Phosphogypsum rapid-hardening curing agent composition with adjustable setting time and application of phosphogypsum rapid-hardening curing agent composition

Abstract

The invention relates to the technical field of ardealite solid waste recycling, in particular to an ardealite quick-hardening curing agent composition with adjustable setting time and application of the ardealite quick-hardening curing agent composition. The composition comprises an active filler, a whisker material, a polymer retarder, a water reducer and an alkaline activator. The ardealite rapid hardening composition can adjust the setting time of an ardealite curing material in a certain range, and can better improve the mechanical properties and durability of the ardealite curing material.

Description

Technical Field

[0001] This invention relates to the field of phosphogypsum solid waste recycling technology, specifically to a phosphogypsum fast-hardening curing agent composition with adjustable setting time and its application. Background Technology

[0002] Phosphogypsum is a major industrial solid waste generated during the wet-process phosphoric acid production process, producing approximately 4.5-5.5 tons of phosphogypsum for every ton of phosphoric acid produced. The large-scale stockpiling of phosphogypsum not only occupies land, but also, due to its content of soluble phosphorus and heavy metal pollutants, leads to eutrophication of water bodies and soil acidification through rainwater leaching, posing a serious threat to the ecological environment. How to achieve large-scale resource utilization of phosphogypsum has become a key point in my country's ecological civilization construction.

[0003] Traditional methods use cement as a curing agent for curing. However, when using cement for curing, phosphogypsum is calcined. During the calcination process, phosphorus and fluorine volatilize, causing air pollution. At the same time, retarders such as citric acid are added, but the retardation effect is uncontrollable and causes a loss of strength in the cured material. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing phosphogypsum curing components, such as uncontrollable retarding effects and severe strength loss in cured materials, and to provide a phosphogypsum fast-curing agent composition with adjustable setting time and its application. This phosphogypsum fast-curing composition can adjust the setting time of phosphogypsum cured materials within a certain range, and can also better increase the mechanical properties and durability of phosphogypsum cured materials.

[0005] To achieve the above objectives, the first aspect of the present invention provides a phosphogypsum fast-setting agent composition with adjustable setting time, the composition comprising an active filler, whisker material, a polymeric retarder, a water-reducing agent, and an alkaline activator.

[0006] As a preferred technical solution of the present invention, the mass ratio of the active filler, whisker material, polymeric retarder, water-reducing agent and alkaline activator is 100:(25-30):(5-20):(2-3):(5-8).

[0007] As a preferred embodiment of the present invention, the active filler includes at least one of silicate cement, fly ash, slag and phosphorus slag powder.

[0008] As a more preferred technical solution of the present invention, the active filler includes silicate cement and fly ash, preferably the mass ratio of silicate cement to fly ash is (3-10):1, for example it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, preferably (5-8):1.

[0009] The silicate cement in this invention is commercially available and can be commercially available 42.5R ordinary silicate cement.

[0010] The fly ash in this invention can be obtained commercially, such as commercially available Grade I low-calcium fly ash.

[0011] As a preferred embodiment of the present invention, the whisker material includes calcium sulfate whiskers and / or silicon carbide whiskers.

[0012] As a preferred embodiment of the present invention, the whisker material is a combination of calcium sulfate whiskers and silicon carbide whiskers.

[0013] In this invention, calcium sulfate whiskers and silicon carbide whiskers are used together as whisker materials, which enables the composition of this invention to better increase the mechanical properties of the cured material when used.

[0014] As a preferred embodiment of the present invention, the mass ratio of calcium sulfate whiskers to silicon carbide whiskers is (1-5):1, for example, 1:1, 2:1, 3:1, 4:1 or 5:1, preferably (2-3):1.

[0015] As a preferred embodiment of the present invention, the average particle size of the calcium sulfate whiskers is 5-20 μm.

[0016] The calcium sulfate whiskers in this invention can be obtained commercially, for example, purchased from Taizhen Mineral Products Processing Plant in Lingshou County, with an average particle size of 10 μm.

[0017] As a preferred embodiment of the present invention, the average particle size of the silicon carbide crystals is 1-10 μm.

[0018] The silicon carbide whiskers in this invention can be obtained commercially, for example, purchased from Hubei Xinyuhong Biomedical Technology Co., Ltd., with an average particle size of 8μm.

[0019] As a preferred embodiment of the present invention, the polymeric retarder contains acrylamide structural units, acrylic acid structural units, dithiodiacrylic acid structural units, and 2-acrylamide-2-methylpropanesulfonic acid structural units.

[0020] The polymeric retarder containing acrylamide, acrylic acid, dithiodiacrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid structural units in this invention not only enables controllable setting time, but also, when used in phosphogypsum curing materials, better increases the strength and wet-dry cycle durability of the cured material. This is presumably because the 2-acrylamide-2-methylpropanesulfonic acid structural unit has a strong hydration effect that delays hydration and improves the polymer's water retention. Simultaneously, the acrylamide and acrylic acid structural units further regulate hydration kinetics, balancing retarding and strength development. Furthermore, the dithiodiacrylic acid structural unit enables self-healing of microcracks and increases the cross-linking network, allowing the composition to effectively increase the mechanical properties and durability of the cured phosphogypsum material.

[0021] As a preferred embodiment of the present invention, the molar amount of the acrylic structural unit is 50%-60% of the molar amount of the acrylamide structural unit, for example, 50%, 52%, 55%, 58% or 60%.

[0022] As a preferred embodiment of the present invention, the molar amount of the 2-acrylamide-2-methylpropanesulfonic acid structural unit is 20%-100% of the molar amount of the acrylamide structural unit, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%.

[0023] In this invention, it was found that controlling the content of 2-acrylamide-2-methylpropanesulfonic acid structural units can selectively adjust the setting time to a certain extent.

[0024] As a preferred embodiment of the present invention, the molar amount of the dithiodiacrylate structural unit is 10%-20% of the molar amount of the acrylamide structural unit, for example, 10%, 12%, 15%, 18% or 20%.

[0025] In this invention, it was found that controlling the content of dithiodiacrylate structural units within the above-mentioned range can better increase the mechanical properties of the product when the composition is used as a phosphogypsum curing material. When the content is too high or too low, it will affect the overall performance of the final product. It is speculated that when the content of dithiodiacrylate structural units is too low, the cross-linking network is insufficient and cannot play a good self-healing role. However, when the content is too high, the polymer retarder is over-cross-linked, which hinders the interpenetrating growth of gypsum crystals and thus affects its strength.

[0026] In this invention, the molar amounts of the acrylamide structural unit, acrylic acid structural unit, dithiodiacrylic acid structural unit, and 2-acrylamide-2-methylpropanesulfonic acid structural unit are respectively expressed as the molar amounts of their respective corresponding monomers.

[0027] In this invention, the polymeric retarder can be prepared by copolymerizing monomers corresponding to structural units. As a preferred embodiment of this invention, the preparation method of the polymeric retarder includes:

[0028] Acrylamide, acrylic acid, dithiodiacrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, water, and sodium dodecyl sulfate are added to a reactor and mixed. Then, the pH of the solution is adjusted to 8-9 using a 30-40 wt% NaOH aqueous solution. Potassium persulfate is then added and the mixture is reacted at 80-85°C for 1-1.5 hours. After cooling to room temperature, the mixture is washed with anhydrous ethanol, pulverized, and dried to constant weight to obtain the polymeric retarder.

[0029] In a preferred embodiment of the present invention, the molar amount of acrylic acid is 50%-60% of the molar amount of acrylamide.

[0030] As a preferred embodiment of the present invention, the molar amount of 2-acrylamide-2-methylpropanesulfonic acid is 20%-100% of the molar amount of acrylamide.

[0031] As a preferred embodiment of the present invention, the molar amount of the dithiodiacrylic acid is 10%-20% of the molar amount of the acrylamide.

[0032] As a preferred embodiment of the present invention, the mass of the water is 10-20 times the total mass of the acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamide-2-methylpropanesulfonic acid.

[0033] As a preferred embodiment of the present invention, the mass of sodium dodecyl sulfate is 3%-5% of the mass of the water.

[0034] As a preferred embodiment of the present invention, the mass of the potassium persulfate is 0.05%-1% of the total mass of the acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid.

[0035] As a preferred embodiment of the present invention, the water-reducing agent includes a polycarboxylate water-reducing agent.

[0036] The polycarboxylate superplasticizer in this invention is commercially available, for example, from Jiangsu Subote New Material Co., Ltd. -9 series polycarboxylate superplasticizer.

[0037] As a preferred embodiment of the present invention, the alkaline activator comprises water glass and sodium hydroxide.

[0038] As a preferred embodiment of the present invention, the mass ratio of the water glass to the sodium hydroxide is (5-10):1, for example, 5:1, 6:1, 7:1, 8:1, 9:1 or 1:1.

[0039] The water glass in this invention can be obtained commercially, such as commercially available 40 Baume water glass.

[0040] The second aspect of the present invention provides the application of the adjustable setting time phosphogypsum fast-setting agent composition described in the first aspect of the present invention in phosphogypsum curing materials.

[0041] As a preferred technical solution, the raw materials of the phosphogypsum curing material include phosphogypsum, water, and the phosphogypsum fast-setting agent composition with adjustable setting time as described in the first aspect of the present invention. Preferably, the mass of the phosphogypsum is 4.5-6 times the mass of the reactive filler in the phosphogypsum fast-setting agent composition with adjustable setting time, and preferably, the mass of the phosphogypsum is 10%-30% of the mass of the water.

[0042] As a preferred technical solution of the present invention, the preparation method of the phosphogypsum curing material includes: dispersing phosphogypsum in water to obtain a mixture, then adding active filler, whisker material, polymer retarder and water-reducing agent to the mixture and mixing evenly, finally adding alkaline activator and mixing evenly, pouring into a mold, molding and curing, to obtain the phosphogypsum curing material.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] In existing processes, small-molecule retarders, such as citric acid, are often used to control the setting time of cured materials. However, small-molecule retarders only delay hydration through chelation, resulting in a short-lived retardation effect and failing to significantly enhance the strength of the system. In this invention, a polymeric retarder containing acrylamide, acrylic acid, dithiodiacrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid structural units is used. This not only enables controllable setting time but also, when used in phosphogypsum cured materials, further enhances the strength and wet-dry cycle durability of the cured material.

[0045] The compositions and embodiments of the present invention will be described in more detail below, but the present invention is not limited thereto.

[0046] Preparation Example

[0047] The following preparation examples provide information on the preparation of polymeric retarder.

[0048] Preparation Example 1

[0049] Preparation of polymeric retarder A:

[0050] Acrylamide, acrylic acid, dithiodiacrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, water, and sodium dodecyl sulfate were added to a reactor and mixed. The pH of the solution was then adjusted to 8.7 using a 32wt% NaOH aqueous solution. Potassium persulfate was then added and the mixture was reacted at 85°C for 1.5 hours. After cooling to room temperature, the mixture was washed with anhydrous ethanol, pulverized, and dried to constant weight to obtain polymeric retarder A.

[0051] The molar ratio of acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamide-2-methylpropanesulfonic acid is 100:55:15:30.

[0052] The mass of water is 18 times the total mass of the acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamide-2-methylpropanesulfonic acid;

[0053] The mass of sodium dodecyl sulfate is 4% of the mass of water;

[0054] The mass of potassium persulfate is 0.5% of the total mass of the acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamide-2-methylpropanesulfonic acid.

[0055] Preparation Example 2

[0056] Preparation of polymeric retarder B:

[0057] The method of preparation example 1 is the same, except that the molar ratio of acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is 100:55:15:50.

[0058] The rest is the same as in Example 1, and the polymeric retarder B is finally prepared.

[0059] Preparation Example 3

[0060] Preparation of polymeric retarder C:

[0061] The method of preparation example 1 is the same, except that the molar ratio of acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is 100:55:15:80.

[0062] The rest is the same as in Example 1, and the polymeric retarder C is finally prepared.

[0063] Preparation Example 4

[0064] Preparation of polymeric retarder D:

[0065] The method of preparation example 1 is the same, except that the molar ratio of acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is 100:55:30:50.

[0066] The rest is the same as in Example 1, and the polymeric retarder D is finally prepared.

[0067] Preparation Example 5

[0068] Preparation of polymeric retarder E:

[0069] The method of preparation example 1 is the same, except that the molar ratio of acrylamide, acrylic acid, dithiodiacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is 100:55:5:50.

[0070] The rest is the same as in Example 1, and the polymeric retarder B is finally prepared. Example

[0071] The following examples illustrate a method for preparing phosphogypsum cured materials using the phosphogypsum rapid-hardening agent composition of the present invention.

[0072] In the following examples, the silicate cement is commercially available 42.5R ordinary silicate cement;

[0073] The fly ash is commercially available Grade I low-calcium fly ash;

[0074] Calcium sulfate whiskers were purchased from Taizhen Mineral Products Processing Plant in Lingshou County, with an average particle size of 10 μm.

[0075] Silicon carbide whiskers were purchased from Hubei Xinyuhong Biomedical Technology Co., Ltd., with an average particle size of 8 μm.

[0076] The polycarboxylate superplasticizer is from Jiangsu Subote New Material Co., Ltd. -9 series polycarboxylate superplasticizer;

[0077] The water glass is 40 Baume water glass.

[0078] 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.

[0079] Example 1

[0080] Preparation of the phosphogypsum rapid-hardening agent composition: Prepare an active filler, whisker material, polymeric retarder, water-reducing agent, and alkaline activator in a mass ratio of 100:26:5:2.4:6.2; wherein, the active filler is silicate cement and fly ash in a mass ratio of 6:1; the whisker material is calcium sulfate whiskers and silicon carbide whiskers in a mass ratio of 2.5:1; the polymeric retarder is polymeric retarder B; the water-reducing agent is polycarboxylate water-reducing agent; and the alkaline activator is water glass and sodium hydroxide in a mass ratio of 6.2:1.

[0081] Preparation of raw materials for phosphogypsum curing material: Prepare the above-mentioned phosphogypsum rapid curing agent composition and phosphogypsum, wherein the mass of phosphogypsum is 5 times the mass of the active filler;

[0082] Preparation of phosphogypsum curing material: Disperse phosphogypsum in water to obtain a mixture with a water content of 20wt%. Then add active filler, whisker material, polymer retarder and water-reducing agent to the mixture and mix evenly. Finally, add alkaline activator and mix evenly. Pour into a mold, shape and cure to obtain phosphogypsum curing material.

[0083] Example 2

[0084] The method according to Example 1 differs in that:

[0085] The mass ratio of active filler, whisker material, polymeric retarder, water-reducing agent and alkaline activator is 100:25:10:2.5:6.5;

[0086] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0087] Example 3

[0088] The method according to Example 1 differs in that:

[0089] The mass ratio of active filler, whisker material, polymeric retarder, water-reducing agent and alkaline activator is 100:25:15:2.5:6.5;

[0090] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0091] Example 4

[0092] The method according to Example 1 differs in that:

[0093] The mass ratio of active filler, whisker material, polymeric retarder, water-reducing agent and alkaline activator is 100:25:20:2.5:6.5;

[0094] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0095] Example 5

[0096] The method according to Example 1 differs in that:

[0097] Replace polymeric retarder B with polymeric retarder A;

[0098] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0099] Example 6

[0100] The method according to Example 1 differs in that:

[0101] Replace polymeric retarder B with polymeric retarder C;

[0102] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0103] Example 7

[0104] The method according to Example 1 differs in that:

[0105] Replace polymeric retarder B with polymeric retarder D;

[0106] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0107] Example 8

[0108] The method according to Example 1 differs in that:

[0109] Replace polymeric retarder B with polymeric retarder E;

[0110] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0111] Comparative Example 1

[0112] The method according to Example 1 differs in that:

[0113] Replace polymeric retarder B with citric acid;

[0114] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0115] Comparative Example 2

[0116] The method according to Example 1 differs in that:

[0117] Whiskers-free materials;

[0118] The rest is the same as in Example 1, and the final phosphogypsum cured material is obtained.

[0119] Performance testing

[0120] 1. Setting time test: The initial setting time and final setting time of the phosphogypsum curing material raw material are tested in accordance with GB / T1346-2011 "Standard Consistency Water Requirement, Setting Time and Soundness Test Methods for Cement".

[0121] 2. Unconfined compressive strength: Tested according to T 0805-1994 "Test method for unconfined compressive strength of inorganic binder stabilized materials".

[0122] 3. Wet-dry cycling test: The sample size, preparation method, and curing conditions for the wet-dry cycling test are the same as those for the unconfined compressive strength test. After curing the specimens under standard conditions for 28 days, the wet-dry cycling test is performed. Each specimen undergoes 12 wet-dry cycles, with 3 parallel samples used each time. One wet-dry cycle includes placing the specimen in a 55℃ oven for 12 hours, weighing the specimen after removal, cooling it, placing it in a 20℃ water bath for 1 day, removing the specimen, drying it, and weighing it again. Calculate the mass loss rate of the sample after the wet-dry cycling test; where, mass loss rate = (mass of the sample before the wet-dry cycling test - mass of the sample after 12 wet cycles) / mass of the sample before the wet-dry cycling test * 100%.

[0123] The performance test results of the examples and comparative examples are shown in Table 1.

[0124] Table 1. Performance test results of the examples and comparative examples.

[0125]

[0126]

[0127] As can be seen from the test results in Table 1, the phosphogypsum fast-curing composition of the present invention can adjust the setting time of phosphogypsum curing materials within a certain range, and can also better increase the mechanical properties and durability of phosphogypsum curing materials.

[0128] 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 phosphogypsum rapid-hardening agent composition with adjustable setting time, characterized in that, The composition includes active filler, whisker material, polymeric retarder, water-reducing agent and alkaline activator.

2. The phosphogypsum rapid-hardening agent composition with adjustable setting time according to claim 1, characterized in that, The mass ratio of the active filler, whisker material, polymeric retarder, water-reducing agent and alkaline activator is 100:(25-30):(5-20):(2-3):(5-8).

3. The phosphogypsum rapid-hardening agent composition with adjustable setting time according to claim 1, characterized in that, The active filler includes at least one of silicate cement, fly ash, slag, and phosphorus slag powder.

4. The phosphogypsum rapid-hardening agent composition with adjustable setting time according to claim 1, characterized in that, The whisker material includes calcium sulfate whiskers and / or silicon carbide whiskers.

5. The phosphogypsum rapid-hardening agent composition with adjustable setting time according to claim 4, characterized in that, The average particle size of the calcium sulfate whiskers is 5-20 μm.

6. The phosphogypsum rapid-hardening agent composition with adjustable setting time according to claim 4, characterized in that, The average particle size of the silicon carbide crystals is 1-10 μm.

7. The phosphogypsum rapid-hardening agent composition with adjustable setting time according to claim 1, characterized in that, The polymeric retarder contains acrylamide structural units, acrylic acid structural units, dithiodiacrylic acid structural units, and 2-acrylamide-2-methylpropanesulfonic acid structural units.

8. The phosphogypsum rapid-hardening agent composition with adjustable setting time according to claim 7, characterized in that, The molar amount of the acrylic acid structural unit is 50%-60% of the molar amount of the acrylamide structural unit; the molar amount of the 2-acrylamide-2-methylpropanesulfonic acid structural unit is 20%-100% of the molar amount of the acrylamide structural unit; and the molar amount of the dithiodiacrylic acid structural unit is 10%-20% of the molar amount of the acrylamide structural unit.

9. The phosphogypsum rapid-hardening agent composition with adjustable setting time according to claim 1, characterized in that, The water-reducing agent includes a polycarboxylate water-reducing agent; the alkali activator includes water glass and sodium hydroxide.

10. The application of a phosphogypsum fast-setting agent composition with adjustable setting time in phosphogypsum curing materials; wherein the phosphogypsum fast-setting agent composition with adjustable setting time is the phosphogypsum fast-setting agent composition with adjustable setting time according to any one of claims 1-10.

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