A wO3 / g-c3n4@ws2 ternary photocatalyst, a preparation method and application thereof

Abstract

The application provides a WO3 / g-C3N4@WS2 ternary photocatalyst and a preparation method and application thereof.The WO3 / g-C3N4@WS2 ternary photocatalyst of the application enhances the electron transfer capacity of the catalyst by constructing a heterojunction, reduces the recombination rate of electron-hole pairs, enhances the catalytic capacity, realizes effective degradation of dodecylmorpholine in water, and does not consume extra energy by using sunlight as energy, and does not cause secondary pollution to water.The application is particularly suitable for treating dodecylmorpholine in water, and has the advantages of simple method, remarkable effect, safety and environmental protection, and has important significance for low-energy-consumption and pollution-free treatment of the floatation agent dodecylmorpholine in salt lake brine.

Description

Technical Field

[0001] This invention belongs to the field of salt lake brine treatment and environmental protection, specifically involving a WO3 / g-C3N4@WS2 ternary photocatalyst, its preparation method, and its application. Background Technology

[0002] Potassium is a crucial element in crops, and its deficiency poses a significant threat to food security. Therefore, alleviating potassium shortages through various means is of great importance. Cold crystallization reverse flotation is a widely used method for potassium production. The main flotation agents used in this method are fatty amides and alkyl morpholines. Amide flotation agents require auxiliary reagents and are used in large quantities, thus their use is less common. Morpholine flotation agents, on the other hand, are used in relatively small quantities, making them the primary flotation agents in potassium salt reverse flotation processes. Experiments have shown that alkyl morpholines with a carbon chain length of 12-18 exhibit the best flotation effect. Based on this, dodecyl morpholine (DMP) is widely used in the production of potash fertilizer from salt lakes. However, due to its long carbon chain, DMP exhibits good stability in water and is difficult to degrade. Allowing DMP to accumulate in water can cause serious harm to the environment and ecology, and severely pollute mineral deposits. Therefore, finding a suitable DMP treatment solution is a crucial step in the subsequent treatment of potash fertilizer.

[0003] Currently, factories mostly use electrocatalytic methods to treat industrial wastewater containing DMP, namely dielectric barrier discharge plasma. However, this method has the following drawbacks: First, the electrocatalytic method is more expensive, as the electrocatalytic process continuously applies a strong current to the wastewater, consuming a large amount of energy; second, a large amount of Cr-containing substances must be added during the reaction. 3+ Fe 3+ The solution can cause secondary pollution. Given the shortcomings of electrocatalytic reactions, it is necessary to develop an environmentally friendly and sustainable technology to address these problems.

[0004] Photocatalysis technology is widely used in environmental pollution control due to its green and environmentally friendly nature, mild reaction conditions, simple operation, and low processing cost. The mechanism of photocatalytic oxidation-reduction mainly involves the catalyst absorbing light energy upon exposure to light, undergoing electron transitions to generate electron-hole pairs. These pairs directly oxidize or reduce pollutants adsorbed on the surface, or oxidize OH- ions on the surface to generate highly oxidizing hydroxyl radicals (·OH) or superoxide radicals (·O2). -Photocatalysis oxidizes pollutants. Among them, graphitic carbon nitride (g-C3N4) is composed of abundant carbon and nitrogen elements on Earth. It is also widely used as a photocatalyst that is easy to prepare and has good morphological characteristics. Studies have shown that the band gap of g-C3N4 is about 2.7 eV under normal conditions. Therefore, it can absorb not only ultraviolet light energy but also visible light energy. In addition, it is stable and easy to recycle, and can be used for photocatalytic degradation of organic pollutants.

[0005] The unique properties of semiconductor catalytic materials are directly influenced by their morphology, size, and even dimensionality. Current research primarily focuses on adding active groups to the surface of g-C3N4 at the nanoscale to create two-dimensional sheet-like nanoparticles. This increases the number of active sites on the surface, reduces electron-hole recombination, and increases the specific surface area of ​​the catalyst, thereby increasing the contact area with reactants and the reaction probability. Another research direction involves combining g-C3N4 with other photocatalysts to form heterojunctions. This alters the electron-hole transfer pathways, reducing electron-hole recombination on the surface and effectively improving electron-hole transfer efficiency, thus stabilizing carrier concentration. However, g-C3N4 materials still have some limitations, such as high electron-hole recombination and small specific surface area in single-material form.

[0006] In Z-type heterojunctions, the different Fermi levels of the two contact semiconductors lead to an internal electric field between the interfaces, driving the migration of photogenerated carriers. Furthermore, the Z-type heterojunction system results in a two-photon excitation process and a unique electron transfer path, thus ensuring the redox capability of the photogenerated charge. Z-type structures based on g-C3N4 are designed to suppress photogenerated electron and hole recombination; however, the inability to collect negatively charged photogenerated electrons limits photogenerated electron transport in g-C3N4 Z-type systems. Recently, noble metals such as platinum particles have been widely studied for collecting photogenerated electrons due to their proton adsorption capabilities (the Gibbs free energy (ΔGH*) of hydrogen adsorption is close to zero). Transition metal sulfide (TMD) materials (WS2, MoS2, WSe2, MoSe2, etc.) have unsaturated active atoms located at exposed edges, which can react with H+ in solution. + Combined, and then exhibiting a favorable effect on H + Reduced platinum-like behavior. Combining TMDs materials with Z-shaped heterostructures can effectively promote charge carrier separation and proton absorption, such as MoS2 / CaTiO3 and Cu2-xS / Mn. 0.5 Cd 0.5 S / MoS2, WS2 / MoS2@WO 3-xThe conduction band (CB) of WS2 relative to the NHE (normal hydrogen electrode) is -1.03 V, and its energy level is lower than that of g-C3N4. The suitable band arrangement between WS2 and g-C3N4 forms an effective WS2 / g-C3N4 heterojunction, which promotes the rapid transfer of photogenerated electrons.

[0007] Although photocatalytic degradation of pollutants in water has been applied in many fields, methods for treating dodecylmorpholine, a flotation agent, in salt lake brine using photocatalysis are relatively rare. Therefore, the key to the technology of photocatalyst degradation of dodecylmorpholine lies in synthesizing a highly efficient photocatalyst for this purpose. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a WO3 / g-C3N4@WS2 ternary photocatalyst, its preparation method, and its application, so as to improve the above-mentioned problems.

[0009] A method for preparing a WO3 / g-C3N4@WS2 ternary photocatalyst, comprising:

[0010] (1) Add dicyandiamide powder to a beaker and add an appropriate amount of WS2 powder to the beaker;

[0011] (2) Add an appropriate amount of deionized water and H2SO4 to the material obtained in step (1) and stir in an oil bath;

[0012] (3) Grind the material obtained in step (2) until there is no obvious particle feel, and then calcine it;

[0013] (4) Grind the material obtained from calcination in step (3) to obtain the flaky composite g-C3N4@WS2;

[0014] (5) Dissolve Na2WO4•H2O in water and add the flake g-C3N4@WS2 prepared in step (4) to obtain solution A;

[0015] (6) Add HCl solution to solution A obtained in (5) to adjust the pH value to 1.9-2.1, then add water to obtain solution B;

[0016] (7) Add glacial acetic acid to solution B to adjust the pH to 2.2-2.4, then stir well;

[0017] (8) The solution B was subjected to hydrothermal reaction at 155-165℃ for 14-18 h. After cooling to room temperature, it was taken out, centrifuged, washed and vacuum dried to obtain WO3 / g-C3N4@WS2 ternary photocatalyst.

[0018] Preferably, in step (2), the amount of H2SO4 added is 3-5 ml, the stirring temperature of the oil bath is 50℃-60℃, the stirring time is 20 h-24 h, and the stirring rate is 150~200 r / min.

[0019] Preferably, in step (3), the heating rate of calcination is 4-6℃ / min, and the temperature is maintained for 3-5 hours after reaching 545-555℃.

[0020] Preferably, the concentration of the HCl solution in step (6) is 1-2 mol / L, and the mass ratio of WO3 to g-C3N4@WS2 in solution A is 90%.

[0021] Preferably, the stirring rate in step (7) is 150-250 r / min and the stirring time is 20-40 min.

[0022] Preferably, in step (8), the washing method is to wash repeatedly with water and alcohol alternately; the vacuum drying temperature is 45-55℃, and the vacuum drying time is 22-26 h.

[0023] This invention also provides a WO3 / g-C3N4@WS2 ternary photocatalyst prepared according to the above preparation method.

[0024] This invention also provides an application of the WO3 / g-C3N4@WS2 ternary photocatalyst prepared above in the degradation of dodecylmorpholine in water.

[0025] Preferably, the WO3 / g-C3N4@WS2 ternary photocatalyst is added to water containing dodecylmorpholine, stirred in the dark for 25-35 min, and then reacted under light for 50-70 min.

[0026] One method is to use a 300W xenon lamp with a filter to simulate sunlight and provide a light source.

[0027] Preferably, the ratio of the WO3 / g-C3N4@WS2 ternary photocatalyst to water containing dodecylmorpholine is 0.08–0.12 g: 90–110 mL, the concentration of dodecylmorpholine in the water is 7–9 mmol / L, and the pH of the water is 3.0–3.2.

[0028] 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.

[0029] All ranges listed in this invention include all point values ​​within that range.

[0030] In this invention, "room temperature" refers to the normal ambient temperature, which can be 10 to 30°C.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] A photocatalyst was developed by combining modified WO3, graphite-type g-C3N4, and WS2. WO3 and g-C3N4 formed a Z-shaped heterojunction, and WS2, as a co-catalyst, increased the light absorption capacity of the catalyst, thereby improving the catalytic performance of the material and enhancing the degradation efficiency of dodecylmorpholine. Furthermore, this method does not produce any excess pollutants that contaminate the water body, effectively degrading small amounts of dodecylmorpholine in the water and preventing the dodecylmorpholine from damaging or polluting mineral deposits in the water, thus achieving the goal of environmental protection.

[0033] Furthermore, the preparation method of the present invention is simple to operate, has high quality and good repeatability. Compared with the existing DMP degradation technology, it has higher efficiency, no secondary pollution, and the catalyst is easy to recover and reuse. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 The X-ray diffraction pattern of the WO3 / g-C3N4@WS2 ternary photocatalyst in Example 1 of this invention is shown.

[0036] Figure 2 a) ~ Figure 2 c) is a scanning electron microscope image of the WO3 / g-C3N4@WS2 ternary photocatalyst in Example 1 of the present invention.

[0037] Figure 3 The graph shows the photocatalytic degradation performance of dodecylmorpholine solution by the WO3 / g-C3N4@WS2 ternary photocatalyst in Example 1 of this invention.

[0038] Figure 4 This is a cyclic degradation spectrum of dodecylmorpholine solution by photocatalysis using the WO3 / g-C3N4@WS2 ternary photocatalyst in Example 1 of the present invention.

[0039] Figure 5 The photocurrent response curve of the WO3 / g-C3N4@WS2 ternary photocatalyst in Example 1 of this invention is shown.

[0040] Figure 6Impedance curve of WO3 / g-C3N4@WS2 ternary photocatalyst in Example 1 of this invention.

[0041] Figure 7 The graph shows the photocatalytic degradation performance of dodecylmorpholine solution by the WO3 / g-C3N4@WS2 ternary photocatalyst in Example 2 of this invention. Detailed Implementation

[0042] 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.

[0043] Example 1

[0044] A method for preparing a WO3 / g-C3N4@WS2 ternary photocatalyst, the preparation steps are as follows:

[0045] (1) Take 8 g of dicyandiamide powder and place it in a beaker, then add 0.8 g of WS2 powder;

[0046] (2) Add 60ml of deionized water and 3ml of H2SO4 to the beaker in step (1) and stir in an oil bath at 60℃ for 24h;

[0047] (3) The material obtained in step (2) is ground in an agate mortar until there is no obvious particle feel, and then a dicyandiamide powder loaded with WS2 with a flake-like morphology is obtained.

[0048] (4) The material obtained in step (3) is first placed in a crucible, then the crucible is placed in a muffle furnace and the heating program is set to 5℃ / min. The temperature is continuously increased to 550℃ and held at 550℃ for 4 h to prepare g-C3N4@WS2.

[0049] (5) Take a clean beaker, dissolve 1.65 g of Na2WO4•H2O in 10 mL of deionized water, and add 0.23 g of g-C3N4 powder obtained in step (3) to make the theoretical mass ratio of WO3 to g-C3N4 composite 9:1 to obtain solution A.

[0050] (6) Add 2 mol / L HCl solution to solution A obtained in (5) until the pH value of the solution is 2.0, and then add 50 mL of deionized water to obtain solution B;

[0051] (7) Add glacial acetic acid to solution B until the pH value of the solution is 2.3, and then stir for 30 min.

[0052] (8) After stirring, the B solution was transferred to a hydrothermal reactor and reacted in an oven at 160°C for 16 h. After cooling to room temperature, the solution was taken out, washed with deionized water and alcohol by alternating centrifugation, and vacuum dried for 24 h to obtain rod-shaped WO3 / g-C3N4@WS2 ternary photocatalyst.

[0053] The various properties of the prepared WO3 / g-C3N4@WS2 ternary photocatalyst were then tested.

[0054] First, the WO3 / g-C3N4@WS2 ternary photocatalyst prepared above was added to water containing 8 mmol / L DMP for photocatalytic degradation. After a 30-minute dark reaction to allow the catalyst adsorption to reach equilibrium, the light source was turned on for 60 minutes of irradiation. Samples were taken every 10 minutes to test the degradation rate.

[0055] The X-ray diffraction patterns of the above materials are as follows: Figure 1 As shown, WS2 exhibits a distinct characteristic peak at 14.3°, consistent with the standard card PDF#6575-15, which corresponds to the (002) crystal plane of WS2. The absence of extraneous peaks indicates high purity of the WS2 used. After deposition and calcination, g-C3N4@WS2 shows a distinct characteristic peak belonging to WS2 at 14.3°, and a broad peak representing g-C3N4 at 27°, indicating successful composite formation of the two materials after calcination. Following hydrothermal reaction of g-C3N4@WS2, the presence of a characteristic peak of WO3 and the retention of the WS2 characteristic peak at 14.3° demonstrates successful growth of WO3 on the g-C3N4@WS2 surface after hydrothermal treatment.

[0056] Figure 2 Scanning electron microscopy (SEM) images of WS2, g-C3N4@WS2, and WO3 / g-C3N4@WS2 series complexes are provided, and their morphological characteristics are analyzed using SEM images. Figure 2 a) The WS2 block structure shows layering and stacking to form a thick layered structure, with the block size being around 5 μm. Figure 2 (b) The g-C3N4@WS2 sample obtained after calcination exhibits a sheet-like structure with relatively uniform dispersion, successfully dispersing the thick layer structure of WS2 on the surface of g-C3N4. Subsequent hydrothermal reaction to grow WO3 on g-C3N4@WS2 revealed rod-shaped WO3 nanorods growing on the sheet-like material. The length of the WO3 nanorods ranged from 0.5 μm to 1 μm, and the close contact between the materials facilitated the migration of internal charge carriers, effectively improving the separation efficiency of photogenerated electron-hole pairs and thus enhancing catalytic performance.

[0057] The degradation of dodecylmorpholine by the WO3 / g-C3N4@WS2 ternary photocatalyst was tested, and the degradation effect was determined by ultraviolet spectrophotometry. The results are as follows: Figure 3 As shown, g-C3N4 alone exhibits some effect in degrading dodecylmorpholine, but the degradation effect is slow and the degradation efficiency is low. The introduction of WO3 significantly improves both the degradation effect and the degradation rate. Figure 3 It can be observed that the material generated by adding WS2 has an efficiency improvement of about 5% compared with the WO3 / g-C3N4 material without WS2, indicating that the addition of WS2 can effectively improve the photocatalytic ability of WO3 / g-C3N4 material. The addition of WS2 is beneficial to increasing the light-harvesting ability and conductivity of the material, and increasing the carrier migration efficiency. The DMP degradation efficiency reaches 80.1% within 60 min, which is 4 times that of the monomeric WO3 and g-C3N4 catalysts.

[0058] The degradation efficiency of the composite WO3 / g-C3N4@WS2 series photocatalysts was greater than that of each individual catalyst, indicating that the three materials were successfully composited into a ternary catalyst after deposition and hydrothermal reaction. Figure 4 It can be observed that the degradation efficiency of the photocatalyst decreased after 5 cycles, but it still maintained 70% efficiency, indicating that the sample has good stability and can be recycled.

[0059] The WO3 / g-C3N4@WS2 ternary photocatalyst was subjected to photocurrent and impedance testing using a CHI760 electrochemical workstation. The photocurrent test results are as follows: Figure 5 As shown, the photocurrent intensity of the WO3 / g-C3N4@WS2 ternary photocatalyst is observed to be 7 times that of the single materials WO3 and g-C3N4, indicating a significant improvement in photocurrent intensity. Impedance test results are as follows. Figure 6 As shown, the curve radii of WO3 and g-C3N4 are much larger than those of the WO3 / g-C3N4@WS2 ternary photocatalyst and WS2 material, indicating that WS2 has lower impedance. Adding WS2 to the composite material can effectively reduce the impedance of the material, which is beneficial to the migration of charge carriers in the composite material, reduces the loss caused by the material impedance, and increases the migration rate of charge carriers in the composite material, thereby improving the photocatalytic ability of the material.

[0060] Example 2

[0061] The difference from Example 1 is that the amount of WS2 added was changed to 0.9 g. After the catalyst synthesis was completed, 0.1 g was weighed and added to 100 ml of 8 mmol / L dodecylmorpholine solution. The mixture was stirred in a dark reactor for 30 min to allow the photocatalyst and solution to reach adsorption equilibrium. Then, the solution was placed under a light source, and the reaction was stirred under illumination for 60 min. Samples were taken every 10 min to test the concentration of dodecylmorpholine in the solution and the degradation rate was calculated. The results are as follows: Figure 7 As shown, the composite WO3 / g-C3N4@WS2 ternary photocatalyst achieved a degradation efficiency of 77% for dodecyl morpholine in solution, which is a significant improvement compared to the monomer, and has a significant effect on the degradation of dodecyl morpholine in a short time.

[0062] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a WO3 / g-C3N4@WS2 ternary photocatalyst, characterized in that, The method comprises the following steps: (1) adding dicyandiamide powder into a beaker, and adding a proper amount of WS2 powder into the beaker; (2) adding the material obtained in step (1) into a proper amount of deionized water and H2SO4, and stirring in an oil bath pot; (3) after the material obtained in step (2) is ground to no obvious particle feeling, calcining is performed; (4) grinding the material obtained in step (3) to obtain flaky composite g-C3N4@WS2; (5) dissolving Na2WO4·H2O in water, and adding the flaky g-C3N4@WS2 prepared in step (4) to obtain an A solution; (6) adding HCl solution dropwise into the A solution obtained in step (5) to adjust the pH value to 1.9-2.1, and then adding water to obtain a B solution; (7) adding glacial acetic acid dropwise into the B solution to adjust the pH value to 2.2-2.4, and then stirring uniformly; (8) hydrothermal reaction of the B solution at 155-165℃ for 14-18h, taking out after cooling to room temperature, centrifugal washing and vacuum drying to obtain a WO3 / g-C3N4@WS2 ternary photocatalyst.

2. The production method according to claim 1, characterized by: In step (2), the amount of H2SO4 added is 3-5ml, the stirring temperature of the oil bath pot is 50-60℃, the stirring time is 20-24h, and the stirring speed is 150-200r / min.

3. The production method according to claim 1, wherein: In step (3), the heating rate of calcining is 4-6℃ / min, and the temperature is kept at 545-555℃ for 3-5h.

4. The production method according to claim 1, wherein: In step (6), the concentration of HCl solution is 1-2mol / L, and the mass ratio of WO3 to g-C3N4@WS2 in the A solution is 90%.

5. The production method according to claim 1, wherein: In step (7), the stirring speed is 150-250r / min, and the stirring time is 20-40min.

6. The production method according to claim 1, wherein: In step (8), the washing mode is alternating washing with water and alcohol, the vacuum drying temperature is 45-55℃, and the vacuum drying time is 22-26h.

7. A WO3 / g-C3N4@WS2 ternary photocatalyst prepared by the preparation method according to any one of claims 1-6.

8. Application of the WO3 / g-C3N4@WS2 ternary photocatalyst prepared in claim 7 to degradation of dodecylmorpholine in water.

9. Use according to claim 8, characterized in that: The WO3 / g-C3N4@WS2 ternary photocatalyst is added into water containing dodecylmorpholine, and is stirred in dark for 25-35min, and then is reacted under light for 50-70min.

10. Use according to claim 8, characterized in that: The ratio of the WO3 / g-C3N4@WS2 ternary photocatalyst to water containing dodecylmorpholine is 0.08-0.12g:90-110ml, the concentration of the dodecylmorpholine in water is 7-9mmol / L, and the pH value of the water is 3.0-3.2.

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