Stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst as well as preparation and application of stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst as well as preparation and application thereof. Biomass powder and silicon dioxide powder are added into magnesium-containing bimetallic citric acid sol, stirring, mixing and granulation are performed, next-step pyrolysis sintering molding is performed in an inert atmosphere, silicon dioxide particles on the surface are etched with a sodium hydroxide solution after cooling, and the stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst is prepared. The preparation process of the magnesium-containing bimetal oxide millimeter-sphere ozone catalyst is simple and controllable, the magnesium-containing bimetal oxide millimeter-sphere ozone catalyst has excellent catalytic ozone oxidation activity and can be used for strengthening ozone oxidation of refractory pollutants including antibiotics, metal-organic complexes and the like, and the millimeter-scale catalyst is easy to recycle and use and has good application prospects. The method is suitable for advanced treatment of industrial wastewater and industrial park wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and more specifically, relates to a hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst and its preparation and application. Background Art

[0002] The wastewater generated by chemical industrial parks and electroplating industrial parks contains a large number of refractory organic pollutants, such as antibiotics, metal-organic complexes, etc., which are difficult to remove by conventional physical and chemical methods, thus posing a threat to the ecological environment, causing troubles for the discharge of wastewater in compliance with standards or the reuse of reclaimed water, and are the difficulties in industrial wastewater treatment. Catalytic ozone oxidation technology is an advanced oxidation technology that catalyzes the decomposition of ozone to produce highly oxidizing hydroxyl radicals and other active oxygen species at room temperature and pressure. It can efficiently degrade highly stable and refractory organic pollutants that are difficult to oxidize with ozone alone, thereby achieving the purpose of maximizing the removal of organic pollutants and achieving efficient utilization of ozone. In catalytic ozone oxidation technology, the development and application of cheap, stable and efficient catalysts are the key and core factors that determine the water treatment efficiency of this technology. Currently reported environmentally friendly transition metal oxides or alkaline earth metal oxides such as MnO2, Fe2O3, MgO, etc. have ozone oxidation catalytic activity, and after forming magnesium-containing bimetallic oxides such as MgMnO3 and MgFe2O4, they show even better ozone catalytic oxidation activity. However, the magnesium-containing bimetallic oxides currently studied are mostly concentrated on powder catalysts. Although they can efficiently catalyze ozone to produce highly oxidizing active oxygen species such as hydroxyl radicals, they are not conducive to continuous use and recycling in actual use, and are easily lost to cause secondary pollution, limiting their large-scale application. In contrast, macroscopic millimeter-scale spherical catalysts are easy to separate and recycle, and the macroporous-mesoporous stepped porous structure is also conducive to the diffusion and mass transfer of larger molecular pollutants such as antibiotics and metal-organic complexes, and provides a large number of catalytic active sites. Therefore, the development of stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalysts with high catalytic activity and conducive to large-scale application can be used in various wastewater treatment reactor forms such as fixed beds and fluidized beds, and has broad application prospects. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the problems that the existing high-activity powder catalysts are difficult to use and recycle continuously, are not conducive to large-scale application, and have difficulty in mass transfer of large molecular pollutants, and provide a stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst.

[0004] The purpose of the present invention is to provide a method for preparing a graded porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst.

[0005] Another object of the present invention is to provide a step-by-step porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst for use in catalyzing ozone degradation of organic pollutants.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst specifically comprises the following steps:

[0008] S1. Add biomass powder and silica powder to the bimetallic citric acid sol containing magnesium, add a small amount of water as appropriate, stir and mix to granulate, and obtain precursor particles a;

[0009] S2. The precursor particles a described in S1 are pyrolyzed and sintered in one step under nitrogen protection, and then cooled to obtain precursor particles b;

[0010] S3. Take the precursor particles b described in S2 and place them in an etching solution for 4 to 20 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst;

[0011] In the bimetallic citric acid (C6H8O7) sol containing magnesium, the other metal may be manganese or iron, and the precursors of magnesium, manganese and iron are magnesium nitrate, manganese nitrate or iron nitrate, respectively, with a molar ratio of Mg 2+ :Mn 2+ :C6H8O7=1:1:2orMg 2+ :Fe 3+ :C6H8O7=1:2:8, the dosage of the precursor can fluctuate up and down by 10%.

[0012] In the present invention, the magnesium-containing bimetallic citric acid (C6H8O7) sol is a precursor of the magnesium-containing bimetallic oxide. During the pyrolysis process, the citric acid decomposes to generate a large amount of gas to form pores, and the magnesium-containing bimetallic oxide with a rich mesoporous structure can be obtained; at the same time, the biomass is a precursor of biochar, and the biochar generated after pyrolysis can reduce the interface contact between the active component and the silicon dioxide, thereby reducing the electron-withdrawing passivation effect of the silicon dioxide during the catalytic reaction, and at the same time can also improve the pollutant enrichment performance of the catalyst and the electron transmission performance of the catalyst; and SiO2 has the dual functional characteristics of an excipient and a template agent. During the pyrolysis process, the silicon dioxide has a molding effect, so that the catalyst maintains the shape of the precursor millimeter ball after high-temperature pyrolysis. At the same time, after subsequent etching treatment, the micron-sized silicon dioxide particles on the surface of the millimeter ball part are removed, so that the catalyst surface has rich micron pores.

[0013] In the present invention, the bimetallic citric acid sol containing magnesium (calculated according to the dry gel), biomass powder, and silica powder are mixed in a mass ratio of 66-200:12.5-25:65-80. If there is too much bimetallic citric acid sol containing magnesium, the catalyst is not easy to form, and if there is too little, the catalytic activity of the catalyst is reduced due to the reduction of active components; if there is too much biomass powder, on the one hand, the active sites of the catalyst may be wrapped and the catalytic activity may be reduced, and on the other hand, the catalyst is not easy to form, and if there is too little biomass powder, the electron-withdrawing passivation effect of silica during the catalytic reaction cannot be reduced, and the role of pollutant enrichment and assisting the catalyst in conducting electrons cannot be played; if there is too much silica, the catalytic activity is reduced, and if there is too little silica, the catalyst collapses and cannot be formed and is insufficient to play the role of template pore formation.

[0014] In the present invention, the particle size of the silica powder is 10 to 80 μm. If the particle size is too small, the active component, magnesium-containing bimetallic oxide, will have excessive interface contact with the silica, and even silicate will be formed at the interface, which will reduce the catalytic activity. At the same time, the template pore size will be too small, which is not conducive to mass transfer and is more expensive. If the particle size is too large, the shaping effect will be poor, resulting in the catalyst having too low mechanical strength or even being unable to be formed. In addition, the template pore size is too large, which is not conducive to exposing more catalytic active sites and will also prolong the subsequent etching time.

[0015] In the present invention, the particle size of the precursor particles a is 3 to 12 mm. If the particle size is too small, the formed spherical catalyst is difficult to use continuously and recycle; if the particle size is too large, the exposed active surface of the catalyst is reduced, the catalyst dosage is increased, and the cost is increased.

[0016] In the present invention, the pyrolysis temperature is 600-900°C. If the pyrolysis temperature is too low, it is impossible to form a highly active magnesium-containing bimetallic compound, porous carbon, and solidified millimeter-sized particles. If the pyrolysis temperature is too high, the active components are easily sintered and more low-activity silicates are easily formed, thereby reducing the catalytic activity of the catalyst and consuming more energy for pyrolysis.

[0017] In the present invention, the pyrolysis time is 1 to 4 hours. If the pyrolysis time is too short, the highly active magnesium-containing bimetallic compound cannot be completely formed and fixed into a fixed shape. If the pyrolysis time is too long, the active components are easily sintered and more low-activity silicates are easily formed, thereby reducing the overall catalytic activity of the catalyst and consuming more energy.

[0018] Preferably, the other metal in the magnesium-containing bimetallic citric acid sol may be manganese or iron.

[0019] Furthermore, in the preparation method of the stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst of the present invention, the magnesium-containing bimetallic citric acid sol (calculated as dry gel), biomass powder, and silica powder are mixed in a mass ratio of 66-200:12.5-25:65-80.

[0020] Furthermore, in the method for preparing the hierarchical porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst of the present invention, the particle size of the silica powder is 10 to 80 μm; more preferably, the particle size of the silica powder is 40 to 60 μm.

[0021] Preferably, the particle size of the precursor particles a is 3 to 12 mm.

[0022] Furthermore, the heating rate of the pyrolysis is 3-10°C / min. Within this heating rate range, the citric acid sol and the biomass are not likely to decompose too quickly, resulting in structural collapse.

[0023] Furthermore, the pyrolysis time is 1 to 4 hours. Within this range, the hierarchical porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst prepared by pyrolysis has better catalytic performance.

[0024] Furthermore, the precursor particles b are added to a 3-10M sodium hydroxide solution and etched for 4-20 hours, filtered, washed with water until neutral, and dried to obtain a stepped porous magnesium-containing bimetallic oxide millimeter sphere ozone catalyst.

[0025] Furthermore, in the method for preparing the hierarchical porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst of the present invention, the magnesium-containing bimetallic citric acid sol can be purchased commercially or prepared according to the method of the present invention.

[0026] For reference, the present invention provides a method for preparing a bimetallic citric acid sol containing magnesium:

[0027] S11: mixing magnesium nitrate and manganese nitrate in a molar ratio of 0.9 to 1.1:0.9 to 1.1, and then adding a citric acid complexing agent and water in a molar ratio of magnesium nitrate to citric acid of 1:1.8 to 2.2, dissolving to form a uniform solution;

[0028] S12: Add ammonia water dropwise to the uniform solution obtained in S1 and stir, and react at 60-80° C. for 0.5-2 h to form a light pink sol.

[0029] The present invention also protects the step-by-step porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst prepared by the preparation method.

[0030] The present invention protects the application of the stepped porous magnesium-containing bimetallic oxide millimeter ball as an ozone catalyst.

[0031] The hierarchical porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst of the present invention can catalyze ozone to degrade refractory organic pollutants in water.

[0032] Specifically, in the embodiment of the present invention, the step-by-step porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in the embodiment can catalyze the ozone oxidation reaction and effectively degrade antibiotic pollutants or metal organic complexes. More specifically, sulfamethoxazole (SMZ) commonly found in pharmaceutical wastewater and ethylenediaminetetraacetic acid complexed nickel (EDTA-Ni) commonly found in electroplating wastewater are used as pollutant degradation objects, and the step-by-step porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst of the present invention is used for catalysis, and the final SMZ removal rate is more than 89%, and the total nickel concentration of EDTA-Ni after oxidation and decomposition precipitation is less than 0.1 mg / L, reaching the emission standard (<0.1 mg / L) of Table 3 of the "Emission Standard of Electroplating Pollutants" (GB21900-2008), and the catalytic performance of the catalyst is good.

[0033] Additionally, the present invention protects the application of the hierarchical porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst in the field of organic pollutant degradation.

[0034] Furthermore, the organic pollutants include but are not limited to antibiotics, nickel-containing organic complexes and other difficult-to-degrade organic substances.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention adopts a one-step pyrolysis molding method. The bimetallic citric acid polymer releases a large amount of gas during the pyrolysis process to form pores and form a highly active magnesium-containing bimetallic oxide with a rich mesoporous structure. The bimetallic can create a slightly alkaline environment suitable for ozone oxidation reaction and also has bimetallic synergistic catalytic activity. Therefore, it can efficiently degrade organic pollutants in a wide pH range without adjusting the pH of the water.

[0037] (2) The raw materials of the preparation method of the present invention are widely available, either industrial products or biomass waste, which are cheap and environmentally friendly, and the pyrolysis step is simple.

[0038] (3) In the preparation method described in the present invention, SiO2 has the dual functional properties of an excipient and a template. During the pyrolysis process, silica has a molding effect, so that the catalyst maintains the shape of the precursor millimeter ball after high-temperature pyrolysis. At the same time, after subsequent etching treatment, the micron-sized silica particles on the surface of the millimeter ball are removed, so that the catalyst surface has abundant micron pores.

[0039] (4) The addition of biomass in the preparation method of the present invention forms biochar during pyrolysis, which can appropriately reduce the direct contact between the active components and silica, thereby reducing the electron-withdrawing passivation effect of silica during the catalytic reaction, and can also improve the pollutant enrichment performance of the catalyst and the electron transport performance of the catalyst.

[0040] (5) Compared with the existing powder materials, the stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst of the present invention has the advantages of flexible usage scenarios and easy recycling and reuse; and the stepped porous structure is conducive to the full exposure of active sites and the mass transfer of reactants, and the catalyst activity is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a photograph of the stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0043] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0044] Example 1

[0045] The bimetallic citric acid sol containing magnesium in this embodiment is specifically prepared by:

[0046] S11: According to the raw material molar ratio of magnesium nitrate: manganese nitrate: citric acid = 1:1:2, 10.737g (30mmol) of 50% manganese nitrate solution, 7.692g (30mmol) of magnesium nitrate hexahydrate, and 12.608g (60mmol) of citric acid monohydrate were weighed and placed in a 1000mL beaker. 200mL of pure water was added to dissolve all the solids to form a uniform solution.

[0047] S12. Add 25% (w / w) ammonia water dropwise to the above solution, stir, adjust the pH value to 5.0-6.0, place the beaker in an 80°C water bath and stir for 1 hour to form a light pink sol.

[0048] After the above sol is dried, if it is heat treated at 450℃ for 2h, 3.840g MgMnO3 can be obtained.

[0049] A hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0050] S1. 9.6 g of sawdust powder and 30.72 g of silica powder having a particle size of 50 μm were added to the magnesium-containing bimetallic citric acid sol prepared in S12, a small amount of water was added, the mixture was stirred and granulated, and the particle diameter was controlled to be 10 mm to obtain a precursor particle a;

[0051] S2. The precursor particles a described in S1 are heated to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 900°C for 1h, and then cooled to obtain precursor particles b;

[0052] S3. Take the precursor particles b described in S2 and place them in a 10M sodium hydroxide etching solution for 10 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst.

[0053] The hierarchical porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst obtained above is as follows Figure 1 As shown, in the catalyst, the mass percentages of magnesium bimetallic oxide, carbon, and silicon dioxide are 10%, 10%, and 80%, respectively.

[0054] Catalyst performance evaluation: The simulated pollutant is sulfamethoxazole (SMZ) as the object (but the organic pollutants that can be treated are not limited to sulfamethoxazole), 50.0mL, 20.0mg / L sulfamethoxazole wastewater, 4.0g of the stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in Example 1 are added to the customized reactor, and the SMZ removal rate is tested to evaluate the ozone catalytic oxidation activity of the catalyst. The ozone concentration is 2.0mg / L and the flow rate is 100mL / min. The ozone that does not participate in the reaction at the reactor outlet is quenched with potassium iodide solution. After 20 minutes of reaction, the sample is taken, the ozone in the solution is blown off with N2 and filtered, and its concentration is tested by HPLC. The SMZ removal rate reaches 89.5%.

[0055] The simulated pollutant was selected as EDTA-Ni organic complex (but the organic pollutants that can be treated are not limited to EDTA-Ni organic complex). 50.0 mL of 5.0 mg / L Ni 2+ (Ni 2+ Wastewater containing EDTA-Ni complex) was added, 4.0g of the step-by-step porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in Example 1, and ozone was introduced into the bottom of the reactor at a concentration of 3.0mg / L and a flow rate of 100mL / min. The ozone that did not participate in the reaction at the reactor outlet was quenched with potassium iodide solution, and the reaction was sampled after 45min. After the ozone in the solution was stripped with N2, sodium dimethyldithiocarbamate (DTC) was used for precipitation to remove the Ni freed from the broken complex. 2+ Then, the total nickel concentration remaining in the solution (mainly undissociated Ni2+ Or EDTA-Ni organic complex that has not been degraded by the reaction), and the total nickel concentration remaining in the solution after complex breaking and precipitation was used to evaluate its removal effect. The results showed that the total nickel concentration remaining in the solution was 0.08 mg / L by ICP measurement, which reached the emission standard in Table 3 of the "Emission Standard of Pollutants for Electroplating" (GB21900-2008) (<0.1 mg / L).

[0056] Example 2

[0057] The bimetallic citric acid sol containing magnesium in this embodiment is prepared in the same manner as in Example 1.

[0058] A hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0059] S1. 1.60 g of sawdust powder and 8.32 g of silica powder having a particle size of 10 μm were added to the prepared bimetallic citric acid sol containing magnesium, and the mixture was stirred and granulated, and the particle diameter was controlled to be 10 mm to obtain a precursor particle a;

[0060] S2. The precursor particles a described in S1 are heated to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 900°C for 1h, and then cooled to obtain precursor particles b;

[0061] S3. Take the precursor particles b described in S2 and place them in a 10M sodium hydroxide etching solution for 10 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter sphere ozone catalyst.

[0062] The catalyst contains magnesium bimetallic oxide, carbon and silicon dioxide in percentages by mass: 30%, 5% and 65% respectively.

[0063] Catalyst performance evaluation: The simulated pollutant is sulfamethoxazole (SMZ) as the object (but the organic pollutants that can be treated are not limited to sulfamethoxazole), 50.0mL, 20.0mg / L sulfamethoxazole wastewater, 4.0g of the stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in Example 2 are added to the customized reactor, and the SMZ removal rate is tested to evaluate the ozone catalytic oxidation activity of the catalyst. The ozone concentration is 2.0mg / L and the flow rate is 100mL / min. The ozone that does not participate in the reaction at the reactor outlet is quenched with potassium iodide solution. After 20 minutes of reaction, the sample is taken, the ozone in the solution is blown off with N2 and filtered, and its concentration is tested by HPLC. The SMZ removal rate reaches 92.3%.

[0064] Example 3

[0065] The bimetallic citric acid sol containing magnesium in this embodiment is prepared in the same manner as in Example 1.

[0066] A hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0067] S1. Add 9.6 g of sawdust powder and 30.72 g of silica powder having a particle size of 50 μm to the prepared bimetallic citric acid sol containing magnesium, add a small amount of water, stir and mix to form granules, and control the particle diameter to 10 mm to obtain precursor particles a;

[0068] S2. The precursor particles a described in S1 are heated to 600°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 600°C for 4 hours, and then cooled to obtain precursor particles b;

[0069] S3. Take the precursor particles b described in S2 and place them in a 10M sodium hydroxide solution for etching for 10 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst.

[0070] The catalyst contains magnesium bimetallic oxide, carbon and silicon dioxide in percentages by weight: 10%, 10% and 80% respectively.

[0071] Catalyst performance evaluation: EDTA-Ni organic complex was selected as the simulated pollutant (but the organic pollutants that can be treated are not limited to EDTA-Ni organic complex). 50.0mL containing 5.0mg / LNi was added to the custom reactor. 2+ (Ni 2+ The wastewater was prepared by mixing 4.0 g of the step-by-step porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst prepared in Example 3, and ozone was introduced into the bottom of the reactor at a concentration of 3.0 mg / L and a flow rate of 100 mL / min. The ozone that did not participate in the reaction at the reactor outlet was quenched with potassium iodide solution, and the reaction was performed after 45 min. After the ozone in the solution was stripped with N2, sodium dimethyldithiocarbamate (DTC) was used for precipitation to remove the free Ni from the broken complex. 2+ Then, the total nickel concentration remaining in the solution (mainly undissociated Ni 2+ Or EDTA-Ni organic complex that has not been degraded by the reaction), and the total nickel concentration remaining in the solution after complex breaking and precipitation was used to evaluate its removal effect. The results showed that the total nickel concentration remaining in the solution was 0.05 mg / L by ICP measurement, which reached the emission standard in Table 3 of the "Emission Standard of Pollutants for Electroplating" (GB21900-2008) (<0.1 mg / L).

[0072] Example 4

[0073] The bimetallic citric acid sol containing magnesium in this embodiment is prepared in the same manner as in Example 1.

[0074] A hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0075] S1. Add 9.6 g of sawdust powder and 30.72 g of silica powder having a particle size of 10 μm to the bimetallic citric acid sol containing magnesium, add a small amount of water, stir and mix to form granules, and control the particle diameter to 10 mm to obtain precursor particles a;

[0076] S2. The precursor particles a described in S1 are heated to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 900°C for 1h, and then cooled to obtain precursor particles b;

[0077] S3. Take the precursor particles b described in S2 and place them in a 5M sodium hydroxide etching solution for 4 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst.

[0078] The catalyst contains magnesium bimetallic oxide, carbon and silicon dioxide in percentages by weight: 10%, 10% and 80% respectively.

[0079] Catalyst performance evaluation: EDTA-Ni organic complex was selected as the simulated pollutant (but the organic pollutants that can be treated are not limited to EDTA-Ni organic complex). 50.0mL containing 5.0mg / LNi was added to the custom reactor. 2+ (Ni 2+ Wastewater containing EDTA-Ni complex) was added, 4.0g of the step-by-step porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in Example 4, and ozone was introduced into the bottom of the reactor at a concentration of 3.0mg / L and a flow rate of 100mL / min. The ozone that did not participate in the reaction at the reactor outlet was quenched with potassium iodide solution, and the reaction was sampled after 45min. After the ozone in the solution was stripped with N2, sodium dimethyldithiocarbamate (DTC) was used for precipitation to remove the free Ni from the broken complex. 2+ Then, the total nickel concentration remaining in the solution (mainly undissociated Ni 2+ Or EDTA-Ni organic complex that has not been degraded by the reaction), and the total nickel concentration remaining in the solution after complex breaking and precipitation was used to evaluate its removal effect. The results showed that the total nickel concentration remaining in the solution was 0.06 mg / L by ICP measurement, which reached the emission standard in Table 3 of the "Emission Standard of Pollutants for Electroplating" (GB21900-2008) (<0.1 mg / L).

[0080] Example 5

[0081] The bimetallic citric acid sol containing magnesium in this embodiment is prepared in the same manner as in Example 1.

[0082] A hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0083] S1. Add 9.6 g of sawdust powder and 30.72 g of silica powder with a particle size of 10 μm to the bimetallic citric acid wet sol containing magnesium, add a small amount of water, stir and mix to granulate, and control the particle diameter to 3 mm to obtain precursor particles a;

[0084] S2. The precursor particles a described in S1 are heated to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 900°C for 1h, and then cooled to obtain precursor particles b;

[0085] S3. Take the precursor particles b described in S2 and place them in a 3M sodium hydroxide etching solution for 4 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter sphere ozone catalyst.

[0086] The catalyst contains magnesium bimetallic oxide, carbon and silicon dioxide in percentages by weight: 10%, 10% and 80% respectively.

[0087] Catalyst performance evaluation: The simulated pollutant is sulfamethoxazole (SMZ) as the object (but the organic pollutants that can be treated are not limited to sulfamethoxazole), 50.0mL, 20.0mg / L sulfamethoxazole wastewater, 4.0g of the stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in Example 5 are added to the customized reactor, and the SMZ removal rate is tested to evaluate the ozone catalytic oxidation activity of the catalyst. The ozone concentration is 2.0mg / L and the flow rate is 100mL / min. The ozone that does not participate in the reaction at the reactor outlet is quenched with potassium iodide solution. After 20 minutes of reaction, the sample is taken, the ozone in the solution is blown off with N2 and filtered, and its concentration is tested by HPLC. The SMZ removal rate reaches 94.5%.

[0088] Example 6

[0089] The bimetallic citric acid sol containing magnesium in this embodiment is prepared in the same manner as in Example 1.

[0090] A hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0091] S1. Add 9.6 g of flour and 30.72 g of silica powder with a particle size of 50 μm to the bimetallic citric acid sol containing magnesium, add a small amount of water, stir and mix to granulate, and control the particle diameter to 10 mm to obtain precursor particles a;

[0092] S2. The precursor particles a described in S1 are heated to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 900°C for 1h, and then cooled to obtain precursor particles b;

[0093] S3. Take the precursor particles b described in S2 and place them in a 10M sodium hydroxide etching solution for 10 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter sphere ozone catalyst.

[0094] The catalyst contains magnesium bimetallic oxide, carbon and silicon dioxide in percentages by weight: 10%, 10% and 80% respectively.

[0095] Catalyst performance evaluation: EDTA-Ni organic complex was selected as the simulated pollutant (but the organic pollutants that can be treated are not limited to EDTA-Ni organic complex). 50.0mL containing 5.0mg / LNi was added to the custom reactor. 2+ (Ni 2+ The wastewater was prepared by mixing 4.0 g of the step-by-step porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst prepared in Example 6, and ozone was introduced into the bottom of the reactor at a concentration of 3.0 mg / L and a flow rate of 100 mL / min. The ozone that did not participate in the reaction at the reactor outlet was quenched with potassium iodide solution, and the reaction was performed after 45 min. After the ozone in the solution was stripped with N2, sodium dimethyldithiocarbamate (DTC) was used for precipitation to remove the free Ni from the broken complex. 2+ Then, the total nickel concentration remaining in the solution (mainly undissociated Ni 2+ Or EDTA-Ni organic complex that has not been degraded by the reaction), and the total nickel concentration remaining in the solution after complex breaking and precipitation was used to evaluate its removal effect. The results showed that the total nickel concentration remaining in the solution was 0.07 mg / L by ICP measurement, which reached the emission standard in Table 3 of the "Emission Standard of Pollutants for Electroplating" (GB21900-2008) (<0.1 mg / L).

[0096] Comparative Example 1

[0097] Compared with Example 1, the monolithic ozone catalyst of Comparative Example 1 does not contain biomass, and the rest of the preparation methods are the same.

[0098] The bimetallic citric acid sol containing magnesium in this embodiment is prepared in the same manner as in Example 1.

[0099] A hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0100] S1. Add 30.72 g of silica powder having a particle size of 50 μm to the bimetallic citric acid sol containing magnesium, stir and mix to form granules, add a small amount of water, and control the particle diameter to 10 mm to obtain precursor particles a;

[0101] S2. The precursor particles a described in S1 are heated to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 900°C for 1h, and then cooled to obtain precursor particles b;

[0102] S3. Take the precursor particles b described in S2 and place them in a 10M sodium hydroxide etching solution for 10 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst.

[0103] Catalyst performance evaluation: The simulated pollutant is sulfamethoxazole (SMZ) as the object (but the organic pollutants that can be treated are not limited to sulfamethoxazole), 50.0mL, 20.0mg / L sulfamethoxazole wastewater, 4.0g of the stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in Comparative Example 1 are added to the customized reactor, and the SMZ removal rate is tested to evaluate the ozone catalytic oxidation activity of the catalyst. The ozone concentration is 2.0mg / L and the flow rate is 100mL / min. The ozone that does not participate in the reaction at the reactor outlet is quenched with potassium iodide solution, and the sample is taken after 20min of reaction. The ozone in the solution is blown off with N2 and filtered. The concentration is tested by HPLC, and the SMZ removal rate reaches 82.8%.

[0104] The simulated pollutant was selected as EDTA-Ni organic complex (but the organic pollutants that can be treated are not limited to EDTA-Ni organic complex). 50.0 mL of 5.0 mg / L Ni 2+ (Ni 2+ Wastewater containing EDTA-Ni complex) and 4.0 g of the step-by-step porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in Example 1 were added, and ozone was introduced into the bottom of the reactor at a concentration of 3.0 mg / L and a flow rate of 100 mL / min. The ozone that did not participate in the reaction at the outlet of the reactor was quenched with potassium iodide solution, and the sample was taken after 45 minutes of reaction; after the ozone in the solution was stripped with N2, sodium dimethyldithiocarbamate (DTC) was used for precipitation to remove the free Ni from the broken complex. 2+ Then, the total nickel concentration remaining in the solution (mainly undissociated Ni 2+ Or EDTA-Ni organic complex that has not been degraded by the reaction), and the removal effect was evaluated by the total nickel concentration remaining in the solution after complex breaking and precipitation. The results showed that the total nickel concentration remaining in the solution was 0.86 mg / L by ICP measurement, which did not meet the emission standards in Table 3 of the "Emission Standards for Electroplating Pollutants" (GB21900-2008) (<0.1 mg / L).

[0105] Compared with Example 1, the stepped porous magnesium-containing metal oxide millimeter-sphere ozone catalyst prepared in this comparative example does not add biomass powder, and the obtained catalyst contains no biocarbon component. Because the electron-withdrawing passivation effect of silica cannot be reduced, and there is no enhanced pollutant enrichment effect and electron-conducting effect, the catalytic efficiency is significantly reduced.

[0106] Comparative Example 2

[0107] Compared with Example 1, the ozone catalyst of Comparative Example 2 only contains a magnesium precursor when preparing the citric acid wet sol, and the rest of the preparation method is the same.

[0108] The magnesium-containing citric acid sol of the present embodiment is specifically prepared by the following method:

[0109] S11: According to the raw material molar ratio of magnesium nitrate: citric acid = 1:1, 7.692 g (30 mmol) of magnesium nitrate hexahydrate and 6.304 g (30 mmol) of citric acid monohydrate were weighed and placed in a 1000 mL beaker. 200 mL of pure water was added to dissolve all the solids to form a uniform solution.

[0110] S12. Add 25% (w / w) ammonia water dropwise to the above solution, stir, adjust the pH value to 5.0-6.0, place the beaker in an 80°C water bath and stir for 1 hour to form a sol.

[0111] A hierarchical porous magnesium-containing metal oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0112] S1. 9.6 g of sawdust powder and 30.72 g of silica powder having a particle size of 50 μm were added to the magnesium-containing bimetallic citric acid sol prepared in S12, a small amount of water was added, the mixture was stirred and granulated, and the particle diameter was controlled to be 10 mm to obtain a precursor particle a;

[0113] S2. The precursor particles a described in S1 are heated to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 900°C for 1h, and then cooled to obtain precursor particles b;

[0114] S3. Take the precursor particles b described in S2 and place them in a 10M sodium hydroxide etching solution for 10 hours, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing metal oxide millimeter sphere ozone catalyst.

[0115] Catalyst performance evaluation: The simulated pollutant is sulfamethoxazole (SMZ) as the object (but the organic pollutants that can be treated are not limited to sulfamethoxazole), 50.0mL, 20.0mg / L sulfamethoxazole wastewater, 4.0g of the step-by-step porous magnesium-containing metal oxide millimeter ball ozone catalyst prepared in Example 2 are added to the customized reactor, and the SMZ removal rate is tested to evaluate the ozone catalytic oxidation activity of the catalyst. The ozone concentration is 2.0mg / L and the flow rate is 100mL / min. The ozone that does not participate in the reaction at the reactor outlet is quenched with potassium iodide solution, and the sample is taken after 20min of reaction. The ozone in the solution is blown off with N2 and filtered. The concentration is tested by HPLC, and the SMZ removal rate reaches 73.8%.

[0116] Compared with Example 1, the step-by-step porous magnesium-containing metal oxide millimeter-sphere ozone catalyst prepared in this comparative example did not add another metal manganese precursor, resulting in a significant decrease in catalytic efficiency.

[0117] Comparative Example 3

[0118] Compared with Example 1, the ozone catalyst of Comparative Example 3 only contains a manganese precursor when preparing the citric acid wet sol, and the rest of the preparation method is the same.

[0119] The manganese-containing citric acid sol of this embodiment is specifically prepared by:

[0120] S11: According to the raw material molar ratio of manganese nitrate: citric acid = 1:1, 10.737 g (30 mmol) of 50% manganese nitrate solution and 6.304 g (30 mmol) of citric acid monohydrate were weighed and placed in a 1000 mL beaker. 200 mL of pure water was added to dissolve all the solids to form a uniform solution.

[0121] S12. Add 25% (w / w) ammonia water dropwise to the above solution, stir, adjust the pH value to 5.0-6.0, place the beaker in an 80°C water bath and stir for 1 hour to form a sol.

[0122] A hierarchical porous manganese-containing metal oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0123] S1. 9.6 g of sawdust powder and 30.72 g of silica powder having a particle size of 50 μm were added to the manganese-containing citric acid wet sol prepared in S12, a small amount of water was added, the mixture was stirred and granulated, and the particle diameter was controlled to be 10 mm to obtain a precursor particle a;

[0124] S2. The precursor particles a described in S1 are heated to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyzed at 900°C for 1h, and then cooled to obtain precursor particles b;

[0125] S3. Take the precursor particles b described in S2 and place them in a 10M sodium hydroxide etching solution for 10 hours, filter, wash with water until neutral, and dry to obtain a stepped porous manganese-containing metal oxide millimeter sphere ozone catalyst.

[0126] Catalyst performance evaluation: EDTA-Ni organic complex was selected as the simulated pollutant (but the organic pollutants that can be treated are not limited to EDTA-Ni organic complex). 50.0mL containing 5.0mg / LNi was added to the custom reactor. 2+ (Ni 2+ Wastewater containing EDTA-Ni complex) was prepared, 4.0g of the step-by-step porous manganese-containing bimetallic oxide millimeter ball ozone catalyst prepared in Comparative Example 3, and ozone was introduced into the bottom of the reactor at a concentration of 3.0mg / L and a flow rate of 100mL / min. The ozone that did not participate in the reaction at the reactor outlet was quenched with potassium iodide solution, and the reaction was sampled after 45min; after the ozone in the solution was stripped with N2, sodium dimethyldithiocarbamate (DTC) was used for precipitation to remove the free Ni from the broken complex. 2+ Then, the total nickel concentration remaining in the solution (mainly undissociated Ni 2+ Or EDTA-Ni organic complex that has not been degraded by the reaction), and the total nickel concentration remaining in the solution after complex breaking and precipitation was used to evaluate its removal effect. The results showed that the total nickel concentration remaining in the solution was 2.32 mg / L by ICP measurement, which did not meet the emission standards in Table 3 of the "Emission Standards for Electroplating Pollutants" (GB21900-2008) (<0.1 mg / L).

[0127] Compared with Example 1, the step-by-step porous manganese-containing metal oxide millimeter-sphere ozone catalyst prepared in this comparative example does not add a metal magnesium precursor, resulting in a significant decrease in catalytic efficiency.

[0128] Comparative Example 4

[0129] Compared with Example 1, the ozone catalyst of Comparative Example 4 is not subjected to etching treatment, and the rest of the preparation methods are the same.

[0130] The bimetallic citric acid sol containing magnesium in this embodiment is specifically prepared by:

[0131] S11: According to the raw material molar ratio of magnesium nitrate: manganese nitrate: citric acid = 1:1:2, 10.737g (30mmol) of 50% manganese nitrate solution, 7.692g (30mmol) of magnesium nitrate hexahydrate, and 12.608g (60mmol) of citric acid monohydrate were weighed and placed in a 1000mL beaker. 200mL of pure water was added to dissolve all the solids to form a uniform solution.

[0132] S12. Add 25% (w / w) ammonia water dropwise to the above solution, stir, adjust the pH value to 5.0-6.0, place the beaker in an 80°C water bath and stir for 1 hour to form a light pink sol.

[0133] After the above sol is dried, if it is heat treated at 450℃ for 2h, 3.840g MgMnO3 can be obtained.

[0134] A hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, the preparation process is as follows:

[0135] S1. 9.6 g of sawdust powder and 30.72 g of silica powder having a particle size of 50 μm were added to the magnesium-containing bimetallic citric acid sol prepared in S12, a small amount of water was added, the mixture was stirred and granulated, and the particle diameter was controlled to be 10 mm to obtain a precursor particle a;

[0136] S2. Take the precursor particles a described in S1, and heat them to 900°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyze them at 900°C for 1 hour. After cooling, no more etching treatment is performed to obtain a stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst.

[0137] Catalyst performance evaluation: EDTA-Ni organic complex was selected as the simulated pollutant (but the organic pollutants that can be treated are not limited to EDTA-Ni organic complex). 50.0mL containing 5.0mg / LNi was added to the custom reactor. 2+ (Ni 2+ Wastewater (in the form of EDTA-Ni complex), 4.0g of the stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst prepared in Comparative Example 4, and ozone was introduced into the bottom of the reactor at the same time. The concentration of ozone was 3.0mg / L and the flow rate was 100mL / min. The ozone that did not participate in the reaction at the outlet of the reactor was quenched with potassium iodide solution, and the sample was taken after 45min of reaction; after the ozone in the solution was stripped with N2, sodium dimethyldithiocarbamate (DTC) was used for precipitation to remove the free Ni from the broken complex. 2+ Then, the total nickel concentration remaining in the solution (mainly undissociated Ni 2+ Or EDTA-Ni organic complex that has not been degraded by the reaction), and the total nickel concentration remaining in the solution after complex breaking and precipitation was used to evaluate its removal effect. The results showed that the total nickel concentration remaining in the solution was 2.68 mg / L by ICP measurement, which did not meet the emission standards in Table 3 of the "Emission Standards for Electroplating Pollutants" (GB21900-2008) (<0.1 mg / L).

[0138] Compared with Example 1, the stepped porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst prepared in this comparative example was not subjected to etching treatment, and no microporous structure was formed on the surface, thereby reducing the exposure of catalytic active sites and mass transfer, resulting in a significant decrease in catalytic efficiency.

[0139] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a hierarchical porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst, characterized in that: The specific steps include: S1. Add biomass powder and silica powder to the bimetallic citric acid sol containing magnesium, add a small amount of water as appropriate, stir and mix to granulate, and obtain precursor particles a; S2. The precursor particles a described in S1 are pyrolyzed and sintered in one step under nitrogen protection, and then cooled to obtain precursor particles b; S3. Take the precursor particles b described in S2 and place them in an etching solution for 4 to 20 h, filter, wash with water until neutral, and dry to obtain a stepped porous magnesium-containing bimetallic oxide millimeter ball ozone catalyst; The magnesium-containing bimetallic citric acid ( ) sol, the other metal can be manganese or iron, and the precursors of magnesium, manganese and iron are magnesium nitrate, manganese nitrate or iron nitrate, respectively, with a molar ratio of or The dosage of precursor can fluctuate up and down by 10%.

2. The preparation method according to claim 1, characterized in that: The other metal in the magnesium-containing bimetallic citric acid sol may be manganese or iron.

3. The preparation method according to claim 1, characterized in that: The biomass is one or more of flour, starch, rice flour, chitosan, wheat bran, rice husk, bean dregs, leaves, straw, sawdust powder and the like.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the magnesium-containing bimetallic citric acid sol (calculated based on dry gel), biomass powder, and silicon dioxide powder is 66-200: 12.5-25: 65-80.

5. The preparation method according to claim 1, characterized in that: The particle size of silica powder is 10~80 µm.

6. The preparation method according to claim 1, characterized in that: The particle size of the precursor particles a is 3-12 mm.

7. The preparation method according to claim 1, characterized in that: The pyrolysis heating rate is 3-10 °C / min.

8. The preparation method according to claim 1, characterized in that: The pyrolysis temperature is 600-900°C.

9. The preparation method according to claim 1, characterized in that: The pyrolysis time is 1 to 4 h.

10. The preparation method according to claim 1, characterized in that: The etching solution is a 3-10 M sodium hydroxide solution.

11. The hierarchical porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst prepared by the preparation method according to any one of claims 1 to 9.

12. Use of the hierarchical porous magnesium-containing bimetallic oxide millimeter-sphere ozone catalyst according to claim 10 in catalytic ozone degradation of organic pollutants.

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