Composite photocatalytic nanomaterial capable of degrading microplastics under visible light and preparation method thereof

Abstract

This invention provides a composite photocatalytic nanomaterial for visible light-driven degradation of microplastics and its preparation method. First, through reverse precipitation, the reactant of TaCl5 and methanol (tantalum methoxide) undergoes stepwise hydrolysis in the presence of ammonia as a precipitant, converting it into Ta hydroxide. The Ta hydroxide is then subjected to high-temperature heat treatment to obtain Ta2O5. Ta2O5 is further co-calcined with melamine to generate black Ta3N5. Next, ammonium molybdate and thiourea are used as catalysts to generate MoS2. x The reaction raw materials were used to prepare MoS2 by a hydrothermal method. x Furthermore, by adding an appropriate amount of polyvinylpyrrolidone, the final generated MoS₂ was influenced. x The morphology gives it a three-dimensional spherical structure; finally, through hydrothermal reaction, Ta3N5 and MoS3 with a mass ratio of 1.75:3.8 are combined. x The dispersion was subjected to a hydrothermal reaction at 160℃ to finally prepare Ta3N5 / MoS x Composite photocatalytic nanomaterials. The preparation process is simple and easy to operate. Furthermore, Ta3N5 / MoS... x Composite photocatalytic nanomaterials exhibit exceptionally good degradation and reduction effects on polyethylene-ethyl acrylate under photocatalytic conditions.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of nanomaterials, and particularly relates to a composite photocatalytic nanomaterial for visible light-driven degradation of microplastics and a preparation method thereof. BACKGROUND

[0002] The wide application of plastics facilitates people's life and promotes industrial development, but the environmental pollution problem caused by the plastics is increasingly serious. The traditional technology for treating the pollution caused by the plastics has problems such as harsh process conditions, poor reaction efficiency, and huge energy consumption cost. As a new green and energy-saving technology, photocatalysis can generate strong oxidizing active oxygen species by using solar energy, and is widely considered as one of the key technologies for relieving energy crisis, solving environmental problems, and realizing sustainable development.

[0003] Ta3N5 is considered as a potential solar photocatalytic degradation material. The valence band of Ta3N5 is located at-0.5 eV-1.55 eV (vs NHE, pH=7), and the band gap is about 2.1 eV, so that more than 45% of the sunlight can be absorbed. However, due to the high carrier recombination rate and low solar energy utilization rate of Ta3N5 material, the photocatalytic activity of Ta3N5 is poor. This limits the application of Ta3N5 in photocatalytic degradation of plastics. SUMMARY

[0004] In view of the above problems in the prior art, the application provides a Ta3N5 / MoS x The composite photocatalytic nanomaterial and the preparation method thereof are prepared by doping MoS x with a band gap matched with Ta3N5 in a single Ta3N5 material to construct a Ta3N5 / MoS x heterojunction composite photocatalytic material, so as to maximize the separation and utilization of photo-generated electron-hole pairs, and obtain a heterojunction composite photocatalytic nanomaterial with more excellent solar-activated free radical conversion efficiency and photodegradation efficiency. The photocatalytic degradation performance of the heterojunction composite photocatalytic nanomaterial is excellent, which is verified by a microplastic (PE) degradation experiment. The specific application content is as follows:

[0005] In a first aspect, the application provides a preparation method of a composite photocatalytic nanomaterial for visible light-driven degradation of microplastics, and the preparation method comprises the following preparation steps:

[0006] S1, using TaCl5, methanol and ammonia water as reaction raw materials, a Ta2O5 is obtained through reverse homogeneous precipitation and high-temperature heat treatment, and the Ta2O5 is further subjected to thermal nitriding treatment by vacuum calcining the Ta2O5 and melamine, so as to obtain a black Ta3N5 solid powder;

[0007] S2, ammonium molybdate and thiourea with a mass ratio of 1.75:3.8 are dissolved in deionized water, an appropriate amount of polyvinylpyrrolidone is added, and then transferred to a reaction kettle lined with polytetrafluoroethylene, and a hydrothermal reaction is carried out at 180-220°C, and the reaction product is washed, dried, and obtained MoS x ;

[0008] S3, Ta3N5 and MoS x with a mass ratio of 1:3.75 are respectively dispersed in an appropriate amount of deionized water, then the two dispersions are mixed and transferred to a Teflon reaction kettle, and a hydrothermal reaction is carried out at 160°C, and the product is collected by centrifugation, washed and dried to obtain the Ta3N5 / MoS x composite photocatalytic nanomaterial.

[0009] Optionally, step S1 specifically comprises:

[0010] S11, TaCl5 is dissolved in a methanol solution, then added to an NH3·H2O solution, and a reverse homogeneous precipitation reaction is carried out under mechanical stirring to generate white precipitate, which is collected by filtration, washed, and then further high-temperature heat-treated at 800°C to obtain Ta2O5 nanoparticles; wherein the mass-volume ratio of TaCl5, methanol and NH3·H2O is 1g:10-15ml:50ml;

[0011] S12, Ta2O5 nanoparticles are placed in a quartz boat, melamine is placed in another quartz boat, and the two quartz boats are placed adjacent to the center of the tube furnace, vacuumed, and then heated to 650-850°C at a heating rate of 5-10°C / min. Ta2O5 is heat-nitrided for 8-10h, and after the reaction is completed, black Ta3N5 solid powder is collected; the mass ratio of Ta2O5 to melamine is 1:7.

[0012] Optionally, in step S11, the mechanical stirring speed is 400r / min, and the mechanical stirring time is 1h;

[0013] The high-temperature heat treatment time is 6h;

[0014] The washing is washed with deionized water for 2-3 times.

[0015] Optionally, in step S12, the vacuum degree in the tube furnace is not more than 100pa;

[0016] The tube furnace is heated to 800°C at a heating rate of 10°C / min;

[0017] The heat-nitriding treatment time is 8h.

[0018] Optionally, in step S2, the mass ratio of the ammonium molybdate, the thiourea and the polyvinylpyrrolidone is 1.75:3.8:1.25.

[0019] The hydrothermal reaction lasts for 20-24 hours.

[0020] Optionally, the washing is alternating washing with anhydrous ethanol and deionized water for 6-8 times.

[0021] The drying temperature is 60 DEG C.

[0022] Optionally, the MoS x The Ta3N5 is dispersed by mechanical stirring.

[0023] Optionally, the frequency of the ultrasonic is 40 MHz, and the time of the ultrasonic is 30-60 minutes.

[0024] The rotating speed of the mechanical stirring is 200-600 r / min, and the time of the mechanical stirring is 10-30 minutes.

[0025] Optionally, the washing is alternating washing with anhydrous ethanol and deionized water for 6-8 times.

[0026] The drying temperature is 60 DEG C.

[0027] In a second aspect, the application provides a Ta3N5 / MoS x composite photocatalytic nanomaterial obtained by the preparation method of the first aspect.

[0028] Compared with the prior art, the application has the following advantages:

[0029] The application provides a preparation method of a composite photocatalytic nanomaterial for visible light driven degradation of microplastics. x nanoparticles into the Ta3N5 photocatalytic material to form a new Ta3N5 / MoS x composite photocatalytic nanomaterial. x The introduction of the spherical MoS x composite photocatalytic nanomaterial has a wider visible light absorption range than the single Ta3N5 photocatalytic material, and can better utilize solar energy. x The introduction of the spherical MoS x The photo-generated electron-hole pairs of the Ta3N5 / MoS x) separation occurs, thereby avoiding the rapid in-situ recombination of electron-hole in the band gap of single Ta3N5 photocatalytic material, which helps to separate the photo-generated carriers and reduce the band gap.

[0030] The composite photocatalytic nanomaterial provided by the application has extremely excellent degradation and reduction effects on polyethylene-ethyl acrylate under photocatalytic conditions. Under visible light irradiation, the MoS x The electrons in the conduction band can easily react with the adsorbed Ta3N5 / MoS x The oxygen on the surface of the composite photocatalytic nanomaterial reacts to generate free radicals, which can quickly convert microplastics such as polyethylene, polyethylene-ethyl acrylate and polyvinyl chloride into small molecular substances, and the photo-generated holes in the valence band of Ta3N5 can also directly act on the degradation of pollutants. MoS x The electrons in the conduction band will be combined with the holes in the valence band of Ta3N5 through a Z-type charge transfer mechanism. Finally, the interfacial recombination of photo-generated electrons and holes effectively inhibits the MoS x The charge of Ta3N5 / MoS x The composite photocatalytic nanomaterial has a much higher degradation efficiency on microplastics, especially polyethylene-ethyl acrylate, than single Ta3N5 photocatalytic material under visible light irradiation. Experiments prove that under the condition that the dosages of the composite photocatalytic nanomaterial and single Ta3N5 are the same (both are 0.1 mg) and the content of polyethylene-ethyl acryate in the sewage to be treated is the same (both are 0.5 mg / mL), the Ta3N5 / MoS x The composite photocatalytic nanomaterial has a much higher degradation efficiency on microplastics, especially polyethylene-ethyl acryate, than single Ta3N5 photocatalytic material under visible light irradiation. Experiments prove that under the condition that the dosages of the composite photocatalytic nanomaterial and single Ta3N5 are the same (both are 0.1 mg) and the content of polyethylene-ethyl acrate in the sewage to be treated is the same (both are 0.5 mg / mL), the Ta3N5 / MoS x The degradation efficiency of the composite photocatalytic nanomaterial on polyethylene-ethyl acrylate is close to 40% within 8 hours, while the degradation efficiency of single Ta3N5 photocatalytic material on polyethylene-ethyl acrylate is less than 5% within 8 hours. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0032] Figure 1 The Ta3N5 / MoS x The preparation method flow chart of the composite photocatalytic nanomaterial is shown in the figure.

[0033] Figure 2A SEM image of the Ta3N5 photocatalytic nanomaterial provided by the embodiment of the present application is shown.

[0034] Figure 3 A SEM image of the MoS2 photocatalytic nanomaterial provided by the embodiment of the present application is shown. x A SEM image of the MoS2 photocatalytic nanomaterial provided by the embodiment of the present application is shown.

[0035] Figure 4 A SEM image of the Ta3N5 / MoS2 composite photocatalytic nanomaterial provided by the embodiment of the present application is shown. x A SEM image of the Ta3N5 / MoS2 composite photocatalytic nanomaterial provided by the embodiment of the present application is shown.

[0036] Figure 5 A UV diffuse reflectance spectrum of the photocatalytic nanomaterial provided by the embodiment of the present application is shown.

[0037] Figure 6 A XRD spectrum of the Ta3N5 / MoS2 composite photocatalytic nanomaterial provided by the embodiment of the present application is shown. x A XRD spectrum of the Ta3N5 / MoS2 composite photocatalytic nanomaterial provided by the embodiment of the present application is shown.

[0038] Figure 7 A XPS spectrum of the Ta3N5 / MoS2 composite photocatalytic nanomaterial provided by the embodiment of the present application is shown. x A XPS spectrum of the Ta3N5 / MoS2 composite photocatalytic nanomaterial provided by the embodiment of the present application is shown.

[0039] Figure 8 A N2 adsorption-desorption isotherm and pore size distribution of the Ta3N5 / MoS2 composite photocatalytic nanomaterial provided by the embodiment of the present application is shown. x A N2 adsorption-desorption isotherm and pore size distribution of the Ta3N5 / MoS2 composite photocatalytic nanomaterial provided by the embodiment of the present application is shown.

[0040] Figure 9 A performance comparison chart of the photocatalytic nanomaterial provided by the embodiment of the present application in photocatalytic degradation of polyethylene-acrylic acid ethyl ester is shown. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, any person under the inspiration of the present application or combining the present application with other prior art features to obtain any product same or similar to the present application falls within the protection scope of the present application. In addition, all other embodiments obtained by the ordinary skilled in the art without carrying out creative labor fall within the protection scope of the present application.

[0042] Unless otherwise indicated, conventional methods of chemistry, biochemistry, molecular biology, and pharmacology, including recombinant techniques and pharmacological techniques, are described in detail in the literature, for example, in "Current Protocols in Molecular Biology" (F. M. Ausubel et al. eds., 1987), "Cell Culture" (W. R. Wiener and

[0043] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, where appropriate, such techniques, methods, and apparatus can be considered as part of the present disclosure.

[0044] In the description of the present application, it should be understood that the use of "first", "second", and the like words to describe various components is only intended to distinguish the components from each other, and the above words do not have special meanings unless otherwise stated. Therefore, it should not be understood as a limitation on the scope of protection of the present application.

[0045] In addition, the technical features involved in the different embodiments of the application described below can be combined with each other as long as they do not conflict with each other.

[0046] From the pore size distribution curve, it can be seen that the pore size distribution of all catalysts is between 2-40 nm, the specific surface area and pore volume are large, and it belongs to mesoporous material. The increase of pore volume is conducive to the electron diffusion and transfer between the composite photocatalytic nanomaterials and the increase of active sites, and the increase of specific surface area of the catalyst is more conducive to the adsorption of pollutant molecules and thus improves the photocatalytic activity.

[0047] In the photocatalytic reaction system, e - The active sites contact with the liquid phase system to generate free radicals for degrading pollutants. Therefore, the number of active sites and the electron mobility are important factors affecting the catalytic activity of the photocatalyst. In recent years, MoS x has attracted widespread attention in the field of photocatalysis due to its high activity and high abundance. Studies have shown that the active sites of MoS x are mainly determined by unsaturated sulfur. The unsaturated sulfur atoms are mainly distributed on the edge of MoS x . However, there is a van der Waals force between the traditional two-dimensional MOS2 and MoS x nanosheets, which makes the nanosheets stack with each other, and the unsaturated sulfur atoms on the edge are covered, which seriously affects the photocatalytic performance of MoS x . Therefore, it is particularly important to change the morphology of molybdenum sulfide to inhibit the interlayer stacking, increase the number of unsaturated sulfur, and shorten the electron transfer path.

[0048] The embodiment of the present application hopes to inhibit interlayer stacking, increase the number of unsaturated sulfur by changing the morphology of molybdenum sulfide, and then prepare spherical MoS x The nanoparticles are compounded with Ta3N5 to form a new Ta3N5 / MoS x The composite photocatalytic nanomaterial is prepared. Based on the technical concept, the specific implementation content of the present application is as follows:

[0049] In a first aspect, the present application provides a Ta3N5 / MoS x The preparation method of the composite photocatalytic nanomaterial, Figure 1 The Ta3N5 / MoS x The preparation method of the composite photocatalytic nanomaterial is shown in the flow chart, Figure 1 As shown, the preparation method of the composite photocatalytic nanomaterial comprises the following preparation steps:

[0050] S1, using TaCl5, methanol and ammonia as reaction raw materials, through reverse homogeneous precipitation and high-temperature heat treatment, Ta2O5 is obtained, and further through vacuum calcination of Ta2O5 and melamine, the Ta2O5 is subjected to thermal nitriding treatment to obtain black Ta3N5 solid powder;

[0051] S2, ammonium molybdate and thiourea with a mass ratio of 1.75:3.8 are dissolved in deionized water, an appropriate amount of polyvinylpyrrolidone is added, and then transferred to a reaction kettle lined with polytetrafluoroethylene, and subjected to hydrothermal reaction at 180-220 DEG C, and the reaction product is washed, dried, and obtained MoS x ;

[0052] S3, Ta3N5 and MoS x with a mass ratio of 1:3.75 are respectively dispersed in an appropriate amount of deionized water, then the two dispersion liquids obtained are mixed and transferred to a Teflon reaction kettle, and subjected to hydrothermal reaction at 160 DEG C, and the product is collected by centrifugation, washed and dried to obtain the Ta3N5 / MoS x composite photocatalytic nanomaterial.

[0053] In specific implementation, the Ta3N5 / MoS x composite photocatalytic nanomaterial is prepared by three steps; in the first step (S1), TaCl5 and methanol reactants (tantalum methoxide) are subjected to step-by-step hydrolysis under the action of the precipitant ammonia water to convert into Ta hydroxide, and the Ta hydroxide is subjected to high-temperature heat treatment to obtain Ta2O5; Ta2O5 is further calcined with melamine to generate black Ta3N5; in the second step (S2), the present application uses ammonium molybdate and thiourea to generate MoS xreaction raw material, and MoS x is prepared by adding a proper amount of polyvinylpyrrolidone to affect the morphology of the finally generated MoS x , so that it has a three-dimensional spherical structure; the third step (S3), which is also the most important step, the embodiment of the present application mixes the dispersion liquids containing Ta3N5 and MoS x in a mass ratio of 1.75:3.8 respectively, and performs a hydrothermal reaction at 160℃ to finally prepare Ta3N5 / MoS x composite photocatalytic nanomaterial. The preparation process is simple and easy to operate.

[0054] Further, the step S1 specifically comprises:

[0055] S11, dissolving TaCl5 in a methanol solution, then adding it into an NH3·H2O solution, and performing a reverse homogeneous precipitation reaction under mechanical stirring to generate white precipitate, which is collected and washed after filtration, and then further performing high-temperature heat treatment on the white precipitate at 800℃ to obtain Ta2O5 nanoparticles; wherein the mass-volume ratio of the TaCl5, the methanol and the NH3·H2O is 1g:10-15ml:50ml.

[0056] In the present preparation step, since the methanol is a polar organic solvent containing a large amount of hydroxyl groups, it can be alcoholized with the tantalum chloride to generate tantalum methoxide (CH3O)5Ta, which further generates Ta hydroxides such as Ta(OH)Cl4, Ta(OH)2Cl3, Ta(OH)3Cl2, Ta(OH)4Cl, Ta(OH)5 and Ta(OH)O2 in a step-by-step hydrolysis reaction in the environment of a large amount of ammonia water (precipitating agent). In order to fully hydrolyze the TaCl5, the present application selects to dissolve the TaCl5 in a methanol solution, and then further adds it into an ammonia water solution to ensure that the TaCl5 is fully converted into Ta hydroxides. The Ta hydroxides generated by the hydrolysis are further subjected to high-temperature heat treatment at 800℃ to obtain Ta2O5 nanoparticles.

[0057] In the present step, the rotating speed of the mechanical stirring is 400r / min, and the mechanical stirring time is 1h; the high-temperature heat treatment time is 6h; and the washing is performed 2-3 times with deionized water.

[0058] S12, placing the Ta2O5 nanoparticles in a quartz boat, placing melamine in another quartz boat, placing the two quartz boats adjacent to each other in the middle of a tube furnace, vacuumizing, and then increasing the temperature to 650-850℃ at a temperature increasing rate of 5-10℃ / min to perform 8-10h thermal nitridation treatment on the Ta2O5, and then collecting a black Ta3N5 solid powder after the reaction is completed; the mass ratio of the Ta2O5 to the melamine is 1:7. Figure 2A SEM diagram of the Ta3N5 photocatalytic nanomaterial provided by the embodiment of the present application is shown.

[0059] In the preparation step, the vacuum degree of the tube furnace is not more than 100 Pa; the tube furnace is preferably heated to 800 DEG C at a temperature rising rate of 10 DEG C / min for 8h of thermal nitriding treatment.

[0060] Further, in step S2, the ammonium molybdate and the thiourea are used as the reaction raw materials to synthesize MoS x During the process, the addition of polyvinylpyrrolidone (PVP) can realize the controlled synthesis of MoS x , compared with the traditional two-dimensional MoS x nanosheet structure, the MoS x with the three-dimensional spherical structure effectively avoids the accumulation between the nanosheets, exposes more active sites, effectively shortens the electron transfer path, and exposes unsaturated Mo atoms and S atoms at the edges. These unsaturated atoms can also promote the edge activity of sulfur, thereby playing the role of active sites. The MoS x with the three-dimensional spherical structure exhibits outstanding photocatalytic hydrogen evolution activity.

[0061] In step S2, the mass ratio of the ammonium molybdate, the thiourea and the polyvinylpyrrolidone is 1.75:3.8:1.25; and the hydrothermal reaction lasts for 20-24h.

[0062] Further, the washing is alternating washing with anhydrous ethanol and deionized water for 6-8 times; and the drying temperature is 60-80 DEG C.

[0063] Further, the MoS x is dispersed in an ultrasonic manner; and the Ta3N5 is dispersed in a mechanical stirring manner.

[0064] Further, the frequency of the ultrasonic is 40MHz, and the time of the ultrasonic is 30-60min; the rotating speed of the mechanical stirring is 200-600r / min, and the time of the mechanical stirring is 10-30min.

[0065] Further, in step S3, the washing is alternating washing with anhydrous ethanol and deionized water for 6-8 times; and the drying temperature is 60 DEG C.

[0066] In order for those skilled in the art to more clearly understand the present application, the Ta3N5 / MoS x composite photocatalytic nanomaterial for visible light driven degradation of microplastics, the preparation method and application thereof are described in detail.

[0067] Example 1

[0068] About 1 g of TaCl5 was dissolved in 10 mL of MeOH, and then 50 mL of NH3·H2O was added to the mixed system. After stirring at 400 r / min for 1 h, the white precipitate was filtered and washed with water. After heating at 800℃ for 6 h, Ta2O5 nanoparticles were obtained. Then, 100 mg of Ta2O5 nanoparticles were weighed and placed in a quartz boat, and 700 mg of melamine was weighed and placed in another quartz boat. The two quartz boats were placed adjacent to each other in the middle of a tube furnace, sealed, vacuumed to ensure that the air pressure was lower than 30 Pa, and the tube furnace was set to a temperature rising rate of 10℃ / min to 800℃. After heating at 800℃ for 8 h, black solid powder product Ta3N5 nanoparticles were obtained by thermal nitriding in a vacuum tube furnace, and were naturally cooled.

[0069] Figure 2 The SEM image of the Ta3N5 photocatalytic nanomaterial provided by the embodiment of the present application is shown in FIG. 1. Figure 2 As shown in FIG. 1, the Ta3N5 photocatalytic nanomaterial has a typical block layer structure.

[0070] Example 2

[0071] In 60 mL of deionized water, 1.75 g of ammonium molybdate ((NH4)6Mo7O 24 ) and 3.8 g of thiourea (H2NCSNH2) were added, and the solution was stirred at 300 r / min at room temperature to make the solution uniform. Then, 1.25 g of polyvinylpyrrolidone (PVP) was added to the above solution. The homogeneous solution was then transferred to an 80 mL reaction kettle lined with polytetrafluoroethylene for hydrothermal reaction, and the reaction temperature was 200℃ for 24 h. After the reaction was completed, the obtained precipitate was centrifuged and washed with anhydrous ethanol and deionized water alternately for 6 times. After the product was dried at 60℃, spherical MoS x nanoparticles were collected.

[0072] Figure 3 The SEM image of the MoS x photocatalytic nanomaterial provided by the embodiment of the present application is shown in FIG. 2. Figure 3 As shown in FIG. 2, the MoS x photocatalytic nanomaterial provided by the embodiment of the present application has a three-dimensional spherical structure.

[0073] Example 3

[0074] Step 1: Dissolve approximately 1 g of TaCl5 in 10 mL of MeOH, then add a measured amount of 50 mL of NH3·H2O to the mixture. Stir at 400 r / min for 1 h, filter, and wash the white precipitate with water. Heat at 800 °C for 6 h to obtain Ta2O5 nanoparticles. Then weigh 100 mg of Ta2O5 nanoparticles and place them in a quartz boat, and weigh 700 mg of melamine and place them in another quartz boat. Place the two quartz boats adjacent to each other in the center of a tube furnace, seal, and evacuate to ensure the pressure is below 30 Pa. Set the tube furnace to heat to 800 °C at a rate of 10 °C / min, and hold at 800 °C for 8 h. Perform thermal nitriding in the vacuum tube furnace, and allow to cool naturally to obtain the black solid powder product Ta3N5 nanoparticles.

[0075] Step 2: Add 1.75g ​​of ammonium molybdate ((NH4)6Mo7O) to 60mL of deionized water. 24 3.8 g of thiourea (H2NCSNH2) was added and stirred at 300 rpm at room temperature to homogenize the solution. Then, 1.25 g of polyvinylpyrrolidone (PVP) was added to the solution. The homogeneous solution was then transferred to an 80 mL polytetrafluoroethylene-lined reactor for hydrothermal reaction at 200 °C for 24 h. After the reaction, the precipitate obtained by centrifugation was washed six times alternately with anhydrous ethanol and deionized water. The product was dried at 60 °C and collected to obtain spherical MoS2. x Nanoparticles.

[0076] Step 3, add 40mg of spherical MoS x Nanoparticles were placed in 20 mL of deionized water and sonicated at 40 MHz for 1 h. Next, 150 mg of Ta3N5 was dispersed in 30 mL of deionized water and stirred continuously at 400 rpm for 20 min. Finally, both solutions were transferred to an 80 mL Teflon reactor and heated to 160 °C in an oven for 16 h. After the reaction, the precipitate obtained by centrifugation was washed several times with anhydrous ethanol and deionized water. The product was collected after drying at 60 °C for 6 h, yielding pure black Ta3N5 / MoS2. x powder.

[0077] Figure 4 The Ta3N5 / MoS provided in the embodiment of the present invention is shown. x SEM images of composite photocatalytic nanomaterials, such as Figure 4 As shown, the Ta3N5 / MoS provided in this embodiment of the invention x The composite photocatalytic nanomaterial has a spherical layered structure.

[0078] Figure 5 The ultraviolet diffuse reflectance spectrum of the photocatalytic nanomaterials provided in the embodiments of the present invention is shown, such as... Figure 5As shown, the Ta3N5 photocatalytic nanomaterial prepared in Example 1 has a light absorption cutoff edge of about 635 nm and a certain absorption tail peak. The Ta3N5 / MoS x composite photocatalytic nanomaterial synthesized in Example 3 has a wider visible light absorption range and an absorption edge similar to Ta3N5 at 650 nm. Due to the complementary light absorption of the two, the Ta3N5 / MoS x composite photocatalytic nanomaterial can achieve full absorption in the ultraviolet, visible and infrared regions, which indicates that, due to the introduction of MoS x , the Ta3N5 / MoS x composite photocatalytic nanomaterial has a significantly expanded light absorption boundary, which can better utilize solar energy than the single Ta3N5 photocatalytic nanomaterial.

[0079] Figure 6 As shown, the XRD pattern of the Ta3N5 / MoS x composite photocatalytic nanomaterial provided by the embodiment of the present application is shown in the figure. Figure 6 As shown, the Ta3N5 / MoS x composite catalyst system has both Ta3N5 and MoS x characteristic peaks, indicating that the two semiconductor materials are well combined together.

[0080] Figure 7 As shown, the XPS pattern of the Ta3N5 / MoS x composite photocatalytic nanomaterial provided by the embodiment of the present application is shown in the figure. Figure 7 As shown, the XPS pattern proves that the high-purity Ta3N5 is successfully synthesized in the embodiment of the present application, and it can also prove that, when the composite heterojunction catalyst is prepared, MoS x is successfully combined with Ta3N5 and the valence state of Ta3N5 element remains stable.

[0081] Figure 8 As shown, the N2 adsorption-desorption isotherm and pore size distribution of the Ta3N5 / MoS x composite photocatalytic nanomaterial provided by the embodiment of the present application are shown in the figures. Figure 8 As shown, the main figure is the N2 adsorption-desorption isotherm, which has the obvious feature of hysteresis loop, and is a typical IV-type adsorption isotherm, which indicates that the composite photocatalytic nanomaterial is a mesoporous adsorption material and has small mesopores. The subfigure is the pore size distribution obtained by BET test, which further verifies that the composite photocatalytic nanomaterial mainly contains micropores and mesopores with a pore size of 5-30 nm and has a large specific surface area.

[0082] Experimental Example 1

[0083] The present experimental example is used to verify the Ta3N5 photocatalytic nanomaterial prepared in Example 1 and the Ta3N5 / MoS x Degradation performance of the composite photocatalytic nanomaterial on polyethylene-ethyl acrylate.

[0084] Microplastic degradation experiment of the composite photocatalytic nanomaterial and single material:

[0085] The catalytic process was carried out in a 250 mL custom-made double-walled quartz beaker with a cooling water circulation system to maintain a constant reaction temperature of 25℃. A 300 W xenon lamp with a cut-off filter of 420 nm was used as the visible light source, with an average intensity of 200 mW / cm 2 In each operation, 0.1 mg Ta3N5 / MoS x The photocatalyst was dispersed in 100 mL of ultrapure water containing 50 mg of microplastics (copolymer of ethyl acrylate and ethylene extracted from cosmetic waste liquid) MPs. The suspension was continuously stirred throughout the reaction process. Dark adsorption experiments were carried out for 30 min before light irradiation to allow the MPs to mix well with the photocatalyst, and then 5 mmol of PMs was added to the suspension. The reaction was completed after a period of light irradiation, and the catalyst and microplastics were separated by density separation method. The post-reaction MPs were washed several times with ultrapure water and placed in a vacuum drying oven at 60℃ for 6 h for drying.

[0086] The degradation efficiency of the MPs was determined by measuring the weight loss of the MPs before and after the reaction, and the calculation method is shown in formula (2-1):

[0087]

[0088] In the formula: ML is the mass loss percentage of the microplastics, %;

[0089] m i is the mass of the initial microplastic sample, mg;

[0090] m f is the mass of the residual MPs after the reaction, mg.

[0091] Figure 9 A comparison chart of the photocatalytic degradation performance of polyethylene-ethyl acrylate by the photocatalytic nanomaterial provided in the embodiments of the present application is shown. As shown in Figure 9 The degradation efficiency of polyethylene-ethyl acrylate by the Ta3N5 catalytic material provided in Example 1 is not higher than 5% within 8 h, which is due to the limited absorbance of the single Ta3N5 catalytic material and the high recombination rate of photo-generated electron-hole pairs, resulting in poor degradation efficiency of polyethylene-ethyl acrylate. The degradation efficiency of polyethylene-ethyl acrylate by the Ta3N5 / MoS xThe degradation efficiency of the composite photocatalytic nanomaterial on the cohesive ethylene-acrylic acid ethyl ester is close to 40% in 8 hours. This is due to the introduction of MoS x in Ta3N5, which widens the visible light absorption range of the Ta3N5 photocatalytic nanomaterial, and helps to separate the photo-generated carriers and reduce the band gap.

[0092] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present specification.

[0093] For the method embodiments, in order to simply describe, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the order of the described actions, because according to the present application, certain steps can be performed in other order or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily necessary for the present application.

[0094] The above describes in detail the Ta3N5 / MoS x composite photocatalytic nanomaterial and its preparation method, and the principle and implementation manner of the present application are described by applying specific examples. The above embodiment description is only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation manner and application range will be changed, and the above description should not be understood as a limitation of the present application.

Claims

1. A method for preparing a composite photocatalytic nanomaterial for visible light-driven degradation of microplastics, characterized in that, The preparation method of the composite photocatalytic nanomaterial includes the following preparation steps: S1. Using TaCl5, methanol, and ammonia as reactants, Ta2O5 is obtained through reverse homogeneous precipitation and high-temperature heat treatment. Further, Ta2O5 is subjected to thermal nitriding treatment via vacuum calcination and melamine to obtain black Ta3N5 solid powder, specifically including: S11. TaCl5 is dissolved in methanol solution and then added to NH3·H2O. A reverse homogeneous precipitation reaction is carried out under mechanical stirring. The resulting white precipitate is collected by filtration, washed, and then subjected to high-temperature heat treatment at 800 ºC to obtain Ta2O5 nanoparticles. The mass-volume ratio of TaCl5, methanol, and NH3·H2O is 1 g: 10-15 mL: 50 mL. S12. Place Ta2O5 nanoparticles in one quartz boat and melamine in another quartz boat. Place the two quartz boats side by side in the center of a tube furnace. After evacuation, heat the furnace to 650-850℃ at a rate of 5-10℃ / min to perform thermal nitriding treatment on Ta2O5 for 8-10 hours. After the reaction is complete, collect the black Ta3N5 solid powder. The mass ratio of Ta2O5 to melamine is 1:

7. S2. Ammonium molybdate and thiourea in a mass ratio of 1.75:3.8 were dissolved in deionized water. An appropriate amount of polyvinylpyrrolidone was added, and the mixture was transferred to a polytetrafluoroethylene-lined reactor. A hydrothermal reaction was carried out at 180–220 °C. The resulting product was washed and dried to obtain MoS₂ with a three-dimensional spherical structure. x ; S3, Mix Ta3N5 and MoS at a mass ratio of 1:3.

75. x The two dispersions were separately dispersed in an appropriate amount of deionized water. The resulting dispersions were then mixed and transferred to a Teflon-coated reactor for hydrothermal reaction at 160 °C. The products were collected by centrifugation, washed, and dried to obtain the composite photocatalytic nanomaterial—Ta3N5 / MoS2. x .

2. The method for preparing composite photocatalytic nanomaterials for visible light-driven degradation of microplastics according to claim 1, characterized in that, In step S11, the mechanical stirring speed is 400 r / min, and the mechanical stirring time is 1 h; The high-temperature heat treatment lasted for 6 hours. The washing process involves washing with deionized water 2-3 times.

3. The method for preparing composite photocatalytic nanomaterials for visible light-driven degradation of microplastics according to claim 1, characterized in that, In step S12, the vacuum degree in the tubular furnace is no greater than 100 Pa; The tubular furnace is heated to 800°C at a heating rate of 10°C / min; The thermal nitriding treatment lasted for 8 hours.

4. The method for preparing composite photocatalytic nanomaterials for visible light-driven degradation of microplastics according to claim 1, characterized in that, In step S2, the mass ratio of ammonium molybdate, thiourea, and polyvinylpyrrolidone is 1.75:3.8:1.

25. The hydrothermal reaction lasts for 20-24 hours.

5. The method for preparing composite photocatalytic nanomaterials for visible light-driven degradation of microplastics according to claim 1, characterized in that, In step S2, the washing involves alternating between anhydrous ethanol and deionized water for 6-8 times. The drying temperature is 60-80 ℃.

6. The method for preparing composite photocatalytic nanomaterials for visible light-driven degradation of microplastics according to claim 1, characterized in that, In step S3, MoS x Ultrasonic dispersion was used, while Ta3N5 was dispersed by mechanical stirring.

7. The method for preparing composite photocatalytic nanomaterials for visible light-driven degradation of microplastics according to claim 6, characterized in that, The frequency of the ultrasound is 40 MHz, and the duration of the ultrasound is 30-60 min; The mechanical stirring speed is 200-600 r / min, and the mechanical stirring time is 10-30 min.

8. The method for preparing composite photocatalytic nanomaterials for visible light-driven degradation of microplastics according to claim 1, characterized in that, In step S3, the washing involves alternating between anhydrous ethanol and deionized water for 6-8 times. The drying temperature is 60 °C.

9. A composite photocatalytic nanomaterial obtained by the preparation method according to any one of claims 1-8.

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