A method for purifying silicon dioxide from quartz minerals

Abstract

This invention discloses a method for purifying silica from quartz minerals, comprising the following steps: Step 1) Adding hydroxide to a quartz mineral slurry to obtain an aluminum removal reaction slurry, wherein the OH in the aluminum removal reaction slurry... ‑ The concentration is 0.02-0.5 mol / L; the aluminum removal reaction slurry is heated to 50-120℃ under closed conditions and stirred for 0.5-12 h. After the reaction, solid-liquid separation is performed to obtain aluminum-removed quartz mineral; step 2) a high-alkali enhanced oxidant solution is added to the aluminum-removed quartz mineral to obtain an iron removal reaction slurry, wherein the high-alkali enhanced oxidant contains peroxide, carbonate and hydroxide, and the OH- concentration in the iron removal reaction slurry is 0.5-10.0 mol / L; the iron removal reaction slurry is heated to 120-200℃ under closed conditions and stirred for 0.5-2 h, and then heated to 200-280℃ under closed conditions and stirred for 0.1-1 h. After the reaction, solid-liquid separation is performed to obtain purified silica.

Description

Technical Field

[0001] This invention relates to the field of mineral processing, and more specifically to a method for purifying silica from quartz minerals. Background Technology

[0002] High-purity quartz sand generally refers to quartz micro-powder with a SiO2 content higher than 99.99%. High-purity quartz possesses outstanding physicochemical properties and has been widely used in the photovoltaic, electronics, and high-end electric light source industries, making it an indispensable and important mineral raw material. High-purity quartz with extremely low impurity content is a very rare mineral material, forming only under specific geological conditions that meet particular chemical and physical parameters. Therefore, separating, removing impurities, and purifying SiO2 from quartzite ore is a crucial pathway for the preparation of high-purity quartz in China.

[0003] High-purity quartz sand is typically produced from high-grade quartz (SiO2 content greater than 99.80%) through processes such as mineral processing, jaw crushing, calcination, water quenching, screening, magnetic separation, color sorting, acid washing, flotation, wet screening, water washing, solid-liquid separation, sand baking, and strong magnetic separation. The price of the product is determined by the purity of SiO2. Currently, the highest purity that can be achieved in large-scale production has reached over 99.999% (5N), but the contradiction between its output and the large demand is very prominent.

[0004] Acid washing is currently the main method for chemical purification of quartz. However, when treating SiO2 minerals contaminated with Al / Fe in the form of lattice substitution, acid washing with HCl, HNO3, and H2SO4 is difficult to achieve ideal impurity removal results, and mixed acid washing containing HF is often required. The existing quartzite SiO2 purification technologies have the following drawbacks: 1) Removing Al-containing impurities through non-fluorinated acid washing is difficult, and fluorinated impurity removal systems present significant environmental problems; currently, there is no suitable washing system. Fine-grained Al-containing minerals (feldspar, mica, kaolin, illite, etc.) are difficult to remove by flotation separation. 2) Fe-containing impurities exist in silica minerals in the form of ionic lattice substitution, making removal through acid washing systems difficult, and requiring high energy consumption for lattice destruction, with no selectivity in high-temperature mineral phase reconstruction. Therefore, it is necessary to develop a method for effectively removing iron and aluminum impurities from quartz minerals to purify silica. Summary of the Invention

[0005] The purpose of this invention is to provide a method for purifying silicon dioxide from quartz minerals, thereby removing iron and aluminum impurities from quartz minerals.

[0006] The above objective can be achieved through the following technical solutions:

[0007] A method for purifying silica from quartz minerals includes the following steps:

[0008] Step 1) Add hydroxide to the quartz mineral slurry to obtain an aluminum removal reaction slurry. The OH in the aluminum removal reaction slurry... - The concentration is 0.02-0.5 mol / L; the aluminum removal reaction slurry is heated to 50-120℃ under closed conditions and stirred for 0.5-12 h. After the reaction is completed, solid-liquid separation is performed to obtain aluminum-removed quartz minerals.

[0009] Step 2) A high-alkali enhanced oxidant is added to the aluminum-removing quartz mineral to obtain an iron removal reaction slurry. The high-alkali enhanced oxidant contains peroxides, carbonates, and hydroxides. The OH- in the iron removal reaction slurry... - The concentration is 0.5–10.0 mol / L; the iron removal reaction slurry is heated to 120–200℃ under closed conditions and stirred for 0.5–2 h, and then heated to 200–280℃ under closed conditions and stirred for 0.1–1 h. After the reaction is completed, solid-liquid separation is performed to obtain purified silica.

[0010] Optionally, the quartz mineral slurry in step 1) is prepared by grinding the quartz mineral raw material at a grinding mass concentration of 50-70% to dissociate the quartz mineral raw material to a density of -0.074 mm of more than 80%.

[0011] Optionally, the grinding method can be vertical stirred grinding, horizontal stirred grinding, or disc grinding.

[0012] Optionally, the hydroxide in steps 1) and 2) is at least one of sodium hydroxide and potassium hydroxide.

[0013] Optionally, the high-alkali enhanced oxidant in step 2) includes: hydrogen peroxide, carbonate and hydroxide; the mass ratio of hydrogen peroxide: carbonate: hydroxide is 1-8:1-2:1;

[0014] Optionally, the carbonate is at least one of sodium carbonate, potassium carbonate, and ammonium carbonate.

[0015] Optionally, in step 1), 8-40 kg / t of caustic alkali is added based on the dry ore mass.

[0016] Optionally, in step 2), 100-800 kg / t of high-alkali enhanced oxidant is added based on the dry ore mass.

[0017] Optionally, the high-alkali enhanced oxidant in step 2) includes: percarbonate and hydroxide;

[0018] Optionally, the percarbonate is at least one of sodium percarbonate, potassium percarbonate, and ammonium percarbonate.

[0019] Optionally, the mass ratio of percarbonate to hydroxide is (1-10):1.

[0020] Optionally, the liquid-to-solid ratio of the aluminum removal reaction slurry and the iron removal reaction slurry is 2 to 6:1.

[0021] Optionally, the liquid obtained from solid-liquid separation in step 1) and the liquid phase obtained from solid-liquid separation in step 2) can be combined to obtain industrial water glass by-product.

[0022] Optionally, after solid-liquid separation in step 2), the purified silica is washed with deionized water.

[0023] The present invention has the following beneficial effects:

[0024] This invention employs a selective enhanced oxidative alkali leaching system for impurity removal, which can purify SiO2 from quartz mineral raw materials. This method exhibits low corrosion to equipment, low cost, and no secondary impurities. Impurities Al and Fe in the SiO2 purification system are selectively converted into soluble salts in a stepwise manner and removed through a multi-stage, gradually increasing-temperature alkali dissolution process, which significantly enhances the selectivity for removing iron and aluminum impurities, resulting in high impurity removal efficiency. Furthermore, this invention is a halogen-free process, based on advanced oxidation technology to promote the selective dissolution and transformation of Fe-containing silicates, offering excellent environmental performance.

[0025] The impurity removal system of this invention has strong adaptability and can be used for natural minerals such as quartz and silica, as well as for molten quartz minerals that have undergone smelting and impurity removal. It is highly adaptable to aluminum-containing mineral impurities and iron-containing mineral impurities, including various aluminum silicate mineral impurities and various Fe silicate mineral impurities, especially Fe affecting the SiO2 mineral content in the form of lattice substitution. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0027] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] To achieve the above objectives, the present invention provides a method for purifying SiO2 from quartz minerals.

[0031] The method of this invention removes iron and aluminum impurities from SiO2 mineral products through a two-step selective purification process. First, aluminum-containing mineral impurities are selectively removed from the minerals using a low-alkalinity hydroxide. Then, iron-containing mineral impurities are removed from the material through a high-alkalinity deep oxidation process. Specifically, this is achieved through the following steps:

[0032] Step 1) Selective grinding and dissociation of materials: Quartz mineral raw materials are ground at a mass concentration of 50-70% using a grinding method that mainly involves grinding to dissociate the material to more than 80% of the particles being -0.074mm, resulting in grinding slurry A, which is then introduced into an alkaline leaching and impurity removal reactor with a sealed function.

[0033] Step 2) Low-alkalinity leaching for aluminum removal: Add 8-40 kg / t of caustic alkali based on the dry ore mass, and then add some deionized water to adjust the liquid-solid ratio to slurry B of 2:1-6:1, to construct a selective impurity removal system a for low-alkalinity (relatively low-alkalinity) quartz-aluminum-containing minerals. This system mainly controls the OH... - The alkaline leaching conditions with SiO2 minerals and aluminum-containing minerals allow for rapid leaching / dissolution of aluminum-containing minerals into the liquid phase, while preserving the solid phase characteristics of SiO2 minerals as much as possible. Subsequently, the above slurry B is heated to 50-120°C and stirred for leaching to remove impurities. After stirring for 0.5-12 hours, the aluminum-containing impurity removal solution C and the impurity removal solid phase D are separated to remove Al impurities from the quartz minerals. The impurity removal solid phase D then proceeds to step 3) for secondary deep impurity removal with high alkali.

[0034] Step 3) High-alkali enhanced oxidation for deep iron removal: Add 100-800 kg / t of high-alkali enhanced oxidant (based on dry ore mass) to the impurity-removing solid phase D obtained in Step 2), and then add deionized water to adjust the liquid-solid ratio to obtain a slurry E with a liquid-solid ratio of 2:1-6:1, to construct a high-alkali enhanced rotatable impurity removal system b for quartz-iron-containing mineral impurities. This system is improved by controlling the H2O2 and CO3 content. 2- OH - The alkaline dissolution and enhanced oxidation processes involving SiO2 minerals and iron-bearing minerals preferentially dissolve and break down the iron-bearing minerals to form FeO2. - Then, the conditions for the impurity removal reaction are changed, and the strong oxidizing species O2(g) and ·OH formed during the process are used to enhance oxidation, causing the Fe species to form alkali-soluble FeO4. 2-The process involves dissolving iron impurities into the liquid phase, leaving SiO2 minerals in the solid phase. The slurry E is then heated to 120–200°C for a first stage of alkaline leaching to remove impurities, with a stirring time of 0.5–2.0 h. The temperature is then raised to 200–280°C for a second stage of enhanced oxidation, with a stirring time of 0.1–1.0 h, to further oxidize the iron-containing minerals and their intermediate species into high-valence soluble iron species. This allows the iron species to enter the iron-containing impurity removal solution F, while SiO2 minerals remain in the impurity-removed solid phase G. The solution F and solid phase G are then cooled and separated.

[0035] Step 4) Purification of SiO2 mineral washing: The impurity-removed solid phase G obtained in step 3) is repeatedly washed with deionized water 3 to 5 times to remove residual alkaline species on the surface of the material, and finally purified SiO2 mineral product H is obtained.

[0036] This invention proposes a selective grinding combined with a selective alkali dissolution system, which allows gangue minerals to undergo two stages of selective leaching to preferentially dissolve aluminum-containing and iron-containing mineral impurities, thereby achieving the purpose of removing impurities and purifying SiO2 from quartz mineral raw materials.

[0037] Specifically, the selective grinding and dissociation of materials described in step 1) is characterized by the fact that, taking into account the characteristics of aluminum-containing and iron-containing mineral impurities often filling the gaps in quartz minerals and being relatively easy to crush compared to quartz minerals, a grinding-based material grinding and dissociation method is adopted. Preferably, vertical stirred mills (stirring rods, stirring spirals, stirring discs, etc.), horizontal stirred mills (sand mills, etc.), and grinding discs are used to efficiently grind and dissociate aluminum-containing and iron-containing minerals, so that the impurity minerals are preferentially ground to a fine particle size and their surfaces are fully exposed, providing favorable conditions for subsequent alkaline dissolution and destruction.

[0038] Step 2) involves using caustic alkalis such as sodium hydroxide and potassium hydroxide. A low alkali concentration is used for the preferential alkali dissolution of aluminum-containing minerals (feldspar, kaolin, illite, and other aluminosilicate minerals). The key chemical reaction process is as follows (thermodynamic data are from HSC 9.0, using the reaction activity of 1.0 mol / L NaOH as an example, with a reaction temperature of 100℃, and related thermodynamic calculations performed):

[0039] 6OH - +NaAlSi3O8 = NaAlO2+3H2SiO3+1.5O2(g) △G=-133.93 kJ / mol (Formula 1)

[0040] Na2Al2Si6O 16 + 12NaOH = 2NaAlO2+6Na2SiO3+6H2O △G=-72.67 kJ / mol (Formula 2)

[0041] 2NaOH + Al2O3 = 2NaAlO2 + H2O △G=-18.03 kJ / mol (Formula 3)

[0042] 4OH - + 2SiO2 = 2H2SiO3 + O2(g) △G=-146.19 kJ / mol (Equation 4)

[0043] 2NaOH+SiO2=Na2SiO3+H2O△G=-44.96kJ / mol (Formula 5)

[0044] Thermodynamically, the alkali dissolution expression of feldspar minerals (Equation 2) preferentially dissolves compared to Equation (5). The above equation preferentially dissolves to obtain H2SiO3 and O2. However, under alkaline conditions, H2SiO3 is in an unstable state, thus requiring a low-alkali (low OH) reaction. - The concentration can make the aluminum removal system selectively react with (Equation 2) as the main reaction, thereby achieving the removal of Al-containing minerals.

[0045] Step 3) uses a high-alkali enhanced oxidant that is a solvent containing carbonate ions and strong oxidizing properties. This includes a combination of hydrogen peroxide, carbonate, and hydroxide, or a combination of percarbonate and hydroxide. The combined agents are used in a mass ratio of hydrogen peroxide: carbonate: hydroxide = (1-8):(1-2):1. When percarbonate is used, the mass ratio of percarbonate to hydroxide is (1-10):1. The carbonate is one or more of sodium carbonate, potassium carbonate, and ammonium carbonate, and the percarbonate is one or more of sodium percarbonate, potassium percarbonate, and ammonium percarbonate.

[0046] Under high-alkali conditions, a reaction process generates highly reactive species such as high-concentration active O2(g) and ·OH. High-alkali oxidation is then used to pre-disrupt and leach iron-containing mineral lattices into intermediate FeO2. - The intermediate is then subjected to further increases in temperature and pressure to enhance the activity of the active species within the reactor, resulting in a secondary oxidation reaction. The O2 and ·OH formed under high temperature and pressure then deeply oxidize FeO2. - To FeO4 2- The transformation involves converting iron-containing minerals into soluble salts; a key chemical reaction process in the high-alkali stage is as follows:

[0047] Na2CO3 + Fe2SiO4 + H2O2 = 2NaFeO2 + CO2(g) + H2SiO3 △G=-40.46 kJ / mol (Formula 6)

[0048] 2H₂O₂ + 2SiO₂ = 2H₂SiO₃ + O₂(g) △G=-121.35 kJ / mol (Equation 7)

[0049] Fe2SiO4 + 2NaOH + H2O2 = H2SiO3 + 2NaFeO2 + H2O △G=-182.20 kJ / mol (Formula 8)

[0050] 2H2O2+2SiO2+2Na2CO3=2Na2SiO3+O2(g)+2H2CO3(a)△G=-70.10kJ / mol (Formula 9)

[0051] Iron-containing silicate minerals (Formula 8) should preferentially react and dissolve compared to quartz minerals (Formulas 9 and 7), preferentially dissolving H2O2 to obtain O2 and ·OH, thus achieving preferential dissolution and destruction of Fe-containing minerals. Then, further increasing the temperature and pressure enhances the oxidation activity. The important chemical reaction process achieved by the two-stage heating and pressurization reaction is as follows:

[0052] NaFeO2 + O2 / (·OH) + OH - → Na2FeO4 + NaOH (Equation 10)

[0053] Through the two-stage enhanced oxidation reaction described above, iron-containing impurity minerals in the system are dissolved and enter the liquid phase, leaving behind a high-purity SiO2 mineral solid phase.

[0054] Step 4) The purified SiO2 mineral is thoroughly washed to obtain purified SiO2 mineral; the obtained SiO2 mineral product meets the requirements of silicon dioxide and can meet the actual needs of the production of special quartz glass products for the semiconductor and photovoltaic industries.

[0055] The impurity removal solution F obtained in steps 2) and 3) above can be mixed with aluminum-containing impurity removal solution C to be used as an industrial water glass by-product.

[0056] Example 1

[0057] A certain SiO2 mineral was obtained from natural quartzite ore through crushing, grinding, and acid flotation separation. The product had a particle size of -0.074 mm (90%) and a SiO2 content of 99.7%. The main impurities were 0.1% Al2O3 and 0.12% TFe, with 0.11% Fe present as FeO lattice substitution, contaminating the SiO2 mineral. Conventional non-fluorinated acid washing methods were insufficient to remove the Al / Fe impurities, and the product failed to meet the standards for electronic-grade SiO2 minerals. This invention addresses this issue by processing the SiO2 mineral product.

[0058] A certain mass of material A is ground to -0.038mm (90%) and then introduced into a closed alkaline leaching and impurity removal reactor.

[0059] For low-alkalinity leaching to remove aluminum, 20 kg / t of sodium hydroxide is added to the finely ground material A based on its dry ore weight, and then some deionized water is added to adjust it into a slurry B with a liquid-to-solid ratio of 3:1. - The concentration was 0.17 mol / L. The mixture was heated to 105 °C and stirred to remove impurities. After stirring for 2 hours, aluminum-containing impurity removal solution C and impurity removal solid phase D were separated.

[0060] For the impurity-removing solid phase D, high-alkali enhanced oxidation is used for deep iron removal. 200 kg / t of high-alkali enhanced oxidant (a 2:1 mixture of sodium percarbonate and sodium hydroxide) is added based on the dry ore mass. Deionized water is then added to adjust the liquid-to-solid ratio to 5:1. - Slurry E with a concentration of 0.8–1.0 mol / L was reacted at 140°C for 1 hour to dissolve iron-containing minerals. Then, the temperature was raised to 230°C for a second stage of stirring and enhanced oxidation reaction for 0.5 hours to enhance the oxidation of iron-containing species into high-valence soluble iron species. This allowed the iron species to enter the iron-containing impurity removal solution F, while SiO2 minerals remained as the impurity removal solid phase G. Subsequently, the iron-containing impurity removal solution F and the impurity removal solid phase G were separated by cooling.

[0061] After washing and removing impurities from the solid phase G, a purified product with a SiO2 content of 99.99%, an Al2O3 content of ≤0.0002%, and an Fe content of ≤0.0001% is finally obtained, meeting the requirements for electronic-grade SiO2 micro powder products.

[0062] Example 2

[0063] The raw quartzite ore has a SiO2 content of 98%, with impurities mainly consisting of 0.5% Al2O3 and 0.8% Fe2O3. The Al-containing impurities are primarily aluminosilicate minerals such as feldspar, kaolinite, and illite, exhibiting a relatively complex composition and being easily brittle. The Ca-containing impurities are mainly calcite, which is easily dissolved by acid. Fe mainly exists in the form of ferrous silicate; due to its relatively low lattice quantity, Fe substitutes for SiO2, resulting in extremely weak magnetic properties and making it difficult to remove via strong magnetic separation. This invention is used to process this quartz ore with a SiO2 content of 98%.

[0064] A certain mass of material A is ground to -0.074mm (90%) and then introduced into a closed alkaline leaching and impurity removal reactor.

[0065] For low-alkalinity leaching to remove aluminum, 40 kg / t of sodium hydroxide is added to the finely ground material A based on its dry ore weight, and then some deionized water is added to adjust it into a slurry B with a liquid-to-solid ratio of 2:1. -The concentration was 0.5 mol / L. The mixture was heated to 120℃ and stirred for leaching to remove impurities. After stirring for 6 hours, aluminum-containing impurity removal solution C and impurity removal solid phase D were separated.

[0066] For the impurity-removing solid phase D, high-alkali enhanced oxidation is used for deep iron removal. 600 kg / t of high-alkali enhanced oxidant (a mixture of hydrogen peroxide, sodium carbonate, and sodium hydroxide in a 4:2:1 ratio) is added based on the dry ore mass. Deionized water is then added to adjust the liquid-to-solid ratio to 3:1. - Slurry E with a concentration of 1.8–2.0 mol / L was reacted at 120°C for 0.5 h to dissolve iron-containing minerals as intermediate iron-containing species. Then, the high-concentration active O2 and ·OH produced were used to carry out a second stage of stirring and enhanced oxidation reaction at 250°C for 0.5 h to enhance the oxidation of iron-containing species into high-valence soluble iron species. This allowed the iron species to enter the iron-containing impurity removal solution F, while SiO2 minerals remained as impurity removal solid phase G. Subsequently, the iron-containing impurity removal solution F and impurity removal solid phase G were separated by cooling.

[0067] After washing and removing impurities from the solid phase G, a purified product with a SiO2 content of 99.95%, an Al2O3 content of ≤0.02%, and an Fe2O3 content of ≤0.01% is finally obtained, which meets the requirements for electrical grade SiO2 micro powder products.

[0068] Example 3

[0069] A certain molten SiO2 mineral product has a SiO2 content of 99.8%, and the main impurities are 0.05% Al2O3 and 0.1% Fe2O3. In this material, Fe exists in the SiO2 lattice in the form of ion exchange, making it difficult to remove. The method of this invention is used to process this molten silica material with a SiO2 content of 99.8%.

[0070] A certain mass of material A is ground to -0.074 mm (80%), and then introduced into a closed alkaline leaching reactor for impurity removal. For low-alkalinity leaching to remove aluminum, 8 kg / t of sodium hydroxide is added to the ground material A based on its dry ore mass, and then some deionized water is added to adjust it to a slurry B with a liquid-to-solid ratio of 5:1. - The concentration was 0.04 mol / L. The mixture was heated to 70 °C and stirred for leaching to remove impurities. After stirring for 2 hours, aluminum-containing impurity-removing solution C and impurity-removing solid phase D were separated.

[0071] For the impurity-removing solid phase D, high-alkali enhanced oxidation is used for deep iron removal. 300 kg / t of high-alkali enhanced oxidant (a mixture of potassium percarbonate and potassium hydroxide in a 6:1 ratio) is added based on the dry ore mass. Deionized water is then added to adjust the liquid-to-solid ratio to 4:1. -Slurry E with a concentration of 1.2–1.5 mol / L was reacted at 100°C for 1 hour to dissolve iron-containing minerals as intermediate iron-containing species. Then, the high-concentration active O2 and ·OH produced were used to carry out a second stage of stirring and enhanced oxidation reaction at 280°C for 2 hours to enhance the oxidation of iron-containing species into high-valence soluble iron species. This allowed the iron species to enter the iron-containing impurity removal solution F, while SiO2 minerals remained as impurity removal solid phase G. Subsequently, the iron-containing impurity removal solution F and impurity removal solid phase G were separated by cooling.

[0072] After washing and removing impurities from the solid phase G, a purified product with a SiO2 content of 99.99%, an Al2O3 content of ≤0.002%, and an Fe2O3 content of ≤0.001% is finally obtained, which meets the requirements for electronic-grade SiO2 micro powder products.

[0073] Furthermore, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for purifying silica from quartz minerals, characterized in that, Includes the following steps: Step 1) Add hydroxide to the quartz mineral slurry to obtain an aluminum removal reaction slurry. The OH in the aluminum removal reaction slurry... - The concentration is 0.02~0.5mol / L; the aluminum removal reaction slurry is heated to 50-120 ℃ under closed conditions and stirred for 0.5~12 h. After the reaction is completed, solid-liquid separation is performed to obtain aluminum-removed quartz minerals. Step 2) Add a high-alkali enhanced oxidant to the aluminum-removing quartz mineral to obtain an iron removal reaction slurry. The high-alkali enhanced oxidant is hydrogen peroxide, carbonate, and hydroxide, or the high-alkali enhanced oxidant is percarbonate and hydroxide. The OH- in the iron removal reaction slurry... - The concentration is 0.5~10.0 mol / L; the iron removal reaction slurry is heated to 120~200 ℃ under closed conditions and stirred for 0.5~2 h, and then heated to 200~280 ℃ under closed conditions and stirred for 0.1~1 h. After the reaction is completed, solid-liquid separation is performed to obtain purified silica.

2. The method for purifying silica from quartz minerals according to claim 1, characterized in that, The quartz mineral slurry in step 1) is prepared by grinding the quartz mineral raw material at a grinding mass concentration of 50-70% to dissociate the quartz mineral raw material to a particle size of -0.074 mm or more, which accounts for more than 80%.

3. The method for purifying silica from quartz minerals according to claim 2, characterized in that, The grinding method is vertical stirred grinding, horizontal stirred grinding, or disc grinding.

4. The method for purifying silica from quartz minerals according to claim 1, characterized in that, The hydroxide in steps 1) and 2) is at least one of sodium hydroxide and potassium hydroxide.

5. The method for purifying silica from quartz minerals according to claim 1, characterized in that, In step 2), the mass ratio of hydrogen peroxide: carbonate: hydroxide in the high-alkali enhanced oxidant is 1~8:1~2:

1.

6. The method for purifying silica from quartz minerals according to claim 1, characterized in that, The carbonate is at least one of sodium carbonate, potassium carbonate, and ammonium carbonate.

7. The method for purifying silica from quartz minerals according to claim 1, characterized in that, In step 2), 100-800 kg / t of high-alkali enhanced oxidant is added based on the dry ore mass.

8. The method for purifying silica from quartz minerals according to claim 1, characterized in that, The percarbonate is at least one of sodium percarbonate, potassium percarbonate, and ammonium percarbonate.

9. The method for purifying silica from quartz minerals according to claim 1, characterized in that, The mass ratio of percarbonate to hydroxide is (1~10):

1.

10. The method for purifying silica from quartz minerals according to claim 1, characterized in that, The liquid-to-solid ratio of the aluminum removal reaction slurry and the iron removal reaction slurry is 2~6:

1.

11. The method for purifying silica from quartz minerals according to claim 1, characterized in that, The liquid obtained from solid-liquid separation in step 1) and the liquid phase obtained from solid-liquid separation in step 2) are combined to obtain industrial water glass by-product.

12. The method for purifying silica from quartz minerals according to claim 1, characterized in that, After solid-liquid separation in step 2), the purified silica is washed with deionized water.