Method for efficiently separating and enriching silicon dioxide by utilizing phosphogypsum

Abstract

The invention relates to the technical field of ardealite recycling, in particular to a method for efficiently separating and enriching silicon dioxide by utilizing ardealite. According to the method, a phosphogypsum modifier and deionized water are mixed and modified, so that a main phase of phosphorite is modified and converted into a matrix easy to etch, modified ore pulp is subjected to solid-liquid separation after modification, modified phosphogypsum and modified filtrate are obtained, the modified phosphogypsum matrix is leached by adopting a leaching method, silicon-rich slag with relatively high silicon content can be obtained after solid-liquid separation, and the silicon-rich slag with relatively high silicon content can be obtained after solid-liquid separation. The obtained modified liquid and leachate are salt solutions and can be used for subsequent molten salt preparation. According to the method, the impurity silicon element with the maximum proportion in the ardealite can be effectively separated and enriched, so that the content of silicon dioxide in the silicon-rich slag obtained after leaching reaches 90.06%, and efficient resource recycling of valuable impurities in the ardealite is achieved. The method effectively solves the problem of calcium-silicon separation in the comprehensive utilization process of phosphogypsum, and has the advantages of low energy consumption, simple operation process, full recovery and utilization of each component and the like.

Description

Technical Field

[0001] The invention relates to the technical field of phosphogypsum recycling and utilization, and specifically to a method for efficiently separating and enriching silicon dioxide by utilizing phosphogypsum. Background Art

[0002] In the phosphorus chemical industry, the production of phosphate fertilizers must first be prepared with phosphoric acid. The preparation of phosphoric acid is usually carried out by wet processing apatite (Ca5(PO4)3OH) using the sulfuric acid production process. In the preparation process, not only phosphoric acid is generated, but also a large amount of solid waste phosphogypsum is produced. Due to the different proportions of H2SO4 and the etching temperature process in the production process, the obtained phosphogypsum is mainly composed of three different hydrates: anhydrous gypsum (Ca2SO4), hemihydrate gypsum (Ca2SO4·0.5H2O) and dihydrate gypsum (CaSO4·2H2O). However, since most phosphorus chemical companies currently use the dihydrate process to produce wet phosphoric acid, the main component of the by-product PG is dihydrate calcium sulfate (CaSO4·2H2O), and the content is generally more than 80%. For every ton of phosphoric acid produced, about 4 to 5 tons of phosphogypsum will be produced at the same time. In 2023, my country's phosphogypsum emissions exceeded 80 million tons. However, the presence of impurities such as fluorine, phosphorus, and organic matter in phosphogypsum greatly limits the comprehensive recycling and utilization of phosphogypsum. At present, my country's comprehensive utilization rate of phosphogypsum is 55.6%, which is still a certain distance from the "Action Plan for Comprehensive Utilization of Phosphogypsum (PG)" to achieve a comprehensive utilization rate of PG resources of 65% by 2026.

[0003] The comprehensive utilization of phosphogypsum widely involves four major fields: building materials, chemical industry, agriculture and biomedicine. Because of its physical and chemical properties similar to those of natural gypsum, phosphogypsum is widely used in the building materials industry. However, the potential hazards caused by the presence of various impurities lead to unpredictable hazards of various phosphogypsum building products exposed to the environment for a long time. Both the main elements and impurity elements in phosphogypsum have great utilization value, so phosphogypsum can be used in the chemical industry to produce chemical products such as calcium sulfate whiskers, calcium carbonate, ammonium sulfate, etc., and various impurity elements can also be recovered. Therefore, the use of a simple and efficient recovery method to separate and enrich silicon dioxide in phosphogypsum can effectively promote the green development of my country's phosphorus chemical industry.

[0004] The traditional method of recovering valuable impurity elements in phosphogypsum is mainly based on impurity removal methods, which mainly include four categories: physical separation, chemical treatment, thermal treatment, biological leaching and new material synthesis. The physical separation method uses the differences in surface properties and particle density of various impurities in phosphogypsum to treat them by flotation and gravity separation respectively. This method can only remove some impurities that are physically combined with calcium sulfate. Chemical treatment and thermal treatment both use chemical methods to separate impurities, but these two methods often produce other by-products and consume a lot of energy. Due to the long processing time and low maturity of research technology, the biological leaching method and the new material synthesis method have not been promoted and applied. Therefore, the various defects of various impurity separation and enrichment methods currently exist, which greatly restrict the comprehensive utilization of phosphogypsum.

[0005] At present, there are some literatures on the comprehensive utilization of phosphogypsum impurity separation and enrichment resources, such as:

[0006] 1. Patent application CN117861862A discloses a method for simultaneous desiliconization and removal of organic matter by co-reverse flotation of phosphogypsum. The method uses alkyl dimethyl tertiary amine as a co-reverse flotation collector and alcohol as a frother. The flotation reagent can simultaneously remove silicon and organic matter in phosphogypsum within a wide range of pH values, and the process is simple and convenient. After a one-step co-reverse flotation process, the silicon dioxide content in the phosphogypsum can be reduced from 6.261% to 2.36%; the whiteness is increased from 33.88% to 57.85%; the organic matter content can be reduced from 0.74% to 0.054%, solving the technical problems of the prior art that the process is complex, time-consuming, costly, and cannot simultaneously and efficiently remove silicon and organic matter in phosphogypsum. It can be seen that the patent application can effectively remove organic impurities in phosphogypsum after a simple one-step co-reverse flotation. Although this method can also separate part of the silicon dioxide in the phosphogypsum and improve the whiteness, the silicon dioxide removal is not complete. In addition, this method does not recycle the impurities in the phosphogypsum after separation, which results in the generation of waste that harms the environment during the production process. The incomplete separation of impurities in the phosphogypsum also makes it difficult to recycle the phosphogypsum after impurities are removed.

[0007] 2. Patent application CN118598178A discloses a method for efficiently recovering phosphorus and fluorine resources from phosphogypsum. The method uses a process of first releasing crystalline phosphorus and then leaching and recovering to separate and recover phosphorus and fluorine valuable impurities in phosphogypsum. In the stage of releasing crystalline phosphorus, a combination of separation, homogenization, aging, dehydration, heat treatment, grinding, etc. or a combination of the above methods is adopted to promote the release of certain crystalline phosphorus, thereby facilitating the treatment; in the stage of recovering phosphorus and fluorine, the treated phosphogypsum is added to the solution, and the treatment is carried out by mixing, impurity removal, filtration, concentration, etc. or a combination of the above methods, and then a multi-element composite solvent is used to convert the phosphorus and fluorine elements in the treatment liquid into an insoluble or insoluble material rich in phosphorus and fluorine elements, so as to realize the recovery of phosphorus and fluorine resources in the treatment liquid. This method does not produce other liquid or solid by-products, and recovers the phosphorus and fluorine resources therein while achieving the reduction and harmlessness of phosphogypsum. It can be seen that the process of releasing crystalline phosphorus and recovering phosphorus and fluorine adopted in this patent is cumbersome and complicated. At the same time, there are many factors affecting the release of crystalline phosphorus in the treatment methods such as sorting, homogenization, aging, dehydration, heat treatment, grinding, etc. or their combination, which is not conducive to effectively controlling the optimal conditions for the release of crystalline phosphorus, and may also lead to high recovery costs and energy consumption. Secondly, the patent does not give the actual separation rate and product grade, and its generalizability needs to be discussed.

[0008] 3. Patent application CN115780096A discloses a collector for collecting carbon and silicon by reverse flotation, and its preparation method and use. The method uses cyclohexane acid imidazoline derivatives, mineral oil and ether alcohol as collectors to reverse flotate and decarbonize and desiliconize phosphogypsum waste residue. The phosphogypsum waste residue slurry is mixed and stirred with the collector, and reverse flotation operation is performed to obtain silicon-containing carbon tailings and phosphogypsum concentrate. The reverse flotation collector can realize an economical and efficient phosphogypsum mixed flotation and silicon-carbon removal process in a strong acidic environment, which not only improves the grade and whiteness of phosphogypsum, but also ensures a high recovery rate of phosphogypsum, and provides qualified raw materials for the multi-path large-scale utilization of phosphogypsum. According to the application example of the patent application, it can be found that the silicon dioxide content in the phosphogypsum after removal is still more than 2.0%. It can be seen that although the collector used in the patent can separate part of the silicon dioxide in the phosphogypsum, the actual silicon removal effect is not significant, resulting in the difficulty of further resource utilization of the phosphogypsum and the captured silicon dioxide after capture.

[0009] Therefore, how to effectively reduce the energy consumption and product utilization rate at each stage of the phosphogypsum recovery process, and realize the separation of calcium and silicon in phosphogypsum and their high-value utilization, these two key steps have become the key issues in the recycling of phosphogypsum secondary resources. Summary of the invention

[0010] In order to solve the above technical problems existing in the prior art, the present invention provides a method for efficiently separating and enriching silicon dioxide using phosphogypsum, comprising the following steps:

[0011] A method for efficiently separating and enriching silicon dioxide using phosphogypsum comprises the following steps:

[0012] (1) mixing phosphogypsum, a modifier and water to react and wet-modify the phosphogypsum, wherein the modifier is sodium carbonate;

[0013] (2) vacuum filtering the modified slurry of step (1) to separate the modified phosphogypsum from the modified filtrate, thereby obtaining the modified phosphogypsum and the modified filtrate; the modified phosphogypsum is the solid remaining in the funnel after the solid-liquid separation;

[0014] (3) After screening, the modified phosphogypsum of step (2) is added into an acidic solution for leaching. After the leaching is completed, the leached slurry is treated by the method in step (2) to obtain an acid leaching solution and silicon-rich slag.

[0015] Furthermore, in the step (1), the additive and water are first dissolved in water to prepare a modified solvent, and then the phosphogypsum is dissolved in the modified solvent for a modification reaction, the concentration of the modified solvent is 0.40 to 0.50 mol / L, and the distribution ratio of the phosphogypsum to the modified solvent is 1:13 to 1:17 g / mL.

[0016] Furthermore, in step (1), the modification conditions are: modification temperature is 10-40°C (room temperature), reaction time is 40-80min, and stirring rate is 275-325rpm.

[0017] Furthermore, in step (2), the main component of the modified phosphogypsum is calcium carbonate, and the modified filtrate is a sodium sulfate salt solution.

[0018] Furthermore, in step (2), the vacuum filtration is carried out under the condition of 0.04-0.06 MPa vacuum until the solid and liquid in the modified slurry are completely separated, and the modified phosphogypsum is dried, for example, in a blast drying oven at 80° C. for 12 hours.

[0019] Furthermore, in the step (3), the modified phosphogypsum is sieved to a mesh size of 200 meshes.

[0020] Furthermore, in step (3), the acid solution is a hydrochloric acid solution and the leaching solution is a calcium chloride salt solution.

[0021] Furthermore, in step (3), the leaching conditions are as follows: leaching temperature of 75-82°C, leaching time of 30-150min, leaching slurry solid-liquid ratio of 1:(1-20)g / mL, hydrochloric acid solution concentration of 2-3mol / L, and stirring rate of 285-310rpm.

[0022] The present invention promotes the separation of calcium and sulfur in phosphogypsum by reacting a sodium carbonate modifier with phosphogypsum in an aqueous solution, realizes the modification of the calcium sulfate phase in the phosphogypsum into an easily eroded calcium carbonate phase, and realizes the effective separation of calcium and silicon in the modified phosphogypsum after leaching the modified phosphogypsum with hydrochloric acid, and obtains silicon-rich slag and calcium-rich leachate with a silicon dioxide content greater than 90.06%. The "modification-leaching" process adopted by the method greatly improves the separation and enrichment of silicon dioxide in phosphogypsum, so that the impurities in the phosphogypsum can be used at a high value.

[0023] Compared with the prior art, the technical effects created by the present invention are embodied in:

[0024] (1) In order to solve the above-mentioned defects, the present invention mixes phosphogypsum, a modifier and water for reaction. The solution is carried out at room temperature during the entire modification process. During the modification reaction, by controlling the added concentration of the modifier, the stable calcium sulfate in the phosphogypsum can be fully converted into an easily corroded calcium carbonate matrix, effectively reducing the separation and enrichment of valuable impurities in the phosphogypsum, and reasonably controlling the production risk, energy consumption and cost of the resource utilization of phosphogypsum.

[0025] (2) The present invention can effectively promote the modification of calcium sulfate matrix in phosphogypsum by reasonably controlling the solid-liquid ratio of the modification reaction, so that calcium and sulfur in calcium sulfate can be effectively separated, thereby improving the overall separation and enrichment efficiency. For example, under the condition of a solid-liquid ratio of 1:10, it takes 90 minutes to completely modify calcium sulfate in phosphogypsum; but when the solid-liquid ratio is 1:15, it takes only 60 minutes for calcium sulfate in phosphogypsum to completely modify.

[0026] (3) The present application reasonably controls the concentration of leaching hydrochloric acid so that calcium can completely enter the solution during the leaching process of the modified phosphogypsum, fully realizing the separation of calcium and silicon, effectively improving the separation efficiency of silicon dioxide in the modified phosphogypsum while enriching it, thereby avoiding the reduction of the separation and enrichment efficiency of silicon dioxide due to insufficient leaching acid.

[0027] (4) This application effectively promotes the modification and transformation of the calcium sulfate matrix in phosphogypsum by adding a modifier, so that calcium and sulfur can be simply separated, and hydrochloric acid leaching is used to basically completely separate calcium and silicon, thereby realizing the separation and subsequent utilization of each valuable component in phosphogypsum. The "modification-leaching" separation and enrichment process is adopted, so that the silicon dioxide content in the leached silicon-rich slag accounts for 90.06%, which effectively solves the problem of calcium-silicon separation in the comprehensive utilization of phosphogypsum, and has the advantages of low energy consumption, simple operation process, and full recycling of each component. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further defined below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0030] The present application example uses phosphogypsum produced in the production process of a factory in Guizhou, and analyzes its chemical composition, and the mass fractions of its components are shown in the following Table 1:

[0031] Table 1 Chemical composition and content of phosphogypsum

[0032] Element CaO <![CDATA[SO3]]> <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[P2O5]]> <![CDATA[Fe2O3]]> F <![CDATA[Na2O]]> other Content (wt%) 38.03 54.05 3.58 0.76 1.26 0.48 1.06 0.12 0.66

[0033] Table 2 Raw material dosage, additives and leaching acid concentration of Examples 1 to 5

[0034] Phosphogypsum(g) Sodium carbonate concentration (mol / L) Hydrochloric acid concentration (mol / L) Example 1 100 0.35 3 Example 2 100 0.45 3 Example 3 100 0.55 3 Example 4 100 0.45 2 Example 5 100 0.55 2

[0035] Example 1

[0036] A method for efficiently separating and enriching silicon dioxide using phosphogypsum comprises the following steps:

[0037] (1) mixing phosphogypsum, a modifier and a certain amount of water to react and wet-modify the phosphogypsum;

[0038] (2) vacuum filtration is used to separate the modified phosphogypsum from the modified filtrate of step (1), thereby obtaining modified phosphogypsum and modified filtrate; the modified phosphogypsum is the solid remaining in the funnel after solid-liquid separation; the vacuum filtration is carried out under the condition of a vacuum degree of 0.04 to 0.06 MPa until the solid and liquid in the modified slurry are completely separated, and the modified phosphogypsum is sent to a forced air drying oven and dried at 80° C. for 12 h;

[0039] (3) After screening, the modified phosphogypsum obtained in step (2) is added into an acidic solution for leaching, and after the leaching is completed, the leached slurry is treated by the method in step (2) to obtain an acid leaching solution and silicon-rich slag;

[0040] Furthermore, in step (1), the modifier is sodium carbonate, and the phosphogypsum, additives and water are prepared by first dissolving the additives in water to prepare a modified solvent, and then dissolving the phosphogypsum in the modified solvent for modification reaction, the concentration of the modified solvent is 0.35 mol / L, the distribution ratio of phosphogypsum to the modified solvent is 1:17 g / mL, and the modification conditions are: modification temperature is 25°C (room temperature), reaction time is 60 min, and stirring rate is 285-315 rpm; in step (2), the main component of the modified phosphogypsum is calcium carbonate, and the modified filtrate is a sodium sulfate salt solution; in step (3), the modified phosphogypsum is sieved to a mesh number of 200 mesh, the acid solution is a hydrochloric acid solution, and the leaching solution is a calcium chloride salt solution. The leaching conditions are: leaching temperature is 82-88°C, leaching time is 60 min, leaching pulp solid-liquid ratio is 1:10 g / mL, hydrochloric acid solution concentration is 3 mol / L, and stirring rate is 295-310 rpm.

[0041] Example 2

[0042] A method for efficiently separating and enriching silicon dioxide using phosphogypsum comprises the following steps:

[0043] (1) mixing phosphogypsum, a modifier and a certain amount of water to react and wet-modify the phosphogypsum;

[0044] (2) vacuum filtration is used to separate the modified phosphogypsum from the modified filtrate of step (1), thereby obtaining modified phosphogypsum and modified filtrate; the modified phosphogypsum is the solid remaining in the funnel after solid-liquid separation; the vacuum filtration is carried out under the condition of a vacuum degree of 0.04 to 0.06 MPa until the solid and liquid in the modified slurry are completely separated, and the modified phosphogypsum is sent to a forced air drying oven and dried at 80° C. for 12 h;

[0045] (3) After screening, the modified phosphogypsum obtained in step (2) is added into an acidic solution for leaching, and after the leaching is completed, the leached slurry is treated by the method in step (2) to obtain an acid leaching solution and silicon-rich slag;

[0046] Furthermore, in step (1), the modifier is sodium carbonate, and the phosphogypsum, additives and water are prepared by first dissolving the additives in water to prepare a modified solvent, and then dissolving the phosphogypsum in the modified solvent for modification reaction, the concentration of the modified solvent is 0.45 mol / L, the distribution ratio of the phosphogypsum to the modified solvent is 1:15 g / mL, and the modification conditions are: modification temperature is 25°C (room temperature), reaction time is 60 min, and stirring rate is 275-305 rpm; in step (2), the main component of the modified phosphogypsum is calcium carbonate, and the modified filtrate is a sodium sulfate salt solution; in step (3), the modified phosphogypsum is sieved to a mesh number of 200 mesh, the acid solution is a hydrochloric acid solution, and the leaching solution is a calcium chloride salt solution, and the leaching conditions are: leaching temperature is 83-86°C, leaching time is 60 min, leaching pulp solid-liquid ratio is 1:10 g / mL, hydrochloric acid solution concentration is 3 mol / L, and stirring rate is 280-305 rpm.

[0047] Example 3

[0048] A method for efficiently separating and enriching silicon dioxide using phosphogypsum comprises the following steps:

[0049] (1) mixing phosphogypsum, a modifier and a certain amount of water to react and wet-modify the phosphogypsum;

[0050] (2) vacuum filtration is used to separate the modified phosphogypsum from the modified filtrate of step (1), thereby obtaining modified phosphogypsum and modified filtrate; the modified phosphogypsum is the solid remaining in the funnel after solid-liquid separation; the vacuum filtration is carried out under the condition of a vacuum degree of 0.04 to 0.06 MPa until the solid and liquid in the modified slurry are completely separated, and the modified phosphogypsum is sent to a forced air drying oven and dried at 80° C. for 12 h;

[0051] (3) After screening, the modified phosphogypsum obtained in step (2) is added into an acidic solution for leaching, and after the leaching is completed, the leached slurry is treated by the method in step (2) to obtain an acid leaching solution and silicon-rich slag;

[0052] Further, in step (1), the modifier is sodium carbonate, and the phosphogypsum, additives and water are prepared by first dissolving the additives in water to prepare a modified solvent, and then dissolving the phosphogypsum in the modified solvent for modification reaction, the modified solvent concentration is 0.55 mol / L, the phosphogypsum and the modified solvent distribution ratio is 1:14 g / mL, and the modification conditions are: modification temperature is 25°C (room temperature), reaction time is 60 min, and stirring rate is 295-300 rpm; in step (2), the main component of the modified phosphogypsum is calcium carbonate, and the modified filtrate is a sodium sulfate salt solution; in step (3), the modified phosphogypsum is sieved to a mesh number of 200 mesh, the acid solution is a hydrochloric acid solution, and the leaching solution is a calcium chloride salt solution. The leaching conditions are: leaching temperature is 80-85°C, leaching time is 60 min, leaching pulp solid-liquid ratio is 1:10 g / mL, hydrochloric acid solution concentration is 3 mol / L, and stirring rate is 300-310 rpm.

[0053] Example 4

[0054] A method for efficiently separating and enriching silicon dioxide using phosphogypsum comprises the following steps:

[0055] (1) mixing phosphogypsum, a modifier and a certain amount of water to react and wet-modify the phosphogypsum;

[0056] (2) vacuum filtration is used to separate the modified phosphogypsum from the modified filtrate of step (1), thereby obtaining modified phosphogypsum and modified filtrate; the modified phosphogypsum is the solid remaining in the funnel after solid-liquid separation; the vacuum filtration is carried out under the condition of a vacuum degree of 0.04 to 0.06 MPa until the solid and liquid in the modified slurry are completely separated, and the modified phosphogypsum is sent to a forced air drying oven and dried at 80° C. for 12 h;

[0057] (3) After screening, the modified phosphogypsum obtained in step (2) is added into an acidic solution for leaching, and after the leaching is completed, the leached slurry is treated by the method in step (2) to obtain an acid leaching solution and silicon-rich slag;

[0058] Furthermore, in step (1), the modifier is sodium carbonate, and the phosphogypsum, additives and water are prepared by first dissolving the additives in water to prepare a modified solvent, and then dissolving the phosphogypsum in the modified solvent for modification reaction, the concentration of the modified solvent is 0.45 mol / L, the distribution ratio of the phosphogypsum to the modified solvent is 1:17 g / mL, and the modification conditions are: modification temperature is 25°C (room temperature), reaction time is 60 min, and stirring rate is 280-315 rpm; in step (2), the main component of the modified phosphogypsum is calcium carbonate, and the modified filtrate is a sodium sulfate salt solution; in step (3), the modified phosphogypsum is sieved to a mesh number of 200 mesh, the acid solution is a hydrochloric acid solution, the leaching solution is a calcium chloride salt solution, and the leaching conditions are: leaching temperature is 81-84°C, leaching time is 60 min, leaching pulp solid-liquid ratio is 1:10 g / mL, hydrochloric acid solution concentration is 2 mol / L, and stirring rate is 296-303 rpm.

[0059] Example 5

[0060] A method for efficiently separating and enriching silicon dioxide using phosphogypsum comprises the following steps:

[0061] (1) mixing phosphogypsum, a modifier and a certain amount of water to react and wet-modify the phosphogypsum;

[0062] (2) vacuum filtration is used to separate the modified phosphogypsum from the modified filtrate of step (1), thereby obtaining modified phosphogypsum and modified filtrate; the modified phosphogypsum is the solid remaining in the funnel after solid-liquid separation; the vacuum filtration is carried out under the condition of a vacuum degree of 0.04 to 0.06 MPa until the solid and liquid in the modified slurry are completely separated, and the modified phosphogypsum is sent to a forced air drying oven and dried at 80° C. for 12 h;

[0063] (3) After screening, the modified phosphogypsum obtained in step (2) is added into an acidic solution for leaching, and after the leaching is completed, the leached slurry is treated by the method in step (2) to obtain an acid leaching solution and silicon-rich slag;

[0064] Furthermore, in step (1), the modifier is sodium carbonate, and the phosphogypsum, additives and water are prepared by first dissolving the additives in water to prepare a modified solvent, and then dissolving the phosphogypsum in the modified solvent for modification reaction, the concentration of the modified solvent is 0.55 mol / L, the distribution ratio of phosphogypsum to the modified solvent is 1:16 g / mL, and the modification conditions are: modification temperature is 25°C (room temperature), reaction time is 60 min, and stirring rate is 288-312 rpm; in step (2), the main component of the modified phosphogypsum is calcium carbonate, and the modified filtrate is a sodium sulfate salt solution; in step (3), the modified phosphogypsum is sieved to a mesh number of 200 mesh, the acid solution is a hydrochloric acid solution, the leaching solution is a calcium chloride salt solution, and the leaching conditions are: leaching temperature is 83-87°C, leaching time is 60 min, leaching pulp solid-liquid ratio is 1:10 g / mL, hydrochloric acid solution concentration is 2 mol / L, and stirring rate is 289-302 rpm.

[0065] Comparative Example 1

[0066] The difference from Examples 1 to 5 is that the hydrochloric acid in the leaching stage is replaced by acetic acid, and the other conditions are kept the same as those in Example 2.

[0067] Comparative Example 2

[0068] The difference from Examples 1 to 5 is that the hydrochloric acid in the leaching stage is replaced by nitric acid, and the other conditions are kept the same as those in Example 2.

[0069] Comparative Example 3

[0070] The difference from Examples 1 to 5 is that the sodium carbonate in the modification stage is replaced by sodium phosphate, and the other conditions are kept the same as those in Example 2.

[0071] Comparative Example 4

[0072] The method of Example 1 of patent application CN117861862A (a method for synchronous desiliconization and removal of organic matter by co-reverse flotation of phosphogypsum) utilizes various amine co-reverse flotation collectors and methyl isobutyl carbinol and pine oil frothers to efficiently separate silicon dioxide and organic impurities in phosphogypsum.

[0073] Comparative Example 5

[0074] The reverse flotation collector is mixed with the phosphogypsum slurry and then fed into a flotation machine for reverse flotation desiliconization and decarbonization roughing operations to obtain silicon-carbon tailings 1 and phosphogypsum concentrate 1.

[0075] The methods of Examples 1 to 5 of the present application and Comparative Examples 1 to 5 were used to separate and enrich the valuable impurities in phosphogypsum, and the impurity separation and enrichment effects of different methods on 100 g of phosphogypsum were recorded. The silica separation rate and grade of each method after separation and enrichment are shown in Table 3 below.

[0076] Table 3 Experimental results of different methods for treating 100g phosphogypsum

[0077]

[0078]

[0079] It can be seen from the experimental data in Table 3 that the method of the present application adopts a "modification-leaching" valuable impurity separation and enrichment process. In the process of recovering silicon dioxide, the silicon dioxide separation rate increases with the increase of the concentration of the modified liquid. When the concentration of the leached modified phosphogypsum is increased, the silicon dioxide enrichment effect is more obvious and the grade is improved. When the concentration of the sodium carbonate solution is 0.45 mol / L and the concentration of the modified phosphogypsum leaching acid is 3 mol / L, the silicon dioxide separation rate in the phosphogypsum is 99.86% and the silicon dioxide grade in the obtained silicon-rich slag is 90.06%. Comparing Examples 1 to 5 with Comparative Examples 1 to 5, it can be found that whether replacing a modifier with a weaker alkalinity or replacing a leaching agent with a weaker acidity, the silicon dioxide separation and enrichment effect in the phosphogypsum is weakened.

[0080] In summary, the present application uses a modification method to modify the main phase elements of calcium sulfate phosphogypsum into an easily corroded calcium carbonate matrix, thereby promoting a better separation effect of calcium and sulfur; hydrochloric acid is used to leach the modified phosphogypsum, so that calcium and silicon in the modified phosphogypsum can be efficiently separated, thereby achieving efficient separation and enrichment of silicon dioxide in phosphogypsum, and the silicon dioxide content in the separated silicon-rich slag exceeds 90%. Compared with the traditional separation and enrichment process, this method can not only effectively separate the valuable impurities of silicon dioxide in phosphogypsum, but also enrich them in large quantities, truly realizing the high-value utilization of impurities in phosphogypsum, and effectively solving the problem of calcium-silicon separation in the comprehensive utilization of phosphogypsum, while having the advantages of low energy consumption, simple operation process, and full recycling of each component.

[0081] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A method for efficiently separating and enriching silicon dioxide using phosphogypsum, characterized in that: The steps include: (1) mixing phosphogypsum, a modifier and water to react and wet-modify the phosphogypsum, wherein the modifier is sodium carbonate; (2) vacuum filtering the modified slurry of step (1) to separate the modified phosphogypsum from the modified filtrate, thereby obtaining the modified phosphogypsum and the modified filtrate; The modified phosphogypsum is the solid remaining in the funnel after solid-liquid separation; (3) After screening, the modified phosphogypsum of step (2) is added into an acidic solution for leaching. After the leaching is completed, the leached slurry is treated by the method in step (2) to obtain an acid leaching solution and silicon-rich slag.

2. The method for efficiently separating and enriching silicon dioxide using phosphogypsum according to claim 1, characterized in that: In the step (1), the additive and water are first dissolved in water to prepare a modified solvent, and then the phosphogypsum is dissolved in the modified solvent for a modification reaction, wherein the concentration of the modified solvent is 0.40 to 0.50 mol / L, and the distribution ratio of the phosphogypsum to the modified solvent is 1:13 to 1:17 g / mL.

3. The method for efficiently separating and enriching silicon dioxide using phosphogypsum according to claim 1, characterized in that: In the step (1), the modification conditions are: modification temperature of 10-40° C., reaction time of 40-80 min, and stirring rate of 275-325 rpm.

4. The method for efficiently separating and enriching silicon dioxide using phosphogypsum according to claim 1, characterized in that: In the step (2), the main component of the modified phosphogypsum is calcium carbonate, and the modified filtrate is a sodium sulfate salt solution.

5. The method for efficiently separating and enriching silicon dioxide using phosphogypsum according to claim 1, characterized in that: In the step (2), the vacuum filtration is carried out under the condition of: performing filtration treatment at a vacuum degree of 0.04 to 0.06 MPa until the solid and liquid in the modified slurry are completely separated, and the modified phosphogypsum is dried.

6. The method for efficiently separating and enriching silicon dioxide using phosphogypsum according to claim 1, characterized in that: In the step (3), the modified phosphogypsum is sieved to a mesh size of 200 meshes.

7. The method for efficiently separating and enriching silicon dioxide using phosphogypsum according to claim 1, characterized in that: In the step (3), the acid solution is a hydrochloric acid solution and the leaching solution is a calcium chloride salt solution.

8. The method for efficiently separating and enriching silicon dioxide using phosphogypsum according to claim 1, characterized in that: The leaching conditions of the step (3) are as follows: leaching temperature of 75-82° C., leaching time of 30-150 min, leaching pulp solid-liquid ratio of 1:(1-20) g / mL, hydrochloric acid solution concentration of 2-3 mol / L, and stirring rate of 285-310 rpm.

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