Preparation method and application of metal catalyst-loaded aerogel

Abstract

The application discloses a preparation method of a metal catalyst aerogel, which comprises four steps of preparing a bimetallic framework, preparing a precursor solution, preparing an aerogel through an ice template method and modifying the aerogel. The application uses marine biomass material sodium alginate and single-layer MXene as a matrix material to prepare an aerogel with a unidirectional structure, and the aerogel has a large porosity and a specific surface area, and can obviously improve the catalytic activity of a bimetallic catalyst. Through the low-temperature calcination method, the carboxyl groups on the surface of the sodium alginate are subjected to decarboxylation, and the recycling stability of the aerogel catalyst in water is effectively improved. Compared with existing aerogel catalysts, the material has more excellent catalytic activity and recycling stability.

Description

Technical Field

[0001] This invention relates to water treatment catalysts, and more particularly to a method for preparing and applying a supported metal catalyst aerogel. Background Technology

[0002] When untreated dye wastewater is discharged into aquatic environments, the organic matter in it consumes dissolved oxygen, leading to a decrease in dissolved oxygen concentration. Furthermore, the color of the dye itself reduces the light transmittance of the water, thus affecting the growth of aquatic life. Dye macromolecules can also decompose or react with other chemicals in the water, releasing toxic substances that also harm aquatic life and the aquatic environment. Since the raw materials for dye production generally contain organic compounds such as benzene, naphthalene, and phenols, as well as heavy metal ions, these toxic substances are inevitably present in dye wastewater and are difficult to degrade naturally.

[0003] Currently, the main methods for removing organic dyes from water include physical, biological, and chemical methods. However, common methods such as physical adsorption, anaerobic digestion, and photocatalytic oxidation suffer from low degradation efficiency, poor cycle stability, and difficulty in secondary recovery.

[0004] Advanced oxidation techniques based on sulfate radicals hold promise as an ideal method for the rapid degradation of organic dyes due to their high redox potential, short half-life, and stable system. Metal catalysts are the core component in activating PMS for the degradation of organic dyes; however, metal particles are prone to aggregation during the reaction, leading to reduced catalytic efficiency. Therefore, selecting a suitable support material is crucial. Aerogels, with their high porosity and specific surface area, are beneficial for dye adsorption and are widely used as supports for metals. However, existing aerogel supports suffer from poor cycling stability. Summary of the Invention

[0005] To address the problem of poor stability of existing metal catalysts for the catalytic degradation of organic fuels, this invention provides a method for preparing a supported metal catalyst aerogel, comprising the following steps:

[0006] 1) Fabrication of bimetallic framework

[0007] Soluble Ni salt or soluble Cu salt and soluble Co salt are added to methanol, stirred evenly, and then 2-methylimidazole is added. After ultrasonic dispersion, the mixture is stirred again to form a bimetallic ZIF. After stirring, the mixture is heated in a reaction vessel, and the reactants are centrifuged to obtain a solid product. After drying, the product is placed in a high-temperature furnace, heated under nitrogen protection, kept at the temperature and calcined. After cooling to room temperature, a bimetallic framework is obtained.

[0008] 2) Preparation of precursor solution

[0009] Sodium alginate, MXene material and the bimetallic framework obtained in step 1) are added to deionized water and stirred thoroughly to mix the three together.

[0010] 3) Preparation of aerogels using the ice template method

[0011] Using a thermally conductive copper plate enclosed by polytetrafluoroethylene as a mold, the precursor solution prepared in step 2) was poured into the mold, directional freezing was performed using liquid nitrogen, and aerogel was obtained after low-temperature drying.

[0012] 4) Modified aerogel

[0013] The aerogel obtained in step 3) is placed in a tube furnace and heated under nitrogen protection until it cools to room temperature.

[0014] In this invention, a Ni-Co or Cu-Co bimetallic catalyst system is used. Step 1) requires the use of corresponding soluble salts to ensure sufficient mixing between elements. The bimetallic ZIF is formed with 2-methylimidazole in a reactor at 120℃~200℃. The soluble Ni salt is one of Ni(NO3)2, NiCl2, or NiSO4; the soluble copper salt is one of Cu(NO3)2, CuCl2, or CuSO4; and the soluble Co salt is one of Co(NO3)2, CoCl2, or CoSO4. The molar ratio of Ni or Cu to Co is 1:(0.8~2.2). Finally, the bimetallic ZIF is calcined in a high-temperature furnace to form a bimetallic framework structure MOFs. The heating rate of the high-temperature furnace is 3~6℃ / min, the calcination temperature is 350℃~400℃, the holding time is 3~5h, and the cooling rate is 3~6℃ / min.

[0015] Step 2) Disperse the bimetallic framework structure in a solution to prepare an aerogel. Add 1-3 parts by weight of sodium alginate, 0.1-1 parts by weight of MXene material and 0.3-3 parts by weight of Ni-Co bimetallic framework to deionized water and stir thoroughly to form a stable precursor solution.

[0016] Step 3) Use a thermally conductive copper plate as the mold, and use polytetrafluoroethylene to surround the desired shape on the thermally conductive copper plate. After pouring the precursor solution into it, use liquid nitrogen to directionally freeze it under the thermally conductive copper plate, and then dry the mold at a low temperature of -100℃ to -60℃ for 18 to 30 hours.

[0017] Step 4) The aerogel prepared by low-temperature drying is heated and calcined in a tube furnace at a heating rate of 3~6℃ / min, a calcination temperature of 100℃~150℃, and a holding time of 20~60min.

[0018] The beneficial effects of this invention are as follows: This invention uses sodium alginate, a marine biomass material, and monolayer MXene as matrix materials to prepare an aerogel with a unidirectional structure, exhibiting large porosity and specific surface area. After loading a bimetallic catalyst, the catalytic activity of the catalyst can be significantly improved. The method of this invention utilizes low-temperature calcination to induce decarboxylation of the carboxyl groups on the surface of sodium alginate, effectively improving the cycling stability of the aerogel catalyst in water. Compared with existing aerogel catalysts, this material exhibits superior catalytic activity and cycling stability. Attached Figure Description

[0019] Figure 1 This is a photograph of the sodium alginate / MXene / NiCo aerogel obtained in Example 1.

[0020] Figure 2 This is a SEM image of the sodium alginate / MXene / NiCo aerogel obtained in Example 1.

[0021] Figure 3 The image shows a SEM image of the sodium alginate / MXene / NiCo aerogel obtained in Example 1 after 10 cycles of use.

[0022] Figure 4 The diagram shows the degradation process of different organic dyes by the sodium alginate / MXene / NiCo aerogel obtained in Example 1. Detailed Implementation

[0023] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Example

[0024] A method for preparing a NiCo bimetallic catalyst aerogel includes the following steps:

[0025] 1) Preparation of the NiCo bimetallic framework: 0.5g Co(NO3)2·6H2O and 0.5g Ni(NO3)2 were added to beaker 1 containing 20ml methanol and stirred at 300r / min for 1h to allow the Co... 2+ Ni 2+ After uniform dispersion, 4 mmol of 2-methylimidazole was added to beaker 2 containing 20 ml of ethanol. After ultrasonic dispersion, it was quickly poured into beaker 1 and stirred for 1 h. The mixture was then transferred to a polytetrafluoroethylene reactor and reacted at 160 °C for 12 h. After centrifugation and drying, the mixture was placed in a high-temperature heating furnace and heated to 400 °C at 5 °C / min under nitrogen protection. After calcination at this temperature for 4 h, the temperature was lowered to room temperature at 5 °C / min to obtain the NiCo bimetallic framework.

[0026] 2) Preparation of precursor solution: Add 0.3g sodium alginate, 50mg monolayer MXene and 0.15g Ni-Co bimetallic framework obtained in step 1) to 10ml deionized water and stir for 2h to fully mix the three to form a stable and homogeneous solution;

[0027] 3) Preparation of aerogel by ice template method: A thermally conductive copper plate surrounded by polytetrafluoroethylene is used as a mold. The precursor solution prepared in step 2) is poured into the mold, directionally frozen with liquid nitrogen, and then freeze-dried at -80℃ for 24h.

[0028] 4) Aerogel modification: The aerogel obtained in step 3) is placed in a tube furnace and heated to 120°C at a heating rate of 5°C / min under nitrogen protection, and held for 30 min to obtain sodium alginate / MXene / NiCo aerogel. Example

[0029] A method for preparing a CuCo bimetallic catalyst aerogel includes the following steps:

[0030] 1) Preparation of CuCo bimetallic framework: 0.5g CuCl2·2H2O and 0.5g NiSO4 were added to beaker 1 containing 20ml methanol and stirred at 300r / min for 1h to allow Co to form a bimetallic framework. 2+ Cu 2+ After uniform dispersion, 4 mmol of 2-methylimidazole was added to beaker 2 containing 20 ml of ethanol. After ultrasonic dispersion, it was quickly poured into beaker 1 and stirred for 1 h. The mixture was then transferred to a polytetrafluoroethylene reactor and reacted at 180 °C for 10 h. After centrifugation and drying, the mixture was placed in a high-temperature heating furnace and heated to 380 °C at 4 °C / min under nitrogen protection. After calcination at this temperature for 5 h, the temperature was lowered to room temperature at 3 °C / min to obtain the CuCo bimetallic framework.

[0031] 2) Preparation of precursor solution: Add 0.3g sodium alginate, 0.1g monolayer MXene and 0.25g CuCo bimetallic framework obtained in step 1) to 10ml deionized water and stir for 2h to fully mix the three to form a stable and homogeneous solution;

[0032] 3) Preparation of aerogel by ice template method: A thermally conductive copper plate surrounded by polytetrafluoroethylene is used as a mold. The precursor solution prepared in step 2) is poured into the mold, directionally frozen with liquid nitrogen, and then freeze-dried at -80℃ for 24h.

[0033] 4) Aerogel modification: The aerogel obtained in step 3) is placed in a tube furnace and heated to 150°C at a heating rate of 4°C / min under nitrogen protection. The temperature is then maintained for 20 min to obtain sodium alginate / MXene / CuCo aerogel.

[0034] Figure 1The image shows the actual sodium alginate / MXene / NiCo aerogel obtained in Example 1. It can be seen that the aerogel has an extremely low density.

[0035] Figure 2 The image shows a SEM image of the sodium alginate / MXene / NiCo aerogel obtained in Example 1. It can be seen that the aerogel has a regular porous structure. Figure 3 The image shows a SEM image of the sodium alginate / MXene / NiCo aerogel obtained in Example 1 after 10 cycles of use. The porous structure of the aerogel remains unchanged after 10 cycles, indicating that it can be reused repeatedly.

[0036] Organic solvent catalytic degradation experiment: 10 mg of methylene blue / rhodamine B solution was accurately weighed and dissolved in a beaker containing 100 ml of water. A certain mass of catalyst was weighed and added to the methylene blue / rhodamine B solution. The beaker was placed in a constant temperature water bath shaking incubator and reacted for 15 min to allow the catalyst to fully adsorb the methylene blue / rhodamine B in the solution and eliminate the influence of adsorption. Timing was then started, and samples were taken at 1 min, 3 min, 5 min, 10 min, and 15 min. Methanol was then added to quench the reaction, and the absorbance change of the characteristic absorption peak of methylene blue was measured using a UV-Vis spectrophotometer. Different catalytic condition variables can be set using the following operations.

[0037] a. The temperature during processing is changed by controlling the temperature set in the constant temperature water bath shaker at 15℃, 20℃, 25℃, 35℃, and 45℃;

[0038] b. The pH value was changed by adding 0.1 mol / L sulfuric acid and 0.1 mol / L sodium hydroxide, and the actual pH value was determined by testing with a pH meter.

[0039] c. The reusability of the material was determined by directly recovering the degraded catalyst, washing it three times with deionized water, freeze-drying it again, and conducting the next degradation experiment to obtain the reusability data of the material.

[0040] The results are as follows Figure 4 As shown, Figure 4 The diagram shows the degradation process of different organic dyes by the sodium alginate / MXene / NiCo aerogel obtained in Example 1. It can be seen that the aerogel exhibits highly efficient catalytic degradation capabilities for methylene blue, rhodamine B, and methyl orange dyes.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a metal catalyst supported aerogel, characterized by, Includes the following steps: 1) Fabrication of bimetallic framework Soluble Ni salt or soluble Cu salt and soluble Co salt are added to methanol, stirred evenly, and then 2-methylimidazole is added. After ultrasonic dispersion, the mixture is stirred again to form a bimetallic ZIF. After stirring, the mixture is heated in a reaction vessel, and the reactants are centrifuged to obtain a solid product. After drying, the product is placed in a high-temperature furnace, heated under nitrogen protection, kept at the temperature and calcined. After cooling to room temperature, a bimetallic framework is obtained. 2) Preparation of precursor solution Sodium alginate, MXene material and the bimetallic framework obtained in step 1) are added to deionized water and stirred thoroughly to mix the three together. 3) Preparation of aerogels using the ice template method Using a thermally conductive copper plate enclosed by polytetrafluoroethylene as a mold, the precursor solution prepared in step 2) was poured into the mold, directional freezing was performed using liquid nitrogen, and aerogel was obtained after low-temperature drying. 4) Modified aerogel The aerogel obtained in step 3) is placed in a tube furnace and heated under nitrogen protection until it cools to room temperature.

2. The method of claim 1, wherein, In step 1), the soluble Ni salt is one of Ni(NO3)2, NiCl2, and NiSO4; the soluble copper salt is one of Cu(NO3)2, CuCl2, and CuSO4; and the soluble Co salt is one of Co(NO3)2, CoCl2, and CoSO4. The molar ratio of Ni or Cu to Co is 1:(0.8~2.2).

3. The method of claim 1, wherein, In step 2), the weight proportions of sodium alginate, MXene material, and Ni-Co bimetallic framework are: 1-3 parts sodium alginate, 0.1-1 part MXene material, and 0.3-3 parts Ni-Co bimetallic framework.

4. The method of claim 1, wherein, In step 1), the heating temperature of the reactor is 120℃~200℃, the heating rate of the high-temperature heating furnace is 3~6℃ / min, the calcination temperature is 350℃~400℃, the holding time is 3~5h, and the cooling rate is 3~6℃ / min; in step 3), the low-temperature drying temperature is -100℃~-60℃, and the drying time is 18~30h; in step 4), the heating rate of the tube furnace is 3~6℃ / min, the calcination temperature is 100℃~150℃, and the holding time is 20~60min.

5. Use of a metal-supported catalyst aerogel prepared according to any one of claims 1 to 4 for the catalytic degradation of organic dyes in water, characterized in that, The supported metal catalyst aerogel is used for the catalytic degradation of organic dyes in water.

6. Use according to claim 5, characterized in that, The organic dye is methylene blue, rhodamine B, or methyl orange.

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