A two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst, its preparation method, and its application.

Abstract

This invention discloses a two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst, its preparation method, and its applications. The invention involves etching the Al atomic layers in the MAX phase Ta4AlC3, then preparing a single-layer MXene material Ta4C3 through exfoliation, and finally generating Bi2WO6 nanospheres in situ on the Ta4C3 surface via a hydrothermal method to obtain the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst. This two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst enhances the electron transfer capability of Bi2WO6, broadens the visible light absorption wavelength range of Bi2WO6, reduces the electron-hole recombination rate, and improves photocatalytic performance. Under 60 min of illumination, the degradation efficiency of the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst reaches 65% for dodecylmorpholine, with no other energy consumption, making it safe and environmentally friendly. This is of great significance for the low-energy and pollution-free treatment of dodecylmorpholine, a flotation agent in salt lake brine.

Description

Technical Field

[0001] This invention belongs to the field of salt lake brine treatment and environmental protection, specifically relating to a two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst, its preparation method, and its application. Background Technology

[0002] Potash fertilizer is widely used in agriculture, providing strong support for increasing agricultural production. Currently, more than 70% of the world's potash fertilizer is produced using the foam flotation method. Morpholine flotation agents have become the primary flotation agents for potash extraction because they are used in relatively small quantities.

[0003] When using froth flotation to extract potassium, dodecylmorpholine and octadecylamine are added. The flotation effect is optimal when the carbon chain length of morpholine is between 12 and 18. As the carbon chain length of the flotation agent increases, it becomes increasingly difficult to degrade naturally. Allowing dodecylmorpholine to flow into water bodies will inevitably have a serious impact on the aquatic environment. Therefore, finding a green and efficient method for treating flotation agents is an important part of the subsequent treatment of potassium fertilizer production.

[0004] Currently, many factories use electrocatalysis to treat dodecylmorpholine contaminated liquid. However, this method has its limitations. The electrocatalytic process requires a continuous surge of current to the contaminated liquid, increasing treatment costs, wasting energy, and introducing new pollutants, causing secondary pollution. Therefore, it is necessary to explore a green and environmentally friendly method for treating dodecylmorpholine contaminated liquid.

[0005] Photocatalysis is a green technology that converts usable light energy into chemical energy. It has advantages such as no secondary pollution, simple operation, and mild reaction conditions, and is widely used in degradation, hydrogen production, and nitrogen fixation. The photocatalytic mechanism is that when a semiconductor material is exposed to sunlight, valence band monomers transition to the conduction band, forming electron-hole pairs. Holes in the valence band, having lost electrons, possess strong oxidizing power, while those in the conduction band, due to electron transitions, possess strong reducing power. Particles with excellent redox properties (·OH, O2ˉ, H2O2) are generated in both the valence and conduction bands, reacting with pollutants to degrade pollutants in water.

[0006] Although a large number of catalysts have been applied to environmental pollution treatment, there are very few photocatalysts for the degradation of dodecylmorpholine. Therefore, the use of photocatalysis to degrade dodecylmorpholine is challenging, the most important of which is the preparation of a highly efficient photocatalyst. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst, its preparation method, and its application, so as to improve the above-mentioned problems.

[0008] Specifically, Bi₂WO₆ is an n-type semiconductor that has attracted research attention due to its excellent visible light absorption properties. Its bandgap value E g Bi₂WO₆ has a voltage of 2.6-2.9 eV, low toxicity, is easy to prepare, possesses a deep valence band formed by the hybridization of Bi₆s and O₂p orbitals, and exhibits excellent chemical stability. However, the main drawbacks of pure semiconductors, including Bi₂WO₆, include photocorrosion, rapid recombination of photogenerated carriers, poor adsorption, low reusability, and low utilization of sunlight. To overcome these problems, various strategies have been employed, such as doping with metals and nonmetals and constructing heterojunctions.

[0009] MXene is a novel 2D material composed of transition metal carbides or nitrides, typically prepared by selectively etching atomic layers from its parent MAX phase using HF or a mixture of strong acids (HCl) and fluoride salts (NaF, LiF, and NH4F). Due to the abundance of hydrophilic functional groups (-OH, -O, and -F) on its surface, MXene can form robust connections with numerous semiconductors. Furthermore, MXene exhibits good metallic conductivity, enhancing carrier migration. Therefore, MXene holds great potential as a co-catalyst in photocatalysis. This invention utilizes a heterojunction constructed between Bi2WO6 and Ta4C3 to improve the photocatalytic performance of Bi2WO6. The combination of Bi2WO6 and the two-dimensional layered MXene material Ta4C3 increases the bandgap E. g The reduction and broadening of the visible light absorption wavelength range of Bi2WO6 effectively improves its light utilization efficiency. The increased specific surface area of ​​Bi2WO6 during the reaction process increases the number of surface reactive sites. Electrons in the valence band of Bi2WO6 can transfer to Ta4C3, reducing the recombination of photogenerated electrons and holes, increasing the lifetime of photogenerated electrons, and thus improving photocatalytic performance, thereby enhancing the degradation rate of dodecylmorpholine.

[0010] Based on the above ideas, the technical solution adopted by the present invention to solve its technical problem is as follows:

[0011] A method for preparing a two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst, comprising:

[0012] (1) Multilayer Ta4C3 was prepared by etching Al with MAX phase Ta4AlC3;

[0013] (2) The multilayer Ta4C3 prepared in step (1) is washed with deionized water and then intercalated with tetramethylammonium hydroxide. The resulting solution is washed with anhydrous ethanol until the supernatant does not turn yellow. Then it is washed with deionized water once more to obtain the washed multilayer Ta4C3.

[0014] (3) The multilayer Ta4C3 obtained by washing in step (2) is subjected to ice-water bath ultrasonication under inert gas protection, and layered Ta4C3 is obtained by centrifugation.

[0015] (4) Dissolve Bi(NO3)3·5H2O in ethylene glycol, add the layered Ta4C3 obtained in step (3) to obtain solution A;

[0016] (5) Dissolve Na2WO4·2H2O in deionized water and add polyvinylpyrrolidone to obtain solution B;

[0017] (6) Add solution B from step (5) to solution A, and adjust the pH value to 1.5-3.5 to obtain solution C;

[0018] (7) After stirring the solution C obtained in step (6) evenly, it is hydrothermally reacted at 150-165℃ for 16-24h. After cooling to room temperature, it is taken out, centrifuged, washed and vacuum dried to obtain a two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst.

[0019] In a preferred embodiment of the present invention, in step (1), the particle size of the MAX phase Ta4AlC3 used is 300-400 mesh; the etching uses an HF solution with a concentration of 40-45%, the volume of the HF solution is 30-50 ml, the etching temperature is 45-55°C, the stirring speed is 400-600 rpm / min, and the etching time is 24-72 h.

[0020] In a preferred embodiment of the present invention, in step (2), the washing is performed 6 to 8 times with deionized water, and the pH of the MXene suspension after washing is 5 to 6; 20 ml of 5 to 25% tetramethylammonium hydroxide is used for intercalation, and the intercalation time is 18 to 24 hours.

[0021] In a preferred embodiment of the present invention, in step (3), an inert gas is introduced during the ultrasonic mechanical peeling process, and the ultrasonic temperature is controlled to be below 20°C, and the ultrasonic time is 90 min to 120 min; the centrifugation conditions are 6500 to 8500 rpm / min, and the centrifugation time is 25 to 40 min.

[0022] In a preferred embodiment of the present invention, the inert gas is nitrogen.

[0023] In a preferred embodiment of the present invention, in step (5), the mass ratio of Bi2WO6 to layered Ta4C3 ranges from 90% to 99%.

[0024] In a preferred embodiment of the present invention, in step (7), the stirring rate is 150 rpm / min to 250 rpm / min, the stirring time is 25 min to 35 min, the washing method is alternating washing with water and ethanol, the vacuum drying temperature is 45 to 70°C, and the vacuum drying time is 18 to 24 h.

[0025] The present invention also provides a two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst prepared according to the above preparation method.

[0026] The present invention also provides an application of the above-mentioned two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst in the degradation of dodecylmorpholine in water.

[0027] In a preferred embodiment of the present invention, the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst is added to water containing dodecyl morpholine; wherein the ratio of the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst to water containing dodecyl morpholine is 0.09–0.13 g: 95–120 mL, the concentration of dodecyl morpholine in the water is 7.5–9.5 mmol / L, and the pH value of the water is 2.0–3.5;

[0028] The water body with added two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst was placed in the dark and stirred for 30-60 minutes, and then reacted under light for 60-90 minutes.

[0029] In this method, by placing the water body with the added two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst in the dark and stirring for 25 to 35 minutes, the catalyst and the solution can reach adsorption equilibrium.

[0030] In a preferred embodiment of the present invention, a 300W xenon lamp with a filter is used to simulate sunlight to provide a light source.

[0031] It should be noted that, unless otherwise specified, the equipment, reagents, processes, parameters, etc. involved in this invention are all conventional equipment, reagents, processes, parameters, etc., and no further examples will be provided.

[0032] All ranges listed in this invention include all point values ​​within that range.

[0033] In this invention, "room temperature" refers to the normal ambient temperature, which can be 10 to 30°C.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. This invention synthesizes a two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst by preparing a 2D layered MXene material Ta4C3, controlling the morphology of Bi2WO6, and constructing a heterojunction with Ta4C3. This catalyst generates highly efficient redox groups in water to degrade dodecylmorpholine.

[0036] 2. The catalytic material of the present invention is simple to prepare, easy to operate, and consumes little energy. Compared with existing DMP degradation catalysts, it has a better catalytic effect and is easy to recover. Attached Figure Description

[0037] Figure 1 The X-ray diffraction patterns of MAX phase Ta4AlC3, multilayer Ta4C3, and single-layer Ta4C3 in Embodiment 1 of the present invention are shown.

[0038] Figure 2 The X-ray diffraction pattern of the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst in Example 1 of the present invention is shown. The upper X-ray diffraction pattern represents the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst, and the lower X-ray diffraction pattern represents Bi2WO6.

[0039] Figure 3 The images are scanning electron microscope (SEM) images of the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst in Example 1 of the present invention, wherein a) is the MAX phase Ta4AlC3, b) is multilayered Ta4C3, c) is monolayered Ta4C3, d) is pure phase Bi2WO6, and e and f) are Ta4C3 / Bi2WO6 composites.

[0040] Figure 4 The image shows the performance curve of the photocatalytic degradation of dodecylmorpholine solution by the two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst in Example 1 of this invention.

[0041] Figure 5 The image shows the performance curve of the photocatalytic degradation of dodecylmorpholine solution by the two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst in Example 2 of this invention.

[0042] Figure 6 This is a cyclic degradation spectrum of dodecylmorpholine solution by photocatalytic degradation using a two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst in Example 2 of the present invention.

[0043] Figure 7 The band gap calculation spectrum of the two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst in Example 2 of the present invention is shown.

[0044] Figure 8The steady-state fluorescence spectrum of the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst in Example 2 of this invention is shown. Detailed Implementation

[0045] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0046] Example 1

[0047] This embodiment provides a method for preparing a two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst and a process for its photocatalytic degradation of 7–9 mmol / L dodecylmorpholine. Specifically:

[0048] (1) Multilayer Ta4C3 was prepared by etching Al with 40 mL of 40% HF at a constant temperature of 50 °C.

[0049] (2) Wash the multilayer Ta4C3 prepared in step (1) with deionized water 7 times until the pH value is greater than 5;

[0050] (3) The multilayer Ta4C3 washed in step (2) was subjected to an intercalation reaction of 20 mL of 5% tetramethylammonium hydroxide for 24 h;

[0051] (4) Wash the solution obtained after intercalation in step (3) with anhydrous ethanol until the supernatant does not turn yellow, and then wash it once with deionized water.

[0052] (5) The multilayer Ta4C3 obtained in step (4) was ultrasonicated in an ice-water bath for 120 min under N2 protection;

[0053] (6) The multilayer Ta4C3 sample prepared in step (5) was centrifuged at 6800 rpm / min for 30 min to obtain a single layer Ta4C3 dispersion, and then freeze-dried for 24 h to obtain a single layer Ta4C3 MXene material.

[0054] (7) Dissolve 0.9701g Bi(NO3)3·5H2O in 40mL ethylene glycol, add the layered Ta4C3 obtained in step (6) to make the mass ratio of Bi2WO6 to layered Ta4C3 25:1, sonicate for 15min and then stir for 120min at 150rpm / min to obtain solution A.

[0055] (8) Dissolve 0.3297g Na2WO4·2H2O in 20mL of deionized water and add 0.3g of polyvinylpyrrolidone. Stir at 150rpm / min for 120min to obtain solution B;

[0056] (9) Add solution B from step (8) to solution A, adjust the pH to 3 with glacial acetic acid to obtain solution C, and stir for 30 min;

[0057] (10) Pour solution C from step (9) into 100 mL of Teflon liner and hydrothermally react at 160 °C for 16 h. After cooling to room temperature, remove it, centrifuge and wash three times with deionized water and anhydrous ethanol, and then vacuum dry at 60 °C for 24 h to obtain a two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst.

[0058] (11) The prepared two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst was added to an 8 mmol / L dodecylmorpholine aqueous solution for photocatalytic degradation. During degradation, the reaction was first carried out in the dark for 30 min, and after the dark reaction was completed, the catalyst was irradiated under simulated sunlight conditions with a 300W Xe lamp for 60 min. Samples were taken every 10 minutes to test the degradation efficiency.

[0059] The X-ray diffraction pattern of the above-mentioned layered Ta4C3 is as follows: Figure 1 As shown, its diffraction characteristic peaks are Ta4C3 peaks. Compared with the MAX phase Ta4AlC3, the Al peaks disappear in the X-ray diffraction pattern of multilayer Ta4C3, leaving only the (002), (013), and (016) crystal planes, indicating that the Al atomic layers in MAX were successfully etched. Compared with multilayer Ta4C3, the 2θ angle of the (002) crystal plane of monolayer Ta4C3 decreases. According to the Bragg equation, a smaller diffraction angle indicates an increase in interplanar spacing, further demonstrating that multilayer Ta4C3 was successfully exfoliated into monolayer Ta4C3.

[0060] The X-ray diffraction pattern of the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst prepared above is shown in the figure. Figure 2 As shown, the prepared Bi2WO6, compared with its standard card, showed no impurity peaks and had sharp characteristic peaks, indicating high purity. Due to the composite of Bi2WO6 and Ta4C3, the diffraction peak intensity decreased compared to pure Bi2WO6 powder, indicating successful composite formation of Bi2WO6 and Ta4C3, thus demonstrating the successful preparation of the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst. Scanning electron microscopy images are shown below. Figure 3 As shown, where Figure 3 middle, Figure 3 a) It is a MAX phase Ta4AlC3, and the massive MAX phase parent body is at the micrometer scale. Figure 3 b) is MXene Ta4C3 that appears accordion-shaped after the Al atomic layer has been etched away. Figure 3 c) is the layered Ta4C3 after ultrasonic ablation. Figure 3 d) is the prepared Bi2WO6. Figure 3e) and Figure 3 f) is a Ta4C3 / Bi2WO6 complex, composed of... Figure 3 It can be seen that Bi2WO6 grows on the surface of Ta4C3.

[0061] The photocatalytic degradation of dodecylmorpholine was tested using a two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst. The degradation efficiency was determined by ultraviolet spectrophotometry. Results are as follows: Figure 4 As shown, Bi2WO6 alone exhibits a certain effect on degrading dodecylmorpholine, but the degradation effect is slow and the degradation efficiency is low. After the introduction of Ta4C3, the degradation effect and degradation rate are significantly improved, and the degradation effect reaches 38% within 60 min, indicating that the layered Ta4C3 / microsphere Bi2WO6 complex has a significant photocatalytic degradation effect on dodecylmorpholine.

[0062] Example 2

[0063] This embodiment modifies the mass ratio of Bi2WO6 to Ta4C3 to 100:3 based on Example 1. The two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst synthesized according to the preparation method of Example 1 was dispersed in 100 mL of 8 mmol / L dodecylmorpholine aqueous solution and reacted in the dark for 30 min to reach adsorption-desorption equilibrium. Under simulated sunlight irradiation with a 300W Xe lamp for 60 min, the calculated degradation efficiency was 64%, which is significantly improved compared to the monomer. This embodiment also conducted stability tests on the catalyst, and the tests were repeated.

[0064] like Figure 6 As shown, from Figure 6 It can be seen that the efficiency can still be above 50% after five cycles of degradation, indicating that the material has good photocatalytic performance.

[0065] like Figure 7 As shown, Figure 7 The calculated band gap spectrum of the two-dimensional layered Ta4C3-supported Bi2WO6 composite catalyst is shown. The calculation shows that the band gap of the monomer Bi2WO6 is 3.20 eV, while the band gap of the composite catalyst is 3.17 eV, indicating that the photoresponse range of Bi2WO6 is not changed after being combined with Ta4C3.

[0066] Next, steady-state fluorescence tests were performed on the prepared complex, such as... Figure 8 As shown, from Figure 8 The fluorescence intensity of the composite catalyst is lower than that of the pure phase, indicating that the recombination rate of electrons and holes in the composite catalyst is reduced, thereby improving the photocatalytic performance.

[0067] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a two-dimensional layered Ta4C3 supported Bi2WO6 composite catalyst, characterized by comprising the following steps: Comprise: ​ (1) The multi-layer Ta4C3 is prepared by etching Al on Ta4AlC3 of MAX phase; (2) The multi-layer Ta4C3 prepared in step (1) is washed with deionized water, and after intercalation with tetramethylammonium hydroxide, the obtained solution is washed with anhydrous ethanol until the supernatant is not yellow, and then washed with deionized water once to obtain the washed multi-layer Ta4C3; (3) The multi-layer Ta4C3 obtained by washing in step (2) is subjected to ice water bath ultrasonic under inert gas protection, and layered Ta4C3 is obtained by centrifugation; (4) Bi(NO3)3·5H2O is dissolved in ethylene glycol, and the layered Ta4C3 prepared in step (3) is added to obtain solution A; (5) Na2WO4·2H2O is dissolved in deionized water and polyvinylpyrrolidone is added to obtain solution B; (6) Solution B in step (5) is added dropwise to solution A, and the pH value is adjusted to 1.5-3.5 to obtain solution C; (7) After the solution C obtained in step (6) is uniformly stirred, hydrothermal reaction is carried out at 150-165 ℃ for 16-24 h, and after cooling to room temperature, it is taken out, washed by centrifugation and vacuum dried to obtain two-dimensional layered Ta4C3 loaded Bi2WO6 composite catalyst.

2. The method of claim 1, wherein: In step (1), the particle size of the used MAX phase Ta4AlC3 is 300-400 mesh; the etching uses HF solution with a concentration of 40-45%, the volume of HF solution is 30-50 ml, the etching temperature is 45-55℃, the stirring speed is 400-600 rpm / min, and the etching time is 24-72 h.

3. The method of claim 1, wherein: In step (2), the deionized water is washed for 6-8 times, and the pH of the MXene suspension after washing is 5-6; 20 ml of 5-25% tetramethylammonium hydroxide is used for intercalation, and the intercalation time is 18-24 h.

4. The method of claim 1, wherein: In step (3), inert gas is introduced during ultrasonic mechanical exfoliation, and the ultrasonic temperature is controlled below 20℃, the ultrasonic time is 90 min-120 min; the centrifugal condition is 6500-8500 rpm / min, the centrifugal time is 25-40 min; and the inert gas is nitrogen.

5. The method of claim 1, wherein: In the step (5), the mass ratio of Bi2WO6 to layered Ta4C3 is in the range of 90% to 99%.

6. The method of claim 1, wherein: In the step (7), the stirring rate is 150 rpm / min to 250 rpm / min, and the stirring time is 25 min to 35 min; the washing method is alternating washing with water and ethanol, the vacuum drying temperature is 45-70℃, and the vacuum drying time is 18-24 h.

7. A two-dimensional layered Ta4C3 loaded Bi2WO6 composite catalyst prepared by the preparation method of any one of claims 1-6.

8. The use of the two-dimensional layered Ta4C3 loaded Bi2WO6 composite catalyst of claim 7 in degrading dodecylmorpholine in water.

9. Use according to claim 8, characterized in that, Comprise: The two-dimensional layered Ta4C3 loaded Bi2WO6 composite catalyst is added into a water body containing dodecylmorpholine; wherein, the ratio of the two-dimensional layered Ta4C3 loaded Bi2WO6 composite catalyst to the water body containing dodecylmorpholine is 0.09-0.13 g: 95-120 mL, the concentration of the dodecylmorpholine in the water body is 7.5-9.5 mmol / L, and the pH value of the water body is 2.0-3.5; The water body after adding the two-dimensional layered Ta4C3 loaded Bi2WO6 composite catalyst is stirred in dark for 30-60 min, so that the two-dimensional layered Ta4C3 loaded Bi2WO6 composite catalyst and the water body reach adsorption equilibrium. The solution after adsorption equilibrium is reacted under light irradiation for 60-90 min.

10. Use according to claim 9, characterized in that: A 300 W xenon lamp plus a filter is used to simulate sunlight irradiation to provide the light irradiation condition.

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