CN112777600B - A kind of ultra-high-purity quartz and preparation method thereof - Google Patents

Abstract

The invention relates to an ultra-high-purity quartz and a preparation method thereof. The preparation method includes the steps of quartz pretreatment, surface impurity cleaning, surface defect increase, diffusion and segregation of quartz lattice metal impurities, and surface impurity segregation area ablation steps in sequence; the diffusion and segregation of quartz lattice metal impurities is performed by baking. Treatment, the surface impurity segregation zone erosion step is treated with sodium hydroxide. The preparation method does not use hydrofluoric acid, chlorine gas, hydrogen fluoride gas and other substances that are not friendly to the environment or are highly dangerous, and is environmentally friendly; and the waste liquids generated in the hydrochloric acid leaching step and the sodium hydroxide leaching step can be Dramatically reduce the cost of wastewater treatment in the quartz industry.

Description

A kind of ultra-high-purity quartz and preparation method thereof

technical field

The invention relates to the technical field of quartz sand production, in particular to an ultra-high-purity quartz and a preparation method thereof.

Background technique

Ultra-high-purity quartz sand generally refers to quartz sand with SiO ₂ content higher than 99.99%, which has excellent chemical stability, high insulation and pressure resistance, and extremely low volume expansion coefficient. It is an indispensable and important basic material for high-tech industries such as electronic core guides, photoconductive communication materials, and solar cells. Its high-end products are widely used in large-scale integrated circuits, solar cells, optical fibers, lasers, aerospace, military and other industries. The purity of quartz sand and the type and content of impurity elements directly affect the quality of the product.

At present, the purification process of quartz sand mainly includes: manual beneficiation, water washing, coarse crushing, fine crushing, screening, magnetic separation, pickling, flotation, deionized water washing, drying and quartz sand quality inspection. This purification process is complicated, and cannot effectively remove the encapsulated impurities and surface impurities in the quartz sand, and new impurities will be introduced in the production process. In the prior art, there is a report of alkaline washing, such as the publication number is CN102674376A, the name of the invention is "a production method for purification of quartz tailings", and the alkaline washing process is introduced, but the impurity metal elements segregated inside the quartz sand are difficult to be effective. remove.

SUMMARY OF THE INVENTION

In view of this, it is necessary to provide a method for preparing ultra-high-purity quartz, which can effectively remove the impurity metal elements segregated inside the quartz sand.

The invention provides a method for preparing ultra-high-purity quartz, including the steps of quartz pretreatment, surface impurity cleaning, surface defect increase, diffusion segregation of quartz lattice metal impurities, and surface impurity segregation zone erosion in sequence; wherein, The step of increasing surface defects is treated with sodium hydroxide, the step of diffusing and segregating the metal impurities of the quartz lattice is treated with baking, and the step of eroding the surface impurity segregation region is treated with sodium hydroxide.

Specifically, the steps of the quartz pretreatment include crushing, magnetic separation and sieving of the quartz.

Specifically, in the step of cleaning the surface impurities, a hydrochloric acid solution of 1-4 mol/L is used for hot-pressing leaching and cleaning, the liquid-solid ratio of the hydrochloric acid solution and the quartz particles is (6-10) mL:1 g, and the leaching temperature is 150 °C. ℃～250℃, leaching time 1～8h.

Specifically, in the step of increasing the surface defects, 0.2-2 mol/L sodium hydroxide solution is used to erode the quartz particles, the liquid-solid ratio of the sodium hydroxide solution and the quartz particles is (6-10) mL:1 g, and the leaching temperature 150℃～200℃, leaching time 1～8h.

Preferably, in the step of increasing the surface defects, the concentration of the sodium hydroxide solution is 0.6667 mol/L, and the liquid-solid ratio of the sodium hydroxide solution to the quartz particles is 6 mL:1 g.

Specifically, in the step of diffusing and segregating metal impurities in the quartz lattice, the calcination temperature is 600-1400° C., and the calcination time is 5-70 h.

Preferably, in the step of diffusing and segregating metal impurities in the quartz lattice, the calcination temperature is 1000°C.

Specifically, in the denudation step of the surface impurity segregation zone, the concentration of the sodium hydroxide solution used is 0.1-0.5 mol/L, and the liquid-solid ratio of the sodium hydroxide solution to the quartz particles is (2-10) mL:1 g, The leaching temperature is 150℃～200℃, and the leaching time is 1～8h.

Preferably, in the denudation step of the surface impurity segregation zone, the concentration of the sodium hydroxide solution is 0.3799 mol/L, and the liquid-solid ratio of the sodium hydroxide solution to the quartz particles is 6 mL:1 g.

The present invention also provides an ultra-high-purity quartz prepared by the method.

Beneficial effects:

1. The preparation method does not use unfriendly or dangerous substances such as hydrofluoric acid, chlorine gas, hydrogen fluoride gas, etc., and is environmentally friendly; and the waste liquids generated in the hydrochloric acid leaching step and the sodium hydroxide leaching step can be mutually neutralized , which can greatly reduce the cost of quartz industrial wastewater treatment.

2. After this preparation method, the content of Al element in quartz is reduced from 56.5μg/g to 7.8μg/g, which meets the requirement of 8μg/g Al content of IOTA 6 series, and the total content of impurity elements is reduced to 38.2μg/g, Much lower than the 50μg/g required by the high-purity quartz standard.

Description of drawings

FIG. 1 is a flow chart of a method for preparing ultra-high-purity quartz provided in an embodiment of the present invention.

FIG. 2 is a surface topography diagram of a quartz ore provided in an embodiment of the present invention.

Fig. 3 is the surface topography diagram of leaching quartz ore with hydrochloric acid according to the embodiment of the present invention.

Fig. 4 is the surface topography diagram of leaching quartz raw ore with hydrochloric acid+sodium chloride according to the embodiment of the present invention.

5 is a surface topography diagram of leaching quartz ore with hydrochloric acid + hydrofluoric acid according to an embodiment of the present invention.

FIG. 6 is a surface topography diagram of leaching quartz raw ore with sodium hydroxide according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

An embodiment of the present invention provides a method for preparing ultra-high-purity quartz, as shown in FIG. 1 , including quartz pretreatment, surface impurity cleaning, surface defect increase, diffusion and segregation of metal impurities in quartz lattice, and surface impurity segregation, which are sequentially performed. The step of poly-area ablation. Wherein, the step of increasing the surface defects is treated with sodium hydroxide, the step of diffusing and segregating the metal impurities of the quartz lattice is treated with roasting, and the step of eroding the surface impurity segregation area is treated with sodium hydroxide.

When the denuding agent is used to treat the quartz particles, when the quartz particles are gradually eroded and dissolved from the particle surface to the inside, the content C of an impurity element in the quartz after leaching and purification can be expressed as:

In the above formula (1), C ₀ is the initial average content of the element, n ₀ is the initial amount of quartz, ΔC is the average content of the element in the dissolved part of quartz, and Δn is the amount of dissolved quartz.

In the process of denuding and dissolving quartz, if the average content of the element in the dissolved part is greater than the initial average content of quartz, the average content of this element in the quartz will decrease after denudation; if the average content in the dissolved part is less than the initial average content of quartz , the average content of quartz increases after ablation.

Therefore, in the step of removing the surface impurity segregation zone, when a certain impurity element in the quartz particles is segregated, and the element is not on the surface of the quartz or the element has been removed on the surface, the initial average value of the element in the quartz particles The content is the content in the matrix of the quartz particles, the content in the segregation zone is higher than that in the matrix, and the content in the depleted zone is lower than that in the matrix. According to formula (1), when the surface impurity segregation area is eroded, the concentration of the element in the remaining quartz decreases, and reaches the lowest value when the segregation area is eroded. When the loss area is completely eroded and dissolved, the concentration of the element in the remaining part will be the same as that in the matrix again, and then the quartz will continue to be eroded, and the concentration of this element will basically not change.

Using this phenomenon and principle, combined with the process of leaching, roasting and erosion (that is, the steps of increasing the surface concentration of defects, the diffusion and segregation of metal impurities in the quartz lattice, and the erosion of the surface impurity segregation area), the present invention implements The example provides a method for preparing ultra-high purity quartz.

In this method, the quartz is first treated by leaching, and then the surface defects are increased (defects refer to the incomplete area of a certain crystal plane, microscopically refers to missing atoms or unit cells, and macroscopically forms etch pits, eroded seams, etc., as shown in the figure The part circled in 6), and the crystal plane with increased surface defects can facilitate the roasting and promote the diffusion and segregation of impurity elements in the quartz lattice metal impurities. Specifically as shown in Figures 2 to 6, in order to deeply study the characteristics of the reaction between hydrochloric acid, sodium chloride, hydrofluoric acid and sodium hydroxide in the leaching process with quartz, scanning electron microscopy was used to analyze the raw quartz ore, the leaching of quartz by hydrochloric acid, and the leaching of quartz by hydrochloric acid. + Sodium chloride leaching, quartz leaching with hydrochloric acid + hydrofluoric acid, quartz leaching with sodium hydroxide and then leaching with hydrochloric acid. Compared with hydrofluoric acid, the shape of the corrosion pits and corrosion seams formed by sodium hydroxide is more rounded, and it can be seen from the local detail images that the inner walls of the corrosion pits and corrosion seams are also more rounded, indicating that the sodium hydroxide The dissolved amount of quartz on the inner wall of the etch pit and eroded fracture is more than that of hydrofluoric acid. It can be inferred that the selectivity of sodium hydroxide to leaching impurities and inclusions is weaker than that of hydrofluoric acid, and the leaching effect is also worse than that of hydrofluoric acid in the leaching test. . That is to say, using sodium hydroxide for leaching can produce the effect of increasing surface defects.

After calcination, impurity metal elements such as Al element inside the quartz diffuse and segregate to a range of several micrometers on the surface of the quartz to form a local segregation region. Finally, the localized segregation region is precisely dissolved by a denuding agent capable of dissolving quartz, thereby rapidly and significantly reducing the content of various impurity metal elements in the quartz.

This method can extend and diffuse the removal range of impurity metal elements, especially Al elements, from the surface of the general method and several atomic layers near the surface to a region of dozens to tens of microns within the quartz surface, that is, to the inner boundary of the depleted region. , so that the content of impurity metal elements such as Al in the purified quartz is greatly reduced (as shown in Figures 2-6).

Specifically, the quartz pretreatment step includes crushing, magnetic separation and screening of the quartz.

Specifically, in the step of cleaning the surface impurities, a hydrochloric acid solution of 1-4 mol/L is mainly used to perform hot-press leaching and cleaning on the pretreated quartz. In hot-press leaching, the liquid-solid ratio of hydrochloric acid solution and quartz particles is (6-10) mL:1g, the leaching temperature is 150-250°C, and the leaching time is 1-8h.

Specifically, the increase in surface defects refers to an increase in the proportion of an incomplete region of a certain crystal plane. Among them, defect refers to the incomplete area of a certain crystal plane, microscopically refers to missing atoms or unit cells, and macroscopically forms etch pits, eroded seams and other states. The specific steps of increasing surface defects are as follows: 0.2-2mol/L sodium hydroxide solution is used to erode the quartz particles, the liquid-solid ratio of the sodium hydroxide solution to the quartz particles is (6-10) mL:1g, and the leaching temperature is 150-200°C , leaching time 1 ~ 8h. Preferably, in this step, the concentration of the sodium hydroxide solution is 0.6667 mol/L, and the liquid-solid ratio of the sodium hydroxide solution to the quartz particles is 6 mL:1 g.

Specifically, in the step of diffusing and segregating the metal impurities in the quartz lattice, the roasting temperature is 600-1400°C, the roasting time is 5-70h, and the preferred roasting temperature is 1000°C.

Specifically, in the step of eroding the surface impurity segregation zone, the concentration of the sodium hydroxide solution used is 0.1-0.5 mol/L, and the liquid-solid ratio of the sodium hydroxide solution and the quartz particles is (2-10) mL: 1 g, and the leaching The temperature is 150～200℃, and the leaching time is 1～8h. Preferably, the concentration of the sodium hydroxide solution is 0.3799 mol/L, and the liquid-solid ratio of the sodium hydroxide solution to the quartz particles is 6 mL:1 g.

In order to facilitate the description of the specific embodiments of the ultra-high-purity quartz preparation method provided by the present invention, the specific preparation parameters thereof are listed in Table 1 below, so as to evaluate the influence of each parameter on the final result.

Table 1 Summary of conditions for the preparation of ultra-high-purity quartz

In order to evaluate the impurity removal process and impurity removal effect of the above embodiment, the removal effect is listed in Table 2.

The concentration of impurity elements in the original quartz ore and the treated quartz samples was measured by ICP-MS test method. The specific test method is to first weigh 2g of the quartz sample, then add 10ml of hydrofluoric acid to dilute the volume to 100ml to dissolve the quartz sample, use a flat plate to heat to 200°C to evaporate the excess hydrofluoric acid until no white smoke is emitted, and then proceed to the quartz sample. Impurity element concentration measurement. In the original quartz ore, the aluminum (Al) content was 56.5 μg/g, the lithium (Li) content was 12.3 μg/g, the sodium (Na) content was 48.1 μg/g, the potassium (K) content was 22.9 μg/g, and the magnesium (K) content was 22.9 μg/g. (Mg) content was 0.52 μg/g, beryllium (Be) content was 0.02 μg/g, calcium (Ca) content was 68.87 μg/g, iron (Fe) content was 26.3 μg/g, and titanium (Ti) content was 15.2 μg/g μg/g, manganese (Mn) content was 9.62 μg/g chromium (Cr) content was 0.16 μg/g, nickel (Ni) content was 0.35 μg/g and copper (Cu) content was 5.2 μg/g.

The data in Table 2 are the impurity concentrations after the diffusion and segregation step of the metal impurities in the quartz lattice and after the surface impurity segregation zone ablation step, while the data in Comparative Example 8 are the final concentrations of each impurity in the particles. It can be seen from Table 2 that:

1. Quartz lattice substitution impurities are one of the most difficult impurities to separate. Conventional separation methods are powerless to remove Al and other impurity elements in lattice substitution impurities. By adopting the method provided by the present invention, through the steps of increasing surface defects, diffusing and segregating metal impurities in the quartz crystal lattice, and eroding the surface impurity segregation region, a good removal ability (such as Al and other metal elements in the quartz crystal lattice) is produced. Examples 1 to 14 are relative to Comparative Example 8).

2. Compared with Example 3 and Example 4, the diffusion and segregation time of Example 6 is prolonged. After the diffusion and segregation step of quartz lattice metal impurities, the surface impurity segregation region is eroded, and the impurity content removed reaches 10.1 μg/ g, higher than that of Examples 3 and 4, it shows that prolonging the diffusion and segregation time of the metal impurities in the quartz lattice in Example 6 can further strengthen the diffusion and segregation effect of the metal impurities in the quartz lattice, thereby facilitating the leaching and ablation of the subsequent impurities, making The last step can greatly remove impurities.

3. Compared with the examples, the calcination temperature and calcination time of Comparative Examples 1 to 2 are unreasonable, which makes the effect of impurity diffusion and segregation not good. The removal effect is significantly worse than that of the embodiment. This shows that the impurity diffusion segregation method provided by the present invention requires precise control of the calcination time and calcination temperature.

4. Compared with the Examples 3 to 7, the steps of increasing the surface defects are not reasonably controlled, which seriously affects the subsequent diffusion and segregation of metal impurities in the quartz lattice and the treatment effect of the surface impurity segregation zone erosion. The content is still high, which is not conducive to subsequent treatment and significantly reduces the final impurity removal efficiency.

To sum up, the preparation method of ultra-high-purity quartz provided by the present invention avoids the use of unfriendly or dangerous substances such as hydrofluoric acid, chlorine gas, hydrogen fluoride gas, etc., and is relatively friendly to the environment; and the hydrochloric acid leaching step and sodium hydroxide The waste liquid produced in the leaching step can be neutralized with each other, which can greatly reduce the cost of wastewater treatment in the quartz industry. The content of Al element in the final prepared quartz is reduced from 56.5μg/g to 7.8μg/g, which meets the requirement of IOTA 6 series for Al content of 8μg/g, and the total content of impurity elements can be reduced to 38.2μg/g, which is much higher than the high Standard requirement for pure quartz 50μg/g.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention.

Claims (4)

1. a method for preparing ultra-high-purity quartz, is characterized in that, comprises the steps of quartz pretreatment, surface impurity cleaning, surface defect increase, the diffusion segregation of quartz lattice metal impurity and surface impurity segregation zone ablation that carry out successively ; Wherein, the step of increasing the surface defects is treated with sodium hydroxide, the step of diffusing and segregating the metal impurities of the quartz lattice is treated with roasting, and the step of eroding the surface impurity segregation zone is treated with sodium hydroxide, wherein the roasting temperature is 600~1400℃, the roasting time is 5~70h; In the step of cleaning the surface impurities, the hydrochloric acid solution of 1-4 mol/L is used for hot-pressing leaching and cleaning, the liquid-solid ratio of the hydrochloric acid solution and the quartz particles is (6-10) mL: 1 g, and the leaching temperature is 150° C. ~250℃, leaching time 1~8 h; In the step of increasing the surface defects, 0.6667 mol/L sodium hydroxide solution is used to etch the quartz particles, the liquid-solid ratio of the sodium hydroxide solution and the quartz particles is 6 mL:1 g, the leaching temperature is 150 ℃ ~ 200 ℃, and the leaching temperature is 150 ℃ ~ 200 ℃. Time 1~8 h; In the step of erosion of the surface impurity segregation zone, the concentration of the sodium hydroxide solution used is 0.1~0.5 mol/L, and the liquid-solid ratio of the sodium hydroxide solution to the quartz particles is (2~10) mL: 1 g, and the leaching The temperature is 150℃~200℃, and the leaching time is 1~8 h. 2 . The method according to claim 1 , wherein the quartz pretreatment step comprises crushing, magnetic separation and sieving of the quartz. 3 . 3 . The method according to claim 1 , wherein, in the step of diffusing and segregating metal impurities in the quartz lattice, the firing temperature is 1000° C. 4 . 4. method according to claim 1, is characterized in that, in the step of described surface impurity segregation zone erosion, sodium hydroxide solution concentration is 0.3799 mol/L, and the liquid-solid ratio of sodium hydroxide solution and quartz particle is 6 mL: 1 g.

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