High-purity quartz sand purification process based on oxidation-reduction synergistic modification

Abstract

The invention relates to the technical field of quartz sand purification and preparation, in particular to a high-purity quartz sand purification process based on oxidation-reduction synergistic modification, which comprises the following steps: S1, pretreating raw ore, and performing preliminary roasting treatment to obtain first crude ore; s2, the first coarse ore is subjected to oxidizing roasting treatment, and second coarse ore is obtained; s3, the second coarse ore is subjected to reduction roasting treatment, and third coarse ore is obtained; s4, the third coarse ore is subjected to magnetic separation treatment, and first concentrate is obtained; s5, the first concentrate is subjected to flotation treatment through a composite flotation reagent under the acidic condition, and second concentrate is obtained; and S6, the second concentrate is sequentially subjected to acid leaching, washing and heat treatment under the high-temperature and high-pressure conditions, and high-purity quartz sand concentrate is obtained. According to the method disclosed by the invention, deep removal of iron impurities and green and efficient production are realized through combination of calcining water quenching, redox synergistic modification and gradient magnetic separation technologies.

Description

Technical Field

[0001] The present invention relates to the technical field of quartz sand purification preparation, and in particular to a high-purity quartz sand purification process based on oxidation-reduction synergistic modification. Background Art

[0002] High-purity quartz sand (SiO2 purity ≥ 99.99%) is a core material for strategic emerging industries such as semiconductors, photovoltaics, and optical fibers, and its application demand continues to grow. In the semiconductor field, high-purity quartz sand is used to manufacture single-crystal silicon growth crucibles and quartz glass devices, directly affecting the chip yield. Insufficient purity will lead to excessive impurities in the silicon rod, thereby affecting the performance of integrated circuits. The presence of iron impurities severely restricts the performance of high-purity quartz sand. Its occurrence forms are diverse, including surface iron oxide films, isomorphic substitution within the lattice (Fe 3+ substituting Si 4+ ), and inclusion minerals (such as hematite and magnetite). These impurities not only cause a decrease in optical transmittance and electrical leakage current problems, but also migrate to the silicon lattice during the high-temperature silicon melting process, forming defects, reducing the purity of single-crystal silicon and the photovoltaic conversion efficiency, while increasing the crucible replacement frequency and production costs. Current iron removal technologies face triple bottlenecks of efficiency, cost, and environmental protection.

[0003] The existing patent CN201911049853.3 discloses a quartz sand pickling purification process, including: S1) adding the quartz sand to be treated, a catalyst, and an acid to a reaction kettle and stirring for 36 - 48 h to obtain a soaking solution; S2) heating the soaking solution obtained in S1 to 60 - 100 °C, reacting for 6 - 12 h, and then naturally cooling to room temperature to obtain an acidified reaction solution; S3) centrifuging the acidified reaction solution obtained in S2 to obtain a mixed solution of the catalyst and the acid and a crude quartz sand product; S4) adding water to submerge the crude quartz sand product prepared in S3 and adding an oxidant under stirring and reacting for 1 - 2 h to obtain an oxidation reaction solution; S5) adding an alkali solution to the oxidation reaction solution prepared in S4 to adjust the pH value to neutral to obtain a neutral mixed solution; S6) centrifuging the neutral mixed solution obtained in S5 to obtain a wet quartz sand product; S7) cleaning the wet quartz sand product obtained in S6 and drying it to obtain a quartz sand finished product. The process of the present invention can effectively remove the influence of iron and improve the product quality. However, in the above technical solution, the separation effect on micron-sized iron oxides is poor. In addition, although the acid leaching method can deeply remove the inclusion iron, hydrofluoric acid is highly corrosive and requires corrosion-resistant equipment. The waste liquid treatment cost accounts for 40% - 50% of the total cost, and the environmental risk is prominent. Summary of the Invention

[0004] In view of this, the present invention proposes a high-purity quartz sand purification process based on oxidation-reduction synergistic modification to solve the technical problems of poor iron removal effect, easy equipment corrosion, and high environmental risk in the existing quartz sand purification process.

[0005] The technical solution of the present invention is realized as follows: The present invention provides a purification process for high-purity quartz sand based on oxidation-reduction synergistic modification, including the following steps:

[0006] S1. After the raw ore is pretreated, it is subjected to preliminary roasting treatment to obtain the first crude ore;

[0007] S2. The first crude ore is subjected to oxidation roasting treatment to obtain the second crude ore;

[0008] S3. The second crude ore is subjected to reduction roasting treatment to obtain the third crude ore;

[0009] S4. The third crude ore is subjected to magnetic separation treatment to obtain the first concentrate;

[0010] S5. The first concentrate is subjected to flotation treatment with a composite flotation reagent under acidic conditions to obtain the second concentrate;

[0011] S6. The second concentrate is successively subjected to acid leaching, washing, and heat treatment under high temperature and high pressure conditions to obtain high-purity quartz sand concentrate.

[0012] Specifically, in the present invention, an oxidation-reduction roasting coupled with magnetic separation technology is adopted. By regulating the occurrence form and magnetic difference of iron impurities, the iron removal efficiency of high-purity quartz sand is significantly improved. Specifically, first, through oxidation roasting, weakly magnetic substances such as limonite and chromite in quartz are converted into Fe2O3; then, in the reduction roasting stage, hematite, pyrite, ilmenite, etc. are selectively reduced to strongly magnetic magnetite (Fe3O4) or iron, while the quartz matrix remains chemically inert, thereby maximizing the magnetic difference between the iron phase and quartz.

[0013] On the basis of the above technical solution, preferably, in step S1, the pretreatment includes grinding the raw ore to a particle size where the proportion of 70-200 mesh is ≥85%; the temperature of the preliminary roasting is 900-1200 °C, and the roasting time is 1-2.5 h. More preferably, the grinding in the pretreatment is wet grinding, the pulp concentration of the wet grinding is controlled at 50-80%, and the grinding time is 5-10 min.

[0014] Specifically, in step S1, first, through wet fine grinding, preliminary roasting, and rapid quenching with water after roasting, a first crude ore with a micro-crack structure is obtained.

[0015] On the basis of the above technical solution, preferably, in step S2, oxidation roasting is carried out with an oxidant. The temperature of the oxidation roasting is 400-800 °C, the time is 1-3 h, and the oxidant is oxygen or sodium peroxide. More preferably, the oxidant is oxygen, and the oxygen concentration ≥28%.

[0016] In the oxidative roasting stage, weakly magnetic substances such as limonite and chromite in the gas-liquid inclusions or on the surface of quartz, which are not easily reducible, are transformed into Fe2O3. In this stage, the chemical forms of iron impurities are unified to prepare for the subsequent reduction process. At the same time, some oxidation reactions also help to destroy the lattice structures of certain impurity minerals, making them easier to separate.

[0017] On the basis of the above technical solutions, preferably, in step S3, reduction roasting is carried out with a reducing agent. The temperature of the reduction roasting is 600 - 1200 °C, the time is 45 - 75 min, the reducing agent is one or more of iron powder, iron carbonate and coke powder, and the addition amount of the reducing agent is 3 - 8% of the mass of the original ore. More preferably, the reducing agent is iron powder, the temperature is controlled at 1000 °C ± 10 °C, and an inert atmosphere is used.

[0018] In the reduction roasting stage, the second rough ore is mixed with a solid reducing agent and subjected to reduction roasting at an appropriate temperature to selectively reduce various iron minerals to strongly magnetic magnetite (Fe3O4) or iron. This stage significantly enhances the magnetism of iron impurities, while the quartz matrix remains chemically inert, thus maximizing the magnetic difference between the iron phase and quartz and creating ideal conditions for subsequent magnetic separation.

[0019] On the basis of the above technical solutions, preferably, in step S4, the magnetic field strength for magnetic separation treatment is 1.2 - 2.4 T, the flow rate of the magnetic separation pulp is controlled at 0.8 - 1.5 m / s, and the magnetic medium uses a multi-layer mesh stainless steel magnetic conductor. The high-intensity magnetic field can capture the weakly magnetic particles after reduction treatment to ensure the efficient separation of magnetic impurities. The appropriate pulp flow rate balances the separation efficiency and processing capacity. Too fast a flow rate will reduce the magnetic separation effect, and too slow a flow rate will affect the production efficiency.

[0020] On the basis of the above technical solutions, preferably, in step S5, the acidic condition is that the pH is 2, and the pH of the first concentrate is adjusted by HF and / or H2SO4.

[0021] On the basis of the above technical solutions, preferably, in step S5, the composite flotation reagent includes a collector, a dispersant, an inhibitor and a foaming agent. The collector is sodium dodecyl sulfonate, dodecylamine polyethylene ether and sodium dibutylnaphthalene sulfonate, the dispersant is sodium pyrophosphate, the inhibitor is water glass, the foaming agent is methyl isobutyl carbinol, and the flotation treatment time is 30 - 90 min.

[0022] Based on the above technical solutions, preferably, the addition amount of sodium dodecyl sulfonate is 50 - 200 g / t of the mass of the raw ore, the addition amount of dodecylamine polyoxyethylene ether is 50 - 250 g / t of the mass of the raw ore, the addition amount of sodium dibutylnaphthalene sulfonate is 50 g / t of the mass of the raw ore, the addition amount of sodium pyrophosphate is 50 - 100 g / t of the mass of the raw ore, the addition amount of sodium silicate is 300 - 500 g / t of the mass of the raw ore, and the addition amount of methyl isobutyl carbinol is 150 - 200 g / t of the mass of the raw ore.

[0023] In the flotation treatment stage, first, HF and H2SO4 are used to adjust the pH to 2 to reach the zero - charge point of quartz. Thus, quartz is neutral and uncharged, while impurities such as mica and feldspar in the pulp are negatively charged on the surface due to their zero - charge points at pH 1 - 1.7 and are easily collected by cationic collectors. Therefore, the cationic collector dodecylamine polyoxyethylene ether is used to collect negatively charged impurities such as mica and feldspar on the surface. Since there may be free metal ions such as calcium and magnesium in the pulp and fine magnetite impurities that are not completely removed by magnetic separation, which are positively charged, the anionic collector sodium dodecyl sulfonate is used in the flotation system to collect and remove impurities to ensure the purity of quartz sand. Sodium pyrophosphate and sodium silicate play a role in preventing the aggregation of fine particles in the pulp and inhibiting the flotation of quartz, avoiding the loss of quartz by flotation. Methyl isobutyl carbinol is a surfactant with hydrophilic and hydrophobic groups, which is adsorbed on the water - air interface directionally, reducing the surface tension of the aqueous solution, making the air filled into the water easy to disperse into bubbles and stabilize the bubbles. The frother and the collector are adsorbed on the surface of mineral particles together, causing the mineral particles to float.

[0024] Based on the above technical solutions, preferably, in step S6, the solution for acid leaching treatment is a mixture of hydrochloric acid, nitric acid, and hydrofluoric acid with a volume ratio of 1:0.5 - 1:0.1, and the acid leaching treatment time is 12 - 24 h.

[0025] Based on the above technical solutions, preferably, in step S6, the atmosphere for heat treatment is hydrogen chloride, the heat treatment temperature is 900 - 1200 °C, and the heat treatment time is 1 - 2 h.

[0026] The mixed - acid system acts synergistically. Metal oxide impurities are dissolved by hydrochloric acid and nitric acid, while hydrofluoric acid effectively removes silicate - type impurities. The optimized ratio of the three ensures efficient impurity removal while minimizing the corrosion of the quartz matrix. Heat treatment in a hydrogen chloride atmosphere can capture and volatilize residual metal elements and repair quartz lattice defects at high temperatures, thereby obtaining ultra - high - purity quartz concentrate.

[0027] A high - purity quartz sand purification process based on oxidation - reduction synergistic modification of the present invention has the following beneficial effects compared with the prior art:

[0028] (1) The high-purity quartz sand purification process provided by the present invention realizes the deep purification of low-iron-content high-purity quartz sand through an innovative technical route of calcination-water quenching - redox synergistic modification - gradient magnetic separation. This method proposes a systematic and complete solution to the industry problems such as the difficulty in removing weakly magnetic impurities, the insufficient exposure of inclusion impurities, and the large pollution in acid leaching treatment in the traditional purification process. Through the organic combination of physical, chemical, and physicochemical methods, the removal efficiency of iron impurities is significantly improved, while the resource and energy consumption are reduced, realizing the green and efficient production of high-purity quartz sand.

[0029] (2) First, through calcination-water quenching (rapid cooling at 900 - 1200 °C), the internal gas-liquid and mineral inclusions in quartz are broken, increasing the exposed area of impurities. There is no dependence on high-energy-consuming equipment, and it lays a physical foundation for subsequent oxidation-reduction modification. Then, the redox synergistic modification technology is adopted to convert weakly magnetic impurities such as hematite and limonite into strongly magnetic Fe3O4 or metallic Fe. Finally, the iron content of the high-purity quartz sand is ≤ 0.3 ppm. First, all kinds of iron impurities are uniformly converted into the form of iron oxides in the oxidation stage, and then these oxides are selectively reduced to strongly magnetic magnetite or metallic iron in the reduction stage, while the quartz matrix remains chemically inert. This treatment method maximizes the magnetic difference between quartz and iron impurities, significantly improving the separation efficiency of subsequent magnetic separation and realizing the deep removal of iron impurities in quartz sand.

[0030] (3) In addition, in the present invention, the oxidant is oxygen, which is environmentally friendly and efficient; the reducing agent is solid reducing agent iron powder, and the excess iron powder can be removed together with magnetic substances in the magnetic separation process, avoiding the use of gases such as hydrogen and methane, which is safe and efficient. After gradient magnetic separation, most of the iron impurities are removed. For the subsequent acid leaching, the mixed acid of hydrochloric acid, nitric acid, and hydrofluoric acid has a volume ratio of 1:0.5:0.1, which is 50 - 40% less than that of nitric acid and hydrofluoric acid in the traditional process. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is the method flow chart of the high-purity quartz sand purification process based on redox synergistic modification of the present invention. Detailed Embodiments

[0033] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Example 1

[0035] This example provides a high-purity quartz sand purification process based on oxidation-reduction synergistic modification, including the following steps:

[0036] S1. Using the quartz raw ore of granite pegmatite type produced in a certain place as the raw material, after pretreatment of the raw ore, it is wet-ground to a particle size of 70-200 mesh with a proportion of ≥85%, calcined at 1000 °C for 2 h, and then quenched and rapidly cooled with water to obtain the first rough ore with a micro-crack structure.

[0037] S2. Oxidatively calcine the first rough ore with a particle size of 70-200 mesh at an oxygen concentration of 28% and a temperature of 600 °C for 1 h to obtain the oxidized second rough ore.

[0038] S3. At 1000 °C, add iron powder accounting for 5% of the mass of the ore raw material to the second rough ore and perform reduction roasting for 1 h to obtain the third rough ore with enhanced magnetism.

[0039] S4. Perform magnetic separation on the third rough ore with a magnetic field intensity of 1.8 T and a pulp flow rate of 1.2 m / s, and remove magnetic impurities to obtain the first concentrate.

[0040] S5. The first concentrate is floated at pH = 2 with a flotation reagent system of 150 g / t of sodium dodecyl sulfonate, 150 g / t of dodecylamine polyethylene ether, 50 g / t of sodium dibutylnaphthalene sulfonate, 80 g / t of sodium pyrophosphate, 350 g / t of water glass, and 200 g / t of methyl isobutyl carbinol for 1 h to obtain the second concentrate.

[0041] S6. The second concentrate is acid-leached at 150 °C for 18 h with hydrochloric acid, nitric acid, and hydrofluoric acid (volume ratio 1:0.5:0.1, 800 g / t), and washed 5 times with deionized water. Heat-treat it at 1050 °C for 2 h in a hydrogen chloride atmosphere to finally obtain high-purity quartz concentrate.

[0042] Example 2

[0043] This example provides a high-purity quartz sand purification process based on oxidation-reduction synergistic modification, including the following steps:

[0044] S1. Using the quartz raw ore of vein quartz type produced in a certain place as the raw material, after pretreatment of the raw ore, it is wet-ground to a particle size of 70-200 mesh with a proportion of ≥85%, calcined at 1000 °C for 2 h, and then quenched and rapidly cooled with water to obtain the first rough ore with a micro-crack structure.

[0045] S2. Then, roast the first coarse ore with a particle size of 70 - 200 mesh at an oxygen concentration of 28% and a temperature of 600 °C for 1 h to obtain the second oxidized coarse ore.

[0046] S3. Next, at 1000 °C, add iron powder accounting for 3% of the mass of the ore raw material to the second coarse ore and perform reduction roasting for 1 h to obtain the third coarse ore with enhanced magnetism.

[0047] S4. Perform magnetic separation on the third coarse ore with a magnetic field strength of 1.8 T and a pulp flow rate of 1.2 m / s to obtain the first concentrate after removing magnetic impurities.

[0048] S5. The first concentrate is floated at pH 2 for 1 h with a flotation reagent system consisting of 100 g / t of sodium dodecyl sulfonate, 100 g / t of dodecylamine polyethylene ether, 50 g / t of sodium dibutylnaphthalene sulfonate, 80 g / t of sodium pyrophosphate, 450 g / t of water glass, and 200 g / t of methyl isobutyl carbinol to obtain the second concentrate.

[0049] S6. The second concentrate is acid-leached at 150 °C for 18 h with hydrochloric acid, nitric acid, and hydrofluoric acid (volume ratio 1:0.5:0.1, 800 g / t) and washed 5 times with deionized water. Heat-treat it at 1050 °C for 2 h in a hydrogen chloride atmosphere to finally obtain high-purity quartz concentrate.

[0050] Example 3

[0051] This example provides a high-purity quartz sand purification process based on oxidation-reduction synergistic modification, including the following steps:

[0052] S1. Using the quartz rock-type quartz raw ore produced in a certain place as the raw material, after pretreatment of the raw ore, it is wet-ground to a particle size of 70 - 200 mesh with a proportion of ≥85%, roasted at 1000 °C for 2 h, and then quenched and rapidly cooled with water to obtain the first coarse ore with a microcrack structure.

[0053] S2. Then, roast the first coarse ore with a particle size of 70 - 200 mesh at an oxygen concentration of 28% and a temperature of 600 °C for 2 h to obtain the second oxidized coarse ore.

[0054] S3. Next, at 1000 °C, add iron powder accounting for 6% of the mass of the ore raw material to the second coarse ore and perform reduction roasting for 1 h to obtain the third coarse ore with enhanced magnetism.

[0055] S4. Perform magnetic separation on the third coarse ore with a magnetic field strength of 1.8 T and a pulp flow rate of 1.2 m / s to obtain the first concentrate after removing magnetic impurities.

[0056] S5. The first concentrate is at pH 2, and is subjected to flotation using a flotation reagent system consisting of 180 g / t of sodium dodecyl sulfonate, 180 g / t of dodecylamine polyoxyethylene ether, 50 g / t of sodium dibutylnaphthalene sulfonate, 100 g / t of sodium pyrophosphate, 300 g / t of water glass, and 200 g / t of methyl isobutyl carbinol to obtain a second concentrate.

[0057] S6. The second concentrate is acid-leached at 150 °C for 18 h with hydrochloric acid, nitric acid, and hydrofluoric acid (volume ratio 1:0.5:0.1, 800 g / t), and washed 5 times with deionized water. It is heat-treated at 1050 °C for 2 h in a hydrogen chloride atmosphere to finally obtain high-purity quartz concentrate.

[0058] Example 4

[0059] This example provides a high-purity quartz sand purification process based on oxidation-reduction synergistic modification, including the following steps:

[0060] S1. Using the granite pegmatite-type quartz raw ore produced in a certain place as raw material, after pretreatment of the raw ore, it is wet-ground to a particle size where the proportion of 70 - 200 mesh is ≥ 85%, roasted at 900 °C for 2.5 h, and then quenched and rapidly cooled with water to obtain a first coarse ore with a microcrack structure.

[0061] S2. The first coarse ore with a particle size of 70 - 200 mesh is oxidized and roasted at 400 °C for 3 h under an oxygen concentration of 28% to obtain an oxidized second coarse ore.

[0062] S3. At 600 °C, 3% of the mass of the ore raw material of iron powder is added to the second coarse ore for reduction roasting for 45 min to obtain a third coarse ore with enhanced magnetism.

[0063] S4. The third coarse ore is subjected to magnetic separation with a magnetic field strength of 1.2 T and a pulp flow rate of 0.8 m / s. After removing magnetic impurities, a first concentrate is obtained.

[0064] S5. The first concentrate is at pH = 2, and is subjected to flotation for 1 h using a flotation reagent system consisting of 50 g / t of sodium dodecyl sulfonate, 50 g / t of dodecylamine polyoxyethylene ether, 50 g / t of sodium dibutylnaphthalene sulfonate, 50 g / t of sodium pyrophosphate, 300 g / t of water glass, and 150 g / t of methyl isobutyl carbinol to obtain a second concentrate.

[0065] S6. The second concentrate is acid-leached at 150 °C for 12 h with hydrochloric acid, nitric acid, and hydrofluoric acid (volume ratio 1:0.8:0.1, 800 g / t), and washed 5 times with deionized water. It is heat-treated at 900 °C for 2 h in a hydrogen chloride atmosphere to finally obtain high-purity quartz concentrate.

[0066] Example 5

[0067] This example provides a high-purity quartz sand purification process based on oxidation-reduction synergistic modification, including the following steps:

[0068] S1. Using the granite pegmatite-type quartz raw ore produced in a certain place as the raw material, after pretreatment of the raw ore, it is wet-ground to a particle size where the proportion of particles with a size of 70 - 200 mesh is ≥ 85%, roasted at 1200 °C for 1 h, and then quenched and rapidly cooled with water to obtain the first crude ore with a micro-crack structure.

[0069] S2. Roast the first crude ore with a particle size of 70 - 200 mesh at 800 °C for 1 h under an oxygen concentration of 28% to obtain the second roasted crude ore.

[0070] S3. At 1200 °C, add iron powder accounting for 8% of the mass of the ore raw material to the second crude ore and perform reduction roasting for 75 min to obtain the third crude ore with enhanced magnetism.

[0071] S4. Perform magnetic separation on the third crude ore with a magnetic field strength of 2.4 T and a pulp flow rate of 1.5 m / s. After removing magnetic impurities, the first concentrate is obtained.

[0072] S5. The first concentrate is subjected to flotation at pH = 2 for 1 h using a flotation reagent system consisting of 200 g / t of sodium dodecyl sulfonate, 250 g / t of dodecylamine polyoxyethylene ether, 50 g / t of sodium dibutylnaphthalene sulfonate, 100 g / t of sodium pyrophosphate, 500 g / t of water glass, and 200 g / t of methyl isobutyl carbinol to obtain the second concentrate.

[0073] S6. The second concentrate is acid-leached at 150 °C for 24 h with hydrochloric acid, nitric acid, and hydrofluoric acid (volume ratio 1:1:0.1, 800 g / t), and then washed 5 times with deionized water. Heat-treat it at 1050 °C for 2 h in a hydrogen chloride atmosphere to finally obtain high-purity quartz concentrate.

[0074] Comparative Example 1

[0075] This comparative example provides a high-purity quartz sand purification process. Its preparation steps are the same as those in Example 1, except that oxidation roasting is not carried out. That is, in step S2, the first crude ore with a particle size of 70 - 200 mesh is roasted at 600 °C for 1 h in an inert atmosphere to obtain the second crude ore.

[0076] Comparative Example 2

[0077] This comparative example provides a high-purity quartz sand purification process. Its preparation steps are the same as those in Example 1, except that oxidation-reduction roasting is not carried out. That is,

[0078] S2. Roast the first crude ore with a particle size of 70 - 200 mesh at 600 °C for 1 h in an inert atmosphere to obtain the second crude ore.

[0079] S3. Roast the second crude ore at 1000 °C for 1 h to obtain the third crude ore.

[0080] Comparative Example 3

[0081] This comparative example provides a high-purity quartz sand purification process. The preparation steps are the same as those in Example 1, except that oxidative-reductive roasting is not carried out, and the volume ratio of acids used in acid leaching is 1:1:0.5, that is

[0082] S2. Roast the first coarse ore with a particle size of 70-200 mesh in an inert atmosphere at 600 °C for 1 h to obtain the second coarse ore.

[0083] S3. Roast the second coarse ore at 1000 °C for 1 h to obtain the third coarse ore;

[0084] S4-S5 are the same as those in Example 1,

[0085] S6. Leach the second concentrate with hydrochloric acid, nitric acid, and hydrofluoric acid (volume ratio 1:1:0.5, 800 g / t) at 150 °C for 18 h, and wash it 5 times with deionized water. Heat-treat it in a hydrogen chloride atmosphere at 1050 °C for 2 h to finally obtain quartz concentrate.

[0086] Comparative Example 4

[0087] This comparative example provides a high-purity quartz sand purification process. The preparation steps are the same as those in Example 1, except that reduction roasting is not carried out, that is

[0088] S3. Roast the second coarse ore at 1000 °C for 1 h to obtain the third coarse ore.

[0089] Comparative Example 5

[0090] This comparative example provides a high-purity quartz sand purification process. The preparation steps are the same as those in Example 1, except that the composite flotation reagent is different and sodium dibutylnaphthalenesulfonate is not added, that is

[0091] S5. Float the first concentrate at pH = 2 with a flotation reagent system consisting of 200 g / t of sodium dodecyl sulfonate, 150 g / t of dodecylamine polyoxyethylene ether, 80 g / t of sodium pyrophosphate, 350 g / t of water glass, and 200 g / t of methyl isobutyl carbinol for 1 h to obtain the second concentrate

[0092] Comparative Example 6

[0093] This comparative example provides a high-purity quartz sand purification process. The preparation steps are the same as those in Example 1, except that the composite flotation reagent is different and dodecylamine polyoxyethylene ether is not added, that is

[0094] S5. Float the first concentrate at pH = 2 with a flotation reagent system consisting of 300 g / t of sodium dodecyl sulfonate, 50 g / t of sodium dibutylnaphthalenesulfonate, 80 g / t of sodium pyrophosphate, 350 g / t of water glass, and 200 g / t of methyl isobutyl carbinol for 1 h to obtain the second concentrate.

[0095] Comparative Example 7

[0096] This comparative example provides a high-purity quartz sand purification process. The preparation steps are the same as those in Example 1, except that the composite flotation reagent is different, and sodium dodecyl sulfonate is not added, that is

[0097] S5. The first concentrate is at pH = 2, and is flotated for 1 h with a flotation reagent system of 150 g / t of dodecylamine polyethylene ether, 200 g / t of sodium dibutylnaphthalenesulfonate, 80 g / t of sodium pyrophosphate, 350 g / t of water glass, and 200 g / t of methyl isobutyl carbinol to obtain the second concentrate.

[0098] Performance detection

[0099] The purity of the quartz concentrate products prepared in the examples and comparative examples was analyzed, and the test results are shown in Table 1.

[0100] Table 1 Product purity analysis

[0101]

[0102] As can be seen from Table 1, the technical solution of the present invention combines calcination-water quenching-redox synergistic modification-gradient magnetic separation technology, which can improve the iron removal efficiency of high-purity quartz sand, and thus improve the purity of the prepared quartz concentrate. Among them, through comparative analysis, it can be seen that: in the roasting process, Comparative Example 1 only used reduction roasting without oxidation roasting, resulting in incomplete reduction of weakly magnetic substances such as limonite and chromite, and the iron content was significantly higher than that of the examples and other comparative examples; Comparative Example 2 did not implement redox roasting, and the product iron content was also high due to insufficient conversion of iron elements; although Comparative Example 3 improved the iron impurity removal effect by increasing the acid leaching amount, the use of excessive acid caused significant environmental problems. In the flotation aid system, sodium dibutylnaphthalenesulfonate was not added in Comparative Example 5. Its main function is to assist in optimizing the pulp environment and improving the adsorption efficiency of other reagents through emulsification. Due to the unoptimized pulp environment, the reagent adsorption efficiency decreased, and the product purity was slightly lower than that of the example; the anionic collector of dodecylamine polyethylene ether was missing in Comparative Example 6, resulting in high contents of feldspar elements such as K, Al, and Ca; sodium dodecyl sulfonate was not used in Comparative Example 7, resulting in incomplete removal of free impurities such as Mg and Fe. This verifies the necessity of systematic process design for improving product purity and environmental friendliness.

[0103] 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 principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-purity quartz sand purification process based on synergistic oxidation-reduction modification, characterized in that: It includes the following steps: S1. After the raw ore is pretreated, it is subjected to preliminary roasting to obtain the first rough ore; S2. The first rough ore is subjected to oxidation roasting to obtain the second rough ore; S3. The second rough ore is subjected to reduction roasting to obtain the third rough ore; S4. The third rough ore is subjected to magnetic separation to obtain the first concentrate; S5. The first concentrate is subjected to flotation treatment with a composite flotation reagent under acidic conditions to obtain the second concentrate; S6. The second concentrate is subjected to acid leaching, washing, and heat treatment in sequence under high temperature and high pressure conditions to obtain high-purity quartz sand concentrate.

2. The high-purity quartz sand purification process based on oxidation-reduction synergistic modification according to claim 1, wherein: In step S1, the pretreatment includes grinding the raw ore to a particle size where the proportion of particles with a size of 70 - 200 mesh is ≥ 85%; the temperature of the preliminary roasting is 900 - 1200 °C, and the roasting time is 1 - 2.5 h.

3. A high-purity quartz sand purification process based on oxidation-reduction synergistic modification according to claim 1, characterized in that: In step S2, oxidation roasting is carried out with an oxidant. The temperature of the oxidation roasting is 400 - 800 °C, the time is 1 - 3 h, and the oxidant is oxygen or sodium peroxide.

4. The high-purity quartz sand purification process based on oxidation-reduction synergistic modification according to claim 1, characterized in that: In step S3, reduction roasting is carried out with a reducing agent. The temperature of the reduction roasting is 600 - 1200 °C, the time is 45 - 75 min, the reducing agent is one or more of iron powder, iron carbonate, and coke powder, and the addition amount of the reducing agent is 3 - 8% of the mass of the raw ore.

5. The high-purity quartz sand purification process based on oxidation-reduction synergistic modification as described in claim 1, wherein: In step S4, the magnetic field strength for magnetic separation is 1.2 - 2.4 T, the flow rate of the magnetic separation pulp is controlled at 0.8 - 1.5 m / s, and the magnetic medium uses a multi-layer mesh stainless steel magnetic conductor.

6. The high-purity quartz sand purification process based on oxidation-reduction synergistic modification according to claim 1, characterized in that: In step S5, the composite flotation reagent includes sodium dodecyl sulfonate, dodecylamine polyethylene ether, sodium dibutylnaphthalene sulfonate, sodium pyrophosphate, water glass, and methyl isobutyl carbinol. The flotation treatment time is 30 - 90 min.

7. The high-purity quartz sand purification process based on oxidation-reduction synergistic modification according to claim 6, characterized in that: The addition amount of sodium dodecyl sulfonate is 50 - 200 g / t of the mass of the raw ore, the addition amount of dodecylamine polyethylene ether is 50 - 250 g / t of the mass of the raw ore, the addition amount of sodium dibutylnaphthalene sulfonate is 50 g / t of the mass of the raw ore, the addition amount of sodium pyrophosphate is 50 - 100 g / t of the mass of the raw ore, the addition amount of water glass is 300 - 500 g / t of the mass of the raw ore, and the addition amount of methyl isobutyl carbinol is 150 - 200 g / t of the mass of the raw ore.

8. The high-purity quartz sand purification process based on oxidation-reduction synergistic modification according to claim 6, characterized in that: In step S5, the acidic condition is that the pH is 2, and the pH of the first concentrate is adjusted with HF and / or H2SO4.

9. The high-purity quartz sand purification process based on oxidation-reduction synergistic modification according to claim 1, wherein: In step S6, the solution for acid leaching treatment is a mixture of hydrochloric acid, nitric acid, and hydrofluoric acid in a volume ratio of 1:1 - 0.5:0.1, and the acid leaching treatment time is 12 - 24 h.

10. A high-purity quartz sand purification process based on oxidation-reduction synergistic modification according to claim 1, characterized in that: In step S6, the atmosphere for heat treatment is hydrogen chloride, the temperature of the heat treatment is 900 - 1200 °C, and the heat treatment time is 1 - 2 h.

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