Preparation method of montmorillonite-based cobalt monatomic catalyst

Abstract

The invention discloses a preparation method of a montmorillonite-based cobalt monatomic catalyst, and belongs to the technical field of clay mineral resource utilization. The preparation method of the montmorillonite-based cobalt monatomic catalyst comprises the following steps: mixing montmorillonite and cobalt salt, and performing ball milling to obtain the montmorillonite-based cobalt monatomic catalyst. The preparation method disclosed by the invention is simple, high in yield, low in cost and easy for large-scale preparation, and is expected to provide a new thought for high-valued utilization of clay minerals and large-scale synthesis of monatomic catalysts.

Description

Technical Field

[0001] This invention relates to the field of clay mineral resource utilization technology, and in particular to a method for preparing a montmorillonite-based cobalt single-atom catalyst. Background Technology

[0002] Single-atom catalysts (SACs) are mainly based on carbon-based supports, while utilizing the strong affinity of non-metallic elements (N, Si, O, S, etc.) for metal atoms to coordinate with metal single atoms to form a coordination structure with "metal-non-metallic elements," resulting in catalytic sites with excellent catalytic activity and selectivity. This has made them a research frontier and hot topic in the field of advanced oxidation. However, carbon-based single-atom catalysts have the following problems: (1) The preparation process usually involves high-temperature pyrolysis of organic precursors, during which metal atoms move and agglomerate into large nanoclusters; (2) During the preparation process, the metal center is often encapsulated in the carbon matrix, resulting in poor dispersion. Both of these factors lead to a decrease in catalytic activity. In addition, the commonly used preparation methods are mainly pyrolysis, ionization radiation, physical and chemical deposition, etc., which have problems such as complex processes, low yields, high costs, and difficulty in large-scale preparation. Therefore, how to enhance the activity and stability of single-atom catalytic sites, achieve simple and environmentally friendly preparation processes, and the large-scale synthesis of single-atom catalysts and the practical application of single-atom activated PMS technology remain challenges. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing montmorillonite-based cobalt single-atom catalysts to solve the problems existing in the prior art. The preparation method of this invention can effectively suppress the migration and aggregation of single atoms during the preparation process, increase the exposure rate of the metal center (active site), thereby enhancing the activity and stability of the single-atom catalytic sites, and realizing the high-value utilization of clay minerals and the large-scale synthesis of single-atom catalysts.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention: a method for preparing a montmorillonite-based cobalt single-atom catalyst, comprising the following steps:

[0006] Montmorillonite and cobalt salt were mixed and ball-milled to obtain the montmorillonite-based cobalt single-atom catalyst.

[0007] In montmorillonite-based cobalt single-atom catalysts, no metallic bonds are formed between Co atoms, hence the name montmorillonite-based cobalt single-atom catalyst.

[0008] Furthermore, the cobalt salt includes cobalt chloride.

[0009] Furthermore, the mass ratio of montmorillonite to cobalt salt is (5-20):1.

[0010] Furthermore, the ball-to-material ratio of the ball mill is (5-10):1, the rotation speed is 300 rpm, the ball mill is rotated in both directions, the rotation direction is changed every 60 minutes, the interval between the forward and reverse rotation is 10 minutes, and the total ball milling time is 8-12 hours.

[0011] The second technical solution of the present invention: a montmorillonite-based cobalt single-atom catalyst prepared by the above preparation method.

[0012] The third technical solution of the present invention: the application of the above-mentioned montmorillonite-based cobalt single-atom catalyst in the degradation of organic pollutants by activated persulfate (PMS).

[0013] Furthermore, the organic pollutants include one or more of bisphenol A, p-chlorophenol, p-nitrophenol, p-hydroxybenzoic acid, metronidazole, carbamazepine, acetaminophen, sulfamethoxazole, tetracycline, amoxicillin, and atrazine.

[0014] The fourth technical solution of the present invention: a method for degrading organic pollutants, comprising the following steps: adding the above-mentioned montmorillonite-based cobalt single-atom catalyst and persulfate to an organic pollutant solution, mixing evenly, and then carrying out a degradation reaction.

[0015] Furthermore, the ratio of organic pollutants, montmorillonite-based cobalt single-atom catalyst, and persulfate in the organic pollutant solution is 10 mg: 0.1–0.3 g: 0.5–2 mmol.

[0016] The fifth technical solution of the present invention: a method for continuous degradation of organic pollutants, comprising the following steps: loading the above-mentioned montmorillonite-based cobalt single-atom catalyst onto a carbon felt, then making a filter device, and then continuously passing a mixed solution of organic pollutants and persulfate through the filter device to carry out a continuous degradation reaction.

[0017] The present invention discloses the following technical effects:

[0018] (1) The preparation method of the present invention is simple, has high yield and low cost, and is easy to prepare on a large scale. It is expected to provide a new idea for the high-value utilization of clay minerals and the large-scale synthesis of single-atom catalysts.

[0019] (2) The montmorillonite-based cobalt single-atom catalyst prepared in this invention has a high cobalt loading.

[0020] (3) The montmorillonite-based cobalt single-atom catalyst prepared in this invention can activate persulfate to remove various recalcitrant organic pollutants and has excellent degradation effect.

[0021] (4) The preparation method of the present invention can effectively inhibit the migration and aggregation of single atoms during the preparation process, improve the exposure rate of metal centers, i.e. active sites, and thus enhance the utilization rate, activity and stability of single-atom catalytic sites. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a scanning electron microscope image of the montmorillonite-based cobalt single-atom catalyst prepared in Example 1 of the present invention;

[0024] Figure 2 This is a transmission electron microscope image of the montmorillonite-based cobalt single-atom catalyst prepared in Example 1 of the present invention;

[0025] Figure 3 This is a high-angle annular dark-field scanning transmission electron microscope image of the montmorillonite-based cobalt single-atom catalyst prepared in Example 1 of the present invention, with spherical aberration correction.

[0026] Figure 4 The results of synchrotron radiation analysis are shown for the montmorillonite-based cobalt single-atom catalyst prepared in Example 1 of this invention.

[0027] Figure 5 The effect of the montmorillonite-based cobalt single-atom catalyst prepared in Example 1 of this invention on the continuous degradation of bisphenol A. Detailed Implementation

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0031] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0032] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0033] The montmorillonite used in this invention is sodium-based montmorillonite, with the molecular formula Na. 0.3 (Al,Mg)2Si4O 10 (OH)2·xH2O has the following composition: 22.14% Al2O3, 59.66% SiO2, 3.17% Fe2O3, 1.33% CaO, 2.22% MgO, 0.16% K2O, 3.15% Na2O, 0.87% TiO2, and 7.3% loss on ignition.

[0034] Example 1

[0035] A method for preparing a montmorillonite-based cobalt single-atom catalyst:

[0036] (1) Add 0.5g of montmorillonite, 0.05g of CoCl2·6H2O and agate balls of different sizes (3 10mm and 3 5mm) to a 50mL ball mill jar, and control the ball-to-material ratio to be 10:1.

[0037] (2) The ball mill was run at 300 rpm at room temperature, alternating between forward and reverse rotation. The running direction was changed every 60 min with an interval of 10 min. The ball milling was carried out for 12 h (total ball milling time) to obtain montmorillonite-based cobalt single-atom catalyst. The Co loading was 2.06 wt% as determined by ICP test.

[0038] The scanning electron microscope image of the montmorillonite-based cobalt single-atom catalyst prepared in this embodiment is shown below. Figure 1 Transmission electron microscope image (see) Figure 2 The high-angle annular dark-field scanning transmission electron microscope image with spherical aberration correction is shown below. Figure 3The results of the synchrotron radiation analysis are shown in [the table below]. Figure 4 .

[0039] from Figures 1-2 As can be seen from the above, the montmorillonite-based cobalt single-atom catalyst prepared in this embodiment exhibits a porous and layered structure, which can enhance the exposure and utilization of Co active sites.

[0040] from Figure 3 As can be seen, cobalt is uniformly dispersed in the montmorillonite matrix in the form of single atoms (without metallic bonds between Co atoms), and no obvious nanoclusters were observed.

[0041] from Figure 4 As can be seen, cobalt atoms exist in the montmorillonite aggregate in the form of Co-O6, without the presence of Co-Co bonds.

[0042] Example 2

[0043] A method for degrading organic pollutants:

[0044] (1) At room temperature, use ultrapure water to prepare a target pollutant stock solution with a concentration of 100 mg / L. Take 5 mL of the stock solution and add it to ultrapure water to dilute to 50 mL to obtain a target pollutant solution with a concentration of 10 mg / L.

[0045] (2) The montmorillonite-based cobalt single-atom catalyst (0.2 g / L) prepared in Example 1 and the oxidant PMS (potassium persulfate, 1 mM) were added to 50 mL of a target pollutant solution with a concentration of 10 mg / L. The mixture was thoroughly mixed and the degradation reaction was carried out at room temperature for 1 h. 1 mL samples were taken at 0, 1, 2, 3, 5, 7, 9, 15, 20, 30, 45, and 60 min, respectively. Simultaneously, 0.5 mL of methanol was added for quenching. The solution was filtered using a 0.22 μm PTFE needle filter and detected by high-performance liquid chromatography. The detection conditions and degradation performance of each pollutant are shown in Table 1.

[0046] Table 1. Detection conditions and degradation properties of each pollutant

[0047]

[0048] Table 1 shows the rate constant (K0) for pollutant degradation in PMS activated by montmorillonite-based cobalt single-atom catalysts. obs The time ranged from 0.225 to 3.188 min. -1 .

[0049] Example 3

[0050] A method for degrading organic pollutants:

[0051] (1) Tear the original carbon felt into small pieces to obtain carbon felt fragments.

[0052] (2) 200 mg of the montmorillonite-based cobalt single-atom catalyst prepared in Example 1 was mixed with 120 μL of Nafion in 3 mL of N,N-dimethylformamide to obtain a mixture.

[0053] (3) The mixture was added dropwise to 2.5g of carbon felt fragments, and then 5mL of methanol and 20mL of deionized water were added dropwise to the carbon felt until it was just soaked. The mixture was then sonicated for 1min to obtain carbon felt fragments loaded with montmorillonite-based cobalt single-atom catalyst.

[0054] (4) Carbon felt fragments loaded with montmorillonite-based cobalt single-atom catalyst were dried in an oven at 70°C for 24 hours. Finally, they were packed into a glass column with a diameter of 1 cm and a length of 20 cm. A mixed solution of 10 mg / L bisphenol A (BPA) and 1 mM PMS (PMS concentration in 10 mg / L bisphenol A is 1 mM) was continuously passed through the glass column from top to bottom for 1 hour at room temperature (the organic pollutant solution passing through the glass column does not need to be passed through again to achieve pollutant removal). This continuous operation was used to test the catalytic filter (Co-SAC / PMS / BPA). The results are shown in [Figure number missing]. Figure 5 .

[0055] Comparative Example 1

[0056] A method for degrading organic pollutants:

[0057] (1) Tear the original carbon felt into small pieces to obtain carbon felt fragments.

[0058] (2) 2.5g of carbon felt fragments were packed into a glass column with a diameter of 1cm and a length of 20cm. A mixed solution of 10mg / L bisphenol A (BPA) and 1mM PMS (the concentration of PMS in 10mg / L bisphenol A is 1mM) was continuously passed through the glass column (filter) from top to bottom for 1 hour at room temperature. This continuous operation was used to perform catalytic filter testing (PMS / BPA). The results are shown in […]. Figure 5 .

[0059] from Figure 5 As can be seen from the example, the bisphenol A removal rate remained at 100% within 1 hour using the method of Example 3, indicating that the montmorillonite-based cobalt single-atom catalyst prepared in Example 1 is expected to be applied to actual wastewater treatment.

[0060] Comparative Example 2

[0061] A method for degrading organic pollutants:

[0062] (1) Mix 0.5g of montmorillonite and 0.05g of CoCl2·6H2O evenly and put them into a porcelain boat. Pyrolyze at 600℃ for 2h with a heating rate of 10℃ / min to obtain the catalyst.

[0063] (2) Add the catalyst (addition amount of 0.2 g / L) prepared in step (1) and the oxidant PMS (potassium persulfate, addition amount of 1 mM) to 50 mL of bisphenol A solution with a concentration of 10 mg / L, mix well, and carry out the degradation reaction at room temperature for 1 h. Take 1 mL samples at 0, 1, 2, 3, 5, 7, 9, 15, 20, 30, 45 and 60 min respectively, and add 0.5 mL of methanol for quenching. Filter with a 0.22 μm PTFE needle filter and detect by high performance liquid chromatography.

[0064] The tests revealed that the degradation efficiency of bisphenol A within 60 minutes was 40–60% (montmorillonite-based Co single-atom catalysts achieved 100% degradation of bisphenol A within 3 minutes), with a rate constant of 0.0194–0.0387 min. -1 .

[0065] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a montmorillonite-based cobalt single-atom catalyst, characterized in that: The following steps are involved: The montmorillonite and the cobalt salt are mixed and then ball-milled to obtain the montmorillonite-based cobalt single-atom catalyst.

2. The preparation method according to claim 1, characterized in that: The cobalt salt includes cobalt chloride.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the montmorillonite to the cobalt salt is (5-20):

1.

4. The preparation method according to claim 1, characterized in that: The ball-to-material ratio of the ball mill is (5-10):1, the rotation speed is 300 rpm, the ball mill is rotated in both forward and reverse directions, the rotation direction of the ball mill is changed every 60 minutes, the interval time of the forward and reverse rotation ball mill is 10 minutes, and the total ball milling time is 8-12 hours.

5. A montmorillonite-based cobalt single-atom catalyst prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the montmorillonite-based cobalt single-atom catalyst according to claim 5 in activating persulfate to degrade organic pollutants.

7. A method for degrading organic pollutants, characterized in that: The method comprises the following steps: adding the montmorillonite-based cobalt single-atom catalyst and persulfate as claimed in claim 5 into an organic pollutant solution, mixing them evenly and then performing a degradation reaction.

8. The method for degrading organic pollutants according to claim 7, characterized in that: The dosage ratio of the organic pollutant, the montmorillonite-based cobalt single-atom catalyst and the persulfate in the organic pollutant solution is 10 mg: 0.1-0.3 g: 0.5-2 mmol.

9. A method for continuously degrading organic pollutants, characterized in that: The method comprises the following steps: loading the montmorillonite-based cobalt single-atom catalyst described in claim 5 on carbon felt, and then making a filtering device; and then continuously passing a mixed solution of organic pollutants and persulfate through the filtering device to perform a continuous degradation reaction.

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