Method for preparing low-carbon waste incineration fly ash (MSWIFA) cement-based material through carbonization of modified nano solution and application of low-carbon waste incineration fly ash (MSWIFA) cement-based material

Abstract

The invention discloses a method for preparing a low-carbon waste incineration fly ash (MSWIFA) cement-based material through carbonization of a modified nano solution and application of the MSWIFA cement-based material, according to the method, nano silicon dioxide is dispersed in a VTES (vinyltriethoxysilane) ethanol solution to serve as a medium for carbonization modification of the MSWIFA, and meanwhile the carbonization degree of the MSWIFA is improved through an ethanolamine solution. The carbonized and modified MSWIFA is used as a supplementary cementing material to be doped into the cement-based material, so that the compressive strength of the cement-based material can be improved, and heavy metal ions in the MSWIFA can be consolidated. Most importantly, the carbonization method provided by the invention is superior to the traditional carbonization method, the steps of suction filtration, drying and the like are not needed in the carbonization modification process, fine-particle micro powder is reserved, the energy consumption in the carbonization process is reduced, the time is saved, and the carbonization efficiency is improved. The building material produced by using the modified MSWIFA reduces environmental pollution, has good thermal insulation characteristics, and achieves the goals of environmental protection, energy conservation and emission reduction.

Description

Technical Field

[0001] The invention relates to the preparation of cement-based materials, and more specifically to a method for preparing low-carbon waste incineration fly ash (MSWIFA) cement-based materials by carbonization of a modified nano-solution and application thereof. Background Art

[0002] The total amount of domestic waste in my country now reaches hundreds of millions of tons per year. The MSWIFA produced after the incineration of domestic waste is rich in heavy metals such as Pb, Cu, Zn, Cr, etc., which need to be treated before they can be landfilled or used. At present, the use of cement cementitious materials to solidify MSWIFA is a common means of harmless disposal of fly ash. MSWIFA contains raw materials such as calcium oxide, silicon dioxide, aluminum oxide, calcium sulfate, etc., which can react with cement to produce CSH, calcium sulfonate and other stable structures that can solidify and stabilize the heavy metals in MSWIFA, and prepare cement parts with certain strength. However, the use of silicate cement to solidify MSWIFA also has many defects. The cement production process has high energy consumption and is accompanied by the production of a large amount of greenhouse gases. The strength of the solidified body is low and the heavy metal solidification effect is poor. The ultra-large specific surface area of ​​nanomaterials can serve as nucleation sites for cement hydration products, promote the generation and growth of hydration product CSH gel, and accelerate the hydration reaction process; in addition, nanomaterials can fill pores, refine the cement pore structure, and promote the formation of denser cement hydration products. If nanomaterials are added to silicate cement, it can be expected that nanomaterials can improve the stabilization effect of heavy metals in the cement to a certain extent. However, nanomaterials tend to agglomerate in the mortar environment and have poor diffusion effect.

[0003] MSWIFA is a typical alkaline waste rich in calcium. Accelerating carbonation can be used for fly ash reuse. The heavy metal ions in the fly ash react with CO2 to form insoluble carbonates. The heavy metal ions are stabilized inside due to chemical precipitation and physical encapsulation, thereby reducing the leaching toxicity of heavy metals. The carbonation reaction enhances the volcanic ash activity of MSWIFA, and the carbonized MSWIFA plays a positive role in the cement hydration reaction. The carbonized MSWIFA can be added to cement-based materials as a supplementary cementitious material, which can not only improve the compressive strength of cement-based materials, but also consolidate the heavy metal ions in MSWIFA. The carbonized MSWIFA can be added to cement-based materials as a supplementary cementitious material, which can effectively reduce the use of cement and has the effects of low carbon, environmental protection, and low economic cost.

[0004] The existing MSWIFA modification technology usually requires filtration, drying and other steps, which consumes a lot of energy. Therefore, a new low-carbon and environmentally friendly MSWIFA treatment method is urgently needed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing low-carbon waste incineration fly ash (MSWIFA) cement-based material by carbonization of modified nano-solution and its application, wherein nano-silicon dioxide is dispersed in a silane coupling agent vinyl triethoxysilane (VTES) ethanol solution as a medium for carbonization modification of MSWIFA, and an ethanolamine solution is used to improve the carbonization degree of MSWIFA, and a gas containing carbon dioxide (purity> 99%) is introduced into a reactor, and carbon dioxide reacts with MSWIFA to undergo carbonization reaction. The carbonized modified MSWIFA can be added to cement-based materials as a supplementary cementitious material, which can not only improve the compressive strength of the cement-based materials, but also consolidate the heavy metal ions in the MSWIFA.

[0006] The carbonization method mentioned in the present invention is superior to the traditional carbonization method. After carbonization modification, there is no need to perform filtration, drying and other steps, which not only reduces the energy consumption in the carbonization process, saves time, and improves the carbonization efficiency. The carbonized modified MSWIFA can be added to cement-based materials as a supplementary cementitious material, which can not only improve the compressive strength of the cement-based materials, but also consolidate the heavy metal ions in the MSWIFA. Using the modified MSWIFA to produce building materials is an effective way to reduce carbon emissions, and has the effects of green environmental protection, energy saving and emission reduction.

[0007] Specifically, the present invention provides a method for preparing low-carbon waste incineration fly ash (MSWIFA) cement-based material by carbonization of modified nano-solution, comprising the following raw materials: MSWIFA, vinyl triethoxysilane (VTES), nano-silica, ethanolamine, water, and carbon dioxide gas; wherein VTES and nano-silica, ethanolamine, and carbon dioxide gas are used in sequence to carbonize and modify MSWIFA.

[0008] Preferably, the chemical composition of the MSWIFA satisfies 30-40% CaO, 3%-8% SiO2, and 1%-4% MgO; the particle size of the MSWIFA satisfies D50=20-30 μm, and the particle size range is 10-50 μm.

[0009] Preferably, the liquid-to-solid ratio of VTES to nano-silicon dioxide is 5:1-6:1 mL / g, and the ratio of VTES to water is 1:2-1:3.

[0010] Preferably, a hydrophilic amorphous flowable powder nano-silica with an average particle size of 20-30 nm is added to anhydrous ethanol and stirred, and then a mixed solution of VTES and water is added. After stirring, the suspension is subjected to ultrasonic dispersion treatment to obtain a VTES-modified nano-silica solution.

[0011] Preferably, the ethanolamine is configured as a 1-2 wt % ethanolamine solution to participate in the modification of MSWIFA.

[0012] Preferably, the introduction rate of carbon dioxide gas is 2-3 L / min, the reaction pressure is 0.5-1 MPa, the reaction time is 1-3 h, the reaction temperature is 20-30° C., and the humidity is 50-80%; the carbon dioxide gas is a high-purity gas with a mass fraction of 99-99.9%.

[0013] Preferably, the carbonized MSWIFA is mixed with ordinary Portland cement to improve the compressive strength of the cementitious material.

[0014] The detailed steps of the method of the present invention are:

[0015] Step 1: Collect MSWIFA, sieve the waste incineration fly ash through a 0.075mm square hole sieve, and take the waste incineration fly ash with a particle size of less than 0.075mm for subsequent use;

[0016] Step 2: Mix distilled water and waste incineration fly ash at a liquid-solid ratio of L / S=5-20:1, and stir magnetically at a speed of 300-500 r / min for 15-30 min;

[0017] Step 3: Use a suction filter to separate the distilled water from the mixed solution of distilled water + waste incineration fly ash to obtain solid waste incineration fly ash, use a 0.45 μm filter membrane for suction filtration, and then dry at 40-60° C. for 24-48 hours, take out after drying to constant mass, cool to room temperature, and sieve to obtain a homogeneous powder with a particle size range of 10-50 μm;

[0018] Step 4: Mix and stir the nano-silica and anhydrous ethanol to disperse the nano-silica in the anhydrous ethanol. Mix and stir the silane coupling agent vinyl triethoxysilane (VTES) and water to hydrolyze the VTES to obtain a VTES solution, pour the VTES solution into the anhydrous ethanol solution of the nano-silica, and stir to mix them to obtain a VTES-modified nano-silica solution; modify the nano-silica using VTES so that the nano-silica is evenly dispersed in the material;

[0019] Step 5: Mixing MSWIFA with VTES modified nano-silica solution to obtain a mixed slurry;

[0020] Step 6: Place the mixed slurry in a water bath device, put it into a microwave reactor, react for 30-40 min, react at 60-70° C., microwave power 300-400 W, and start the microwave reactor for water bath heating;

[0021] Step 7: Prepare 1-2wt% ethanolamine solution, perform ultrasonic oscillation, the oscillation frequency is 40-50KHz, the oscillation power is 25-35W, oscillate for 2s and rest for 3s, and cool after each oscillation for 15-20min, and repeat 4-6 times;

[0022] Step 8: placing the mixed slurry and the prepared ethanolamine solution in a reactor, heating and stirring in a water bath, introducing carbon dioxide gas into the reactor, adjusting the pressure and reaction time of the reactor, and performing a carbonization reaction;

[0023] Step 9: The carbonized mixed slurry is mixed with ordinary Portland cement to obtain a slurry mixture, wherein the slurry mixture is a mixture of waste incineration fly ash and ordinary Portland cement mortar, wherein the waste incineration fly ash content is 30%. The slurry mixture is molded and vibrated, and demolded after curing for 24 hours under standard curing conditions. After demolding, the specimen is moved into a high-temperature steam curing box at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to an age of 7d and 28d to obtain a test block.

[0024] The magnetic stirring in step 2 preferably has a rotation speed of 400 r / min and a time of 20 min.

[0025] In the step 3, the preferred drying temperature is 48° C. and the drying time is 36 hours.

[0026] In the step 4, the preferred liquid-to-solid ratio of VTES to nano-silicon dioxide is 5:1-6:1 mL / g, and the ratio of VTES to water is 1:2-1:3.

[0027] The nano-silica suspension in step 4 is preferably prepared by adding hydrophilic amorphous flowable powder nano-silica with an average particle size range of 20-30 nm to anhydrous ethanol and mixing and stirring, then adding a mixed solution of VTES and water and magnetically stirring at a speed of 200-300 r / min for 10-20 min, and ultrasonically dispersing the suspension for 30-40 min at a frequency of 40-50 KHz to obtain a VTES-modified nano-silica solution.

[0028] In step 6, the preferred microwave reaction time is 35 min, the reaction temperature is 65° C., and the microwave power is 350 W.

[0029] Preferably, in step 7, a 1.5%wt% ethanolamine solution is used, the ultrasonic oscillation frequency is preferably 45KHz, the oscillation power is 30W, the oscillation is 2s and the rest is 3s, and cooling is performed after each oscillation for 15min-20min, and this is repeated 4-6 times.

[0030] In the step 8, the preferred carbon dioxide gas introduction rate is 2-3 L / min, the reaction pressure is 0.5-1 MPa, the reaction time is 1-3 h, the reaction temperature is 20-30° C., the humidity is 50-80%, and the stirring rate is 200-300 r / min.

[0031] Beneficial effects of the present invention:

[0032] 1. After the waste incineration fly ash (MSWIFA) is modified, the present invention does not require steps such as filtration and drying, retains finer particles of micropowder, reduces energy consumption, and saves time.

[0033] 2. The present invention can effectively stabilize the heavy metals in MSWIFA, reduce the leaching of heavy metal ions, and reduce the pollution to the environment. After the introduction of carbon dioxide, the heavy metal ions in the solution react with it to form insoluble heavy metal carbonate precipitation, and the heavy metal ions are stabilized inside due to chemical precipitation and physical encapsulation.

[0034] 3. The nano-silicon dioxide suspension added in the present invention is used as a carbonization medium. Its high specific surface area can adsorb and consolidate heavy metals, and promote cement hydration as a nucleation site, generating more hydrated calcium silicate gel products, further improving the mechanical properties.

[0035] 4. The ethanolamine solution added in the present invention acts as a CO2 carrier, which increases the solubility of CO2 in the liquid phase and promotes the carbonization reaction rate on the surface of MSWIFA. Its alkaline environment promotes the formation of hydroxide or carbonate precipitation of heavy metal ions in MSWIFA.

[0036] 5 The present invention realizes the addition of MSWIFA as a supplementary cementitious material into cement-based materials, and the solidified body has high strength, and the heavy metal leaching concentration is far lower than the national solid waste leaching toxicity identification standard. The use of MSWIFA to replace part of cement as a building material while ensuring strength reduces environmental pollution and carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the process of waste incineration fly ash modification DETAILED DESCRIPTION

[0038] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0039] Example 1

[0040] The MSW incineration fly ash (MSWIFA) treatment process in this embodiment specifically includes the following steps:

[0041] (1) Collect MSWIFA, sieve the waste incineration fly ash through a 0.075 mm square hole sieve, and take the waste incineration fly ash with a particle size less than 0.075 mm for subsequent use;

[0042] (2) Distilled water and waste incineration fly ash were mixed at a liquid-solid ratio of L / S=10:1, and magnetically stirred at a speed of 400 r / min for 20 min; the mixed solution of distilled water + waste incineration fly ash was separated from the distilled water by a suction filter to obtain solid waste incineration fly ash, the filter membrane used for suction filtration was a 0.45 μm filter membrane, and then dried at 48°C for 36 h, and then taken out after drying to constant mass, cooled to room temperature, and the product was sieved through a 625-mesh sieve to obtain waste incineration fly ash with a particle size of 0.020 mm;

[0043] (3) After mixing and stirring 1% hydrophilic amorphous flowable powder nano-silica and anhydrous ethanol accounting for the mass fraction of MSWIFA, a mixed solution of silane coupling agent VTES and water was added, the liquid-to-solid ratio of silane coupling agent VTES to nano-silica was 5:1 mL / g, and the ratio of silane coupling agent VTES to water was 1:2. The suspension was prepared by magnetic stirring at a speed of 200 r / min for 10 min, and then the suspension was ultrasonically dispersed for 30 min at a frequency of 40 KHz to obtain a nano-silica suspension. MSWIFA was weighed and placed in a microwave reactor together with the nano-silica suspension. The reaction time was 35 min, the reaction temperature was 65°C, and the microwave power was 350 W.

[0044] (4) Prepare 1% ethanolamine solution, perform ultrasonic oscillation, the oscillation frequency is 45 kHz, the oscillation power is 30 W, oscillate for 2 seconds and rest for 3 seconds, and cool after each oscillation for 20 minutes, and repeat this process 6 times;

[0045] (5) adding the mixed solution obtained in (3) and the ethanolamine solution obtained in (4) into a reaction kettle, stirring with a magnetic force, and introducing a gas containing CO2 into the reaction kettle at a rate of 2 L / min, and continuing the reaction for 2 h;

[0046] (6) mixing the mixed slurry obtained after the carbonization in (5) with ordinary Portland cement, and then stirring in a cement mixer at a speed of 300 r / min for 5 minutes to obtain a slurry mixture;

[0047] (7) The slurry mixture is molded, vibrated, and placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 100%. After curing for 24 hours, the mold is removed. After the specimen is demolded, it is moved into a high-temperature steam curing chamber at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to 28 days to obtain a test block;

[0048] (8) The compressive strength of the test piece obtained by testing with a pressure testing machine is 45.2 MPa;

[0049] (9) The test block prepared in (7) was crushed until all of the test blocks passed through a 3 mm sieve, and then dried in a drying oven at 60 °C for 24 h;

[0050] (10) Deionized water was used as the leaching agent with a liquid-to-solid ratio of 10:1 (L / kg) and an amplitude of 40 mm. 2 g of solid sample was mixed into 20 mL of deionized water and then horizontally vibrated at 110 ± 10 times / min for 8 h. The mixture was allowed to stand for 16 h and finally filtered through a 0.45 μm membrane. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the concentration of heavy metals in the leachate.

[0051] Table 1 Example 1 mix ratio

[0052]

[0053] Table 2 Heavy metal leaching concentrations of original waste incineration fly ash and final product of Example 1

[0054] Heavy Metal Elements Crμg / L Cuμg / L Znμg / L Cdμg / L Pbμg / L Raw fly ash 232.60 174.30 6.45 26.85 20.36 Example 1 14.56 12.22 0.98 2.11 1.85

[0055] Example 2

[0056] The MSWIFA processing process in this embodiment specifically includes the following steps:

[0057] (1) Collect MSWIFA, sieve the waste incineration fly ash through a 0.075 mm square hole sieve, and take the waste incineration fly ash with a particle size less than 0.075 mm for subsequent use;

[0058] (2) Distilled water and waste incineration fly ash were mixed at a liquid-solid ratio of L / S=10:1, and magnetically stirred at a speed of 400 r / min for 20 min; the mixed solution of distilled water + waste incineration fly ash was separated from the distilled water by a suction filter to obtain solid waste incineration fly ash, the filter membrane used for suction filtration was a 0.45 μm filter membrane, and then dried at 48°C for 36 h, and then taken out after drying to constant mass, cooled to room temperature, and the product was sieved through a 625-mesh sieve to obtain waste incineration fly ash with a particle size of 0.020 mm;

[0059] (3) After mixing and stirring 2% hydrophilic amorphous flowable powder nano-silica and anhydrous ethanol, a mixed solution of silane coupling agent VTES and water was added, the liquid-to-solid ratio of silane coupling agent VTES to nano-silica was 5:1 mL / g, and the ratio of silane coupling agent VTES to water was 1:2. The suspension was prepared by magnetic stirring at a speed of 200 r / min for 10 min, and then the suspension was ultrasonically dispersed for 30 min at a frequency of 40 KHz to obtain a nano-silica suspension. MSWIFA was weighed and placed in a microwave reactor together with the nano-silica suspension. The reaction time was 35 min, the reaction temperature was 65°C, and the microwave power was 350 W.

[0060] (4) Prepare 1% ethanolamine solution, perform ultrasonic oscillation, the oscillation frequency is 45 kHz, the oscillation power is 30 W, oscillate for 2 seconds and rest for 3 seconds, and cool after each oscillation for 20 minutes, and repeat this process 6 times;

[0061] (5) adding the mixed solution obtained in (3) and the ethanolamine solution obtained in (4) into a reaction kettle, stirring with a magnetic force, and introducing a gas containing CO2 into the reaction kettle at a rate of 2 L / min, and continuing the reaction for 2 h;

[0062] (6) mixing the mixed slurry obtained after the carbonization in (5) with ordinary Portland cement, and then stirring in a cement mixer at a speed of 300 r / min for 5 minutes to obtain a slurry mixture;

[0063] (7) The slurry mixture is molded, vibrated, and placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 100%. After curing for 24 hours, the mold is removed. After the specimen is demolded, it is moved into a high-temperature steam curing chamber at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to 28 days to obtain a test block;

[0064] (8) The compressive strength of the test piece obtained by testing with a pressure testing machine was 48.2 MPa;

[0065] (9) The test block prepared in (7) was crushed until all of the test blocks passed through a 3 mm sieve, and then dried in a drying oven at 60 °C for 24 h;

[0066] (10) Deionized water was used as the leaching agent with a liquid-to-solid ratio of 10:1 (L / kg) and an amplitude of 40 mm. 2 g of solid sample was mixed into 20 mL of deionized water and then horizontally vibrated at 110 ± 10 times / min for 8 h. The mixture was allowed to stand for 16 h and finally filtered through a 0.45 μm membrane. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the concentration of heavy metals in the leachate.

[0067] Table 3 Example 2 mix ratio

[0068]

[0069] Table 4 Heavy metal leaching concentrations of original waste incineration fly ash and final product of Example 2

[0070] Heavy Metal Elements Crμg / L Cuμg / L Znμg / L Cdμg / L Pbμg / L Raw fly ash 232.60 174.30 6.45 26.85 20.36 Example 2 11.72 10.01 0.87 2.04 1.67

[0071] Example 3

[0072] The waste incineration fly ash treatment process in this embodiment specifically includes the following steps:

[0073] (1) Collect MSWIFA, sieve the waste incineration fly ash through a 0.075 mm square hole sieve, and take the waste incineration fly ash with a particle size less than 0.075 mm for subsequent use;

[0074] (2) Distilled water and waste incineration fly ash were mixed at a liquid-solid ratio of L / S=10:1, and magnetically stirred at a speed of 400 r / min for 20 min; the mixed solution of distilled water + waste incineration fly ash was separated from the distilled water by a suction filter to obtain solid waste incineration fly ash, the filter membrane used for suction filtration was a 0.45 μm filter membrane, and then dried at 48°C for 36 h, and then taken out after drying to constant mass, cooled to room temperature, and the product was sieved through a 625-mesh sieve to obtain waste incineration fly ash with a particle size of 0.020 mm;

[0075] (3) After mixing and stirring 3% hydrophilic amorphous flowable powder nano-silica and anhydrous ethanol, a mixed solution of silane coupling agent VTES and water was added, the liquid-to-solid ratio of silane coupling agent VTES to nano-silica was 5:1 mL / g, and the ratio of silane coupling agent VTES to water was 1:2. The suspension was prepared by magnetic stirring at a speed of 200 r / min for 10 min, and then the suspension was ultrasonically dispersed for 30 min at a frequency of 40 KHz to obtain a nano-silica suspension. MSWIFA was weighed and placed in a microwave reactor together with the nano-silica suspension. The reaction time was 35 min, the reaction temperature was 65°C, and the microwave power was 350 W.

[0076] (4) Prepare 1% ethanolamine solution, perform ultrasonic oscillation, the oscillation frequency is 45 kHz, the oscillation power is 30 W, oscillate for 2 seconds and rest for 3 seconds, and cool after each oscillation for 20 minutes, and repeat this process 6 times;

[0077] (5) adding the mixed solution obtained in (3) and the ethanolamine solution obtained in (4) into a reaction kettle, stirring with a magnetic force, and introducing a gas containing CO2 into the reaction kettle at a rate of 2 L / min, and continuing the reaction for 2 h;

[0078] (6) mixing the mixed slurry obtained after the carbonization in (5) with ordinary Portland cement, and then stirring in a cement mixer at a speed of 300 r / min for 5 minutes to obtain a slurry mixture;

[0079] (7) The slurry mixture is molded, vibrated, and placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 100%. After curing for 24 hours, the mold is removed. After the specimen is demolded, it is moved into a high-temperature steam curing chamber at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to 28 days to obtain a test block;

[0080] (8) The compressive strength of the test piece obtained by the pressure testing machine is 43.4 MPa;

[0081] (9) The test block prepared in (7) was crushed until all of the test blocks passed through a 3 mm sieve, and then dried in a drying oven at 60 °C for 24 h;

[0082] (10) Deionized water was used as the leaching agent with a liquid-to-solid ratio of 10:1 (L / kg) and an amplitude of 40 mm. 2 g of solid sample was mixed into 20 mL of deionized water and then horizontally vibrated at 110 ± 10 times / min for 8 h. The mixture was allowed to stand for 16 h and finally filtered through a 0.45 μm membrane. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the concentration of heavy metals in the leachate.

[0083] Table 5 Example 3 mix ratio

[0084]

[0085] Table 6 Heavy metal leaching concentrations of original waste incineration fly ash and final product of Example 3

[0086] Heavy Metal Elements Crμg / L Cuμg / L Znμg / L Cdμg / L Pbμg / L Raw fly ash 232.60 174.30 6.45 26.85 20.36 Example 3 16.72 13.34 1.41 2.52 2.36

[0087] Example 4

[0088] The waste incineration fly ash treatment process in this embodiment specifically includes the following steps:

[0089] (1) Collect MSWIFA, sieve the waste incineration fly ash through a 0.075 mm square hole sieve, and take the waste incineration fly ash with a particle size less than 0.075 mm for subsequent use;

[0090] (2) Distilled water and waste incineration fly ash were mixed at a liquid-solid ratio of L / S=10:1, and magnetically stirred at a speed of 400 r / min for 20 min; the mixed solution of distilled water + waste incineration fly ash was separated from the distilled water by a suction filter to obtain solid waste incineration fly ash, the filter membrane used for suction filtration was a 0.45 μm filter membrane, and then dried at 48°C for 36 h, and then taken out after drying to constant mass, cooled to room temperature, and the product was sieved through a 625-mesh sieve to obtain waste incineration fly ash with a particle size of 0.020 mm;

[0091] (3) After mixing 2% hydrophilic amorphous flowable powder nano-silica accounting for 2% of the mass fraction of MSWIFA and water, an ultrasonic dispersion treatment was performed for 30 min at a frequency of 40 kHz to obtain a nano-silica suspension. MSWIFA was weighed and placed in a microwave reactor together with the nano-silica solution. The reaction time was 35 min, the reaction temperature was 65° C., and the microwave power was 350 W.

[0092] (4) Prepare 1% ethanolamine solution, perform ultrasonic oscillation, the oscillation frequency is 45 kHz, the oscillation power is 30 W, oscillate for 2 seconds and rest for 3 seconds, and cool after each oscillation for 20 minutes, and repeat this process 6 times;

[0093] (5) adding the mixed solution obtained in (3) and the ethanolamine solution obtained in (4) into a reaction kettle, stirring with a magnetic force, and introducing a gas containing CO2 into the reaction kettle at a rate of 2 L / min, and continuing the reaction for 2 h;

[0094] (6) mixing the mixed slurry obtained after the carbonization in (5) with ordinary Portland cement, and then stirring in a cement mixer at a speed of 300 r / min for 5 minutes to obtain a slurry mixture;

[0095] (7) The slurry mixture is molded, vibrated, and placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 100%. After curing for 24 hours, the mold is removed. After the specimen is demolded, it is moved into a high-temperature steam curing chamber at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to 28 days to obtain a test block;

[0096] (8) The compressive strength of the test piece obtained by testing with a pressure testing machine is 45.3 MPa;

[0097] (9) The test block prepared in (7) was crushed until all of the test blocks passed through a 3 mm sieve, and then dried in a drying oven at 60 °C for 24 h;

[0098] (10) Deionized water was used as the leaching agent with a liquid-to-solid ratio of 10:1 (L / kg) and an amplitude of 40 mm. 2 g of solid sample was mixed into 20 mL of deionized water and then horizontally vibrated at 110 ± 10 times / min for 8 h. The mixture was allowed to stand for 16 h and finally filtered through a 0.45 μm membrane. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the concentration of heavy metals in the leachate.

[0099] Table 7 Example 4 mix ratio

[0100]

[0101] Table 8 Heavy metal leaching concentrations of original waste incineration fly ash and final product of Example 4

[0102] Heavy Metal Elements Crμg / L Cuμg / L Znμg / L Cdμg / L Pbμg / L Raw fly ash 232.60 174.30 6.45 26.85 20.36 Example 4 15.73 12.91 1.39 2.31 2.27

[0103] Comparative Example 1

[0104] (1) Collect MSWIFA, sieve the waste incineration fly ash through a 0.075 mm square hole sieve, and take the waste incineration fly ash with a particle size less than 0.075 mm for subsequent use;

[0105] (2) Distilled water and waste incineration fly ash were mixed at a liquid-solid ratio of L / S=10:1, and magnetically stirred at a speed of 400 r / min for 20 min; the mixed solution of distilled water + waste incineration fly ash was separated from the distilled water by a suction filter to obtain solid waste incineration fly ash, the filter membrane used for suction filtration was a 0.45 μm filter membrane, and then dried at 48°C for 36 h, and then taken out after drying to constant mass, cooled to room temperature, and the product was sieved through a 625-mesh sieve to obtain waste incineration fly ash with a particle size of 0.020 mm;

[0106] (3) After mixing and stirring 2% hydrophilic amorphous flowable powder nano-silica and anhydrous ethanol, a mixed solution of silane coupling agent VTES and water was added, the liquid-to-solid ratio of silane coupling agent VTES to nano-silica was 5:1 mL / g, and the ratio of silane coupling agent VTES to water was 1:2. The suspension was prepared by magnetic stirring at a speed of 200 r / min for 10 min, and then the suspension was ultrasonically dispersed for 30 min at a frequency of 40 KHz to obtain a nano-silica suspension. MSWIFA was weighed and placed in a microwave reactor together with the nano-silica suspension. The reaction time was 35 min, the reaction temperature was 65°C, and the microwave power was 350 W.

[0107] (4) Add the mixed solution obtained in (3) into the reactor, stir it magnetically, and introduce a gas containing CO2 into the reactor at a rate of 2 L / min, and continue the reaction for 2 h;

[0108] (5) mixing the mixed solution obtained after the carbonization in (4) with ordinary Portland cement, and then stirring in a cement mixer at a speed of 300 rpm for 5 minutes to obtain a slurry mixture;

[0109] (6) The slurry mixture is molded, vibrated, and placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 100%. After curing for 24 hours, the mold is removed. After the specimen is demolded, it is moved into a high-temperature steam curing chamber at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to 28 days to obtain a test block;

[0110] (7) The compressive strength of the test piece obtained by testing with a pressure testing machine was 44.8 MPa;

[0111] (8) The test block prepared in (5) was crushed until all of the test blocks passed through a 3 mm sieve, and then dried in a drying oven at 60 °C for 24 h;

[0112] (9) Deionized water was used as the leaching agent with a liquid-to-solid ratio of 10:1 (L / kg) and an amplitude of 40 mm. 2 g of solid sample was mixed into 20 mL of deionized water and then horizontally vibrated at 110 ± 10 times / min for 8 h. The mixture was allowed to stand for 16 h and finally filtered through a 0.45 μm membrane. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the concentration of heavy metals in the leachate.

[0113] Table 9 Comparative Example 1 Mixing Ratio

[0114]

[0115] Table 10 Heavy metal leaching concentrations of original waste incineration fly ash and final product of comparative example 1

[0116] Heavy Metal Elements Crμg / L Cuμg / L Znμg / L Cdμg / L Pbμg / L Raw fly ash 232.60 174.30 6.45 26.85 20.36 Comparative Example 1 15.31 13.12 1.18 2.22 2.31

[0117] Comparative Example 2

[0118] (1) Collect MSWIFA, sieve the waste incineration fly ash through a 0.075 mm square hole sieve, and take the waste incineration fly ash with a particle size less than 0.075 mm for subsequent use;

[0119] (2) Distilled water and waste incineration fly ash were mixed at a liquid-solid ratio of L / S=10:1, and magnetically stirred at a speed of 400 r / min for 20 min; the mixed solution of distilled water + waste incineration fly ash was separated from the distilled water by a suction filter to obtain solid waste incineration fly ash, the filter membrane used for suction filtration was a 0.45 μm filter membrane, and then dried at 48°C for 36 h, and then taken out after drying to constant mass, cooled to room temperature, and the product was sieved through a 625-mesh sieve to obtain waste incineration fly ash with a particle size of 0.020 mm;

[0120] (3) Ordinary Portland cement, waste incineration fly ash and distilled water were weighed and mixed, and then stirred in a cement mixer at a speed of 300 r / min for 5 minutes to obtain a slurry mixture;

[0121] (4) The slurry mixture is molded, vibrated, and placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 100%. After curing for 24 hours, the mold is removed. After the specimen is demolded, it is moved into a high-temperature steam curing chamber at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to 28 days to obtain a test block;

[0122] (5) The compressive strength of the test piece obtained by the pressure testing machine is 37.8 MPa;

[0123] (6) The test block prepared in (4) was crushed until all of the test blocks passed through a 3 mm sieve, and then dried in a drying oven at 60 °C for 24 h;

[0124] (7) Deionized water was used as the leaching agent with a liquid-to-solid ratio of 10:1 (L / kg) and an amplitude of 40 mm. 2 g of solid sample was mixed into 20 mL of deionized water and then horizontally vibrated at 110 ± 10 times / min for 8 h. The mixture was allowed to stand for 16 h and finally filtered through a 0.45 μm membrane. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the concentration of heavy metals in the leachate.

[0125] Table 11 Comparative Example 2 Mixing Ratio

[0126] Table 12 Heavy metal leaching concentrations of original waste incineration fly ash and final product of comparative example 2

[0127] Heavy Metal Elements Crμg / L Cuμg / L Znμg / L Cdμg / L Pbμg / L Raw fly ash 232.60 174.30 6.45 26.85 20.36 Comparative Example 2 99.24 88.14 4.29 13.04 11.32

[0128] Comparative Example 3

[0129] (1) Ordinary Portland cement and distilled water were weighed and mixed, and then stirred in a cement mixer at a speed of 400 r / min for 5 minutes to obtain a slurry mixture;

[0130] (2) The slurry mixture is molded, vibrated, and placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 100%. After curing for 24 hours, the mold is removed. After the specimen is demolded, it is moved into a high-temperature steam curing chamber at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to 28 days to obtain a test block;

[0131] (3) The compressive strength of the test block obtained by using a pressure testing machine is 42.6 MPa.

[0132] Table 13 Comparative Example 3 Mixing Ratio

[0133]

[0134] Comparative Example 4

[0135] (1) Collect MSWIFA, sieve the waste incineration fly ash through a 0.075 mm square hole sieve, and take the waste incineration fly ash with a particle size less than 0.075 mm for subsequent use;

[0136] (2) Distilled water and waste incineration fly ash were mixed at a liquid-solid ratio of L / S=10:1, and magnetically stirred at a speed of 400 r / min for 20 min; the mixed solution of distilled water + waste incineration fly ash was separated from the distilled water by a suction filter to obtain solid waste incineration fly ash, the filter membrane used for suction filtration was a 0.45 μm filter membrane, and then dried at 48°C for 36 h, and then taken out after drying to constant mass, cooled to room temperature, and the product was sieved through a 625-mesh sieve to obtain waste incineration fly ash with a particle size of 0.020 mm;

[0137] (3) Prepare 1% ethanolamine solution, perform ultrasonic oscillation, the oscillation frequency is 45 kHz, the oscillation power is 30 W, oscillate for 2 seconds and rest for 3 seconds, and cool after each oscillation for 20 minutes, and repeat this process 6 times;

[0138] (4) Weigh the ethanolamine solution, waste incineration fly ash and distilled water obtained in (3), mix them in proportion and add them into a reactor, stir them magnetically, and introduce a gas containing CO2 into the reactor at a rate of 2 L / min, and continue the reaction for 2 h;

[0139] (5) The mixed slurry obtained in (4), waste incineration fly ash and ordinary Portland cement are stirred in a cement mixer at a speed of 300 r / min for 5 minutes to obtain a slurry mixture;

[0140] (6) The slurry mixture is molded, vibrated, and placed in a constant temperature and humidity chamber at a temperature of 25°C and a humidity of 100%. After curing for 24 hours, the mold is removed. After the specimen is demolded, it is moved into a high-temperature steam curing chamber at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to 28 days to obtain a test block;

[0141] (7) The compressive strength of the test piece obtained by testing with a pressure testing machine is 43.5 MPa;

[0142] (8) The solidified product obtained in (5) was crushed until all of the solidified product passed through a 3 mm sieve, and then dried in a drying oven at 60° C. for 24 h;

[0143] (9) Deionized water was used as the leaching agent with a liquid-to-solid ratio of 10:1 (L / kg) and an amplitude of 40 mm. 2 g of solid sample was mixed into 20 mL of deionized water and then horizontally vibrated at 110 ± 10 times / min for 8 h. The mixture was allowed to stand for 16 h and finally filtered through a 0.45 μm membrane. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the concentration of heavy metals in the leachate.

[0144] Table 14 Comparative Example 4 Mixing Ratio

[0145]

[0146] Table 15 Heavy metal leaching concentrations of original waste incineration fly ash and final product of comparative example 4

[0147] Heavy Metal Elements Crμg / L Cuμg / L Znμg / L Cdμg / L Pbμg / L Raw fly ash 232.60 174.30 6.45 26.85 20.36 Comparative Example 4 16.11 13.41 1.28 2.21 2.04

[0148] It can be seen from the analysis and test results of each embodiment and comparative example that the solidified test block prepared by carbonization modification of MSWIFA using VTES and nano-silicon dioxide, ethanolamine and carbon dioxide gas has good compressive strength and relatively stable heavy metals. Compared with Examples 1-3, the results show that with the increase of nano-silicon dioxide content, the compressive strength of cement shows a trend of first increasing and then decreasing, indicating that there is an optimal range for nano-silicon dioxide. Compared with Comparative Example 2, Examples 1-3 show that carbonization significantly improves the mechanical properties of MSWIFA-containing cement paste, indicating that the carbonization process strengthens the volcanic ash activity of MSWIFA, and the carbonized modified MSWIFA plays a positive role in cement hydration reaction. The calcium carbonate particles produced by the carbonization reaction of carbon dioxide with hydrated calcium silicate and calcium hydroxide can fill pores and microcracks to improve its mechanical properties. At the same time, the heavy metal ions in the solution react with carbon dioxide to form insoluble carbonates. The heavy metal ions are stabilized inside because of chemical precipitation and physical encapsulation, making the heavy metals in the fly ash relatively stable. Compared with Example 4, the results of Example 2 show that the MSWIFA cement-based material with nano-silica has a stronger ability to consolidate heavy metals and improves its strength. This is because the higher specific surface area of ​​nano-silica can adsorb and consolidate heavy metals, and promote cement hydration as a nucleation site, generate more hydrated calcium silicate gel products, and fill the micropores and cracks in the hardened slurry to make the matrix denser. Compared with Example 4, the results of Example 2 show that after the nano-silica is modified with VTES, the nano-silica can better fill the pores, generate more hydrated calcium silicate gel products, and the matrix is ​​denser and the strength is improved, thereby more effectively encapsulating heavy metal ions. Compared with Example 1, the results of Example 2 show that the ethanolamine solution accelerates the carbonization reaction rate of the fly ash particle surface. Its alkaline environment not only promotes the hydration of calcium oxide to generate calcium hydroxide, and then reacts with carbon dioxide to generate calcium carbonate, but also promotes the formation of hydroxide or carbonate precipitation of heavy metal ions in fly ash.

Claims

1. A method for preparing low-carbon waste incineration fly ash (MSWIFA) cement-based materials by carbonization of modified nano-solutions, characterized in that: The method comprises the following raw materials: MSWIFA, vinyl triethoxysilane (VTES), nano silicon dioxide, ethanolamine, water and carbon dioxide gas; wherein VTES, nano silicon dioxide, ethanolamine and carbon dioxide gas are used in sequence to carbonize and modify MSWIFA.

2. The method according to claim 1, characterized in that The chemical composition of the MSWIFA satisfies 30-40% of CaO, 3%-8% of SiO2, and 1%-4% of MgO; the particle size of the MSWIFA satisfies D50=20-30 μm, and the particle size range is 10-50 μm.

3. The method according to claim 1, characterized in that The liquid-to-solid ratio of VTES to nano-silicon dioxide is 5:1-6:1 mL / g, and the ratio of VTES to water is 1:2-1:

3.

4. The method according to claim 3, characterized in that The hydrophilic amorphous flowable powder nano-silica with an average particle size of 20-30 nm is added to anhydrous ethanol and stirred, and then a mixed solution of VTES and water is added. After stirring, the suspension is subjected to ultrasonic dispersion treatment to obtain a VTES-modified nano-silica solution.

5. The method according to claim 1, characterized in that The ethanolamine is configured as a 1-2 wt % ethanolamine solution to participate in the modification of MSWIFA.

6. The method according to claim 1, characterized in that The introduction rate of carbon dioxide gas is 2-3L / min, the reaction pressure is 0.5-1MPa, the reaction time is 1-3h, the reaction temperature is 20-30°C, and the humidity is 50-80%; the carbon dioxide gas is a high-purity gas with a mass fraction of 99-99.9%.

7. The method according to claim 1, characterized in that The carbonized MSWIFA is mixed with ordinary Portland cement to improve the compressive strength of the cement base.

8. The method according to any one of claims 1 to 7, characterized in that: The steps include: S1. Sieve the waste incineration fly ash through a 0.075 mm square hole sieve, and take the waste incineration fly ash with a particle size of less than 0.075 mm for subsequent use; S2. Mix distilled water and waste incineration fly ash at a liquid-solid ratio of L / S=5-20:1, and stir magnetically at a speed of 300-500 r / min for 15-30 min; S3, using a suction filter to separate the distilled water from the mixed solution of distilled water + waste incineration fly ash to obtain solid waste incineration fly ash, using a 0.45 μm filter membrane for suction filtration, and then drying at 40-60° C. for 24-48 hours, taking out after drying to constant mass, cooling to room temperature, and sieving to obtain a homogeneous powder with a particle size range of 10-50 μm; S4, mixing and stirring the nano-silica and anhydrous ethanol to disperse the nano-silica in the anhydrous ethanol. Mixing and stirring the silane coupling agent vinyl triethoxysilane (VTES) and water to hydrolyze the VTES to obtain a VTES solution, pouring the VTES solution into the anhydrous ethanol solution of the nano-silica, and stirring to mix them to obtain a VTES-modified nano-silica solution; modifying the nano-silica by using VTES so that the nano-silica is uniformly dispersed in the material; S5, mixing the MSWIFA and VTES modified nano-silica solution to obtain a mixed slurry; S6, placing the mixed slurry in a water bath device, placing it in a microwave reactor, reaction time 30-40min, reaction temperature 60-70°C, microwave power 300-400W, start microwave reactor water bath heating; S7, prepare 1-2wt% ethanolamine solution, perform ultrasonic oscillation, the oscillation frequency is 40-50KHz, the oscillation power is 25-35W, oscillate for 2s and rest for 3s, and cool after each oscillation for 15-20min, and repeat 4-6 times; S8, placing the mixed slurry and the prepared ethanolamine solution in a reactor, heating and stirring in a water bath, introducing carbon dioxide gas into the reactor, adjusting the pressure and reaction time of the reactor, and performing a carbonization reaction; S9. The carbonized mixed slurry is mixed with ordinary Portland cement and stirred to obtain a slurry mixture, wherein the slurry mixture is a mixture of waste incineration fly ash and ordinary Portland cement mortar, wherein the waste incineration fly ash content is 30%. The slurry mixture is molded and vibrated, and demolded after curing for 24 hours under standard curing conditions. After demolding, the specimen is moved into a high-temperature steam curing box at a temperature of 90°C and a humidity of 100%. After curing for 48 hours, the specimen is moved into a standard curing room and cured to an age of 28 days to obtain a test block.

9. Use of the method according to any one of claims 1 to 8 in improving the compressive strength of cement-based materials and / or recycling MSWIFA.

Images