartz sand from muscovite granite quartz comprises the following steps:

[0030] (1) Quartz concentrate is obtained after grinding, classification, gravity separation, magnetic separation and flotation of quartz ore. The SiO2 content of the quartz concentrate is ≥99.9wt%, the particle size is 0.10-0.25mm, and the quartz ore is muscovite-type granite quartz with a muscovite content of 5%-15%. The quartz concentrate is heated and acid-leached. After acid leaching, the leached product is repeatedly washed until the washing water is free of Cl- by AgNO3 detection, and then placed in a 105°C oven for drying to obtain primary quartz sand.

[0031] (2) After calcining the primary quartz sand, it is immediately quenched in water at room temperature and then dried in an oven at 105°C to obtain the intermediate mineral;

[0032] (3) adding the intermediate mineral to an oxidizing or reducing acid system, first performing ultrasonic acid leaching at room temperature, and then performing heated acid leaching to obtain a leachate and a leach residue;

[0033] (4) The leached residue is ultrasonically washed with ultrapure water, the ultrasonic power is 500-1200W, the ultrasonic washing frequency is 1-3 times, each time is 10-30 minutes, and the washing water is washed until there is no Cl in the washing water by AgNO3 detection. - , placed in an oven at 105℃ and dried to obtain 4N7 grade high-purity quartz sand.

[0034] In step (2), the calcination temperature is 600-700°C, and the temperature is raised with the furnace, and the holding time is ≥1 hour. After calcination, water quenching is immediately performed at room temperature. The advantage of selecting this temperature range is that the layered structure of the muscovite is not destroyed, while the impurities in the inclusions and cracks are exposed to the surface of the particles, making them easy to remove by acid leaching. Furthermore, the calcination temperature can be 600°C, 625°C, 650°C, 675°C and 700°C. Furthermore, the calcination time can be 1 hour, 2 hours, 3 hours or 4 hours.

[0035] In step (1), acid leaching adopts mixed acid, and the mixed acid comprises HCl and HF, the concentration of HCl in the mixed acid is 2-4 mol / L, the concentration of HF is 0.5-2 mol / L, and the molar concentration ratio of HCl to HF is 2:1-5:1. The liquid-solid ratio of the mixed acid to the quartz concentrate is ≥3 ml:1 g.

[0036] In step (3), the oxidation or reduction system acid adopts a mixed acid, which includes HCl and HF, and one of HNO3 and H2C2O4, wherein the concentration of HNO3 or H2C2O4 is 0.5-1mol / L, the concentration of HCl is 2-4mol / L, and the concentration of HF is 0.5-2mol / L. At the same time, the molar concentration ratio of the sum of the molar concentrations of HNO3 or H2C2O4 and HCl to the molar concentration ratio of HF is 2:1-5:1, and the liquid-solid ratio of the mixed acid to the quartz concentrate is ≥3ml:1g. Further, the concentration of the HNO3 can be 0.5mol / L, 0.6mol / L, 0.8mol / L, 1mol / L, etc. Further, the concentration of the H2C2O4 can be 0.5mol / L, 0.6mol / L, 0.8mol / L, 1mol / L, etc. Furthermore, the concentration of HF may be 0.5 mol / L, 0.1 mol / L, 1.5 mol / L, 2 mol / L, etc. Furthermore, the concentration of HCl may be 2 mol / L, 3 mol / L, 4 mol / L, etc.

[0037] In step (3), the ultrasonic acid leaching at room temperature is carried out under normal temperature and pressure, the ultrasonic power is 1000 - 1200 W, and the ultrasonic mixed acid leaching time is 0.5 - 1.5 h. Further, the ultrasonic power can be 1000 W, 1100 W, 1200 W, etc. Further, the ultrasonic mixed acid leaching time can be 0.5 h, 1 h, 1.5 h, etc.

[0038] In steps (1) and (3), the temperature of the heating acid leaching is 60 - 95 °C, and the leaching time is 4 - 8 h; further, the leaching temperature can be 60 °C, 70 °C, 80 °C, 90 °C, etc. Further, the leaching time can be 4 h, 5 h, 6 h, 7 h, 8 h, etc.

[0039] In order to make the purpose and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] The quartz raw material used in the embodiment of the present invention is quartz concentrate with a SiO2 content ≥ 99.9% after physical separation, and the original ore type is high-purity quartz of granite type rich in muscovite. The content of each impurity element of a certain quartz concentrate is shown in Table 1.

[0041] Table 1 Impurity elements and quartz content of quartz concentrate

[0042]

[0043] Table 2 Summary of preparation implementation conditions for 4N7 grade high-purity quartz sand

[0044]

[0045]

[0046]

[0047] Table 3 Impurity elements and quartz content of high-purity quartz

[0048]

[0049] As can be seen from Table 3, Examples 1 - 5 can all prepare 4N7 grade high-purity quartz sand.

[0050] Before carrying out step (2), Comparative Examples 1-2 did not carry out step (1). The calcination temperature of the comparative examples was 950°C. At this temperature, muscovite would gradually remove hydroxyl groups, and the positions of atoms in the unit cell would change, resulting in the separation of lamellae and the formation of new substances that were difficult to remove, leading to a decrease in the purity of the prepared high-purity quartz sand. The calcination temperature of Comparative Example 2 was 650°C. Although at this temperature, the influence on the crystal structure, optical properties, surface morphology, etc. of muscovite was small, and the purity of the quartz sand was higher than that of Comparative Example 1, when the impurity content was high, high-temperature calcination was likely to cause impurity elements to enter the crystal lattice, thus affecting the removal of impurity elements. Therefore, heating and acid leaching first and then calcining, and controlling the calcination temperature at 600-700°C was beneficial to improving the effect of impurity removal.

[0051] The calcination temperature of Comparative Example 3 was 950°C. Although most of the impurities were removed through step (1), there were still some mica minerals in the form of fine particles or inclusions. After high-temperature calcination at 950°C, it led to the separation of lamellae and the formation of new substances that were difficult to remove. At the same time, the energy consumption of calcination at 950°C was higher than that at 600°C, which was not conducive to the specific operation implementation and economic benefits.

[0052] In Comparative Example 4, ultrasonic leaching at room temperature was not used in step (3), and high-temperature mixed acid leaching was directly carried out. The preparation effect of high-purity quartz sand was not as good as that of Examples 1-5, indicating that the cavitation effect of ultrasonic waves promoted leaching. In Comparative Example 5, an oxidation / reduction system was not used for mixed acid leaching in step (3), and the preparation effect of high-purity quartz sand was not as good as that of Examples 1-5, indicating that adding an oxidizing / reducing agent could significantly promote the removal of impurity elements.

[0053] The present invention provides a method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz. The SiO2 content of the prepared 4N grade high-purity quartz sand reached more than 99.997 wt%. The prepared high-purity quartz sand could meet the industry's requirements for high-purity quartz sand. The preparation method had a simple process, low energy consumption, and was easy to operate. This method effectively solved the problem of difficult removal of fine-grained muscovite in the prior art.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz, characterized in that: It includes the following steps: (1) The quartz concentrate is obtained after the separation of the quartz raw ore. The quartz concentrate is subjected to heating acid leaching, washing, and drying to obtain primary quartz sand; (2) The primary quartz sand is calcined, quenched with normal-temperature water, and dried to obtain intermediate minerals; (3) The intermediate minerals are added to the oxidation or reduction system acid. First, ultrasonic acid leaching is carried out at normal temperature, and then heating acid leaching is carried out to obtain leaching solution and leaching residue; (4) The leaching residue is ultrasonically washed and dried to obtain 4N7 grade high-purity quartz sand; In step (1), the content of SiO2 in the quartz concentrate is ≥99.9 wt%, and the particle size is 0.10 - 0.25 mm; The content of muscovite in the muscovite-type granite quartz raw ore is 5% - 15%; In step (2), the calcination temperature is 600 - 700 °C, heating up with the furnace, the heat preservation time is ≥1 h, and immediately quenched with normal-temperature water after calcination; In step (1), mixed acid is used for acid leaching. The mixed acid includes HCl and HF. The concentration of HCl in the mixed acid is 2 - 4 mol / L, the concentration of HF is 0.5 - 2 mol / L. At the same time, the molar concentration ratio of HCl and HF is 2:1 - 5:1, and the liquid-solid ratio of the mixed acid and the quartz concentrate is ≥3 ml:1 g; In step (3), the oxidation or reduction system acid uses mixed acid. The mixed acid includes HCl and HF, and one of HNO3 and H2C2O4. The concentration of HNO3 or H2C2O4 is 0.5 - 1 mol / L, the concentration of HCl is 2 - 4 mol / L, the concentration of HF is 0.5 - 2 mol / L. At the same time, the molar concentration ratio of the sum of HNO3 or H2C2O4 and HCl to the molar concentration of HF is 2:1 - 5:1, and the liquid-solid ratio of the mixed acid and the quartz concentrate is ≥3 ml:1 g.

2. The method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz according to claim 1, wherein: In step (3), the ultrasonic power is 1000 - 1200 W, the ultrasonic mixed acid leaching time is 0.5 - 1.5 h, and the leaching temperature is room temperature.

3. A method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz according to claim 1, characterized in that: In step (1), the temperature of heating acid leaching is 60 - 95 °C, and the leaching time is 4 - 8 h.

4. A method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz according to claim 1, characterized in that: In step (3), the temperature of heating acid leaching is 60 - 95 °C, and the leaching time is 4 - 8 h.

5. A method for preparing 4N7 grade high-purity quartz sand from muscovite granite quartz according to claim 1, characterized in that: In step (4), the ultrasonic washing is carried out with ultrapure water until Cl cannot be detected. - .

6. The method for preparing 4N7 grade high-purity quartz sand from muscovite-type granite quartz according to claim 1, characterized in that: The content of SiO2 in the 4N7 grade high-purity quartz sand is ≥99.997 wt%.

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