Method and application of CO2 nanobubbles synergistically hydrophobically modified to strengthen solid waste filling materials

Abstract

The present invention discloses a method and application of CO2 nanobubble-coordinated hydrophobic modification to strengthen solid waste filling materials, and the technical field of high-carbon-fixing, strong-impermeability, all-solid waste filling materials. Coal mine solid waste is uniformly mixed with silicon dioxide nanoparticles and aluminum nanoparticles to obtain a solid material, sodium silicate is added to water, and then sodium hydroxide is added to obtain a strong base excitation solution; polydimethylsiloxane and a silane coupling agent are added to the strong base excitation solution, and emulsified to obtain a strong base-hydrophobic modified composite solution; xanthan gum, polyvinyl alcohol, and sodium dodecylbenzenesulfonate are added to deionized water for mixing, carbon dioxide is introduced through a diffuser, and then the carbon dioxide gas is dispersed and homogenized in the base liquid to obtain a carbon dioxide nanobubble fluid; the solid material, the strong base-hydrophobic modified composite solution and the carbon dioxide nanobubble fluid are mixed and stirred to generate a high-carbon-fixing, strong-impermeability, all-solid waste filling material. It has a simple configuration and high use effect, and can effectively support the goaf while consuming a large amount of carbon dioxide.

Description

Technical Field

[0001] The present invention relates to a method and application of CO2 nanobubble-coordinated hydrophobic modification and strengthening of solid waste filling materials, belonging to the technical field of high-carbon-fixing, strong-impermeability, full-solid waste filling materials. Background Art

[0002] Coal mine solid waste disposal and CO2 storage are effective ways to achieve low-carbon development in the coal industry.

[0003] After the solid waste filling material is mineralized, the carbonate produced precipitates in the micropores, making its internal structure denser and improving the overall strength of the filling material. The mineralized solid waste material is filled into the goaf and, after solidification, bears the pressure of the roof, causing the filling body to compress and deform, and then cracks are formed and further developed inside it. In addition, the interior of the goaf often contains groundwater, and free water seeps into the cracks of the filling body, causing a water-weakening effect on the filling body and reducing the effectiveness of the filling treatment. The porous structure and hydrophilicity of the filling body promote its interaction with water, and the chloride ions and sulfate ions in the water will destroy the internal structure of the filling body. Therefore, the hydrophobic modification of the filling material to improve the impermeability, durability and stability are the main technologies to solve the problem of water weakening of the filling body.

[0004] Although hydrophobic modification can improve the impermeability of the filling body, the surface hydrophobic film may restrict the reaction between CO2 and solid waste materials, failing to achieve the desired mineralization effect. Therefore, developing a technology that synergistically enhances the mineralization and hydrophobicity of solid waste filling materials is one of the necessary conditions for realizing the underground utilization of CO2-mineralized solid waste filling materials. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a method and application of CO2 nanobubble-synergistic hydrophobic modification to strengthen solid waste filling materials. The preparation method is simple, the use effect is good, and it can effectively consume and seal carbon dioxide. At the same time, the resulting filling material also has good hydrophobicity, which can effectively isolate the invasion of groundwater on the construction area.

[0006] To achieve the above technical objectives, the preparation method of the CO2 nanobubble synergistic hydrophobic modification and strengthening solid waste filling material of the present invention comprises the following steps:

[0007] Step 1, uniformly mixing coal mine solid waste with silicon dioxide nanoparticles and aluminum nanoparticles to obtain a solid material, wherein the mass ratio of the coal mine solid waste, the silicon dioxide nanoparticles and the aluminum nanoparticles is (12-100): (1-10): 1, and the molar ratio of silicon, aluminum and sodium in the solid material satisfies (2-8): (1-5): 1;

[0008] Step 2: adding sodium silicate to water, mixing and stirring to obtain an alkaline base liquid, and then adding sodium hydroxide to the alkaline base liquid, mixing and stirring to obtain a strong base excitation solution; wherein the mass ratio of sodium silicate, sodium hydroxide and water is (1-60):(1-30):100;

[0009] Step 3, adding polydimethylsiloxane and a silane coupling agent to the strong base excitation solution prepared in step 2, and performing emulsification treatment to obtain a strong base-hydrophobically modified composite solution; wherein the mass ratio of polydimethylsiloxane, silane coupling agent and strong base excitation solution is (1-25):(0.05-1.25):375;

[0010] Step 4: Add xanthan gum, polyvinyl alcohol, and sodium dodecylbenzenesulfonate to deionized water and mix them, and stir them evenly to obtain a base liquid; wherein the mass ratio of xanthan gum, polyvinyl alcohol, sodium dodecylbenzenesulfonate and water is (1-80):(1-25):(1-50):1000,

[0011] Step 5: introducing carbon dioxide into the base liquid obtained in step 4 through a diffuser, and then using a carbon dioxide homogenization system to disperse and homogenize the carbon dioxide gas in the base liquid to obtain a carbon dioxide nanobubble fluid; the volume ratio of the carbon dioxide gas to the base liquid is (5-45):100, wherein the carbon dioxide gas is at normal pressure;

[0012] Step 6: Mix and stir the solid material prepared in step 1, the strong base-hydrophobic modified composite solution prepared in step 3, and the carbon dioxide nanobubble fluid prepared in step 5 to generate a high-carbon-solidified, highly impermeable, all-solid waste filling material; wherein the mass ratio of the solid material, the strong base-hydrophobic modified composite solution, and the carbon dioxide nanobubble fluid is 6:(2.5-4.7):(1.3-2.8).

[0013] Furthermore, the coal mine solid waste in step 1 includes slag, fly ash, and coal gangue, wherein the particle size of the slag and fly ash is 0.3 to 200 μm, the particle size of the coal gangue after grinding is 1 to 1000 μm, the particle size of the silica nanoparticles is 2.5 to 250 nm, and the particle size of the alumina nanoparticles is 10 to 500 nm.

[0014] Furthermore, the pH value of the strong base excitation solution obtained in step 2 is 10-14.

[0015] Furthermore, the emulsification treatment in step 3 is achieved by stirring, the stirring rate of the emulsification treatment is 800-3000 r / min, the emulsification treatment time is 5-30 min, and the viscosity of the obtained strong base-hydrophobic modification composite solution is 10-120 mPa.s.

[0016] Furthermore, in step 4, xanthan gum, polyvinyl alcohol, sodium dodecylbenzenesulfonate and water are stirred and mixed at a stirring rate of 500 to 1500 r / min and a stirring time of 30 to 150 min. The viscosity of the base liquid obtained after mixing is 50 to 250 mPa.s.

[0017] Furthermore, in step 5, the injection flow rate of carbon dioxide injected through the diffuser is 2-500 mL / min, the homogenization rate is 1000-10000 r / min, the processing time is 2-20 min, and the viscosity of the obtained carbon dioxide nanobubble fluid is 25-500 mPa.s.

[0018] Furthermore, the high carbon-fixing and strong anti-permeability all-solid waste filling material in step 6 has a viscosity of 420 to 10,000 mPa.s, a pH value of 9 to 14, and a solidification time of 50 to 800 minutes.

[0019] Furthermore, in step 6, the carbon fixation rate of the high carbon fixation and strong anti-permeability all-solid waste filling material is 1.4-40.2 mgCO2 / g filling material, the surface contact angle of the material is 95-140°, and the water absorption rate is 15-80%.

[0020] A method for preparing a solid waste filling material strengthened by CO2 nanobubbles in synergistic hydrophobic modification is disclosed to prepare a high-carbon-fixing, highly impermeable, all-solid waste filling material.

[0021] Application of a high carbon-fixing, strong anti-permeability all-solid waste filling material:

[0022] In underground working faces, high-carbon-fixed, high-permeability, all-solid waste filling materials are used to fill goafs. After solidification, the surface of high-carbon-fixed, high-permeability, all-solid waste filling materials exhibits hydrophobic properties, which can effectively prevent the infiltration of mine water and reduce the problem of reduced material strength caused by water weakening and crack development in the filling materials.

[0023] High-carbon-fixed, highly impermeable, all-solid waste filling materials are injected into the overburden cracks near the mining working face. After drilling, they are sealed step by step using high-carbon-fixed, highly impermeable, all-solid waste filling materials. In addition, in the event of water infiltration, the hydrophobic properties of the material can prevent water from continuing to infiltrate the working face and divert the water to the water storage area.

[0024] Beneficial effects:

[0025] 1. In this method, CO2 is treated with nanobubbles to increase the specific surface area of ​​CO2 and improve the efficiency of the carbonization reaction between CO2 and materials under normal temperature and pressure conditions. The carbon dioxide nanobubble fluid prepared by this method can be stably stored for 1 to 10 days under normal temperature and pressure conditions. It has a long shelf life and is easy to transport, and does not need to be prepared near the use area.

[0026] 2. This method achieves the synergistic treatment of improving CO2 carbonization efficiency, CO2 solid-state coal mine goaf storage, and preventing water weakening of filling materials, thus achieving the goals of "double carbonization" and green mining, and also solving the safety hazards of CO2 storage instability and water weakening of filling materials.

[0027] 3. The CO2 nanobubbles of the present invention cooperate with the hydrophobic modification to strengthen the hydrophobicity of the solid waste filling material, and provide good support capacity for the underground. At the same time, the carbon dioxide can be sealed in a solid form in a high-carbon-fixing, strong and impermeable all-solid waste filling material. The solid-state sealing has better stability and solves the problem of carbon dioxide gas leakage. The high-carbon-fixing, strong and impermeable all-solid waste filling body involved in this method is stronger than the existing filling body. While having a good gelling effect, it reduces the water absorption rate of the material, prevents the water weakening of the filling body, and increases the absorption rate of CO2 in the filling body. Combined with the utilization of all solid waste, it avoids the environmental pollution caused by the use of a large amount of cement, and provides a new way for cemented filling mining. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are further described below:

[0029] The disclosed method of CO2 nanobubbles in the present invention for synergistic hydrophobic modification and strengthening of solid waste filling materials comprises the following specific steps:

[0030] Step 1: uniformly mixing solid wastes such as slag, fly ash, and coal gangue with silicon dioxide nanoparticles and aluminum nanoparticles to obtain a solid material;

[0031] Step 2: adding sodium silicate to water, mixing and stirring to obtain an alkaline base liquid, and then adding sodium hydroxide to the alkaline base liquid, mixing and stirring to obtain a strong base excitation solution;

[0032] Step 3: adding polydimethylsiloxane and a silane coupling agent to the strong base excitation solution in step 2, and emulsifying to obtain a strong base-hydrophobic modification composite solution;

[0033] Step 4: Add xanthan gum, polyvinyl alcohol, and sodium dodecylbenzenesulfonate to deionized water, mix, and stir to obtain a base solution;

[0034] Step 5: CO2 is introduced into the base liquid in step 4 through a diffuser, and then the CO2 is dispersed and homogenized by a homogenizing system to obtain a CO2 nanobubble fluid;

[0035] Step 6: Mix and stir the solid material of step 1, the strong base-hydrophobic modified composite solution of step 3, and the CO2 nanobubble fluid of step 5 to prepare a high-carbon-fixing, strong and impermeable all-solid waste filling material for downhole filling applications.

[0036] As a specific implementation, in step 1, the particle size of the slag and fly ash after grinding is 0.3 to 200 μm, the particle size of the coal gangue after grinding is 1 to 1000 μm, the particle size of the silica nanoparticles is 2.5 to 250 nm, the particle size of the alumina nanoparticles is 10 to 500 nm, and the molar ratio of silicon to aluminum sodium in the solid material is 2 to 8:1 to 5:1, thereby ensuring that the solid waste can fully react.

[0037] As a specific embodiment, in step 2, the mass ratio of sodium silicate, sodium hydroxide and water is 1-60:1-30:100, and the pH value of the obtained strong base excitation solution is 10-14, thereby ensuring that the raw materials are fully activated.

[0038] As a specific embodiment, in step 3, the mass ratio of polydimethylsiloxane, silane coupling agent and strong base excitation solution is 1-25:0.05-1.25:375, the stirring rate of the emulsification treatment is 800-3000 r / min, the emulsification treatment time is 5-30 min, and the obtained strong base-hydrophobic modified composite solution has a viscosity of 10-120 mPa.s, thereby ensuring that the material has hydrophobic properties after curing.

[0039] As a specific embodiment, in step 4, the mass ratio of xanthan gum, polyvinyl alcohol, sodium dodecylbenzenesulfonate and water is 1-80:1-25:1-50:1000, the stirring rate is 500-1500 r / min, the stirring time is 30-150 min, and the viscosity of the obtained base liquid is 50-250 mPa.s, thereby ensuring that the CO2 nanobubbles are stably suspended in the base liquid.

[0040] As a specific embodiment, in step 5, the volume ratio of CO2 to base liquid is 5-45:100, the CO2 injection flow rate is 2-500 mL / min, the homogenization rate is 1000-10000 r / min, the processing time is 2-20 min, and the viscosity of the obtained CO2 nanobubble fluid is 25-500 mPa.s, thereby ensuring a certain mineralization reaction rate and efficiency.

[0041] As a specific embodiment, the carbon dioxide homogenization system in step 5 includes: a carbon dioxide cylinder, a carbon dioxide nanobubble fluid container, and a homogenizer; the gas outlet of the carbon dioxide cylinder is connected to an air injection pipeline via a pressure reducing valve, the end of the air injection pipeline is connected to a diffuser and penetrates the bottom of the carbon dioxide nanobubble fluid container containing a base liquid, the air injection pipeline is sequentially installed with an on-off valve and a flowmeter as detection devices, the upper end of the homogenizer is equipped with a high-speed rotation device, and the lower end is connected to a stirring blade. While the injected carbon dioxide is dispersed in the base liquid through the diffuser, the homogenizer rotates the stirring blade at the lower end at high speed, generating high-intensity shear force, thereby reducing the volume of the carbon dioxide to the nanometer scale. Combined with the viscosity and adsorption properties of the base liquid, the speed at which the carbon dioxide nanobubbles rise is reduced, thereby obtaining the carbon dioxide nanobubble fluid required by the present application.

[0042] As a specific embodiment, the carbon dioxide nanobubble fluid in step 5 can be stably stored for 1 to 10 days under normal temperature and pressure conditions, thereby ensuring the carbonization reaction when the fluid is stirred with the solid material.

[0043] As a specific embodiment, the mass ratio of the solid material, the strong base-hydrophobic modified composite solution and the CO2 nanobubble fluid in step 6 is 6:2.5~4.7:1.3~2.8, thereby ensuring that the material has high carbon absorption and strong hydrophobic properties after solidification.

[0044] As a specific implementation, the high carbon-fixing and strong anti-permeability all-solid waste filling material in step 6 has a viscosity of 420 to 10,000 mPa.s, a pH value of 9 to 14, and a solidification time of 50 to 800 minutes.

[0045] As a specific embodiment, the high-carbon-fixing and highly impermeable all-solid waste filling material prepared in step 6 has a carbon fixation rate of 1.4 mgCO2 / g filling material to 40.2 mgCO2 / g filling material, a water contact angle of 95 to 140°, and a water absorption rate of 15 to 80%.

[0046] Example 1

[0047] In order to better understand the method provided by the present invention for preparing a high-carbon-fixing, strong, and impermeable all-solid waste filling material by using CO2 nanobubbles in conjunction with hydrophobic modification, the following will be described in detail with reference to the examples. The specific steps are as follows:

[0048] Step 1: Grind slag, fly ash, and coal gangue to particle sizes of 150 μm, 125 μm, and 550 μm, respectively, and evenly mix them with silicon dioxide nanoparticles with a particle size of 75 nm and aluminum nanoparticles with a particle size of 100 nm;

[0049] Step 2: Sodium silicate and sodium hydroxide are added to water in a mass ratio of 30:20:100 and uniformly mixed to form an alkaline base liquid with a pH value of 14;

[0050] Step 3: adding polydimethylsiloxane and a silane coupling agent to the strong base excitation solution in step 2 at a mass ratio of 10:0.5:375 and emulsifying at a rate of 2500 r / min for 20 min to convert it into a strong base-hydrophobic modification composite solution;

[0051] Step 4: Add xanthan gum, polyvinyl alcohol, and sodium dodecylbenzenesulfonate to deionized water in a mass ratio of 10:3.5:7:1000 and mix uniformly at 1000 rpm for 120 minutes to prepare a base solution;

[0052] Step 5: CO2 was introduced into the base liquid in step 4 at a volume ratio of 25:100 at a flow rate of 150 mL / min through a diffuser, and then the CO2 was dispersed and homogenized at a homogenization rate of 8000 r / min for 5 minutes using a homogenization system to obtain a CO2 nanobubble fluid;

[0053] Step 6: Mix and stir the solid material of step 1, the strong base-hydrophobic modified composite solution of step 3, and the CO2 nanobubble fluid of step 5 to make a new type of high-carbon solid and strong anti-permeability all-solid waste filling material, pour it into a 50mm×100mm (column) and 70.7mm×70.7mm×70.7mm (square) test mold, and then immediately vibrate the specimen on a vibrating table. Place the formed specimen in a standard constant temperature and humidity curing box with a temperature of 25±2°C and a humidity of 60±5% for standard curing for 48 hours, then demould. After demoulding, number the test blocks and continue to place them in the curing box for curing until the curing age reaches 28 days. After reaching the curing age, the columnar test blocks are subjected to a uniaxial compressive test to test the compressive strength of the test blocks.

[0054] Step 7. Use 400-grit sandpaper to polish the surface of the square test block, and then place it in the surface hydrophilicity test device to measure the contact angle of the test block surface. In order to reduce the error value of the experiment, the water droplet on the surface of the test block needs to be kept for 5 minutes before photographing and measuring the contact angle between the water droplet and the test block surface. The contact angle of each surface of the test block with the water droplet is photographed and measured more than three times.

[0055] Step 8: Air-dry the square test block in a 60°C constant temperature oven for 24 hours. Once the test block returns to ambient temperature, record its initial mass. Then, immerse the air-dried test block in water. Record the hourly mass change for the first 6 hours, and the mass change every 12 hours after the first 6 hours. The total test duration is 102 hours. Finally, calculate the relationship between the cumulative water absorption rate and the mass change of the test block. To reduce experimental error, use three or more test blocks for water absorption test simultaneously. Wipe off the surface moisture of the test block for each mass record, and repeat the mass record three times.

[0056] Example 2

[0057] In order to better understand the method provided by the present invention for preparing a high-carbon-fixing, strong, and impermeable all-solid waste filling material by using CO2 nanobubbles in conjunction with hydrophobic modification, the following will be described in detail with reference to the examples. The specific steps are as follows:

[0058] Step 1: Grind slag, fly ash, and coal gangue to particle sizes of 150 μm, 125 μm, and 550 μm, respectively, and evenly mix them with silicon dioxide nanoparticles with a particle size of 75 nm and aluminum nanoparticles with a particle size of 100 nm;

[0059] Step 2: Sodium silicate and sodium hydroxide are added to water in a mass ratio of 30:20:100 and uniformly mixed to form an alkaline base liquid with a pH value of 14;

[0060] Step 3: adding polydimethylsiloxane and a silane coupling agent to the strong base excitation solution in step 2 at a mass ratio of 5:0.25:375 and emulsifying at a rate of 2500 r / min for 20 min to convert it into a strong base-hydrophobic modification composite solution;

[0061] Step 4: Add xanthan gum, polyvinyl alcohol, and sodium dodecylbenzenesulfonate to deionized water in a mass ratio of 10:3.5:7:1000 and mix uniformly at 1000 rpm for 120 minutes to prepare a base solution;

[0062] Step 5: CO2 was introduced into the base liquid in step 4 at a volume ratio of 25:100 at a flow rate of 150 mL / min through a diffuser, and then the CO2 was dispersed and homogenized at a homogenization rate of 8000 r / min for 5 minutes using a homogenization system to obtain a CO2 nanobubble fluid;

[0063] Step 6: Mix and stir the solid material of step 1, the strong base-hydrophobic modified composite solution of step 3, and the CO2 nanobubble fluid of step 5 to make a new type of high-carbon solid and strong anti-permeability all-solid waste filling material, pour it into a 50mm×100mm (column) and 70.7mm×70.7mm×70.7mm (square) test mold, and then immediately vibrate the specimen on a vibrating table. Place the formed specimen in a standard constant temperature and humidity curing box with a temperature of 25±2°C and a humidity of 60±5% for standard curing for 48 hours, then demould. After demoulding, number the test blocks and continue to place them in the curing box for curing until the curing age reaches 28 days. After reaching the curing age, the columnar test blocks are subjected to a uniaxial compressive test to test the compressive strength of the test blocks.

[0064] Step 7. Use 400-grit sandpaper to polish the surface of the square test block, and then place it in the surface hydrophilicity test device to measure the contact angle of the test block surface. In order to reduce the error value of the experiment, the water droplet on the surface of the test block needs to be kept for 5 minutes before photographing and measuring the contact angle between the water droplet and the test block surface. The contact angle of each surface of the test block with the water droplet is photographed and measured more than three times.

[0065] Step 8: Air-dry the square test block in a 60°C constant temperature oven for 24 hours. Once the test block returns to ambient temperature, record its initial mass. Then, immerse the air-dried test block in water. Record the hourly mass change for the first 6 hours, and the mass change every 12 hours after the first 6 hours. The total test duration is 102 hours. Finally, calculate the relationship between the cumulative water absorption rate and the mass change of the test block. To reduce experimental error, use three or more test blocks for water absorption test simultaneously. Wipe off the surface moisture of the test block for each mass record, and repeat the mass record three times.

[0066] Example 3

[0067] In order to better understand the method provided by the present invention for preparing a high-carbon-fixing, strong, and impermeable all-solid waste filling material by using CO2 nanobubbles in conjunction with hydrophobic modification, the following will be described in detail with reference to the examples. The specific steps are as follows:

[0068] Step 1: Grind slag, fly ash, and coal gangue to particle sizes of 150 μm, 125 μm, and 550 μm, respectively, and evenly mix them with silicon dioxide nanoparticles with a particle size of 75 nm and aluminum nanoparticles with a particle size of 100 nm;

[0069] Step 2: Sodium silicate and sodium hydroxide are added to water in a mass ratio of 30:20:100 and uniformly mixed to form an alkaline base liquid with a pH value of 14;

[0070] Step 3: adding polydimethylsiloxane and a silane coupling agent to the strong base excitation solution in step 2 at a mass ratio of 10:0.5:375 and emulsifying at a rate of 2500 r / min for 20 min to convert it into a strong base-hydrophobic modification composite solution;

[0071] Step 4: Add xanthan gum, polyvinyl alcohol, and sodium dodecylbenzenesulfonate to deionized water in a mass ratio of 10:3.5:7:1000 and mix uniformly at 1000 rpm for 120 minutes to prepare a base solution;

[0072] Step 5: CO2 was introduced into the base liquid in step 4 at a volume ratio of 20:100 at a flow rate of 100 mL / min through a diffuser, and then the CO2 was dispersed and homogenized for 5 minutes using a homogenization system at a homogenization rate of 8000 r / min to obtain a CO2 nanobubble fluid;

[0073] Step 6: Mix and stir the solid material of step 1, the strong base-hydrophobic modified composite solution of step 3, and the CO2 nanobubble fluid of step 5 to make a new type of high-carbon solid and strong anti-permeability all-solid waste filling material, pour it into a 50mm×100mm (column) and 70.7mm×70.7mm×70.7mm (square) test mold, and then immediately vibrate the specimen on a vibrating table. Place the formed specimen in a standard constant temperature and humidity curing box with a temperature of 25±2°C and a humidity of 60±5% for standard curing for 48 hours, then demould. After demoulding, number the test blocks and continue to place them in the curing box for curing until the curing age reaches 28 days. After reaching the curing age, the columnar test blocks are subjected to a uniaxial compressive test to test the compressive strength of the test blocks.

[0074] Step 7. Use 400-grit sandpaper to polish the surface of the square test block, and then place it in the surface hydrophilicity test device to measure the contact angle of the test block surface. In order to reduce the error value of the experiment, the water droplet on the surface of the test block needs to be kept for 5 minutes before photographing and measuring the contact angle between the water droplet and the test block surface. The contact angle of each surface of the test block with the water droplet is photographed and measured more than three times.

[0075] Step 8: Air-dry the square test block in a 60°C constant temperature oven for 24 hours. Once the test block returns to ambient temperature, record its initial mass. Then, immerse the air-dried test block in water. Record the hourly mass change for the first 6 hours, and the mass change every 12 hours after the first 6 hours. The total test duration is 102 hours. Finally, calculate the relationship between the cumulative water absorption rate and the mass change of the test block. To reduce experimental error, use three or more test blocks for water absorption test simultaneously. Wipe off the surface moisture of the test block for each mass record, and repeat the mass record three times.

[0076] The performance of the solidified solids of high carbon fixation and strong anti-permeability all-solid waste filling materials prepared by the CO2 nanobubbles prepared in Examples 1-3 and synergistically with hydrophobic modification was compared. The comparative examples in the following table were prepared according to the ratio of Example 1, but without CO2 nanobubbles and hydrophobic treatment:

[0077] Table 1 Compressive strength of high carbon solidification and strong anti-permeability all-solid waste filling materials after different curing times and immersion in mine water

[0078]

[0079]

[0080] Table 2 Surface contact angle, water absorption rate and CO2 absorption rate of high carbon-fixing and strong anti-permeability all-solid waste filling materials

[0081] serial number Surface contact angle Water absorption / % <![CDATA[CO2 absorption rate / mgCO2 / g material]]> Example 1 124.7° 5.26 35.2 Example 2 110.8° 7.29 33.6 Example 3 123.4° 5.41 24.8 Comparative Example 66.5° 14.6 4.2

[0082] Compared with filling materials that have not been treated with CO2 nanobubbles and hydrophobic modification, the preparation method of CO2 nanobubbles synergistically hydrophobically modified and reinforced solid waste filling materials provided in this application innovatively combines the improvement of CO2 carbonization, CO2 solid coal goaf storage, and prevention and control of water weakening of filling materials. On the one hand, it effectively utilizes the coal-based solid waste generated by coal mining while improving the safety and stability problems of CO2 storage in coal mine goafs; on the other hand, while improving CO2 storage, it solves the water weakening of filling materials after being soaked in water in mines and various mining risks, providing new ideas for achieving "dual carbon" and green mining in mines. Therefore, compared with the existing technology, it has the following advantages:

[0083] 1. CO2 is treated with nanobubbles to increase its specific surface area and improve the carbonization reaction efficiency between CO2 and materials at room temperature and pressure;

[0084] 2. The system achieves the coordinated treatment of improving CO2 carbonization efficiency, CO2 solid-state coal mine goaf storage, and preventing water weakening of filling materials, thus achieving the goals of "double carbonization" and green mining, and also solving the safety hazards of CO2 storage instability and water weakening of filling materials;

[0085] 3. By adopting the filling material preparation method of the present application, the strength of the high-carbon-fixing and high-impermeability all-solid waste filling body is better than that of the existing filling body. While having a good cementing effect, it reduces the water absorption rate of the material, prevents the water weakening of the filling body, and increases the absorption rate of CO2 in the filling body. Combined with the utilization of all-solid waste, it avoids the environmental pollution caused by the use of a large amount of cement, and provides a new way for cemented filling mining.

Claims

1. A method for preparing a solid waste filling material by synergistically hydrophobically modifying CO2 nanobubbles, characterized in that: The following steps are involved: Step 1, uniformly mixing coal mine solid waste with silicon dioxide nanoparticles and aluminum nanoparticles to obtain a solid material, wherein the mass ratio of the coal mine solid waste, silicon dioxide nanoparticles and aluminum nanoparticles is (12-100): (1-10): 1, and the molar ratio of silicon, aluminum and sodium in the solid material satisfies (2-8): (1-5): 1; Step 2: adding sodium silicate to water, mixing and stirring uniformly to obtain an alkaline base liquid, and then adding sodium hydroxide to the alkaline base liquid, mixing and stirring uniformly to obtain a strong base excitation solution; wherein the mass ratio of sodium silicate, sodium hydroxide and water is (1-60): (1-30): 100; Step 3: adding polydimethylsiloxane and a silane coupling agent to the strong base excitation solution prepared in step 2, and performing emulsification treatment to obtain a strong base-hydrophobic modification composite solution; The mass ratio of polydimethylsiloxane, silane coupling agent and strong base excitation solution is (1-25): (0.05-1.25): 375; Step 4: Add xanthan gum, polyvinyl alcohol, and sodium dodecylbenzenesulfonate to deionized water and mix them, stirring them evenly to obtain a base liquid; wherein the mass ratio of xanthan gum, polyvinyl alcohol, sodium dodecylbenzenesulfonate and water is (1-80): (1-25): (1-50): 1000. Step 5: introducing carbon dioxide into the base liquid obtained in step 4 through a diffuser, and then using a carbon dioxide homogenization system to disperse and homogenize the carbon dioxide gas in the base liquid to obtain a carbon dioxide nanobubble fluid; the volume ratio of the carbon dioxide gas to the base liquid is (5-45):100, wherein the carbon dioxide gas is at normal pressure; Step 6: Mixing and stirring the solid material prepared in step 1, the strong base-hydrophobic modified composite solution prepared in step 3, and the carbon dioxide nanobubble fluid prepared in step 5 to produce a high-carbon-fixing, strong, and impermeable all-solid waste filling material; wherein the mass ratio of the solid material, the strong base-hydrophobic modified composite solution, and the carbon dioxide nanobubble fluid is 6:(2.5-4.7):(1.3-2.8); The carbon dioxide homogenization system includes: a carbon dioxide gas cylinder, a carbon dioxide nanobubble fluid container and a homogenizer; the gas outlet of the carbon dioxide gas cylinder is connected to the gas injection pipe through a pressure reducing valve, the end of the gas injection pipe is connected to a diffuser and penetrates the bottom of the carbon dioxide nanobubble fluid container containing base liquid. The gas injection pipe is sequentially installed with a switch valve and a flow meter as detection devices. The upper end of the homogenizer is equipped with a high-speed rotation device, and the lower end is connected to a stirring blade.

2. The method for preparing a CO2 nanobubble-assisted hydrophobic modified reinforced solid waste filling material according to claim 1, characterized in that: The coal mine solid waste in step 1 includes slag, fly ash, and coal gangue, wherein the particle size of slag and fly ash is 0.3-200 μm, the particle size of coal gangue after grinding is 1-1000 μm, the particle size of silicon dioxide nanoparticles is 2.5-250 nm, and the particle size of aluminum oxide nanoparticles is 10-500 nm.

3. The method for preparing a CO2 nanobubble-assisted hydrophobic modified reinforced solid waste filling material according to claim 1, characterized in that: The pH value of the strong base excitation solution obtained in step 2 is 10-14.

4. The method for preparing a CO2 nanobubble-assisted hydrophobic modified reinforced solid waste filling material according to claim 1, characterized in that: The emulsification treatment in step 3 is achieved by stirring, the stirring rate of the emulsification treatment is 800-3000 r / min, the emulsification treatment time is 5-30 min, and the viscosity of the obtained strong base-hydrophobic modification composite solution is 10-120 mPa.s.

5. The method for preparing a CO2 nanobubble-assisted hydrophobic modified and reinforced solid waste filling material according to claim 1, characterized in that: In step 4, xanthan gum, polyvinyl alcohol, sodium dodecylbenzenesulfonate and water are stirred and mixed at a stirring rate of 500 to 1500 r / min and a stirring time of 30 to 150 min. The viscosity of the base liquid obtained after mixing is 50 to 250 mPa.s.

6. The method for preparing a CO2 nanobubble-assisted hydrophobic modified reinforced solid waste filling material according to claim 1, characterized in that: In step 5, the injection flow rate of carbon dioxide injected through the diffuser is 2-500 mL / min, the homogenization rate is 1000-10000 r / min, the processing time is 2-20 min, and the viscosity of the obtained carbon dioxide nanobubble fluid is 25-500 mPa.s.

7. The method for preparing a CO2 nanobubble-assisted hydrophobic modified and reinforced solid waste filling material according to claim 1, characterized in that: The viscosity of the high-carbon-fixing, strong and impermeable all-solid waste filling material in step 6 is 420 to 10,000 mPa.s, the pH value is 9 to 14, and the solidification time is 50 to 800 minutes.

8. The method for preparing a CO2 nanobubble-assisted hydrophobic modified reinforced solid waste filling material according to claim 1, characterized in that: In the step 6, the carbon fixation rate of the high carbon fixation and strong anti-permeability all-solid waste filling material is 1.4-40.2 mgCO2 / g filling material, the surface contact angle of the material is 95-140°, and the water absorption rate is 15-80%.

9. A high-carbon-fixing, strong and impermeable solid waste filling material prepared by the preparation method of CO2 nanobubbles synergistically hydrophobically modified and strengthened solid waste filling material according to claim 1.

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