Nano composite filling material based on in-situ acid-base mutual modification enhancement and application thereof

Abstract

The invention belongs to the technical field of industrial solid waste resource recycling, and discloses a nano composite filling material based on in-situ acid-base mutual modification enhancement and application thereof. According to the nano composite filling material, the alkalinity of the red mud and the acidity of the desulfurized gypsum are used for neutralization, the alkalinity of a system is reduced, a synergistic reaction is excited, a large number of ettringite crystals playing a key enhancing role are generated under the regulation and control of a nano material, and the ettringite crystals and a geopolymer form an interpenetrating network structure. The obtained slurry is low-viscosity and high-fluidity Newtonian fluid (diffusivity gt and 250 mm), the 7-day strength is larger than 2.0 MPa, the pH value is 7-9, and the fluorine ion concentration is lt; and the leaching of heavy metal ions is qualified, and the method is environment-friendly and safe. Efficient resource utilization of the red mud and the desulfurized gypsum is achieved, and the method is simple in process, low in cost and especially suitable for mine filling and engineering backfilling.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of industrial solid waste resource recycling, and particularly relates to a nano-composite filling material based on in-situ acid-base mutual modification enhancement and application thereof. BACKGROUND

[0002] Red mud is a strong alkaline solid waste produced by the alumina industry, and its large-scale storage not only occupies land, but also poses a continuous threat to the ecological environment due to its high alkalinity, fluorides and potential heavy metal ions. The existing disposal method of red mud is mainly storage, and the channel for resource utilization is narrow, so it is urgent to develop a large-scale way to dispose of red mud. Desulfurization gypsum is a by-product of flue gas desulfurization in coal-fired power plants, and its main component is calcium sulfate dihydrate (CaSO4·2H2O), which is weakly acidic and also faces the problems of storage and utilization.

[0003] In the fields of mine filling and foundation backfilling, traditional filling materials often use cement as the main cementing agent, which is costly and has high carbon emissions. In recent years, some studies have attempted to use red mud or desulfurization gypsum to prepare filling materials, but all have significant defects: when red mud is used alone, its strong alkalinity (pH>12) will result in poor material fluidity, poor long-term volume stability, and high risk of harmful ion leaching; when desulfurization gypsum is used alone, it has the problems of slow setting and low early strength. Although some studies have simply mixed the two, they have not fundamentally solved the synergistic contradiction between cementing activity activation, strength development and environmental protection safety, and often still rely on a large amount of cement or high-alkali activator, failing to achieve efficient and high-value utilization of solid waste.

[0004] Therefore, it is of great significance to develop a filling material that can fully utilize the characteristics of red mud and desulfurization gypsum, achieve in-situ mutual modification through component compatibility, and has excellent workability, mechanical properties and environmental protection, for promoting the large-scale disposal of industrial solid waste and green mine construction. SUMMARY

[0005] To solve the above technical problems, the present application aims to provide a nano-composite filling material based on in-situ acid-base mutual modification enhancement, which is a method for preparing a high-performance and environmentally friendly filling material by utilizing the acid-base mutual modification effect of red mud and desulfurization gypsum, and synergistically using cement and nano-silicon aluminum materials. The method specifically involves neutralizing the alkalinity of red mud and the acidity of desulfurization gypsum through precise component ratio design, and activating synergistic cementing reaction, to prepare a filling material with high fluidity, high strength and environmental safety under the regulation of nano-materials.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solution: A nano-composite filling material based on in-situ acid-base mutual modification enhancement, wherein the nano-composite filling material is prepared by mixing mixture A and water in a mass ratio of (62-68) : (32-38). The mixture A is obtained by mixing red mud, desulfurized gypsum, cement and nano-silicon aluminum materials.

[0007] Preferably, the raw materials in mixture A are composed of the following mass fractions: Red mud 68-72%, desulfurized gypsum 23-27%, cement 4.8-8%, and nano-silicon-aluminum materials 0.1-0.3%.

[0008] Preferably, the cement is ordinary silicate cement or sulfoaluminate cement with a strength grade of 42.5.

[0009] Preferably, the nano-silicon-aluminum material is a mixture of nano-silica and nano-alumina obtained by compounding them in a mass ratio of (1~3):1; The specific surface area of ​​the nano-silicon-aluminum material is not less than 200 m². 2 / g.

[0010] A method for preparing a nanocomposite filling material based on in-situ acid-base intermodulation enhancement includes the following steps: S1. Preparation of mixture A: Red mud, desulfurized gypsum, cement, and nano-silicon aluminum materials are selected according to their respective mass fractions and placed in a mixer until they are mixed evenly; S2. Place mixture A in a forced mixer, add water and stir until a uniform, particle-free slurry is obtained.

[0011] Preferably, in step S1, the mixing time in the mixer is 10 to 5 minutes.

[0012] Preferably, in step S2, the stirring time with water is 3-5 minutes.

[0013] A construction method for a nanocomposite backfill material based on in-situ acid-base intermodulation enhancement includes transporting the nanocomposite backfill material obtained by the preparation method to the backfilling goaf or the area to be backfilled through a pumping system, without compaction, relying on its own weight to flow and form.

[0014] An application of a nanocomposite filling material based on in-situ acid-base intermodulation enhancement, wherein the nanocomposite filling material is used in filling goaf areas in mines, backfilling roadbeds, or grouting in engineering projects.

[0015] Compared with the prior art, the present invention has at least the following technical effects: This invention provides a nanocomposite filling material based on in-situ enhanced acid-base intermodulation. This material utilizes the acid-base intermodulation effect of red mud and desulfurized gypsum, synergistically combining cement and nano-silica-alumina materials to prepare a high-performance, environmentally friendly filling material. Specifically, this method involves precisely designing the component ratios, using the alkalinity of red mud to neutralize the acidity of desulfurized gypsum, and activating a synergistic gelation reaction. Under the control of nanomaterials, a high-flowability, high-strength, and environmentally safe filling material is prepared.

[0016] The innovative mechanism in this method is: (1) Acid-base intermodulation and alkali hazard removal: The acid-base neutralization reaction between red mud (strongly alkaline) and desulfurized gypsum (weakly acidic) is creatively utilized to effectively reduce the total alkalinity of the system and stabilize the pH value of the final product within the weakly alkaline range of 7-9. This fundamentally eliminates the environmental risks and application obstacles (such as equipment corrosion and hydration inhibition) caused by the high alkalinity of red mud. This "intermodulation" process is the key to achieving the environmental protection of materials.

[0017] (2) Synergistic cementation and strength enhancement: This invention reveals the core enhancement mechanism: During the neutralization process of the system, the aluminosilicate active components dissolved in the red mud and the sulfate ions (SO4) provided by the desulfurized gypsum... 2- ) and calcium ions (Ca) provided by cement hydration 2+ The reaction produces a large number of needle-like or columnar ettringite (AFt) crystals. This hydration product network, together with the geopolymer gel, forms an interpenetrating reinforced composite cementitious system, providing significant early and late strength support, enabling the material to achieve a compressive strength exceeding 2.0 MPa at 7 days.

[0018] (3) Nanomaterials regulate rheology and microstructure: Nano-silica aluminum materials, as nucleation centers and structure regulators, greatly promote the uniform nucleation and growth of ettringite and gel phase, and optimize the microstructure. On the other hand, they effectively improve the rheological properties of the slurry at low dosage, so that even with a solid content of more than 65%, it still exhibits the characteristics of low viscosity and high fluidity of Newtonian fluid, with a diffusivity greater than 250 mm, making it very easy to pump and fill.

[0019] (4) Highly efficient solidification of heavy metal ions: The three-dimensional network structure of ettringite crystals and geopolymers generated by the reaction has a strong physical encapsulation and chemical bonding solidification ability for fluoride ions and heavy metal ions (such as Pb, Cr, Cd, etc.) in red mud, so that the concentration of fluoride ions in the leachate is less than 5 mg / L, and the leaching concentration of various heavy metal ions meets the requirements of the GB 5085.3-2007 standard, and the environmental safety is extremely high.

[0020] (5) High utilization rate of solid waste and simple process: Red mud and desulfurized gypsum account for more than 95% of the total solid phase mass, realizing the high-value utilization of bulk solid waste. The entire preparation process is carried out at room temperature and pressure, without the need for pre-activation treatment of raw materials, with extremely low energy consumption, simple process and obvious cost advantage.

[0021] This method enables the efficient resource utilization of red mud and desulfurized gypsum. The process is simple and low-cost, and is particularly suitable for mine filling and engineering backfilling. Detailed Implementation

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly described below in conjunction with the description of the embodiments or the prior art. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0023] Example 1: Preparation of materials for filling goaf areas in mines.

[0024] A method for preparing nanocomposite filling materials based on in-situ acid-base intermodulation enhancement. S1, Raw material ratio (mass percentage) of mixture A: Red mud: 70% Desulfurized gypsum: 25% PO 42.5 cement: 4.8% Nano-SiO2-Al2O3 composite powder (specific surface area 220 m²) 2 / g, SiO2: Al2O3=2:1): 0.2% S2. Take 65 kg of mixture A and 35 kg of water and add them to a forced mixer. Mix for 4 minutes to obtain a uniform slurry.

[0025] Performance testing: The slurry spread reached 265 mm, indicating excellent rheological properties. After curing at room temperature for 7 days, the unconfined compressive strength of the cast specimen was measured to be 2.4 MPa. The pH of the leachate was 8.1, the fluoride ion leaching concentration was 3.8 mg / L, and the leaching concentrations of heavy metal ions were undetectable, meeting national standards.

[0026] Example 2: Preparation of materials for roadbed backfilling.

[0027] A method for preparing nanocomposite filling materials based on in-situ acid-base intermodulation enhancement. S1, Raw material ratio (mass percentage) of mixture A: Red mud: 68% Desulfurized gypsum: 27% PO 42.5 cement: 4.9% Nano-SiO2-Al2O3 composite powder (specific surface area 250 m²) 2 / g, SiO2: Al2O3=1.5:1): 0.1% S2. Take 68 kg of mixture A and 32 kg of water and add them to a forced mixer. Mix for 5 minutes to obtain a uniform slurry.

[0028] Performance testing: Slurry diffusion greater than 250 mm. 7-day compressive strength 2.1 MPa. Leachate pH 7.8, fluoride ion leaching concentration 4.5 mg / L, environmental protection standards met.

[0029] Comparative example: Without the addition of desulfurized gypsum and nanomaterials: 94.8% red mud, 5% cement, 0.2% nanomaterials, water-to-solid ratio 0.35. The mixed slurry is viscous with a diffusion range of only 180 mm, slow setting, a 7-day strength of 0.8 MPa, a leachate pH of 11.5, and a fluoride ion leaching concentration of 15 mg / L, failing to meet environmental protection standards.

[0030] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nanocomposite filling material based on in-situ acid-base intermodulation enhancement, characterized in that, The nanocomposite filling material is prepared by mixing mixture A and water in a mass ratio of (62~68):(32~38); The mixture A is obtained by mixing red mud, desulfurized gypsum, cement and nano-silicon aluminum materials.

2. The nanocomposite filling material based on in-situ acid-base intermodulation enhancement according to claim 1, characterized in that, The raw materials in mixture A are composed of the following mass fractions. composition: Red mud 68-72%, desulfurized gypsum 23-27%, cement 4.8-8%, and nano-silicon-aluminum materials 0.1-0.3%.

3. The nanocomposite filling material based on in-situ acid-base intermodulation enhancement according to claim 2, characterized in that, The cement is ordinary Portland cement or sulfoaluminate cement with a strength grade of 42.

5.

4. The nanocomposite filling material based on in-situ acid-base intermodulation enhancement according to claim 2, characterized in that, The nano-silicon-aluminum material is a mixture of nano-silica and nano-alumina in a mass ratio of (1~3):

1. The specific surface area of ​​the nano-silicon-aluminum material is not less than 200 m². 2 / g.

5. A method for preparing a nanocomposite filling material based on in-situ acid-base intermodulation enhancement as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Preparation of mixture A: Red mud, desulfurized gypsum, cement, and nano-silicon aluminum materials are selected according to their respective mass fractions and placed in a mixer until they are mixed evenly; S2. Place mixture A in a forced mixer, add water and stir until a uniform, particle-free slurry is obtained.

6. The preparation method of a nanocomposite filling material based on in-situ acid-base intermodulation enhancement according to claim 5, characterized in that, In step S1, the mixing time in the mixer is 10-5 minutes.

7. The preparation method of a nanocomposite filling material based on in-situ acid-base intermodulation enhancement according to claim 5, characterized in that, In step S2, the water is added and stirred for 3-5 minutes.

8. A construction method for a nanocomposite filling material based on in-situ acid-base intermodulation enhancement as described in any one of claims 1 to 4, characterized in that, This includes transporting nanocomposite filling materials obtained through preparation methods to filling mined-out areas or areas to be backfilled through a pumping system, without the need for compaction, relying on gravity flow to form the material.

9. An application of a nanocomposite filling material based on in-situ acid-base intermodulation enhancement as described in any one of claims 1 to 4, characterized in that, The nanocomposite filling material is used in filling goaf areas in mines, backfilling roadbeds, or grouting in engineering projects.