Method for preparing type II anhydrite by utilizing phosphogypsum and application of type II anhydrite
By treating phosphogypsum with polycarboxylic acid or polyphosphonic acid crystallizing agents and surfactants, the problems of high energy consumption and uneven particle size in the conversion of phosphogypsum to type II anhydrous gypsum were solved, and high-performance anhydrous gypsum was prepared. This gypsum was then applied to composite materials to improve their mechanical properties and reduce energy consumption.
Patent Information
- Application Number
- CN202511061310.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-30
- Publication Date
- 2025-11-14
AI Technical Summary
The existing technology for converting phosphogypsum into type II anhydrous gypsum has problems such as high energy consumption, residual impurities, large and uneven particle size, and small specific surface area, which affect its high-value utilization.
By treating phosphogypsum under hydrothermal conditions with polycarboxylic acid or polyphosphonic acid crystallizing agents and surfactants, and by controlling the crystal growth rate and morphology, type II anhydrous gypsum with uniform particle size and large specific surface area was prepared.
The prepared type II anhydrous gypsum has uniform particle size and large surface area, and can be used in large quantities in polymers to improve the mechanical properties of composite materials and reduce energy consumption and pollution, which is in line with the green and low-carbon goals.
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Figure CN120943549A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of high-value utilization technology of solid waste, and in particular to a method for preparing type II anhydrous gypsum using phosphogypsum, and the application of type II anhydrous gypsum in the preparation of composite materials. Background Technology
[0002] Phosphogypsum is a major solid waste product of the wet-process phosphoric acid industry. As the world's largest producer of phosphate chemicals, my country's annual phosphogypsum production exceeds 70 million tons, with accumulated stockpiles exceeding 600 million tons. This industrial byproduct contains harmful components such as soluble phosphorus, fluorine, organic matter, and heavy metals. Long-term stockpiling not only occupies vast amounts of land resources but also leads to soil acidification and groundwater pollution. Resource utilization of phosphogypsum can not only facilitate its large-scale disposal but also reduce its environmental impact.
[0003] Converting phosphogypsum into type II anhydrous gypsum is an important direction for its high-value utilization. Type II anhydrous gypsum can be widely used as a filler in self-leveling mortars, plastics and coatings, and for soil improvement. Traditional methods for preparing type II anhydrous gypsum mainly involve calcination and acidification, but these methods suffer from high energy consumption, residual impurities, and suboptimal performance. Therefore, a new green and low-energy-consumption preparation process is urgently needed. Furthermore, current type II anhydrous gypsum prepared from phosphogypsum faces challenges such as large and uneven particle size and small specific surface area. New processes are needed to control its particle size, ensuring uniform distribution at the nano- and micro-scale while achieving a larger specific surface area. This structural characteristic is particularly important for the high-value utilization of type II anhydrous gypsum, such as achieving large-scale addition in polymers or resins. Summary of the Invention
[0004] In view of this, the present invention proposes a method and application for preparing type II anhydrous gypsum using phosphogypsum, to solve the problems of high energy consumption, impurity residue, and large particle size, uneven distribution, and small specific surface area of the prepared type II anhydrous gypsum product faced by the method of converting phosphogypsum into type II anhydrous gypsum; at the same time, it also provides the application of the above-mentioned type II anhydrous gypsum in the preparation of composite materials, which effectively improves the performance of composite materials.
[0005] The technical solution of this invention is implemented as follows:
[0006] On one hand, the present invention provides a method for preparing type II anhydrous gypsum using phosphogypsum, comprising the following steps: adding a crystallization agent, an alkalinity regulator, a surfactant and water to phosphogypsum, reacting under hydrothermal conditions and then filtering, and drying the resulting solid under vacuum to obtain anhydrous gypsum; wherein the crystallization agent comprises at least one of 1,3,5-triazine-2,4,6-triaminehexaacetic acid and 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid;
[0007] The structure of the 1,3,5-triazine-2,4,6-triaminehexaacetic acid is shown in Formula I:
[0008]
[0009] The structure of the 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid is shown in Formula II:
[0010]
[0011] Based on the above scheme, preferably, the amount of the crystallization agent added is 0.05 to 1 wt% of phosphogypsum; more preferably, the amount of the crystallization agent added is 0.5 wt%.
[0012] Based on the above scheme, the preferred method for synthesizing the crystallization agent 1,3,5-triazine-2,4,6-triaminehexaacetic acid includes: weighing 1 part cyanuric chloride, 5 parts iminodiacetic acid, and 7 parts sodium carbonate by mass and adding them to 60 parts 1,4-dioxane, reacting at 60°C for 4 hours, then filtering out sodium carbonate, and distilling the filtrate under reduced pressure to obtain the solid 1,3,5-triazine-2,4,6-triaminehexaacetic acid.
[0013] Based on the above scheme, preferably, the synthesis method of the crystallization agent 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid includes: weighing 1 part cyanuric chloride, 4.5 parts iminodimethylphosphonic acid, and 6 parts sodium carbonate by mass and adding them to 60 parts 1,4-dioxane, reacting at 60°C for 4 hours, then filtering out sodium carbonate, and distilling the filtrate under reduced pressure to obtain the solid 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid.
[0014] Polycarboxylic acid or polyphosphonic acid crystallizing agents are used to control the crystallization of phosphogypsum into anhydrous gypsum. Their molecular structure has a high content of carboxylic acid or phosphonic acid groups and a symmetrical distribution. When they extend in three dimensions, they can be adsorbed on various crystal surfaces of gypsum and combine with water molecules. At the same time, they affect the crystallization behavior of calcium ions and sulfate ions, forming a uniform and regular anhydrous gypsum crystal phase, which plays a role in inhibiting the crystal growth rate from being too fast.
[0015] Based on the above scheme, preferably, the alkalinity regulator is one or more of sodium hydroxide solution, sodium carbonate solution, triethylamine, ammonia, ammonium carbonate solution, and ammonium bicarbonate solution; the surfactant is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and fatty alcohol polyoxyethylene ether; more preferably, the alkalinity regulator is sodium hydroxide solution, and the surfactant is fatty alcohol polyoxyethylene ether.
[0016] This indicates that the surfactant can uniformly disperse calcium ions and sulfate ions in the solvent, ensuring that the contact between anions and cations can proceed evenly, thereby promoting the crystal growth rate of the crystal conversion agent to inhibit excessive crystal growth.
[0017] Based on the above scheme, preferably, the concentration of the alkaline regulator is 0.15–1.5 mol / L, and the addition amount is 2–8 wt% of phosphogypsum; the addition amount of the surfactant is 0.25–3 wt% of phosphogypsum; more preferably, the concentration of the alkaline regulator is 1 mol / L, and the addition amount is 5 wt% of phosphogypsum; the addition amount of the surfactant is 2 wt% of phosphogypsum.
[0018] Based on the above scheme, preferably, the solid-liquid ratio of phosphogypsum and water is 1:(1-8); the hydrothermal conditions are a reaction at 100-220℃ for 1-8 hours; more preferably, the solid-liquid ratio of phosphogypsum and water is 1:3; the hydrothermal conditions are a reaction at 100℃ for 8 hours.
[0019] Secondly, the present invention provides a type II anhydrous gypsum, preferably prepared by the above-described method for preparing type II anhydrous gypsum.
[0020] Thirdly, the present invention provides a composite material, preferably containing, by mass, 5 to 40 parts of type II anhydrous gypsum as described above, and 100 parts of polymer and 0.5 to 3 parts of silane coupling agent.
[0021] Based on the above scheme, preferably, the polymer comprises one or more of polypropylene, polyvinyl chloride, and polyethylene; the silane coupling agent comprises one or more of isobutyltriethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane.
[0022] Based on the above scheme, a further optimized method is to take 100 parts by weight of polypropylene, 5 parts of the above-mentioned type II anhydrous gypsum, and 3 parts of isobutyltriethoxysilane, and injection mold them at 160°C to obtain dumbbell-shaped and straight-shaped specimens.
[0023] The method and application of this invention for preparing type II anhydrous gypsum using phosphogypsum have the following advantages over existing technologies:
[0024] (1) This invention provides a method for synthesizing a novel polycarboxylic acid or polyphosphonic acid crystal-transforming agent, which is used to control the crystal-transforming process of phosphogypsum into anhydrous gypsum. Its advantage is that the crystal-transforming agent has a high content of carboxylic acid or phosphonic acid groups in its molecular structure and is symmetrically distributed. When it extends along the three-dimensional direction, it can be adsorbed on each crystal surface of gypsum and combine with water molecules. At the same time, it affects the crystallization behavior of calcium ions and sulfate ions, thereby inhibiting the crystal growth rate from being too fast and forming a uniform and regular anhydrous gypsum crystal phase.
[0025] (2) In this invention, the surfactant can uniformly disperse calcium ions and sulfate ions in the solvent, ensuring that the contact between anions and cations can proceed in a balanced manner, thereby promoting the crystal growth rate of the crystal conversion agent. The surfactant and the crystal conversion agent work synergistically to promote uniform crystal growth and form a stable crystal phase. The effective control of the crystal form of anhydrous gypsum can also change its morphology, thus obtaining anhydrous gypsum with smaller and more uniform particle size. This structure helps to improve the dispersibility of anhydrous gypsum in polymer media. Even at high dosages, it can be well compatible with the matrix, improving the mechanical properties of the prepared composite material.
[0026] (3) The type II anhydrous gypsum prepared in this invention has a particle size D90 of 9.47 μm, a whiteness of 81.39%, a purity of 92.04%, and a specific surface area of 2478.2 m². 2 The moisture content was consistently controlled below 0.36% in multiple repeated tests, meeting the product quality requirements for anhydrous gypsum. Furthermore, its small and uniform particle size and large specific surface area indicate that the anhydrous gypsum prepared by this method has high potential activity.
[0027] (4) When the type II anhydrous gypsum prepared by this invention is used in polymers with a large dosage (40%), the tensile properties, bending properties and impact properties of the composite material are all improved, indicating that anhydrous gypsum has high-value application scenarios. While improving the performance of the substrate, it can also significantly reduce its usage cost.
[0028] (5) The present invention uses a green low-temperature hydrothermal synthesis process to convert phosphogypsum into anhydrous gypsum. Compared with the calcination method and the atmospheric pressure acidification method, it can significantly reduce energy consumption and reduce the generation of secondary pollutants, which meets the requirements of the "dual carbon target". Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0030] Figure 1These are sample diagrams of composite materials with different amounts of Type II anhydrous gypsum according to the present invention;
[0031] Figure 2 This is a diagram showing the contact angle test results of the pure polypropylene material formed according to the present invention;
[0032] Figure 3 The image shows the contact angle test results of the composite material formed by 5% type II anhydrous gypsum of the present invention.
[0033] Figure 4 The image shows the contact angle test results of the composite material formed by 40% type II anhydrous gypsum of the present invention. Detailed Implementation
[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0035] In this invention, the main materials such as cyanuric chloride, iminodiacetic acid, and iminodimethylphosphonic acid are analytical grade with a purity of 99%, and are all purchased from Aladdin Reagent (Shanghai) Co., Ltd.
[0036] Example 1: Preparation of crystallization agent
[0037] 1. Synthesis of the crystallization agent 1,3,5-triazine-2,4,6-triaminehexaacetic acid
[0038] Weigh 1 gram of cyanuric chloride, 5 grams of iminodiacetic acid, and 7 grams of sodium carbonate and add them to 60 grams of 1,4-dioxane. React at 60°C for 4 hours, then filter out the sodium carbonate. Distill the filtrate under reduced pressure to obtain the solid 1,3,5-triazine-2,4,6-triaminehexaacetic acid.
[0039] 2. Synthesis of the crystallization agent 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid
[0040] Weigh 1 gram of cyanuric chloride, 4.5 grams of iminodimethylphosphonic acid, and 6 grams of sodium carbonate and add them to 60 grams of 1,4-dioxane. React at 60°C for 4 hours, then filter out the sodium carbonate. Distill the filtrate under reduced pressure to obtain the solid 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid.
[0041] Example 2: Preparation of Type II Anhydrous Gypsum
[0042] Add 5 mL of 1 mol / L sodium hydroxide solution, 0.5 g of 1,3,5-triazine-2,4,6-triaminehexaacetic acid, 2 g of fatty alcohol polyoxyethylene ether, and 300 g of water to 100 g of phosphogypsum. React under hydrothermal conditions at 100 °C for 8 h, then filter. The resulting solid is vacuum dried at 140 °C for 8 h to obtain the type II anhydrous gypsum.
[0043] Example 3: Preparation of Type II Anhydrous Gypsum
[0044] The preparation method in this embodiment is the same as that in Example 2, except that the amount of 1,3,5-triazine-2,4,6-triaminehexaacetic acid added is 0.05 g.
[0045] Example 4: Preparation of Type II Anhydrous Gypsum
[0046] The preparation method in this embodiment is the same as that in Example 2, except that the amount of 1,3,5-triazine-2,4,6-triaminehexaacetic acid added is 1 gram.
[0047] Example 5: Preparation of Type II Anhydrous Gypsum
[0048] The preparation method in this embodiment is the same as that in Example 2, except that 0.5 g of 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid is added.
[0049] Example 6: Preparation of Type II Anhydrous Gypsum
[0050] Add 8 mL of 0.15 mol / L triethylamine solution, 0.5 g of 1,3,5-triazine-2,4,6-triaminehexaacetic acid, 0.25 g of hexadecyltrimethylammonium bromide, and 100 g of water to 100 g of phosphogypsum. React under hydrothermal conditions at 100 °C for 8 h, then filter. The resulting solid is vacuum dried at 140 °C for 8 h to obtain the type II anhydrous gypsum.
[0051] Example 7: Preparation of Type II Anhydrous Gypsum
[0052] Add 2 mL of 1.5 mol / L sodium carbonate solution, 0.5 g of 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid, 3 g of sodium dodecylbenzenesulfonate, and 800 g of water to 100 g of phosphogypsum. React under hydrothermal conditions at 220 °C for 2 h, then filter. The resulting solid is vacuum dried at 140 °C for 8 h to obtain the type II anhydrous gypsum.
[0053] Comparative Example 1: Preparation of Type II Anhydrous Gypsum
[0054] The preparation method in this embodiment is the same as that in Example 2, except that the amount of 1,3,5-triazine-2,4,6-triaminehexaacetic acid added is 0.03 g.
[0055] Comparative Example 2: Preparation of Type II Anhydrous Gypsum
[0056] The preparation method in this embodiment is the same as that in Example 2, except that the amount of 1,3,5-triazine-2,4,6-triaminehexaacetic acid added is 1.2 grams.
[0057] Comparative Example 3: Preparation of Type II Anhydrous Gypsum
[0058] The preparation method in this embodiment is the same as that in Example 2, except that no surfactant is added.
[0059] Verification tests were conducted on the anhydrous gypsum prepared according to Examples 2-7 and Comparative Examples 1-3, and the results are shown in Table 1.
[0060] Table 1. Performance data of type II anhydrous gypsum prepared in Examples 2-7 and Comparative Examples 1-3.
[0061]
[0062] The results showed that, according to the above embodiments, the crystal water prepared could meet the quality requirements of Type II anhydrous gypsum products, and the Type II anhydrous gypsum had high purity and whiteness, with particle size reaching the nano-micro level, which could meet the requirements for use as a high-grade plastic filler. When no surfactant was added, the prepared Type II anhydrous gypsum had a larger particle size, higher crystal water content, and lower purity; when the amount of crystallizing agent added was too low or too high, the performance of the prepared Type II anhydrous gypsum was generally inferior to, or basically equal to, the performance of the Type II anhydrous gypsum in the above embodiments.
[0063] Example 8: Preparation of composite materials
[0064] 1000g of polypropylene, 50g of type II anhydrous gypsum prepared in Example 2, and 30g of isobutyltriethoxysilane were injection molded at 160°C to obtain dumbbell-shaped and straight-strip composite material specimens, as shown below. Figure 1 As shown in Table 2, the mechanical properties of the resulting composite material were tested.
[0065] Example 9: Preparation of composite materials
[0066] This embodiment uses the same preparation method as Example 8, except that 400 grams of type II anhydrous gypsum prepared in Example 2 are added to obtain dumbbell-shaped and straight-strip composite material specimens, such as... Figure 1 As shown in Table 2, the mechanical properties of the resulting composite material were tested.
[0067] Table 2 shows the mechanical properties of composite materials formed by adding different amounts of type II anhydrous gypsum to polypropylene.
[0068]
[0069] Type II anhydrous gypsum was prepared by adding low (5%) and high (40%) amounts of polypropylene, respectively. The resulting composite material was formed by injection molding. Samples are shown below. Figure 1 As shown in Table 2, the tensile, flexural, and impact mechanical properties of the composite material were tested. Table 2 shows that when the addition amount is 5%, the three mechanical properties are significantly improved compared to pure polypropylene; when the addition amount is 40%, although the mechanical properties decrease slightly at lower addition amounts, they are still improved compared to pure polypropylene. This indicates that the Type II anhydrous gypsum prepared in this invention can be used in large quantities in polymers. This is mainly attributed to its uniform particle size distribution and nano-scale particle size, a structural feature that allows it to be uniformly dispersed in polymers without deposition.
[0070] This invention also tests the contact angle of polypropylene composites prepared at different dosages to determine the hydrophobic properties of the composites. For example... Figure 2-4 As shown, pure polypropylene ( Figure 2 The contact angle of the polypropylene is 82.718°, while adding 5% ( Figure 3 ) and 40% Figure 4 After the addition of type II anhydrous gypsum, the contact angles of the composite materials were 90.00 and 87.352, respectively. The contact angles were both larger than those of pure polypropylene, indicating that the hydrophobicity was improved.
[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing type II anhydrous gypsum, characterized in that, Includes the following steps: A crystallizing agent, an alkalinity regulator, a surfactant, and water are added to phosphogypsum, and the mixture is reacted under hydrothermal conditions and then filtered. The resulting solid is then vacuum dried to obtain anhydrous gypsum. The crystallizing agent contains at least one of 1,3,5-triazine-2,4,6-triaminehexaacetic acid and 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid. The structure of the 1,3,5-triazine-2,4,6-triaminehexaacetic acid is shown in Formula I: The structure of the 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid is shown in Formula II:
2. The method for preparing type II anhydrous gypsum as described in claim 1, characterized in that, The amount of the crystallizing agent added is 0.05-1 wt% of phosphogypsum.
3. The method for preparing type II anhydrous gypsum as described in claim 1, characterized in that, The method for synthesizing 1,3,5-triazine-2,4,6-triaminehexaacetic acid includes: weighing 1 part cyanuric chloride, 4-6 parts iminodiacetic acid, and 5-8 parts sodium carbonate by mass and adding them to 40-80 parts 1,4-dioxane, reacting at 30-90°C for 2-6 hours, then filtering out sodium carbonate, and distilling the filtrate under reduced pressure to obtain the solid 1,3,5-triazine-2,4,6-triaminehexaacetic acid.
4. The method for preparing type II anhydrous gypsum as described in claim 1, characterized in that, The method for synthesizing 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid includes: weighing 1 part cyanuric chloride, 3.5-5.5 parts iminodimethylphosphonic acid, and 5-8 parts sodium carbonate by mass and adding them to 40-80 parts 1,4-dioxane; reacting at 30-90°C for 2-6 hours; then filtering out sodium carbonate; and distilling the filtrate under reduced pressure to obtain the solid 1,3,5-triazine-2,4,6-triaminehexamethylphosphonic acid.
5. The method for preparing type II anhydrous gypsum as described in claim 1, characterized in that, The alkalinity regulator is one or more of sodium hydroxide solution, sodium carbonate solution, triethylamine, ammonia, ammonium carbonate solution, and ammonium bicarbonate solution; the surfactant is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and fatty alcohol polyoxyethylene ether.
6. The method for preparing type II anhydrous gypsum as described in claim 5, characterized in that, The concentration of the alkaline regulator is 0.15–1.5 mol / L, and the amount added is 2–8 wt% of phosphogypsum; the amount of the surfactant added is 0.25–3 wt% of phosphogypsum.
7. The method for preparing type II anhydrous gypsum as described in claim 1, characterized in that, The solid-liquid ratio of the phosphogypsum and water is 1:(1-8); the hydrothermal conditions are a reaction at a temperature of 100-220℃ for 1-8 hours.
8. A type II anhydrous gypsum, characterized in that, It is prepared by the method for preparing type II anhydrous gypsum according to any one of claims 1 to 7.
9. A composite material, characterized in that, Based on mass parts, it contains 5 to 40 parts of type II anhydrous gypsum as described in claim 8, and also contains 100 parts of polymer and 0.5 to 3 parts of silane coupling agent.
10. The composite material as described in claim 9, characterized in that, The polymer comprises one or more of polypropylene, polyvinyl chloride, and polyethylene; the silane coupling agent comprises one or more of isobutyltriethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane.