Preparation and Application of a Piezoelectric Composite Material for Degrading Organic Pollutants in Water Using Low-Frequency Energy

Abstract

The present invention discloses the preparation and application of a piezoelectric composite material for degrading organic pollutants in water by using low-frequency energy. The piezoelectric composite material has ultra-high piezoelectric catalytic activity. This method overcomes the problem of secondary pollution easily caused by powder piezoelectric catalysts. Moreover, compared with the traditional piezoelectric effect triggering method, low-frequency energy is ubiquitous in life, which can greatly improve the efficiency of wastewater treatment. The present invention includes the modification of transition metal sulfides, dispersing the modified powder composite piezoelectric material in the piezoelectric polymer polyvinylidene fluoride, and finally mixing the composite piezoelectric material and the polymer matrix liquid to form various forms of ternary composite piezoelectric materials through phase conversion, so as to degrade organic pollutants in water under the action of low-frequency mechanical energies such as water flow, wind and vibration. The raw materials of the present invention are easy to obtain, the preparation method has a simple process, convenient operation, no secondary pollution, and high degradation efficiency, providing a feasible strategy for the efficient and environmentally friendly degradation of organic pollutants.

Description

Technical Field

[0001] The present invention provides an application of using low-frequency energy to degrade organic pollutants in water, relates to a preparation method of a ternary composite piezoelectric material, and particularly relates to its application in the fields of interfacial catalytic reaction and water purification, belonging to the technical field of preparation and application of new functional materials.

Background Art

[0002] The problem of water pollution is becoming increasingly severe, and problems such as the resulting environmental pollution and harm to human health need to be solved urgently. Therefore, water purification has become a focus issue widely concerned by researchers in recent years. In order to achieve the efficient degradation of pollutants in water, a series of new materials and new methods have been developed. Piezoelectrocatalysis is an emerging water treatment technology, which is a catalytic technology that relies on the charge energy or separation efficiency of carriers. The piezoelectric potential induced by strain or stress generates a huge electric field, thereby promoting the formation of active free radicals and achieving the efficient degradation of pollutants in water. Piezoelectrocatalysis effectively utilizes wind energy, solar energy, water wave energy, etc., and has the advantages of no chemical addition and darkroom operation, which has attracted the attention of researchers and has great application potential.

[0003] Traditional piezoelectric catalytic materials such as MoS2, WS2, MoSe2, WSe2, ZnO, BiTiO3, CdS, BaTiO3, etc. have all been proven to have piezoelectric activity and can be used to catalytically degrade pollutants in water. However, due to defects such as slow carrier migration rate and fast electron-hole recombination rate in these materials, their further application is limited. In recent years, researchers have paid more attention to modified composite piezoelectric catalytic materials.

[0004] CN113908827A discloses a tungsten oxide@bismuth tungstate heterojunction piezoelectric catalytic material, which reduces the resistance between phase interfaces and accelerates the carrier transport rate. By using the method of sulfuric acid etching, tungsten oxide is in-situ generated on the surface of bismuth tungstate, improving the stability and uniformity of the heterojunction piezoelectric catalytic material. CN114682281A discloses a BFO / BOC composite with piezoelectric catalytic characteristics, its preparation method and application. The composite has ferroelectricity and good piezoelectric catalytic performance, and can effectively catalytically degrade pollutants. CN113751025A discloses the preparation of a MnNb-(3)S-(6) piezoelectric catalyst, which can be used for the piezoelectric catalytic removal of neonicotinoid pesticides. In addition, the development of a piezoelectric electrocatalytic water treatment technology with low energy consumption and low pollution has also become a research hotspot.

[0005] Transition metal chalcogenide (TMDCs) two-dimensional layered materials have received a great deal of attention. Transition metal dichalcogenides (TMDs) are a class of layered materials, and their basic chemical formula can be written as MX2, where M represents transition metal elements, including Ti, V, Ta, Mo, W, Re, etc., and X represents chalcogen atoms such as S, Se, Te, etc. Such materials have wonderful electrical and optoelectronic properties and can be widely applied in the fields of energy conversion and collection as well as piezoelectric catalysis technology. For example, molybdenum disulfide has excellent piezoelectric properties due to its non-centrosymmetric lattice and is a new type of piezoelectric catalyst with good development potential. MoS2 has a layered structure and non-centrosymmetry. Under the action of low mechanical stress, it can undergo structural deformation, triggering a piezoelectric catalytic reaction to generate highly oxidative free radicals, which can oxidize and degrade organic pollutants in water. Introducing piezoelectrically active materials such as graphene, polyvinylidene fluoride, and graphitic carbon nitride into the composite with transition metal sulfide materials to obtain a composite material with dual piezoelectric properties. By virtue of the band gap difference and dual piezoelectric effect of the two materials, the separation of electrons / holes is promoted, and the piezoelectric catalytic performance of the material is enhanced. Polyvinylidene fluoride is a common piezoelectric catalytic material with good chemical stability, thermal stability, and mechanical stability, and has good application prospects.

[0006] In summary, aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an application for degrading organic pollutants in water using low-frequency energy. The main difference between the present invention and other technologies lies in that cuprous oxide is compounded with three different transition metal sulfides, MoS2, WS2, and CdS, to modify the transition metal sulfide, and then coupled with polyvinylidene fluoride to obtain a modified ternary composite piezoelectric material with high activity. The rapid degradation of pollutants in water can be achieved using the low-frequency energy in life. Compared with other technologies, the material synthesis process of this method is simple, the energy consumption in the water treatment process is smaller, and at the same time, the piezoelectric catalytic activity of the prepared modified ternary composite piezoelectric material is higher, making it easier to realize industrial application.

Summary of the Invention

[0007] [Technical Problems to be Solved]

[0008] The purpose of the present invention is to address the shortcomings of existing transition metal sulfide materials, such as low electron-hole separation rate, low catalytic activity, and high energy consumption, and propose an application for degrading organic pollutants in water using low-frequency energy. By coupling the non-toxic and easily obtainable semiconductor catalyst cuprous oxide, the excellent piezoelectric polymer polyvinylidene fluoride with transition metal sulfide, the piezoelectric catalytic activity of the material is significantly enhanced.

[0009] To achieve this purpose, for an application of degrading organic pollutants in water using low-frequency energy described in the present invention, its technical solution and steps are as follows:

[0010] [Technical Solution]

[0011] The present invention is realized through the following technical solutions.

[0012] (1) Preparation of composite piezoelectric material:

[0013] 1) Weigh copper salt and reducing agent according to the molar ratio of 2:1 - 1.5, place them in a 500 ml beaker, add 200 - 350 ml of deionized water, continuously stir for 30 - 60 min, add 2 mol / L sodium hydroxide solution to adjust the pH to 12 - 13 to obtain a homogeneous solution;

[0014] 2) Weigh 0.6 g of transition metal sulfide, place it in the solution obtained in 1) and stir for 1 - 2 h to obtain a composite material precursor solution;

[0015] 3) Place the precursor solution obtained in step 2) in a water bath and heat and stir at 60 - 70 °C for 5 - 8 h;

[0016] 4) Wash the reacted material with water and absolute ethanol 2 - 3 times, and filter to obtain a powdery composite material;

[0017] 5) Place the powdery composite material obtained in step 4) in a tube furnace, under N2 atmosphere, activate at 300 - 450 °C for 3 - 5 h;

[0018] (2) Preparation of ternary piezoelectric polymer material

[0019] Dissolve polyvinylidene fluoride powder in an organic solvent, disperse it under ultrasonic conditions for 80 - 120 min, place it in a water bath, stir at 60 °C for 30 - 50 min to obtain a homogeneous polymer base liquid. Weigh the composite piezoelectric material obtained in step (1), add it to the above polymer base liquid, place it in a water bath, stir at 70 °C for 50 min, and then quickly transfer it to a vacuum drying oven with a pressure of -1.1 - -1.5 MPa and a temperature of 50 °C for degassing for 24 - 48 hours to obtain a piezoelectric polymer base liquid. Take 10 - 25 ml of the above base liquid, spray deionized water, and prepare various forms of ternary piezoelectric polymer materials by the phase inversion method;

[0020] (3) Application of using low - frequency energy to degrade organic pollutants in water

[0021] Take 1 - 50 L of organic wastewater, make the ternary piezoelectric polymer material prepared in (2) fully contact with the wastewater, use low - frequency energy to trigger the piezoelectric effect to degrade organic pollutants in water, take 3 - 5 mL of the reaction solution, and measure the concentration of organic pollutants.

[0022] The copper salt can be one or a mixture of two or more of anhydrous copper sulfate, copper nitrate trihydrate, copper acetate, and copper chloride.

[0023] The reducing agent can be one or more of hydrazine hydrate, glucose, sodium citrate, and sodium sulfite.

[0024] The transition metal sulfide is one or more of molybdenum disulfide, cadmium sulfide, and tungsten disulfide.

[0025] The mass ratio of the composite piezoelectric material to the piezoelectric polymer-based liquid is 1:15 to 50.

[0026] The ternary piezoelectric polymer material can be in the form of a liner, a film, or microspheres.

[0027] The low-frequency energy is low-frequency mechanical energy such as water wave energy, wind energy, and vibration.

[0028] [Beneficial effects]

[0029] Compared with the prior art, the present invention mainly has the following beneficial effects:

[0030] (1) The preparation method of the modified ternary composite piezoelectric material provided by the present invention is simple, low in cost, and large in output, and can be used in actual production.

[0031] (2) The modified ternary composite piezoelectric material of the present invention has ultra-high piezoelectric catalytic activity, can rapidly degrade organic pollutants in water, has high reusability, and no secondary pollution, meeting the requirements of environmental engineering applications.

Description of the drawings

[0032] Figure 1 It is a scanning electron microscope photograph of the inner surface of the Cu2O@MoS2 / PVDF piezoelectric liner prepared by the present invention.

[0033] Figure 2 It is the effect curve of the Cu2O@MoS2 / PVDF piezoelectric catalytic degradation of pollutants prepared by the present invention.

[0034] Figure 3 It is a scanning electron microscope photograph of the surface of the Cu2O@WS2 / PVDF piezoelectric film prepared by the present invention.

[0035] Figure 4 It is the effect curve of the Cu2O@WS2 / PVDF piezoelectric catalytic degradation of pollutants prepared by the present invention.

[0036] Figure 5 It is a scanning electron microscope photograph of the surface of the Cu2O@CdS / PVDF piezoelectric microspheres prepared by the present invention.

[0037] Figure 6 It is the effect curve of the Cu2O@CdS / PVDF piezoelectric catalytic degradation of pollutants prepared by the present invention.

Specific implementation manners

[0038] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following is a detailed description in conjunction with the attached drawings and embodiments.

[0039] Example 1:

[0040] Preparation and application of Cu2O@MoS2 / PVDF composite piezoelectric liner tubes, and the specific preparation and application methods are as follows.

[0041] (1) Preparation of composite piezoelectric materials:

[0042] 1) Weigh anhydrous copper sulfate and glucose in a molar ratio of 2:1, place them in a 500 ml beaker, add 200 ml of deionized water and continuously stir for 40 min, add 2 mol / L sodium hydroxide solution to adjust the pH to 12 to obtain a uniform solution;

[0043] 2) Weigh 0.6 g of molybdenum disulfide, place it in the solution of step 1) and stir for 1.5 hours to obtain a composite material precursor solution;

[0044] 3) Place the precursor solution obtained in step 2) in a water bath at 60 °C, heat and stir for 6 h;

[0045] 4) Wash the reacted material with water and absolute ethanol 2 - 3 times, and filter to obtain a powdery composite material;

[0046] 5) Place the powdery composite material obtained in step 4) in a tubular furnace, and under a N2 atmosphere, activate it at a high temperature of 350 °C for 3 h;

[0047] (2) Preparation of ternary piezoelectric polymer materials

[0048] Dissolve 6 g of polyvinylidene fluoride in 48 g of organic solvent, disperse it under ultrasonic conditions for 120 min, place it in a water bath pot, and stir at 60 °C for 50 min to obtain a uniform polymer base liquid. Weigh 0.2 g of the composite piezoelectric catalyst in step (1), add it to 4 g of the above polymer base liquid, place it in a water bath pot, stir at 70 °C for 50 min, and then quickly transfer it to a vacuum drying oven with a pressure of -1.1 MPa and a temperature of 50 °C for degassing for 24 h to obtain an organic piezoelectric polymer base liquid. Take 25 ml of the above base liquid, spray deionized water, and prepare ternary piezoelectric polymer liner tubes by the phase inversion method;

[0049] (3) Application of degrading organic pollutants in water using low-frequency energy

[0050] Take 50 L of organic wastewater, continuously flow it through the ternary piezoelectric polymer liner tube prepared in (2), use the water wave energy to trigger the piezoelectric effect to degrade the organic pollutants in the water, take 3 - 5 mL of the effluent, and measure the concentration of the organic pollutants. The test results are as shown in the appendix Figure 2As shown, the results show that the Cu2O@MoS2 / PVDF piezoelectric tube of the present invention has obvious degradation effects on pollutants such as oxytetracycline, ciprofloxacin, rhodamine B, bisphenol A, and methylene blue under water flow drive, and can be applied to the advanced treatment of organic wastewater and other fields. It can be seen that the present invention has a wide range of applications in the field of water treatment.

[0051] Example 2:

[0052] Preparation and application of Cu2O@WS2 / PVDF composite piezoelectric thin film. The specific preparation and application methods are as follows.

[0053] (1) Preparation of composite piezoelectric material:

[0054] 1) Weigh copper chloride and sodium citrate according to a molar ratio of 2:1.2, place them in a 500 ml beaker, add 250 ml of deionized water, stir continuously for 50 min, add 2 mol / L sodium hydroxide solution to adjust the pH to 12.5 to obtain a uniform solution;

[0055] 2) Weigh 0.6 g of WS2, place it in the solution obtained in 1) and stir for 1 h to obtain a composite material precursor solution;

[0056] 3) Place the precursor solution obtained in step 2) in a water bath at 65 °C, heat and stir for 7 h;

[0057] 4) Wash the reacted material with water and absolute ethanol 2 - 3 times, and filter to obtain a composite material precursor;

[0058] 5) Place the composite piezoelectric catalyst obtained in step 4) in a tubular furnace, under N2 atmosphere, activate at 400 °C for 4 h;

[0059] (2) Preparation of ternary piezoelectric polymer material

[0060] Dissolve 4 g of polyvinylidene fluoride in 20 g of organic solvent, disperse it under ultrasonic conditions for 100 min, place it in a water bath, stir at 60 °C for 40 min to obtain a uniform polymer base liquid. Weigh 0.15 g of the composite piezoelectric material from step (1), add it to the above polymer base liquid, place it in a water bath, stir at 70 °C for 50 min, and then quickly transfer it to a vacuum drying oven with a pressure of -1.2 MPa and a temperature of 50 °C for degassing for 36 h to obtain a piezoelectric polymer base liquid. Take 15 ml of the above base liquid and spray deionized water to prepare a ternary piezoelectric polymer material thin film by the phase inversion method;

[0061] (3) Application of using low - frequency energy to degrade organic pollutants in water

[0062] Take 20 L of organic wastewater, immerse the ternary piezoelectric polymer film prepared in (2) in the wastewater and vibrate it to trigger the piezoelectric effect and degrade the organic pollutants in the water. Take 3 - 5 mL of the reaction solution and measure the concentration of the organic pollutants. The test results are as follows Figure 4 As shown, it can be seen from the results that the Cu2O@WS2 / PVDF piezoelectric film of the present invention has a relatively obvious degradation effect on pollutants such as tetracycline, norfloxacin, ronidazole, chlortetracycline, and methyl orange under mechanical vibration, and can be applied to the advanced treatment of fields such as organic wastewater. It can be seen that the present invention has a wide application range in the field of water treatment.

[0063] Example 3:

[0064] Preparation and application of Cu2O@CdS / PVDF composite piezoelectric microspheres. The specific preparation and application methods are as follows.

[0065] (1) Preparation of the composite piezoelectric catalyst:

[0066] 1) Weigh copper nitrate trihydrate and hydrazine hydrate according to a molar ratio of 2:1.5, place them in a 500 ml beaker, add 300 ml of deionized water and continuously stir for 60 min. Add 2 mol / L sodium hydroxide solution to adjust the pH to 12 to obtain a homogeneous solution;

[0067] 2) Weigh 0.6 g of CdS and place it in the solution obtained in 1) and stir for 2 h to obtain a composite material precursor solution;

[0068] 3) Place the precursor solution obtained in step 2) in a water bath at 70 °C and heat and stir for 8 h;

[0069] 4) Wash the reacted material with water and absolute ethanol 2 - 3 times and filter to obtain a composite material precursor;

[0070] 5) Place the composite piezoelectric material obtained in step 4) in a tube furnace and activate it at a high temperature of 450 °C for 5 h under a N2 atmosphere;

[0071] (2) Preparation of the ternary piezoelectric polymer material

[0072] Dissolve 3 g of polyvinylidene fluoride in 15 g of an organic solvent, disperse it under ultrasonic conditions for 90 min, place it in a water bath pot, and stir at 60 °C for 45 min to obtain a homogeneous polymer base solution. Weigh 0.1 g of the composite piezoelectric material obtained in step (1) and add it to the above polymer base solution. Place it in a water bath pot and stir at 70 °C for 50 min, then quickly transfer it to a vacuum drying oven with a pressure of -1.5 MPa and a temperature of 50 °C to degas for 48 h to obtain a piezoelectric polymer base solution. Take 10 ml of the above base solution and spray deionized water to prepare ternary piezoelectric polymer microspheres by the phase inversion method;

[0073] (3) Application of Degrading Organic Pollutants in Water by Low-Frequency Energy

[0074] Take 30 L of organic wastewater, mix it with the ternary piezoelectric polymer microspheres prepared in (2) in a reactor, ventilate the bottom of the reactor, trigger the piezoelectric effect by wind energy to degrade organic pollutants in water, take 3-5 mL of the reaction solution, and measure the concentration of organic pollutants. The test results are as follows Figure 6 As shown, it can be seen from the results that the Cu2O@CdS / PVDF piezoelectric microspheres of the present invention have obvious degradation effects on pollutants such as levofloxacin, ciprofloxacin, lomefloxacin, fleroxacin, and sparfloxacin under the action of wind mechanical energy, and can be applied to the advanced treatment of fields such as organic wastewater. It can be seen that the present invention has a wide application range in the field of water treatment.

Claims

1. A preparation method of a ternary piezoelectric polymer material, characterized in that It includes the following steps: 1) Weigh copper salt and reducing agent according to the molar ratio of 2:1 - 1.5, place them in a 500 mL beaker, add 200 - 350 mL of deionized water and continuously stir for 30 - 60 min. Then add 2 mol / L sodium hydroxide solution to adjust the pH to 12 - 13 to obtain a homogeneous solution; 2) Weigh 0.6 g of transition metal sulfide and place it in the solution obtained in 1) and stir for 1 - 2 h to obtain a composite material precursor solution. The transition metal sulfide is one or more of molybdenum disulfide, cadmium sulfide and tungsten disulfide; 3) Place the precursor solution obtained in step 2) in a water bath and heat and stir at 60 - 70 °C for 5 - 8 h; 4) Wash the reacted material with water and absolute ethanol 2 - 3 times, and filter to obtain a powdery composite material; 5) Place the powdery composite material obtained in step 4) in a tube furnace, and under the N2 atmosphere, activate it at a high temperature of 300 - 450 °C for 3 - 5 hours to prepare a composite piezoelectric material; 6) Dissolve polyvinylidene fluoride powder in an organic solvent, disperse it under ultrasonic conditions for 80 - 120 min, place it in a water bath pot, stir at 60 °C for 30 - 50 min to obtain a homogeneous polymer-based liquid. Weigh the composite piezoelectric material obtained in step 5), add it to the above polymer-based liquid, place it in a water bath pot, stir at 70 °C for 50 min, and then quickly transfer it to a vacuum drying oven with a pressure of -1.1 - -1.5 MPa and a temperature of 50 °C for degassing for 24 - 48 hours to obtain a piezoelectric polymer-based liquid. Take 10 - 25 mL of the above liquid and spray deionized water to prepare various forms of ternary piezoelectric polymer materials by the phase inversion method.

2. The preparation method of the ternary piezoelectric polymer material according to claim 1, wherein, The copper salt is one or a mixture of two or more of anhydrous copper sulfate, copper nitrate trihydrate, copper acetate and copper chloride; the reducing agent is one or a mixture of two or more of hydrazine hydrate, glucose, sodium citrate and sodium sulfite.

3. The preparation method of the ternary piezoelectric polymer material according to claim 1, characterized in that, The mass ratio of polyvinylidene fluoride to the organic solvent is 1:3 - 10, and the mass ratio of the composite piezoelectric material to the piezoelectric polymer-based liquid is 1:15 - 50.

4. The preparation method of the ternary piezoelectric polymer material according to claim 1, characterized in that, The form of the ternary piezoelectric polymer material is a liner, a film or a microsphere.

5. Use of a ternary piezoelectric polymer material obtained by the preparation method according to claim 1 in the degradation of organic pollutants in water using low-frequency energy, characterized in that, Take 1 - 50 L of organic wastewater, make the prepared ternary piezoelectric polymer material fully contact with the wastewater, use low-frequency energy to trigger the piezoelectric effect to degrade organic pollutants in the water, take 3 - 5 mL of the reaction solution and measure the concentration of organic pollutants.

6. The application of using low-frequency energy to degrade organic pollutants in water according to claim 5, characterized in that, The low-frequency energy is water wave energy, wind energy, vibration mechanical energy.

Images