Self-repairing multi-matrix plugging material and preparation method thereof

Abstract

According to the self-repairing type multi-matrix plugging material and the preparation method thereof, main matrix materials comprise modified yellow mud, fly ash, an alkali active agent and a microbial self-repairing exciting agent, bentonite is added to modify the yellow mud, self-repairing is achieved through the oxygen-sensitive microencapsulated microbial self-repairing exciting agent, and then long-acting plugging is achieved. The preparation process comprises the following steps: firstly, preparing the microbial self-repairing exciting agent, dissolving and mixing polylactic acid and nitrogen-doped activated carbon, drying, crushing, soaking in a microbial bacterial solution to prepare a microbial skeleton composite capsule core, and uniformly wrapping with an oxygen-sensitive wall material to prepare the microbial self-repairing exciting agent; and finally, dissolving an alkali active agent in water, mixing the alkali active agent with the prepared microbial self-repairing exciting agent, the modified yellow mud and the fly ash according to a certain proportion, and uniformly stirring to obtain the self-repairing multi-matrix plugging material. The prepared self-repairing type multi-matrix plugging material is low in cost and environmentally friendly, has self-repairing performance and high resistance strength, and achieves the purpose of long-acting plugging.

Description

Technical Field

[0001] This invention belongs to the field of mine pile sealing and fire prevention technology, specifically relating to a self-healing multi-matrix sealing material and its preparation method. Background Technology

[0002] Mine stockpiles are accumulations of waste materials formed during mining operations, typically including coal gangue and slag. Due to the difficulty in processing and low utilization rates, these stockpiles continue to accumulate and expand, leading to a series of environmental problems such as heavy metal pollution and acidic mine water seepage. These waste materials, piled in open areas or inside mining areas, are prone to spontaneous combustion due to factors such as high external temperatures, oxygen supply, and chemical reactions. Once a fire occurs, it is extremely difficult to extinguish and will produce large amounts of toxic and harmful gases, impacting the surrounding ecosystem and the health of residents. Furthermore, the high temperatures and smoke generated by the fire can cause structural instability in the mine stockpiles, triggering geological disasters such as collapses and landslides, endangering the safety of the mining area.

[0003] Currently, domestic and international scholars mainly use methods such as grouting, colloids, foam, and surface covering to seal and extinguish fires in mine shafts. Organic sealing materials cause significant pollution. Commonly used inorganic sealing materials, such as yellow mud, are inexpensive and have good plasticity and sealing properties, but they are prone to cracking after water loss, easily causing secondary air leakage, and have low strength. Fly ash has strong high-temperature resistance and corrosion resistance, and high strength after consolidation, but its water resistance and hardening time are long. In recent years, new mine sealing materials have been extensively studied. For example, patent CN115819050A discloses a flexible solid waste-based lightweight expansive cementitious material for mine leakage sealing. Using solid waste as raw material, it can effectively block air leakage and further bind and reinforce loose coal, with good accumulation effect. However, none of these methods can achieve long-term sealing of mine shafts. Once cracks or damage occur, refilling is required. Geopolymer gels are resistant to high temperatures, acid and alkali corrosion, and have high early strength. Microbial mineralization technology, through the metabolic activities of microorganisms and their interaction with the environment, forms minerals that can repair fractures. However, ensuring the activity and targeted release of microorganisms remains a challenge, and research on sealing materials combining these two technologies has not yet been widely conducted. In conclusion, developing a highly efficient and environmentally friendly sealing material with sufficient strength and self-healing capabilities is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a self-healing multi-matrix sealing material and its preparation method. The method is simple, environmentally friendly, and low in cost. The self-healing multi-matrix sealing material prepared has strong corrosion resistance and wind erosion resistance. It can also self-repair when cracks appear in the sealing layer by using an oxygen-sensitive microencapsulated microbial self-healing activator, thereby achieving the goal of long-term sealing of the mine body.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A method for preparing a self-healing multi-matrix sealing material includes the following steps:

[0007] S1. Preparation of microbial self-repair activators;

[0008] S1-1. Dissolve polylactic acid in dichloromethane to prepare a polylactic acid solution with a mass fraction of 5% to 10%. Then slowly add nitrogen-doped activated carbon to the polylactic acid solution, stir thoroughly, and let it stand at room temperature until the solvent evaporates and the skeleton is formed. Rinse with deionized water to remove residual dichloromethane, and then put it in a vacuum drying oven to dry at 40 to 50°C for 5 to 7 hours. Crush and grind to 10 to 20 mesh to obtain the microbial skeleton.

[0009] S1-2. The microbial skeleton obtained in step S1-1 is immersed in microbial inoculum for 25-35 minutes and then allowed to stand and dry to obtain the microbial skeleton composite capsule core.

[0010] S1-3. Flaxseed oil, hydrophobic silica nanoparticles and nano manganese dioxide are mixed and dispersed in an ethanol-water mixed solvent, and ultrasonically homogenized to form a uniform dispersion of oxygen-sensitive wall material.

[0011] S1-4. Under an inert atmosphere, place the microbial skeleton composite capsule core prepared in S1-2 in a fluidized bed. Spray the oxygen-sensitive wall material uniform dispersion obtained in step S1-3 evenly onto the surface of the microbial skeleton composite capsule core using an electrostatic spraying device. Then place it in a vacuum drying oven and perform staged pressure reduction drying at 35-40℃ for 40-60 minutes to obtain the microbial self-repair activator, and store it in a sealed container.

[0012] S2. Add 5% to 10% bentonite by mass to yellow clay and stir evenly to obtain modified yellow clay;

[0013] S3. Dissolve the alkaline activator in water, and then mix it with the microbial self-healing activator prepared in step S1, the modified yellow mud prepared in step S2, and fly ash in a certain proportion. Stir evenly to obtain a self-healing multi-matrix sealing material.

[0014] Preferably, in step S3, the water-to-solid ratio of the self-healing multi-matrix sealing material is 0.25 to 0.45, that is, the mass ratio of water to solid matter in the self-healing multi-matrix sealing material is (0.25 to 0.45): 1.

[0015] Preferably, in step S3, the mass ratio of the alkali activator to the total mass of the modified yellow mud and fly ash is 1:(10-12.5), and the mass ratio of the microbial self-healing activator to the total mass of the modified yellow mud and fly ash is 1:(10-40).

[0016] Preferably, in step S3, the mass ratio of modified yellow mud to fly ash is (1.5~2.5):1.

[0017] Preferably, in step S1-1, the mass ratio of polylactic acid to nitrogen-doped activated carbon is (2-4):1.

[0018] Preferably, in steps S1-2, the microbial culture solution is a mixed-strain culture solution, and the strains include at least two of Bacillus megaterium, Bacillus subtilis, Bacillus pseudostrongylus, Bacillus pseudofungiformis, and Bacillus licheniformis; the concentration of the microbial culture solution is 1×10⁻⁶. 7 ~1×10 9 CFU / mL.

[0019] Preferably, in steps S1-3, the mass ratio of flaxseed oil, hydrophobic silica nanoparticles, and nano-manganese dioxide is 60:5:1; the ultrasonic homogenization treatment lasts for 5-10 minutes, and the ethanol concentration in the ethanol-water mixed solvent is 80%.

[0020] Preferably, in steps S1-4, the voltage of the electrostatic spraying equipment is 10-15kV, the spraying thickness is 20-30μm, and the spraying rate is 0.5-1mL / min; the specific process of staged pressure reduction drying is as follows: the vacuum degree is maintained at 100mbar for the first 10-15min, and the vacuum degree is reduced to 30mbar for the next 30-45min.

[0021] Preferably, in step S3, the alkaline activator is at least one of potassium hydroxide, sodium hydroxide, sodium carbonate, sodium silicate, potassium silicate, and potassium carbonate.

[0022] To achieve the above-mentioned objectives, the present invention also provides a self-healing multi-matrix sealing material prepared by the above-mentioned preparation method.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) This invention improves the water retention and mineral content of the prepared sealing material by using modified yellow mud, making it more suitable for the survival and reproduction of microorganisms. It also adds fly ash, alkali activator and other substances to generate a geopolymer gel, which solves the problem of low strength of the original sealing material. The material can have good mechanical strength in the early stage of filling, which further increases the resistance strength and molding speed of the material.

[0025] (2) This invention achieves self-repair function through oxygen-sensitive microencapsulated microbial self-repair activator. When cracks are generated on the surface of the sealing material due to dryness or external damage, external oxygen will enter the cracks. The oxygen-sensitive microcapsule wall will rupture upon contact with oxygen, releasing the internal microorganisms. Based on the microbial mineralization mechanism, the microorganisms will form mineral deposits through their own metabolic activities and interaction with the surrounding high water retention and mineral-rich environment, thus repairing the cracks themselves and achieving the goal of long-term sealing.

[0026] (3) This invention solves the problem of maintaining microbial activity by combining microcapsule technology and microbial skeleton structure, effectively improving the survival rate of microorganisms and the self-healing performance of materials; the microbial skeleton structure in this invention has carbon and nitrogen sources required for microbial survival and provides good physical support and protection for microbial survival; the microcapsule structure provides a protective environment for microorganisms, enhances their tolerance, and ensures that the repair agent can be triggered in time when cracks occur in the material and that microorganisms can grow at specific points, further improving the compressive strength of the sealing material;

[0027] (4) The materials used in this invention are green and environmentally friendly, have low cost, and are simple to prepare and use. They also have strong corrosion resistance, wind erosion resistance and stability. With appropriate material ratio, they can achieve good applicability to mine stockpiles and can effectively prevent mine stockpiles fire accidents. Attached Figure Description

[0028] Figure 1 This is a comparison chart showing the changes in pressure readings over time for Examples 1, 2, 3, 4, and Comparative Example 2 at room temperature for a period of 0-6 hours.

[0029] Figure 2 This is a comparison chart of the leakage plugging rate changes over time in Example 3 and Comparative Example 2 at room temperature, collected over a period of 0-6 hours.

[0030] Figure 3 This is a flowchart illustrating the preparation principle of the present invention. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] like Figure 3 As shown, a method for preparing a self-healing multi-matrix sealing material includes the following steps:

[0034] S1. Preparation of microbial self-repair activators;

[0035] S1-1. Dissolve 187.5g of polylactic acid in dichloromethane to prepare a 5% polylactic acid solution. Then slowly add 62.5g of nitrogen-doped activated carbon to the polylactic acid solution, stir thoroughly, and let stand at room temperature until the solvent evaporates and the skeleton is formed. Rinse with deionized water to remove residual dichloromethane, and then put it in a vacuum drying oven to dry at 40-50℃ for 5-7 hours. Crush and grind to 10-20 mesh to obtain the microbial skeleton.

[0036] S1-2. The microbial skeleton obtained in step S1-1 is immersed in a microbial culture of Bacillus megaterium and Bacillus subtilis for 30 minutes, and then allowed to stand and dry to obtain a microbial skeleton composite capsule core; the concentration of the microbial culture is 1×10⁻⁶. 8 CFU / mL;

[0037] S1-3. Flaxseed oil, hydrophobic silica nanoparticles and nano manganese dioxide are mixed in a mass ratio of 60:5:1 and dispersed in an ethanol-water mixed solvent. The mixture is then ultrasonically homogenized for about 8 minutes to form a uniform dispersion of oxygen-sensitive wall material. The ethanol concentration in the ethanol-water mixed solvent is 80%.

[0038] S1-4. Under an inert atmosphere, the microbial skeleton composite capsule core obtained in step S1-2 is placed in a fluidized bed. The oxygen-sensitive wall material uniform dispersion obtained in step S1-3 is uniformly sprayed onto the surface of the microbial skeleton composite capsule core obtained in step S1-2 through an electrostatic spraying device (voltage 10-15kV), with a thickness of 20-30μm and a spraying rate of 0.8mL / min. Then, it is placed in a vacuum drying oven and subjected to staged pressure reduction drying at 35℃. The vacuum degree is maintained at 100mbar for the first 10min, and then reduced to 30mbar for the next 30min. The total drying time is 40min, and the microbial self-repair activator is obtained and sealed for storage.

[0039] S2. After adding 5% bentonite by mass to the yellow clay, mix it evenly with a mixer to obtain 7 kg of modified yellow clay.

[0040] S3. Dissolve 250g of potassium hydroxide and 750g of sodium carbonate in 4.5kg of water, then mix with 0.25kg of microbial self-healing activator prepared in step S1, 7kg of modified yellow mud prepared in step S2, and 3kg of fly ash. Stir evenly to obtain a self-healing multi-matrix sealing material with a microbial self-healing agent incorporation amount (the mass ratio between the mass of the microbial self-healing activator and the total mass of the modified yellow mud and fly ash) of 2.5% and a water-solid ratio of 0.40.

[0041] Example 2

[0042] like Figure 3 As shown, a method for preparing a self-healing multi-matrix sealing material includes the following steps:

[0043] S1. Preparation of microbial self-repair activators;

[0044] S1-1. Dissolve 375g of polylactic acid in dichloromethane to prepare a 5% polylactic acid solution. Then slowly add 125g of nitrogen-doped activated carbon to the polylactic acid solution. After stirring thoroughly, let it stand at room temperature until the solvent evaporates and the skeleton is formed. Rinse with deionized water to remove residual dichloromethane. Then place it in a vacuum drying oven and dry at 40-50℃ for about 5-7 hours. Crush and grind to 10-20 mesh to obtain the microbial skeleton.

[0045] Steps S1-2 to S1-4 and step S2 are consistent with those in Example 1;

[0046] S3. Dissolve 250g of potassium hydroxide and 750g of sodium carbonate in 4.6kg of water, then mix with 0.5kg of microbial self-healing activator obtained in step S1, 7kg of modified yellow mud obtained in step S2, and 3kg of fly ash. Stir evenly to obtain a self-healing multi-matrix sealing material with a microbial self-healing agent incorporation amount (the mass ratio between the mass of the microbial self-healing activator and the total mass of the modified yellow mud and fly ash) of 5% and a water-solid ratio of 0.40.

[0047] Example 3

[0048] like Figure 3 As shown, a method for preparing a self-healing multi-matrix sealing material includes the following steps:

[0049] S1. Preparation of microbial self-repair activators;

[0050] S1-1. Dissolve 562.5g of polylactic acid in dichloromethane to prepare a 5% polylactic acid solution. Then slowly add 187.5g of nitrogen-doped activated carbon to the polylactic acid solution. After stirring thoroughly, let it stand at room temperature until the solvent evaporates and the skeleton is formed. Rinse with deionized water to remove residual dichloromethane. Then place it in a vacuum drying oven and dry at 40-50℃ for about 5-7 hours. Crush and grind to 10-20 mesh to obtain the microbial skeleton.

[0051] Steps S1-2 to S1-4 and step S2 are consistent with those in Example 1;

[0052] S3. Dissolve 250g of potassium hydroxide and 750g of sodium carbonate in 4.7kg of water, then mix with 0.75kg of microbial self-healing activator obtained in step S1, 7kg of modified yellow mud obtained in step S2, and 3kg of fly ash. Stir evenly to obtain a self-healing multi-matrix sealing material with a microbial self-healing agent incorporation amount (the mass ratio between the mass of the microbial self-healing activator and the total mass of the modified yellow mud and fly ash) of 7.5% and a water-solid ratio of 0.40.

[0053] Example 4

[0054] like Figure 3 As shown, a method for preparing a self-healing multi-matrix sealing material includes the following steps:

[0055] S1. Preparation of microbial self-repair activators;

[0056] S1-1. Dissolve 750g of polylactic acid in dichloromethane to prepare a 5% polylactic acid solution. Then slowly add 250g of nitrogen-doped activated carbon to the polylactic acid solution. After stirring thoroughly, let it stand at room temperature until the solvent evaporates and the skeleton is formed. Rinse with deionized water to remove residual dichloromethane. Then place it in a vacuum drying oven and dry at 40-50℃ for about 5-7 hours. Crush and grind to 10-20 mesh to obtain the microbial skeleton.

[0057] Steps S1-2 to S1-4 and step S2 are consistent with those in Example 1;

[0058] S3. Dissolve 250g of potassium hydroxide and 750g of sodium carbonate in 4.8kg of water, then mix with 1kg of microbial self-healing activator prepared in step S1, 7kg of modified yellow mud prepared in step S2, and 3kg of fly ash. Stir evenly to obtain a self-healing multi-matrix sealing material with a microbial self-healing agent incorporation amount (the mass ratio between the mass of the microbial self-healing activator and the total mass of the modified yellow mud and fly ash) of 10% and a water-solid ratio of 0.40.

[0059] Examples 5-9

[0060] In Examples 5-9, only step S1-2 differs from that in Example 3. Step S1-2 in Examples 5-9 is as follows: the microbial skeleton obtained in step S1-1 is immersed in the microbial inoculum of a single species of Bacillus megaterium (Example 5), Bacillus subtilis (Example 6), Bacillus pseudostrongylus (Example 7), Bacillus pseudofungiformis (Example 8), and Bacillus licheniformis (Example 9) for 30 minutes, and then allowed to stand and dry for later use. All other steps are consistent with those in Example 3.

[0061] Example 10

[0062] In this embodiment, only step S3 differs from that in Example 3. In step S3 of this embodiment, 250g of potassium hydroxide and 750g of sodium carbonate are dissolved in approximately 3kg of water, then mixed with 0.75kg of the microbial self-healing activator obtained in step S1, 7kg of modified yellow mud prepared in step S2, and 3kg of fly ash. The mixture is stirred until homogeneous, resulting in a self-healing multi-matrix sealing material with a microbial remediation agent incorporation ratio (the mass ratio between the mass of the microbial self-healing activator and the total mass of the modified yellow mud and fly ash) of 7.5% and a water-to-solid ratio of approximately 0.25. All other steps remain the same as in Example 3. (The calculated water volume is slightly increased from 2.9375kg to 3kg.)

[0063] Example 11

[0064] In this embodiment, only step S3 differs from that in Example 3. In step S3 of this embodiment, 250g of potassium hydroxide and 750g of sodium carbonate are dissolved in approximately 5.2kg of water, and then mixed with 0.75kg of microbial self-healing activator obtained in step S1, 7kg of modified yellow mud prepared in step S2, and 3kg of fly ash. The mixture is stirred evenly to obtain a self-healing multi-matrix sealing material with a microbial remediation agent incorporation amount (the mass ratio between the mass of the microbial self-healing activator and the total mass of the modified yellow mud and fly ash) of 7.5% and a water-to-solid ratio of approximately 0.45. All other steps are consistent with those in Example 3. (The calculated water volume is slightly reduced from 5.2875kg to 5.2kg.) Comparative Example 1

[0065] Without adding a microbial self-healing activator, 250g of potassium hydroxide and 750g of sodium carbonate were dissolved in 4.4kg of water and mixed. Then, the mixture was mixed with 7kg of modified yellow mud and 3kg of fly ash. After stirring evenly, a sealing material with a water-to-solid ratio of 0.40 was obtained, which is Comparative Example 1.

[0066] Comparative Example 2

[0067] Without adding microbial self-healing activators and alkaline activators, 7 kg of modified yellow mud was mixed with 3 kg of fly ash and 4 kg of water. After stirring evenly, a sealing material with a water-to-solid ratio of 0.40 was obtained as Comparative Example 2.

[0068] The sealing materials prepared in Examples 1-11 and Comparative Examples 1-2 were poured into 50mm*50mm*50mm cube molds to prepare several sets of samples. The setting time of the samples was tested using a Vicat apparatus; the compressive strength was tested by uniformly loading the samples at a rate of 0.5mm / min until the samples were damaged using a uniaxial rock compressor and taking the average value; a crack with a length of 3cm and a depth of 5mm was made on the surface of the sample using a knife, and the crack images were processed daily using computer image color block recognition technology. The ratio of the crack repair length to the total crack length was taken as the crack repair rate, and the number of days required for the repair rate to be greater than 85% was recorded as the repair time.

[0069] The properties of self-healing multi-matrix plugging materials with different amounts of microbial self-healing activator were tested by comparing Examples 1, 2, 3, 4, Comparative Example 1, and Comparative Example 2. The experimental results are shown in Table 1.

[0070] Table 1. Comparison of properties of self-healing multi-matrix sealing materials with different amounts of microbial self-healing activators incorporated.

[0071]

[0072] As shown in Table 1, Comparative Example 2 had the longest setting time. Comparative Example 1, under the action of the alkali activator, produced a geopolymer gel, accelerating the hydration reaction of the minerals and promoting the setting and hardening of the material. With the increase of the amount of microbial self-healing activator added, the setting time decreased slightly. This is because the microbial self-healing activator absorbs moisture from the self-healing multi-matrix sealing material, and some of the self-healing activator on the material surface breaks upon contact with oxygen, generating a microbial mineralization reaction that also accelerates the setting speed. Regarding compressive strength, it gradually increased with curing time. The compressive strength of Comparative Example 1 was much greater than that of Comparative Example 2. The alkali activator promoted the formation of geopolymer gels from minerals such as fly ash, improving the material's density and effectively enhancing its compressive strength. Although the addition of the microbial self-healing activator slightly reduced the compressive strength, the value was still much higher than that of Comparative Example 2. With the increase of the amount of microbial self-healing activator added, the crack repair time gradually shortened, indicating that this invention has a good repair effect on sealing cracks in mine bodies.

[0073] A simulated mine shaft plugging test device was used to test the plugging performance of a self-healing multi-matrix plugging material. The test device consisted of a plugging material injection control system, an inert gas injection control system, a steel pipe container, a pressure gauge, a data acquisition system, and a camera. The steel pipe was 1m high and 0.5m in diameter at the bottom. 10kg of coal gangue was added first. In two separate experiments, 5kg of the plugging material from Example 3 and Comparative Example 2 were injected onto the surface of the coal gangue, respectively. After the material was allowed to solidify, inert gas was slowly and uniformly injected through a pre-embedded pipe embedded in the coal gangue until the pressure gauge reading reached 2MPa (initial pressure P1). Timing began, and the pressure gauge reading P2 was collected every 0.5 hours. Under room temperature conditions, the maximum collection time was 6 hours. The plugging rate versus time curves for Example 3 and Comparative Example 2 were plotted. The formula for calculating the plugging rate is shown below.

[0074]

[0075] In the formula: η is the plugging rate, %; P2 is the pressure reading, MPa; P1 is the initial pressure, which is 2MPa.

[0076] Figure 1 This is a comparison graph showing the change of pressure readings over time for Examples 1-4 and Comparative Example 2. Figure 2 This is a comparison graph showing the change in plugging rate over time between Example 3 and Comparative Example 2. From... Figure 1 , 2 It can be seen that with an initial pressure of 2 MPa, the pressure gauge reading gradually decreased over time, and the plugging rate also gradually decreased, with the rate of decrease gradually narrowing. After 6 hours, the plugging rate of Example 1 was approximately 76.7%, Example 2 was approximately 83.5%, Example 3 was approximately 87.1%, Example 4 was approximately 87.6%, and Comparative Example 2 was approximately 66.5%. The value of Comparative Example 2 still showed a decreasing trend after 6 hours. After 24 hours of measurement, the pressure gauge reading of Comparative Example 2 was 1.246 MPa, with a plugging rate of approximately 62.3%, and the pressure gauge reading of Example 3 was 1.728 MPa, with a plugging rate of approximately 86.4%. The microbial self-healing activator self-repaired the existing cracks, with a plugging rate far exceeding that of Comparative Example 2.

[0077] The effects of different bacterial species and quantities on the repair speed of the self-healing multi-matrix sealing material were tested by comparing Examples 3 and 5-9. The experimental results are as follows: the repair time, ranked from shortest to longest, is: Example 3 (Bacillus megaterium and Bacillus subtilis) < Example 5 (Bacillus subtilis) < Example 6 (Bacillus megaterium) < Example 7 (Bacillus licheniformis) < Example 8 (Bacillus pseudofungiformis) < Example 9 (Bacillus pseudostrongylus). It can be concluded that the repair rate of the combination of two bacterial species is greater than that of a single bacterial species.

[0078] The effects of different water-to-solid ratios on the setting time and compressive strength of the self-healing multi-matrix sealing material were tested by comparing Examples 3, 10, and 11. The experimental results are as follows: setting time, from shortest to longest, is: Example 10 < Example 3 < Example 11; 14-day compressive strength, from shortest to longest, is: Example 11 < Example 3 < Example 10. A higher water-to-solid ratio increases the fluidity of the self-healing multi-matrix sealing material, facilitating the filling of voids or cracks. However, it increases the setting time, decreases the compressive strength, and reduces the material's durability, but it is still superior to Comparative Examples 1 and 2.

[0079] Therefore, it can be seen that the self-healing multi-matrix sealing material of the present invention has excellent leakage sealing effect.

[0080] The self-healing multi-matrix sealing material prepared by this invention exhibits strong resistance and excellent plugging effect. Through the self-repair of cracks in the sealing layer using an oxygen-sensitive microencapsulated microbial self-healing activator, it achieves the goal of long-term sealing of mine stockpiles and effectively prevents mine stockpile fires. Furthermore, the preparation method of this invention is simple, environmentally friendly, and low-cost, and has broad application prospects.

Claims

1. A method for preparing a self-healing multi-matrix sealing material, characterized in that, Includes the following steps: S1. Preparation of microbial self-repair activators; S1-1. Dissolve polylactic acid in dichloromethane to prepare a polylactic acid solution with a mass fraction of 5% to 10%. Then slowly add nitrogen-doped activated carbon to the polylactic acid solution, stir thoroughly, and let it stand at room temperature until the solvent evaporates and the skeleton is formed. Rinse with deionized water to remove residual dichloromethane, and then put it in a vacuum drying oven to dry at 40 to 50°C for 5 to 7 hours. Crush and grind to 10 to 20 mesh to obtain the microbial skeleton. S1-2. The microbial skeleton obtained in step S1-1 is immersed in microbial inoculum for 25-35 minutes and then allowed to stand and dry to obtain the microbial skeleton composite capsule core. S1-3. Flaxseed oil, hydrophobic silica nanoparticles and nano manganese dioxide are mixed and dispersed in an ethanol-water mixed solvent, and ultrasonically homogenized to form a uniform dispersion of oxygen-sensitive wall material. S1-4. Under an inert atmosphere, place the microbial skeleton composite capsule core prepared in S1-2 in a fluidized bed. Spray the oxygen-sensitive wall material uniform dispersion obtained in step S1-3 evenly onto the surface of the microbial skeleton composite capsule core using an electrostatic spraying device. Then place it in a vacuum drying oven and perform staged pressure reduction drying at 35-40℃ for 40-60 minutes to obtain the microbial self-repair activator, and store it in a sealed container. S2. Add 5% to 10% bentonite by mass to yellow clay and stir evenly to obtain modified yellow clay; S3. Dissolve the alkaline activator in water, and then mix it with the microbial self-healing activator prepared in step S1, the modified yellow mud prepared in step S2, and fly ash in a certain proportion. Stir evenly to obtain a self-healing multi-matrix sealing material.

2. The preparation method of a self-healing multi-matrix sealing material according to claim 1, characterized in that, In step S3, the water-to-solid ratio of the self-healing multi-matrix sealing material is 0.25 to 0.45, that is, the mass ratio of water to solid matter in the self-healing multi-matrix sealing material is (0.25 to 0.45):

1.

3. The method for preparing a self-healing multi-matrix sealing material according to claim 1 or 2, characterized in that, In step S3, the mass ratio between the alkali activator and the total mass of modified yellow mud and fly ash is 1:(10-12.5), and the mass ratio between the microbial self-repair activator and the total mass of modified yellow mud and fly ash is 1:(10-40).

4. A method for preparing a self-healing multi-matrix sealing material according to claim 1 or 2, characterized in that, In step S3, the mass ratio between modified yellow mud and fly ash is (1.5~2.5):

1.

5. A method for preparing a self-healing multi-matrix sealing material according to claim 1 or 2, characterized in that, In step S1-1, the mass ratio of polylactic acid to nitrogen-doped activated carbon is (2-4):

1.

6. A method for preparing a self-healing multi-matrix sealing material according to claim 1 or 2, characterized in that, In steps S1-2, the microbial culture solution is a mixed-strain culture solution, and the mixed strains are at least two of Bacillus megaterium, Bacillus subtilis, Bacillus pseudostrongylus, Bacillus pseudofungiformis, and Bacillus licheniformis; the concentration of the microbial culture solution is 1×10⁻⁶. 7 ~1×10 9 CFU / mL.

7. A method for preparing a self-healing multi-matrix sealing material according to claim 1 or 2, characterized in that, In steps S1-3, the mass ratio of flaxseed oil, hydrophobic silica nanoparticles, and nano-manganese dioxide is 60:5:1; ultrasonic homogenization is performed for 5-10 minutes, and the ethanol concentration in the ethanol-water mixed solvent is 80%.

8. A method for preparing a self-healing multi-matrix sealing material according to claim 1 or 2, characterized in that, In steps S1-4, the voltage of the electrostatic spraying equipment is 10-15kV, the spraying thickness is 20-30μm, and the spraying rate is 0.5-1mL / min; the specific process of staged pressure reduction drying is as follows: maintain a vacuum of 100mbar for the first 10-15min, and reduce the vacuum to 30mbar for the next 30-45min.

9. A method for preparing a self-healing multi-matrix sealing material according to claim 1 or 2, characterized in that, In step S3, the alkaline activator is at least one of potassium hydroxide, sodium hydroxide, sodium carbonate, sodium silicate, potassium silicate, and potassium carbonate.

10. The self-healing multi-matrix sealing material prepared by the preparation method according to any one of claims 1-9.

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