Preparation method and application of a biomass carbon-supported cerium / molybdenum single-atom catalyst

Abstract

This invention belongs to the field of heterogeneous catalyst technology, and specifically relates to a method for preparing and applying a biomass carbon-supported cerium / molybdenum single-atom catalyst. Oyster mushrooms are dried, pulverized, and then impregnated and dispersed in water. Soluble cerium salt, soluble molybdenum salt, and urea are added to the aforementioned dispersion system. After thorough dispersion, the mixture is dried to obtain a biomass carbon precursor-supported cerium / molybdenum salt. The biomass carbon precursor-supported cerium / molybdenum salt is calcined at 200℃~600℃ for 3h~6h under a protective atmosphere, and after cooling, a black powder is obtained. The black powder is acid-treated, washed until neutral, and then dried to obtain the biomass carbon-supported cerium / molybdenum single-atom catalyst. This catalyst exhibits excellent catalytic activity and reusability when used to activate persulfate treatment of dyeing and printing wastewater.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous catalyst technology, and specifically relates to a method for preparing and applying a biomass carbon-supported cerium / molybdenum single-atom catalyst. Background Technology

[0002] Dyeing and printing wastewater refers to wastewater containing harmful substances generated during the dyeing and printing industry. These harmful substances may include various dyes, auxiliaries, heavy metals, organic compounds, etc. The discharge and treatment of dyeing and printing wastewater does indeed present certain technical challenges. Persulfate-activated advanced oxidation technology is considered a novel and efficient treatment method. In recent years, due to the popularization of green chemistry concepts and based on sustainable development strategies, attention has gradually shifted to the removal of dyeing and printing wastewater using activated persulfate, focusing on improving atom economy, energy conservation, and environmental protection.

[0003] The use of heterogeneous catalysts is considered the most efficient and energy-saving option. However, this option still has certain limitations, such as low mass transfer efficiency, high metal leaching rate, and low mineralization rate. Therefore, it is necessary to develop new environmentally friendly catalyst materials.

[0004] Single-atom catalysts (SACs) bridge the gap between heterogeneous and homogeneous catalysis, showing great application potential in many catalytic systems. SACs exhibit advantages such as high metal utilization, strong interactions between atoms and the support, high catalytic activity, and low coordination numbers. Furthermore, SACs supported on various substrates endow them with tunable catalytic activity, selectivity, and durability. Biomass carbon, with its large specific surface area, facilitates the dispersion and immobilization of single-atom catalysts. Its porous structure enables rapid mass and energy transfer, and its tunable chemical coordination environment makes it considered an ideal support for confining single atoms. Further research into SACs has revealed that non-noble metal SACs are inexpensive yet possess the excellent catalytic performance of noble metals, making them suitable for a wide range of applications. Summary of the Invention

[0005] This application provides a method for preparing a cerium / molybdenum single-atom catalyst supported on biomass carbon, comprising the following steps:

[0006] (1) Dry the oyster mushrooms, crush them, and soak them in water to disperse them;

[0007] (2) Add soluble cerium salt, soluble molybdenum salt and urea to the dispersion system obtained in step (1), and after sufficient dispersion, dry them together to obtain cerium salt / molybdenum salt loaded with biomass carbon precursor.

[0008] (3) The cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) is calcined at 200℃~600℃ for 3h~6h under a protective atmosphere, and then cooled to obtain a black powder.

[0009] (4) The black powder obtained in step (3) is treated with acid and washed until neutral, and then dried to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst.

[0010] As a preferred option: in step (1), the oyster mushrooms are dried and then pulverized to 30-300 mesh.

[0011] As a preferred embodiment, in step (2), the cerium element in the soluble cerium salt and the molybdenum element in the soluble molybdenum salt together account for 0.25 to 1.25% of the mass of the biomass carbon precursor.

[0012] Preferably, in step (2), urea accounts for 0.5 to 4.5% of the mass of the biomass carbon precursor.

[0013] As a preferred embodiment: In step (3), the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) is heated to 200°C for 3 hours at a heating rate of 5-10°C / min under a protective atmosphere, and then heated to 600°C for 3 hours at a heating rate of 5-10°C / min.

[0014] As a preferred option, the acid treatment in step (4) is to add the black powder obtained in step (3) into a 2 mol / L HCl aqueous solution, stir at a constant temperature of 80°C for 10 h, and then filter and retain the filter cake.

[0015] The present invention also provides an application of the biomass carbon-supported cerium / molybdenum single-atom catalyst prepared by the above method in activating persulfate for the treatment of dyeing and printing wastewater.

[0016] The beneficial effects of this invention are as follows:

[0017] Oyster mushrooms, as an edible fungus, contain a large amount of amino acids. These amino acids decompose into nitrogen-containing gases upon heating, which helps increase the specific surface area and pore structure of the carrier. On the other hand, they can provide nitrogen dopant for biomass carbon. Under heating conditions, nitrogen atoms coordinate with Ce / Mo metals, effectively anchoring and dispersing single-atom Ce / Mo centers. Subsequent acid treatment removes the Ce / Mo nanoparticles aggregated on the carrier, allowing for better exposure of the more catalytically active single-atom Ce / Mo (the single-atom Ce / Mo is strongly anchored and confined to the derived nitrogen-doped biomass carbon by nitrogen atoms, and will not detach during acid washing). Furthermore, not all doped nitrogen elements have the function of anchoring metal atoms. In biocarbon material carriers, nitrogen can be classified into nitrogen oxides, graphitic nitrogen, pyridine nitrogen, and pyrrole nitrogen. During the research on single-atom preparation, the applicant found that pyridine nitrogen and pyrrole nitrogen are significantly more conducive to forming metal-N bonds with single metal atoms.

[0018] Based on this, this scheme also adds urea. Although the nitrogen in urea can replenish the nitrogen that leaves the substrate after being vaporized by heat, in most cases, because urea is introduced as an additive, the binding between the nitrogen introduced by urea and the substrate is not strong. This leads to the nitrogen introduced by urea easily detaching from the substrate during subsequent high-temperature and acid treatments, causing the metal single atoms anchored by this nitrogen to also be lost, resulting in a limited replenishment effect. However, this scheme selects oyster mushroom as the substrate. Oyster mushroom is an edible fungus, and its nitrogen is largely present in the form of amino acids. Amino acids in oyster mushroom itself constitute stable acidic active sites. After the nitrogen in amino acids volatilizes by heat, these active sites do not immediately disappear. The nitrogen in urea re-binds to these active sites and binds more stably, making it less prone to loss. This increases the probability of stable binding between nitrogen in the substrate and biomass carbon, and also allows more metal single atoms to be ultimately anchored to the oyster mushroom substrate, increasing catalytic activity. Since the main purpose of using urea in this method is to supplement nitrogen to oyster mushrooms during the preparation process, the amount of urea added is very small.

[0019] In summary, this catalyst, using nitrogen-doped biomass carbon with a large specific surface area as a support, is beneficial for the dispersion and immobilization of single-atom catalysts. It also has a porous structure, enabling rapid mass and energy transfer, as well as an adjustable chemical coordination environment. When used to activate persulfate treatment of dyeing and printing wastewater, it exhibits excellent catalytic activity, achieving efficient and rapid degradation and mineralization of dyeing and printing wastewater pollution. At the same time, based on the anchoring effect of the support on active single atoms, it reduces metal leaching of the catalyst, improves the reusability of the catalyst, and achieves environmental friendliness. Attached Figure Description

[0020] Figure 1 The image shows the XRD pattern of the Ce / Mo-NBC composite material prepared in Example 1 of this application.

[0021] Figure 2 This is a TEM image of the Ce / Mo-NBC composite material prepared in Example 1 of this application;

[0022] Figure 3 This is a TEM image of the Ce / Mo-NBC composite material prepared in Example 1 of this application. Detailed Implementation

[0023] A method for preparing a biomass carbon-supported cerium / molybdenum single-atom catalyst includes the following steps:

[0024] (1) Dry the oyster mushrooms and then pulverize them to 30-300 mesh, and then soak and disperse them in water;

[0025] (2) According to the proportion of cerium in soluble cerium salt and molybdenum in soluble molybdenum salt to 0.25-1.25% of the biomass carbon precursor mass, and urea to 0.5-4.5% of the biomass carbon precursor mass, soluble cerium salt, soluble molybdenum salt and urea are added to the dispersion system obtained in step (1). After being stirred at room temperature (25℃, the same below) for 12 hours to disperse fully, the mixture is dried as a whole to obtain cerium salt / molybdenum salt loaded on biomass carbon precursor.

[0026] (3) The cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) is heated to 200°C for 3 hours at a heating rate of 5-10°C / min under a protective atmosphere, and then heated to 600°C for 3 hours at a heating rate of 5-10°C / min. After cooling, a black powder is obtained.

[0027] (4) The black powder obtained in step (3) is added to a 2 mol / L HCl aqueous solution, stirred at 80°C for 10 h, filtered, the filter cake is washed until neutral, and then dried to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst.

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of protection of the invention.

[0029] Example 1

[0030] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0031] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratio: cerium element was 0.025% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.025% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: urea was 0.5% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to disperse the system sufficiently, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0032] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0033] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.26% and the weight loading of molybdenum metal was 0.21%.

[0034] Example 2

[0035] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0036] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratio: 0.05% of the mass of dried oyster mushrooms dispersed in water in step (1) and 0.05% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: 1% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to ensure sufficient dispersion, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0037] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0038] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.31% and the weight loading of molybdenum metal was 0.25%.

[0039] Example 3

[0040] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0041] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratios: cerium element was 0.075% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.075% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: urea was 1.5% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to ensure sufficient dispersion, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0042] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0043] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.33% and the weight loading of molybdenum metal was 0.28%.

[0044] Example 4

[0045] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0046] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratios: cerium element was 0.1% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.1% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: urea was 2% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to ensure sufficient dispersion, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0047] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0048] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.58% and the weight loading of molybdenum metal was 0.41%.

[0049] Example 5

[0050] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0051] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratios: cerium element was 0.125% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.125% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: urea was 2.5% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to ensure sufficient dispersion, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0052] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0053] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.67% and the weight loading of molybdenum metal was 0.52%.

[0054] Example 6

[0055] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0056] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratios: cerium element was 0.15% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.15% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: urea was 3% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to ensure sufficient dispersion, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0057] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0058] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.73% and the weight loading of molybdenum metal was 0.63%.

[0059] Example 7

[0060] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0061] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratios: cerium element was 0.175% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.175% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: urea was 3.5% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to ensure sufficient dispersion, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0062] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0063] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.84% ​​and the weight loading of molybdenum metal was 0.75%.

[0064] Example 8

[0065] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0066] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratios: cerium element was 0.2% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.2% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: urea was 4% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to ensure sufficient dispersion, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0067] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0068] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 1.06% and the weight loading of molybdenum metal was 0.90%.

[0069] Example 9

[0070] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0071] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratios: cerium element was 0.225% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.225% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the following ratio: urea was 4.5% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to ensure sufficient dispersion, the system was dried in an oven at 120℃ to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0072] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0073] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 1.37% and the weight loading of molybdenum metal was 1.13%.

[0074] Comparative Example 1

[0075] Molybdenum was not added; the missing molybdenum was replaced with cerium. All other operations were the same as in Example 1.

[0076] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0077] (2) Cerium nitrate was added to the dispersion system obtained in step (1) according to the cerium element being 0.05% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the urea element being 0.5% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to disperse the system sufficiently, the system was dried in an oven at 120℃ to obtain cerium salt loaded with biomass carbon precursor.

[0078] (3) Place the cerium salt loaded with the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0079] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium single-atom catalyst, namely Ce-NBC metal single-atom catalyst. The weight loading of cerium metal in this catalyst was 0.63%.

[0080] Comparative Example 2

[0081] Cerium was not added; the missing cerium was replaced with molybdenum. All other operations were the same as in Example 1.

[0082] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0083] (2) Molybdenum nitrate was added to the dispersion system obtained in step (1) according to the molybdenum element being 0.05% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the urea element being 0.5% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 12 h to disperse the system sufficiently, the system was dried in an oven at 120℃ to obtain molybdenum salt loaded with biomass carbon precursor.

[0084] (3) The molybdenum salt loaded with biomass carbon precursor obtained in step (2) is placed in a crucible and calcined at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, it is calcined at 600°C for 3 hours at a heating rate of 10°C / min and then cooled to room temperature to obtain black powder.

[0085] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported molybdenum single-atom catalyst, namely Mo-NBC metal single-atom catalyst. The weight loading of molybdenum metal in this catalyst is 0.56%.

[0086] Comparative Example 3

[0087] No urea was added; all other procedures were the same as in Example 4.

[0088] (1) Dry the oyster mushrooms and then pulverize them to 100 mesh. Soak and disperse them in deionized water at a ratio of 1:50.

[0089] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratios: cerium element was 0.1% of the mass of dried oyster mushrooms dispersed in water in step (1) and molybdenum element was 0.1% of the mass of dried oyster mushrooms dispersed in water in step (1). After stirring at room temperature for 13 hours to disperse fully, the mixture was dried in an oven at 120°C to obtain cerium / molybdenum salt loaded with biomass carbon precursor.

[0090] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0091] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-BC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.36% and the weight loading of molybdenum metal was 0.22%.

[0092] Compare with Example 1

[0093] Replace the oyster mushrooms with chitosan, and follow the same steps as in Example 4:

[0094] (1) Disperse chitosan thoroughly in deionized water at a material-to-liquid ratio of 1:50;

[0095] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the ratio of cerium element to chitosan dispersed in water in step (1) as 0.1% and molybdenum element to chitosan dispersed in water in step (1) as 0.1% and the ratio of molybdenum element to chitosan dispersed in water in step (1). After stirring at room temperature for 60 min, urea was added to the system according to the ratio of urea to chitosan dispersed in water in step (1) as 2%. After stirring at room temperature for 12 h to disperse the system sufficiently, the system was dried in an oven at 120℃ to obtain cerium salt / molybdenum salt loaded with biomass carbon precursor.

[0096] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0097] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.30% and the weight loading of molybdenum metal was 0.27%.

[0098] Compare with Example 2

[0099] No urea was added in this case compared to Control Example 1; all other procedures were the same as in Control Example 1.

[0100] (1) Disperse chitosan thoroughly in deionized water at a material-to-liquid ratio of 1:50;

[0101] (2) Cerium nitrate and molybdenum nitrate were added to the dispersion system obtained in step (1) according to the following ratio: cerium element is 0.1% of the mass of chitosan dispersed in water in step (1) and molybdenum element is 0.1% of the mass of chitosan dispersed in water in step (1). After stirring at room temperature for 13 hours to disperse fully, the mixture was dried in an oven at 120°C to obtain cerium salt / molybdenum salt loaded with biomass carbon precursor.

[0102] (3) Place the cerium / molybdenum salt loaded on the biomass carbon precursor obtained in step (2) into a crucible, and calcine it at 200°C for 3 hours at a heating rate of 10°C / min under a high-purity Ar atmosphere. Then, calcine it at 600°C for 3 hours at a heating rate of 10°C / min. After cooling naturally to room temperature, a black powder is obtained.

[0103] (4) The black powder obtained in step (3) was added to a 2 mol / L HCl aqueous solution at a material-to-liquid ratio of 1:100. After stirring at 80°C for 10 h, the mixture was filtered. The filter cake was washed with deionized water until the pH of the washed water was 7. The filter cake solid was then dried in a vacuum drying oven at 80°C to obtain a biomass carbon-supported cerium / molybdenum single-atom catalyst, namely Ce / Mo-BC bimetallic single-atom catalyst. In this catalyst, the weight loading of cerium metal was 0.29% and the weight loading of molybdenum metal was 0.24%.

[0104] The supported catalysts prepared in the above examples, comparative examples, and control examples were used to directly activate potassium persulfate to treat dyeing and printing wastewater. Methylene blue was used to simulate dyeing and printing wastewater, with a total volume of 40 mL and a methylene blue concentration of 40 mg / L. At room temperature, 5 mg of the supported catalyst and 20 mg of potassium persulfate were added to each simulated wastewater. After stirring at 120 r / min for 3 min, the removal rate of methylene blue in each wastewater was immediately measured (1 - methylene blue concentration in the simulated dyeing and printing wastewater after reaction ÷ original methylene blue concentration in the simulated dyeing and printing wastewater 40 mg / L × 100%). The results are shown in the table below.

[0105]

[0106] As the content of single atoms loaded on the catalyst increases in Examples 1 to 9 above, the catalytic effect shows a trend of first increasing and then decreasing, as shown in the table above. This is probably because after the number of single atoms on the catalyst increases to a certain extent, more single atoms aggregate together to form sub-nano particles. Therefore, although the total number of metal single atoms increases, the overall catalytic effect decreases.

[0107] Compared with Comparative Examples 1 and 2, when the catalyst with a single metal atom is supported, the amount of active metal loaded in the catalyst product is reduced, but the catalytic effect is significantly improved. This should be because molybdenum and cerium form a single-atom alloy with a diatomic structure. The alloy causes electrons to shift, thereby further improving the catalytic activity.

[0108] Compared to Example 4, the catalyst in Comparative Example 3, lacking urea, showed a significant decrease in the final metal atom loading and catalytic effect. This fully demonstrates the contribution of urea in anchoring single metal atoms under this scheme. However, when the oyster mushroom in the Comparative Example was replaced with chitosan, the final anchoring effect of the catalyst on metal atoms and its catalytic effect did not change much with or without the participation of urea. Although both chitosan and oyster mushrooms contain nitrogen as a carbon source, the form in which nitrogen exists is drastically different. In chitosan, nitrogen exists in the form of amino groups, while in oyster mushrooms, nitrogen exists primarily in the form of amino acids. Therefore, the applicant argues that amino acids, as acids, can form relatively stable acidic active sites in oyster mushrooms. After the nitrogen in amino acids evaporates upon heating, the active site does not immediately disappear. The added urea nitrogen can re-bind stably with the active site and remain on the catalyst support to anchor metal atoms. However, the amino groups in chitosan cannot form similar acidic active sites. After being vaporized upon heating, even if urea nitrogen is added, it cannot stably bind to the chitosan matrix. In the end, most of the added urea nitrogen is detached from the catalyst matrix due to heating, vaporization, acid washing, and other interventions, thus failing to play the role of "anchoring metal atoms."

[0109] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a biomass-carbon supported cerium / molybdenum single-atom catalyst, characterized by: The preparation method comprises the following steps, (1) drying and crushing Pleurotus ostreatus, and immersing and dispersing in water; (2) adding soluble cerium salt, soluble molybdenum salt and urea into the dispersion system obtained in step (1), and after sufficient dispersion, integrally drying to obtain biomass carbon precursor loaded cerium salt / molybdenum salt; (3) calcining the biomass carbon precursor loaded cerium salt / molybdenum salt obtained in step (2) at 200-600 DEG C under a protective atmosphere for 3-6 hours, and after cooling, obtaining a black powder; (4) after acid treatment, washing to neutral, and drying, the black powder obtained in step (3) obtains the biomass carbon loaded cerium / molybdenum single-atom catalyst, namely Ce / Mo-NBC bimetallic single-atom catalyst; In step (2), the cerium element in the soluble cerium salt and the molybdenum element in the soluble molybdenum salt account for 0.25-1.25% of the mass of the biomass carbon precursor; In step (2), the urea accounts for 0.5-4.5% of the mass of the biomass carbon precursor.

2. The method for preparing the biomass carbon-supported cerium / molybdenum single-atom catalyst as described in claim 1, characterized in that: In step (1), the Pleurotus ostreatus is crushed to 30-300 mesh after drying.

3. The method for preparing the biomass carbon-supported cerium / molybdenum single-atom catalyst as described in claim 1, characterized in that: In step (3), the biomass carbon precursor loaded cerium salt / molybdenum salt obtained in step (2) is calcined at 200 DEG C under a protective atmosphere at a heating rate of 5-10 DEG C / min for 3 hours, and then calcined at 600 DEG C under a protective atmosphere at a heating rate of 5-10 DEG C / min for 3 hours.

4. The method of claim 1, wherein the biomass carbon supported cerium / molybdenum monatomic catalyst is prepared by the following steps: (1) preparing a biomass carbon support; (2) preparing a cerium / molybdenum monatomic catalyst; and (3) mixing the biomass carbon support and the cerium / molybdenum monatomic catalyst. In step (4), the acid treatment is that the black powder obtained in step (3) is added into 2 mol / L HCl aqueous solution, and after constant temperature stirring at 80 DEG C for 10 hours, the filter cake is reserved by filtration.

5. Application of the biomass carbon loaded cerium / molybdenum single-atom catalyst obtained by the preparation method in any one of claims 1-4 in activating persulfate for treating printing and dyeing wastewater.

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