A kaolin / cobalt oxide composite catalyst, a preparation method and application thereof

Abstract

The application discloses a kaolin / cobalt oxide composite catalyst and a preparation method and application thereof. The application relates to the technical field of catalysts. The preparation method of the kaolin / cobalt oxide composite catalyst comprises the following steps: S1, growing cobalt hydroxide precursors on the surface of kaolin by using an oil bath method; and S2, calcining the kaolin / cobalt hydroxide precursors to obtain the kaolin / cobalt oxide composite catalyst. In the application, the abundant Al hydroxyl groups on the surface of the kaolin can be used as anchor points of the catalyst, the cobalt oxide can be uniformly dispersed on the surface of the kaolin through a precursor calcination method, and meanwhile, the strong interaction between the kaolin and the cobalt oxide can regulate the electronic structure of the cobalt oxide, so that the catalytic performance of the cobalt oxide is improved.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a kaolin / cobalt oxide composite catalyst, its preparation method, and its application. Background Technology

[0002] There is an urgent need to treat organic pollutants in water. Fenton oxidation is a common industrial method for treating organic wastewater; its principle is to utilize Fe under acidic conditions. 2+ The Fenton oxidation process catalyzes the oxidation of H₂O₂ to generate highly oxidizing ·OH, which in turn degrades organic matter. While the Fenton oxidation method boasts advantages such as simple operation, low cost, fast reaction rate, and high efficiency, some drawbacks still limit its widespread application. For example, in an alkaline environment, Fe... 2+ and Fe 3+ Iron sludge is easily formed, reducing degradation efficiency and causing secondary pollution. Therefore, heterogeneous catalytic systems have been developed to improve this drawback, for example, by preparing solid Fe-based catalysts with Fe as the active center. 2+ It is fixed on the catalyst surface. In addition, some non-Fe transition metal heterogeneous catalysts (Cu, Mn, Co, etc.) have also been used to activate hydrogen peroxide.

[0003] Although many heterogeneous catalysts have been developed, their efficiency in activating hydrogen peroxide to generate hydroxyl radicals is relatively low. Therefore, further improvements are needed. Replacing Fe with an electrochemical reaction could be a solution. 2+ Activating hydrogen peroxide not only solves the problem of iron sludge formation in the Fenton oxidation process under alkaline conditions but also further accelerates the reaction rate. The key lies in preparing a high-performance electrocatalyst to convert hydrogen peroxide into hydroxyl radicals. Cobalt oxide is a common electrocatalyst that can activate hydrogen peroxide to generate hydroxyl radicals through electrochemical reactions, but its hydroxyl radical yield is low. Therefore, regulating cobalt oxide is crucial for preparing cobalt oxide-based high-performance electrocatalysts. Summary of the Invention

[0004] The purpose of this invention is to address the low yield of hydroxyl radicals generated by cobalt oxide-activated hydrogen peroxide in existing technologies, and to propose a simple, low-cost, and high-performance electro-Fenton catalyst, namely a kaolin / cobalt oxide composite catalyst, along with its preparation method and applications.

[0005] The present invention discloses a method for preparing a kaolin / cobalt oxide composite catalyst, comprising the following steps:

[0006] S1. Cobalt hydroxide precursor is grown on the surface of kaolin using an oil bath method;

[0007] S2. The kaolin / cobalt hydroxide precursor is calcined to obtain the kaolin / cobalt oxide composite catalyst.

[0008] Further, the specific operation of step S1 is as follows: Kaolin or modified kaolin, anhydrous cobalt chloride, and urea are ultrasonically dispersed in deionized water, and the solution is washed by centrifugation after oil bath and dried to obtain kaolin / cobalt hydroxide precursor.

[0009] Furthermore, the mass ratio of the kaolin or modified kaolin, anhydrous cobalt chloride, and urea is 100:11-88:10-80.

[0010] Further, the solution is placed in an oil bath at 110°C for 2-4 hours; and / or dried at 70-80°C.

[0011] Furthermore, the modified kaolin was prepared by the following method: kaolin was calcined at 400℃~700℃ for 3h, and after the reaction cooled to room temperature, the sample was taken out to obtain the modified kaolin.

[0012] Furthermore, the heating rate was set to 5℃·min. -1 ,

[0013] Furthermore, in step S2, the sample is calcined at 400℃~500℃ for 2-4 hours.

[0014] Furthermore, the heating rate was set to 5℃·min. -1 .

[0015] A kaolin / cobalt oxide composite catalyst prepared by the above-described preparation method.

[0016] An application of the kaolin / cobalt oxide composite catalyst as described above is to use the kaolin / cobalt oxide composite catalyst as a catalyst for the electrochemical activation of H2O2.

[0017] In this invention, the abundant Al hydroxyl groups on the surface of kaolin can serve as anchor points for catalysts. Cobalt oxide can be uniformly dispersed on the surface of kaolin through precursor calcination. At the same time, the strong interaction between kaolin and cobalt oxide can regulate the electronic structure of cobalt oxide, thereby improving the catalytic performance of cobalt oxide.

[0018] The kaolin / cobalt oxide composite electrocatalyst prepared in this invention has excellent performance and can significantly improve the hydroxyl radical yield of cobalt oxide. In this invention, H2O2 is activated by electrochemical method, which is highly efficient and environmentally friendly. In the presence of 40mM H2O2 in solution, it can degrade 90% of Orange II (50mL solution, concentration of 20mg / L) in 30min. Attached Figure Description

[0019] Figure 1 X-ray powder diffraction pattern of kaolin;

[0020] Figure 2X-ray powder diffraction pattern of cobalt oxide;

[0021] Figure 3 Example 5: X-ray powder diffraction pattern of the composite catalyst;

[0022] Figure 4 X-ray photoelectron spectrum of Al2p kaolinite;

[0023] Figure 5 X-ray photoelectron spectrum of cobalt oxide (Co2p);

[0024] Figure 6 Example 5: X-ray photoelectron spectrum of the catalyst Al2p;

[0025] Figure 7 Example 5: X-ray photoelectron spectrum of the catalyst Co2p;

[0026] Figure 8 Example 1: Effect diagram of pollutant degradation by composite catalyst;

[0027] Figure 9 Example 2: Effect diagram of pollutant degradation by composite catalyst;

[0028] Figure 10 Example 3: Effect diagram of pollutant degradation by composite catalyst;

[0029] Figure 11 Example 4: Effect diagram of pollutant degradation by composite catalyst;

[0030] Figure 12 Example 5: Effect diagram of pollutant degradation by composite catalyst;

[0031] Figure 13 Diagram showing the effect of cobalt oxide in degrading pollution. Detailed Implementation

[0032] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0033] Example 1: The preparation method of a modified kaolin / cobalt oxide composite catalyst according to this embodiment is completed according to the following steps:

[0034] Step 1

[0035] First, 0.500g of kaolin, 0.055g of anhydrous cobalt chloride, and 0.050g of urea were dispersed in 80mL of deionized water and sonicated for 30min. Then, the solution was placed in an oil bath at 110℃ for 3h. After the oil bath was completed, the sample was washed by centrifugation and dried at 80℃ to obtain the kaolin / cobalt hydroxide precursor.

[0036] Step Two

[0037] The prepared kaolin / cobalt hydroxide precursor was placed in a muffle furnace and calcined at 500℃ for 3 hours, with a heating rate of 5℃·min. -1 After the reaction cooled to room temperature, the sample was removed to obtain the kaolin / cobalt oxide composite catalyst.

[0038] Example 2

[0039] The difference between this embodiment and Example 1 is that the kaolin used in step one is modified kaolin, the modification method is calcination, the calcination temperature is 500℃, the time is 3 hours, and the heating rate is 5℃·min. -1 The other steps are the same as in Example 1.

[0040] Example 3

[0041] The difference between this embodiment and Example 1 is that the kaolin used in step one is modified kaolin, the modification method is calcination, the calcination temperature is 700℃, the time is 3 hours, and the heating rate is 5℃·min. -1 The other steps are the same as in Example 1.

[0042] Example 4

[0043] The difference between this embodiment and Example 1 is that the mass of anhydrous cobalt chloride in step one is 0.110g, and the mass of urea is 0.100g. The other steps are the same as in Example 1.

[0044] Example 5

[0045] In this embodiment and example: the mass of anhydrous cobalt chloride in step one is 0.220g, and the mass of urea is 0.200g. Other steps are the same as in Example 1.

[0046] Example 6

[0047] The difference between this embodiment and Example 1 is that the mass of anhydrous cobalt chloride in step one is 0.440g, and the mass of urea is 0.400g. The other steps are the same as in Example 1.

[0048] Example 7

[0049] The difference between this embodiment and Example 1 is that the oil bath time in step one is 2 hours. All other steps are the same as in Example 1.

[0050] Example 8

[0051] The difference between this embodiment and Example 1 is that the oil bath time in step one is 4 hours. All other steps are the same as in Example 1.

[0052] Example 9

[0053] The difference between this embodiment and Example 1 is that the calcination time in step two is 2 hours. All other steps are the same as in Example 1.

[0054] Example 10

[0055] The difference between this embodiment and Example 1 is that the calcination time in step two is 4 hours. All other steps are the same as in Example 1.

[0056] Example 11

[0057] The difference between this embodiment and Example 1 is that the calcination temperature in step two is 400°C. All other steps are the same as in Example 1.

[0058] Comparative Example

[0059] The method for preparing pure cobalt oxide in this embodiment is completed according to the following steps:

[0060] Step 1

[0061] First, 0.440 g of anhydrous cobalt chloride and 0.400 g of urea were dispersed in 80 mL of deionized water and sonicated for 30 min. Then, the solution was placed in an oil bath at 110 °C for 3 h. After the oil bath was completed, the sample was centrifuged and washed, and dried at 80 °C to obtain the cobalt hydroxide precursor.

[0062] Step Two

[0063] The prepared cobalt hydroxide precursor was placed in a muffle furnace and calcined at 500℃ for 3 hours, with a heating rate of 5℃·min. -1 After the reaction cooled to room temperature, the sample was removed, and pure cobalt oxide was obtained.

[0064] Application Example: Electrocatalytic Degradation of Orange II

[0065] The electrocatalytic activity of the kaolin / cobalt oxide composite catalyst was evaluated using Orange II as the pollutant. The electrocatalytic degradation reaction was carried out in an electrolytic cell using a three-electrode system: a carbon rod as the counter electrode, a silver-silver chloride electrode as the reference electrode, and an inductively coupled conductive glass (ITO) electrode supporting the catalyst as the working electrode. The preparation procedure for the working electrode was as follows: First, 10 mg of catalyst was added to 1 mL of ethanol, followed by 20 μL of Nafion (5%) solution, and sonicated for 30 min. Then, 100 μL of the electrode slurry was coated onto the ITO, with a coating area of ​​1 × 2 cm². 2Then allow it to air dry naturally before use. Before testing, prepare 50 mL of 20 mg / L Orange II solution, then add 0.355 g of Na2SO4 (0.05 M), and adjust the pH of the solution to 10 with potassium hydroxide. After adding 0.205 mL (40 mM) of H2O2, start the test. The time-current method was used for testing, with the potential set to -0.59 V (vs Ag / AgCl), and the test duration was 30 min. At regular intervals, 1 mL of sample was taken from the electrolytic cell using a syringe to measure the absorbance. The absorbance was measured on a visible spectrophotometer at a wavelength of 484 nm.

[0066] The structural characterization method for the kaolin / cobalt oxide composite catalyst was as follows: X-ray diffraction (XRD) was used to analyze the crystal structure and composition of the material using a Bruker D8 Advance instrument. During testing, the X-ray source was Al Kα rays, the scanning range was 5°–90°, and the scanning speed was 5° / min. Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemical bond structure of the material using a Thermo Scientific Nicolet instrument. The changes in surface functional groups and chemical bonds were analyzed by examining the peak positions and intensities of the infrared spectra. The testing range was 400 cm⁻¹. -1 -4000cm -1 .

[0067] Figure 1 , Figure 2 , Figure 3 The images show the XRD patterns of pure kaolin, pure cobalt oxide, and the composite catalyst of Example 5, respectively. Figure 3 In Example 5, the diffraction peaks belonging to cobalt oxide appeared on the spectrum of kaolinite / cobalt oxide-20%, and the diffraction peaks of kaolinite were still present, indicating that cobalt oxide was successfully synthesized on the surface of kaolinite.

[0068] Figures 4 to 7 The images show the XPS spectra of Al2p of pure kaolin, Co2p of pure cobalt oxide, and Al2p and Co2p of the composite catalyst in Example 5. These spectra show that there is electron transfer between kaolin and cobalt oxide, with electrons from cobalt oxide being transferred to kaolin. This indicates that kaolin can regulate the electron density of cobalt oxide through interfacial interactions.

[0069] Figures 8 to 12The figures show the degradation effects of the composite catalysts in Examples 1 to 5. As can be seen from the figures, the surface loading of cobalt oxide on kaolin can affect the catalytic performance. The degradation effect is better when the loading of cobalt oxide is 5% and 10%, but the performance decreases when the loading is increased to 20%. The catalytic performance of cobalt oxide can be further improved by calcining and modifying kaolin. The composite catalyst prepared in Example 3 has the best performance and can degrade 90% of Orange II in 30 minutes. Figure 13 The degradation effect of pure cobalt oxide is shown; only 40% of Orange II can be degraded in 30 minutes. The improved degradation effect indicates that kaolin can significantly increase the hydroxyl radical yield of pure cobalt oxide, thereby improving the pollutant degradation effect.

[0070] For any points not covered above, existing technologies shall apply.

[0071] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. An application of a kaolin / cobalt oxide composite catalyst, characterized in that: Kaolin / cobalt oxide composite catalyst was used as a catalyst for electrochemical activation of H2O2; The preparation method of the kaolin / cobalt oxide composite catalyst includes the following steps: S1. Cobalt hydroxide precursor is grown on the surface of kaolin using an oil bath method; S2. The kaolin / cobalt hydroxide precursor was calcined at 400 °C~500 °C for 2-4 h to obtain the kaolin / cobalt oxide composite catalyst.

2. The method for preparing a kaolin / cobalt oxide composite catalyst as described in claim 1, characterized in that: The specific operation of step S1 is as follows: Kaolin, anhydrous cobalt chloride, and urea are ultrasonically dispersed in deionized water, the solution is washed by centrifugation after oil bath, and dried to obtain kaolin / cobalt hydroxide precursor.

3. The method for preparing a kaolin / cobalt oxide composite catalyst as described in claim 2, characterized in that: The mass ratio of kaolin, anhydrous cobalt chloride, and urea is 100:11 ~ 88:10 ~ 80.

4. The method for preparing a kaolin / cobalt oxide composite catalyst as described in claim 2, characterized in that: The solution is placed in an oil bath at 110 °C for 2-4 h; and / or dried at 70-80 °C.

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