Preparation method and application of CoFeLa trimetallic composite catalyst
By introducing lanthanide metals into the Co-Fe coordinated Prussian blue analog, the CoFeLa trimetal composite catalyst was prepared by the speed controlled simultaneous dropping method, which solved the problems of low catalyst catalytic efficiency and difficulty in recycling and utilization, and achieved efficient degradation of organic pollutants And reduce production costs.
Patent Information
- Application Number
- CN202211606926.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-12-13
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2042-12-13
AI Technical Summary
The existing Co-Fe coordinated Prussian blue analog catalysts have problems of low catalytic efficiency and difficulty in catalyzing the degradation of organic pollutants, and the traditional three-way catalyst preparation method is complex and costly.
The lanthanide metal was introduced based on the Co-Fe coordination Prussian blue analog, and the CoFeLa trimetal composite catalyst was prepared by controlling the speed and simultaneous dropping method. By mixing the solution of cobalt sulfate and lanthanum chloride heptahydrate and potassium ferricyanide solution, it formed The regular nanostructure significantly improves the degradation performance of the catalyst.
The ability to catalytically degrade organic pollutants is significantly improved, production costs are reduced, and the prepared CoFeLa trimetal composite catalyst still maintains high catalytic activity after multiple cycles, and has excellent degradation performance.
Smart Images
Figure CN116212885B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of environmental protection, and in particular to a preparation method and application of a CoFeLa trimetallic composite catalyst. Background Art
[0002] Advanced oxidation processes (AOPs) are one of the most effective methods for removing refractory organic pollutants from water. Compared with traditional treatment methods such as adsorption and membrane separation that separate, enrich and transfer organic pollutants in water, advanced oxidation processes can more effectively and directly remove and mineralize organic pollutants, avoid secondary pollution of degradation intermediates and toxic products, and are more efficient and safe. Therefore, the development of a novel and efficient catalyst material is indispensable.
[0003] Persulfate (PMS) is an asymmetric peroxide that can be activated in a variety of ways. Among them, Co and Fe-based transition metal catalysts show high efficiency in PMS activation. However, studies have shown that transition metal activation is difficult to recycle and is prone to secondary pollution. Compared with transition catalysts and mixed transition catalysts, ternary catalysts prepared by adding a third element are composite multiphase materials containing three elements or their oxides. Due to their multimetallic characteristics, they are expected to synergistically enhance catalytic activity. Co-Fe coordinated Prussian blue analogs are a class of superior bimetallic catalysts. Currently, in order to improve their catalytic efficiency, more and more studies on the optimization of related catalyst structures are being conducted, such as doping with nitrogen elements or adding other transition metals to construct ternary Prussian blue analog catalysts. Chen Zhongwei from the University of Waterloo studied the oxygen and hydrogen evolution reactions of ternary Ni-Co-Fe Prussian blue analogs. Ni was coordinated with Co-Fe Prussian blue analogs to prepare ternary Prussian blue analogs, but Ni and Co are both transition metals, and their catalytic effect still needs to be improved. Therefore, it is necessary to develop new trimetallic composite catalysts based on Co-Fe coordinated Prussian blue analogs to further improve the performance of the composite catalysts. Summary of the invention
[0004] In view of the above-mentioned prior art, the purpose of the present invention is to provide a preparation method and application of a CoFeLa trimetallic composite catalyst. The present invention introduces lanthanide metals to synthesize a novel trimetallic composite catalyst based on Co-Fe coordinated Prussian blue analogs, and the multi-metal catalyst has a synergistic effect, which significantly improves the ability of catalytic degradation of organic pollutants.
[0005] To achieve the above object, the present invention adopts the following technical solution:
[0006] The first aspect of the present invention provides a method for preparing a CoFeLa trimetallic composite catalyst, comprising the following steps:
[0007] A mixed solution containing cobalt sulfate and lanthanum chloride heptahydrate is prepared, and the mixed solution and potassium ferrocyanide solution are mixed together at the same dropping speed, and the mixture is continuously stirred to form a uniform solution. After the dropping is completed, the mixture is continuously stirred. After the stirring is completed, the mixture is allowed to stand, filtered, and the solid product is collected. The solid product is washed and dried to obtain a powder product, namely the CoFeLa trimetallic composite catalyst.
[0008] Preferably, in the mixed solution, the concentration of cobalt sulfate is 4 mmol / L, the concentration of lanthanum chloride heptahydrate is 2 mmol / L; and the concentration of potassium ferrocyanide solution is 4 mmol / L.
[0009] Preferably, the volume ratio of the mixed solution to the potassium ferrocyanide solution is 1:1.
[0010] Preferably, the dropping speed of the mixed solution and the potassium ferrocyanide solution is 25 mL / min, and the temperature during the dropping is 25° C.
[0011] Preferably, the rotation speed of the magnetic stirring is 500 r / min; and the stirring time is continued for 2 h.
[0012] Preferably, the standing time is 12 hours.
[0013] Preferably, the cleaning is: cleaning three times with deionized water.
[0014] Preferably, the drying is: vacuum drying at 60° C. for 24 hours.
[0015] The second aspect of the present invention provides a CoFeLa trimetallic composite catalyst prepared by the above method.
[0016] The third aspect of the present invention provides the use of a CoFeLa trimetallic composite catalyst in the degradation of organic pollutants in water.
[0017] Beneficial effects of the present invention:
[0018] (1) The present invention introduces lanthanide metals to synthesize a novel trimetallic composite catalyst based on Co-Fe coordinated Prussian blue analogs. The multimetallic catalyst has a synergistic effect and significantly improves the ability to catalyze the degradation of organic pollutants.
[0019] (2) The preparation method of the present invention is simple and the preparation process is controllable, which greatly reduces the production cost.
[0020] (3) The CoFeLa trimetallic composite catalyst prepared by the present invention still maintains a high catalytic activity after multiple cycles of use. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 : Scanning electron microscope image of CoFeLa01;
[0022] Figure 2 : SEM images of Comparative Examples 1-8;
[0023] Figure 3 :Transmission scanning electron microscope image of CoFeLa01;
[0024] Figure 4 : BET diagrams of Co-Fe PBA and CoFeLa01;
[0025] Figure 5 : Degradation properties of different materials;
[0026] Figure 6 : Repeatability of CoFeLa01 catalytic degradation of organic pollutants. DETAILED DESCRIPTION
[0027] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.
[0028] As introduced in the background technology section, the catalytic effect of catalysts containing transition metals is general and difficult to recycle. Based on this, the purpose of the present invention is to provide a preparation method and application of a CoFeLa trimetallic composite catalyst. The present invention adopts a method of controlling the speed and adding simultaneously to prepare a CoFeLa trimetallic composite nanocatalyst. According to preliminary investigations, it was found that the research on the degradation of organic pollutants in water bodies using trimetallic composite nanocatalysts is not very sufficient, especially the preparation methods of some catalysts are too complicated, and the cost of adding precious metals such as gold, silver, and platinum is too expensive. Based on the Prussian blue analogues of Co / Fe coordination that have been widely studied, the present invention adds a lanthanide metal element La, and prepares a trimetallic composite catalyst using a simple method and a process-controllable speed and adding simultaneously to obtain a trimetallic composite catalyst, which not only greatly reduces the production cost, but also the multi-metal catalyst also has a synergistic effect and improves the catalytic degradation performance. The preparation method and material structure have the following advantages: (1) The synthesis method is simple. The synthesis process uses an aqueous solution without involving an organic solution. The catalyst preparation can directly obtain a truncated microcube structure by a controlled rate co-precipitation method at room temperature; (2) The product synthesized by the controlled rate simultaneous dripping method has a regular morphology, uniform particle size, and more microporous structures; (3) The lanthanide metal element La can be successfully added to the bimetallic material; (4) The degradation performance of the obtained trimetallic composite material is significantly improved compared with the bimetallic material, and the performance decreases when La is added in excess of a certain proportion; (5) The CoFeLa catalyst has stable performance and still maintains a high activity after multiple cycles.
[0029] In the present invention, lanthanum chloride heptahydrate can only be added to cobalt sulfate solution, otherwise it is impossible to obtain a CoFeLa trimetallic composite catalyst with regular morphology and uniform particle size, and the catalytic effect is not high. The degradation performance is best only when 2mmol / L of lanthanum chloride heptahydrate is added. By using a peristaltic pump to simultaneously drop into the reaction system at the same speed (25mL / min), compared with the method of direct mixing or one solution being added dropwise to another solution, uniform and regular particles cannot be obtained, and the method of controlling the speed and dropping simultaneously can simply and stably obtain uniform particles. The trimetallic catalyst prepared in this application has more microporous structures below 1nm. Usually, Prussian blue analogs require certain complexing agents to form a uniform and regular morphology. This application does not add any complexing agent, and a regular hexahedron regular structure can be obtained. The active exposed crystal faces of the regular structure of the regular hexahedron are exposed more outward, which can provide more active sites for PMS activation, accelerate the catalyst and PMS activation to produce free radicals, and make contact with pollutants easier, so that organic pollutants are mineralized and degraded as much as possible by free radicals.
[0030] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.
[0031] The test materials used in the examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels.
[0032] Example
[0033] (1) Prepare 300 mL of solution A (4 mmol / L potassium ferrocyanide solution) and 300 mL of solution B (4 mmol / L cobalt sulfate mixed with 2 mmol / L lanthanum chloride heptahydrate solution) respectively.
[0034] (2) The temperature was controlled at 25°C, and two peristaltic pumps with the same speed (25 mL / min) were used to simultaneously add solution A and solution B into a 1000 mL beaker, and the mixture in the container was continuously magnetically stirred to form a uniform solution. After the addition of solution A and solution B was completed, stirring was continued for 2 hours.
[0035] (3) After stirring, the mixture was allowed to stand for 12 hours, and the solid product was collected by vacuum filtration and washed three times with deionized water.
[0036] (4) Dry under vacuum at 60°C for 24 hours to obtain a powder product, which is denoted as CoFeLaO1.
[0037] Comparative Example 1
[0038] The difference from the embodiment is that the addition amount of lanthanum chloride heptahydrate is 4 mmol / L, and the final product prepared is recorded as CoFeLaO2.
[0039] Comparative Example 2
[0040] The difference from the embodiment is that the addition amount of lanthanum chloride heptahydrate is 6 mmol / L, and the final product prepared is recorded as CoFeLaO3.
[0041] Comparative Example 3
[0042] The difference from the embodiment is that lanthanum chloride heptahydrate is changed to lanthanum nitrate hexahydrate, the addition amount is 2 mmol / L, and the final product prepared is recorded as CoFeLaO4.
[0043] Comparative Example 4
[0044] The difference from the embodiment is that cobalt sulfate is changed to cobalt nitrate, the addition amount is 4 mmol / L, and the final product prepared is recorded as CoFeLaO5.
[0045] Comparative Example 5
[0046] The difference from the embodiment is that the lanthanum-cobalt mixed solution is added dropwise to the potassium ferrocyanide solution at a rate of 25 mL / min, and the final product prepared is recorded as CoFeLaO6.
[0047] Comparative Example 6
[0048] The difference from the embodiment is that 300 mL of each of lanthanum chloride heptahydrate solution, cobalt sulfate solution and potassium ferrocyanide solution are directly mixed, and the final product prepared is recorded as CoFeLaO7.
[0049] Depend on Figure 1 and Figure 2 It can be seen that the CoFeLaO1 trimetallic composite catalyst prepared in the example has a regular morphology and uniform particle size. However, the catalysts prepared in comparative examples 1 to 6 have irregular morphology and non-uniform particle size. Figure 5 It can be seen that the CoFeLaO1 trimetallic composite catalyst prepared in Example has the best degradation effect.
[0050] Comparative Example 7
[0051] Preparation of Co-Fe coordinated Prussian blue analogs:
[0052] The difference from the embodiment is that lanthanum chloride heptahydrate is not added, and the final product prepared is recorded as Co-FePBA.
[0053] Comparative Example 8
[0054] The Co-FePBA prepared in Comparative Example 7 was added to a 2 mmol / L lanthanum chloride heptahydrate solution, magnetically stirred for 2 hours, allowed to stand for 12 hours, and the solid product was collected by vacuum filtration, and washed repeatedly with deionized water for 3 times. The product was dried under vacuum at 60°C for 24 hours to obtain a powder product, which was recorded as La-CoFePBA.
[0055] Depend on Figures 1-2 It can be seen that the catalysts prepared in the examples are regular and uniform hexahedral particles, while the catalysts prepared in comparative examples 1 to 8 are irregular in shape. Figures 3-4 It can be seen that the catalyst prepared in the example has successfully added La element on the basis of Co-FePBA, and its micropore structure below 1 nm is much more than that of Co-Fe PBA.
[0056] Test example
[0057] Wastewater containing norfloxacin was collected from a sewage outlet of a pharmaceutical factory in Zhuhai City, and the concentration of norfloxacin compounds in the wastewater was measured by ultraviolet spectrophotometry to be 10 mg / L. The catalysts prepared in Examples and Comparative Examples 1 to 8 were respectively added to 100 mL of wastewater filtered through a 0.22 μm filter membrane, and potassium persulfate (PMS) was added after mechanical stirring for half an hour in advance. The samples were filtered and added to a methanol solution at a certain point, and the volume of methanol and the sampling solution was equal. The concentration of norfloxacin compounds in the wastewater was detected, and the degradation rate of the norfloxacin compounds was calculated.
[0058] After the catalyst was recovered by suction filtration, it was washed three times with deionized water, dried in a vacuum drying oven at 60°C for 24 hours, and then added to the above wastewater containing norfloxacin compounds. This step was repeated 6 times, and the concentration of norfloxacin compounds in the wastewater was detected. The degradation rate of norfloxacin compounds was calculated. The results are shown in Tables 1 and Figures 5-6 .
[0059] Table 1: Multiple cycle performance of different materials
[0060]
[0061] It can be seen from Table 1 that, compared with the catalysts prepared in Comparative Examples 1 to 8, the catalysts prepared in Examples have higher ability to degrade norfloxacin and higher ability to be recycled. Figure 5 It can be seen that the ability of the catalyst prepared by the method of the present invention to degrade norfloxacin is far superior to that of the catalysts prepared in Comparative Examples 1 to 8. Figure 6 It can be seen that the catalyst prepared by the present invention has good recycling ability, which indicates that the catalyst prepared by the method of the present invention can improve the degradation ability of the catalyst.
[0062] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing a CoFeLa trimetallic composite catalyst for degrading organic pollutants in water, characterized in that: The following steps are involved: A mixed solution containing cobalt sulfate and lanthanum chloride heptahydrate is prepared, the mixed solution and potassium ferrocyanide solution are mixed together at the same dropping speed, and the mixed solution is continuously stirred to form a uniform solution, and the stirring is continued after the dropping is completed. After the stirring is completed, the mixed solution is allowed to stand, filtered, and the solid product is collected, and the powder product, i.e., the CoFeLa trimetallic composite catalyst, is obtained after washing and drying; In the mixed solution, the concentration of cobalt sulfate is 4 mmol / L, the concentration of lanthanum chloride heptahydrate is 2 mmol / L; the concentration of the potassium ferrocyanide solution is 4 mmol / L; The dropping speed of the mixed solution and the potassium ferrocyanide solution was 25 mL / min, and the temperature during the dropping was 25°C.
2. The preparation method according to claim 1, characterized in that: The volume ratio of the mixed solution to the potassium ferrocyanide solution is 1:
1.
3. The preparation method according to claim 1, characterized in that: The rotation speed of the magnetic stirring was 500 r / min; and the stirring time was continued for 2 h.
4. The preparation method according to claim 1, characterized in that: The standing time is 12 hours.
5. The preparation method according to claim 1, characterized in that: The washing is: washing with deionized water three times.
6. The preparation method according to claim 1, characterized in that: The drying step is: vacuum drying at 60° C. for 24 hours.
7. The CoFeLa trimetallic composite catalyst obtained by the preparation method according to any one of claims 1 to 6.
8. Use of the CoFeLa trimetallic composite catalyst according to claim 7 in degrading organic pollutants in water.