A composite solidified material containing active filler and organosilicon modified phosphogypsum and its use

Abstract

The present application relates to the technical field of phosphogypsum solid waste recycling, and particularly relates to a phosphogypsum composite solidified material containing active filler and organosilicon modified material and application thereof.The raw materials of the phosphogypsum composite solidified material include, by weight, 65-85 parts of phosphogypsum, 10-20 parts of active filler, 3-10 parts of organosilicon polymer, 1-8 parts of activator and 0.5-5 parts of polypropylene fiber.The phosphogypsum-based material in the present application simultaneously realizes the advantages of ultra-low scouring loss and high early strength, and can avoid the phenomenon of surface tackiness.

Description

Technical Field

[0001] This invention relates to the field of phosphogypsum solid waste recycling technology, specifically to a phosphogypsum composite curing material containing active fillers and organosilicon modification and its applications. Background Technology

[0002] Phosphogypsum is an industrial byproduct of wet-process phosphoric acid production, primarily composed of calcium sulfate dihydrate. Global annual emissions exceed 280 million tons, but its comprehensive utilization rate is less than 35%. Large-scale stockpiling not only occupies land but also contributes to eutrophication, soil acidification, and groundwater pollution due to its content of soluble phosphorus, fluorine, heavy metals, and acidic impurities. Converting phosphogypsum into high-value-added building materials (such as roadbed fillers and wall blocks) is a core direction for resource utilization; however, phosphogypsum itself suffers from poor durability and insufficient mechanical properties.

[0003] To enhance the durability and mechanical properties of phosphogypsum-cured materials, binders and specific curing agents are often added. CN116986880A describes a method for preparing a phosphogypsum-cured material with good properties and low scouring mass loss by mixing phosphogypsum lightweight aggregate and phosphogypsum powder in a specific ratio, and using binders and curing agents such as water-based epoxy resin and polyetheramine, combined with fibers, sawdust, and chitosan. However, the mechanical properties of this phosphogypsum-cured material are still not high enough, and due to the addition of binders such as water-based epoxy resin and polyetheramine, its migration can easily cause the phosphogypsum road base material to become sticky. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing phosphogypsum composite curing materials, such as insufficient strength and surface stickiness, and to provide a phosphogypsum composite curing material containing active fillers and modified with organosilicon, as well as its applications. This phosphogypsum composite curing material exhibits excellent strength and avoids surface stickiness.

[0005] To achieve the above objectives, the first aspect of the present invention provides a phosphogypsum composite curing material containing active filler and organosilicon modification. By weight, the raw materials of the phosphogypsum composite curing material include: 65-85 parts of phosphogypsum, 10-20 parts of active filler, 3-10 parts of organosilicon polymer, 1-8 parts of activator, and 0.5-5 parts of polypropylene fiber.

[0006] In this invention, in order to enable the raw materials to work together better and increase the overall performance of the prepared phosphogypsum composite curing material, preferably, by weight, the raw materials of the phosphogypsum composite curing material include: 72-78 parts of phosphogypsum, 12-18 parts of active filler, 3-5 parts of organosilicon polymer, 2-4 parts of activator, and 1-1.5 parts of polypropylene fiber.

[0007] Phosphogypsum is a solid waste generated during the wet process of phosphoric acid production. Its main component is calcium sulfate dihydrate. The phosphogypsum in this invention can be obtained commercially. Preferably, the phosphogypsum is Grade I phosphogypsum that meets the requirements of GB / T 23456-2018 and is purchased from Hubei Xinyangfeng Modern Agricultural Development Co., Ltd.

[0008] Preferably, the active filler comprises a combination of silicate cement, metakaolin, and fly ash.

[0009] More preferably, the weight ratio of the silicate cement, metakaolin and fly ash is 1:(0.3-1):(0.1-0.5), and more preferably 1:(0.4-0.5):(0.2-0.25).

[0010] Silicate cement refers to cement clinker with calcium silicate as the main component. The silicate cement in this invention can be obtained commercially, such as commercially available 42.5R ordinary silicate cement.

[0011] Metakaolin is a volcanic ash material formed by calcining and activating kaolin at a specific temperature. The metakaolin in this invention can be obtained commercially, for example, purchased from Yongchang Mineral Products Processing Plant in Lingshou County, with an average particle size of 1250 mesh.

[0012] Coal ash is a fine particulate solid waste collected from the flue gas after coal combustion in coal-fired power plants. It belongs to pozzolanic materials. The fly ash in this invention can be obtained commercially, for example, the fly ash is Grade I low-calcium fly ash.

[0013] Preferably, the organosilicon polymer contains acrylamide structural units, vinylphosphonic acid structural units, and vinyltriethoxysilane structural units.

[0014] The organosilicon polymers in this invention contain silyl ether groups, which are easily hydrolyzed into silanol groups in water. These groups can condense with the hydroxyl groups on the surface of phosphogypsum / active filler, forming a hydrophobic siloxane network in the system through chemical bonding. This significantly reduces the hydrophilicity of the material. Furthermore, the silanes are enriched and cross-linked in the system to form a dense hydrophobic layer, which can suppress surface stickiness.

[0015] In this invention, each structural unit in the organosilicon polymer is provided by its corresponding monomer. Specifically, the acrylamide structural unit is provided by acrylamide, the vinylphosphonic acid structural unit is provided by vinylphosphonic acid, and the vinyltriethoxysilane structural unit is provided by vinyltriethoxysilane. Preferably, the mass ratio of the acrylamide structural unit, the vinylphosphonic acid structural unit, and the vinyltriethoxysilane structural unit is 1:(0.2-0.6):(0.5-1), more preferably 1:(0.3-0.35):(0.6-0.65). The mass of each structural unit in this invention is based on the mass of its corresponding monomer.

[0016] In this invention, it was found that controlling the mass ratio of acrylamide structural units, vinylphosphonic acid structural units, and vinyltriethoxysilane structural units within the aforementioned range can better achieve a balance between strength and erosion resistance. This is presumably because the lack of vinylphosphonic acid structural units may reduce the interaction between the organosilicon polymer and components such as active fillers, affecting the overall performance. In addition, an excessive content of vinyltriethoxysilane structural units can lead to excessive cross-linking of the organosilicon polymer. Although this can slightly increase the erosion resistance of the phosphogypsum composite cured material, it may affect the toughness and adhesion of the phosphogypsum composite cured material, thus reducing its erosion resistance.

[0017] In this invention, the organosilicon polymer can be prepared by copolymerization of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane. Preferably, the preparation method of the organosilicon polymer includes: adding acrylamide, vinylphosphonic acid, vinyltriethoxysilane, and water to a reactor to obtain a mixed solution; adjusting the pH of the mixed solution to 8-9 with an aqueous sodium hydroxide solution; adding an emulsifier and mixing to obtain a reaction raw material solution; adding an initiator to carry out a copolymerization reaction; and finally precipitating, filtering, washing, and drying to obtain the organosilicon polymer.

[0018] Preferably, in the preparation of organosilicon polymers, the mass ratio of acrylamide, vinylphosphonic acid and vinyltriethoxysilane is 1:(0.2-0.6):(0.5-1), more preferably 1:(0.3-0.35):(0.6-0.65).

[0019] Preferably, when preparing organosilicon polymers, the total mass of acrylamide, vinylphosphonic acid and vinyltriethoxysilane is denoted as m, and the mass of water is denoted as m1, where m1 is 8-15 times m.

[0020] Preferably, when preparing organosilicon polymers, the concentration of the sodium hydroxide aqueous solution is 3-8 wt%.

[0021] Preferably, when preparing organosilicon polymers, the emulsifier is selected from at least one of OP-10, NP-10 and sodium dodecylbenzenesulfonate, and preferably NP-10.

[0022] Preferably, when preparing organosilicon polymers, the mass of the emulsifier is 6-8% of the mass of water.

[0023] Preferably, when preparing organosilicon polymers, the initiator is selected from azo initiators.

[0024] Preferably, in preparing organosilicon polymers, the azo initiator is selected from at least one of azobisisobutyronitrile, azobisisovalerate, azobisisoheptanenitrile, azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, and azobiscyclohexylformonitrile and azobisisopropylimidazoline. Azobisisobutyramidine hydrochloride is used as an example in this invention.

[0025] Preferably, in the preparation of organosilicon polymers, the mass of the initiator is 0.2-0.3% of the total mass of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane.

[0026] Preferably, when preparing organosilicon polymers, the copolymerization reaction conditions include: being carried out under a nitrogen atmosphere, a copolymerization temperature of 50-70°C, and a time of 8-15 hours.

[0027] In the preparation of organosilicon polymers in this invention, the purpose of precipitation is to precipitate the organosilicon polymers from the copolymerization reaction. The specific precipitation method can be a conventional method in the art, such as precipitation in anhydrous ethanol. Preferably, the volume ratio of anhydrous ethanol to water is 1:(1-2).

[0028] In this invention, there are no special limitations on the washing method when preparing organosilicon polymers; for example, acetone can be used for washing 3-5 times.

[0029] In the preparation of organosilicon polymers in this invention, the drying method can be a conventional method obtained in the art, such as vacuum drying at 40-50°C to constant weight.

[0030] Preferably, the preparation method of the organosilicon polymer includes: adding acrylamide, vinylphosphonic acid, vinyltriethoxysilane, and water (in an amount 8-15 times the total mass of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane) in a mass ratio of 1:(0.3-0.35):(0.6-0.65) to a reactor and mixing them thoroughly to obtain a mixed solution; then adjusting the pH of the mixed solution to 9 with a 5wt% sodium hydroxide aqueous solution; and adding emulsifier NP-10 (in an amount equal to the water mass). Mix 6-8% of the raw materials to obtain a reaction solution. Then, purge the system with nitrogen to create a nitrogen atmosphere. Add azobisisobutyramidine hydrochloride (0.2-0.3% of the total mass of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane) and copolymerize at 50-70°C for 8-15 hours. After copolymerization, add anhydrous ethanol (1:1 volume ratio with water) for precipitation. Finally, filter, wash 5 times with acetone, and vacuum dry at 40°C to constant weight to obtain an organosilicon polymer.

[0031] Preferably, the activator is selected from water glass and sodium hydroxide.

[0032] Preferably, the weight ratio of water glass to sodium hydroxide is (3-10):1, more preferably (3.5-4):1.

[0033] The water glass in this invention can be obtained commercially, preferably commercially available 40 Baume water glass.

[0034] Preferably, the polypropylene fiber has an average diameter of 1-5 mm and an average length of 100-400 mm.

[0035] The polypropylene fiber in this invention can be obtained commercially, for example, the polypropylene fiber is purchased from Shandong Jinyi Building Materials Co., Ltd., with an average diameter of 2mm and an average length of 300mm.

[0036] Preferably, the preparation method of the phosphogypsum composite curing material includes: dispersing phosphogypsum in water to obtain a mixture, then adding active filler, organosilicon polymer and polypropylene fiber to the mixture for a first mixing, and finally adding an activator for a second mixing, pouring it into a mold, molding and curing, to obtain the phosphogypsum composite curing material containing active filler and organosilicon modification.

[0037] In this invention, when preparing the phosphogypsum composite curing material, the amount of water used is such that the water content of the mixture is 15-20 wt%.

[0038] In the preparation of phosphogypsum composite curing material in this invention, there are no special limitations on the conditions of the first mixing and the second mixing, as long as they are mixed evenly. This invention does not impose any special restrictions on this.

[0039] The second aspect of the present invention provides the application of the phosphogypsum composite curing material containing active filler and organosilicon modified according to the first aspect of the present invention in road base materials.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects: In this invention, by combining specific organosilicon polymers with active fillers and corresponding activators, the advantages of ultra-low erosion loss and high early strength can be simultaneously achieved in phosphogypsum-based materials, while avoiding surface stickiness. Example

[0041] The following describes in more detail the synthesis examples and embodiments of the present invention, but the present invention is not limited thereto.

[0042] In the following examples and comparative examples: The phosphogypsum was Grade 1 phosphogypsum that met the requirements of GB / T 23456-2018 and was purchased from Hubei Xinyangfeng Modern Agricultural Development Co., Ltd. The silicate cement used is commercially available 42.5R ordinary silicate cement; The metakaolin was purchased from Yongchang Mineral Products Processing Plant in Lingshou County, with an average particle size of 1250 mesh. The fly ash is Grade I low-calcium fly ash; The water glass is commercially available 40 Baume water glass; The polypropylene fibers were purchased from Shandong Jinyi Building Materials Co., Ltd., with an average diameter of 2mm and an average length of 300mm. Example 1

[0043] Preparation of organosilicon polymers: Acrylamide, vinylphosphonic acid, vinyltriethoxysilane, and water (12 times the total mass of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane) in a mass ratio of 1:0.32:0.6 were added to a reactor and mixed thoroughly to obtain a mixed solution. Then, the pH of the mixed solution was adjusted to 9 using a 5wt% sodium hydroxide aqueous solution. Emulsifier NP-10 (7% of the mass of water) was added and mixed thoroughly to obtain a reaction feed liquid. Nitrogen gas was then introduced to purge the system under a nitrogen atmosphere. Azobisisobutyramidine hydrochloride (0.25% of the total mass of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane) was then added and copolymerized at 56°C for 12 hours. After the copolymerization reaction was completed, anhydrous ethanol (1:1 volume ratio with water) was added for precipitation. Finally, the mixture was filtered, washed five times with acetone, and vacuum dried at 40°C to constant weight to obtain an organosilicon polymer.

[0044] Preparation of phosphogypsum composite curing material: Prepare 75 parts by weight of phosphogypsum, 15 parts of active filler, 4.8 parts of organosilicon polymer, 3.8 parts of activator, and 1.4 parts of polypropylene fiber; Phosphogypsum was dispersed in water to obtain a mixture with a water content of 18 wt%. Then, active filler, organosilicon polymer and polypropylene fiber were added to the mixture and mixed evenly. Finally, an activator was added and mixed evenly. The mixture was poured into a mold and cured to obtain a phosphogypsum composite curing material with active filler and organosilicon modification.

[0045] The active filler consists of silicate cement, metakaolin, and fly ash in a weight ratio of 1:0.44:0.22; the activator consists of water glass and sodium hydroxide in a weight ratio of 3.75:1. Example 2

[0046] Preparation of organosilicon polymers: Acrylamide, vinylphosphonic acid, vinyltriethoxysilane, and water (12 times the total mass of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane) in a mass ratio of 1:0.3:0.65 were added to a reactor and mixed thoroughly to obtain a mixed solution. Then, the pH of the mixed solution was adjusted to 9 using a 5wt% sodium hydroxide aqueous solution. Emulsifier NP-10 (7% of the mass of water) was added and mixed thoroughly to obtain a reaction feed liquid. Nitrogen gas was then introduced to purge the system under a nitrogen atmosphere. Azobisisobutyramidine hydrochloride (0.25% of the total mass of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane) was then added and copolymerized at 56°C for 12 hours. After the copolymerization reaction was completed, anhydrous ethanol (1:1 volume ratio with water) was added for precipitation. Finally, the mixture was filtered, washed five times with acetone, and vacuum dried at 40°C to constant weight to obtain an organosilicon polymer.

[0047] Preparation of phosphogypsum composite curing material: Prepare 72.5 parts by weight of phosphogypsum, 17 parts of active filler, 5 parts of organosilicon polymer, 4 parts of activator, and 1.5 parts of polypropylene fiber. Phosphogypsum was dispersed in water to obtain a mixture with a water content of 18 wt%. Then, active filler, organosilicon polymer and polypropylene fiber were added to the mixture and mixed evenly. Finally, an activator was added and mixed evenly. The mixture was poured into a mold and cured to obtain a phosphogypsum composite curing material with active filler and organosilicon modification.

[0048] The active filler consists of silicate cement, metakaolin, and fly ash in a weight ratio of 1:0.45:0.25; the activator consists of water glass and sodium hydroxide in a weight ratio of 4:1. Example 3

[0049] The method according to Example 1 differs in that: By replacing acrylamide, vinylphosphonic acid, and vinyltriethoxysilane in a mass ratio of 1:0.32:0.6 with acrylamide and vinyltriethoxysilane in a mass ratio of 1:0.78, organosilicon polymers and their corresponding phosphogypsum composite curing materials were finally prepared. Example 4

[0050] The method according to Example 1 differs in that: The method according to Example 1 differs in that: By replacing the mass ratio of acrylamide, vinylphosphonic acid, and vinyltriethoxysilane with a mass ratio of 1:0.73:1.47 (acrylamide, vinylphosphonic acid, and vinyltriethoxysilane) with a mass ratio of 1:0.32:0.6, organosilicon polymers and their corresponding phosphogypsum composite curing materials were finally prepared.

[0051] Comparative Example 1 Prepare 77 parts by weight of phosphogypsum, 16.55 parts by weight of active filler, 5 parts by weight of activator, and 1.45 parts by weight of polypropylene fiber. Phosphogypsum was dispersed in water to obtain a mixture with a water content of 18 wt%. Then, active filler and polypropylene fiber were added to the mixture and mixed evenly. Finally, an activator was added and mixed evenly. The mixture was poured into a mold and cured to obtain a phosphogypsum composite curing material with active filler and organosilicon modification.

[0052] The active filler consists of silicate cement, metakaolin, and fly ash in a weight ratio of 1:0.44:0.22; the activator consists of water glass and sodium hydroxide in a weight ratio of 3.75:1.

[0053] Comparative Example 2 The method according to Example 1 differs in that: The organosilicon polymer was replaced with an acrylamide polymer. The preparation method of the acrylamide polymer was similar to that in Example 1, except that acrylamide and vinylphosphonic acid in a mass ratio of 1:0.62 were used instead of acrylamide, vinylphosphonic acid and vinyltriethoxysilane in a mass ratio of 1:0.32:0.6. The organosilicon polymer and its corresponding phosphogypsum composite curing material were finally prepared.

[0054] Performance testing The properties of the phosphogypsum composite curing materials in Examples 1-4 and Comparative Examples 1-2 were tested as follows.

[0055] 1. Erosion mass loss: Tested according to T 0860-2009 "Test method for erosion resistance of inorganic binder stabilized materials".

[0056] 2. Unconfined compressive strength: According to T 0805-1994 "Test method for unconfined compressive strength of inorganic binder stabilized materials".

[0057] 3. Observe whether the surface of the prepared phosphogypsum composite curing material is sticky.

[0058] The performance test results are shown in Table 1.

[0059] Table 1 Performance test results of phosphogypsum composite curing materials in Examples 1-4 and Comparative Examples 1-2

[0060] As can be seen from the test results in Table 1, the phosphogypsum-based material of the present invention simultaneously achieves the advantages of ultra-low erosion loss and high early strength, and can avoid surface stickiness.

[0061] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite curing material containing active filler and organosilicon-modified phosphogypsum, characterized in that, By weight, the raw materials of the phosphogypsum composite curing material include: 65-85 parts phosphogypsum, 10-20 parts active filler, 3-10 parts organosilicon polymer, 1-8 parts activator, and 0.5-5 parts polypropylene fiber.

2. The phosphogypsum composite curing material containing active filler and organosilicon modification according to claim 1, characterized in that, The active filler comprises a combination of silicate cement, metakaolin, and fly ash.

3. The phosphogypsum composite curing material containing active filler and organosilicon modification according to claim 2, characterized in that, The weight ratio of silicate cement, metakaolin, and fly ash is 1:(0.3-1):(0.1-0.5).

4. The phosphogypsum composite curing material containing active filler and organosilicon modification according to claim 1, characterized in that, The organosilicon polymer contains acrylamide structural units, vinylphosphonic acid structural units, and vinyltriethoxysilane structural units.

5. The phosphogypsum composite curing material containing active filler and organosilicon modification according to claim 4, characterized in that, The mass ratio of the acrylamide structural unit, the vinylphosphonic acid structural unit and the vinyltriethoxysilane structural unit is 1:(0.2-0.6):(0.5-1).

6. The phosphogypsum composite curing material containing active filler and organosilicon modification according to claim 1, characterized in that, The activator is selected from water glass and sodium hydroxide.

7. The phosphogypsum composite curing material containing active filler and organosilicon modification according to claim 6, characterized in that, The weight ratio of water glass to sodium hydroxide is (3-10):

1.

8. The phosphogypsum composite curing material containing active filler and organosilicon modification according to claim 1, characterized in that, The polypropylene fibers have an average diameter of 1-5 mm and an average length of 100-400 mm.

9. The phosphogypsum composite curing material containing active filler and organosilicon modification according to any one of claims 1-8, characterized in that, The preparation method of the phosphogypsum composite curing material includes: dispersing phosphogypsum in water to obtain a mixture, then adding active filler, organosilicon polymer and polypropylene fiber to the mixture for a first mixing, and finally adding an activator for a second mixing, pouring it into a mold, molding and curing, to obtain the phosphogypsum composite curing material containing active filler and organosilicon modification.

10. The application of the phosphogypsum composite curing material containing active filler and organosilicon modification as described in any one of claims 1-9 in road base materials.

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