Curing agent for waste soil treatment and preparation method and application thereof

Abstract

The invention relates to the technical field of solid waste resource recycling, in particular to a curing agent for waste soil treatment and a preparation method and application thereof. The curing agent for waste soil treatment is prepared from the following raw materials in parts by weight: 30 to 40 parts of carboxyl-terminated hyperbranched polyester, 2 to 4 parts of calcium formate, 25 to 35 parts of polyacrylamide, 7 to 13 parts of hydroxypropyl methyl cellulose, 2 to 4 parts of calcium stearate, 8 to 12 parts of potassium carbonate, 2 to 6 parts of sodium hydroxide, 3 to 5 parts of organic silicon defoaming agent and 8 to 12 parts of organic bentonite. The method has the advantage that the solidification effect of the waste soil with high water content is improved.

Description

Technical Field

[0001] The present application relates to the technical field of solid waste resource recycling, and in particular to a solidifying agent for waste soil treatment, a preparation method thereof, and an application thereof. Background Art

[0002] Silt slurry generated by river dredging and construction waste slurry from engineering projects have high water content, exhibit fluid plasticity, and exhibit extremely poor engineering performance. Among practical treatment methods, chemical solidification is a common approach for reinforcing soft soils. Through physical and chemical reactions between the solidifying agent and the soft soil, a solidified soil with high strength, integrity, and good water stability is formed. Solidifying agents are a new type of energy-saving and environmentally friendly engineering material synthesized from a variety of inorganic and organic materials for solidifying various types of soil. In civil engineering, the most commonly used solidifying agents are cement and lime. Lime has the longest history of use in civil engineering, but its drawback is that it produces low strength and poor results. Therefore, cement is currently the most predominant solidifying agent in civil engineering. However, the cement production process consumes a lot of energy and emits a lot of carbon dioxide, which is not conducive to environmental protection.

[0003] Based on this, currently developed green curing agents use traditional solid waste materials, such as granulated blast furnace slag powder and carbide slag, which can improve curing effects. However, when used on waste soils with high water content, such as shield mud, river dredging sludge, and seabed silt, rapid curing during dehydration and drying is difficult. As a result, small amounts of water remain between soil particles, resulting in loose bonds and insufficient structural strength and water resistance, leading to poor curing results. Summary of the Invention

[0004] In order to improve the solidification effect of waste soil with a high water content, the present application provides a solidifying agent for waste soil treatment, a preparation method and an application thereof.

[0005] In the first aspect, the present application provides a solidifying agent for waste soil treatment, which adopts the following technical solution: A curing agent for waste soil treatment comprises the following raw materials in parts by weight: 30-40 parts of carboxyl-terminated hyperbranched polyester, 2-4 parts of calcium formate, 25-35 parts of polyacrylamide, 7-13 parts of hydroxypropyl methylcellulose, 2-4 parts of calcium stearate, 8-12 parts of potassium carbonate, 2-6 parts of sodium hydroxide, 3-5 parts of organosilicon defoaming agent, and 8-12 parts of organobentonite.

[0006] By adopting the above technical solution, the curing agent of the present application is in a solid powder state. On the one hand, it is more convenient than liquid curing agents in storage and actual application. On the other hand, when it is in a solid powder state and added to waste soil with a high moisture content, it can also consume part of the moisture by dissolving in it, thereby improving the curing effect. When some raw materials, such as sodium hydroxide, are dissolved in the waste soil, the paste releases heat, which can also accelerate the evaporation of water and increase the curing rate. On this basis, the present application also abandons the straight-chain polycarboxylic acid polymer cross-linking agent from the raw material and adopts a carboxyl-terminated hyperbranched polymer as a cross-linking agent. The hyperbranched polymer has better water solubility and a smaller molecular viscosity, making it easier to dissolve and evenly disperse in the waste soil system. The carboxyl groups contained are at the end, and the carboxyl groups contained can fully exert the cross-linking effect, increase the cross-linking density, and enhance the strength and durability of the waste soil after curing. Polyacrylamide is added as a flocculant to adsorb soil particles to form a flocculated structure, and cooperates with the silicone defoamer to greatly reduce the porosity in the waste soil and increase the density of the waste soil after curing. In addition, the silicone defoamer can increase the hydrophobicity of the waste soil. The organic bentonite is an inorganic mineral / organic ammonium compound, which uses bentonite as raw material and utilizes the lamellar structure of montmorillonite in bentonite and its ability to swell and disperse into colloidal clay particles in water or organic solvents to absorb water to form a gel, thereby enhancing the plasticity and deformation resistance of the solidified soil and making the solidifying agent more suitable for soils with high water content. In addition, it cooperates with other cross-linking agents to increase the cross-linking density of the solidified soil and improve the drying of the solidified soil. The shrinkage rate did not show a significant increase, and the organic bentonite can also delay the settlement of the waste soil, increase the cross-linking time, make the cross-linking more complete, and also increase the strength of the solidified soil; calcium formate, calcium stearate, potassium carbonate and sodium hydroxide can adjust the pH of the waste soil to alkaline, promote the cross-linking of polyacrylamide, accelerate the curing reaction, and calcium stearate as a lubricant can also improve the construction performance; therefore, the curing agent of the present application can greatly improve the curing effect of waste soil with a high water content and improve the comprehensive performance of the waste soil after curing.

[0007] Preferably, the organosilicon defoamer is a powdered organosilicon defoamer.

[0008] By adopting the above technical solution, powdered silicone defoamer can be more easily evenly dispersed in the waste soil system, avoiding stratification of liquid defoamer, and reducing the risk of moisture absorption and agglomeration during storage, thereby extending the shelf life of the product. In terms of environmental protection, it can also achieve no solvent residue and reduce volatile pollution.

[0009] Preferably, the average molecular weight of the carboxyl-terminated hyperbranched polyester is 2600-12000.

[0010] By adopting the above technical solution, the low molecular weight carboxyl-terminated hyperbranched polyester has good fluidity, is easy to contact with soil particles, and has a fast reaction speed, but its molecular weight is too low and it contains fewer carboxyl groups, which affects its cross-linking density; the high molecular weight carboxyl-terminated hyperbranched polyester can provide a higher cross-linking density and enhance the structural strength of the solidified soil, but its molecular weight is too high and it is difficult to disperse, which may also lead to limited strength of the solidified soil; therefore, when its molecular weight is within this range, it is more suitable for the curing effect of this curing agent.

[0011] Preferably, the waste soil treatment curing agent further comprises 1-5 parts by weight of sepiolite.

[0012] By adopting the above technical solution, sepiolite is a fibrous hydrated magnesium silicate that absorbs water and becomes soft when it comes into contact with it. It can deform when the waste soil solidifies and loses water, thereby better filling the pores, improving the strength of the solidified soil, and buffering the expansion and water loss shrinkage defects of bentonite. In addition, sepiolite also has the advantages of high temperature resistance and strong salt resistance, which can improve the application of solidified soil in high temperature environments.

[0013] Preferably, the average particle size of the sepiolite is 10-100 μm.

[0014] By adopting the above technical solution, smaller-sized sepiolite can fill tiny pores and promote uniform distribution to avoid local uneven strength.

[0015] Preferably, the waste soil treatment curing agent further comprises 3-7 parts by weight of cyclodextrin.

[0016] By adopting the above technical solution, cyclodextrin is a product generated by acid decomposition and cyclization of starch, and has a hollow cylindrical structure. Adding cyclodextrin to the curing agent can, on the one hand, encapsulate heavy metal ions in the waste soil to prevent their dissolution and pollution; on the other hand, it can increase the cross-linking density, regulate moisture migration, delay curing shrinkage and cracking, and improve the strength of the cured soil.

[0017] In a second aspect, the present application provides a method for preparing a solidifying agent for waste soil treatment, which adopts the following technical solution: A method for preparing a solidifying agent for waste soil treatment comprises the following steps: S1. Mixing the raw materials except the organobentonite, calcium formate, calcium stearate, sodium hydroxide, and potassium carbonate at 60-80° C., then adding the organobentonite and stirring to obtain a mixture A. S2, stirring and mixing calcium formate, calcium stearate, sodium hydroxide and potassium carbonate to prepare mixture B; S3. Mixing mixture A and mixture B at 60-80° C. to prepare a solidifying agent for waste soil treatment.

[0018] By adopting the above technical solution and controlling the temperature, the moisture absorption of the curing agent during preparation can be reduced, thereby preventing it from absorbing moisture during preparation, prematurely cross-linking during storage, or agglomerating and cross-linking, which affects the effect during use and dispersion in the waste soil system.

[0019] In a second aspect, the present application provides an application of a solidifying agent for waste soil treatment, which adopts the following technical solution: An application of the curing agent for waste soil treatment, when the mass percentage of water in the waste soil is 45-65%, the mass ratio of the waste soil to the curing agent is (8-12):1.

[0020] By adopting the above-mentioned technical solution, the curing agent for waste soil treatment prepared in this application does not require pre-dissolution or pre-dehydration of the waste soil, which can greatly reduce the treatment cost; when used for waste soil with high moisture content, it can quickly absorb moisture and initiate a cross-linking reaction, shortening the construction period while ensuring its curing effect.

[0021] In summary, this application includes at least one of the following beneficial technical effects: 1. The curing agent of the present application is in a solid powder state. On the one hand, it is more convenient than liquid curing agents in storage and practical application. On the other hand, when it is in a solid powder state and added to waste soil with high moisture content, it can also consume part of the moisture by dissolving in it, thereby improving the curing effect. When some raw materials, such as sodium hydroxide, are dissolved in the waste soil, the paste releases heat, which can also accelerate the evaporation of water and increase the curing rate. On this basis, the present application also abandons the straight-chain polycarboxylic acid polymer cross-linking agent from the raw material and adopts a carboxyl-terminated hyperbranched polymer as a cross-linking agent. The hyperbranched polymer has better water solubility and lower molecular viscosity, making it easier to dissolve and evenly disperse in the waste soil system. The carboxyl groups contained are at the end, and the carboxyl groups contained can give full play to the cross-linking effect, increase the cross-linking density, and enhance the strength and durability of the waste soil after curing. Polyacrylamide is added as a flocculant to adsorb soil particles to form a flocculated structure, and cooperates with the organosilicon defoamer to greatly reduce the porosity in the waste soil and increase the density of the waste soil after curing. In addition, the organosilicon defoamer can increase the hydrophobicity of the waste soil, making the waste soil It is difficult for large water droplets to exist in the soil, which reduces the pore defects after solidification and improves the density and strength of the solidified soil after solidification and drying. Organic bentonite is an inorganic mineral / organic ammonium complex. It uses bentonite as raw material and utilizes the lamellar structure of montmorillonite in bentonite and its ability to swell and disperse into colloidal clay particles in water or organic solvents to absorb water to form a gel, thereby enhancing the plasticity and deformation resistance of the solidified soil and making the solidifying agent more suitable for soils with high water content. In addition, it cooperates with other cross-linking agents to increase the cross-linking density of the solidified soil and the drying shrinkage rate of the solidified soil. It did not show a significant improvement, and the organic bentonite can also play a role in delaying the settlement of the waste soil, can increase the cross-linking time, make the cross-linking more complete, and can also improve the strength of the solidified soil; calcium formate, calcium stearate, potassium carbonate and sodium hydroxide can adjust the pH of the waste soil to be alkaline, can promote the cross-linking of polyacrylamide, accelerate the curing reaction, and calcium stearate as a lubricant can also play a role in improving the construction performance; therefore, the curing agent of the present application can greatly improve the curing effect of waste soil with a high water content and improve the comprehensive performance of the waste soil after curing.

[0022] 2. The solidifying agent for waste soil treatment prepared in this application can achieve excellent solidification effect on waste soil with high water content; the drying shrinkage rate of the solidified soil formed by the solidifying agent for waste soil treatment in this application is between 0.24-0.33%, the water stability coefficient is higher than 0.97, and can reach up to 0.99, and the permeability coefficient is maintained at 1.12-1.23x10 -7 cm / s. At the same time, its unconfined compressive strength is above 3.4MPa and can reach up to 4.4MPa. DETAILED DESCRIPTION

[0023] The following is a further detailed description of this application in conjunction with the specific content.

[0024] raw material The raw materials used in the examples of the present application are all common commercially available products, among which the average molecular weight of polyacrylamide is 10 million, it is cationic, and the brand is BASF; the viscosity of hydroxypropyl methylcellulose is 20,000 mPa·s, and the brand is Shin-Etsu Chemical; the model of the powdered silicone defoamer is SAG 622, with a particle size range of 5-10 μm, and the brand is Dow Corning; the organic bentonite is purchased from Lingshou County Jinyuan Mining Processing Plant; sepiolite is purchased from Tianhe Chemical; the model of cyclodextrin is β-cyclodextrin, and it is purchased from Jiangxi Shengwei Chemical Technology Co., Ltd. Example

[0025] Example 1 A solidifying agent for waste soil treatment, the raw materials and the amounts of the raw materials are shown in Table 1, and the preparation method is as follows: S1. At 70° C., weigh the raw materials in the amounts listed in Table 1, mix a carboxyl-terminated hyperbranched polyester, polyacrylamide, hydroxypropyl methylcellulose, and a powdered silicone defoamer, add organic bentonite, and stir to prepare a mixture A; wherein the carboxyl-terminated hyperbranched polyester has a model of HyPer C103, an average molecular weight of 6400, and a carboxyl group number of 24 / mol; S2, stirring and mixing calcium formate, calcium stearate, sodium hydroxide and potassium carbonate to prepare mixture B; S3. Mixing mixture A and mixture B at 70° C. to prepare a solidifying agent for waste soil treatment.

[0026] Table 1 Raw materials and amounts of raw materials used in Example 1 (kg) Carboxyl-terminated hyperbranched polyester 35 calcium formate 3 polyacrylamide 30 Hydroxypropyl methylcellulose 10 calcium stearate 3 potassium carbonate 10 Sodium hydroxide 4 Powdered silicone defoamer 4 Organic bentonite 10 Example 2 A curing agent for waste soil treatment is different from Example 1 in that, among its raw materials, the model of the carboxyl-terminated hyperbranched polyester is HyPer C102, its average molecular weight is 2600, and the number of carboxyl groups is 12 / mol. The remaining steps are the same as those in Example 1.

[0027] Example 3 A curing agent for waste soil treatment is different from Example 1 in that, among its raw materials, the model of the carboxyl-terminated hyperbranched polyester is HyPer C104, its average molecular weight is 12,000, and the number of carboxyl groups is 48 / mol. The remaining steps are the same as those in Example 1.

[0028] Example 4 A curing agent for waste soil treatment, which differs from Example 1 in that its raw materials also include 3 kg of micron-sized sepiolite. When preparing the curing agent, the sepiolite is added to S1, and the average particle size of the sepiolite is 20 μm. The remaining steps are the same as Example 1.

[0029] Example 5 A solidifying agent for waste soil treatment is different from Example 4 in that its raw materials also include 5 kg of cyclodextrin, and the remaining steps are the same as Example 4.

[0030] Comparative Example Comparative Example 1 A curing agent for waste soil treatment is different from Example 1 in that no powdered silicone defoaming agent is added to its raw materials, and the remaining steps are the same as Example 1.

[0031] Comparative Example 2 A curing agent for waste soil treatment is different from Example 1 in that the end-carboxyl hyperbranched polyester added to the raw materials is replaced by an equal mass of polymethacrylic acid with the same average molecular weight, and the remaining steps are the same as Example 1.

[0032] Comparative Example 3 A solidifying agent for waste soil treatment is different from Example 1 in that organic bentonite is not added to its raw materials, and the remaining steps are the same as Example 1.

[0033] Performance testing Detection method / test method According to the preparation methods of Examples 1-5 and Comparative Examples 1-3, solidifying agents for waste soil treatment were prepared respectively, and then used to solidify shield mud. The test results of the solidified soil formed after solidification are shown in Table 2.

[0034] Take 100kg of shield mud, in which the mass percentage of water is 55%, and add 10kg of waste soil treatment curing agent while stirring. After the addition is completed, continue stirring for 30 minutes to form premixed solidified soil, and then cast and vibrate to form a mold size of 100mm x100mm x100mm. After standing for 24 hours, demould it and cover it with a film and maintain it at 20-30℃ for 28 days.

[0035] Table 2 Test results of Examples 1-5 and Comparative Examples 1-3 It can be seen from Examples 1-5 and Comparative Examples 1-3, as well as the test results in Table 2, that the solidifying agent for waste soil treatment prepared by the present application can achieve excellent solidification effect on waste soil with high water content; the drying shrinkage of the solidified soil formed by the solidifying agent for waste soil treatment of the present application is between 0.24-0.33%, the water stability coefficient is higher than 0.97, and can reach up to 0.99, and the permeability coefficient is maintained at 1.12-1.23x10 -7 cm / s. At the same time, its unconfined compressive strength is above 3.4MPa and can reach up to 4.4MPa.

[0036] Powdered silicone defoamers are easier to evenly disperse in waste soil systems, preventing stratification of liquid defoamers. They also reduce the risk of moisture absorption and caking during storage, extending the product's shelf life. They also work synergistically with polyacrylamide to improve the hydrophobicity of waste soil, making it less susceptible to large water droplets, reducing post-curing pore defects, and improving the density and strength of the cured soil after curing and drying. This is verified by the test data from Example 1 and Comparative Example 1.

[0037] The present application abandons the straight-chain polycarboxylic acid polymer cross-linking agent and adopts the carboxyl-terminated hyperbranched polymer as a cross-linking agent. The water solubility of the hyperbranched polymer is better, and its molecular viscosity is small, it is easier to dissolve and evenly disperse into the waste soil system, and the carboxyl group contained is at the end. The carboxyl group contained can give full play to the cross-linking effect, improve the cross-linking density, and enhance the strength and durability of the waste soil after solidification. The test data of Example 1 and Comparative Example 2 can be verified. In conjunction with Example 2-3, the low-molecular-weight carboxyl-terminated hyperbranched polyester has good fluidity, is easy to contact with soil particles, and has a fast reaction speed, but its molecular weight is too low and contains less carboxyl, which affects its cross-linking density; the high-molecular-weight carboxyl-terminated hyperbranched polyester can provide a higher cross-linking density, enhance the structural strength of the solidified soil, but the molecular weight is too high, and it is difficult to disperse, which can also cause the strength of the solidified soil to be limited; Therefore, when its molecular weight is in the range of 2600-12000, it is more suitable for the curing effect of this curing agent.

[0038] Organobentonite is an inorganic mineral / organic ammonium complex that uses bentonite as a raw material. It utilizes the lamellar structure of montmorillonite in bentonite and its ability to swell and disperse into colloidal clay particles in water or an organic solvent to absorb water to form a gel, thereby enhancing the plasticity and deformation resistance of the solidified soil. This makes the curing agent more suitable for high-water content soils. In addition, the organobentonite works in synergy with other cross-linking agents to increase the cross-linking density of the solidified soil, while the drying shrinkage of the solidified soil does not show a significant increase. In addition, the organobentonite can also delay the settlement of the waste soil, increase the cross-linking time, make the cross-linking more complete, and improve the strength of the solidified soil. This can be verified by the test data of Example 1 and Comparative Example 3.

[0039] It can be seen from the test data of Examples 1 and 4 that sepiolite is a fibrous hydrated magnesium silicate that absorbs water and becomes soft when it comes into contact with it. It can deform when the waste soil loses water during solidification, thereby better filling the pores, improving the strength of the solidified soil, and buffering the expansion and water loss shrinkage defects of bentonite. In addition, sepiolite has the advantages of high temperature resistance and strong salt resistance, which can improve the application of solidified soil in high temperature environments.

[0040] It can be seen from the test data of Example 1 and Example 5 that cyclodextrin is a product generated by acidolysis and cyclization of starch, and has a hollow cylindrical structure. Adding cyclodextrin to the curing agent can, on the one hand, encapsulate heavy metal ions in the waste soil to prevent their dissolution and pollution; on the other hand, it can increase the cross-linking density and regulate moisture migration, delay curing shrinkage and cracking, and improve the strength of the cured soil.

[0041] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A solidifying agent for waste soil treatment, characterized in that: The invention comprises the following raw materials in parts by weight: 30-40 parts of terminal carboxyl hyperbranched polyester, 2-4 parts of calcium formate, 25-35 parts of polyacrylamide, 7-13 parts of hydroxypropyl methylcellulose, 2-4 parts of calcium stearate, 8-12 parts of potassium carbonate, 2-6 parts of sodium hydroxide, 3-5 parts of organosilicon defoaming agent and 8-12 parts of organobentonite.

2. The solidifying agent for waste soil treatment according to claim 1, characterized in that: The organosilicon defoamer is a powdered organosilicon defoamer.

3. The solidifying agent for waste soil treatment according to claim 1, characterized in that: The average molecular weight of the carboxyl-terminated hyperbranched polyester is 2600-12000.

4. The solidifying agent for waste soil treatment according to claim 1, characterized in that: The waste soil treatment curing agent further comprises 1-5 parts by weight of sepiolite.

5. The solidifying agent for waste soil treatment according to claim 4, characterized in that: The average particle size of the sepiolite is 10-100 μm.

6. The solidifying agent for waste soil treatment according to claim 4, characterized in that: The waste soil treatment curing agent further comprises 3-7 parts by weight of cyclodextrin.

7. A method for preparing the solidifying agent for waste soil treatment according to any one of claims 1 to 6, characterized in that: It comprises the following preparation steps: S1. Mixing the raw materials except the organobentonite, calcium formate, calcium stearate, sodium hydroxide, and potassium carbonate at 60-80° C., then adding the organobentonite and stirring to obtain a mixture A. S2, stirring and mixing calcium formate, calcium stearate, sodium hydroxide and potassium carbonate to prepare mixture B; S3. Mixing mixture A and mixture B at 60-80° C. to prepare a solidifying agent for waste soil treatment.

8. Use of the solidifying agent for waste soil treatment according to any one of claims 1 to 6, characterized in that: When the mass percentage of water in the waste soil is 45-65%, the mass ratio of the waste soil to the curing agent is (8-12):1.

Images