High-content water-resistant phosphogypsum building material and preparation method thereof

Abstract

The present application relates to the technical field of industrial waste residue utilization, and particularly relates to a high-mixing amount water-resistant phosphogypsum building material and a preparation method thereof.A preparation method of a high-mixing amount water-resistant phosphogypsum building material comprises the following steps: uniformly stirring phosphogypsum, nano-silicon dioxide, water and a water reducing agent to prepare a phosphogypsum slurry, and then performing mold curing to obtain a body modified phosphogypsum building material; obtaining a hydrophobic coating and performing waterproof treatment on the surface of the body modified phosphogypsum building material to obtain the high-mixing amount water-resistant phosphogypsum building material; and the raw materials of the hydrophobic coating comprise a silane coupling agent, a solvent, ammonia water and nano-titanium dioxide.The present application improves the hydrophobic property, corrosion resistance, self-cleaning property and antibacterial property of the phosphogypsum building material by means of double modification, and also improves the mechanical property of the phosphogypsum building material.In addition, the present application has high utilization rate of phosphogypsum, is more green and environmentally friendly, and has great practical value and application prospect.

Description

Technical Field

[0001] This invention relates to the field of industrial waste utilization technology, specifically to a high-content water-resistant phosphogypsum building material and its preparation method. Background Technology

[0002] Phosphogypsum is a solid waste residue generated during the treatment of phosphate rock with sulfuric acid in phosphoric acid production. Its main component is CaSO4·2H2O. It contains trace amounts of harmful impurities such as phosphorus, fluorine, organic matter, and silicon dioxide, and the residual phosphoric acid results in high acidity. In the dihydrate wet process for phosphoric acid production, 4-5 tons of phosphogypsum are generated for every ton of phosphoric acid produced. Untreated phosphogypsum stockpiles not only occupy large amounts of land but also cause serious soil, water, and air pollution. Therefore, it is necessary to find rational ways to utilize phosphogypsum. This will not only contribute to the sustainable development of the phosphate fertilizer industry and the high utilization rate of phosphogypsum but also avoid the occupation of valuable land resources and environmental pollution, which is of great significance.

[0003] Phosphogypsum building materials are a new type of low-carbon and environmentally friendly green building material. They possess advantages such as fire resistance, environmental friendliness, recyclability, easy processing, and lightweight. Using industrial waste phosphogypsum as a building material not only maximizes the resource utilization of phosphogypsum and reduces environmental pollution from phosphogypsum stockpiling, but also reduces the use of traditional building materials. However, most research solutions still suffer from low phosphogypsum utilization rates, making it difficult to meet the goal of large-scale, high-value-added resource utilization of phosphogypsum. Furthermore, the strength of phosphogypsum decreases significantly after absorbing water, and phosphogypsum products have a water absorption rate as high as 50%, making them prone to mold and bacterial growth after absorbing water. Therefore, the waterproof performance of phosphogypsum building materials is also crucial.

[0004] Gypsum hydrophobic coatings can improve the water resistance of gypsum building materials, but existing gypsum hydrophobic coatings are not suitable for phosphogypsum. Existing gypsum hydrophobic coatings react with the alkaline substances inside the gypsum through a dehydration and cross-linking reaction. The resulting products block all capillary channels within the gypsum, thus improving hydrophobicity and compressive strength. However, phosphogypsum contains acidic substances such as phosphoric acid and monocalcium phosphate, which affect the reaction between the gypsum hydrophobic coating and phosphogypsum. Furthermore, phosphogypsum contains potassium salts, sodium salts, and organic impurities, which also affect the reaction, increase water demand, weaken the bonding between calcium sulfate dihydrate crystals, prolong the hardening time of the phosphogypsum hardened body, increase porosity, and reduce strength. Therefore, waterproofing agents suitable for ordinary gypsum are not suitable for phosphogypsum. Existing waterproofing agents suitable for phosphogypsum have complex processes and high costs. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of existing phosphogypsum building materials, such as easy mold growth, poor water resistance, poor anti-sticking and anti-fouling properties, and poor mechanical properties, so as to provide a high-dosage water-resistant phosphogypsum building material and its preparation method to solve the above problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a high-content water-resistant phosphogypsum building material includes:

[0008] Phosphogypsum is mixed with nano-silica, water and water-reducing agent to form phosphogypsum slurry, which is then molded and cured to obtain bulk modified phosphogypsum building material.

[0009] The hydrophobic coating is obtained by waterproofing the surface of the bulk-modified phosphogypsum building material;

[0010] The raw materials for the hydrophobic coating include silane coupling agent, solvent, ammonia and nano titanium dioxide.

[0011] Preferably, the mass ratio of the phosphogypsum, nano-silica, water and water-reducing agent is (65-75):(3.2-4.2):(20-30):(0.5-1.5).

[0012] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent; the water reduction rate of the polycarboxylate water-reducing agent is 30%.

[0013] Preferably, the preparation process of the hydrophobic coating is as follows: first, ammonia water is mixed with a solvent, then a silane coupling agent is added and mixed evenly to prepare a mixed solution, then nano-titanium dioxide is added and mixed evenly, and then ammonia is removed by ventilation to obtain the hydrophobic coating.

[0014] Preferably, the silane coupling agent includes, but is not limited to, isobutyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and vinyltriethoxysilane.

[0015] Preferably, the concentration of the ammonia water is 25 wt%; the pH is adjusted by using ammonia water to promote the hydrolysis of the silane coupling agent.

[0016] Preferably, the solvent is anhydrous ethanol.

[0017] Preferably, based on a hydrophobic coating volume of 100 mL, the amount of the silane coupling agent is 1-5 mL, the amount of the ammonia water is 2 mL, the amount of the nano titanium dioxide is 3 g, and the remainder is solvent.

[0018] Preferably, it includes the following steps:

[0019] 1) Add phosphogypsum and nano-silica into a mixer and mix well to obtain a phosphogypsum mixture;

[0020] 2) Add water-reducing agent and water to the phosphogypsum mixture obtained in step 1) and stir evenly to obtain phosphogypsum slurry;

[0021] 3) Pour the phosphogypsum slurry obtained in step 2) into a mold, vibrate and scrape it flat, cure and shape it, and then demold to obtain the modified phosphogypsum building material.

[0022] 4) Waterproofing treatment is applied to the surface of the bulk modified phosphogypsum building material obtained in step 3), and then it is placed at room temperature for curing treatment to obtain a high-dosage water-resistant phosphogypsum building material.

[0023] Preferably, the curing and shaping time is ≥24 hours;

[0024] And / or, the curing treatment lasts for ≥3 hours;

[0025] And / or, the mold is a triple mold with dimensions of 40mm×40mm×160mm;

[0026] And / or, the waterproofing treatment method includes, but is not limited to, spraying;

[0027] And / or, the amount of the hydrophobic coating used is 150 cm³. 2 / mL.

[0028] The present invention also provides a high-dosage water-resistant phosphogypsum building material, which is prepared by the above-mentioned preparation method of the high-dosage water-resistant phosphogypsum building material.

[0029] In this invention, the water-cement ratio of the phosphogypsum slurry is calculated according to GB / T17669.4-1999 "Determination of Physical Properties of Building Gypsum Paste", and is preferably 0.6.

[0030] The technical solution of this invention has the following advantages:

[0031] 1. A method for preparing a high-dosage water-resistant phosphogypsum building material, comprising: mixing phosphogypsum with nano-silica, water, and a water-reducing agent to form a phosphogypsum slurry; molding and curing the slurry to obtain a bulk-modified phosphogypsum building material; obtaining a hydrophobic coating and waterproofing the surface of the bulk-modified phosphogypsum building material; the raw materials of the hydrophobic coating include a silane coupling agent, a solvent, ammonia, and nano-titanium dioxide; by adding a water-reducing agent and nano-silica to the phosphogypsum, the early hydration rate of the phosphogypsum building material can be accelerated, generating more hydration products. Simultaneously, nano-silica has a certain filling effect, which can further improve the microstructure density of the phosphogypsum blocks, thereby improving the impermeability and durability of the phosphogypsum building material; this invention further modifies the bulk-modified phosphogypsum building material through a hydrophobic coating, and the nano-titanium dioxide in the hydrophobic coating can effectively keep the surface of the phosphogypsum building material clean and It inhibits the growth of microorganisms, thus protecting phosphogypsum building materials from mold and bacterial growth. Furthermore, nano-titanium dioxide is easy to produce, non-toxic, and possesses good thermal and chemical stability. It is not consumed during photocatalysis and can act on the surface of high-dosage water-resistant phosphogypsum building materials for a long time. The silane coupling agent in the hydrophobic coating modifies the surface of nano-titanium dioxide, improving the adhesion of the hydrophobic coating while reducing water demand. In addition, the silane coupling agent can construct a micro / nano-layered rough structure similar to the surface of a lotus leaf on the hydrophobic surface, which not only reduces bacterial adhesion but also effectively prevents corrosive ions from penetrating into the coating. Therefore, it can effectively prevent corrosion and biological contamination of high-dosage water-resistant phosphogypsum building materials, further enhancing their waterproof performance and assisting nano-silica in further improving the impermeability and durability of phosphogypsum building materials.

[0032] In addition, the present invention, through a dual modification method, significantly improves the hydrophobicity, corrosion resistance, self-cleaning properties, antibacterial properties, and mechanical properties of phosphogypsum building materials, further expanding the application range of phosphogypsum building materials.

[0033] 2. This invention further improves the utilization rate of phosphogypsum by optimizing the raw material ratio, thereby alleviating the pressure on the resource utilization of phosphogypsum and demonstrating outstanding environmental value. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 This is a physical image of the bulk-modified phosphogypsum building material during the curing and molding process of Embodiment 1 of the present invention;

[0036] Figure 2 This is a physical image of the high-dosage water-resistant phosphogypsum building material prepared in Example 1 of the present invention;

[0037] Figure 3 This is a photograph of the unmodified phosphogypsum building material used in Comparative Example 2 during the curing and molding process.

[0038] Figure 4 This is a physical image of the unmodified phosphogypsum building material from Comparative Example 2. Detailed Implementation

[0039] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0040] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0041] Example 1

[0042] This embodiment provides a method for preparing a high-dosage water-resistant phosphogypsum building material, comprising the following steps:

[0043] 1) Weigh 95 kg of phosphogypsum and 5 kg of nano-silica and put them into a mixer and stir evenly to obtain a phosphogypsum mixture;

[0044] 2) Weigh 75 kg of the phosphogypsum mixture obtained in step 1), then add 1 kg of polycarboxylate superplasticizer and 24 kg of water and stir evenly to obtain a phosphogypsum slurry with a water-cement ratio of 0.6.

[0045] 3) Pour the phosphogypsum slurry obtained in step 2) into a triple mold with dimensions of 40mm×40mm×160mm. Manually lift the mold 3-5cm and vibrate it up and down 10 times, then smooth it. Let it sit for 24 hours to cure and set. Afterward, remove the mold. The modified phosphogypsum building material produced during the curing process is as follows: Figure 1 As shown, no water seepage occurred during the curing and shaping process;

[0046] 4) Measure 2 mL of 25 wt% ammonia water and 97 mL of anhydrous ethanol and mix them. Then add 1 mL of isobutyltriethoxysilane and mix evenly to obtain a mixed solution. Then add 3 g of nano titanium dioxide and place it in a ventilated place with an open magnetic stirrer until the ammonia gas is removed to obtain a hydrophobic coating.

[0047] 5) Apply the hydrophobic coating obtained in step 4) to the surface of the bulk-modified phosphogypsum building material obtained in step 3) for waterproofing treatment. The waterproofing treatment method is spraying, and the spraying amount of the hydrophobic coating is 150cm. 2 / mL, and then cured at room temperature for more than 3 hours to obtain high-dosage water-resistant phosphogypsum building materials, such as Figure 2 As shown.

[0048] Example 2

[0049] This embodiment provides a method for preparing a high-dosage water-resistant phosphogypsum building material, comprising the following steps:

[0050] 1) Weigh 75 kg of phosphogypsum and 4.2 kg of nano-silica and put them into a mixer and stir evenly to obtain a phosphogypsum mixture;

[0051] 2) Add 1.2 kg of polycarboxylate superplasticizer and 30 kg of water to the phosphogypsum mixture obtained in step 1) and stir evenly to obtain a phosphogypsum slurry with a water-cement ratio of 0.6.

[0052] 3) Pour the phosphogypsum slurry obtained in step 2) into a triple mold with a size of 40mm×40mm×160mm, manually lift the mold 3-5cm and shake it up and down 10 times and scrape it flat. Then let it stand for 24 hours to cure and shape before demolding to obtain the body-modified phosphogypsum building material.

[0053] 4) Measure 2 mL of 25 wt% ammonia water and 95 mL of anhydrous ethanol and mix them. Then add 3 mL of γ-glycidyl oxypropyltrimethoxysilane and mix evenly to obtain a mixed solution. Then add 3 g of nano titanium dioxide and place it in a ventilated place with an open mouth and stir magnetically until the ammonia gas is removed to obtain a hydrophobic coating.

[0054] 5) Apply the hydrophobic coating obtained in step 4) to the surface of the bulk-modified phosphogypsum building material obtained in step 3) for waterproofing treatment. The waterproofing treatment method is spraying, and the spraying amount of the hydrophobic coating is 150cm. 2 / mL, and then placed at room temperature for curing treatment for more than 3 hours to obtain high-dosage water-resistant phosphogypsum building materials.

[0055] Example 3

[0056] This embodiment provides a method for preparing a high-dosage water-resistant phosphogypsum building material, comprising the following steps:

[0057] 1) Weigh 65 kg of phosphogypsum and 3.2 kg of nano-silica and put them into a mixer and stir evenly to obtain a phosphogypsum mixture;

[0058] 2) Add 0.8 kg of polycarboxylate superplasticizer and 20 kg of water to the phosphogypsum mixture obtained in step 1) and stir evenly to obtain a phosphogypsum slurry with a water-cement ratio of 0.6.

[0059] 3) Pour the phosphogypsum slurry obtained in step 2) into a triple mold with a size of 40mm×40mm×160mm, manually lift the mold 3-5cm and shake it up and down 10 times and scrape it flat. Then, after 24 hours, remove the mold to obtain the modified phosphogypsum building material.

[0060] 4) Measure 2 mL of 25 wt% ammonia water and 93 mL of anhydrous ethanol and mix them. Then add 5 mL of vinyltriethoxysilane and mix evenly to obtain a mixed solution. Then add 3 g of nano titanium dioxide and place it in a ventilated place with an open magnetic stirrer until the ammonia gas is removed to obtain a hydrophobic coating.

[0061] 5) Apply the hydrophobic coating obtained in step 4) to the surface of the bulk-modified phosphogypsum building material obtained in step 3) for waterproofing treatment. The waterproofing treatment method is spraying, and the spraying amount of the hydrophobic coating is 150cm. 2 / mL was then placed at room temperature for curing for more than 3 hours to obtain high-dosage water-resistant phosphogypsum building materials.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing phosphogypsum building materials that only undergo bulk modification, comprising the following steps:

[0064] 1) Weigh 95 kg of phosphogypsum and 5 kg of nano-silica and put them into a mixer and stir evenly to obtain a phosphogypsum mixture;

[0065] 2) Weigh 75 kg of the phosphogypsum mixture obtained in step 1), then add 1 kg of polycarboxylate superplasticizer and 24 kg of water and stir evenly to obtain a phosphogypsum slurry with a water-cement ratio of 0.6.

[0066] 3) Pour the phosphogypsum slurry obtained in step 2) into a triple mold with a size of 40mm×40mm×160mm, manually lift the mold 3-5cm and shake it up and down 10 times and scrape it flat. Then, after 24 hours, remove the mold to obtain the modified phosphogypsum building material.

[0067] Comparative Example 2

[0068] This comparative example provides a method for preparing phosphogypsum building materials using only hydrophobic coatings for surface modification, comprising the following steps:

[0069] 1) Weigh 100 kg of phosphogypsum, then add 1 kg of polycarboxylate superplasticizer and 24 kg of water and stir evenly to obtain a phosphogypsum slurry with a water-cement ratio of 0.6.

[0070] 2) Pour the phosphogypsum slurry obtained in step 1) into a triple mold with dimensions of 40mm×40mm×160mm. Manually lift the mold 3-5cm and vibrate it up and down 10 times, then smooth it. Let it sit for 24 hours to cure and shape. Then remove the mold to obtain unmodified phosphogypsum building material. The unmodified phosphogypsum building material during the curing process is as follows: Figure 3 As shown, unmodified phosphogypsum building materials exhibit severe water bleeding during the curing and molding process, leading to a decrease in the strength of the phosphogypsum building materials; the resulting unmodified phosphogypsum building materials, as shown... Figure 4 As shown.

[0071] 3) Measure 2 mL of 25 wt% ammonia water and 97 mL of anhydrous ethanol and mix them. Then add 1 mL of isobutyltriethoxysilane and mix evenly to obtain a mixed solution. Then add 3 g of nano titanium dioxide and place it in a ventilated place with an open magnetic stirrer until the ammonia gas is removed to obtain a hydrophobic coating.

[0072] 4) Apply the hydrophobic coating obtained in step 3) to the surface of the unmodified phosphogypsum building material obtained in step 2) for waterproofing treatment. The waterproofing treatment method is spraying, and the spraying amount of the hydrophobic coating is 150cm. 2 / mL, and then placed at room temperature for curing for more than 3 hours to obtain surface-modified phosphogypsum building materials.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 1 is that a commercially available hydrophobic agent (sodium methylsilicate) was used instead of the hydrophobic coating prepared from silane coupling agent, solvent, ammonia and nano titanium dioxide. Other conditions were the same as in Example 1.

[0075] Test Example 1

[0076] The compressive strength, flexural strength, and softening coefficient of the phosphogypsum building materials in Examples 1-3 and Comparative Examples 1-3 were tested. The flexural strength and compressive strength of gypsum were tested in accordance with the "Determination of Mechanical Properties of Building Gypsum". In the gypsum preparation process, the mass of powder and liquid was weighed first, then the powder was poured into the mixing pot, and then the liquid was poured in. The mixture was stirred at 125 rpm for 30 seconds to ensure that the slurry was fully mixed. The mixed gypsum slurry was poured into a 40mm×40mm×160mm triple mold and cured under natural indoor conditions. The experimental data were tested for 3 days and 28 days respectively. The test results are shown in Table 1.

[0077] Table 1 Mechanical properties of phosphogypsum building materials in Examples 1-3 and Comparative Examples 1-3

[0078]

[0079] According to Table 1 and Figure 1-4 It is known that unmodified phosphogypsum building materials, phosphogypsum building materials that have only undergone bulk or surface modification, and phosphogypsum building materials that have undergone bulk modification but surface modification using conventional hydrophobic agents all have poor mechanical properties. However, the phosphogypsum building materials obtained through the dual modification of this invention have superior mechanical properties. The high-dosage water-resistant phosphogypsum building materials obtained by this invention significantly improve their mechanical properties while enhancing their hydrophobicity, corrosion resistance, self-cleaning properties, and antibacterial properties through bulk and surface modification.

[0080] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-content water-resistant phosphogypsum building material, characterized in that, include: Phosphogypsum is mixed with nano-silica, water and water-reducing agent to form phosphogypsum slurry, which is then molded and cured to obtain bulk modified phosphogypsum building material. The hydrophobic coating is obtained by waterproofing the surface of the bulk-modified phosphogypsum building material; The raw materials for the hydrophobic coating include silane coupling agent, solvent, ammonia and nano titanium dioxide; The mass ratio of the phosphogypsum, nano-silica, water, and water-reducing agent is (65-75):(3.2-4.2):(20-30):(0.5-1.5). The preparation process of the hydrophobic coating is as follows: first, ammonia water is mixed with a solvent, then a silane coupling agent is added and mixed evenly to prepare a mixed solution, then nano titanium dioxide is added and mixed evenly, and then ammonia is removed by ventilation to obtain the hydrophobic coating.

2. The preparation method according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

3. The preparation method according to claim 1 or 2, characterized in that, The concentration of the ammonia solution is 25 wt%.

4. The preparation method according to claim 1, characterized in that, The solvent is anhydrous ethanol.

5. The preparation method according to claim 1, characterized in that, Based on a hydrophobic coating volume of 100 mL, the amount of the silane coupling agent is 1-5 mL, the amount of the ammonia water is 2 mL, the amount of the nano titanium dioxide is 3 g, and the remainder is solvent.

6. The preparation method according to claim 1, characterized in that, Includes the following steps: 1) Add phosphogypsum and nano-silica into a mixer and mix well to obtain a phosphogypsum mixture; 2) Add water-reducing agent and water to the phosphogypsum mixture obtained in step 1) and stir evenly to obtain phosphogypsum slurry; 3) Pour the phosphogypsum slurry obtained in step 2) into a mold, vibrate and smooth it, cure and shape it, and then demold to obtain the modified phosphogypsum building material. 4) Waterproofing treatment is applied to the surface of the bulk modified phosphogypsum building material obtained in step 3), and then it is placed at room temperature for curing treatment to obtain a high-dosage water-resistant phosphogypsum building material.

7. The preparation method according to claim 6, characterized in that, The curing and shaping time is ≥24 hours; And / or, the curing process lasts for ≥3 h.

8. A high-content water-resistant phosphogypsum building material, characterized in that, It is prepared by the method for preparing high-dosage water-resistant phosphogypsum building materials according to any one of claims 1-7.

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