Silt solidifying agent, preparation method and application

Abstract

This application discloses a sludge solidification agent, its preparation method, and its application, belonging to the field of sludge solidification technology. The sludge solidification agent comprises solid waste composite powder, a composite activator, and a microbial self-healing agent. The microbial self-healing agent is a chitosan-bentonite microcapsule loaded with Bacillus pasteurellii. The Bacillus pasteurellii is encapsulated within a protective layer composed of chitosan and bentonite using microencapsulation technology, thus maintaining dormancy and high activity during long-term storage. Through dual modification of the key components of the activator (hydrophobic microcapsules encapsulating water glass and surface passivated gypsum), the problems of pre-reaction and clumping failure due to moisture absorption in single-component powders are solved. The introduction of specific organic regulators (xanthan gum and casein) significantly improves the solidification effect on high-organic-matter sludge. Therefore, the sludge solidification agent provided in this application can achieve long-term microbial survival, dry-state stability of the activator, and efficient solidification of high-organic-matter sludge.

Description

Technical Field

[0001] This application relates to the field of sludge solidification technology, and in particular to a sludge solidification agent, its preparation method, and its application. Background Technology

[0002] River and lake dredging and industrial site cleanup often generate large amounts of silt, which typically has high water content, high organic matter content, and complex pollutant composition. Direct landfilling or disposal can easily lead to waste of land resources and secondary water pollution.

[0003] In recent years, the technology of co-stabilizing sludge using industrial solid waste (such as slag and fly ash) and microorganisms (such as Bacillus pasteurellii) has begun to attract attention. However, related technologies typically employ simple adsorption of bacterial solutions onto solid waste carriers or direct mixing with powders. This approach faces the following insurmountable technical bottlenecks in practical applications: 1. Difficulty in maintaining microbial activity for a long time: The activity of Bacillus pasteurellii will rapidly decline in a dry, highly alkaline powder environment, resulting in a short product shelf life and unstable curing and self-healing functions.

[0004] 2. Poor storage stability of single-component finished products: When activators containing hygroscopic components such as water glass and gypsum are premixed with microbial powder to form single-component finished products, they are very prone to pre-hydration reaction due to moisture absorption, which leads to the failure of activators, product caking, and thus complete loss of curing ability.

[0005] 3. Insufficient adaptability to high organic matter sludge: High organic matter content will coat solid waste particles, severely inhibiting the hydration reaction process. Ordinary activators lack a regulatory mechanism for organic matter, resulting in slow development of solidified body strength and low final strength.

[0006] Therefore, developing a single-component solidifying agent that can be stored stably for a long time, maintain high microbial activity, and effectively solidify sludge with high organic matter content is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] This application provides a sludge solidifying agent, its preparation method, and its application. The sludge solidifying agent can be stored stably for a long period, maintain high microbial activity, and effectively solidify high-organic-matter sludge. The technical solution is as follows: On one hand, a sludge solidifying agent is provided, the sludge solidifying agent comprising the following components in parts by weight: Solid waste composite powder 80-90 parts, composite activator 8-12 parts, microbial self-healing agent 2-5 parts; The microbial self-healing agent is a chitosan-bentonite microcapsule loaded with Bacillus pasteurellii. The composite activator comprises the following modified powder components by mass fraction: 40%~50% alkaline activator, 30%~40% sulfate activator, and 10%~20% organic regulator; The alkaline activator is prepared by compounding sodium hydroxide and solid water glass powder coated with hydrophobic microcapsules at a mass ratio of 1: (2~3). The solid water glass powder coated with hydrophobic microcapsules is made by adsorbing liquid water glass, spray drying it, and coating it with a hydrophobic calcium stearate film. The sulfate activator is prepared by compounding surface passivated anhydrous gypsum and aminosulfonate in a mass ratio of (2~4):1. The surface passivated anhydrous gypsum is prepared by calcining desulfurized gypsum at 180℃~200℃ and then modifying its surface with a silane coupling agent to be hydrophobic. The organic regulator is a compound of xanthan gum and casein in a mass ratio of 1:(0.5~2).

[0008] In one possible implementation, the bacterial concentration in the microorganism is 10. 8 CFU / g ~10 9 The microcapsules have an average particle size of 50 μm to 100 μm and a wall thickness of 5 μm to 15 μm, with a CFU / g concentration.

[0009] In another possible implementation, the mass ratio of chitosan to bentonite is 1:(1~3).

[0010] In another possible implementation, the solid waste composite powder is made by grinding industrial solid waste with a specific surface area ≥700 m² in the following mass fractions. 2 / kg composition: Steel slag 15%~25%, blast furnace slag 15%~25%, fly ash 15%~25%, concrete powder 10%~20%, and recycled construction waste powder 10%~20%.

[0011] On the other hand, a method for preparing a sludge solidifying agent is provided, wherein the sludge solidifying agent is as described in any of the above claims, and the preparation method includes: Preparation of solid waste composite powder; Preparation of composite activators; Preparation of microbial self-healing agents; The solid waste composite powder, the composite activator, and the microbial self-healing agent are mechanically mixed evenly under inert gas protection to obtain the sludge solidification agent.

[0012] In one possible implementation, the preparation of the solid waste composite powder includes: Steel slag, blast furnace slag, fly ash, concrete powder, and recycled construction waste powder are mixed, and the resulting solid waste mixture is ground to a specific surface area ≥ 400 m². 2 / kg; The solid waste mixture after grinding is further ground, and triethanolamine is added as a grinding aid during the grinding process. After grinding to the target fineness, the solid waste composite powder is obtained; wherein the particle size distribution of the solid waste composite powder satisfies D10 < 2 μm, D50 < 8 μm, and D97 < 30 μm.

[0013] In another possible implementation, the preparation of the composite activator includes: Preparation of solid water glass powder coated with hydrophobic microcapsules; Preparation of anhydrous plaster with passivated surface; Sodium hydroxide, solid water glass powder encapsulated in the hydrophobic microcapsules, anhydrous gypsum with passivated surface, aminosulfonate, xanthan gum, and casein are mixed evenly to obtain the composite activator.

[0014] In another possible implementation, the preparation of the hydrophobic microcapsule-coated solid water glass powder includes: Liquid water glass was mixed with nano-silica, sodium fluorosilicate was added, and solid microspheres were prepared by spray drying; wherein the inlet temperature of spray drying was 170℃~190℃. In a fluidized bed, the solid microspheres are coated with an ethanol solution of calcium stearate to obtain solid water glass powder coated with hydrophobic microcapsules.

[0015] In another possible implementation, the preparation of surface-passivated anhydrous gypsum includes: The desulfurized gypsum was calcined at 180℃~200℃ for 1h~3h, cooled to 80℃~100℃, and then sprayed with an ethanol solution of silane coupling agent to obtain the surface passivated anhydrous gypsum.

[0016] In another possible implementation, the preparation of the microbial self-healing agent includes: Chitosan was dissolved in an acetic acid solution to form a mixture; Add bentonite to the mixture; Then add Pasteurella multocida bacterial solution to make the concentration of Pasteurella multocida bacterial solution 10. 8 CFU / g ~10 9 CFU / g; Microcapsules with a particle size of 50 μm to 100 μm and a wall thickness of 5 μm to 15 μm were prepared by spray drying to obtain the microbial self-healing agent.

[0017] On the other hand, an application of a sludge solidifying agent in sludge solidification treatment is provided, the sludge solidifying agent being as described in any of the above claims.

[0018] This application provides a sludge solidification agent, which includes a solid waste composite powder, a composite activator, and a microbial self-healing agent. The microbial self-healing agent is a chitosan-bentonite microcapsule loaded with Bacillus pasteurellii. Microencapsulation technology encapsulates Bacillus pasteurellii within a protective layer composed of chitosan and bentonite, physically isolating it from the dry, alkaline powder environment, thus maintaining its dormancy and high activity during long-term storage. The composite activator includes an alkaline activator, a sulfate activator, and an organic regulator. Through dual modification of the key components of the activator (hydrophobic microcapsules encapsulating water glass and surface passivated gypsum), the problem of pre-reaction and clumping failure due to moisture absorption in single-component powders is solved, ensuring the chemical stability and ready-to-use nature of the product. By introducing specific organic regulators (xanthan gum and casein), this combination not only improves slurry flowability but also specifically adsorbs and encapsulates organic molecules in the sludge, weakening their inhibitory effect. Simultaneously, the partially hydrolyzed organic matter under alkaline conditions can serve as a nucleation template for hydration products, turning a "disadvantage" into a "benefit," significantly enhancing the solidification effect on high-organic-matter sludge. Therefore, through the synergistic effect of the above components, the sludge solidifying agent provided in this application enables long-term microbial survival, dry-state stability of the activator, and efficient solidification of high-organic-matter sludge. Detailed Implementation

[0019] To make the technical solution and advantages of this application clearer, the embodiments of this application will be described in further detail below.

[0020] River and lake dredging and industrial site cleanup generate large amounts of silt, which typically has high water content, high organic matter content, and complex pollutant composition. Traditional cement solidification methods are ineffective, costly, and have a large carbon footprint. Industrial solid wastes such as steel slag, mineral slag, and fly ash are widely used in the building materials industry, but the limited fineness of traditional grinding processes prevents them from fully utilizing their activity.

[0021] Sludge solidification technologies based on solid waste and microorganisms often focus on the formulation of compounds, neglecting the storage stability, activity retention, and adaptability to complex sludge issues that must be addressed to transform them into industrially scalable "products." In particular, the "simple adsorption-mixing" scheme shown in prior art CN118652077A cannot provide long-term effective microbial protection, and its activator components are extremely unstable in the mixed state. The inventive concept of this application stems from an insight into this deep-seated application bottleneck, rather than a simple combination of known technologies.

[0022] This application provides a high-performance sludge solidifying agent that integrates the synergistic activation of multiple solid wastes and the self-repair function of microorganisms. It aims to build a stable, efficient and easy-to-use single-component system through two core means: "physical isolation to protect microbial strains" and "chemical modification to stabilize the activator", thereby fundamentally solving the above-mentioned bottlenecks.

[0023] The sludge solidifying agent provided in this application embodiment comprises the following components in parts by weight: Solid waste composite powder 80-90 parts, composite activator 8-12 parts, microbial self-healing agent 2-5 parts; Among them, the microbial self-healing agent is a chitosan-bentonite microcapsule loaded with Bacillus pasteurellii; The composite activator comprises the following modified powder components in the indicated mass fractions: 40%–50% alkaline activator, 30%–40% sulfate activator, and 10%–20% organic regulator; The alkaline activator is composed of sodium hydroxide and solid water glass powder coated with hydrophobic microcapsules in a mass ratio of 1: (2~3). The solid water glass powder coated with hydrophobic microcapsules is made by adsorption, spray drying and external coating of liquid water glass with a hydrophobic calcium stearate film. The sulfate activator is a compound of surface passivated anhydrous gypsum and aminosulfonate in a mass ratio of (2~4):1. The surface passivated anhydrous gypsum is prepared by calcining desulfurized gypsum at 180℃~200℃ and then modifying its surface hydrophobicity with a silane coupling agent. The organic regulator is a compound of xanthan gum and casein in a mass ratio of 1:(0.5~2).

[0024] This application provides a sludge solidification agent, which includes a solid waste composite powder, a composite activator, and a microbial self-healing agent. The microbial self-healing agent is a chitosan-bentonite microcapsule loaded with Bacillus pasteurellii. Microencapsulation technology encapsulates Bacillus pasteurellii within a protective layer composed of chitosan and bentonite, physically isolating it from the dry, alkaline powder environment, thus maintaining its dormancy and high activity during long-term storage. The composite activator includes an alkaline activator, a sulfate activator, and an organic regulator. Through dual modification of the key components of the activator (hydrophobic microcapsules encapsulating water glass and surface passivated gypsum), the problem of pre-reaction and clumping failure due to moisture absorption in single-component powders is solved, ensuring the chemical stability and ready-to-use nature of the product. By introducing specific organic regulators (xanthan gum and casein), this combination not only improves slurry flowability but also specifically adsorbs and encapsulates organic molecules in the sludge, weakening their inhibitory effect. Simultaneously, the partially hydrolyzed organic matter under alkaline conditions can serve as a nucleation template for hydration products, turning a "disadvantage" into a "benefit," significantly enhancing the solidification effect on high-organic-matter sludge. Therefore, through the synergistic effect of the above components, the sludge solidifying agent provided in this application enables long-term microbial survival, dry-state stability of the activator, and efficient solidification of high-organic-matter sludge.

[0025] For example, the mass fractions of the solid waste composite powder can be 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, etc. The mass fractions of the composite activator can be 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, etc. The mass fractions of the microbial self-healing agent can be 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0026] The mass fraction of alkaline activator in composite activators can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, etc. The mass fraction of sulfate activator can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc. The mass fraction of organic regulator can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0027] The mass ratio of sodium hydroxide to hydrophobic microcapsule-coated solid water glass powder in alkaline activators can be 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, etc.

[0028] The mass ratio of surface-passivated anhydrous gypsum to aminosulfonate in the sulfate activator can be 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, etc. Optionally, the mass ratio of surface-passivated anhydrous gypsum to aminosulfonate is 3:1.

[0029] The mass ratio of xanthan gum to casein in the organic regulator can be 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, etc. Optionally, the mass ratio of xanthan gum to casein is 1:1.

[0030] The calcination temperature of the desulfurized gypsum for passivated anhydrous gypsum can be 180℃, 182℃, 185℃, 188℃, 190℃, 192℃, 195℃, 198℃, 200℃, etc.

[0031] In one possible implementation, the bacterial concentration in the microbial self-healing agent is 10. 8 CFU / g ~10 9 CFU / g, the average particle size of the microcapsules is 50μm~100μm, and the wall thickness is 5μm~15μm.

[0032] For example, the bacterial concentration can be 10. 8CFU / g, 10 8.1 CFU / g, 10 8.2 CFU / g, 10 8.3 CFU / g, 10 8.4 CFU / g, 10 8.5 CFU / g, 10 8.6 CFU / g, 10 8.7 CFU / g, 10 8.8 CFU / g, 10 8.9 CFU / g, 10 9 CFU / g, etc. The average particle size of the microcapsules can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc. The wall thickness of the microcapsules can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc.

[0033] In this embodiment, *Bacillus pasteurellii* is encapsulated within a chitosan-bentonite protective layer using microencapsulation technology, physically isolating it from the dry, alkaline powder environment, thus maintaining its dormancy and high activity during long-term storage. Furthermore, when cracks appear in the solidified body, the chitosan-bentonite microcapsules are activated by water, releasing *Bacillus pasteurellii* which utilizes urea hydrolysis to produce carbonate ions, which combine with calcium ions to form calcium carbonate precipitate, automatically filling the cracks. Experiments have shown that this system can repair cracks up to 0.8 mm wide within 28 days, restoring the permeability coefficient to over 90% of its pre-cracking level.

[0034] In one possible implementation, the mass ratio of chitosan to bentonite is 1:(1~3).

[0035] For example, the mass ratio of chitosan to bentonite can be 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, etc. Optionally, the mass ratio of chitosan to bentonite is 1:2.

[0036] In this embodiment, bentonite provides a large specific surface area and a layered structure, serving as the primary carrier for bacteria and significantly increasing the loading capacity of *Bacillus pasteurellosis*. Chitosan acts as a binder and film-forming agent, binding the bentonite particles together to form a microcapsule framework with sufficient mechanical strength, preventing structural collapse. When the mass ratio of both is within the aforementioned range, the microcapsules can swell and release bacteria quickly upon contact with water while maintaining structural integrity, meeting the time-sensitive requirements for self-healing cracks.

[0037] In one possible implementation, the solid waste composite powder is made by grinding industrial solid waste with the following mass fractions to a specific surface area ≥700 m².2 Composition per kg (approximately 800-1000 mesh): Steel slag 15%~25%, blast furnace slag 15%~25%, fly ash 15%~25%, concrete powder 10%~20%, and recycled construction waste powder 10%~20%.

[0038] For example, the mass fraction of steel slag can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, etc. The mass fraction of blast furnace slag can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, etc. The mass fraction of fly ash can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, etc. The mass fraction of concrete powder can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc. The mass fraction of recycled construction waste powder can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0039] Steel slag is a byproduct of the steelmaking process, composed of various oxides formed by the oxidation of impurities such as silicon, manganese, phosphorus, and sulfur in pig iron during smelting, as well as salts formed by the reaction of these oxides with solvents. Its main chemical components include 40%–60% calcium oxide (CaO), 3%–10% magnesium oxide (MgO), and iron oxide, etc. The mineral composition is mainly tricalcium silicate, followed by dicalcium silicate, RO phase, etc.

[0040] Blast furnace slag, also known as blast furnace slag, is a byproduct of the blast furnace ironmaking process. During ironmaking, impurities such as silica and alumina in iron ore react with lime and other materials to form a molten substance mainly composed of silicates and aluminosilicates. After quenching, it becomes a loose, porous granular material. Its main chemical components include CaO, SiO2, Al2O3, and MgO.

[0041] Fly ash is a fine fly ash collected from the flue gas of coal combustion in thermal power plants, and it has very good pozzolanic activity. Its main chemical components are Al2O3 (about 40%) and SiO2 (about 35%), and its mineral phase includes glass (50%~80%), quartz and mullite, etc.

[0042] Concrete micropowder originates from scraps, defective products, or waste materials from the production process of autoclaved aerated concrete (AAC) blocks / slabs. AAC itself is made primarily from slag waste stone powder (70-75%), gypsum, lime, cement, and other raw materials. Therefore, the main components of its micropowder are SiO2, CaO, etc., which have a certain degree of hydraulic activity.

[0043] Construction waste recycled micro powder consists of particles with a diameter of less than 75 μm, produced during the preparation of recycled aggregates from construction waste, primarily composed of concrete, bricks, and tiles. Its main chemical composition is similar to fly ash, primarily consisting of SiO2, CaO, and Al2O3, and it possesses certain potential activity.

[0044] In this embodiment of the application, various industrial solid wastes are ultrafinely ground to the micro-nano scale (specific surface area 700m²). 2 / kg), significantly improving particle activity and reaction interface. The complementary chemical compositions of different solid wastes, under the action of composite activators, undergo synergistic hydration reactions, generating more CSH gel, ettringite, and other hydration products, forming a dense microstructure. Furthermore, using ultrafine industrial solid waste as the main raw material, high-value utilization of waste is achieved; compared with traditional cement solidification, carbon emissions are reduced by more than 50%, and costs are reduced by 30% to 40%.

[0045] On the other hand, this application provides a method for preparing a sludge solidifying agent, the method comprising: Step 1: Prepare solid waste composite powder.

[0046] In this embodiment, the preparation of the ultrafine multi-solid waste composite powder adopts a "multi-stage series ultrafine grinding process", and the specific steps are as follows: Step (1): Mix steel slag, blast furnace slag, fly ash, concrete powder, and recycled construction waste powder, and grind the mixed solid waste mixture to a specific surface area ≥ 400 m². 2 / kg.

[0047] Steel slag, blast furnace slag, fly ash, concrete powder, and recycled construction waste powder are fed into a vertical mill or roller press, and the mixed solid waste is ground to a specific surface area ≥400 m². 2 / kg.

[0048] Step (2): The solid waste mixture after grinding is further ground, and triethanolamine is added as a grinding aid during the grinding process. After grinding to the target fineness, solid waste composite powder is obtained.

[0049] A closed-circuit system consisting of a high-efficiency vortex mill and an ultrafine classifier is used to further grind the solid waste mixture after grinding. During the grinding process, 0.5% to 1% of the powder mass is added as a grinding aid to improve grinding efficiency and enhance particle surface activity. After grinding to the target fineness, solid waste composite powder is obtained.

[0050] The particle size distribution of the solid waste composite powder satisfies D10 < 2 μm, D50 < 8 μm, and D97 < 30 μm.

[0051] For example, the amount of triethanolamine used can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% of the powder mass, etc.

[0052] Step 2: Prepare composite activator.

[0053] This step can be achieved through the following steps (1) to (3), including: (1) Preparation of solid water glass powder coated with hydrophobic microcapsules.

[0054] Liquid water glass was mixed with nano-silica, sodium fluorosilicate was added, and the mixture was spray-dried to form solid microspheres. In a fluidized bed, the solid microspheres were coated with an ethanol solution of calcium stearate to obtain solid water glass powder with hydrophobic microcapsules.

[0055] The mass ratio of liquid water glass to nano-silica is (4~6):1. For example, the mass ratio of liquid water glass to nano-silica can be 4:1, 4.2:1, 4.5:1, 4.8:1, 5:1, 5.2:1, 5.5:1, 5.8:1, 6:1, etc. Optionally, the mass ratio of liquid water glass to nano-silica is 5:1.

[0056] The amount of sodium fluorosilicate added is 1% to 2% of the mass of liquid water glass. For example, the amount of sodium fluorosilicate added can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, etc., of the mass of liquid water glass. Optionally, the amount of sodium fluorosilicate added is 1.5% of the mass of liquid water glass.

[0057] The mass of calcium stearate in the ethanol solution is 4% to 6% of the mass of the solid microspheres. For example, the mass of calcium stearate can be 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, etc., of the solid microspheres. Optionally, the mass of calcium stearate is 5% of the mass of the solid microspheres.

[0058] The inlet temperature of spray drying can be 170℃~190℃. For example, the inlet temperature of spray drying can be 170℃, 172℃, 175℃, 178℃, 180℃, 182℃, 185℃, 188℃, 190℃, etc.

[0059] Furthermore, the modulus of liquid water glass is 2.5 to 3. For example, the modulus of liquid water glass can be 2.5, 2.6, 2.7, 2.8, 2.9, 3, etc. Optionally, the modulus of liquid water glass is 2.8. Here, the modulus of liquid water glass refers to the molar ratio of SiO2 to Na2O in the solution.

[0060] (2) Prepare anhydrous gypsum with passivated surface.

[0061] The desulfurized gypsum was calcined at 180℃~200℃ for 1h~3h, then cooled to 80℃~100℃, and an ethanol solution of silane coupling agent was sprayed in. The mixture was stirred at high speed to make it uniformly coated, thus obtaining anhydrous gypsum with a passivated surface.

[0062] The calcination time can be 1h, 1.2h, 1.5h, 1.8h, 2h, 2.2h, 2.5h, 2.8h, 3h, etc. Optionally, the calcination time can be 2h.

[0063] Cooling temperatures can be 80℃, 82℃, 85℃, 88℃, 90℃, 95℃, 98℃, 100℃, etc. Optionally, the cooling temperature can be 90℃.

[0064] The mass of the silane coupling agent can be 0.5% to 1.5% of the mass of the desulfurized gypsum. For example, the mass of the silane coupling agent can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, etc., of the desulfurized gypsum. Optionally, the mass of the silane coupling agent can be 1% of the mass of the desulfurized gypsum.

[0065] The type of silane coupling agent can be set and changed as needed, and there is no specific limitation on it. For example, the silane coupling agent is KH-550.

[0066] It should be noted that the order of steps (1) and (2) can be set and changed as needed, and no specific restrictions are imposed on this.

[0067] (3) Sodium hydroxide, hydrophobic microcapsule-coated solid water glass powder, surface passivated anhydrous gypsum, aminosulfonate, xanthan gum and casein are mixed evenly to obtain a composite activator.

[0068] In one possible implementation, sodium hydroxide, hydrophobic microcapsule-coated solid water glass powder, surface-passivated anhydrous gypsum, aminosulfonate, xanthan gum, and casein are directly mixed uniformly in the corresponding mass ratio to obtain a composite activator.

[0069] In another possible implementation, sodium hydroxide is mixed with hydrophobic microcapsule-coated solid water glass powder at a mass ratio of 1:(2~3) to obtain an alkaline activator; surface passivated anhydrous gypsum is mixed with aminosulfonate at a mass ratio of (2~4):1 to obtain a sulfate activator; xanthan gum and casein are mixed at a mass ratio of 1:(0.5~2) to obtain an organic regulator; and the alkaline activator, sulfate activator and organic regulator are mixed evenly to obtain a composite activator.

[0070] In this implementation, sodium hydroxide and hydrophobic microcapsule-encapsulated solid water glass powder are mixed uniformly in a dry nitrogen environment with a dew point temperature < -30°C to obtain an alkaline activator. Passivated anhydrous gypsum and aminosulfonate are mixed uniformly in a dry nitrogen environment with a dew point temperature < -30°C to obtain a sulfate activator. Xanthan gum and casein are mixed uniformly in a dry nitrogen environment with a dew point temperature < -30°C to obtain an organic regulator. The alkaline activator, sulfate activator, and organic regulator are mixed uniformly in a dry nitrogen environment with a dew point temperature < -30°C to obtain a composite activator.

[0071] After obtaining the composite activator, it can be packaged in an aluminum-plastic composite vacuum bag with a built-in 3A molecular sieve dryer and a vacuum degree of <-0.095MPa.

[0072] Step 3: Prepare microbial self-healing agents.

[0073] Chitosan was dissolved in acetic acid solution to form a mixture; bentonite was added to the mixture; then Bacillus pasteurellium culture was added to make the concentration of Bacillus pasteurellium culture 10. 8 CFU / g ~10 9 CFU / g; Microcapsules with a particle size of 50μm~100μm and a wall thickness of 5μm~15μm were prepared by spray drying to obtain a microbial self-healing agent.

[0074] The process involves dissolving chitosan in a 1% acetic acid solution to form a 2% (w / w) mixture; adding bentonite to the mixture at a chitosan-to-bentonite mass ratio of 1:(1~3), and after thorough dispersion, adding Bacillus pasteurellium culture to achieve a final culture concentration of 10%. 8 CFU / g ~10 9 The CFU / g was used to prepare microcapsules by spray drying, thus obtaining a microbial self-healing agent.

[0075] In this step, the inlet temperature of the spray drying process can be the same as or different from the inlet temperature of the spray drying process for preparing the hydrophobic microcapsule-coated solid water glass powder in step 2; no specific limitation is made in this regard. For example, the inlet temperature of the spray drying process in this step can be the same as the inlet temperature of the spray drying process for preparing the hydrophobic microcapsule-coated solid water glass powder in step 2, which is 170℃~190℃.

[0076] It should be noted that this application does not specify the order of execution for steps 1, 2, and 3 above. In practical applications, the composite activator can be prepared first, followed by the microbial self-healing agent, and finally the solid waste composite powder; that is, step 2 can be performed first, followed by step 3, and finally step 1. Alternatively, the solid waste composite powder can be prepared first, followed by the microbial self-healing agent, and finally the composite activator; that is, step 1 can be performed first, followed by step 3, and finally step 2.

[0077] Step 4: Mechanically mix the solid waste composite powder, composite activator, and microbial self-healing agent evenly under inert gas protection to obtain sludge solidification agent.

[0078] The inert gas can be nitrogen, helium, or other types of gas, without specific limitations.

[0079] The core innovation of the sludge solidification agent provided in this application lies in the construction of a synergistic and stable "microcapsule-modified activator" system: By encapsulating Bacillus pasteurellii within a protective layer composed of chitosan and bentonite using microencapsulation technology, it is physically isolated from the dry, alkaline powder environment of the outside world, thus maintaining dormancy and high activity during long-term storage.

[0080] By dual modification of the key components of the activator (hydrophobic microcapsule-coated water glass and surface passivated gypsum), the problem of pre-reaction and clumping failure of single-component powder due to moisture absorption is completely solved, ensuring the chemical stability and ready-to-use nature of the product.

[0081] By introducing specific organic regulators (xanthan gum and casein), this combination can not only improve the fluidity of the slurry, but also specifically adsorb and encapsulate organic molecules in the sludge, weakening their inhibitory effect. At the same time, the partially hydrolyzed organic matter in the alkaline environment can become a nucleation template for hydration products, turning "disadvantage" into "advantage", and significantly improving the solidification effect on high organic matter sludge.

[0082] It is evident that this system is not a simple patchwork of related technologies. Although those skilled in the art have common knowledge of using microcapsules or hydrophobic modification, it is difficult to foresee that when it is systematically applied to the complex scenario of "microorganism-hygroscopic activator-high organic matter system", it can produce a synergistic effect of "1+1+1>3": that is, it simultaneously achieves the long-term survival of microorganisms, the dry stability of activator and the efficient solidification of high organic matter sludge, and finally successfully prepares a single-component finished product that can be used directly and has stable performance. This constitutes the non-obvious substantive feature of this application relative to related technologies.

[0083] On the other hand, this application provides an application of a sludge solidifying agent in sludge solidification treatment.

[0084] When using the aforementioned sludge solidifying agent, add the sludge solidifying agent to the sludge at 8% to 15% of the dry sludge mass, then mix it evenly using a high-efficiency mixing device, fill it in layers and compact it to the designed density; during the curing period, keep the surface moist by covering it with a film to promote microbial activity.

[0085] The mass of the silt solidifying agent can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% of the dry silt mass, etc.

[0086] In summary, compared with related technologies, the sludge solidification agent provided in this application has the following beneficial effects: (1) Excellent storage stability and activity retention: Through innovative microencapsulation and hydrophobic modification technology of activator, the single-component curing agent of this application has no clumping phenomenon after accelerated aging (40℃, 80%RH) equivalent to 3 months of storage at room temperature, microbial survival rate >90%, curing strength retention rate >96%, which solves the long-standing storage and transportation problems in the industry.

[0087] (2) High-efficiency solidification of sludge with high organic matter content: The unique organic regulator (xanthan gum / casein) can effectively shield the interference of organic matter, so that the solidifier can still achieve excellent results of 7-day unconfined compressive strength ≥1.5MPa and 28-day strength ≥3.0MPa for sludge with organic matter content as high as 15%.

[0088] (3) Durable self-healing ability: The protected microorganisms are activated when the cracks are exposed to water and can autonomously repair cracks up to 0.8 mm wide within 28 days. The permeability coefficient recovery rate is >90%, which greatly improves the durability of the project.

[0089] (4) Significant environmental and economic benefits: Using industrial solid waste as the main raw material, carbon emissions are reduced by more than 50% and costs are reduced by 30% to 40% compared with traditional cement. Moreover, the single-component form simplifies the construction process.

[0090] To make the technical solution and advantages of this application clearer, they will be described in detail below through specific embodiments.

[0091] In the following specific embodiments, operations without specified conditions are performed under standard conditions or conditions recommended by the manufacturer. Raw materials without specified manufacturers and specifications are all commercially available products.

[0092] Example 1 Example 1 provides a sludge solidification agent, which comprises the following components in parts by weight: solid waste composite powder (specific surface area 750 m²). 2 85 parts ( / kg), 10 parts compound activator, and 5 parts microbial self-repair agent.

[0093] The solid waste composite powder includes the following components by mass fraction: 25% steel slag, 25% blast furnace slag, 20% fly ash, 15% concrete powder, and 15% recycled construction waste powder.

[0094] The composite activator comprises the following components in the indicated mass fractions: 50% alkaline activator, 40% sulfate activator, and 10% organic regulator. The alkaline activator consists of 1.5 parts sodium hydroxide and 3.5 parts hydrophobic microcapsule-coated solid water glass powder; the sulfate activator consists of 3.0 parts surface-passivated anhydrous gypsum and 1.0 part aminosulfonate; and the organic regulator consists of 0.5 parts xanthan gum and 0.5 parts casein.

[0095] The microbial self-healing agent is a chitosan-bentonite microcapsule loaded with Bacillus pasteurellii, wherein the bacterial concentration is 10. 9 The chitosan to bentonite mass ratio is 1:2, the average particle size of the microcapsules is 80 μm, and the wall thickness is 10 μm.

[0096] The preparation method of this sludge solidification agent is as follows: Step 1: Prepare solid waste composite powder.

[0097] Steel slag, blast furnace slag, fly ash, concrete powder, and recycled construction waste powder are mixed and ground in a vertical mill to a specific surface area ≥ 400 m². 2 / kg, using a closed-circuit system consisting of a high-efficiency vortex mill and an ultrafine classifier, the solid waste mixture after grinding is further ground. During the grinding process, 1% of the powder mass of triethanolamine is added as a grinding aid to improve grinding efficiency and enhance particle surface activity. After grinding to the target fineness, solid waste composite powder is obtained.

[0098] The particle size distribution of the solid waste composite powder satisfies D10 < 2 μm, D50 < 8 μm, and D97 < 30 μm.

[0099] Step 2: Prepare composite activator.

[0100] (1) Liquid water glass with a modulus of 2.8 was mixed with nano-silica at a mass ratio of 5:1, and sodium fluorosilicate of 1.5% by mass of the liquid water glass was added. The mixture was then spray-dried (inlet temperature of 180℃) to form solid microspheres. Subsequently, the mixture was coated in a fluidized bed with an ethanol solution of 5% calcium stearate (by mass of the solid microspheres) to obtain solid water glass powder coated with hydrophobic microcapsules.

[0101] (2) Calcine the desulfurized gypsum at 190°C for 2 hours. When it is cooled to 90°C, spray in an ethanol solution of KH-550 silane coupling agent at 1% of the mass of the desulfurized gypsum. Stir at high speed to make it uniformly coated, and obtain anhydrous gypsum with passivated surface.

[0102] (3) Sodium hydroxide and hydrophobic microcapsule-coated solid water glass powder were mixed evenly at a mass ratio of 1:2 in a dry nitrogen environment with a dew point temperature < -30℃ to obtain an alkaline activator. Surface-passivated anhydrous gypsum and aminosulfonate were mixed evenly at a mass ratio of 3:1 in a dry nitrogen environment with a dew point temperature < -30℃ to obtain a sulfate activator. Xanthan gum and casein were mixed evenly at a mass ratio of 1:1 in a dry nitrogen environment with a dew point temperature < -30℃ to obtain an organic regulator. The alkaline activator, sulfate activator, and organic regulator were mixed evenly in a dry nitrogen environment with a dew point temperature < -30℃ to obtain a composite activator.

[0103] The composite activator is packaged in an aluminum-plastic composite vacuum bag with an internal 3A molecular sieve desiccant, and the vacuum degree is <-0.095MPa.

[0104] Step 3: Prepare microbial self-healing agents.

[0105] Chitosan was dissolved in a 1% acetic acid solution to form a 2% (w / w) mixture. Bentonite was then added to the mixture at a chitosan to bentonite mass ratio of 1:2. After thorough dispersion, Bacillus pasteurellium culture was added to bring the final culture concentration to 10%. 9 Microcapsules with a particle size of 80 μm and a wall thickness of 10 μm were prepared by spray drying at CFU / g, thus obtaining the microbial self-healing agent.

[0106] Step 4: Mechanically mix the solid waste composite powder, composite activator and microbial self-healing agent evenly under nitrogen protection to obtain sludge solidification agent.

[0107] Example 2 Example 2 provides a sludge solidification agent. The solid waste composite powder, composite activator, and microbial self-healing agent in this sludge solidification agent are the same as the corresponding components in Example 1. The difference is that the mass fraction of the solid waste composite powder is 88 parts, and the mass fraction of the microbial self-healing agent is 2 parts, as shown in Table 2.

[0108] The preparation method can be found in Example 1, and will not be repeated here.

[0109] Example 3 Example 3 provides a sludge solidification agent. The solid waste composite powder, composite activator, and microbial self-healing agent in this sludge solidification agent are the same as the corresponding components in Example 1. The difference is that the mass fraction of the solid waste composite powder is 83 parts, and the mass fraction of the composite activator is 12 parts. See Table 2 for further details.

[0110] The preparation method can be found in Example 1, and will not be repeated here.

[0111] Comparative Example 1 Comparative Example 1 provides a sludge solidification agent. The difference between this sludge solidification agent and Example 1 is that the same concentration of Bacillus pasteurellium bacterial solution is directly adsorbed onto an equal amount of solid waste composite powder (unencapsulated), and then mixed with an unmodified activator (ordinary water glass powder, untreated gypsum). Otherwise, it is the same as Example 1.

[0112] Comparative Example 2 Comparative Example 2 provides a sludge curing agent that differs from Example 1 in that it uses unmodified water glass powder and unpassivated gypsum, while otherwise being the same as Example 1.

[0113] Comparative Example 3 Comparative Example 3 provides a sludge solidifying agent that differs from Example 1 in that the composite activator does not contain xanthan gum and casein, but is otherwise the same as Example 1.

[0114] Comparative Example 4 Comparative Example 4 used traditional cement as a sludge solidifying agent.

[0115] Performance testing To demonstrate the inventiveness of this application, a series of comparative experiments were designed.

[0116] Test 1: Comparison of long-term survival rates of microorganisms Sample A: Sludge solidifying agent prepared in Example 1.

[0117] Sample B: Sludge solidifying agent prepared in Comparative Example 1.

[0118] Samples A and B were placed in an environment of 40℃ and 80%RH for accelerated aging, and samples were taken periodically to test the number of viable bacteria. The test results are shown in Table 1.

[0119] Table 1

[0120] As can be seen from the data in Table 1, microencapsulation technology provides a crucial physical barrier for the bacteria, enabling them to maintain a survival rate of over 90% in harsh, dry, alkaline environments. In contrast, simple adsorption methods result in a loss of over 96% of bacterial activity within one month, demonstrating that the protective measures proposed in this application are fundamental and not obvious.

[0121] Test 2: Storage Stability Test Sample C: Sludge solidifying agent prepared in Example 1.

[0122] Sample D: Sludge solidifying agent prepared in Comparative Example 2.

[0123] The sludge solidifying agents prepared in groups C and D were placed in a constant temperature and humidity chamber at 40℃ and 80% relative humidity for accelerated aging tests. Furthermore, the accelerated-aged sludge solidifying agent was added at a dosage of 12% (relative to the dry weight of the sludge) to river sludge with high organic matter (12%) and high water content (60%) to prepare standard samples. These samples were cured under standard conditions, and their compressive strength was tested. The results are shown in Table 2.

[0124] As shown in Table 2, the targeted hydrophobic modification of water glass and gypsum effectively prevents moisture absorption and pre-hydration, which is key to ensuring the performance of the single-component product does not degrade during storage. Under harsh conditions equivalent to approximately 3 months of storage at room temperature, the unmodified product completely fails due to internal pre-reaction. The sludge curing agent provided in Example 1, however, maintains good physical state and core mechanical properties, with an unconfined compressive strength of 1.82±0.15 MPa at 7 days and 3.25±0.20 MPa at 28 days, exhibiting a strength retention rate of over 96%, far exceeding industry standards (typically requiring a strength retention rate >90% after 3 months).

[0125] Test 3: Comparison of solidification effects on high organic matter sludge Sample E: The sludge solidifying agent prepared in Example 1, containing xanthan gum / casein organic regulator.

[0126] Sample F: Sludge solidifying agent prepared in Comparative Example 3.

[0127] River silt with an organic matter content of 12% was selected for solidification effect testing. The test results are shown in Table 3.

[0128] Table 3

[0129] As can be seen from the data in Table 3, the combined use of xanthan gum and casein is not simply a thickening agent, but rather significantly improves the system's adaptability to high-organic-matter sludge, demonstrating the synergistic effect of this specific combination in the system.

[0130] Test 4: Self-healing effect test Sample G: Sludge solidifying agent prepared in Example 1.

[0131] Pre-cracking was performed on samples cured for 28 days, resulting in cracks with an average width of 0.5 mm. After another 28 days of curing, evaluation was conducted using microscopic observation and permeability testing: the self-healing rate of the cracks was >92%, and the permeability recovery rate was 8.5 × 10⁻⁶ after cracking. -5 cm / s recovered to 2.1×10 -7 cm / s, recovered to more than 92% of the initial value.

[0132] This application also tested the sludge solidifying agents provided in Examples 2, 3, 2, and 4. The sludge solidifying agents were subjected to accelerated aging for 30 days, and their 28-day strength was tested. See Table 4 for further details.

[0133]

[0134] As shown in Table 4, the sludge solidifying agents provided in Examples 1, 2, and 3 exhibit superior performance compared to Comparative Examples 2 and 4. The sludge solidifying agents prepared in Examples 1 to 3 not only possess high strength but also a high self-healing rate of cracks. In contrast, the sludge solidifying agent provided in Comparative Example 2 uses an unmodified activator, which fails due to severe pre-hydration during storage, resulting in significant strength loss. This underscores the importance of the modification technology presented in this application. The traditional cement used in Comparative Example 4 is unsuitable for high-organic-matter sludge, exhibiting low strength and lacking self-healing capabilities.

[0135] This application also compares the sludge solidifying agent provided in Example 1 with two commercially available mainstream sludge solidifying agents. All sludge solidifying agents were used to treat the same batch of sludge at a dosage of 12%. The results are shown in Table 5.

[0136] Table 5

[0137] As can be seen from Table 5, the curing agent provided in this application exhibits significant advantages in terms of comprehensive performance and adaptability, especially in terms of storage stability and self-healing function, which are not found in commercially available products.

[0138] The above description is only for the purpose of enabling those skilled in the art to understand the technical solution of this application, and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A sludge solidifying agent, characterized in that, The sludge solidifying agent comprises the following components in parts by weight: Solid waste composite powder 80-90 parts, composite activator 8-12 parts, microbial self-healing agent 2-5 parts; The microbial self-healing agent is a chitosan-bentonite microcapsule loaded with Bacillus pasteurellii. The composite activator comprises the following modified powder components by mass fraction: 40%~50% alkaline activator, 30%~40% sulfate activator, and 10%~20% organic regulator; The alkaline activator is prepared by compounding sodium hydroxide and solid water glass powder coated with hydrophobic microcapsules at a mass ratio of 1: (2~3). The solid water glass powder coated with hydrophobic microcapsules is made by adsorbing liquid water glass, spray drying it, and coating it with a hydrophobic calcium stearate film. The sulfate activator is prepared by compounding surface passivated anhydrous gypsum and aminosulfonate in a mass ratio of (2~4):

1. The surface passivated anhydrous gypsum is prepared by calcining desulfurized gypsum at 180℃~200℃ and then modifying its surface with a silane coupling agent to be hydrophobic. The organic regulator is a compound of xanthan gum and casein in a mass ratio of 1:(0.5~2).

2. The sludge solidifying agent according to claim 1, characterized in that, The bacterial concentration in the microbial self-healing agent is 10. 8 CFU / g ~10 9 The microcapsules have an average particle size of 50 μm to 100 μm and a wall thickness of 5 μm to 15 μm, with a CFU / g concentration.

3. The sludge solidifying agent according to claim 2, characterized in that, The mass ratio of chitosan to bentonite is 1:(1~3).

4. The sludge solidifying agent according to claim 1, characterized in that, The solid waste composite powder is made from industrial solid waste with the following mass fractions, ground to a specific surface area ≥700 m². 2 / kg composition: Steel slag 15%~25%, blast furnace slag 15%~25%, fly ash 15%~25%, concrete powder 10%~20%, and recycled construction waste powder 10%~20%.

5. A method for preparing a sludge solidifying agent, characterized in that, The sludge solidifying agent is as described in any one of claims 1 to 4, and the preparation method comprises: Preparation of solid waste composite powder; Preparation of composite activators; Preparation of microbial self-healing agents; The solid waste composite powder, the composite activator, and the microbial self-healing agent are mechanically mixed evenly under inert gas protection to obtain the sludge solidification agent.

6. The preparation method according to claim 5, characterized in that, The preparation of the composite activator includes: Preparation of solid water glass powder coated with hydrophobic microcapsules; Preparation of anhydrous plaster with passivated surface; Sodium hydroxide, solid water glass powder encapsulated in the hydrophobic microcapsules, anhydrous gypsum with passivated surface, aminosulfonate, xanthan gum, and casein are mixed evenly to obtain the composite activator.

7. The preparation method according to claim 6, characterized in that, The preparation of the hydrophobic microcapsule-coated solid water glass powder includes: Liquid water glass was mixed with nano-silica, sodium fluorosilicate was added, and solid microspheres were prepared by spray drying; wherein the inlet temperature of spray drying was 170℃~190℃. In a fluidized bed, the solid microspheres are coated with an ethanol solution of calcium stearate to obtain solid water glass powder coated with hydrophobic microcapsules.

8. The preparation method according to claim 6, characterized in that, The preparation of surface-passivated anhydrous gypsum includes: The desulfurized gypsum was calcined at 180℃~200℃ for 1h~3h, cooled to 80℃~100℃, and then sprayed with an ethanol solution of silane coupling agent to obtain the surface passivated anhydrous gypsum.

9. The preparation method according to claim 5, characterized in that, The preparation of the microbial self-healing agent includes: Chitosan was dissolved in an acetic acid solution to form a mixture; Add bentonite to the mixture; Then add Pasteurella multocida bacterial solution to bring the concentration of Pasteurella multocida bacterial solution to 10. 8 CFU / g ~10 9 CFU / g; Microcapsules with a particle size of 50 μm to 100 μm and a wall thickness of 5 μm to 15 μm were prepared by spray drying to obtain the microbial self-healing agent.

10. The application of a sludge solidifying agent in sludge solidification treatment, characterized in that, The sludge solidifying agent is as described in any one of claims 1 to 4.

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