Preparation method of composite catalytic membrane based on fly ash mesoporous molecular sieve

Abstract

The invention discloses a preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash. The preparation method comprises the following steps: S1, preparing a mesoporous molecular sieve ceramic membrane; s2, preparing a Co-BiVO4 catalyst; s3, preparing a molecular sieve composite catalytic membrane; the molecular sieve composite catalytic membrane comprises a ceramic membrane substrate, a molecular sieve dispersed on the ceramic membrane substrate and a Co-BiVO4 catalyst dispersed on the molecular sieve, so that the catalyst with high specific surface area and high activity is loaded on the molecular sieve, the interception precision and the catalytic activity of the ceramic membrane are improved, and the self-cleaning effect of the ceramic membrane is realized; the defect that the ceramic membrane is easy to pollute is improved; secondly, a hydrothermal reaction is carried out in a ceramic membrane matrix and a molecular sieve precursor solution, so that the molecular sieve is uniformly and firmly loaded in internal apertures of the ceramic membrane matrix, and the light absorption intensity and the utilization rate of the catalyst are increased by modifying the catalyst, so that the sewage treatment efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a preparation method of a composite catalytic membrane based on fly ash mesoporous molecular sieve. Background Art

[0002] Inorganic ceramic membranes have been widely used in the field of water treatment, but the phenomenon of membrane fouling hinders their further development. Especially, the smaller the pore size, the more serious the membrane fouling phenomenon. It is necessary to provide a multifunctional membrane with high precision, large flux and anti-fouling to solve this problem. Summary of the Invention

[0003] In view of the above problems, the present invention designs a preparation method of a composite catalytic membrane based on fly ash mesoporous molecular sieve, including the following steps: S1: Prepare a mesoporous molecular sieve ceramic membrane; S11: Put fly ash into sodium hydroxide solution, cool it and then vacuum filter to obtain Al and Si extraction solution; S12: Prepare cetyltrimethylammonium bromide solution, stir it under water bath heating, add the cetyltrimethylammonium bromide solution into the Al and Si extraction solution and stir until no floccules are generated, and then adjust it to transparency with sulfuric acid; S13: Add ethyl acetate to the solution in S12 and stir to obtain a molecular sieve precursor solution, and carry out hydrothermal reaction on the molecular sieve precursor solution and the ceramic membrane substrate to obtain a molecular sieve ceramic membrane precursor; S14: Wash the molecular sieve ceramic membrane precursor with deionized water and ethanol respectively until it is neutral, and dry it to obtain a molecular sieve ceramic membrane preform;

[0004] S2: Prepare Co-BiVO4 catalyst; S21: Mix bismuth trioxide, vanadium pentoxide and ionized distilled water in proportion and stir to obtain solution one; S22: Add diethylenetriaminepentaacetic acid into solution one; S23: Add ammonia water to solution one to adjust the pH to obtain solution two, and add Co(NO3)2 to solution two and stir to obtain a catalyst precursor solution;

[0005] S3: Prepare a molecular sieve composite catalytic membrane; S31: Immerse the molecular sieve ceramic membrane preform into the catalyst precursor solution, carry out vacuum impregnation and then dry it to obtain a molecular sieve composite catalytic membrane precursor; S32: Calcinate and cool the molecular sieve composite catalytic membrane precursor to obtain a molecular sieve composite catalytic membrane;

[0006] The molecular sieve composite catalytic membrane includes a ceramic membrane matrix, molecular sieves dispersed on the ceramic membrane matrix, and Co-BiVO4 catalysts dispersed on the molecular sieves. The pore size of the molecular sieve is 7-9 nm, the particle size of the molecular sieve is 1-3 μm, the pore size of the ceramic membrane matrix is 30-50 nm, the specific surface area of the molecular sieve is 260-270 m 2 / g, and the particle size of the Co-BiVO4 catalyst is 0.3-1 μm.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: The catalyst attached to the molecular sieve can reach the nanoscale, with a large specific surface area and high catalytic efficiency. At the same time, through the nanoscale catalyst, while the number of cavities and electron pairs inside the instant catalyst is high, the recombination rate of cavities and electron pairs of all the nanoscale catalysts as a whole decreases, thus significantly improving the catalytic efficiency.

[0008] However, when preparing nanoscale catalysts in the molecular sieve, agglomeration is extremely likely to occur, resulting in a significant reduction in catalytic effect. In this application, after the molecular sieve is first dispersed on the ceramic membrane matrix, the catalyst is then dispersed on the molecular sieve, avoiding the problems of agglomeration and small specific surface area during the direct preparation of the molecular sieve, as well as the phenomenon of agglomeration when the molecular sieve and the catalyst are directly combined.

[0009] Thus, a catalyst with a high specific surface area and high activity is loaded on the molecular sieve, improving the rejection accuracy and catalytic activity of the ceramic membrane, thereby realizing the self-cleaning function of the ceramic membrane and improving the disadvantage that the ceramic membrane is easily contaminated. Secondly, through the hydrothermal reaction in the ceramic membrane matrix and the molecular sieve precursor solution, the molecular sieve is uniformly and firmly loaded in the internal pores of the ceramic membrane matrix. By modifying the catalyst, the absorption intensity and utilization rate of light by the catalyst are increased, thereby improving the treatment efficiency of sewage.

[0010] Further, the preparation method of the ceramic membrane substrate in S13: Mix high-aluminum fly ash, alumina, plastic clay, pore-forming agent, low-temperature binder, water, plasticizer, lubricant, water-reducing agent, and water-retaining agent in a mass ratio of 40-60:10-20:3-6:5-8:2-6:15-25:1.5-3:4-7:0.5-1:2-4, and extrude to form a ceramic membrane substrate green body. Sinter the ceramic membrane substrate green body. The sintering process includes heating from room temperature to 100-120°C at a heating rate of 9-11°C / min, heating from 100-120°C to 300-340°C at a heating rate of 6-7°C / min, heating from 300-340°C to 450-500°C at a heating rate of 4-5°C / min, and heating from 450-550°C to 1100-1300°C at a heating rate of 3-3.5°C / min. The pore-forming agent includes at least one of PMMA microspheres and silicon carbide powder, the low-temperature binder includes at least one of polyvinyl alcohol and carboxyethyl cellulose, the plasticizer includes polyethylene glycol, the lubricant includes sodium stearate, the water-reducing agent includes at least one of oleic acid, water glass, and sodium tripolyphosphate, and the water-retaining agent includes tung oil.

[0011] The beneficial effects of adopting the above further technical solution are as follows: By mixing various materials and extruding them into a formed ceramic membrane base body, sintering the ceramic membrane base body, when heated, part of the organic substances volatilize, and the remaining substances melt and crystallize to form a ceramic membrane base with large pore diameters and a large number of pores. When the temperature of the ceramic membrane base body in the green body rises from room temperature to 100 - 120 °C, the ceramic membrane base body is initially solidified. When the temperature rises from 100 - 120 °C to 300 - 340 °C, the organic substances volatilize. When the temperature rises from 300 - 340 °C to 450 - 500 °C, the organic substances completely volatilize, and the remaining substances melt and crystallize. When the temperature rises from 450 - 550 °C to 1100 - 1300 °C, a ceramic membrane base with large pore diameters and a large number of pores is formed, and then it is cooled to room temperature, and the ceramic membrane base is shaped.

[0012] Further, before the hydrothermal reaction of the ceramic membrane base body, it is soaked and left standing in a modification solution to obtain a modified ceramic membrane matrix, and the modified ceramic membrane matrix is placed in a molecular sieve precursor solution for hydrothermal reaction;

[0013] The preparation process of the modification solution is as follows: Sodium dodecylbenzenesulfonate and deionized water are mixed according to a mass ratio, and the mass ratio is 1 - 3:7 - 9. After mixing by mass ratio, a modification solution is obtained.

[0014] The beneficial effects of adopting the above further technical solution are as follows: By doping sodium dodecylbenzenesulfonate on the ceramic membrane matrix to modify the ceramic membrane matrix, when the molecular sieve combines with the ceramic membrane matrix, it is beneficial for the molecular sieve to disperse into the pore interior of the ceramic membrane matrix, avoiding the problem of blockage of the pore surface inside the ceramic membrane matrix caused by the aggregation of the molecular sieve when the molecular sieve combines with the ceramic membrane or the generated molecular sieve adhering to the surface of the ceramic membrane matrix, thereby avoiding the problem that the liquid to be treated cannot enter the pore interior of the ceramic membrane matrix during use, and thus avoiding the problem of reduced catalytic efficiency.

[0015] Further, the mass ratio of fly ash to sodium hydroxide solution in S11 is: 10:1, the concentration of sodium hydroxide is 1.5 - 2.5 mol / L, and the reaction is carried out at 120 - 130 °C for 0.9 - 1.1 h.

[0016] Further, the concentration of cetyltrimethylammonium bromide in the cetyltrimethylammonium bromide solution in water is 9 - 11%, stirred in a water bath at 25 °C - 35 °C for 9 - 11 min, the stirring speed is 295 - 305 rpm, the ratio of the cetyltrimethylammonium bromide solution added to the Al, Si extraction solution is 0.8 - 1.2:0.6 - 0.8 - 0.8 - 1.1, and sulfuric acid is 4.5 - 5.5 mol / L, and the pH is adjusted to 9.5 - 10.5.

[0017] Further, the ratio of ethyl acetate to the solution in S12 in S13 is 0.8 - 1.2:16 - 18 - 17 - 19. The ethyl acetate in S13 is rapidly stirred for 4 - 6 min. The temperature of the hydrothermal reaction is 85°C - 95°C, and it is treated for 23.5 - 24.5 h. The concentration of the sodium dialkylbenzenesulfonate solution is 1% - 5%. Then, it is calcined at 500 - 600°C for 4.5 - 5.5 h.

[0018] The beneficial effects of adopting the above further technical solution are as follows: Using fly ash to prepare molecular sieves reduces the raw material cost and realizes the rational utilization of solid waste, thereby preparing molecular sieves with a high specific surface area and porous channels, controlling the pore size of the ceramic membrane, enabling the pore size of the ceramic membrane separation layer to be 30 - 50 nm, successfully combining it with the support ceramic membrane, and preparing a high-precision separation membrane.

[0019] Further, the ratio of bismuth trioxide, vanadium pentoxide, and ionized distilled water in S21 is 0.8 - 1.2:4.8 - 5.2:9 - 11. The molar ratio of bismuth trioxide to vanadium pentoxide is 0.8 - 1.2:0.8 - 1.2, and the stirring time is 11.5 - 12.5 h;

[0020] In S22, the molar ratio of diethylenetriaminepentaacetic acid to solution one is DTPA:Bi:V = 2.8 - 3.2:0.8 - 1.2:0.8 - 1.2.

[0021] Further, the pH of solution two in S23 is 10 - 12. The molar percentage of solution two to Co(NO3)2 is 1% - 5%, and the stirring time at 75 - 85°C is 23.5 - 24.5 h.

[0022] Further, in S31, the molecular sieve ceramic membrane is immersed in the catalyst precursor solution. After vacuum impregnation for 9.5 - 10.5 min, it is dried at 75 - 85°C for 47.5 - 48.5 h.

[0023] Further, in S32, the molecular sieve composite catalytic membrane is calcined at 550 - 650°C for 3.5 - 4.5 h, and the heating rate is 4.5 - 5.5°C / min, and then it is cooled to room temperature.

[0024] The beneficial effects of adopting the above further technical solution are as follows: Using BiVO4 as a photocatalyst is because it has visible light response. By doping with Co to modify the catalyst, the separation efficiency of electrons and holes is improved, the number of electron-hole pairs inside the catalyst particles is increased, and the light absorption intensity and catalytic efficiency of the catalyst are enhanced;

[0025] After simultaneous modification, the catalyst loaded on the ceramic membrane molecular sieve will generate a heterojunction under high-temperature sintering, making the Ce-Ti bimetallic catalyst more closely combined, and the synergistic effect can improve the catalytic activity of the photocatalyst. Description of the Drawings

[0026] Figure 1 This is a flowchart of the preparation method of the composite catalytic membrane based on fly ash mesoporous molecular sieve according to the embodiment of the present invention. Detailed Embodiments

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0028] Example 1:

[0029] This example provides a preparation method of a composite catalytic membrane based on fly ash mesoporous molecular sieve, including the following steps:

[0030] S1: Prepare a mesoporous molecular sieve ceramic membrane; S11: Put fly ash into a sodium hydroxide solution, and after cooling, vacuum filter to obtain an Al and Si extraction solution; in S11, the mass ratio of fly ash to the sodium hydroxide solution is 10:1, the concentration of sodium hydroxide is 2 mol / L, and the reaction is carried out at 110 °C for 1 h;

[0031] S12: Prepare a cetyltrimethylammonium bromide solution, stir it under water bath heating, add the cetyltrimethylammonium bromide solution to the Al and Si extraction solution and stir until no floccules are produced, then add sulfuric acid to adjust it to transparency; the concentration of cetyltrimethylammonium bromide in the cetyltrimethylammonium bromide solution in water is 10%, stir for 10 min under water bath heating at 25°C - 35°C, the stirring speed is 300 rpm, the ratio of the cetyltrimethylammonium bromide solution added to the Al and Si extraction solution is 1:0.75, the sulfuric acid is 5 mol / L, and adjust the pH = 10; S13: Add ethyl acetate to the S12 solution and stir to obtain a molecular sieve precursor solution, and carry out a hydrothermal reaction on the molecular sieve precursor solution and the ceramic membrane substrate to obtain a molecular sieve ceramic membrane precursor; the preparation method of the ceramic membrane substrate in S13: Mix high-aluminum fly ash, alumina, plastic clay, pore-forming agent, low-temperature binder, water, plasticizer, lubricant, water-reducing agent, and water-retaining agent in a mass ratio of 50:15:4.5:6.5:4:20:2.3:5.5:0.75:3.5, extrude to form a ceramic membrane substrate blank, sinter the ceramic membrane substrate blank, the sintering process includes raising the temperature from room temperature to 110°C, the heating rate is 10°C / min, raising the temperature from 110°C to 320°C, the heating rate is 6.5°C / min, raising the temperature from 320°C to 475°C, the heating speed is 4.5°C / min, raising the temperature from 500°C - to 1200°C, the heating rate is 3.25°C / min, the pore-forming agent is PMMA microspheres, the low-temperature binder is polyvinyl alcohol, the plasticizer is polyethylene glycol, the lubricant is sodium stearate, the water-reducing agent is oleic acid, and the water-retaining agent is tung oil. S14: Wash the molecular sieve ceramic membrane precursor with deionized water and ethanol respectively until neutral, and obtain a molecular sieve ceramic membrane preform after drying; by mixing a variety of materials and extruding them into shape, a ceramic membrane substrate blank is formed, sinter the ceramic membrane substrate blank, when heating, part of the organic matter volatilizes, and the rest of the substances melt and crystallize to form a ceramic membrane substrate with large pore size and a large number of pores. When the ceramic membrane substrate blank is raised from room temperature to 110°C, the ceramic membrane substrate is initially solidified. When the temperature is raised from 110°C to 320°C, the organic matter volatilizes. When the temperature is raised from 320°C to 475°C, the organic matter volatilizes completely, and the rest of the substances melt and crystallize. When the temperature is raised from 505°C - to 1200°C, a ceramic membrane substrate with large pore size and a large number of pores is formed, and then it is cooled to room temperature, and the ceramic membrane substrate is shaped; the ratio of ethyl acetate to the S12 solution in S13 is 1:17 - 18, the ethyl acetate in S13 is rapidly stirred for 5 min, the temperature of the hydrothermal reaction is 90°C, treated for 24 h, and then calcined at 550°C for 5 hours. Using fly ash to prepare molecular sieves reduces the raw material cost, realizes the rational utilization of solid waste, thereby prepares molecular sieves with high specific surface area and porous channels, thereby controlling the pore size of the ceramic membrane, and can realize the pore size of the ceramic membrane separation layer to be 40 nm, successfully combines it with the support ceramic membrane, and prepares a high-precision separation membrane;

[0032] S2: Prepare the Co-BiVO4 catalyst; S21: Mix bismuth trioxide, vanadium pentoxide and ionized distilled water in proportion and stir to obtain Solution 1. The ratio of bismuth trioxide, vanadium pentoxide and ionized distilled water in S21 is 1:5:10, the molar ratio of bismuth trioxide to vanadium pentoxide is 1:1, and the stirring time is 12 h; S22: Add diethylenetriaminepentaacetic acid to Solution 1. The molar ratio of diethylenetriaminepentaacetic acid to Solution 1 in S22 is DTPA:Bi:V = 3:1:1; S23: Add ammonia water to Solution 1 to adjust the pH to obtain Solution 2, and add Co(NO3)2 to Solution 2 and stir to obtain the catalyst precursor solution. The pH of Solution 2 in S23 is 11, the molar percentage of Solution 2 to Co(NO3)2 is 3%, and the stirring time is 24 h at 80 °C.

[0033] S3: Prepare the molecular sieve composite catalytic membrane; S31: Immerse the molecular sieve ceramic membrane preform into the catalyst precursor solution, perform vacuum impregnation and then dry to obtain the molecular sieve composite catalytic membrane precursor. In S31, immerse the molecular sieve ceramic membrane into the catalyst precursor solution, perform vacuum impregnation for 10 min, and then dry at 80 °C for 48 h; S32: Calcinate and cool the molecular sieve composite catalytic membrane precursor to obtain the molecular sieve composite catalytic membrane. In S32, the molecular sieve composite catalytic membrane is calcined at 600 °C for 4 hours, the heating rate is 5 °C / min, and then cooled to room temperature. The molecular sieve composite catalytic membrane includes a ceramic membrane matrix, molecular sieves dispersed on the ceramic membrane matrix, and Co-BiVO4 catalysts dispersed on the molecular sieves. The pore size of the molecular sieve is 8 nm, the particle size of the molecular sieve is 2 μm, the pore size of the ceramic membrane matrix is 40 nm, the specific surface area of the molecular sieve is 265 m 2 / g, and the particle size of the Co-BiVO4 catalyst is 0.65 μm. By using BiVO4 as the photocatalyst, it is because it has visible light response. By doping with Co to modify the catalyst, the separation efficiency of electrons and holes is improved, the number of electron-hole pairs inside the catalyst particles is increased, and the light absorption intensity and catalytic efficiency of the catalyst are increased; while improving, the modified catalyst is loaded on the ceramic membrane molecular sieve, and a heterojunction will be generated under high-temperature sintering, making the Ce-Ti bimetallic catalyst combine more closely, and the synergistic effect can improve the catalytic activity of the photocatalyst;

[0034] It is realized that the catalyst attached to the molecular sieve can reach the nanoscale, with a large specific surface area and high catalytic efficiency. At the same time, through the nanoscale catalyst, while the number of holes and electron pairs inside the instant catalyst is high, the recombination rate of holes and electron pairs of all the nanoscale catalysts as a whole is reduced, thereby significantly improving the catalytic efficiency;

[0035] However, when preparing nanoscale catalysts inside molecular sieves, agglomeration is extremely likely to occur, resulting in a significant reduction in catalytic performance. In this application, by first dispersing the molecular sieve on the ceramic membrane matrix and then dispersing the catalyst on the molecular sieve, the problems of agglomeration and small specific surface area during the direct preparation of the molecular sieve are avoided, as well as the phenomenon of agglomeration caused by the direct combination of the molecular sieve and the catalyst.

[0036] Thereby, a catalyst with a high specific surface area and high activity is loaded on the molecular sieve, improving the rejection accuracy and catalytic activity of the ceramic membrane, and thus realizing the self-cleaning function of the ceramic membrane and improving the disadvantage that the ceramic membrane is easily contaminated. Secondly, through hydrothermal reaction in the ceramic membrane matrix and the molecular sieve precursor solution, the molecular sieve is uniformly and firmly loaded in the internal pores of the ceramic membrane matrix. By modifying the catalyst, the absorption intensity and utilization rate of light by the catalyst are increased, thereby improving the treatment efficiency of sewage.

[0037] Example 2:

[0038] The same content as in Example 1 will not be elaborated here; the different solutions from Example 1 are as follows:

[0039] This example provides a preparation method of a composite catalytic membrane based on fly ash mesoporous molecular sieve.

[0040] In S11, the mass ratio of fly ash to sodium hydroxide solution is 10.1:1.1, the concentration of sodium hydroxide is 2.4 mol / L, and the reaction is carried out at 129 °C for 1.09 h; S12: The concentration of cetyltrimethylammonium bromide in the cetyltrimethylammonium bromide solution in water is 10.9%, stirred for 10.9 min under a water bath at 34 °C, the stirring speed is 304 rpm, the ratio of the cetyltrimethylammonium bromide solution added to the Al, Si extraction solution is 1.1:0.89, sulfuric acid is 5.4 mol / L, and the pH is adjusted to 10.4; S13: Preparation method of the ceramic membrane substrate: Mix high-aluminum fly ash, alumina, plastic clay, pore-forming agent, low-temperature binder, water, plasticizer, lubricant, water reducer, water-retaining agent in a mass ratio of 59:19:5.9:7.9:5.9:24:2.9:6.9:0.9:3.9, extrude to form a ceramic membrane substrate green body, sinter the ceramic membrane substrate green body, the sintering process includes rising from room temperature to 119 °C, the heating rate is 10.9 °C / min, rising from 119 °C to 339 °C, the heating rate is 6.9 °C / min, rising from 339 °C to 499 °C, the heating rate is 4.9 °C / min, rising from 549 °C to 1290 °C, the heating rate is 3.4 °C / min, the pore-forming agent is PMMA microspheres, the low-temperature binder is polyvinyl alcohol, the plasticizer is polyethylene glycol, the lubricant is sodium stearate, the water reducer is oleic acid, and the water-retaining agent is tung oil; S14: When the ceramic membrane substrate green body rises from room temperature to 119 °C, the ceramic membrane substrate is initially solidified, when rising from 119 °C to 339 °C, organic substances volatilize, when rising from 339 °C to 499 °C, organic substances volatilize completely, and the remaining substances melt and crystallize, when rising from 549 °C to 1299 °C, a ceramic membrane substrate with large and numerous pores is formed, and then cooled to room temperature, and the ceramic membrane substrate is shaped; The ratio of ethyl acetate to the S12 solution in S13 is 1.1:17.9 - 18.9, the ethyl acetate in S13 is rapidly stirred for 5.9 min, the temperature of the hydrothermal reaction is 94 °C, treated for 24.4 h, and then calcined at 599 °C for 5.4 hours, and the pore diameter of the ceramic membrane separation layer can reach 49 nm;

[0041] Before the hydrothermal reaction of the ceramic membrane substrate, it is soaked and left standing in a modification solution to obtain a modified ceramic membrane matrix. The modified ceramic membrane matrix is placed in a molecular sieve precursor solution for hydrothermal reaction. The preparation process of the modification solution is as follows: Sodium dodecylbenzenesulfonate and deionized water are mixed according to a mass ratio of 2.9:8.9. After mixing in this mass ratio, a modification solution is obtained. By doping sodium dodecylbenzenesulfonate on the ceramic membrane matrix, the ceramic membrane matrix is modified. When the molecular sieve combines with the ceramic membrane matrix, it is beneficial for the molecular sieve to disperse into the pores of the ceramic membrane matrix, avoiding the problem of blockage of the internal pore surface of the ceramic membrane matrix caused by the aggregation of the molecular sieve when the molecular sieve combines with the ceramic membrane or the generated molecular sieve adhering to the surface of the ceramic membrane matrix. Thus, the problem that the liquid to be treated cannot enter the pores of the ceramic membrane matrix during use is avoided, and therefore the problem of reduced catalytic efficiency is avoided.

[0042] In S21, the ratio of bismuth trioxide, vanadium pentoxide and ionized distilled water is 1.1:5.1:10.9, the molar ratio of bismuth trioxide and vanadium pentoxide is 1.1:1.1, and the stirring time is 12.4 h; in S22, the molar ratio of diethylenetriaminepentaacetic acid to Solution 1 is DTPA:Bi:V = 3.1:1.1:1.1; in S23, the pH of Solution 2 is 11.9, the molar percentage of Solution 2 and Co(NO3)2 is 4%, and the stirring time at 84 °C is 24.4 h;

[0043] In S31, the molecular sieve ceramic membrane is immersed in the catalyst precursor solution. After vacuum impregnation for 10.4 min, it is dried at 84 °C for 48.4 h; in S32, the molecular sieve composite catalytic membrane is calcined at 649 °C for 4.4 h, the heating rate is 5.4 °C / min, and then it is cooled to room temperature. The pore diameter of the molecular sieve is 8.9 nm, the particle size of the molecular sieve is 2.9 μm, the pore diameter of the ceramic membrane matrix is 49 nm, the specific surface area of the molecular sieve is 269 m 2 / g, and the particle size of the Co-BiVO4 catalyst is 0.9 μm;

[0044] Example Three:

[0045] The content that is the same as that in Example One in this example will not be elaborated; the different solutions from Example One in this example are as follows:

[0046] This example provides a preparation method of a fly ash mesoporous molecular sieve composite catalytic membrane,

[0047] In S11, the mass ratio of fly ash to sodium hydroxide solution is 9.9:0.9, the concentration of sodium hydroxide is 1.6 mol / L, and the reaction is carried out at 121 °C for 0.91 h; S12: The concentration of cetyltrimethylammonium bromide in the cetyltrimethylammonium bromide solution in water is 9.1%, stirred for 9.1 min under a water bath at 26 °C, the stirring speed is 296 rpm, the ratio of the cetyltrimethylammonium bromide solution added to the Al, Si extraction solution is 0.9:0.61, sulfuric acid is 4.6 mol / L, and the pH is adjusted to 9.6; S13: Preparation method of the ceramic membrane substrate: Mix high-aluminum fly ash, alumina, plastic clay, pore-forming agent, low-temperature binder, water, plasticizer, lubricant, water reducing agent, water retaining agent in a mass ratio of 41:11:3.1:5.1:2.1:16:1.6:4.1:0.6:2.1, extrude to form a ceramic membrane substrate green body, sinter the ceramic membrane substrate green body, the sintering process includes rising from room temperature to 101 °C, the heating rate is 9.1 °C / min, rising from 101 °C to 301 °C, the heating rate is 6.1 °C / min, rising from 301 °C to 451 °C, the heating speed is 4.1 °C / min, rising from 451 °C to 1101 °C, the heating speed is 3.1 °C / min, the pore-forming agent is PMMA microspheres, the low-temperature binder is polyvinyl alcohol, the plasticizer is polyethylene glycol, the lubricant is sodium stearate, the water reducing agent is oleic acid, and the water retaining agent is tung oil; S14: When the ceramic membrane substrate green body rises from room temperature to 101 °C, the ceramic membrane substrate begins to solidify preliminarily. When rising from 101 °C to 301 °C, organic substances volatilize. When rising from 301 °C to 451 °C, the organic substances volatilize completely, and the remaining substances melt and crystallize. When rising from 451 °C to 1101 °C, a ceramic membrane substrate with large pore diameter and large quantity is formed, and then cooled to room temperature, and the ceramic membrane substrate is shaped; The ratio of ethyl acetate to the S12 solution in S13 is 0.9:16.1 - 17.1. The ethyl acetate in S13 is rapidly stirred for 4.1 min, the temperature of the hydrothermal reaction is 86 °C, treated for 23.6 h, and then calcined at 501 °C for 4.6 hours, and the pore diameter of the ceramic membrane separation layer can reach 31 nm;

[0048] Before the hydrothermal reaction, the ceramic membrane substrate is soaked and left standing in a modification solution to obtain a modified ceramic membrane matrix. The modified ceramic membrane matrix is placed in a molecular sieve precursor solution for hydrothermal reaction. The preparation process of the modification solution is as follows: Sodium dodecylbenzenesulfonate and deionized water are mixed according to a mass ratio of 1.1:7.1 to obtain a modification solution. By doping sodium dodecylbenzenesulfonate on the ceramic membrane matrix, the ceramic membrane matrix is modified. When the molecular sieve binds to the ceramic membrane matrix, it is beneficial for the molecular sieve to disperse into the pores of the ceramic membrane matrix, avoiding the problem of blockage of the inner pore surface of the ceramic membrane matrix caused by the aggregation of the molecular sieve when the molecular sieve binds to the ceramic membrane or the generated molecular sieve adhering to the surface of the ceramic membrane matrix, thereby avoiding the problem that the liquid to be treated cannot enter the pores of the ceramic membrane matrix during use, and thus avoiding the problem of reduced catalytic efficiency.

[0049] In S21, the ratio of bismuth trioxide, vanadium pentoxide and ionized distilled water is 0.8 - 1.2:4.8 - 5.2:9 - 11, the molar ratio of bismuth trioxide and vanadium pentoxide is 0.9:0.9, and the stirring time is 11.6 h; in S22, the molar ratio of diethylenetriaminepentaacetic acid to Solution 1 is DTPA:Bi:V = 2.9:0.9:0.9; in S23, the pH of Solution 2 is 10.1, the molar percentage of Solution 2 and Co(NO3)2 is 1%, and the stirring time at 76 °C is 23.6 h;

[0050] In S31, the molecular sieve ceramic membrane is immersed in the catalyst precursor solution. After vacuum impregnation for 9.6 min, it is dried at 76 °C for 47.6 h; in S32, the molecular sieve composite catalytic membrane is calcined at 551 °C for 3.6 hours, the heating rate is 4.6 °C / min, and then it is cooled to room temperature. The pore diameter of the molecular sieve is 7.1 nm, the particle size of the molecular sieve is 1.1 μm, the pore diameter of the ceramic membrane matrix is 31 nm, the specific surface area of the molecular sieve is 261 m2 / g, and the particle size of the Co - BiVO4 catalyst is 0.4 μm;

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash, characterized in that, It includes the following steps: S1: Prepare a mesoporous molecular sieve ceramic membrane; S11: Put fly ash into a sodium hydroxide solution, cool it, and then perform vacuum filtration to obtain an Al and Si extraction solution; S12: Prepare a cetyltrimethylammonium bromide solution, stir it under a water bath, add the cetyltrimethylammonium bromide solution to the Al and Si extraction solution and stir until no floccules are produced, and then add sulfuric acid to adjust it to transparency; S13: Add ethyl acetate to the solution in S12 and stir to obtain a molecular sieve precursor solution, and perform a hydrothermal reaction on the molecular sieve precursor solution and a ceramic membrane substrate to obtain a molecular sieve ceramic membrane precursor; S14: Wash the molecular sieve ceramic membrane precursor with deionized water and ethanol until it is neutral, and dry it to obtain a molecular sieve ceramic membrane preform; S2: Prepare a Co-BiVO4 catalyst; S21: Mix bismuth trioxide, vanadium pentoxide, and ionized distilled water in proportion and stir to obtain Solution 1; S22: Add diethylenetriaminepentaacetic acid to Solution 1; S23: Add ammonia water to Solution 1 to adjust the pH to obtain Solution 2, and add Co(NO3)2 to Solution 2 and stir to obtain a catalyst precursor solution; S3: Prepare a molecular sieve composite catalytic membrane; S31: Immerse the molecular sieve ceramic membrane preform in the catalyst precursor solution, perform vacuum impregnation and then dry it to obtain a molecular sieve composite catalytic membrane precursor; S32: Calcine and cool the molecular sieve composite catalytic membrane precursor to obtain a molecular sieve composite catalytic membrane; The molecular sieve composite catalytic membrane includes a ceramic membrane matrix, molecular sieves dispersed on the ceramic membrane matrix, and Co-BiVO4 catalysts dispersed on the molecular sieves. The pore size of the molecular sieves is 7-9 nm, the particle size of the molecular sieves is 1-3 μm, the pore size of the ceramic membrane matrix is 30-50 nm, the specific surface area of the molecular sieves is 260-270 m 2 / g, and the particle size of the Co-BiVO4 catalysts is 0.3-1 μm.

2. The preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash according to claim 1, characterized in that: The preparation method of the ceramic membrane substrate in S13: Mix high-aluminum fly ash, alumina, plastic clay, pore-forming agent, low-temperature binder, water, plasticizer, lubricant, water reducer, and water retention agent in a mass ratio of 40-60:10-20:3-6:5-8:2-6:15-25:1.5-3:4-7:0.5-1:2-4, extrude and sinter them to obtain a ceramic membrane substrate blank. The sintering process of the ceramic membrane substrate blank includes heating from room temperature to 100-120°C at a heating rate of 9-11°C / min, heating from 100-120°C to 300-340°C at a heating rate of 6-7°C / min, heating from 300-340°C to 450-500°C at a heating rate of 4-5°C / min, and heating from 450-550°C to 1100-1300°C at a heating rate of 3-3.5°C / min.

3. The preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash according to claim 2, characterized in that: Before the hydrothermal reaction of the ceramic membrane substrate, soak and stand it in a modification solution to obtain a modified ceramic membrane matrix, and put the modified ceramic membrane matrix into the molecular sieve precursor solution for hydrothermal reaction; The preparation process of the modification solution: Mix sodium dodecylbenzenesulfonate and deionized water in a mass ratio, and the mass ratio is 1-3:7-9. Mix them by mass ratio to obtain a modification solution.

4. The preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash according to claim 1, characterized in that: In S11, the mass ratio of fly ash to the sodium hydroxide solution is 9.8-10.2:0.8-1.2, the concentration of sodium hydroxide is 1.5-2.5 mol / L, and the reaction is carried out at 120-130°C for 0.9-1.1 h.

5. The preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash according to claim 1, characterized in that: The concentration of cetyltrimethylammonium bromide in the cetyltrimethylammonium bromide solution in water is 9-11%, stirred for 9-11 min under water bath heating at 25°C-35°C, the stirring speed is 295-305 rpm, and the ratio of the cetyltrimethylammonium bromide solution to the Al, Si extraction solution is 0.8-1.2:0.6-0.9, sulfuric acid is 4.5-5.5 mol / L, and the pH is adjusted to 9.5-10.

5.

6. A preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash, as claimed in claim 1, wherein: In S13, the ratio of ethyl acetate to the S12 solution is 0.8-1.2:16-18-17-19. The ethyl acetate in S13 is rapidly stirred for 4-6 min, the temperature of the hydrothermal reaction is 85°C-95°C, treated for 23.5-24.5 h, the concentration of the dialkylbenzenesulfonate solution is 1%-5%, and then calcined at 500-600°C for 4.5-5.5 h.

7. A preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash, as claimed in claim 1, characterized in that: In S21, the ratio of bismuth trioxide, vanadium pentoxide and ionized distilled water is 0.8-1.2:4.8-5.2:9-11, the molar ratio of bismuth trioxide to vanadium pentoxide is 0.8-1.2:0.8-1.2, and the stirring time is 11.5-12.5 h; In S22, the molar ratio of diethylenetriaminepentaacetic acid to solution 1 is DTPA:Bi:V = 2.8-3.2:0.8-1.2:0.8-1.

2.

8. A preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash, as described in claim 1, characterized in that: In S23, the pH of solution 2 is 10-12, the molar percentage of solution 2 to Co(NO3)2 is 1%-5%, and stirred at 75-85°C for 23.5-24.5 h.

9. The preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash according to claim 1, characterized in that: In S31, the molecular sieve ceramic membrane is immersed in the catalyst precursor solution. After vacuum impregnation for 9.5-10.5 min, it is dried at 75-85°C for 47.5-48.5 h.

10. The preparation method of a mesoporous molecular sieve composite catalytic membrane based on fly ash according to claim 1, characterized in that: In S32, the molecular sieve composite catalytic membrane is calcined at 550-650°C for 3.5-4.5 h, the heating rate is 4.5-5.5°C / min, and then cooled to room temperature.

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