A method for purifying quartz from fluorine-containing solid waste

Abstract

The application relates to the technical field of fluorine-containing solid waste purification quartz, and specifically discloses a dissolution-preventing method for fluorine-containing solid waste purification quartz, which comprises the following processing steps: performing an acid leaching process on minerals and an acid leaching solution at a temperature of 10-90 DEG C, the acid leaching time is 10-80 min, and the solid-liquid ratio of the minerals and the acid leaching solution is 1 kg:(1-3) L; the acid leaching solution is composed of a strong acid solution and a dissolution-preventing agent, the strong acid can dissolve fluorine-containing substances and calcium-containing substances in the minerals but cannot dissolve silicon dioxide, and the coordination ability of the dissolution-preventing agent with fluorine is greater than the coordination ability of fluorine with silicon. The minerals and the acid leaching solution are reacted under specific conditions, so that the fluorine-containing substances and the calcium-containing substances are dissolved but the silicon dioxide is not dissolved, the coordination ability of the dissolution-preventing agent with fluorine is greater than the coordination ability of fluorine with silicon, the generated hydrofluoric acid preferentially reacts with the dissolution-preventing agent, so as to break the continuous chemical reaction of the hydrofluoric acid dissolving silicon and play a role in preventing dissolution.

Description

[0001] The priority basis of this application includes: the invention application filed on September 30, 2021, with application number 2021111612834 and patent title "A method and equipment for preparing quartz from secondary tungsten tailings". Technical Field

[0002] This application relates to the technical field of quartz purification from fluorine-containing solid waste, and more specifically, it relates to a solution-inhibiting method for quartz purification from fluorine-containing solid waste. Background Technology

[0003] Currently, some minerals (such as tungsten ore, fluorite, calcite, cryolite, and ilmenite) and their tailings contain fluorine-containing substances. Solid wastes such as hydrometallurgical slag, flue gas dust, and wastewater / acid precipitates also contain fluorine-containing substances, and often a certain amount or even a large amount of silica. To recycle and reuse fluorine-containing solid waste, it is usually purified to obtain high-purity quartz. The fluorine-containing substances (fluorite, fluorapatite) in fluorine-containing solid waste generally react with strong acids to produce hydrofluoric acid (HF). Hydrofluoric acid can react with silica in quartz and aluminosilicate minerals (such as mica and feldspar) to produce fluorosilicic acid; the relevant chemical reaction equations are as follows:

[0004] 6HF+SiO2=H2SiF6+2H2O; 4HF+SiO2=SiF4+2H2O;

[0005] 3SiF4+3H2O=2H2SiF6+H2SiO3; SiF4+3H2O=H2SiO3+4HF;

[0006] H2SiF6=SiF4+2HF; H2SiO3=Si2O·H2O↓;

[0007] In the process of purifying quartz from fluorine-containing solid waste, the resulting minerals all contain fluorine-containing substances. Therefore, strong acid decomposition or selective acid leaching cannot be used to separate the fluorine-containing substances from the quartz and silica. If strong acid decomposition and selective acid leaching are employed, it is known that the hydrofluoric acid intermediate produced by the reaction of strong acid with fluorine-containing substances can further react with silica, alumina, and silica in aluminosilicates to form fluorosilicic acid. The resulting solution contains fluorosilicic acid and fluorosilicates, making it impossible to obtain high-purity quartz. Furthermore, the presence of fluorosilicic acid and fluorosilicates increases the difficulty of treatment and recycling, sometimes even making treatment and recycling impossible, resulting in high costs for enterprises. Therefore, preventing hydrofluoric acid from dissolving silica has become a critical technical challenge in the process of purifying quartz from fluorine-containing solid waste. Summary of the Invention

[0008] To effectively prevent silica leaching and reduce enterprise costs, this application provides a solution-inhibiting method for purifying quartz from fluorine-containing solid waste.

[0009] The solution-inhibiting method for purifying quartz from fluorine-containing solid waste provided in this application adopts the following technical solution:

[0010] A method for purifying quartz from fluorine-containing solid waste by means of the following steps: leaching minerals and acid leaching solution at a temperature of 30-90℃ for 20-80 minutes, with a solid-liquid ratio of minerals to acid leaching solution of 1 kg:(1-3) L.

[0011] The acid leaching solution consists of a strong acid solution and an inhibitor, with a volume-to-mass ratio of 1L:(25-200)g. The strong acid dissolves fluorine-containing and calcium-containing substances in the minerals but does not dissolve silicon dioxide. The inhibitor has a greater coordination ability with fluorine than with silicon.

[0012] By adopting the above technical solution, the acid leaching solution can dissolve fluorine-containing and calcium-containing substances but not silicon dioxide. Since the coordination ability of the solvent with fluorine is greater than that of fluorine with silicon, the intermediate product hydrofluoric acid preferentially reacts with the solvent to interrupt the continuous chemical reaction of hydrofluoric acid dissolving silicon, thus playing the role of solvent inhibition. At the same time, the product generated does not dissolve silicon dioxide.

[0013] Minerals and acid leaching solutions are mixed in a specific ratio and placed in a specific temperature environment for a certain period of time to allow fluorine-containing and calcium-containing substances to dissolve. The solvent inhibits the continuous chemical reaction of hydrofluoric acid dissolving silicon, effectively preventing the dissolution of silicon dioxide. This results in purified quartz with higher purity and reduces production costs for enterprises.

[0014] Preferably, the solvent is boric acid or borate.

[0015] By adopting the above technical solution and optimizing the selection of the solvent, it is possible to achieve solvent inhibition because fluorine has a stronger coordination ability with boron than with silicon. When fluorine, boron, and silicon are present in the reaction system, hydrofluoric acid first reacts with boric acid or borate to form fluoroboric acid without reacting with silicon dioxide, thus achieving the effect of solvent inhibition.

[0016] Preferably, the strong acid solution is a hydrochloric acid solution or a nitric acid solution.

[0017] By adopting the above technical solution, hydrochloric acid solution and nitric acid solution can dissolve fluorine-containing and calcium-containing substances, which facilitates the separation of fluorine-containing substances from quartz and silicon dioxide, and the reaction generates hydrofluoric acid and corresponding salt substances. The solvent can interrupt the dissolution of hydrofluoric acid from silicon dioxide, so that the purified quartz has a higher purity.

[0018] Preferably, the strong acid solution is a hydrochloric acid solution, and the inhibitory solvent is boric acid.

[0019] By adopting the above technical solution, the selection of strong acid solution is optimized to reduce the production cost of enterprises. This is because when nitric acid solution reacts with fluorine-containing substances, nitric acid is expensive and more corrosive to equipment, and the process of recycling and reusing the generated nitrate is more complicated, resulting in high production costs for enterprises. Therefore, hydrochloric acid is usually chosen as the strong acid solution.

[0020] In addition to considering the inhibitory effect, the processing and recycling costs of the product also need to be taken into account when optimizing the selection of the inhibitory solvent. Since using borate as an inhibitory solvent will introduce new impurity ions, the subsequent recycling and reuse processes will be more complicated, the equipment requirements will be higher, and the production and equipment investment costs of enterprises will increase. Therefore, boric acid is a better choice as an inhibitory solvent.

[0021] Preferably, the volume-to-mass ratio of hydrochloric acid solution to boric acid is 1L:(75-125)g.

[0022] By adopting the above technical solution, the ratio of hydrochloric acid solution to boric acid is further optimized, the anti-dissolution effect of acid leaching solution on minerals is further improved, the dissolution of silica is reduced, and the purity of purified quartz is improved.

[0023] Preferably, the hydrochloric acid concentration is 3-6 mol / L.

[0024] By adopting the above technical solutions, if the hydrochloric acid concentration is too high, its high volatility will have a certain impact on the environment and human health. Moreover, the acid leaching reaction also occurs at a certain temperature, which promotes the volatilization of the hydrochloric acid solution, resulting in greater equipment wear and high enterprise costs. If the hydrochloric acid concentration is too low, it will not be able to completely dissolve fluorine-containing substances, thus failing to achieve the goal of improving the purity of quartz. At the same time, the dissolution rate of fluorine-containing substances is too slow, and the processing time is long, thereby increasing the enterprise's production costs. Optimizing the concentration of the hydrochloric acid solution not only improves the solubility inhibition effect of the acid leaching solution on minerals, but also reduces the enterprise's production costs.

[0025] Preferably, the acid leaching temperature in the acid leaching process is 40-70℃.

[0026] By adopting the above technical solution, the acid leaching temperature is optimized to facilitate the complete dissolution of boric acid, improve the treatment effect of the acid leaching solution, and control production costs. Table 1 shows the solubility of boric acid at different temperatures. At 50℃, the solubility of boric acid in 1L of aqueous solution is 115.4g, while in 1L of acid leaching solution, the optimized addition of solid boric acid results in 75-125g. The solubility of boric acid at different temperatures indicates that when the temperature is below 40℃, the boric acid in 1L of acid leaching solution cannot be completely dissolved. However, higher temperatures increase production costs and also increase the volatility of the hydrochloric acid solution. Therefore, to improve the treatment effect of the acid leaching solution and reduce production costs, controlling the temperature between 40-70℃ is preferable.

[0027] Table 1 Solubility of boric acid at different temperatures

[0028] Solubility (g / %) 5.04 6.72 8.72 11.54 14.81 18.62 23.63 30.38

[0029] Preferably, the acid leaching time in the acid leaching process is 30-60 minutes.

[0030] By adopting the above technical solution, the reaction time of acid leaching is optimized to further control the dissolution of fluorine-containing substances while preventing the dissolution of silicon dioxide, effectively preventing silicon dioxide from being dissolved by hydrofluoric acid and improving the purity of the purified quartz.

[0031] Preferably, in the acid leaching process, the solid-liquid ratio of the mineral to the acid leaching solution is 1 kg:(1-1.4) L.

[0032] By adopting the above technical solution, the solid-liquid ratio of minerals and acid leaching solution is further optimized to facilitate stirring during the reaction. If there is too much mineral, it will increase the difficulty of stirring and will not be conducive to the effective reaction. If there is too much acid leaching solution, the amount of minerals processed in a single batch will be small, increasing the number of processing batches and thus increasing the processing cost of the enterprise. Therefore, it is better to further optimize the solid-liquid ratio to 1kg:(1-1.4)L.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. Acid leaching solutions can dissolve fluorine-containing and calcium-containing substances but not silicon dioxide because fluorine has a stronger coordination ability with boron than with silicon. When fluorine, boron, and silicon are present in the reaction system, hydrofluoric acid first reacts with boric acid or borate to form fluoroboric acid without reacting with silicon dioxide, thus interrupting the continuous chemical reaction of hydrofluoric acid dissolving silicon and acting as a solvent inhibitor. By placing the minerals and acid leaching solutions in a specific ratio at a specific temperature for a certain period of time, the fluorine-containing and calcium-containing substances in the minerals are dissolved, but silicon dioxide is not, resulting in a higher purity of the purified quartz.

[0035] 2. Further optimize the hydrochloric acid solution concentration, acid leaching time, acid leaching temperature, and the solid-liquid ratio of the mineral to the acid leaching solution to better control the leaching of fluorine-containing substances while preventing the leaching of silica, effectively preventing silica from being dissolved by hydrofluoric acid, improving the purity of the purified quartz, and reducing the company's production costs. Detailed Implementation

[0036] The present application will be further described in detail below with reference to the embodiments.

[0037] Example

[0038] Example 1

[0039] A method for purifying quartz from fluorine-containing solid waste using a solvent inhibition process includes the following steps: 10 kg of minerals and 10 L of acid leaching solution are subjected to an acid leaching process at a temperature of 30°C and a stirring speed of 90 rpm for 20 min. The acid leaching solution is prepared by mixing 3 mol / L hydrochloric acid solution and boric acid at a volume-to-mass ratio of 1 L: 25 g. Since the density of 3-6 mol / L hydrochloric acid solution is 1.02-1.1 kg / L, for ease of calculation and representation, the density of the hydrochloric acid solution used in this application is equivalent to 1 kg / L, that is, the mass of 1 L of hydrochloric acid solution is 1 kg. When the acid leaching solution is prepared according to the above ratio, the mass ratio of boric acid to hydrochloric acid solution is 0.025:1, that is, the mass percentage of boric acid in the hydrochloric acid solution is 2.5%, hereinafter referred to as boric acid percentage.

[0040] In the acid leaching solution, boric acid is completely dissolved in the hydrochloric acid solution under certain temperature conditions, and the resulting volume change is negligible. Therefore, the volume of the acid leaching solution used in this application is regarded as the volume of the hydrochloric acid solution, that is, the solid-liquid ratio of the mineral to the acid leaching solution is 1:1.

[0041] The mineral used in this embodiment is secondary tungsten tailings, which are waste tailings from tungsten tailings after re-grinding and re-purification of fluorite and mica. Due to the re-grinding, most of the tailings are very fine-grained, belonging to the category of micro-fine-grained tailings. Furthermore, some of the micro-fine-grained fluorite and mica are intergrowths and have not been individually resolved, making it impossible to further purify quartz through physical beneficiation. The mineral phase analysis of the secondary tungsten tailings is shown in Table 2.

[0042] Table 2

[0043]

[0044] The difference between Examples 2-17 and Example 1 lies in the different conditions. The process conditions for Examples 1-17 are shown in Table 3.

[0045] Table 3 Process conditions for Examples 1-17

[0046] Example 1 1:1 2.5 30 20 3 Example 2 1:1.4 2.5 30 20 3 Example 3 1:3 2.5 30 20 3 Example 4 1:1 7.5 30 20 3 Example 5 1:1 10 30 20 3 Example 6 1:1 12.5 30 20 3 Example 7 1:1 20 30 20 3 Example 8 1:1 10 40 20 3 Example 9 1:1 10 50 20 3 Example 10 1:1 10 70 20 3 Example 11 1:1 10 90 20 3 Example 12 1:1 10 50 30 3 Example 13 1:1 10 50 50 3 Example 14 1:1 10 50 60 3 Example 15 1:1 10 50 80 3 Example 16 1:1 10 50 30 4 Example 17 1:1 10 50 30 6

[0047] Example 18

[0048] The difference from Example 16 is that the secondary tungsten tailings are replaced with fluorite tailings, wherein the fluorite tailings contain 95% quartz, 3% fluorite, 1% feldspar, and 1% mica, and the rest are the same as in Example 16.

[0049] Example 19

[0050] The difference from Example 16 is that hydrochloric acid is replaced with nitric acid, and all other aspects are the same as in Example 16.

[0051] Example 20

[0052] The difference from Example 16 is that boric acid is replaced with sodium borate, otherwise it is the same as Example 16.

[0053] Comparative Example

[0054] Comparative Example 1

[0055] The difference from Example 16 is that the acid leaching solution does not contain boric acid, but otherwise it is the same as Example 16.

[0056] Comparative Example 2

[0057] The difference from Example 16 is that the solid-liquid ratio of the mineral to the acid leaching solution is 1:0.5, while the rest are the same as in Example 16.

[0058] Comparative Example 3

[0059] The difference from Example 16 is that the acid leaching temperature is 5°C and the acid reaction time is 20 min, while the rest are the same as in Example 16.

[0060] Performance testing

[0061] Record the mass of the minerals in Examples 1-20 and Comparative Example 1 before acid leaching as M1, and the mass after acid leaching as M2. The dissolution rate % = (M1-M2)*100% / M1. Calculate the dissolution rate of the minerals. Determine the silica content in Examples 1-20 and Comparative Examples 1-3 according to JC / T1021-2007 "Methods for Chemical Analysis of Non-metallic Minerals and Rocks". Record the dissolution rate and silica content results of Examples 1-20 in Table 4, and the results of Examples 16 and Comparative Examples 1-3 in Table 5.

[0062] Table 4. Experimental results of Examples 1-20

[0063]

[0064] Table 5. Test Results

[0065] Solubility / % 1.44 4.46 0.82 0.22 <![CDATA[SiO2%]]> 99.17 95.16 98.30 97.90

[0066] As can be seen from Examples 1-3 and Table 4, by adjusting the solid-liquid ratio of mineral raw materials to acid leaching solution, increasing the amount of acid leaching solution increases the dissolution rate of minerals, but the purity of silica in the minerals does not improve significantly. This is because the boric acid content is constant, and a larger amount of acid leaching solution is beneficial for the reaction, but the amount of minerals processed in a single batch is small. To process the same amount of minerals, more batches need to be processed, thereby increasing the enterprise's processing costs and the processing cost of recycling waste acid leaching solution for the same amount of minerals. Therefore, a solid-liquid ratio of 1:1 between minerals and acid leaching solution is better.

[0067] As can be seen from Examples 1 and 4-7 and Table 4, the solubility changes very little when the boric acid concentration is between 7.5% and 12.5%, and there is basically no change when it is greater than 12.5%. Adjusting the boric acid ratio to 7.5%-12.5%, that is, optimizing the ratio of hydrochloric acid solution to boric acid, can keep the mineral solubility within the required range, improve the solubility inhibition effect of the acid leaching solution on the mineral, reduce the dissolution of silica, and improve the quality of the obtained product. The optimal boric acid ratio is 10%, that is, the ratio of hydrochloric acid solution to boric acid is 1L:100g.

[0068] As can be seen from Examples 5 and 8-11 and in conjunction with Table 4, when the acid leaching temperature is between 40-70℃, the change in solubility and the purity of silica in the mineral is minimal. At 70℃, the solubility begins to decrease, and at 90℃, the decrease is more significant, and the purity of silica in the mineral also decreases. This is because at higher temperatures, the volatilization of hydrochloric acid leads to a decrease in hydrochloric acid concentration, resulting in some fluorite remaining undissolved. Adjusting the acid leaching temperature to 40-70℃ facilitates complete dissolution of boric acid and shortens the time required for complete dissolution of fluorite, thereby improving the treatment effect of the acid leaching solution and controlling production costs.

[0069] As can be seen from Examples 9 and 12-15, combined with Tables 4 and 7, if the leaching time is less than 30 minutes, the solubility decreases and the purity of silica in the mineral is also low. This is because some fluorite remains undissolved. When the acid leaching time is 30-60 minutes, the change in solubility and the purity of silica in the mineral is minimal. After 60 minutes, the solubility begins to increase. In Example 15, the leaching time was 80 minutes, and the solubility increased significantly, but the purity of silica in the mineral hardly improved, and even slightly decreased. This is because the leaching time was too long, resulting in the dissolution of a small amount of quartz. Therefore, adjusting the acid leaching time to 30-60 minutes helps to further control the dissolution of fluorine-containing substances while preventing the dissolution of silica, effectively preventing silica from being dissolved by hydrofluoric acid. It can be seen that a temperature of 40-70℃ and a time of 30-60 minutes can reduce the production cost of acid leaching. At a temperature of 50℃, a reaction time of 30 minutes is even better.

[0070] As can be seen from Examples 12 and 16-17, and in conjunction with Tables 4 and 7, adjusting the concentration of hydrochloric acid solution not only improves the solubility inhibition effect of the acid leaching solution on minerals, but also reduces the production cost for enterprises. If the hydrochloric acid concentration is too high, although the time required for all fluorite to be dissolved is shortened to a certain extent, the purity of silica in the minerals is not significantly improved. Furthermore, excessively high hydrochloric acid concentrations result in high volatility, which has a certain impact on the environment and human health. Additionally, the acid leaching reaction also occurs at a certain temperature, which promotes the volatilization of the hydrochloric acid solution, leading to greater equipment wear and tear and higher enterprise costs. If the hydrochloric acid concentration is too low, fluorine-containing substances cannot be completely dissolved, thus failing to achieve the goal of improving quartz purity. At the same time, the dissolution rate of fluorine-containing substances is too slow, resulting in a long processing time. Therefore, a 4 mol / L hydrochloric acid solution is preferable.

[0071] As can be seen from Examples 16 and 18, the solubility and silica content of the final product vary depending on the type of raw materials used and their composition. Example 19 replaced hydrochloric acid with nitric acid, and Example 20 replaced boric acid with sodium borate. The solubility and silica content of the products obtained in Examples 19 and 20 were basically the same as those in Example 16. However, in actual production, the products of Examples 19 and 20 are more complex in subsequent recycling processes, resulting in higher costs for enterprises.

[0072] As can be seen from Example 16 and Comparative Example 1, and in conjunction with Table 5, the acid leaching solution of Comparative Example 1 does not contain boric acid, and the solubility of minerals is significantly increased. The hydrofluoric acid generated after the hydrochloric acid reacts with the fluorine-containing substance also reacts with the silica in the quartz, resulting in a lower silica content in the product than in the raw material. Therefore, it cannot achieve the function of inhibiting dissolution, nor can it achieve the purpose of purifying quartz.

[0073] As can be seen from Example 16 and Comparative Example 2, and in conjunction with Table 5, there was too much mineral and too little acid leaching solution in Comparative Example 2. The solid-liquid ratio of the mineral and the acid leaching solution was unbalanced, which not only prevented the impurities in the mineral from being completely dissolved, but also increased the difficulty of stirring due to the large amount of mineral, which was not conducive to the effective progress of the reaction. As a result, the dissolution rate of the mineral was low, and the purity of the obtained quartz product was only slightly improved because the fluorite contained in it was not completely dissolved, which could not achieve the purification purpose desired in this application.

[0074] As can be seen from Example 16 and Comparative Example 3, and in conjunction with Table 5, the acid leaching temperature in Comparative Example 3 was too low, which was not conducive to the reaction. The purity of the quartz obtained was basically the same as that of the mineral before acid leaching, and it could not achieve the expected purpose of dissolving impurities to purify the quartz.

[0075] The calcium fluoride content and calcium fluoride solubility were tested for the secondary tungsten tailings of Example 16 and the minerals obtained after acid leaching, and for the fluorite tailings of Example 18 and the minerals obtained after acid leaching, respectively, to verify the solubility of different fluorine-containing solid wastes after acid leaching. The results are shown in Table 6.

[0076] Table 6

[0077]

[0078] As shown in the table above, the dissolution rate of fluorite in the secondary tungsten tailings after acid leaching reached 99.74%, and the dissolution rate of fluorite in the fluorite tailings after acid leaching reached 99.66%. Within the relevant error range, both can be considered to have been completely dissolved.

[0079] Since the fluorine-containing substances in solid waste are mostly calcium fluoride (fluorite), and the calcium fluoride content varies in different solid wastes, the relevant reactions of calcium fluoride with acid leachate are as follows:

[0080] 2HCl+CaF2=CaCl2+2HF; 4HF+H3BO3=HBF4+3H2O;

[0081] As can be seen from the above reaction equation, the amount of acid leaching solution used is directly proportional to the mass of fluorine-containing substances in the solid to be leached. The higher the content of fluorine-containing substances in the solid, the more acid leaching solution is required. If the mass of fluorine-containing substances in the solid to be leached is high, the following measures can be taken: First, while keeping the boric acid content and hydrochloric acid concentration in the acid leaching solution constant, increase the solid-liquid ratio of the acid leaching solution, i.e., increase the amount of acid leaching solution used; second, while keeping the solid-liquid ratio constant, increase the concentration of hydrochloric acid and the content of boric acid in the acid leaching solution. Taking all factors into consideration, with a constant solid-liquid ratio and a fixed proportion of boric acid, the time required for complete dissolution of calcium fluoride can be obtained by varying the acid leaching temperature, reaction time, and hydrochloric acid concentration.

[0082] To further investigate the time required for complete dissolution of different amounts of calcium fluoride in the above acid leaching process, the following experiment was conducted for verification.

[0083] Experiment on the time required for complete dissolution of calcium fluoride with different concentrations in fluoride-containing solid waste.

[0084] Experimental procedure: Fluorine-containing minerals were subjected to process conditions of hydrochloric acid concentrations of 3 mol / L, 4 mol / L, and 6 mol / L, temperature of 40-70℃, boric acid content of 10%, and solid-liquid ratio of 1:1 (i.e., 1 kg of fluorine-containing minerals to 1 L of hydrochloric acid). The mass of calcium fluoride was varied and recorded as m1, the mass of the minerals as m2, and the calcium fluoride content = m1 * 100% / m2. The experimental results under the above conditions were recorded in Table 7.

[0085] Table 7

[0086]

[0087]

[0088] As shown in Table 7, with a constant solid-liquid ratio and hydrochloric acid concentration, the time required to dissolve the same amount of calcium fluoride decreases with increasing temperature. When the temperature reaches 70℃, the hydrochloric acid solution evaporates rapidly, and at a calcium fluoride content of 6%, the calcium fluoride cannot be completely dissolved. At a constant temperature of 50℃, a higher hydrochloric acid concentration results in a shorter time required for complete dissolution of calcium fluoride and a greater mass of calcium fluoride that can be dissolved. However, higher hydrochloric acid concentrations lead to greater volatility, which has an impact on the environment and human health, and is more corrosive to equipment. This necessitates higher performance and corrosion resistance requirements for equipment, increasing investment in production equipment and costs. In the process of purifying quartz from fluorine-containing solid waste, the fluorine content in the fluorine-containing minerals after physical beneficiation is usually less than 1.5%. Therefore, considering the acid leaching temperature, leaching time, and cost, a solid-liquid ratio of 1:1, a temperature of 50℃, a hydrochloric acid concentration of 4 mol / L, and a reaction time of 30 min are optimal for dissolving calcium fluoride in the fluorine-containing minerals with a content of less than 3%. When the calcium fluoride content in the fluorine-containing minerals is greater than 3%, increasing any one or more of the following four parameters—solid-liquid ratio, temperature, and concentrations of hydrochloric acid and boric acid—is necessary to achieve complete dissolution of the calcium fluoride.

[0089] In the continuous production of quartz purification from fluorine-containing solid waste, the solid waste is subjected to an acid leaching process, and the product after the reaction contains fluoroboric acid. In order to verify that quartz is not dissolved by fluoroboric acid, the following experiment was conducted.

[0090] Experimental verification that fluoroboric acid cannot dissolve quartz

[0091] Experiments were conducted using quartzite (sandy silicate) minerals. The main impurities in quartzite were aluminosilicate and carbonate minerals. The main impurities in the aluminosilicate minerals were feldspar and mica, with mica accounting for 3%. Within mica, SiO2 accounted for approximately 45.2%, Al2O3 for approximately 38.5%, and K2O for approximately 11.8%. It also contained small amounts of Na, Ca, Mg, Ti, Cr, Mn, Fe, and F. The small amount of K was replaced by Na, Ca, Mg, and Fe. The main impurity in the carbonate minerals was calcite (chemical formula CaCO3), followed by dolomite (chemical formula CaCO3·MgCO3).

[0092] Under the production process parameters of 100 kg of quartzite mineral (SiO2: 98.35%), 10% boric acid, 50℃, 30 min reaction time, 1:1 solid-liquid ratio, and 90 rpm stirring speed, 0.663 kg of quartzite mineral was dissolved after acid leaching, with a dissolution rate of 0.66%. The elemental contents of the quartzite mineral before acid leaching, the elemental contents obtained after acid leaching, and the elemental contents in the acid leaching liquid were determined according to JC / T1021-2007 "Methods for Chemical Analysis of Non-metallic Minerals and Rocks". The results are shown in Table 8.

[0093] Table 8

[0094]

[0095] It is known that 0.663 kg of quartzite mineral was dissolved after acid leaching of 100 kg of quartzite mineral. Mica accounts for 3% of the quartzite mineral composition. Assuming that all the dissolved 0.663 kg was mica and the quartz remained undissolved, the mica dissolution rate is: (0.663 kg ÷ 3.0 kg) × 100% = 22.1%. Theoretically, the contents of silica, alumina, and potassium oxide in the quartzite mineral after acid leaching are respectively:

[0096]

[0097] The difference between the actual test result and 98.76% is 0.04%.

[0098]

[0099] The difference between the actual test result of 0.88% and the result itself is 0.03%.

[0100]

[0101] The difference between the actual test result of 0.271% and the actual result is 0.007%.

[0102] The contents of silica, alumina, and potassium oxide in the acid leachate after acid leaching of minerals are as follows:

[0103]

[0104] The difference between the actual test result of 2.984 (g / L) and the result of the test is 0.013 (g / L).

[0105]

[0106] The difference between the actual test result of 2.549 (g / L) and the result of the test is 0.004 (g / L).

[0107]

[0108] The difference between the actual test result of 0.598 (g / L) and the theoretical content is -0.184 (g / L). This is because a small amount of K in mica is replaced by Na, Ca, Mg, Fe, etc., so the actual test result will be slightly lower than the theoretical content.

[0109] The above calculations show that the theoretical contents of silica, alumina, and potassium oxide in the quartzite minerals after acid leaching are basically consistent with the actual test results. Furthermore, the contents of silica, alumina, and potassium oxide in the acid leachate after leaching are also basically consistent with the actual test results. Therefore, it can be concluded that what is actually dissolved by fluoroboric acid in the quartzite minerals is mica, not quartz (SiO2); quartz is not dissolved by fluoroboric acid.

[0110] To further investigate whether higher purity quartz could dissolve, 500g of quartz sample (silica content 99.99%) was tested in a sealed device under the conditions of 90℃, 80min, solid-liquid ratio 1:3, and hydrochloric acid concentration 4mol / L, while the concentration of fluoroboric acid was varied. The results are shown in Table 9.

[0111] Table 9. Solubility of 99.9% pure quartz

[0112]

[0113] The data in Table 5 can be used to determine that...

[0114] Quartz with a silica content of 99.99% used in the experiment was not dissolved by fluoroboric acid under the conditions of 90℃, reaction time of 80 min, solid-liquid ratio of 1.0:3.0, and fluoroboric acid concentration of 6%. When the fluoroboric acid concentration exceeded 6%, the quartz began to dissolve slowly, and the concentration of fluoroboric acid generated under the conditions of this application was less than 6%. This demonstrates that even under the most soluble conditions—90℃, 80 min, and a solid-liquid ratio of 1:3—the quartz sample was not dissolved by fluoroboric acid. Therefore, under even milder dissolution conditions, the quartz products generated during the continuous purification process of quartz in the factory (especially those with high silica content) will not dissolve, thus ultimately yielding high-purity quartz.

[0115] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A solution-inhibiting method for purifying quartz from fluorine-containing solid waste, characterized in that, The process includes the following steps: the mineral and acid leaching solution are subjected to acid leaching at a temperature of 40-70℃ for 30-60 minutes, and the solid-liquid ratio of the mineral to the acid leaching solution is 1 kg: (1-3) L. The acid leaching solution consists of a strong acid solution and an inhibitor, with a volume-to-mass ratio of 1L:(25-200)g. The strong acid dissolves fluorine-containing and calcium-containing substances in the minerals but does not dissolve silica. The inhibitor has a greater coordination ability with fluorine than with silicon. The strong acid solution is a hydrochloric acid solution, and the inhibitor is boric acid.

2. The method for solvent inhibition in the purification of quartz from fluorine-containing solid waste according to claim 1, characterized in that: The volume-to-mass ratio of hydrochloric acid solution to boric acid is 1L:(75-125)g.

3. The method for solvent inhibition in the purification of quartz from fluorine-containing solid waste according to claim 1, characterized in that: The hydrochloric acid concentration is 3-6 mol / L.

4. The method for solvent inhibition in the purification of quartz from fluorine-containing solid waste according to claim 1, characterized in that: In the acid leaching process, the solid-liquid ratio of the mineral to the acid leaching solution is 1 kg:(1-1.4) L.

Images