WO2024007201A1

WO2024007201A1 - Copper-doped zinc oxide nanorod, preparation method therefor, and use thereof in piezoelectric-photocatalytic removal of organic pollutants

Info

Publication number: WO2024007201A1
Application number: PCT/CN2022/104166
Authority: WO
Inventors: 路建美; 李娜君
Original assignee: 苏州大学
Priority date: 2022-07-06
Filing date: 2022-07-06
Publication date: 2024-01-11

Abstract

Disclosed in the present invention are a copper-doped zinc oxide nanorod, a preparation method therefor, and a use thereof in piezoelectric-photocatalytic removal of organic pollutants. The copper-doped zinc oxide nanorod is obtained by mixing a water-soluble zinc salt, a water-soluble copper salt, polyvinylpyrrolidone, hexamethylenetetramine and water, and carrying out a hydrothermal reaction. By placing the copper-doped zinc oxide nanorods in a water body containing organic pollutants and carrying out illumination and/or ultrasonic treatment, the organic pollutants in the water body can be completely removed. Under the combined action of illumination and ultrasonic vibration, the material is excited by light to produce photo-generated charges, and a polarization electric field generated due to the ultrasonic effect promotes migration and separation of the photo-generated charges, so that the photocatalytic performance is effectively enhanced. The nano-material prepared by the present invention has chemical stability, high reactivity and piezoelectricity, and has an excellent application value in the field of piezoelectric-photocatalysis.

Description

A kind of copper-doped zinc oxide nanorod, preparation method and its application in piezoelectric-photocatalytic removal of organic pollutants

Technical field

The invention relates to the technical fields of nanomaterials and piezoelectric-photocatalysis, and specifically relates to a preparation method of copper-doped zinc oxide nanorods and the application of the material in piezoelectric-photocatalytic removal of water pollutants.

Background technique

Due to the rapid development of industry and the extensive use of fossil fuels, environmental pollution and energy shortages seriously threaten the sustainable development of today's society. Among various solutions, semiconductor-based photocatalytic technology has good application prospects due to its green process and easy implementation. The reaction efficiency of photocatalysis greatly depends on the separation and migration rate of photogenerated charges, but photogenerated charges will quickly recombine on the photocatalyst body and surface, which results in low charge separation efficiency and low photocatalytic efficiency, thereby limiting the practical application of photocatalysts. application. Therefore, various strategies (such as constructing heterojunctions, modifying metals or metal oxides, and forming surface defects) have been proposed to promote surface charge separation and enhance photocatalytic activity. Among them, polarization field engineering has been proven to be an effective method to improve Methods for photogenerated charge separation and enhanced photocatalytic performance.

Zinc oxide (ZnO), as an important semiconductor material, has been widely used in catalysis, paint industry, ceramics, varistor, fertilizers and cosmetics. In the field of photocatalysis, zinc oxide semiconductors have become a popular choice for environmental treatment due to their unique properties, such as direct wide bandgap in the near-ultraviolet spectral region, extremely strong oxidation ability, good photocatalytic performance, and large free Exciton binding energy (the exciton emission process can continue at room temperature and even higher).

The performance of zinc oxide catalysts in degrading pollutants needs to be improved. The existing technology mixes a solution containing zinc salts and copper salts with an inorganic alkali aqueous solution, controls the pH value to 10.5-11.5, and then places it in a closed container for hydrothermal reaction. After the solid-liquid separation, the solid is collected and washed with water, dried and calcined under the protection of protective gas to obtain a mesoporous nanorod-shaped catalyst doped with copper oxide and zinc oxide, which requires hydrogen peroxide to be driven when degrading pollutants. The preparation of zinc oxide catalysts in the existing technology requires calcination. Currently, there is no zinc oxide or doped zinc oxide catalyst prepared without calcination.

technical problem

The purpose of the present invention is to provide a nanomaterial that can respond to visible light and external pressure at the same time, and to quickly and effectively degrade pollutants in water through piezoelectric-photocatalytic synergy. Bisphenol A was used as the target organic pollutant to study the catalytic performance of the nanomaterials prepared in the present invention. The copper-doped zinc oxide nanorods disclosed in the present invention can utilize the piezoelectric effect to coordinate photocatalysis to improve degradation performance. Under the combined action of illumination and ultrasonic vibration, the material is excited by light to generate photogenerated charges, and the polarized electric field generated by ultrasound promotes the migration and separation of photogenerated charges, thereby effectively enhancing the photocatalytic performance. The one-dimensional nanorod morphology of the material can provide a fast channel for electron migration and promote charge separation. The nanomaterial prepared by the invention has chemical stability, high reactivity and piezoelectricity, and has excellent application value in the field of piezoelectric-photocatalysis.

Technical solutions

In order to achieve the above object, the specific technical solution of the present invention is as follows: a copper-doped zinc oxide nanorod, the preparation method of which is to combine water-soluble zinc salt, water-soluble copper salt, polyvinylpyrrolidone, hexamethylenetetramine and water After mixing, a hydrothermal reaction is performed to obtain copper-doped zinc oxide nanorods; specifically, the aqueous solutions of zinc nitrate hexahydrate, copper nitrate trihydrate and polyvinylpyrrolidone (PVP) are mixed and hexamethylenetetramine is added, and then Copper-doped zinc oxide nanorods were prepared by hydrothermal method.

In the present invention, the copper in the water-soluble copper salt is 1 to 10% of the molar amount of zinc in the water-soluble zinc salt, preferably 3 to 7%, and further preferably 4 to 6%, such as 5%.

In the present invention, the mass ratio of water-soluble zinc salt, polyvinylpyrrolidone and hexamethylenetetramine is (6-12): (5-10): (3-6), preferably (6-7): ( 5～6): (3～4), such as 6:5:3.

In the present invention, the hydrothermal reaction is carried out at 80-100°C for 5-8 hours, preferably at 90°C for 6 hours.

The invention discloses a method for removing organic pollutants from water bodies. The above-mentioned copper-doped zinc oxide nanorods are placed into water bodies containing organic pollutants and treated with light and/or ultrasonic to complete the removal of organic pollutants from water bodies. Preferably, the organic pollutant is bisphenol A; the light is visible light.

beneficial effects

Advantages of the present invention: 1. The preparation method of the copper-doped zinc oxide nanorods disclosed in the present invention is simple and has regular morphology. In particular, no calcination is required, which overcomes the prior art belief that calcination is required to prepare zinc oxide or doped zinc oxide catalysts. Technical bias; the raw materials used are common and easily available; the morphology of one-dimensional nanorods can provide a fast channel for electron migration; the doping of copper elements can improve the light absorption capacity of zinc oxide semiconductor, thereby improving its photocatalytic effect; 2. In the copper-doped zinc oxide nanorods disclosed in the present invention, the piezoelectricity is adjusted and the radial piezoelectricity is enhanced, thereby promoting the separation and migration of internal photogenerated charges; under the combined action of visible light and ultrasound, the catalyst shows significant Improved performance; 3. After multiple cycles of the copper-doped zinc oxide nanorods disclosed in the present invention, the catalytic performance of the catalyst has not been significantly reduced and the structural morphology has not changed, indicating that its structure and properties are stable.

Description of the drawings

Figure 1 is a scanning electron microscope photo of copper-doped zinc oxide nanorods.

Figure 2 is a transmission electron microscope photo of copper-doped zinc oxide nanorods.

Figure 3 shows the experimental results of photocatalytic degradation of bisphenol A in water by different catalysts.

Figure 4 shows the experimental results of piezoelectric catalytic degradation of bisphenol A in water with different catalysts.

Figure 5 shows the degradation effect of copper-doped zinc oxide nanorods on bisphenol A under different conditions.

Figure 6 shows the kinetic fitting curve of the piezoelectric-photocatalytic degradation experiment of bisphenol A in water.

Figure 7 is a graph showing the cyclic degradation of bisphenol A by copper-doped zinc oxide nanorods.

Figure 8 shows the SEM images of 1% Cu-ZnO and 10% Cu-ZnO with different doping amounts.

Embodiments of the invention

In the catalyst of the present invention, when stress is applied to the unit cell, the centers of positive and negative ions will move in opposite directions, resulting in dipolar polarization (ion charge) and a built-in electric field (piezoelectric field). When the dipole moment superposition occurs in the entire unit, an electric potential distributed along the stress direction will be generated, that is, the piezoelectric potential.

In the present invention, an aqueous solution of zinc nitrate hexahydrate and polyvinylpyrrolidone (PVP) is stirred evenly, then hexamethylenetetramine is added, and then zinc oxide nanorods are prepared by a hydrothermal method as a comparison. Specifically, first weigh 0.6~1.2 g zinc nitrate hexahydrate and 0.5~1.0 g PVP and dissolve it in 40~80 mL deionized water. After stirring evenly, add 0.3~0.6 g hexamethylenetetramine and continue stirring for 30~60 min. Then, transfer the evenly stirred solution to the liner of a reaction kettle with a capacity of 50 mL, seal it, and place it in a blast oven at 90 to 180 ^o C for reaction for 6 to 9 hours. After cooling to room temperature, it is centrifuged and washed several times with deionized water and absolute ethanol, and then dried to obtain zinc oxide nanorods.

The preparation method of copper-doped zinc oxide nanorods of the present invention is specifically as follows: first, weigh 0.6~1.2 g zinc nitrate hexahydrate, 25~50 mg copper nitrate trihydrate and 0.5~1.0 g PVP and dissolve them in 40~80 mL deionized water. water, stir evenly, add 0.3~0.6 g hexamethylenetetramine, and continue stirring for 30~60 min. Then, transfer the evenly stirred solution to the liner of a reaction kettle with a capacity of 50 mL, seal it, and place it in a blast oven at 90 to 180 ^o C for reaction for 6 to 9 hours. After cooling to room temperature, it is centrifuged and washed several times with deionized water and absolute ethanol, and then dried to obtain copper-doped zinc oxide nanorods.

Piezoelectric synergistic photocatalytic degradation experiment: Put the above-mentioned nanomaterials into an aqueous solution containing bisphenol A, avoid light and adsorb for one hour, and then use ultrasound and simulated solar light sources to remove organic pollutants in the water.

Zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ ∙6H ₂ O) was purchased from Sigma-Aldrich. Hexamethylenetetramine (C ₆ H ₁₂ N ₄ ), copper nitrate trihydrate (Cu(NO ₃ ) ₂ ∙3H ₂ O) and vanadium pentoxide (V ₂ O ₅ ) were purchased from Sinopharm Chemical Reagent Co., Ltd. . Polyvinylpyrrolidone (PVP, M _w =40000) and bisphenol A (C ₁₅ H ₁₆ O ₂ ) were purchased from TCI. The raw materials used in the present invention are all existing products, and the specific preparation operations and testing methods are conventional technologies. For example, stirring is a conventional mixing method in this field.

Example 1: Preparation of zinc oxide nanorods, the specific steps are as follows: Dissolve 0.6 g zinc nitrate hexahydrate and 0.5 g PVP in 40 mL deionized water, stir for 3 minutes, add 0.3 g hexamethylenetetramine, and continue. Stir for 30 minutes, then put the solution into the reaction kettle and react at 90 ^° C for 6 hours; after cooling to room temperature, centrifuge and wash 3 times with deionized water and absolute ethanol, and then dry to obtain zinc oxide nanorods.

Example 2: Preparation of copper-doped zinc oxide nanorods, the specific steps are as follows: Weigh 0.6 g zinc nitrate hexahydrate, 25 mg copper nitrate trihydrate and 0.5 g PVP and dissolve them in 40 mL deionized water, stir for 3 minutes and then add 0.3 g hexamethylenetetramine, continue stirring for 30 minutes, then put the solution into the reaction kettle, react at 90 ^° C for 6 hours, cool to room temperature, and then centrifuge and wash 3 times with deionized water and absolute ethanol. After drying, the copper-doped zinc oxide nanorods are obtained, which is 5% Cu-ZnO. The molar amount of copper is 5% of the molar amount of zinc.

Figure 1 is a scanning electron microscope image of the above-mentioned copper-doped zinc oxide nanorods, and Figure 2 is a transmission electron microscope image of the above-mentioned copper-doped zinc oxide nanorods. It can be clearly seen from the figure that the copper-doped zinc oxide nanorods are regular Uniform one-dimensional nanorod morphology and solid structure.

Comparative Example 1: Dissolve 0.6 g zinc nitrate hexahydrate, 9 mg vanadium pentoxide and 0.5 g PVP in 40 mL deionized water, stir for 3 minutes, add 0.3 g hexamethylenetetramine, and continue stirring for 30 minutes. Then, the solution was put into the reaction kettle and reacted at 90 ^° C for 6 hours; after cooling to room temperature, it was centrifuged and washed three times with deionized water and absolute ethanol, and then dried to obtain vanadium-doped zinc oxide nanorods, 5% V -ZnO.

Example 3 Photocatalytic degradation experiment of bisphenol A in water.

Weigh 25 mg of the 5% Cu-ZnO catalyst obtained in Example 2 and add it to 50 ml of an aqueous solution containing bisphenol A (concentration: 10 mg/L). First, adsorb in dark conditions to avoid light for 1 hour to achieve adsorption equilibrium. After equilibrium, start the photocatalytic degradation experiment. Use a 300 W xenon lamp as a simulated solar light source. Take 1 ml every 30 minutes, filter it with a filter head and inject it into a high-performance liquid phase sample bottle. Use a high-performance liquid chromatograph in deionized water: methanol = Test the absorption curve of the sample at 290 nm ultraviolet wavelength in the mobile phase of 30:70, record the bisphenol A peak area at about 6 minutes, and record the initial bisphenol A concentration as 100% to obtain the bisphenol A concentration. Photocatalytic degradation curve.

Weigh 25 mg of the catalyst obtained in Example 1 and Comparative Example 1 to conduct the same photocatalytic degradation experiment of bisphenol A in water. The results are shown in Figure 3.

Example 4 Piezoelectric catalytic degradation experiment of bisphenol A in water.

Weigh 25 mg of the copper-doped zinc oxide nanorods obtained in Example 2 (5% Cu-ZnO), added to 50 ml of aqueous solution containing bisphenol A (concentration 10 mg/L). First, adsorb in dark conditions to avoid light for 1 hour to achieve adsorption equilibrium. After equilibration, start the piezoelectric degradation experiment using 150 W (40 kHz) ultrasonic cleaning machine as the ultrasonic source, take 1 ml every 30 minutes, filter it with a filter head and inject it into a high-performance liquid phase sample bottle, use a high-performance liquid chromatograph in the mobile phase of deionized water: methanol = 30:70 The absorption curve of the test sample at a UV wavelength of 290 nm was recorded, and the bisphenol A peak area at about 6 minutes was recorded. The initial bisphenol A concentration was recorded as 100% to obtain the piezoelectric catalytic degradation curve of bisphenol A.

Weigh 25 mg of the catalyst obtained in Example 1 and Comparative Example 1 and conduct the same piezoelectric catalytic degradation experiment of bisphenol A in water. The results are shown in Figure 4.

Example 5 Piezoelectric-photocatalytic degradation experiment of copper-doped zinc oxide nanorods on bisphenol A in water.

Weigh 25 mg of the copper-doped zinc oxide nanorods obtained in Example 2 (5% Cu-ZnO), added to 50 ml of aqueous solution containing bisphenol A (concentration 10 mg/L). First, adsorb in dark conditions to avoid light for 1 hour to achieve adsorption equilibrium. After equilibrium, the piezoelectric-photodegradation experiment was started, using a 300 W xenon lamp as a simulated solar light source and a 150 W (40 kHz) ultrasonic cleaning machine as the ultrasonic source, take 1 ml every 30 minutes, filter it with a filter head and inject it into a high-performance liquid phase sample bottle, use a high-performance liquid chromatograph in the mobile phase of deionized water: methanol = 30:70 Test the absorption curve of the sample at a UV wavelength of 290 nm, record the bisphenol A peak area at about 6 minutes, and record the initial bisphenol A concentration as 100% to obtain the piezoelectric-photocatalytic degradation curve of bisphenol A. . Figure 5 is the degradation curve of bisphenol A in water by copper-doped zinc oxide nanorods under different conditions. Under the combined action of ultrasound and light, the degradation effect of copper-doped zinc oxide nanorods is significantly improved. During piezoelectric-photocatalytic degradation for 120 minutes, the removal rate of bisphenol A in water reaches 97%, which is much higher than that of zinc oxide alone. Nano stave.

Weigh 25 mg of the catalyst obtained in Example 1 and Comparative Example 1 and conduct piezoelectric-photocatalytic degradation experiments of bisphenol A in the same water respectively. Use conventional methods to perform kinetic fitting. The kinetic fitting curve in Figure 6 It shows that Cu-ZnO has the fastest piezoelectric-photocatalytic degradation rate and V-ZnO has the slowest piezoelectric-photocatalytic degradation rate; the piezoelectric-photocatalytic degradation rate of Cu-ZnO nanorods (0.0281 min ^-1 ) is V -2.2 times the photocatalytic rate of ZnO (0.0126 min ^-1 ). The results of piezoelectric-photocatalysis well combine the conclusions of photocatalysis and piezoelectric catalysis. 5% Cu-ZnO not only improves the photocatalytic activity but also enhances the piezoelectricity, so it shows the highest piezoelectric-photocatalytic activity. .

Preliminary experiments found that zinc oxide nanorods were first prepared and then hydrothermally reacted with copper nitrate trihydrate to obtain a composite catalyst. The piezoelectric-photocatalytic degradation of bisphenol A was not as effective as zinc oxide nanorods alone.

Example 6 Experiment on the cyclic degradation of bisphenol A in water by copper-doped zinc oxide nanorods.

The copper-doped zinc oxide nanorods in Example 5 were collected by centrifugation, and then the collected catalyst was dried in an oven at 60 ^° C for 12 hours. The dried catalyst was again placed in 50 mL of bisphenol A (concentration: 10 mg/L) aqueous solution, protected from light, and stirred until adsorption equilibrium. After equilibrium, start the piezoelectric-photodegradation experiment. Use a 300 W xenon lamp as the simulated sunlight source and a 150 W ultrasonic cleaner as the ultrasonic source. Take 1 ml every 30 minutes, filter it with a filter head and inject it into a high-efficiency liquid phase sample bottle. Use a high-performance liquid chromatograph to test the absorption curve of the sample at a UV wavelength of 290 nm in a mobile phase of deionized water: methanol = 30:70, record the peak area of bisphenol A at about 6 minutes, and refer to the standard curve to obtain The residual concentration of bisphenol A in the corresponding water samples. Repeat this method three times and record the degradation curve of bisphenol A.

Figure 7 is a cyclic degradation diagram of copper-doped zinc oxide nanorods. It can be seen from the figure that the performance of the catalyst is stable and it still maintains good catalytic performance during three cycles of degradation. This shows that copper-doped zinc oxide nanorods have better stability and have strong potential for practical applications.

Comparative Example 2: Use the same test method as Example 5 to test 5% of Comparative Example 1 The piezoelectric-photocatalytic degradation effect of the V-ZnO catalyst. When the piezoelectric-photocatalytic degradation was performed for 120 minutes, the residual rate of bisphenol A in the water was 24.8%, which was not as good as that of zinc oxide nanorods alone.

Example 7: Based on Example 2, 1% Cu-ZnO and 10% Cu-ZnO were prepared by changing the amount of Cu(NO ₃ ) ₂ ∙3H ₂ O added to adjust the doping ratio. SEM image See Figure 8 respectively. Using the same testing method as in Example 5, the piezoelectric-photocatalytic degradation performance is not as good as 5% Cu-ZnO.

Example 8: Adjust the initial concentration of bisphenol A to 5 in the experiment of Example 5 mg/L, when piezoelectric-photocatalytic degradation occurs for 60 minutes, the removal rate of bisphenol A in water reaches more than 90%; when piezoelectric-photocatalytic degradation occurs for 90 minutes, the removal rate of bisphenol A in water reaches more than 96% ; Bisphenol A in water was completely removed after 120 minutes of piezoelectric-photodegradation.

The invention discloses a nanomaterial for piezoelectric synergistic visible light catalytic degradation of organic pollutants, its preparation method and its effective removal of organic pollutants (such as bisphenol A) in water bodies. Copper element was incorporated into zinc oxide crystals through a simple hydrothermal method to obtain copper-doped zinc oxide nanorods. Zinc oxide is a commonly used photocatalyst, but pure zinc oxide only responds to ultraviolet light, and its application is limited. The present invention synthesizes copper-doped zinc oxide nanorods, and introduces copper elements into zinc oxide to adjust the piezoelectricity of zinc oxide. And improve the light absorption capacity, thereby improving the catalytic performance of zinc oxide. By adding ultrasound-assisted photocatalysis, the purpose of quickly and effectively degrading organic pollutants in water can be achieved, and it can be recycled to reduce costs.

Claims

A method for preparing copper-doped zinc oxide nanorods, which is characterized in that after mixing water-soluble zinc salts, water-soluble copper salts, polyvinylpyrrolidone, hexamethylenetetramine and water, a hydrothermal reaction is performed to obtain copper Doped zinc oxide nanorods.
The preparation method of copper-doped zinc oxide nanorods according to claim 1, characterized in that, after mixing zinc nitrate hexahydrate, copper nitrate trihydrate, polyvinylpyrrolidone and water, hexamethylenetetramine is added, and then water is passed through Copper-doped zinc oxide nanorods were prepared by thermal method.
The method for preparing copper-doped zinc oxide nanorods according to claim 1, wherein the copper in the water-soluble copper salt is 1 to 10% of the molar amount of zinc in the water-soluble zinc salt.
The preparation method of copper-doped zinc oxide nanorods according to claim 1, characterized in that the mass ratio of water-soluble zinc salt, polyvinylpyrrolidone, and hexamethylenetetramine is (6-12): (5-10 ): (3～6).
The preparation method of copper-doped zinc oxide nanorods according to claim 1, characterized in that the hydrothermal reaction is 80-100°C for 5-8 hours.
Copper-doped zinc oxide nanorods prepared according to the preparation method of copper-doped zinc oxide nanorods according to claim 1.
The application of copper-doped zinc oxide nanorods in removing organic pollutants according to claim 6.
The application according to claim 7, characterized in that the removal method is photocatalysis and/or piezoelectric catalysis.
A method for removing organic pollutants in water, characterized in that the copper-doped zinc oxide nanorods of claim 6 are placed in water containing organic pollutants, and treated with light and/or ultrasonic to complete the removal of organic pollutants in water. Remove.
The method for removing organic pollutants from water according to claim 9, wherein the organic pollutants are bisphenol A and the light is visible light.