Transition metal-nitrogen-carbon defect piezoelectric material and preparation method and application thereof

Abstract

The invention discloses a transition metal-nitrogen-carbon defect piezoelectric material and a preparation method and application thereof.The preparation method comprises the steps that Zn (NO3) 2.6 H2O, FeSO4. 7H2O, polyvinyl pyrrolidone and 2-methylimidazole are dissolved in a methanol solution to be fully stirred and react to obtain a mixed material, then the mixed material is subjected to centrifugal treatment, and ZnFe-ZIF nanocrystals are obtained; and dispersing the ZnFe-ZIF nanocrystals in a methanol solution, adding tannic acid, carrying out fixed-time etching to obtain a reaction product, carrying out high-temperature calcination on the reaction product in a nitrogen atmosphere, and cooling to obtain the piezoelectric material with the carbon defect structure. The piezoelectric material with the carbon defect structure is used for sewage catalytic treatment. The catalyst is simple in preparation method, low in cost, convenient to operate and good in repeatability, the obtained material can effectively achieve piezoelectric catalytic degradation of organic pollutants, and a green, efficient and feasible scheme is provided for water environment pollution treatment.

Description

Technical Field

[0001] The present invention relates to the technical fields of preparation of piezoelectric catalytic materials and sewage treatment, and more specifically to a transition metal-nitrogen-carbon defect piezoelectric material, a preparation method thereof, and an application thereof. Background Art

[0002] As emerging organic pollutants, pharmaceuticals and personal care products have attracted much attention due to their high persistence in wastewater treatment and high detection rates in various water bodies. Carbamazepine is one of them and is widely used in the treatment of epilepsy and neuralgia, with an annual consumption of more than 1000 tons. After oral administration, about 30% is not absorbed by the human body and is discharged into the sewage system, which results in its large amount of residue in natural water bodies, ultimately affecting environmental safety and human health. Therefore, it is necessary to develop an economical and effective treatment technology to deal with residual carbamazepine. So far, researchers have explored treatment technologies including adsorption, advanced oxidation, and reverse osmosis to remove carbamazepine from wastewater. For example, the Chinese invention patent application with the patent application number 201811009283.0 discloses a method for photocatalytic degradation of carbamazepine by g-C3N4 / BiOBr. A protonated g-C3N4 / BiOBr photocatalyst is added to the water to be treated containing carbamazepine, and then photocatalytic degradation is carried out under simulated sunlight. This method can effectively degrade carbamazepine in water bodies, but it must work synergistically under simulated sunlight and cannot work effectively in the dark environment, which limits its large-scale application and development.

[0003] Piezoelectric catalysis is a technology that uses the piezoelectric effect of piezoelectric materials to convert mechanical energy into chemical energy, thereby achieving the removal of organic pollutants. Its energy source is extensive and can be external mechanical stimuli such as ultrasonic waves, water flow, waves, wind energy, and mechanical vibration. At the same time, it has the advantages of zero chemical addition, operability in the dark environment, and rapid reaction. These characteristics make the piezoelectric catalysis technology a green solution for treating organic pollutants in water bodies.

[0004] The construction of carbon defects and the doping of transition metal species contribute to promoting piezoelectric catalytic activity. Specifically, the coordination of transition metals on the carbon carrier creates more metal active centers. From the perspective of defect chemistry, these metal active centers can be regarded as carbon lattice defects, endowing it with excellent piezoelectric catalytic performance. However, there are few studies on the piezoelectric catalytic degradation of organic pollutants using transition metal-doped materials with carbon defect structures. Summary of the Invention

[0005] In view of this, the present invention provides a transition metal-nitrogen-carbon defect piezoelectric material and a preparation method thereof, which solve the technical problem of removing carbamazepine in the process of sewage purification, are simple to prepare, low in cost, convenient to operate, and have good repeatability.

[0006] To achieve the above object, the present invention adopts the following technical solutions: First, the present invention provides a method for preparing a transition metal-nitrogen-carbon defect piezoelectric material, comprising the following steps: (1) Dissolve Zn(NO3)2·6H2O and FeSO4·7H2O in a methanol solution to obtain a solution A; dissolve polyvinyl pyrrolidone and 2-methylimidazole in a methanol solution to obtain a solution B; mix the solution A and the solution B and stir them thoroughly to obtain a mixed material; (2) centrifuging the mixture to remove the supernatant, washing, and drying to obtain ZnFe-ZIF nanocrystals; (3) Dispersing ZnFe-ZIF nanocrystals in a methanol solution, adding a tannic acid solution for etching, and then centrifuging, washing, and drying to obtain a reaction product; (4) The reaction product is calcined at high temperature in a nitrogen atmosphere and then cooled to obtain a piezoelectric material with a carbon defect structure.

[0007] Preferably, in step (1), the mass ratio of Zn(NO3)2·6H2O to FeSO4·7H2O is (28.0-38.0):1, the mass ratio of polyvinyl pyrrolidone to 2-methylimidazole is (0.5-1.5):(0.4-1.4), and the stirring reaction time is 0.1-24 h.

[0008] Preferably, in step (2), the centrifugal speed is 5000 rpm, the time is 5 min, methanol is used for washing, the drying temperature is 40-80° C., and the drying time is 0.1-20 h.

[0009] Preferably, the concentration of the tannic acid solution in step (3) is 1-8 g / L, the mass ratio of ZnFe-ZIF nanocrystals to tannic acid solution is 1:(2.5-4.0), the etching time is 0.1-15 min, the centrifugal speed is 5000 rpm, the time is 5 min, methanol is used for washing, the drying temperature is 40-80 ° C, and the drying time is 0.1-20 h.

[0010] Preferably, in step (4), the calcination temperature is 300-900° C. and the holding time is 1-5 h.

[0011] Preferably, the heating rate during the calcination process is 1-8°C / min.

[0012] The present invention also provides a transition metal-nitrogen-carbon defect piezoelectric material prepared by the above technical solution.

[0013] The present invention also provides a transition metal-nitrogen-carbon defect piezoelectric material prepared by the above technical solution or the use of the transition metal-nitrogen-carbon defect piezoelectric material in sewage treatment.

[0014] Furthermore, the addition amount of the transition metal-nitrogen-carbon defective piezoelectric material in sewage treatment is 0.001-10 mg / mL, and the ultrasonic excitation catalytic process is carried out at a power of 20-1000 Hz, and the reaction time is 0.01-3 h.

[0015] Preferably, the sewage is sewage containing carbamazepine, the concentration of carbamazepine in the sewage is 10 mg / L, the pH of the sewage is 3-11, and the dosage of the transition metal-nitrogen-carbon defective piezoelectric material is 0.25 g / L based on the volume of the sewage.

[0016] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a transition metal-nitrogen-carbon defective piezoelectric material, its preparation method and application, and has the following beneficial effects: Through the coordination of transition metals on the carbon carrier, the present invention creates more metal active centers, which can induce polarization potential under ultrasonic excitation, thereby improving the efficiency of piezoelectric electron transport and achieving better piezoelectric catalytic performance; the transition metal-nitrogen-carbon defective piezoelectric material prepared by the present invention can effectively remove the organic pollutant carbamazepine in water by piezoelectric catalysis under normal temperature and pressure conditions. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0018] Figure 1 For the piezoelectric catalytic removal effect of the materials prepared in Example 1 and Comparative Examples 1-2 on carbamazepine; Figure 2 For the field emission scanning electron microscope (SEM) images and high-resolution field emission scanning transmission electron microscope (HRTEM) images of the materials prepared in Example 1 and Comparative Example 2; Figure 3 For the electron paramagnetic resonance (EPR) images of the materials prepared in Example 1 and Comparative Examples 1-2; Figure 4 For the Fe-NC H energy dispersive X-ray spectroscopy (EDS) image of the material prepared in Example 1; Figure 5 For the piezoelectric response force microscopy (PFM) images of the materials prepared in Example 1 and Comparative Examples 1-2; Figure 6 For the Fe-NC HPiezo-catalytic degradation effect diagrams of carbamazepine with different addition amounts of materials; Figure 7 Fe-NC prepared in Example 1 H Piezo-catalytic degradation effect diagrams of carbamazepine with different initial pH conditions of materials; Figure 8 Fe-NC prepared in Example 1 H Piezo-catalytic degradation effect diagrams of carbamazepine for 5-cycle experiments of materials. Detailed implementation manners

[0019] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] Example 1 Preparation of transition metal-nitrogen-carbon defect material (Fe-NC H ) (1) Dissolve 0.575 g of Zn(NO3)2·6H2O and 0.019 g of FeSO4·7H2O in 50 mL of methanol to obtain solution A; dissolve 0.60 g of polyvinylpyrrolidone and 0.66 g of 2-methylimidazole in 50 mL of methanol to obtain solution B, and then mix solution A and solution B to obtain a mixed material; (2) Continuously stir the mixed material at room temperature for 24 h, centrifuge at 5000 rpm for 5 min to remove the supernatant, wash it 3 times with methanol, and dry it in an oven at 70 °C for 12 h to obtain ZnFe-ZIF nanocrystals; (3) Disperse 0.10 g of ZnFe-ZIF nanocrystals in 10 mL of methanol solution, add it to 40 mL of tannic acid solution with a concentration of 8 g / L for etching for 10 min, centrifuge at 5000 rpm for 5 min, wash it 3 times with methanol solution, and dry it in an oven at 70 °C for 12 h to obtain etched ZnFe-ZIF nanocrystals; (4) Under a nitrogen atmosphere, place the obtained etched ZnFe-ZIF nanocrystals in a tube furnace for heating and calcination, with a heating rate of 2 °C / min, heat up to 800 °C, keep it for 3 h after heating up, and cool it to room temperature after calcination to obtain Fe-NC H material.

[0021] Comparative Example 1 Preparation of nitrogen-carbon material (NC): (1) Dissolve 0.89 g of Zn(NO3)2·6H2O in 30 mL of methanol to obtain solution A; dissolve 1.97 g of 2-methylimidazole in 20 mL of methanol to obtain solution B, and then mix solution A and solution B to obtain a mixed material; (2) Continuously stir the mixed material at room temperature for 24 h, centrifuge at 5000 rpm for 5 min to remove the supernatant, wash it 3 times with methanol solution, and dry it in an oven at 70 °C for 12 h to obtain the ZIF-8 material; (3) Under a nitrogen atmosphere, place the ZIF-8 material in a tubular furnace for temperature-raising calcination, with a heating rate of 2 °C / min, heat up to 800 °C, keep it for 3 h after heating, and cool it to room temperature after calcination to obtain the NC material.

[0022] Comparative Example 2 Preparation of transition metal-nitrogen-carbon material (Fe-NC): (1) Dissolve 0.575 g of Zn(NO3)2·6H2O and 0.019 g of FeSO4·7H2O in 50 mL of methanol to obtain solution A; dissolve 0.60 g of polyvinylpyrrolidone and 0.66 g of 2-methylimidazole in 50 mL of methanol to obtain solution B, and then mix solution A and solution B to obtain a mixed material; (2) Continuously stir the mixed material at room temperature for 24 h, centrifuge at 5000 rpm for 5 min to remove the supernatant, wash it 3 times with methanol solution, and dry it in an oven at 70 °C for 12 h to obtain ZnFe-ZIF nanocrystals; (3) Under a nitrogen atmosphere, place the ZnFe-ZIF nanocrystals in a tubular furnace for temperature-raising calcination, with a heating rate of 2 °C / min, heat up to 800 °C, keep it for 3 h after heating, and cool it to room temperature after calcination to obtain the Fe-NC material.

[0023] Experimental Example I. Application of the materials prepared in Example 1 and Comparative Examples 1-2 in the degradation of organic pollutants (1) Dissolve 5 mg of carbamazepine powder in 500 mL of deionized water, and after sufficient stirring and dissolution, obtain a carbamazepine solution with a mass concentration of 10 mg / L; (2) Take 5 mg each of the Fe-NC H materials, NC materials, and Fe-NC materials prepared in Example 1 and Comparative Examples 1-2, and add them to 20 mL of 10 mg / L carbamazepine solution respectively. After adsorption for 30 min, trigger the piezoelectric catalytic reaction with ultrasound at a frequency of 50 Hz. After timed sampling, filter it with a 0.22 μm polytetrafluoroethylene filter membrane, and measure the concentration of the target pollutant with high performance liquid chromatography; the maximum reaction time is 100 min; set three replicate groups respectively.

[0024] The experimental results are as follows Figure 1 shown Figure 1 indicating that the piezoelectric degradation effect of NC materials on carbamazepine is limited, with a degradation rate of about 32%; the piezoelectric degradation effect of Fe-NC materials on carbamazepine is also limited, and the degradation rate is lower than that of NC materials on carbamazepine, only about 19%. This is because the introduction of excessive iron elements leads to aggregation and blockage of active sites; Fe-NC H materials have a significant piezoelectric degradation effect on carbamazepine. The degradation effect on carbamazepine within 100 min is about 100%, and its degradation effect is significantly better than the piezoelectric catalytic degradation effect of NC materials and Fe-NC materials on carbamazepine.

[0025] II. Material Characterization As follows Figure 2 shown, the Fe-NC material without tannic acid etching has a relatively regular rhombic dodecahedron structure, while the Fe-NC H material surface after tannic acid etching becomes significantly blurred and irregular, preliminarily indicating the successful preparation of transition metal-nitrogen-carbon defect materials. The attached Figure 3 electron paramagnetic resonance image further confirms the introduction of defects. From the attached Figure 4 energy-dispersive X-ray spectroscopy pattern, it can be seen that each element (Fe, N, O, and C) is evenly distributed throughout the framework.

[0026] Attached Figure 5 piezoresponse force microscopy images prove that the prepared Fe-NC H materials have excellent piezoelectric properties. The phase hysteresis loop of Fe-NC H materials is about 180° phase inversion under a scanning bias of -10 and +10 V. The typical butterfly-shaped amplitude loop further verifies its good piezoelectric properties, showing a maximum amplitude of 667 pm; in contrast, the maximum amplitudes of Fe-NC and NC materials are 558 pm and 485 pm respectively, which proves that Fe-NC H materials have stronger piezoelectric properties than Fe-NC and NC. Based on the maximum effective piezoelectric coefficient (d 33 ) value of the amplitude loop, NC (40.70 pm / V) < Fe-NC (47.40 pm / V) < Fe-NC H (55.67 pm / V), which also effectively proves that the Fe-NC H materials with introduced defects have excellent piezoelectric properties.

[0027] III. Verification of the addition amount, acid-base adaptability, and cycling performance of the materials prepared in Example 1 Sewage treatment was carried out by the method of the first part in the experimental example. Weigh Fe-NC materials with different masses (2 mg, 5 mg, 10 mg) and add them to a 20 mL carbamazepine water sample with a concentration of 10 mg / L. After adsorption for 30 min, the piezocatalytic reaction was triggered by ultrasound with a frequency of 50 Hz. After sampling at regular intervals, it was filtered through a 0.22 μm polytetrafluoroethylene filter membrane, and the concentration of the target pollutant was determined by high performance liquid chromatography. The maximum reaction time was 100 min, and three replicate groups were set respectively. The results are as follows H shown, Figure 6 indicating that Fe-NC Figure 6 materials can effectively degrade carbamazepine by piezocatalysis, and the treatment group with a mass concentration of 0.25 g / L shows better removal advantages for carbamazepine. H

[0028] As can be seen from the appendix Figure 7 Fe-NC H materials can effectively remove carbamazepine in water samples with different pH values (3 - 11) under the action of ultrasound, showing good acid-base adaptability. The pH of the organic pollutant was adjusted with 0.5 M hydrochloric acid or 0.5 M sodium hydroxide solution.

[0029] As can be seen from the appendix Figure 8 the transition metal-nitrogen-carbon defect piezomaterials have good stability. The degradation efficiency of Fe-NC H materials for carbamazepine still reached more than 92% after 4 cycles, proving that the piezocatalyst has good stability.

[0030] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.​

Claims

1. A preparation method of a transition metal-nitrogen-carbon defect piezoelectric material, characterized in that, The following steps are involved: (1) Dissolve Zn(NO3)2·6H2O and FeSO4·7H2O in a methanol solution to obtain a solution A; dissolve polyvinyl pyrrolidone and 2-methylimidazole in a methanol solution to obtain a solution B; mix the solution A and the solution B and stir them thoroughly to obtain a mixed material; (2) centrifuging the mixture to remove the supernatant, washing, and drying to obtain ZnFe-ZIF nanocrystals; (3) Dispersing ZnFe-ZIF nanocrystals in a methanol solution, adding a tannic acid solution for etching, and then centrifuging, washing, and drying to obtain a reaction product; (4) The reaction product is calcined in a nitrogen atmosphere and then cooled to obtain a piezoelectric material with a carbon defect structure.

2. The preparation method of a transition metal-nitrogen-carbon defective piezoelectric material according to claim 1, wherein In step (1), the mass ratio of Zn(NO3)2·6H2O to FeSO4·7H2O is (28.0-38.0):1, the mass ratio of polyvinyl pyrrolidone to 2-methylimidazole is (0.5-1.5):(0.4-1.4), and the stirring reaction time is 0.1-24 h.

3. The preparation method of a transition metal-nitrogen-carbon defect piezoelectric material according to claim 1, characterized in that, In step (2), the centrifugal speed is 5000 rpm, the time is 5 minutes, methanol is used for washing, the drying temperature is 40-80°C, and the drying time is 0.1-20 hours.

4. The preparation method of a transition metal-nitrogen-carbon defective piezoelectric material according to claim 1, wherein, The concentration of the tannic acid solution in step (3) is 1-8 g / L, the mass ratio of ZnFe-ZIF nanocrystals to tannic acid solution is 1:(2.5-4.0), the etching time is 0.1-15 min, the centrifugal speed is 5000 rpm, the time is 5 min, methanol is used for washing, the drying temperature is 40-80 ° C, and the drying time is 0.1-20 h.

5. The preparation method of a transition metal-nitrogen-carbon defective piezoelectric material according to claim 1, characterized in that, In step (4), the calcination temperature is 300-900°C and the holding time is 1-5 hours.

6. The preparation method of a transition metal-nitrogen-carbon defective piezoelectric material according to claim 1 or 5, characterized in that, The heating rate during the calcination process is 1~8℃ / min. 7 . A transition metal-nitrogen-carbon defect piezoelectric material prepared by the method for preparing a transition metal-nitrogen-carbon defect piezoelectric material according to any one of claims 1 to 6 .

8. Use of the transition metal-nitrogen-carbon defect piezoelectric material prepared by the preparation method of the transition metal-nitrogen-carbon defect piezoelectric material according to any one of claims 1 to 6 in sewage treatment.

9. The application according to claim 8, wherein The addition amount of the transition metal-nitrogen-carbon defect piezoelectric material in sewage treatment is 0.001-10 mg / mL, the catalytic process is excited by ultrasound with a power of 20-1000 Hz, and the reaction time is 0.01-3 hours.

10. The application according to claim 8 or 9, characterized in that, The sewage contains carbamazepine, the concentration of carbamazepine in the sewage is 10 mg / L, the pH of the sewage is 3-11, and the amount of the transition metal-nitrogen-carbon defect piezoelectric material used is 0.25 g / L based on the volume of the sewage.

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