A method for removing mineral impurities from a quartz lattice structure

Abstract

The present application relates to a kind of removal methods of mineral impurities in quartz lattice structure, belong to the technical field of non-metallic element compound.The removal method of mineral impurities in quartz lattice structure of the present application, comprising the following steps: S1, pre-activation treatment: quartz crystal is placed in inert gas atmosphere and is carried out first heat treatment;S2, mid-temperature chlorination treatment: after the quartz crystal treated in step S1 is placed in the mixed gas atmosphere including inert gas and hydrogen chloride gas and is carried out second heat treatment;S3, high-temperature chlorination treatment: after the quartz crystal treated in step S2 is placed in the mixed gas atmosphere of inert gas, hydrogen chloride gas and chlorine and is carried out third heat treatment.The method can effectively improve the removal rate of mineral impurities in quartz lattice structure, and then obtain high-purity quartz crystal.

Description

Technical Field

[0001] This invention relates to the field of non-metallic element compound technology, and in particular to a method for removing mineral impurities within a quartz lattice structure. Background Technology

[0002] Quartz, whose main chemical component is SiO2, is widely used as an important industrial raw material in photovoltaics, semiconductors, fiber optic communications, optical glass, and high-end building materials. However, naturally formed quartz contains certain amounts of metallic impurities (such as Li, Na, Al, K, Ca, Mg, etc.), making it difficult to meet the purity and stability requirements of these applications. Currently, quartz purification technologies can be divided into physical and chemical methods. Physical methods mainly include crushing, washing, scrubbing, magnetic separation, and flotation, while chemical methods mainly include acid leaching and heat treatment. Among these, chlorination roasting in heat treatment is a widely used technique for removing impurities from quartz. Chlorination roasting involves introducing chlorine-based gases (such as HCl or Cl2) during quartz roasting, causing metallic and non-metallic impurities in the quartz to be converted into gaseous or condensed chlorides, thus separating them from the original mineral system and improving the purity of the quartz.

[0003] While chlorination roasting offers unique advantages for removing lattice-substitute impurities and micron-sized inclusions, the impurity removal rate of this method has not yet reached an ideal level. To improve the impurity removal rate, existing technologies have primarily focused on the following improvements: 1) Increasing the reaction temperature or extending the reaction time, but this leads to a significant increase in energy consumption and a higher risk of quartz phase transformation (such as cristobalite conversion); 2) Increasing the chlorine concentration or partial pressure, while partially enhancing the reaction driving force, exacerbates equipment corrosion, increases the burden of exhaust gas treatment and raw material costs, and may cause excessive erosion of the quartz matrix; 3) Introducing catalysts or mineralizers, such as attempting to add small amounts of fluorides or carbonates to promote impurity migration, but this may introduce new sources of contamination and affect the high-temperature stability of quartz. Therefore, a method that can effectively improve the removal rate of mineral impurities within the quartz lattice structure is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for removing mineral impurities within a quartz lattice structure.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for removing mineral impurities within a quartz crystal lattice structure, comprising the following steps: S1. Pre-activation treatment: The quartz crystal is placed in an inert gas atmosphere for the first heat treatment; S2, Medium-temperature chlorination treatment: The quartz crystal treated in step S1 is placed in a mixed gas atmosphere containing inert gas and hydrogen chloride gas (HCl) for a second heat treatment. S3, High-temperature chlorination treatment: The quartz crystal treated in step S2 is placed in a mixed gas atmosphere of inert gas, hydrogen chloride gas (HCl) and chlorine gas (Cl2) for a third heat treatment; The temperature of the first heat treatment is T1, the temperature of the second heat treatment is T2, and the temperature of the third heat treatment is T3, and the following conditions must be met: T1 < T2 < T3, 800℃ < T2 < 1050℃, T3 ≥ 1050℃; The volume ratio of the inert gas to the hydrogen chloride gas in step S2 is (70~80):(20~30). The volume ratio of the inert gas, hydrogen chloride gas and chlorine gas in step S3 is (5~40):(50~90):(5~15).

[0006] To address the mineral impurities embedded within the quartz lattice, this invention first employs a pre-activation treatment to disrupt the weak bonding structures on the quartz crystal surface and at the lattice edges, creating reaction sites for subsequent chlorination reactions. Then, it utilizes segmented chlorination treatments of medium-temperature and high-temperature chlorination, combined with specific chlorination temperatures and chlorinating agents, to achieve targeted chlorination of moderately volatile and non-volatile salt impurities. This allows the chloride impurities generated in the reaction to detach from the quartz system, thereby achieving deep removal of mineral impurities both inside and outside the quartz lattice, resulting in high-purity quartz crystals.

[0007] The pre-activation treatment uses an inert gas atmosphere, which provides a heat transfer medium for the quartz crystal while effectively isolating it from oxygen, moisture, or other active substances in the environment. This prevents oxidation, impurity incorporation, or surface damage during the high-temperature pre-activation process. The inert gas atmospheres used in the medium-temperature and high-temperature chlorination treatments effectively prevent the quartz crystal from being oxidized at high temperatures and also inhibit the indiscriminate reaction of the chlorinating agent, thereby reducing the formation of harmful byproducts and promoting the improvement of quartz crystal purity.

[0008] By adjusting the temperature gradient (T1 < T2 < T3) to create a gradient heating mode, the "physical activation" and "chemical chlorination" processes are precisely linked in time and space. This maximizes the removal of mineral impurities while ensuring the integrity of the quartz crystal structure. The lower T1 provides adequate thermal excitation, creating microscopic cracks within the quartz crystal and releasing volatiles, thus reserving a "reaction channel" for the chlorinating agent to enter during the medium-temperature chlorination stage. It also effectively inhibits the diffusion of impurity ions into the deeper layers of the crystal lattice. The higher T2 ensures the reactivity of the chlorinating agent, promoting the chlorination reaction on the surface of the quartz crystal and in shallow impurities. The higher T3 effectively drives the outward diffusion of metal ions embedded deep within the quartz crystal lattice and promotes the vaporization and escape of high-boiling-point chlorination products.

[0009] If T1 is greater than or equal to T2, impurity ions will undergo deep thermal migration before being captured by the chlorinating agent, significantly increasing the difficulty of subsequent impurity removal. If T2 is too low, the activity of the chlorinating agent will be limited, and the chlorination reaction kinetics of the quartz surface and shallow impurities will be insufficient, resulting in incomplete initial impurity removal. If T2 is too high, it will easily cause local sintering on the surface of quartz particles, which will block the channels for the discharge of reaction products, thus producing "inclusion defects". If T3 is too low, it will not be enough to drive the metal ions embedded deep in the quartz lattice to diffuse outward, and the high-boiling-point chlorination products will not be able to fully vaporize and escape, resulting in the metal element content of the final product exceeding the standard, making it difficult to meet the application requirements of high-purity quartz.

[0010] The gas atmosphere for intermediate-temperature chlorination is a mixture of inert gas and hydrogen chloride gas. When the volume percentage of hydrogen chloride gas is too low, there will be insufficient effective reactive groups in the gas phase, the chlorination reaction rate will drop significantly, and some difficult-to-react impurities will not be fully converted, resulting in more residual impurities in the quartz crystal lattice. On the other hand, when the volume percentage of hydrogen chloride gas is too high, excess hydrogen chloride will be adsorbed and remain on the surface of the quartz crystal, and may compete with chlorine for reaction sites during the high-temperature chlorination stage, inhibiting the chlorination effect of chlorine on stubborn impurities and indirectly reducing the overall impurity removal efficiency.

[0011] Meanwhile, although the corrosive effect of hydrogen chloride on SiO2 is weaker in the medium-temperature chlorination stage than in the high-temperature chlorination stage, when the volume ratio of hydrogen chloride gas is too high, it will still react weakly with the surface of quartz crystal and generate non-volatile substances such as SiCl4, which will cause etching damage such as pits and craters on the surface of quartz crystal particles, resulting in uneven particle size distribution and increased surface roughness of quartz crystal.

[0012] Metallic impurities (such as Fe and Ti) within the quartz lattice typically exist in the form of oxides or silicates. Using hydrogen chloride alone as a chlorinating agent has limited ability to "open up" the deep-seated, bound impurities within the quartz lattice. However, combining hydrogen chloride with chlorine gas as a chlorinating agent and conducting the chlorination reaction at temperatures above 1050°C can increase the oxidation-chlorination potential of the system, promoting the conversion of difficult-to-react impurities into volatile chlorides (such as FeCl3). This effectively removes difficult-to-react metallic impurities within the quartz lattice, thereby improving the purity of the quartz crystal.

[0013] In some implementations, T2 may be, but is not limited to, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, or 1040°C, or fall within the range of any two of the above values.

[0014] In some implementations, T3 may be, but is not limited to, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, 1100°C, 1110°C, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, 1200°C, 1210°C, 1220°C, 1230°C, 1240°C, or 1250°C, or fall within the range of any two of the above values.

[0015] In some embodiments, the inert gas in the mixed gas atmosphere in step S2, by volume, may be, but is not limited to, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 or 80 parts, or fall within the range of any two of the above values.

[0016] In some embodiments, the hydrogen chloride gas in the mixed gas atmosphere in step S2, by volume, may be, but is not limited to, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, or 30 parts, or fall within the range of any two of the above values.

[0017] In some embodiments, the inert gas in the mixed gas atmosphere described in step S3, by volume, may be, but is not limited to, 5 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, or 40 parts, or fall within the range of any two of the above values.

[0018] In some embodiments, the hydrogen chloride gas in the mixed gas atmosphere in step S3, by volume, may be, but is not limited to, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, or 90 parts, or fall within the range of any two of the above values.

[0019] In some embodiments, the chlorine gas in the mixed gas atmosphere in step S3, by volume, may be, but is not limited to, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts, or falls within the range of any two of the above values.

[0020] In some embodiments, the inert gas in step S1, the inert gas in step S2, and the inert gas in step S3 are each independently selected from at least one of nitrogen (N2), argon (Ar), helium (He), and neon (Ne). Considering both process cost and material stability, nitrogen is preferred as the inert gas.

[0021] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure described in this invention, 200℃≤T2-T1≤300℃.

[0022] In some implementations, T2-T1 may be, but is not limited to, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C, or 300°C, or fall within the range of any two of the above values.

[0023] By adjusting T2-T1 within the aforementioned range, it is more effective to remove difficult-to-react metallic impurities within the quartz lattice, thereby improving the purity of the quartz crystal.

[0024] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure described in this invention, 100℃≤T3-T2≤200℃.

[0025] In some implementations, T3-T2 may be, but is not limited to, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, or 200°C, or fall within the range of any two of the above values.

[0026] By adjusting T3-T2 within the aforementioned range, it is more effective to remove difficult-to-react metallic impurities within the quartz lattice, thereby improving the purity of the quartz crystal.

[0027] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure of the present invention, T1 is 550°C to 800°C, preferably 650°C to 750°C, and more preferably 700°C.

[0028] In some embodiments, the temperature (T1) of the first heat treatment may be, but is not limited to, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, or 800°C, or fall within the range of any two of the above values.

[0029] By controlling the temperature (T1) of the first heat treatment within the above range, sufficient thermal stress can be provided to open the micro-channels inside the quartz crystal to promote the penetration of chlorinating agent in subsequent treatment and improve the impurity removal efficiency. It can also effectively avoid the thermal closure effect of the micropores of the quartz crystal, which would trap impurities inside the crystal lattice and prevent them from being discharged. Furthermore, it can suppress the deep thermal diffusion of impurity ions and the unexpected transformation of the crystal phase, thereby better improving the structural integrity and purity of the quartz crystal.

[0030] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure described in this invention, T2 is 850°C to 1000°C, preferably 900°C to 980°C, and more preferably 950°C.

[0031] By controlling the temperature (T2) of the second heat treatment within the above range, not only can the activity of the chlorinating agent be guaranteed to promote the chlorination reaction and improve the initial impurity removal effect, but the smooth discharge of the reaction products can also be guaranteed to avoid the formation of "inclusion defects" in the quartz crystals.

[0032] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure of the present invention, T3 is 1050°C to 1250°C, preferably 1050°C to 1200°C, more preferably 1080°C to 1150°C, and even more preferably 1100°C.

[0033] By controlling the temperature (T3) of the third heat treatment within the above range, it is possible not only to better drive the outward diffusion of metal ions embedded deep in the quartz lattice and the full vaporization and escape of the chlorination products produced by the reaction, but also to effectively prevent the uncontrolled phase transformation of the quartz crystal to form cristobalite induced by high temperature, thus avoiding the formation of microcracks or pulverization of the quartz crystal structure due to thermal stress imbalance. At the same time, it is also possible to prevent the local softening of the surface of the quartz crystal particles and the closure of the micropore channels, thereby better removing residual impurities in the quartz crystal.

[0034] As a preferred embodiment of the method for removing mineral impurities in the quartz lattice structure of the present invention, the mixed gas atmosphere in step S2 also contains chlorine gas, and the volume ratio of the inert gas, hydrogen chloride gas and chlorine gas is (70~80):(20~30):(0.5~5).

[0035] In some embodiments, the chlorine gas in the mixed gas atmosphere in step S2, by volume, may be, but is not limited to, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, or 5 parts, or fall within the range of any two of the above values.

[0036] Introducing a small amount of chlorine gas into the atmosphere during the intermediate-temperature chlorination process can utilize the strong oxidizing properties of chlorine to accelerate the conversion of metallic impurities in the quartz lattice into high-valence chlorides, thereby better improving the rate and depth of impurity removal during the intermediate-temperature chlorination process.

[0037] Studies have found that the amount of chlorine introduced should be strictly controlled. If the concentration of chlorine is too high, it will cause excessive chemical erosion of the quartz matrix, resulting in inaccurate particle size and micropore defects on the surface. At the same time, excessive chlorine will accelerate the corrosion and wear of production equipment and increase the difficulty of treating residual toxic gases in the exhaust gas.

[0038] In addition, chlorine can effectively reduce the chemical water potential of the reaction environment and promote the removal of hydroxyl groups from the quartz surface.

[0039] The hydroxyl content can be measured using FT-IR (Fourier Transform Infrared Spectroscopy) at 3500 cm⁻¹. -1 Up to 3700cm -1 The absorption peaks of the band were determined, and the hydroxyl content was calculated based on the Beer-Lambert law.

[0040] As a preferred embodiment of the method for removing mineral impurities in the quartz lattice structure of the present invention, the volume ratio of the inert gas, hydrogen chloride gas and chlorine gas in step S3 is (5~25):(70~90):(5~15), preferably (10~20):(70~80):(8~12), and more preferably 15:75:10.

[0041] By adjusting the volume ratio of inert gas, hydrogen chloride gas and chlorine gas in step S3 to within the above range, it is more conducive to the deep removal of mineral impurities inside and outside the quartz lattice, thereby better improving the purity of the quartz crystal.

[0042] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure described in this invention, the duration of the first heat treatment is 10 min to 35 min, preferably 15 min to 25 min, and more preferably 20 min.

[0043] In some embodiments, the time for the first heat treatment may be, but is not limited to, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min, or 35 min, or fall within the range of any two of the above values.

[0044] By controlling the time of the first heat treatment within the above range, on the one hand, the quartz crystal can be heated evenly, and the anisotropic thermal stress inside can be fully accumulated, which can better promote the rupture of inclusions, reduce the residue of volatiles, and thus provide a large number of permeation channels for the subsequent chlorination reaction; on the other hand, it can also effectively avoid lattice distortion and physical damage to the particle surface of the quartz crystal, thereby maintaining better structural stability.

[0045] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure described in this invention, the second heat treatment time is 30 to 50 minutes, preferably 35 to 45 minutes, and more preferably 40 minutes.

[0046] In some embodiments, the time for the second heat treatment may be, but is not limited to, 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, 41 min, 42 min, 43 min, 44 min, 45 min, 46 min, 47 min, 48 min, 49 min, or 50 min, or fall within the range of any two of the above values.

[0047] By controlling the time of the second heat treatment within the above range, the temperature of the second heat treatment can be better matched, which not only promotes the chlorination reaction to proceed fully, but also avoids the growth of quartz crystal grains or the generation of lattice defects.

[0048] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure described in this invention, the time for the third heat treatment is 30 min to 65 min, preferably 35 min to 50 min, further preferably 35 min to 45 min, and more preferably 40 min.

[0049] In some embodiments, the time for the third heat treatment may be, but is not limited to, 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, 41 min, 42 min, 43 min, 44 min, 45 min, 46 min, 47 min, 48 min, 49 min, 50 min, 51 min, 52 min, 53 min, 54 min, 55 min, 56 min, 57 min, 58 min, 59 min, 60 min, 61 min, 62 min, 63 min, 64 min, or 65 min, or fall within the range of any two of the above values.

[0050] By adjusting the time of the third heat treatment within the above range, the temperature of the third heat treatment can be better matched, which not only promotes the chlorination reaction to proceed fully, but also avoids the growth of quartz crystal grains or the generation of lattice defects.

[0051] In a preferred embodiment of the method for removing mineral impurities within the quartz lattice structure of the present invention, the quartz crystal in step S1 is obtained from quartz sand through flotation, magnetic separation, and acid leaching.

[0052] Specifically, the steps include: First, the quartz sand is subjected to two selective flotation processes to remove physical impurities such as associated growth stones and mica; Then a magnetic separation is performed to remove magnetic impurities (such as garnet). Finally, a final leaching with an aqueous hydrogen fluoride (HF) solution is performed to remove chemically bonded impurities from the surface.

[0053] Preferably, the particle size of the quartz sand can be from 100μm to 300μm, for example, but not limited to 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm, 240μm, 260μm, 280μm or 300μm, or within the range of any two of the above values.

[0054] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention first uses a pre-activation treatment to break down the weak bonding structures on the surface and lattice edges of quartz crystals, creating reaction sites for subsequent chlorination reactions. Then, it employs segmented chlorination treatments of medium-temperature and high-temperature chlorination, combined with specific chlorination temperatures and specific chlorinating agents, to achieve directional chlorination of moderately volatile and non-volatile salt impurities. This allows the chloride impurities generated in the reaction to detach from the quartz system, thereby achieving deep removal of mineral impurities inside and outside the quartz lattice and obtaining high-purity quartz crystals. Attached Figure Description

[0055] The embodiments of this invention are not limited to the drawings described below, which are only some embodiments of this invention. Those skilled in the art can obtain drawings of other embodiments based on the content of this invention.

[0056] Figure 1 This is a process flow diagram of the method for removing mineral impurities within the quartz lattice structure according to the present invention. Detailed Implementation

[0057] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0058] Unless otherwise specified, all other materials and reagents used in the examples are commercially available.

[0059] Example 1 A method for removing mineral impurities within a quartz lattice structure, comprising the following steps (e.g.) Figure 1 (as shown) S1. Pre-activation treatment: Quartz crystals are placed in a fluidized bed reactor and subjected to the first heat treatment in a nitrogen atmosphere (N2). Quartz crystals are obtained from quartz sand through the following treatment: Quartz sand with a particle size of 100μm to 300µm is prepared. It is first subjected to two selective flotation processes to remove physical impurities such as associated growth stones and mica. Then, it is subjected to one magnetic separation to remove magnetic impurities such as garnet. Finally, it is subjected to one leaching with HF aqueous solution to remove surface chemically bonded impurities, and quartz crystals are obtained.

[0060] S2, Medium-temperature chlorination treatment: The quartz crystal treated in step S1 is placed in a mixed gas atmosphere of nitrogen (N2) and hydrogen chloride (HCl) for a second heat treatment.

[0061] S3, High-temperature chlorination treatment: The quartz crystal treated in step S2 is placed in a mixed gas atmosphere of nitrogen (N2), hydrogen chloride (HCl) gas and chlorine (Cl2) gas for a third heat treatment; The salts on the surface of the quartz crystal are then removed by washing or airflow purging to obtain high-purity quartz crystals.

[0062] Examples 2 to 3 Except for the temperature of the first heat treatment in step S1, which is different from that in Example 1, the rest is the same as in Example 1.

[0063] Examples 4 to 5 Except for the temperature of the second heat treatment in step S2, which is different from that in Example 1, the rest is the same as in Example 1.

[0064] Examples 6 to 9 Except for the gas atmosphere of the second heat treatment in step S2, which is different from that in Example 1, everything else is the same as in Example 1.

[0065] Examples 10 to 11 Except for the temperature of the third heat treatment in step S3, which is different from that in Example 1, the rest is the same as in Example 1.

[0066] Examples 12 to 13 Except for the gas atmosphere of the third heat treatment in step S3, which is different from that in Example 1, the rest is the same as in Example 1.

[0067] Example 14 Except for the time of the first heat treatment in step S1, the time of the second heat treatment in step S2, and the time of the third heat treatment in step S3, which are different from those in Example 1, the rest are the same as in Example 1.

[0068] Comparative Examples 1 to 2 Except for the temperature of the second heat treatment in step S2, which is different from that in Example 1, the rest is the same as in Example 1.

[0069] Comparative Examples 3 to 4 Except for the gas atmosphere of the second heat treatment in step S2, which is different from that in Example 1, everything else is the same as in Example 1.

[0070] Comparative Example 5 Except for the temperature of the third heat treatment in step S3, which is different from that in Example 1, the rest is the same as in Example 1.

[0071] Comparative examples 6 to 8 Except for the gas atmosphere of the third heat treatment in step S3, which is different from that in Example 1, everything else is the same as in Example 1.

[0072] Comparative Example 9 Except for omitting step S1, the rest is the same as in Example 1.

[0073] Comparative Example 10 Except for omitting step S2, the rest is the same as in Example 1.

[0074] The specific parameters and conditions for the methods of removing mineral impurities in the quartz lattice structure in each embodiment and comparative example are shown in Table 1.

[0075] Table 1 In Table 1, " / " indicates that there are no relevant parameters.

[0076] Performance Testing 1) Metal impurity content: 1.0g of sample was digested with high-purity hydrofluoric acid, and the content of each metal impurity was determined by ICP-MS (inductively coupled plasma mass spectrometry). The test results are shown in Tables 2 to 6. "Initial impurities" refers to various metallic impurities in quartz sand, while high-purity hydrofluoric acid refers to hydrofluoric acid with a concentration of 40%-49% (w / w), electronic grade (G5 grade / UP-S grade) or higher purity.

[0077] 2) Hydroxyl content: Measured using FT-IR (Fourier Transform Infrared Spectrometer) at 3500 cm⁻¹. -1 Up to 3700cm -1 The absorption peaks of the band were determined, and the hydroxyl content was calculated based on the Beer-Lambert law.

[0078] Table 2 Table 3 Table 4 Table 5 Table 6 According to the data in Tables 2 to 6, the Al content in the high-purity quartz crystals obtained in Examples 1 to 14 is reduced to below 1.75 ppb, the Fe content is reduced to below 0.52 ppb, and the individual values ​​of other metal element impurities are also at extremely low levels (ppb level). Calculated by the difference method, the purity of silicon dioxide is greater than 99.9992%, and breakthrough deep removal is achieved, especially for Al and Fe elements of interest in semiconductors. Furthermore, the hydroxyl content in the high-purity quartz crystals obtained in each example is stably controlled below 5 ppm, meeting the requirements for semiconductor-grade quartz products. This indicates that the method for removing mineral impurities within the quartz lattice structure of this invention can not only effectively improve the removal rate of mineral impurities within the quartz lattice structure but also effectively solve the problem of incomplete removal of hydroxyl (-OH) in traditional processes.

[0079] Comparative Examples 1 and 2 show that both excessively low and excessively high temperatures in the intermediate-temperature chlorination stage negatively impact the removal of mineral impurities within the quartz crystal structure. Comparative Examples 3 and 4 also reveal that excessively low or excessively high HCl concentrations in the mixed gas atmosphere during the intermediate-temperature chlorination stage also reduce the removal rate of mineral impurities within the quartz crystal structure. Comparative Example 5 shows that excessively low temperatures in the high-temperature chlorination stage make it difficult to effectively remove mineral impurities from the quartz crystal structure, resulting in lower purity of the quartz crystal.

[0080] Comparative Examples 6, 7, and 8 show that if the concentration of HCl in the mixed gas atmosphere during the high-temperature chlorination stage is too low or there is a lack of Cl2 or HCl, the removal rate of mineral impurities in the quartz crystal structure will also be significantly reduced. Comparative Examples 9 and 10 show that without pre-activation treatment or medium-temperature chlorination treatment, it is difficult to exert the synergistic effect of pre-activation treatment, medium-temperature chlorination treatment, and high-temperature chlorination treatment, resulting in lower purity of the quartz crystal.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for removing mineral impurities within a quartz crystal lattice structure, characterized in that, Includes the following steps: S1. Pre-activation treatment: The quartz crystal is placed in an inert gas atmosphere for the first heat treatment; S2, Medium-temperature chlorination treatment: The quartz crystal treated in step S1 is placed in a mixed gas atmosphere containing inert gas and hydrogen chloride gas for a second heat treatment. S3. High-temperature chlorination treatment: The quartz crystal treated in step S2 is placed in a mixed gas atmosphere of inert gas, hydrogen chloride gas and chlorine gas for a third heat treatment. The temperature of the first heat treatment is T1, the temperature of the second heat treatment is T2, and the temperature of the third heat treatment is T3, and the following conditions must be met: T1 < T2 < T3, 550℃ ≤ T1 ≤ 800℃, 800℃ < T2 < 1050℃, and T3 ≥ 1050℃. The volume ratio of the inert gas to the hydrogen chloride gas in step S2 is (70~80):(20~30). The volume ratio of the inert gas, hydrogen chloride gas and chlorine gas in step S3 is (5~40):(50~90):(5~15).

2. The method for removing mineral impurities within a quartz lattice structure as described in claim 1, characterized in that, 200℃≤T2-T1≤300℃.

3. The method for removing mineral impurities within a quartz lattice structure as described in claim 1 or 2, characterized in that, 100℃≤T3-T2≤200℃.

4. The method for removing mineral impurities within a quartz lattice structure as described in claim 1, characterized in that, At least one of the following conditions (1) to (2) must be met: (1) The T2 is 850℃ to 1000℃; (2) The T3 is 1050℃ to 1250℃.

5. The method for removing mineral impurities within a quartz lattice structure as described in claim 1, characterized in that, The mixed gas atmosphere in step S2 also contains chlorine, and the volume ratio of the inert gas, hydrogen chloride gas and chlorine is (70~80):(20~30):(0.5~5).

6. The method for removing mineral impurities within a quartz lattice structure as described in claim 1, characterized in that, The volume ratio of the inert gas, hydrogen chloride gas and chlorine gas in step S3 is (5~25):(70~90):(5~15).

7. The method for removing mineral impurities within a quartz lattice structure as described in claim 6, characterized in that, The volume ratio of the inert gas, hydrogen chloride gas and chlorine gas in step S3 is (10~20):(70~80):(8~12).

8. The method for removing mineral impurities within a quartz lattice structure as described in claim 7, characterized in that, The volume ratio of the inert gas, hydrogen chloride gas and chlorine gas in step S3 is 15:75:

10.

9. The method for removing mineral impurities within a quartz lattice structure as described in claim 1, characterized in that, At least one of the following conditions (1) to (3) must be met: (1) The duration of the first heat treatment is 10 min to 35 min; (2) The duration of the second heat treatment is 30 to 50 minutes; (3) The duration of the third heat treatment is 30 min to 65 min.

10. The method for removing mineral impurities within a quartz lattice structure as described in claim 1, characterized in that, The quartz crystals mentioned in step S1 are obtained from quartz sand through flotation, magnetic separation and acid leaching.

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