Preparation Method of a Fe / Nv-PCN Piezoelectric Material

Abstract

The present invention is applicable to the field of environmental governance technologies, and particularly relates to a preparation method of an Fe / Nv-PCN piezoelectric material. The method includes: in-situ synthesizing a PCN material: calcining urea to obtain the PCN material; synthesizing an Nv-PCN material: calcining the PCN material under a nitrogen atmosphere to obtain the Nv-PCN material; preparing Fe3O4 nanoparticles using ferric chloride FeCl3·6H2O and ferrous sulfate FeSO4·7H2O as iron sources; loading the Fe3O4 nanoparticles onto the Nv-PCN material by an in-situ co-precipitation method, cooling to room temperature after the reaction is completed, taking out, washing successively with deionized water and absolute ethanol, and then drying under a closed condition to obtain an Fe / Nv-PCN composite material. Through the synergistic effect of iron doping and nitrogen vacancies, the present invention significantly improves the piezoelectric performance and catalytic activity. Iron doping enhances the electron transport ability and redox activity of the material, while nitrogen vacancies optimize the energy band structure of the material, improving the piezoelectric effect and free radical generation efficiency; this material simultaneously has dual functions of adsorption and catalytic oxidation and can degrade pollutants in a long-term manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental governance, and particularly relates to a preparation method of Fe / Nv-PCN piezoelectric material. Background Art

[0002] The efficient, green and low-cost treatment of organic-polluted groundwater and wastewater is a major environmental demand currently faced. The most widely used technology for treating organic-polluted water is the advanced oxidation process. Traditional reagent oxidation technologies need to add a large amount of oxidants, catalytic materials or adopt other catalytic methods to the water body, and there are problems such as high cost and easy generation of secondary pollution as a whole. Therefore, seeking methods for low consumption, low cost and long-term degradation of organic pollutants has become the forefront technology and development trend in the current treatment of organic-polluted groundwater and wastewater.

[0003] Piezoelectrocatalysis is a newly emerging advanced oxidation technology for water purification in recent years, which has attracted much attention due to its advantages such as no chemical addition, rapid reaction and no secondary pollution; it has obvious advantages compared with traditional oxidation technologies. Piezoelectric materials can generate electrical energy when subjected to pressure due to their unique piezoelectric effect, and this characteristic provides a new idea for environmental governance. However, existing piezoelectric materials have defects such as low activity and poor stability in environmental applications, and it is difficult to meet the actual needs. Developing an efficient, stable and environmentally friendly piezoelectric material has important practical significance.

[0004] Since traditional piezoelectric materials (such as PZT) contain lead and belong to high-energy-consuming preparation processes, there is a risk of heavy metal leakage when used for water treatment, and it is difficult to meet the requirements of green environmental protection. Moreover, traditional piezoelectric materials (such as BaTiO3, ZnO) have problems such as low catalytic activity, narrow response bandwidth and poor chemical stability; existing piezoelectric catalysts (such as TiO2) require ultraviolet light excitation, with high energy consumption and poor response to visible light. Polymer-based piezoelectric materials (such as PVDF) have low catalytic activity and are difficult to work stably in complex environments (such as acidic wastewater). Porous carbon-based materials (such as g-C3N4) have adsorption properties and visible light response, but have a low piezoelectric coefficient (<5 pm / V), weak piezoelectric effect (d33<10 pC / N), and a high electron-hole recombination rate, and cannot achieve high-performance synergistic conversion of mechanical energy-chemical energy, resulting in insufficient pollutant degradation efficiency. Single modification means (such as metal doping) have limited improvement in pollutant degradation efficiency (<40%), and lack a charge separation and active site synergy mechanism. Existing nitrogen vacancy (Nv) modification methods mostly rely on high-temperature ammonia treatment, with complex processes and uneven vacancy distribution. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of Fe / Nv-PCN piezoelectric material, aiming to solve the problems of weak piezoelectric effect and lack of charge separation and active site synergy mechanism of existing piezoelectric materials.

[0006] The present invention is achieved as follows. A preparation method of Fe / Nv-PCN piezoelectric material, the method comprising:

[0007] In-situ synthesis of PCN material: Calcining urea to obtain PCN material;

[0008] Synthesis of Nv-PCN material: Under a nitrogen atmosphere, calcining the PCN material to obtain Nv-PCN material;

[0009] Preparation of Fe / Nv-PCN composite material: Loading Fe3O4 nanoparticles onto Nv-PCN material by in-situ co-precipitation method. After the reaction is completed, it is cooled to room temperature, taken out, washed successively with deionized water and absolute ethanol, and then dried in a sealed manner to obtain Fe / Nv-PCN composite material, wherein the Fe3O4 nanoparticles are prepared using ferric chloride FeCl3·6H2O and ferrous sulfate FeSO4·7H2O as iron sources.

[0010] Preferably, in the step of calcining urea to obtain PCN material, during calcination, the heating rate is 2.5 - 10 °C / min, heating up to 550 °C, and holding for 2 - 4 h.

[0011] Preferably, after holding, it is cooled to room temperature, the product is collected, ground into powder, washed repeatedly with deionized water, and after washing is completed, dried in a vacuum environment at 80 °C for 12 h.

[0012] Preferably, in the step of calcining the PCN material under a nitrogen atmosphere to obtain Nv-PCN material, the PCN material is calcined in a tubular furnace, and during calcination, it is held for 2 - 4 h, wherein the flow rate of nitrogen is 100 ml / min.

[0013] Preferably, after calcination, it is cooled to room temperature, washed with deionized water and ethanol, and dried in a vacuum environment at 80 °C for 12 h to obtain Nv-PCN material.

[0014] Preferably, the steps for preparing Fe / Nv-PCN composite material include:

[0015] Dispersing Nv-PCN material in a mixed solution of ethanol and water, and performing ultrasonic treatment to obtain an ultrasonic suspension of Nv-PCN material;

[0016] Dissolving FeSO4·7H2O and FeCl3·6H2O in deionized water, and adding it to the ultrasonic suspension of Nv-PCN material;

[0017] Stirring at a temperature of 80 °C for 10 - 20 min, adjusting the pH to 11, and continuing to stir to obtain a black mixture;

[0018] Cool it naturally to room temperature, wash it several times, and then dry it in an oven to obtain the Fe / Nv-PCN composite material.

[0019] Preferably, the volume ratio of ethanol to water is 1:1, and the molar ratio of FeSO4·7H2O to FeCl3·6H2O is 5:3 to 5:4.

[0020] The preparation method of an Fe / Nv-PCN piezoelectric material provided by the present invention significantly improves the piezoelectric performance and catalytic activity through the synergistic effect of iron doping and nitrogen vacancies. Iron doping enhances the electron transport ability and redox activity of the material, while nitrogen vacancies optimize the energy band structure of the material, improving the piezoelectric effect and free radical generation efficiency; this material simultaneously has dual functions of adsorption and catalytic oxidation and can degrade pollutants for a long time. Description of the Drawings

[0021] Figure 1 It is the X-ray diffraction pattern of PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials provided by the embodiments of the present invention;

[0022] Figure 2 It is the Fourier transform infrared spectrum of PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials provided by the embodiments of the present invention;

[0023] Figure 3 It is the valence band X-ray photoelectron energy spectrum of PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials provided by the embodiments of the present invention;

[0024] Figure 4 It is the degradation effect diagram of Fe / Nv-PCN piezoelectric materials prepared from different raw materials provided by the embodiments of the present invention;

[0025] Figure 5 It is the first degradation effect diagram of Fe / Nv-PCN piezoelectric materials under different heating rates, different heat preservation times, and ultrasonic conditions provided by the embodiments of the present invention;

[0026] Figure 6 It is the second degradation effect diagram of Fe / Nv-PCN piezoelectric materials under different heating rates, different heat preservation times, and standing conditions provided by the embodiments of the present invention;

[0027] Figure 7 It is the experimental result of degrading water samples containing antibiotic pollutants using different catalysts provided by the embodiments of the present invention. Detailed Embodiments

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] An embodiment of the present invention provides a method for preparing an Fe / Nv-PCN piezoelectric material, and the method includes:

[0030] In-situ synthesis of PCN material: Calcining urea to obtain PCN material;

[0031] Synthesis of Nv-PCN material: Under a nitrogen atmosphere, calcining the PCN material to obtain Nv-PCN material;

[0032] Preparation of Fe / Nv-PCN composite material: Loading Fe3O4 nanoparticles onto the Nv-PCN material by in-situ co-precipitation method, cooling to room temperature after the reaction is completed, taking out, washing successively with deionized water and absolute ethanol, and then drying in a sealed manner to obtain Fe / Nv-PCN composite material, wherein the Fe3O4 nanoparticles are prepared using ferric chloride FeCl3·6H2O and ferrous sulfate FeSO4·7H2O as iron sources.

[0033] In the embodiment of the present invention, the specific steps of the method for preparing the Fe / Nv-PCN piezoelectric material include:

[0034] Step 1: In-situ synthesis of g-C3N4 (PCN) material: High-temperature calcining urea to obtain PCN material;

[0035] Step 2: Synthesis of Nv-PCN material: High-temperature calcining the PCN material obtained in Step 1 under a nitrogen atmosphere;

[0036] Step 3: Preparation of Fe3O4 nanoparticles: Preparing Fe3O4 nanoparticles using ferric chloride (FeCl3·6H2O) and ferrous sulfate (FeSO4·7H2O) as iron sources;

[0037] Step 4: Preparation of Fe / Nv-PCN composite material: Loading Fe3O4 nanoparticles onto Nv-PCN by in-situ co-precipitation method, cooling to room temperature after the reaction is completed, taking out, washing successively with deionized water and absolute ethanol, and then drying in a sealed manner.

[0038] In order to compare the effects of different piezoelectric materials, the present invention also gives the preparation method of Fe / PCN composite material: Loading Fe3O4 nanoparticles onto PCN by in-situ co-precipitation method, cooling to room temperature after the reaction is completed, taking out, washing successively with deionized water and absolute ethanol, and then drying in a sealed manner to obtain Fe / PCN composite material; the specific steps include:

[0039] Disperse 200 mg - 250 mg of PCN in 200 mL - 300 mL of ethanol / water (1:1) and sonicate for 2 h - 3 h. Then, dissolve FeSO4·7H2O and FeCl3·6H2O (molar ratio = 5:3 - 5:4) in 40 - 60 mL of deionized water and add it to the PCN ultrasonic suspension. Mechanically stir at 80 °C for 10 - 20 min, add an aqueous NaOH solution to adjust the solution pH to 11, continue to stir at 80 °C for 40 - 60 min to obtain a black mixture. After naturally cooling to room temperature, wash it several times with deionized water and ethanol alternately, and then dry it in an oven at 60 °C to finally obtain the solid product Fe / PCN composite material.

[0040] In this example, in step one, put 10 g - 20 g of urea into an alumina crucible with a lid, heat it in air at a rate of 2.5 - 10 °C / min to 550 °C, and keep it warm for 2 - 4 h. After the crucible cools to room temperature, collect the product, grind it into powder with a mortar, wash it several times with deionized water, and vacuum dry it at 80 °C for 12 h to obtain the PCN material.

[0041] In this example, in step two, it is synthesized by calcining PCN in a tube furnace under a nitrogen atmosphere. Grind 250 mg - 300 mg of PCN thoroughly and heat it to 550 °C at a heating rate of 5 °C / min in a nitrogen atmosphere, and keep it warm for 2 - 4 h (N2 flow rate is 100 mL / min). After cooling to room temperature, wash the obtained powder several times with deionized water and ethanol, and vacuum dry it at 80 °C for 12 h to obtain the Nv-PCN material.

[0042] In this example, in step four, using ferric chloride (FeCl3·6H2O) and ferrous sulfate (FeSO4·7H2O) as iron sources, the Fe / Nv-PCN composite material is synthesized with Nv-PCN by the in-situ coprecipitation method. The specific method is as follows: Disperse 200 mg - 250 mg of Nv-PCN in 200 mL - 300 mL of ethanol / water (1:1) and sonicate for 2 h - 3 h. Then, dissolve FeSO4·7H2O and FeCl3·6H2O (molar ratio = 5:3 - 5:4) in 40 - 60 mL of deionized water and add it to the Nv-PCN ultrasonic suspension. Mechanically stir at 80 °C for 10 - 20 min, add an aqueous NaOH solution to adjust the solution pH to 11, continue to stir at 80 °C for 40 - 60 min to obtain a black mixture. After naturally cooling to room temperature, wash it several times with deionized water and ethanol alternately, and then dry it in an oven at 60 °C to finally obtain the solid product Fe / Nv-PCN composite material.

[0043] Application of a Fe / Nv-PCN composite material in the degradation of organic pollutants.

[0044] Under the combined action of the piezoelectric effect of graphitic carbon nitride and the surface chemical reaction of nitrogen vacancies, the piezoelectric catalyst of the present invention introduces iron oxide to strengthen the piezoelectric effect of the material, breaks through the limitations of the band gap width and ROS yield of traditional piezoelectric materials, and exhibits excellent piezoelectric catalytic performance, which can significantly improve the efficiency of pollutant degradation. This material has high activity and good stability, can be effectively applied in the environmental field, and solves the deficiencies of existing environmental treatment technologies. At the same time, a preparation method of this material is provided. This method is simple, easy to operate, and low in cost, suitable for large-scale production. In addition, the specific application of this material in the environmental field is clarified, providing a new technical means for environmental treatment.

[0045] In order to verify the effect of the Fe / Nv-PCN composite material provided by the present invention, the following experimental process was used for analysis;

[0046] Preparation of different piezoelectric materials:

[0047] Example 1: Preparation of PCN material:

[0048] Put 10 g - 20 g of urea into an alumina crucible with a lid, heat it in air at a rate of 2.5 - 10 °C / min to 550 °C, and keep it warm for 2 - 4 h. After the crucible is cooled to room temperature, collect the product, grind it into powder with a mortar, wash it with deionized water multiple times, and vacuum dry it at 80 °C for 12 h to obtain the PCN material;

[0049] Example 2: Preparation of Nv-PCN material:

[0050] It was synthesized by calcining PCN in a tubular furnace under a nitrogen atmosphere. Grind 250 - 300 mg of PCN thoroughly, and heat it to 550 °C at a heating rate of 5 °C / min in a nitrogen atmosphere, and keep it warm for 2 - 4 h (N2 flow rate is 100 mL / min). After cooling to room temperature, wash the obtained powder with deionized water and ethanol several times, and vacuum dry it at 80 °C for 12 h to obtain the Nv-PCN material.

[0051] Example 3: Preparation of Fe / PCN material:

[0052] Using ferric chloride (FeCl3·6H2O) and ferrous sulfate (FeSO4·7H2O) as iron sources, it was synthesized with PCN by the in-situ co-precipitation method. The specific method is as follows: Disperse 200 - 250 mg of PCN in 200 - 300 mL of ethanol / water (1:1) and ultrasonically treat for 2 - 3 h. Then, dissolve FeSO4·7H2O and FeCl3·6H2O (molar ratio = 5:3 - 5:4) in 40 - 60 mL of deionized water and add it to the PCN ultrasonic suspension. Mechanically stir at 80 °C for 10 - 20 min, add an aqueous NaOH solution to adjust the solution pH to 11, continue to stir at 80 °C for 40 - 60 min to obtain a black mixture. After naturally cooling to room temperature, wash it several times alternately with deionized water and ethanol, and then place it in an oven at 60 °C for drying. Finally, obtain the solid product Fe / PCN material.

[0053] Example 4: Preparation of Fe / Nv-PCN composite material:

[0054] Using ferric chloride (FeCl3·6H2O) and ferrous sulfate (FeSO4·7H2O) as iron sources, it was synthesized with Nv-PCN by the in-situ co-precipitation method. The specific method is as follows: Disperse 200 - 250 mg of Nv-PCN material in 200 - 300 mL of ethanol / water (1:1) and ultrasonically treat for 2 - 3 h. Then, dissolve FeSO4·7H2O and FeCl3·6H2O (molar ratio = 5:3 - 5:4) in 40 - 60 mL of deionized water and add it to the Nv-PCN ultrasonic suspension. Mechanically stir at 80 °C for 10 - 20 min, add an aqueous NaOH solution to adjust the solution pH to 11, continue to stir at 80 °C for 40 - 60 min to obtain a black mixture. After naturally cooling to room temperature, wash it several times alternately with deionized water and ethanol, and then place it in an oven at 60 °C for drying. Finally, obtain the solid product Fe / Nv-PCN.

[0055] The results are as Figure 1 、 Figure 2 and Figure 3 shown, Figure 1X-ray diffraction patterns of the PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials prepared in Examples 1-4; the diffraction patterns of PCN and Nv-PCN contain a set of diffraction peaks, which are the g-C3N4 structure. The diffraction patterns of Fe / PCN and Fe / Nv-PCN contain two sets of diffraction peaks, which are the g-C3N4 structure and the Fe3O4 structure, respectively, indicating that a semiconductor composite material with Fe3O4 structure and g-C3N4 structure has been successfully prepared. The strong peak of PCN at 27.6° corresponds to the (002) diffraction plane of the layered conjugated aromatic structure, which is generated by the interlayer stacking of the conjugated aromatic system and is similar to the stacking between carbon atom layers in graphite. The weaker diffraction peak at 12.8° corresponds to the (100) diffraction plane of the heptazine unit in the repeating plane. This peak represents the periodic arrangement of triazine ring structural units in the plane and reflects the in-plane order of the material. After the nitrogen heat treatment of PCN, the two characteristic peaks in Nv-PCN significantly attenuate, indicating that nitrogen thermal etching produces g-C3N4 nitrogen vacancy defect structural units and weakened layered stacking. In addition, except for the characteristic diffraction peaks of g-C3N4, there are no additional hybrid peaks, indicating that the nitrogen heat treatment process has no effect on the lattice structure and phase purity of g-C3N4. For the Fe / PCN and Fe / Nv-PCN materials, the diffraction peaks of the Fe3O4 component are located at 2θ = 30.09°, 35.42°, 43.06°, 53.38°, 56.94°, 62.54°, and 73.93°, which are attributed to the (220), (311), (400), (422), (511), (440), and (533) crystal planes of Fe3O4, respectively. Due to the addition of Fe3O4, it may have a certain impact on the crystal structure of C3N4 containing nitrogen vacancies during the composite process, resulting in a change in its crystallinity, and the two characteristic peaks (002) and (100) attributed to PCN significantly attenuate. In addition, compared with the Fe / PCN material, due to the presence of nitrogen vacancies in the Fe / Nv-PCN material, Fe3O4 interacts with PCN, making the local structure of PCN more disordered, and then the intensity of the characteristic peaks of PCN is further weakened. From the XRD comparison data of PCN, Nv-PCN, Fe / PCN, Fe / Nv-PCN, and Fe3O4, it can be seen that the Fe / Nv-PCN catalytic material has been successfully synthesized, and after introducing nitrogen vacancies and Fe3O4 components into g-C3N4, there are no other impurities present and it has no impact on its crystal structure.

[0056] Figure 2 Fourier transform infrared spectra of the PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials prepared in Examples 1-4. In the range of 3000 - 3500 cm -1 and 1200 - 1700 cm -1and 813 cm -1 Three distinct peaks were detected in the ranges of 810 cm -1 The sharp absorption peak at is attributed to the out-of-plane bending vibration mode of the triazine ring unit, while the broad absorption band in the range of 3000 - 3600 cm -1 is related to the N-H stretching vibration in the terminal amino group and the O-H stretching vibration in H2O. In addition, the infrared peaks in the range of 1200 - 1700 cm -1 are caused by the stretching vibration of the C-N heterocycle. The stretching vibration peaks of the Nv-PCN sample are basically the same as those of the raw material PCN, indicating that after nitrogen heat treatment, the basic structure and chemical bonds of the sample are well retained. It is worth noting that the absorption peak intensity of the Nv-PCN sample in the range of 1200 - 1700 cm -1 significantly decreases, indicating that a large number of nitrogen defects are formed inside the PCN after nitrogen heat treatment. These nitrogen defects are expected to affect the piezocatalytic performance of the catalyst. Generally speaking, nitrogen defects can provide more active sites for the piezocatalytic degradation reaction, thus enhancing the mass transfer ability of the catalyst. The stretching vibration peaks of Fe-O belonging to Fe3O4 appear between 550 - 580 cm -1 in Fe3O4 nanoparticles and Fe / PCN, Fe / Nv-PCN composites. The N-H stretching vibration peak corresponding to that in PCN between 3000 - 3500 cm -1 and the characteristic peak caused by the skeletal vibration of the aromatic C-N heterocycle at 1200 - 1700 cm -1 can also be observed in the Fe / Nv-PCN spectrogram. In addition, the characteristic peak at 813 cm -1 is the stretching vibration peak of the triazine ring. The FT-IR test diagram further proves the successful synthesis of the Fe / Nv-PCN composite material.

[0057] Figure 3 Figure is the valence band X-ray photoelectron spectrogram of the PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezomaterials prepared in Examples 1 - 4. Their valence band tops (Ev) are 1.68 eV, 1.36 eV, 0.74 eV, and 0.58 eV respectively. Compared with PCN, the doping of Fe3O4 and the introduction of nitrogen vacancies increase the defect energy level and reduce the band gap, thus reducing the energy required for electrons to transition from the valence band (VB) to the conduction band (CB), improving the utilization rate of ultrasound, and being beneficial to the improvement of piezocatalytic performance.

[0058] Example 5. On the basis of Examples 1-4, according to the process of the piezoelectric catalysis activity test experiment, before the dark adsorption started, different catalysts were used for comparison: no catalyst, PCN, Nv-PCN, Fe / PCN, and Fe / Nv-PCN piezoelectric materials. Weigh 5-50 mg of the above piezoelectric catalytic material sample powder and add it to 10-50 mL of the water sample containing antibiotic pollutants. The best catalyst was selected. Samples were taken at regular intervals for ultraviolet spectrophotometer analysis. The experimental results are as Figure 7 shown. It can be seen that the Fe / Nv-PCN piezoelectric material prepared by the preparation method provided by the present invention has the fastest degradation rate and the highest degradation rate for the water sample containing antibiotic pollutants.

[0059] Example 6: On the basis of Examples 1-4, according to the process of the piezoelectric catalysis synthesis experiment, the effects of different raw materials on the synthesis of Fe / Nv-PCN piezoelectric materials were explored. By adding different raw materials, urea (Fe / Nv-PCN), melamine (Fe / Nv-MCN), thiourea (Fe / Nv-TCN), high-temperature calcination was carried out, and the piezoelectric catalysis reaction effect was detected. Samples were taken at regular intervals for ultraviolet spectrophotometer analysis.

[0060] As Figure 4 shown, the results show that Fe / Nv-PCN with urea as the raw material has the best effect on degrading tetracycline hydrochloride. Moreover, melamine (77 ¥ / 500g) > thiourea (50.5 ¥ / 500g) > urea (23 ¥ / 500g). Considering comprehensively, urea was selected as the raw material for synthesis.

[0061] Example 7: On the basis of Examples 1-4, according to the process of the piezoelectric catalysis synthesis experiment, the effects of different heating rates on the synthesis of Fe / Nv-PCN piezoelectric materials were explored. By controlling different heating rates: 2.5 °C / min, 5 °C / min, 10 °C / min, high-temperature calcination was carried out, and the piezoelectric catalysis reaction effect was detected. Samples were taken at regular intervals for ultraviolet spectrophotometer analysis.

[0062] Example 8: On the basis of Examples 1-4, according to the process of the piezoelectric catalysis synthesis experiment, the effects of different heat preservation times on the synthesis of Fe / Nv-PCN piezoelectric materials were explored. By controlling different heat preservation times: 2 h, 4 h, high-temperature calcination was carried out, and the piezoelectric catalysis reaction effect was detected. Samples were taken at regular intervals for ultraviolet spectrophotometer analysis.

[0063] Example 9: On the basis of Examples 1-4, in accordance with the experimental process of piezoelectric catalysis synthesis, the effects of different environmental states on the Fe / Nv-PCN piezoelectric material were explored. By adjusting different ultrasonic powers: 0-100 Hz, the piezoelectric catalytic reaction was excited by ultrasound for 5-60 min. After filtration, the concentration of the target pollutant antibiotic was measured.

[0064] The results are as Figure 5 and Figure 6 shown. The best heating rate is 2.5 °C / min, the holding time is 4 h, and the ultrasonic state has the best effect. The Fe / Nv-PCN piezoelectric material prepared under these conditions has the best effect.

[0065] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of Fe / Nv-PCN piezoelectric material, characterized in that, The method includes: In-situ synthesis of PCN material: Calcining urea to obtain the PCN material; Synthesis of Nv-PCN material: Under a nitrogen atmosphere, calcining the PCN material to obtain the Nv-PCN material; Preparation of Fe / Nv-PCN composite material: Loading Fe3O4 nanoparticles onto the Nv-PCN material by in-situ coprecipitation method. After the reaction is completed, cool to room temperature, take out, wash successively with deionized water and absolute ethanol, and then dry in a closed environment to obtain the Fe / Nv-PCN composite material, where the Fe3O4 nanoparticles are prepared using ferric chloride FeCl3·6H2O and ferrous sulfate FeSO4·7H2O as iron sources.

2. The preparation method of the Fe / Nv-PCN piezoelectric material according to claim 1, characterized in that, In the step of calcining urea to obtain the PCN material, during calcination, the heating rate is 2.5~10°C / min, heat up to 550°C, and keep the temperature for 2~4h.

3. The preparation method of the Fe / Nv-PCN piezoelectric material according to claim 2, characterized in that, After the heat preservation is completed, cool to room temperature, collect the product, grind the product into powder, wash it with deionized water multiple times. After the washing is completed, dry it in a vacuum environment at 80°C for 12h.

4. The preparation method of the Fe / Nv-PCN piezoelectric material according to claim 1, characterized in that, In the step of calcining the PCN material under a nitrogen atmosphere to obtain the Nv-PCN material, the PCN material is calcined in a tubular furnace. During calcination, keep the temperature for 2 - 4h, and the flow rate of nitrogen is 100ml / min.

5. The preparation method of the Fe / Nv-PCN piezoelectric material according to claim 4, characterized in that, After the calcination is completed, cool to room temperature, wash with deionized water and ethanol, and dry in a vacuum environment at 80°C for 12h to obtain the Nv-PCN material.

6. The preparation method of the Fe / Nv-PCN piezoelectric material according to claim 1, characterized in that, The steps for preparing the Fe / Nv-PCN composite material include: Disperse the Nv-PCN material in a mixed solution of ethanol and water, and perform ultrasonic treatment to obtain an ultrasonic suspension of the Nv-PCN material; Dissolve FeSO4·7H2O and FeCl3·6H2O in deionized water, and add it to the ultrasonic suspension of the Nv-PCN material; Stir at a temperature of 80°C for 10 - 20min, adjust the pH to 11, and continue stirring to obtain a black mixture; Cool naturally to room temperature, wash several times, and then dry in an oven to obtain the Fe / Nv-PCN composite material.

7. The preparation method of the Fe / Nv-PCN piezoelectric material according to claim 6, characterized in that, The volume ratio of ethanol to water is 1:1, and the molar ratio of FeSO4·7H2O to FeCl3·6H2O is 5:3~5:4.

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