Innovative process-based manufacturing method of rapid-hardening waterproof phosphogypsum material

Abstract

The invention relates to the technical field of building materials, and discloses a rapid-hardening waterproof phosphogypsum material manufacturing method based on an innovative process, which comprises the following steps: S1, gradient neutralization pretreatment: carrying out two-stage reaction on phosphogypsum and a composite neutralizer at 55 + / -2 DEG C, s2, adding a nano composite coagulant: adding the composite coagulant containing aluminum sulfate, triethanolamine and hollow mesoporous nano silicon dioxide into the pretreated material; and S3, multi-scale waterproof treatment: synchronously doping the silane-polymer composite emulsion in a grinding stage. In multi-scale waterproof treatment, alkyl alkoxy silane is hydrolyzed to generate silanol groups, the silanol groups and hydroxyl groups on the surface of gypsum are condensed to form a hydrophobic siloxane film, micropores are filled with styrene-acrylic emulsion, a flexible polymer layer is formed after curing, the hydrophobic siloxane film and the flexible polymer layer construct a composite waterproof barrier, the solid content, the particle size and the glass-transition temperature of the emulsion are matched with a two-step emulsification process, and the waterproof effect is good. Uniform coating of the waterproof agent is ensured, and the waterproof performance of the material is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and specifically to a manufacturing method of a quick-setting waterproof phosphogypsum material based on an innovative process. Background Art

[0002] In the technical field of building materials, with the rapid development of the construction industry, the requirements for the waterproof performance of building materials are increasing day by day. Especially in building scenarios such as underground projects, roof waterproofing, and tunnel linings, the waterproof effect is directly related to the safety and durability of buildings. Currently, a variety of waterproof building materials are widely used in the market, and some of these materials are based on gypsum for waterproof treatment in an attempt to meet the building waterproofing requirements.

[0003] Currently, the preparation process of traditional phosphogypsum-based waterproof building materials is relatively single. Taking common phosphogypsum waterproof mortar as an example, in the existing technology, usually only a certain amount of ordinary waterproof agents such as asphalt emulsion and paraffin emulsion are simply added to phosphogypsum. The action principle of these ordinary waterproof agents is mainly to form a relatively simple covering film on the surface of the phosphogypsum material to block the intrusion of moisture. For example, asphalt emulsion uses the water-repellent property of asphalt to form a continuous asphalt film on the surface of phosphogypsum to try to prevent water penetration; paraffin emulsion fills some pores by attaching paraffin on the pore surface of phosphogypsum to achieve a certain waterproof effect.

[0004] The waterproof barriers of existing waterproof gypsum materials are not stable and efficient enough. The single waterproof component or simple combination of waterproof agents used cannot maintain good waterproof performance in complex building environments for a long time. Summary of the Invention

[0005] In view of the deficiencies of the existing technology, the present invention provides a manufacturing method of a quick-setting waterproof phosphogypsum material based on an innovative process, which solves the problems that the waterproof barriers of existing waterproof gypsum materials are not stable and efficient enough and cannot maintain good waterproof performance in complex building environments for a long time.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A manufacturing method of a quick-setting waterproof phosphogypsum material based on an innovative process, including the following steps:

[0007] S1. Gradient neutralization pretreatment: React phosphogypsum with a composite neutralizing agent in two stages at 55 ± 2°C. The neutralizing agent consists of calcium hydroxide, magnesium oxide, and sodium silicate, and the mass ratio of the three is 6.5:2.8:1;

[0008] S2. Addition of nano-composite accelerating agent: Add a composite accelerating agent containing aluminum sulfate, triethanolamine, and hollow mesoporous nano-silica to the pretreated material. The mass ratio of the three is 9.2:1:1.1, and the dosage is 3.2 ± 0.3% of the dry basis mass;

[0009] S3. Multi-scale waterproof treatment: Synchronously incorporate a silane-polymer composite emulsion during the grinding stage, where the mass ratio of alkylalkoxysilane to styrene-acrylic emulsion is 1:1.2, and the total dosage is 5.5 ± 0.5 wt%.

[0010] Preferably, the gradient neutralization pretreatment includes:

[0011] The first stage: At 55 ± 1 °C, mix phosphogypsum with a mixture of calcium hydroxide and magnesium oxide in a mass ratio of 3:1, stir and react at 250 rpm for 40 ± 5 minutes, and neutralize to pH 5.0 ± 0.2;

[0012] The second stage: Add sodium silicate and heat up to 80 ± 2 °C, react for 20 ± 2 minutes, and the end-point pH is 7.0 ± 0.1.

[0013] Preferably, the preparation method of the hollow mesoporous nano-silica is as follows:

[0014] The molar ratio of the template agent cetyltrimethylammonium bromide to tetraethyl orthosilicate is 1:4.5;

[0015] After calcination at 750 ± 10 °C for 2 hours, it is modified with KH-570 silane coupling agent, the pore diameter is 8.5 ± 1.5 nm, and the BET specific surface area is 420 ± 30 m 2 / g.

[0016] Preferably, the addition method of the composite coagulant is as follows:

[0017] The pH value of the premixed solution of aluminum sulfate and triethanolamine is 3.0 ± 0.2;

[0018] Nano-silica is incorporated in three equal amounts at intervals of 6 ± 0.5 minutes, and the mixing speed is 1000 ± 100 rpm.

[0019] Preferably, in the multi-scale waterproof treatment:

[0020] The solid content of the isooctyltriethoxysilane emulsion is 43 ± 1%;

[0021] The Tg of the styrene-acrylic emulsion is 20 ± 2 °C, and the D50 particle size is 110 ± 10 nm.

[0022] Preferably, the dosage of ammonium ferric citrate added in the neutralization pretreatment stage is 0.8 ± 0.1% of the mass of phosphogypsum.

[0023] Preferably, the specific surface area of the ground product is 500 ± 20 m 2 / kg, and the grinding temperature is controlled at 60 ± 3 °C.

[0024] Preferably, the two-step emulsification process parameters are:

[0025] S1, phosphate emulsifier addition amount 2.5wt%, based on silane emulsion, emulsification time 18±1 minutes;

[0026] S2, shear rate 2500±200rpm, emulsification time 12±1min.

[0027] Preferably, the nano titanium oxide coating has a thickness of 80±10 nm and a spraying rate of 2.5 mL / min.

[0028] Preferably, the nano titanium oxide coating is prepared by a sol-gel method, the precursor of which is a molar ratio of tetrabutyl titanate to ethanol of 1:15, the hydrolysis pH value is controlled at 2.5±0.2, and the curing temperature is 180±5°C.

[0029] Working principle: Gradient neutralization pretreatment principle: The presence of free acid and impurities in phosphogypsum will have a negative impact on the performance of the material. The neutralization reaction is carried out in two stages at 55±2℃. In the first stage, calcium hydroxide and magnesium oxide (mass ratio 3:1) are used to stir and react at 55±1℃ for 40±5 minutes to neutralize the acidic components and adjust the pH to 5.0±0.2 to initially stabilize the gypsum matrix. In the second stage, sodium silicate is added and the temperature is raised to 80±2℃. Sodium silicate not only further neutralizes the residual acidic substances, but also reacts with calcium and magnesium ions to form a calcium silicate / magnesium gel phase, forming a dense network structure, improving the early strength of the material, and adjusting the endpoint pH to 7.0±0.1 to create a suitable alkaline environment for subsequent accelerated coagulation. In addition, ammonium ferric citrate is added at 0.8±0.1% of the mass of phosphogypsum, which can chelate harmful metal ions and reduce the interference of impurities in the reaction.

[0030] Working principle of nanocomposite coagulant: The composite coagulant is composed of aluminum sulfate, triethanolamine and hollow mesoporous nano-silica. As the main coagulant, aluminum sulfate quickly hydrolyzes in an alkaline environment to generate aluminum hydroxide colloid, accelerates the hydration and crystallization of gypsum, and shortens the setting time; triethanolamine is both a dispersant, optimizing the distribution of colloids and preventing local over-coagulation, and a retarding regulator, regulating the exothermic process of the hydration reaction and avoiding material cracking. With its high specific surface area and mesoporous structure, hollow mesoporous nano-silica absorbs hydration products, provides nucleation sites, and promotes uniform hydration reactions. Nano-silica is added in equal amounts three times, with an interval of 6±0.5 minutes, and mixed at a speed of 1000±100rpm to ensure that it is fully dispersed and avoid agglomeration, thereby further improving the efficiency of coagulation.

[0031] Principle of multi-scale waterproof treatment: Silane-polymer composite emulsion is synchronously incorporated during the grinding stage. Among them, alkylalkoxysilane (such as isooctyltriethoxysilane) hydrolyzes to generate silanol groups, which condense with the hydroxyl groups on the surface of gypsum to form a hydrophobic silicone oxide film; styrene-acrylic emulsion fills the micropores of the material and forms a flexible polymer layer after curing. The two cooperate to construct a "rigid-flexible" composite waterproof barrier. The solid content of isooctyltriethoxysilane emulsion is controlled at 43±1%, ensuring film-forming efficiency and fluidity, enabling it to uniformly penetrate into the gaps between gypsum particles; the glass transition temperature (Tg 20±2°C) of the styrene-acrylic emulsion is close to room temperature, and a flexible film is formed after curing, filling micron-sized pores, absorbing external stress through deformation, and preventing brittle cracking of the waterproof layer. The emulsion particles with a D50 particle size of 110±10nm can penetrate into sub-micron pores, enhancing the waterproof effect. The two-step emulsification process (the addition amount of phosphate emulsifier is 2.5wt%, and the shear rate is 2500±200rpm) ensures the stability of the emulsion and realizes the uniform coating of the waterproof agent on the surface of gypsum particles.

[0032] Principle of auxiliary process strengthening: During the grinding process, the material is ground to a specific surface area of 500±20 m 2 / kg, improving the reaction activity of the material; the temperature is controlled at 60±3°C to avoid the destruction of additive performance at high temperatures, ensure efficient grinding, and maintain the uniformity of material quality. Titanium tetrabutoxide precursor is sprayed on the surface of the material by sol-gel method to form a nano-titanium oxide coating (thickness 80±10nm, spraying rate 2.5mL / min). After curing at 180±5°C, a TiO2 layer with photocatalytic function is formed, enhancing the weather resistance and surface self-cleaning ability of the material.

[0033] The present invention provides a method for manufacturing a quick-setting waterproof phosphogypsum material based on an innovative process. It has the following beneficial effects:

[0034] 1. In the multi-scale waterproof treatment of the present invention, alkylalkoxysilane hydrolyzes to generate silanol groups, which condense with the hydroxyl groups on the surface of gypsum to form a hydrophobic silicone oxide film. Styrene-acrylic emulsion fills the micropores and forms a flexible polymer layer after curing. The two construct a composite waterproof barrier, and the solid content, particle size, and glass transition temperature of the emulsion, combined with the two-step emulsification process, ensure the uniform coating of the waterproof agent, significantly improving the waterproof performance of the material.

[0035] 2. Phosphogypsum in the present invention is usually difficult to be efficiently utilized due to many impurities. Through steps such as gradient neutralization pretreatment and addition of a composite coagulant promoter, this process successfully converts phosphogypsum into a high-performance building material, realizing the resource utilization of industrial waste, reducing environmental pollution caused by the accumulation of phosphogypsum, and reducing the dependence on resources such as natural gypsum, which conforms to the concept of green environmental protection development.

[0036] 3. The characteristics of rapid setting, waterproofing, high strength and good durability of the present invention make the phosphogypsum material applicable to a variety of building scenarios, such as underground projects, roof waterproofing, tunnel lining and other projects with high requirements for waterproofing and strength. It can also be applied to rapid construction projects with strict requirements for the setting time of materials, broadening the application fields of phosphogypsum-based materials and providing more high-performance material options for the construction industry.

[0037] 4. In the gradient neutralization pretreatment stage of the present invention, the composite neutralizer reacts to generate calcium silicate, forming a dense network structure, enhancing the early strength of the material. Ammonium ferric citrate chelates harmful metal ions, reduces impurity interference, improves the comprehensive performance of the material, reduces internal defects, enhances the compressive strength. The nano-titanium oxide coating endows the material with photocatalytic function, improves the weather resistance and surface self-cleaning ability, and extends the service life of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a flowchart of the manufacturing method of the rapid-setting waterproof phosphogypsum material based on the innovative process of the present invention;

[0039] Figure 2 is a flowchart of the gradient neutralization pretreatment of the present invention;

[0040] Figure 3 is a flowchart of the preparation method of the hollow mesoporous nano-silica of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] Please refer to the attached Figure 1 - attached Figure 3 , the embodiment of the present invention provides a manufacturing method of a rapid-setting waterproof phosphogypsum material based on an innovative process, including the following steps:

[0043] Gradient neutralization pretreatment: React phosphogypsum with a composite neutralizer in two stages at 55±2°C. The neutralizer consists of calcium hydroxide, magnesium oxide and sodium silicate, and the mass ratio of the three is 6.5:2.8:1;

[0044] Addition of nano-composite coagulant: Add a composite coagulant containing aluminum sulfate, triethanolamine and hollow mesoporous nano-silica to the pretreated material. The mass ratio of the three is 9.2:1:1.1, and the dosage is 3.2±0.3% of the dry basis mass;

[0045] Multi-scale waterproofing treatment: Silane-polymer composite emulsion is simultaneously added during the grinding stage, wherein the mass ratio of alkyl alkoxy silane to styrene acrylic emulsion is 1:1.2, and the total addition amount is 5.5±0.5wt%.

[0046] Specifically, in the gradient neutralization pretreatment, phosphogypsum contains free acid and impurities, which affect the material properties. In the first stage, calcium hydroxide and magnesium oxide (mass ratio 3:1) are used to neutralize the acidic components at 55°C, and the pH is adjusted to 5.0±0.2 to initially stabilize the gypsum matrix. In the second stage, sodium silicate is added and the temperature is raised to 80°C to further neutralize the residual acidic substances. At the same time, sodium silicate reacts with calcium and magnesium ions to form a calcium silicate / magnesium gel phase, forming a dense network structure, improving the early strength of the material, and adjusting the endpoint pH to 7.0±0.1 to provide a suitable alkaline environment for subsequent accelerated coagulation. The addition of ammonium ferric citrate (0.8±0.1%) can chelate harmful metal ions and reduce impurity interference.

[0047] Nanocomposite coagulants work synergistically. Aluminum sulfate, as the main coagulant, quickly hydrolyzes in an alkaline environment to generate Al(OH)3 colloid, accelerating hydration and crystallization of gypsum and shortening the setting time. Triethanolamine (TEA) is used as a dispersant and retarder to optimize the distribution of colloids and avoid local over-setting. Hollow mesoporous nano-silica (pore size 8.5±1.5nm, specific surface area 420±30m 2 / g) adsorbs hydration products through its high specific surface area and mesoporous structure, provides nucleation sites, and promotes uniform hydration reaction. Nano-silica is added in three equal amounts (6 minutes interval, 1000rpm mixing) to ensure that it is fully dispersed, avoid agglomeration, and further improve the efficiency of accelerating coagulation.

[0048] Multi-scale waterproofing treatment mechanism, silane-polymer composite emulsion (total dosage 5.5±0.5wt%) is added simultaneously during the grinding stage. Alkyl alkoxy silane (such as isooctyl triethoxy silane) is hydrolyzed to generate silanol groups, which condense with the hydroxyl groups on the gypsum surface to form a hydrophobic siloxane film; styrene acrylic emulsion (Tg20±2℃) fills the micropores of the material and forms a flexible polymer layer after curing, which cooperates with silane to construct a "rigid-flexible" composite waterproof barrier. The two-step emulsification process (phosphate emulsifier 2.5wt%, shear rate 2500rpm) ensures the stability of the emulsion and realizes the uniform coating of the waterproofing agent on the surface of the gypsum particles.

[0049] Auxiliary process to enhance performance, grinding control: grinding to a specific surface area of 500±20m 2 / kg, improve the reaction activity of the material; the temperature is controlled at 60±3℃ to avoid high temperature damaging the performance of the additives, nano titanium oxide coating: the tetrabutyl titanate precursor (thickness 80±10nm) is sprayed by the sol-gel method, and a photocatalytic TiO2 layer is formed after curing at 180℃ to enhance the material's weather resistance and surface self-cleaning ability.

[0050] Please refer to the appendix Figure 2 , the gradient neutralization pretreatment includes:

[0051] The first stage: at 55 ± 1 °C, mix phosphogypsum with calcium hydroxide and magnesium oxide in a mass ratio of 3:1, stir and react at 250 rpm for 40 ± 5 minutes, and neutralize to pH 5.0 ± 0.2;

[0052] The second stage: add sodium silicate and heat up to 80 ± 2 °C, react for 20 ± 2 minutes, and the end point pH is 7.0 ± 0.1.

[0053] Specifically, the residual acidic components such as free phosphoric acid and fluoride in phosphogypsum will seriously deteriorate the material properties. Calcium hydroxide and magnesium oxide, as alkaline neutralizing agents, preferentially react with free acids to form stable salts such as calcium phosphate and magnesium phosphate. At the same time, Ca 2+ and Mg 2+ released during the neutralization process can partially replace the harmful cations in phosphogypsum (such as Al 3+ and Fe 3+ ), reducing the interference of impurities on the hydration reaction. The mild heating at 55 °C not only accelerates the reaction kinetics but also avoids the dehydration or phase change of gypsum caused by high temperature.

[0054] Sodium silicate dissociates into SiO3 2- under high-temperature alkaline conditions and reacts with the residual Ca 2+ , Mg 2+ in the first stage to form calcium silicate and magnesium silicate gel. Reaction formula: Na2SiO3 + Ca(OH)2 → CaSiO3↓ + 2NaOH. The strong alkalinity of sodium silicate further neutralizes the trace residual acid and regulates the pH of the system to weakly alkaline (7.0 ± 0.1), providing the best pH window for the efficient hydrolysis of the subsequent aluminum sulfate coagulant.

[0055] Please refer to the appendix Figure 3 , the preparation method of hollow mesoporous nano-silica is as follows:

[0056] The molar ratio of the template cetyltrimethylammonium bromide to tetraethyl orthosilicate is 1:4.5;

[0057] After calcination at 750 ± 10 °C for 2 hours, it is modified with KH-570 silane coupling agent, with a pore diameter of 8.5 ± 1.5 nm and a BET specific surface area of 420 ± 30 m 2 / g.

[0058] Specifically, template-guided synthesis is carried out. Using cetyltrimethylammonium bromide (CTAB) as the template, it is mixed with tetraethyl orthosilicate (TEOS) in a molar ratio of 1:4.5. CTAB forms a micelle structure through self-assembly and acts as a mesoporous template to guide the hydrolysis and polycondensation of TEOS, forming an ordered silicate skeleton.

[0059] High-temperature calcination: The precursor is calcined at 750 ± 10 °C for 2 hours to completely decompose the template agent CTAB, while densifying the silica skeleton to form a stable hollow mesoporous structure.

[0060] The addition method of the composite coagulant promoter is as follows:

[0061] The pH value of the premixed solution of aluminum sulfate and triethanolamine is 3.0 ± 0.2;

[0062] Nanosilica is incorporated in three equal amounts at intervals of 6 ± 0.5 minutes, and the mixing speed is 1000 ± 100 rpm;

[0063] In the multi-scale waterproof treatment:

[0064] The solid content of the isooctyltriethoxysilane emulsion is 43 ± 1%;

[0065] The Tg of the styrene-acrylic emulsion is 20 ± 2 °C, and the D50 particle size is 110 ± 10 nm.

[0066] Specifically, aluminum sulfate stable in acidic environment: The acidic condition with pH 3.0 ± 0.2 inhibits the premature hydrolysis of aluminum sulfate, avoids the formation of inert Al(OH)3 precipitate, ensures its existence in the form of soluble ions, and reserves active components for the rapid reaction in the subsequent alkaline environment. The dual functions of triethanolamine (TEA): Dispersing stabilizer: TEA delays the hydrolysis rate of aluminum sulfate by complexing Al 3+ ions, preventing local overcoagulation; Retarding and regulating agent: Regulating the exothermic process of the gypsum hydration reaction to avoid material cracking caused by sudden temperature rise.

[0067] Incorporating in batches to avoid agglomeration: Nanosilica is prone to agglomeration due to its high specific surface area. Incorporating it in three batches (with an interval of 6 minutes each) combined with high-speed shearing (1000 rpm), through mechanical force dispersion and time relaxation effect, gradually breaks the agglomerates to achieve single-particle-level dispersion. Dynamic adsorption optimization: After each incorporation, the nanoparticles are preferentially adsorbed on the uncovered area of the gypsum particle surface to form uniform "nano-anchors", providing nucleation sites for the hydration products. Finally, the dispersion degree of nanosilica reaches more than 95%, the agglomerate size < 200 nm, the coagulation promotion efficiency is increased by 25%, the compressive strength at 2 hours reaches 4.2 MPa, the pore distribution of the material is uniform, the pore diameter is concentrated in the range of 50 - 100 nm, and the penetration risk is reduced.

[0068] Isooctyltriethoxysilane emulsion (solid content 43 ± 1%), chemically bonded hydrophobic layer. After hydrolysis of the silane emulsion, isooctylsilanol is generated, which condenses with the hydroxyl groups (-OH) on the surface of gypsum to form a dense siloxane (Si-O-Si) network, covering the material surface and pore entrances, and the contact angle is increased to more than 125°. Precise control of the solid content: The solid content of 43 ± 1% balances the film-forming efficiency and fluidity, ensuring that the silane uniformly penetrates into the gaps between gypsum particles during the grinding process.

[0069] The glass transition temperature (Tg 20 ± 2 °C) of the styrene-acrylic emulsion is close to room temperature. After curing, a flexible polymer film is formed, filling micron-sized pores and absorbing external stress through deformation to prevent brittle cracking of the waterproof layer. Advantage of nano-scale particle size: Emulsion particles with a D50 particle size of 110 ± 10 nm can penetrate into sub-micron pores, forming a "rigid-flexible combination" composite structure with the silane hydrophobic layer.

[0070] The dosage of ammonium ferric citrate added in the neutralization pretreatment stage is 0.8 ± 0.1% of the mass of phosphogypsum; the specific surface area of the ground product is 500 ± 20 m 2 / kg, and the grinding temperature is controlled at 60 ± 3 °C.

[0071] Specifically, in practical applications, when ammonium ferric citrate is added at 0.8 ± 0.1% of the mass of phosphogypsum, it can effectively fix the harmful impurities in phosphogypsum. On the one hand, it reduces the interference of impurities on subsequent chemical reactions, making the reaction in the gradient neutralization pretreatment stage more stable and efficient. Through synergistic action with composite neutralizing agents such as calcium hydroxide, magnesium oxide, and sodium silicate, it ensures that the pH value of phosphogypsum can accurately reach the set pH value range at each stage. On the other hand, due to the chelation of impurities, after the final forming of the material, it can significantly improve the comprehensive performance of the material, reduce internal defects that may be caused by the presence of impurities, and thus enhance the strength of the rapid-setting waterproof phosphogypsum material, making it perform more excellently under pressure and external force impact.

[0072] If the grinding temperature is too high, some components in phosphogypsum may undergo thermal decomposition or crystal form transformation, affecting the chemical composition and physical properties of the material. The excessive temperature may cause the crystal water in phosphogypsum to be lost prematurely, changing its crystal structure, and thus affecting the setting characteristics and strength of the material. On the contrary, if the temperature is too low, the grinding efficiency will decrease, the energy consumption will increase, and it may not be able to achieve the ideal fineness and dispersion state of the material. Controlling the temperature stably at 60 ± 3 °C can not only ensure the efficient progress of the grinding process but also ensure that the chemical stability and physical properties of phosphogypsum are not damaged, maintaining the quality uniformity of the material, providing a strong guarantee for the subsequent preparation of rapid-setting waterproof phosphogypsum materials with excellent performance.

[0073] In the scale waterproof treatment:

[0074] The solid content of isooctyltriethoxysilane emulsion is 43±1%;

[0075] The Tg of styrene-acrylic emulsion is 20±2 °C, and the D50 particle size is 110±10 nm; the dosage of ammonium ferric citrate added in the neutralization pretreatment stage is 0.8±0.1% of the mass of phosphogypsum.

[0076] Specifically, when the emulsion is mixed with phosphogypsum, as the water gradually volatilizes, the silane molecules begin to undergo hydrolysis and condensation reactions. The ethoxy groups in the silane molecules will gradually hydrolyze into hydroxyl groups, and these hydroxyl groups will condense with each other to form a silicone oxygen polymerization with a three-dimensional network structure. Due to the presence of hydrophobic alkyl groups in its molecular structure, this polymer forms a tight hydrophobic film on the pores and surface of the phosphogypsum material. A high solid content can ensure that a sufficient number of silane molecules participate in the reaction to form a complete and continuous hydrophobic film, effectively preventing the intrusion of external moisture. Moreover, this hydrophobic film has good chemical stability and durability, and can maintain the waterproof performance of the material for a long time.

[0077] The glass transition temperature (Tg) of the styrene-acrylic emulsion is 20±2 °C, which makes it in a moderately soft and elastic state at room temperature. When the styrene-acrylic emulsion is mixed with phosphogypsum, during the curing process of the material, it can form a continuous polymer film between the phosphogypsum particles. Its D50 particle size of 110±10 nm ensures good dispersion of the emulsion particles in the phosphogypsum system, and can be evenly filled in the pores of the phosphogypsum, further refining the pore structure. When encountering moisture, the polymer film formed by the styrene-acrylic emulsion can prevent moisture penetration through physical blocking. At the same time, due to its certain elasticity, it can adapt to the small deformations of the material under different environmental conditions, avoiding waterproof failure caused by cracks due to material deformation, and cooperating with the hydrophobic film formed by the silane emulsion to build an efficient waterproof barrier from different scales, significantly improving the waterproof performance of the material.

[0078] In the neutralization pretreatment stage, ammonium ferric citrate is added at an accurate dosage of 0.8±0.1% of the mass of phosphogypsum. Phosphogypsum usually contains various impurities. Ammonium ferric citrate is an effective chelating agent. Its working principle is based on the coordination groups in its molecular structure that can complex with impurity ions. During the neutralization pretreatment process, the addition of ammonium ferric citrate makes the impurity ions be stably chelated in its molecular structure. On the one hand, this effectively reduces the interference of impurity ions on the reaction between phosphogypsum and the composite neutralizing agent, ensuring that the pH value can be accurately adjusted according to the set stage target during the gradient neutralization pretreatment process, and ensuring the smooth progress of the reaction. On the other hand, by chelating impurities, the problem of reduced material strength and durability caused by heavy metal ions is avoided, thereby improving the overall quality of the rapid-setting waterproof phosphogypsum material, enhancing the performance such as compressive strength and impermeability of the material, and extending the service life of the material.

[0079] The process parameters of the two-step emulsification are as follows:

[0080] S1. The addition amount of phosphate ester emulsifier is 2.5 wt% (based on the silane emulsion), and the emulsification time is 18 ± 1 minute;

[0081] S2. The shear rate is 2500 ± 200 rpm, and the emulsification time is 12 ± 1 minute; the thickness of the nano-titanium oxide coating is 80 ± 10 nm, and the spraying rate is 2.5 mL / min; the nano-titanium oxide coating is prepared by the sol-gel method, and the molar ratio of tetrabutyl titanate to ethanol in its precursor is 1:15, the hydrolysis pH value is controlled at 2.5 ± 0.2, and the curing temperature is 180 ± 5 °C.

[0082] Specifically, for S1, the addition amount of phosphate ester emulsifier is 2.5 wt% (based on the silane emulsion), and the emulsification time is 18 ± 1 minute: In the multi-scale waterproof treatment, the main purpose of the first-step emulsification process is to preliminarily disperse the silane emulsion, laying a foundation for the subsequent formation of a uniform and stable emulsion system. The addition amount of phosphate ester emulsifier is 2.5 wt% of the silane emulsion. The phosphate ester emulsifier has a special amphiphilic structure. One end is a lipophilic group that can interact with the organic components in the silane emulsion, and the other end is a hydrophilic group that enables it to disperse in water. During the emulsification time of 18 ± 1 minutes, the phosphate ester emulsifier gradually wraps the silane emulsion droplets, reducing the surface tension between the emulsion droplets and preventing them from aggregating with each other. In this step, the silane emulsion is preliminarily dispersed into smaller droplets, increasing the surface area of the emulsion, enabling it to come into more sufficient contact and be evenly distributed when subsequently mixed with styrene-acrylic emulsion and reacting with phosphogypsum, thus enhancing the waterproof effect.

[0083] For S1, the shear rate is 2500 ± 200 rpm, and the emulsification time is 12 ± 1 minute: After the first-step emulsification, the degree of dispersion of the emulsion is not yet ideal and further treatment is required. In the second step, a high shear rate of 2500 ± 200 rpm is adopted and maintained for 12 ± 1 minutes. Under the action of high shear force, the emulsion droplets are further refined and dispersed. The powerful force generated by the high-speed rotating shear equipment can break the larger emulsion aggregates formed after the first-step emulsification, making the silane emulsion droplets smaller and more evenly distributed. At the same time, this high shear force can also promote the closer fusion of the silane emulsion and the styrene-acrylic emulsion, enabling the two emulsions to better interpenetrate and intertwine at the microscopic level, forming a more stable and uniform composite emulsion system. Finally, a more dense and effective waterproof network structure is constructed in the phosphogypsum material, significantly enhancing the waterproof performance of the material and effectively preventing water penetration.

[0084] The thickness of the nano-titanium oxide coating is controlled at 80 ± 10 nm. This thickness can not only ensure that the coating has good protective performance but also will not affect other properties of the material due to excessive thickness. The spraying rate is set at 2.5 mL / min to ensure that the nano-titanium oxide solution can uniformly cover the surface of the phosphogypsum material.

[0085] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a rapid-setting waterproof phosphogypsum material based on an innovative process, characterized in that, It includes the following steps: S1. Gradient neutralization pretreatment: React phosphogypsum with a composite neutralizer at 55 ± 2 °C in two stages. The neutralizer consists of calcium hydroxide, magnesium oxide, and sodium silicate, and the mass ratio of the three is 6.5:2.8:1; S2. Addition of nano-composite coagulant: Add a composite coagulant containing aluminum sulfate, triethanolamine, and hollow mesoporous nano-silica to the pretreated material. The mass ratio of the three is 9.2:1:1.1, and the dosage is 3.2 ± 0.3% of the dry basis mass; S3. Multi-scale waterproof treatment: Synchronously incorporate a silane-polymer composite emulsion during the grinding stage. The mass ratio of alkylalkoxysilane to styrene-acrylic emulsion is 1:1.2, and the total dosage is 5.5 ± 0.5 wt%; 2. The manufacturing method of the rapid-setting waterproof phosphogypsum material based on the innovative process according to claim 1, characterized in that, The gradient neutralization pretreatment includes: The first stage: At 55 ± 1 °C, react phosphogypsum with a mixture of calcium hydroxide and magnesium oxide with a mass ratio of 3:1, stir and react at 250 rpm for 40 ± 5 minutes, and neutralize to pH 5.0 ± 0.2; The second stage: Add sodium silicate and raise the temperature to 80 ± 2 °C, react for 20 ± 2 minutes, and the end point pH is 7.0 ± 0.1; 3. The manufacturing method of the quick-setting waterproof phosphogypsum material based on the innovative process according to claim 1, characterized in that, The preparation method of the hollow mesoporous nano-silica is: The molar ratio of the template agent cetyltrimethylammonium bromide to tetraethyl orthosilicate is 1:4.5; After calcination at 750 ± 10 °C for 2 hours, it was modified with KH-570 silane coupling agent, with a pore size of 8.5 ± 1.5 nm and a BET specific surface area of 420 ± 30 m 2 / g.

4. The manufacturing method of the quick-setting waterproof phosphogypsum material based on an innovative process according to claim 1, characterized in that The addition method of the composite coagulant is: The pH value of the premixed solution of aluminum sulfate and triethanolamine is 3.0 ± 0.2; The nano-silica is incorporated in three equal amounts at intervals of 6 ± 0.5 minutes, and the mixing speed is 1000 ± 100 rpm; 5. The manufacturing method of the rapid-setting waterproof phosphogypsum material based on the innovative process according to claim 1, characterized in that, In the multi-scale waterproof treatment: The solid content of the isooctyltriethoxysilane emulsion is 43 ± 1%; The Tg of the styrene-acrylic emulsion is 20 ± 2 °C, and the D50 particle size is 110 ± 10 nm; 6. The manufacturing method of the quick-setting waterproof phosphogypsum material based on the innovative process according to claim 2, characterized in that, The dosage of ammonium ferric citrate added in the neutralization pretreatment stage is 0.8 ± 0.1% of the mass of phosphogypsum; 7. The manufacturing method of the rapid-setting waterproof phosphogypsum material based on an innovative process according to claim 1, characterized in that, The specific surface area of the ground product is 500±20 m 2 / kg, and the grinding temperature is controlled at 60±3 °C.

8. The manufacturing method of the quick-setting waterproof phosphogypsum material based on the innovative process according to claim 5, characterized in that, The process parameters of the two-step emulsification are: S1. The addition amount of the phosphate emulsifier is 2.5 wt%, based on the silane emulsion, and the emulsification time is 18 ± 1 minute; S2. The shear rate is 2500 ± 200 rpm, and the emulsification time is 12 ± 1 minute; 9. The manufacturing method of the quick-setting waterproof phosphogypsum material based on the innovative process according to claim 1, characterized in that, The thickness of the nano-titanium oxide coating is 80 ± 10 nm, and the spraying rate is 2.5 mL / min; 10. The method for manufacturing a rapid-setting waterproof phosphogypsum material based on an innovative process according to claim 9, characterized in that, The nano-titanium oxide coating is prepared by the sol-gel method. The molar ratio of its precursor tetrabutyl titanate to ethanol is 1:15, the hydrolysis pH value is controlled at 2.5 ± 0.2, and the curing temperature is 180 ± 5 °C;

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