Method for using piezoelectric material to screen soil and degrade pollutants

Abstract

The present invention relates to the technical field of slag treatment, and in particular to a method for using piezoelectric materials for slag screening and pollutant degradation. The method comprises the following steps: S1. piezoelectric material selection; S2. coating preparation; S3. screen structure design; S4. screen installation and adjustment; S5. piezoelectric material coating; S6. vibrating screen implementing excitation force; S7. high-pressure spray device assistance; S8. dehydration and drying treatment of dewatering screen. The present invention can combine vibration screening and oxidation decontamination to improve the processing efficiency; the present invention utilizes the piezoelectric principle to degrade and oxidize organic matter and microorganisms in waste slag, so that the whole process does not require the addition of additional chemical oxidants, greatly reducing the amount of addition.

Description

Technical Field

[0001] The invention relates to the technical field of slag treatment, and in particular to a method for using a piezoelectric material to screen slag and degrade pollutants. Background Art

[0002] In the construction of engineering projects in large cities, billions of cubic meters of construction waste are produced every year. The traditional treatment method is generally to dehydrate and dry them and then transport them for stacking and landfill. The composition of construction waste is complex, containing heavy metals, dissolved salts, benzene and hydrocarbon organic matter to varying degrees. Directly stacking the waste in the waste yard also poses a great risk, which can easily lead to environmental pollution and have long-term and irreparable impacts on the environment. Among them, shield waste is produced in a volume of hundreds of millions of cubic meters per year. The addition of a large amount of foaming agent, bentonite, modifier and water makes the waste mud high in water content and poor in mechanical properties, making it difficult to dispose of. Common organic pollutants in earth pressure shield waste include polycyclic aromatic hydrocarbons (PAHs), benzene series, petroleum hydrocarbons, etc. These pollutants may come from oil pollution, lubricant leakage or natural organic matter in the stratum during construction.

[0003] As an advanced technology that can effectively remove organic pollutants, piezoelectric catalytic technology can fully convert the vibration energy of nature into chemical energy compared with traditional catalytic technology. It has low energy consumption and is pollution-free. The active species generated during the catalytic process can effectively decompose pollutants. In the existing patented technology, there is an application of a composite piezoelectric catalytic material in sludge dewatering (CN111068659B). The composite piezoelectric catalytic material loads an electrocatalyst and uses the residual piezoelectric field of the piezoelectric material to induce the electrocatalyst to generate an induced electric field, thereby increasing the dewatering amount of the sludge; when the composite piezoelectric catalytic material is used together with a catalyst promoter, a coagulant and a flocculant, and then assisted by ultrasonic treatment, after filtering by a filter press, the dewatering amount of the sludge can be increased and the quality of the sludge can be reduced.

[0004] However, the above-mentioned slag treatment method has the following technical problems:

[0005] ① The traditional treatment method of waste soil does not treat pollutants. Under the influence of overburden pressure and rainfall infiltration, the leachate produced easily penetrates into the surrounding soil, causing groundwater pollution and soil pollution;

[0006] ② The existing patented technology promotes the oxidation and rupture of the cell membrane of sludge microorganisms through the piezoelectric effect, thereby improving the efficiency of sludge dehydration and reduction, without further removing organic pollutants in the soil;

[0007] ③ Each treatment method is isolated and has a single effect. If multiple methods are directly combined, the process will be complicated, and the processing time, difficulty and cost will increase. Summary of the invention

[0008] The present invention provides a method for using piezoelectric materials to screen and degrade pollutants from slag, aiming to solve the technical problems existing in existing slag treatment methods.

[0009] The present invention provides a method for using piezoelectric materials to screen soil and degrade pollutants, comprising the following steps:

[0010] S1. Selection of piezoelectric materials: Select appropriate piezoelectric materials as raw materials for coating preparation;

[0011] S2. Coating preparation: 62-68% of piezoelectric material, 19-24% of polyvinyl acrylate, 6-8% of silicon carbide, and 5-8% of carbon nanotubes are mixed by ultrasonic to prepare a piezoelectric material coating;

[0012] S3. Screen structure design: According to the size of the soil particles, select a screen with a smaller hole diameter than the soil particles;

[0013] S4. Screen installation and adjustment: Assemble the screen frame into a multi-layer screen structure and adjust the spacing between the multi-layer screens;

[0014] S5. Piezoelectric material coating: The prepared piezoelectric material coating is evenly coated on the surface of the multi-layer screen;

[0015] S6. Vibrating screen implements excitation force: through the excitation force of the vibrating screen, the piezoelectric material coated on the screen is excited to generate intrinsic free carriers in the piezoelectric material;

[0016] S7. High-pressure spray device assistance: During the slag screening process, the screen is sprayed with high pressure to further stimulate the piezoelectric material to generate intrinsic free carriers;

[0017] S8. Dehydration and drying treatment of dewatering screen: install the screen coated with piezoelectric material in the dewatering screen, start the dewatering screen equipment, and dehydrate and dry the slag treated by the vibrating screen. The piezoelectric material generates intrinsic free carriers under the action of vibration, which degrades the organic pollutants in the slag.

[0018] As a further improvement of the present invention, in step S1, the selected piezoelectric materials include BaTiO3, MoS2, ZnO, Ag / BaTiO3, and HPVDF / BTO-OV.

[0019] As a further improvement of the present invention, in step S2, the coating preparation process includes:

[0020] S21. Prepare a solution: dissolve a required amount of polyvinyl acrylate in deionized water or ethanol, and stir until completely dissolved to form a uniform polyvinyl acrylate solution;

[0021] S22. Dispersing carbon nanotubes: adding a desired amount of carbon nanotubes to a polyvinyl acrylate solution, and ultrasonically treating the mixture using an ultrasonic processor to uniformly disperse the carbon nanotubes in the solution;

[0022] S23. Adding silicon carbide: adding a desired amount of silicon carbide particles to the polyvinyl acrylate solution containing carbon nanotubes, and stirring thoroughly until the silicon carbide is evenly dispersed in the solution;

[0023] S24. Adding a piezoelectric material: gradually adding a desired amount of a piezoelectric material to the polyvinyl acrylate solution containing carbon nanotubes, stirring thoroughly until the piezoelectric material is evenly dispersed in the solution;

[0024] S25. Ultrasonic treatment: placing the mixture into an ultrasonic processor again for further ultrasonic treatment to uniformly disperse and bond the piezoelectric material, polyvinyl acrylate, and carbon nanotubes;

[0025] S26. Adjust viscosity: slowly add deionized water while stirring until the coating reaches the desired viscosity;

[0026] S27. Degassing: The prepared coating mixture is allowed to stand, or a vacuum degassing device is used to remove bubbles generated during the mixing process;

[0027] S28. Storage and Use: Store the prepared paint in a sealed container to avoid contact with light and air; stir slightly before use to ensure the uniformity of the paint.

[0028] As a further improvement of the present invention, during the ultrasonic treatment in steps S22 and S25, the ultrasonic processor adopts an intermittent treatment method, heating for a period of time until the solution reaches a specified dissolution temperature, stopping heating, and continuing heating when the solution temperature is lower than the specified dissolution temperature, and repeating this operation until the ultrasonic treatment is completed.

[0029] As a further improvement of the present invention, in the step S3, when designing the screen structure, it also includes preparing piezoelectric material slow-release spheres to be sandwiched between the multiple layers of screens;

[0030] The preparation process of piezoelectric material sustained-release spheres includes:

[0031] S31. Prepare a solution: dissolve a desired amount of polyvinyl acrylate in ethanol and stir until completely dissolved to form a uniform polyvinyl acrylate solution;

[0032] S32. Dispersing carbon nanotubes: adding a desired amount of carbon nanotubes to a polyvinyl acrylate solution, and ultrasonically treating the mixture using an ultrasonic processor to uniformly disperse the carbon nanotubes in the solution;

[0033] S33 adding silicon carbide: adding a desired amount of silicon carbide particles to the polyvinyl acrylate solution containing carbon nanotubes, stirring thoroughly until the silicon carbide is evenly dispersed in the solution to form a mixed solution of a reinforcing material;

[0034] S34. Adding a piezoelectric material: gradually adding a desired amount of a piezoelectric material to the polyvinyl acrylate solution containing carbon nanotubes, stirring thoroughly until the piezoelectric material is evenly dispersed in the solution;

[0035] S35. Ultrasonic treatment: placing the mixture into an ultrasonic processor again for further ultrasonic treatment to uniformly disperse and bond the piezoelectric material, polyvinyl acrylate, and carbon nanotubes;

[0036] S36 spray drying: spray drying the prepared mixed solution of the piezoelectric material and the reinforcing material to form spherical particles, and controlling the size and shape of the particles;

[0037] S37. Screening: Screening the particles obtained by spray drying to obtain a spherical piezoelectric material with uniform particle size;

[0038] S38. Coupling agent treatment: Place the screened spherical piezoelectric material in a solution containing a silane coupling agent, stir it, and dry it for later use.

[0039] As a further improvement of the present invention, in step S3, the sieve hole diameter is selected as follows: when screening slag with large diameter particles, the sieve hole diameters are 20 mm, 10 mm, and 5 mm respectively; when used in a vibrating screen dehydration device, the sieve hole diameter is in the range of 20 to 120 μm.

[0040] As a further improvement of the present invention, in step S4, the screen installation and adjustment specifically includes:

[0041] S41. Prepare the screen frame: Make sure the screen frame is clean and free of residue and dirt;

[0042] S42. Install the lower screen: Place the lower screen with a larger aperture on the bottom of the screen frame, align the edge of the screen frame, and fix the top corners and edges of the lower screen;

[0043] S43. Install the upper screen: Place the upper screen with a smaller aperture on the lower screen, align the edge of the screen frame, and fix the top corners and edges of the upper screen;

[0044] S44. Spacing adjustment: adjust the spacing between the upper screen and the lower screen and fix it;

[0045] S45. Fixing of vibration screen dehydration equipment: Install the screen frame with the screen onto the vibration screen equipment and fix it.

[0046] As a further improvement of the present invention, in step S5, the process of coating the piezoelectric material specifically includes:

[0047] S51. Substrate preparation: Clean the metal substrate surface of the screen to remove all grease, dust and contaminants;

[0048] S52. Paint preparation: Use a stirrer to gently stir until the paint is uniform;

[0049] S53. Coating: coating the coating evenly on the metal substrate surface of the screen; when multiple layers of coating are applied, the next layer of coating is applied after each layer of coating is dried;

[0050] S54. Drying: After coating is completed, the coating is placed in a dry environment for solvent casting drying.

[0051] As a further improvement of the present invention, in step S6, the process of exciting the piezoelectric material coated on the screen by the excitation force of the vibrating screen to make the piezoelectric material generate intrinsic free carriers includes:

[0052] S61. Installation and preparation of the vibrating screen: The screen coated with the piezoelectric material is installed in the vibrating screen device and fixed firmly;

[0053] S62. Vibrating screen start: start the vibrating screen equipment, start to generate mechanical vibration, and transmit the vibration to the piezoelectric material coated on the screen through the screen;

[0054] S63. Mechanical stress transfer: The periodic deformation of the internal lattice of the piezoelectric material under the mechanical stress generated by the vibrating screen;

[0055] S64. Electric field generation: Piezoelectric materials generate internal electric fields and separate electrons and holes to form free carriers;

[0056] S65. Free carrier generation: The electrons in the piezoelectric material are excited to the conduction band to form electron-hole pairs. The electrons and holes move inside the material to form intrinsic free carriers.

[0057] S66. Free carrier migration: Free carriers migrate to the surface of the material under the action of an electric field;

[0058] S67. Generation of reactive oxygen free radicals: Free carriers react with oxygen molecules in the air to generate reactive oxygen free radicals;

[0059] S68.Continuous reaction: The vibrating screen works continuously, maintaining mechanical vibration, so that the piezoelectric material continues to generate free carriers and active oxygen free radicals.

[0060] As a further improvement of the present invention, in step S7, during the slag screening process, the process of spraying the screen with high pressure to further excite the piezoelectric material to generate intrinsic free carriers includes:

[0061] S71. Installation and preparation of high-pressure spray device: Install the high-pressure spray device above or on the side of the vibrating screen so that the spray water flow can evenly cover the screen coated with piezoelectric material;

[0062] S72. Start the vibrating screen and high-pressure spray device: Start the vibrating screen equipment and generate mechanical vibration, and start the high-pressure spray device to spray high-pressure water onto the screen coated with piezoelectric material to apply additional mechanical force to the piezoelectric material;

[0063] S73. Enhanced generation of free carriers: Under the combined effects of the vibration of the vibrating screen and the high-pressure spray water flow, the piezoelectric material generates more free carriers, and the free carriers migrate to the surface of the piezoelectric material.

[0064] As a further improvement of the present invention, in step S8, the process of dehydration and drying by the dehydration screen includes:

[0065] S81. The active oxygen free radicals generated by the piezoelectric material come into contact with the organic pollutants in the slag, and an oxidation reaction occurs, decomposing the organic pollutants into harmless small molecules;

[0066] S82. The vibrating screen and high-pressure spray device work continuously to generate new active oxygen free radicals to react with organic pollutants and continuously degrade organic pollutants; the dewatering screen dehydrates and dries the slag treated by the vibrating screen.

[0067] The beneficial effects of the present invention are:

[0068] ① Vibration screening and oxidation decontamination can be combined to improve treatment efficiency;

[0069] ② Using the piezoelectric principle to degrade and oxidize organic matter and microorganisms in waste soil, the entire process does not require the addition of additional chemical oxidants, greatly reducing the amount of addition;

[0070] ③Multi-layer screens can reduce the wear of piezoelectric materials and generate a large number of active oxygen free radicals to degrade organic pollutants;

[0071] ④This method can work quickly and continuously and is easy to operate;

[0072] ⑤ The organic pollution content of the slag treated by this method is low and has greater value for resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a schematic diagram of treating slag with a screen coated with a piezoelectric material coating in the method of the present invention. DETAILED DESCRIPTION

[0074] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0075] The present invention provides a method for using piezoelectric materials for slag screening and pollutant degradation, which is mainly used in the treatment of waste slag in construction projects, especially for slag with high organic matter content. The piezoelectric material is excited by the excitation force of the vibrating screen, and its intrinsic free carriers are driven to generate active oxygen free radicals to degrade organic pollutants.

[0076] Specifically, Figure 1 As shown, the method comprises the following steps:

[0077] S1. Selection of piezoelectric materials: Select appropriate piezoelectric materials as raw materials for coating preparation, such as BaTiO3, MoS2, ZnO, Ag / BaTiO3, HPVDF / BTO-OV, etc. Among them, Ag / BaTiO3 and HPVDF / BTO-OV are composite piezoelectric materials.

[0078] S2. Preparation of coating 1: 62~68% piezoelectric material, 19~24% polyvinyl acrylate (PVEA), 6~8% silicon carbide (SiC), and 5~8% carbon nanotubes (CNT) can be mixed by ultrasonic to make a coating. The prepared piezoelectric material coating is applied in the form of a low-cost coating. Coating 1 needs to be flexible and dried by a solvent casting method so that it adheres firmly to the metal surface. The preparation process is as follows:

[0079] a) Prepare the solution: Dissolve the required amount of PVEA in deionized water or ethanol and stir until it is completely dissolved to form a uniform PVEA solution. It can be heated appropriately (about 60°C) to accelerate the dissolution process.

[0080] b) Dispersing carbon nanotubes (CNT): Add the required amount of CNT to the PVEA solution and use an ultrasonic processor to ultrasonicate the mixture for about 30 minutes to ensure that the CNT is evenly dispersed in the solution. During ultrasonication, be careful to prevent overheating and perform intermittent treatment, such as 5 minutes of treatment and 2 minutes of rest.

[0081] c) Adding silicon carbide (SiC): Add the required amount of SiC particles to the PVEA solution containing CNTs, and stir thoroughly with a stirrer or a magnetic stirrer until the SiC is evenly dispersed in the solution; the silicon carbide particles are micron-sized particles (1µm~10µm).

[0082] d) Adding piezoelectric material: gradually add the required amount of piezoelectric material to the PVEA solution containing CNTs, and stir thoroughly using a stirrer or a magnetic stirrer until the piezoelectric material is evenly dispersed in the solution.

[0083] e) Ultrasonic treatment: The above mixture is placed in an ultrasonic processor again for further ultrasonic treatment for about 30 minutes. This step helps to improve the uniform dispersion and mutual bonding of piezoelectric materials, PVEA and CNT.

[0084] f) Adjust viscosity: Deionized water can be added as needed to adjust the viscosity of the coating. Slowly add deionized water while stirring until the coating reaches the desired viscosity.

[0085] g) Degassing: Allow the prepared coating mixture to stand or use a vacuum degassing device to remove air bubbles generated during the mixing process.

[0086] h) Storage and use: Store the prepared coating in a sealed container to avoid exposure to light and air. Stir slightly before use to ensure the uniformity of the coating.

[0087] i) When using an ultrasonic processor, be careful to prevent the liquid from overheating and adopt an intermittent treatment method.

[0088] j) Once the paint is prepared, use it as soon as possible to prevent separation or sedimentation of the components during storage.

[0089] S3. Sieve 2 structure design: According to the size of the slag particles 4, select a sieve 2 with a sieve hole diameter smaller than the slag particles 4; the multi-layer sieve 2 is made of steel, and its hole diameter is set according to different needs. For slag with large diameter particles, the recommended sieve hole diameters are 20mm, 10mm, and 5mm respectively; when used in a vibrating screen dehydration device, the recommended sieve hole diameter is in the range of 20~120μm.

[0090] When designing the structure of the screen 2, it also includes preparing piezoelectric material slow-release spheres 3 to be sandwiched between the multiple layers of screens 2. The piezoelectric material slow-release spheres 3 can be selected and used according to needs. When used, the diameter of the sphere is about 3 mm larger than the aperture of the screen 2. The two layers of screens 2 on the same frame clamp and fix the slow-release spheres 3, and 4 to 8 spheres can be fixed according to needs.

[0091] The preparation process of the piezoelectric material sustained-release sphere 3 includes:

[0092] a) Prepare the solution: Dissolve the required amount of polyvinyl acrylate (25-30%) in ethanol and stir until completely dissolved to form a uniform polyvinyl acrylate solution.

[0093] b) Dispersing carbon nanotubes: Add the required amount of carbon nanotubes (3-5%) into the polyvinyl acrylate solution and ultrasonicate the mixture using an ultrasonic processor to evenly disperse the carbon nanotubes in the solution.

[0094] c) Adding silicon carbide: Add the required amount of silicon carbide (SiC) particles (5-10%) to the polyvinyl acrylate solution containing CNTs. Use a magnetic stirrer to stir thoroughly until the SiC is evenly dispersed in the solution to form a mixed solution of reinforcing materials. The mixed solution refers to a mixed solution of piezoelectric materials and materials such as carbon nanotubes and silicon carbide, and the reinforcing materials refer to materials such as carbon nanotubes and silicon carbide.

[0095] d) Adding piezoelectric material: gradually add the required amount of piezoelectric material BaTiO3 (45-60%) into the polyvinyl acrylate solution containing carbon nanotubes and stir thoroughly until the piezoelectric material is evenly dispersed in the solution.

[0096] e) Ultrasonic treatment: The mixture is placed in an ultrasonic processor again for further ultrasonic treatment to make the piezoelectric material, polyvinyl acrylate, and carbon nanotubes dispersed evenly and combined with each other.

[0097] f) Spray drying: The prepared mixed solution of piezoelectric material and reinforcing material is spray dried by a spray dryer to form spherical particles. The parameters of the spray dryer are adjusted to control the size and shape of the particles.

[0098] g) Screening: The particles obtained by spray drying are screened using a screening device to obtain spherical piezoelectric materials with uniform particle size.

[0099] h) Coupling agent treatment: Place the screened spherical piezoelectric material in a solution containing a silane coupling agent (0.5-1%), stir for a certain period of time (such as 1 hour), and then dry it in an oven for later use. This improves the bonding between the piezoelectric material and the substrate, and improves the mechanical properties and wear resistance of the material.

[0100] The piezoelectric material slow-release sphere 3 has the following functions: the piezoelectric material slow-release sphere 3 can also degrade organic pollutants; in a high-vibration environment, the vibration-damping effect of the piezoelectric material slow-release sphere 3 can protect the screen 2 from excessive stress and extend the life of the equipment; utilizing the vibration characteristics of the piezoelectric material, the slow-release sphere 3 can generate micro-vibrations on the surface of the screen 2, which helps prevent material blockage and accumulation and keep the screen 2 clean.

[0101] S4. Installation and adjustment of the screen 2: Assemble the screen frame into a multi-layer screen 2 structure and adjust the spacing between the multi-layer screens 2; ensure that the spacing between the two layers of screens 2 is adjustable and can be disassembled to meet different screening requirements and maintenance needs. The details are as follows:

[0102] a) Prepare the screen frame: Make sure the screen frame is clean and free of residue and dirt.

[0103] b) Install the lower screen 2: Place the lower screen 2 with a larger aperture on the bottom of the screen frame and align it with the edge of the screen frame. Use pins to fix the four corners and edges of the screen 2. The pins should be firmly inserted into the reserved holes on the screen frame to ensure that the screen 2 is flat and tight.

[0104] c) Install the upper screen 2: Place the upper screen 2 with a smaller aperture on the bottom screen 2 and align the edge of the screen frame. Use latches to fix the four corners and edges of the upper screen 2, and make sure the latches are tight to prevent the screen 2 from moving or loosening during use.

[0105] The same screen frame is composed of two layers of screens 2, the aperture of the lower layer of screen 2 is slightly larger than the aperture of the upper layer of screen 2. The use of double layers of screens 2 in the same screen frame has the following functions: reducing the wear of the piezoelectric material coating 1; increasing the structural stability of the screen 2, reducing the deformation and damage risk of the screen 2 in high-frequency vibration; and fixing the piezoelectric material slow-release body.

[0106] In practical applications, multiple screen frames can be placed from top to bottom, and the apertures of the screens 2 of different screen frames decrease from top to bottom, so that particles of different sizes can be screened out layer by layer.

[0107] d) Spacing adjustment: Adjust and fix the spacing between the upper screen 2 and the lower screen 2. The spacing between the upper and lower screens 2 can be 3-8 mm.

[0108] e) Screen aperture adjustment: Replace screen 2 as needed, remove the latch, remove the existing screen 2, select a new screen 2 with appropriate aperture and reinstall it according to the above steps.

[0109] f) Tightness adjustment: Check whether the screen 2 is tight and flat. If it is loose, readjust the position of the latch and ensure that the latch is firmly inserted.

[0110] g) Flatness check: Make sure that the screen 2 has no obvious protrusions or depressions. Use a tool to gently tap the screen 2 to make it flat.

[0111] h) Fixed use of vibrating screen dehydration equipment: Install the screen frame with screen 2 installed on the vibrating screen equipment to ensure that the screen 2 is stable and firm during the vibration process. Check the fastening of the screen 2 regularly and adjust the latch in time if it is loose.

[0112] S5. Piezoelectric material coating: The prepared piezoelectric material coating is evenly coated on the surface of the multi-layer screen 2 to ensure that the coating 1 is evenly and firmly covered to ensure the excitation effect and service life. The specific process includes:

[0113] a) Substrate preparation: Clean the metal substrate surface of the screen 2 to remove all grease, dust and other contaminants. You can use ethanol or acetone to wipe it to ensure that the surface is clean and dry.

[0114] b) Paint preparation: If the paint settles or stratifies during storage, use a stirrer to gently stir the paint to make it uniform.

[0115] c) Coating: Select appropriate coating tools (brush, roller or spray gun) to evenly apply the coating on the surface of the metal substrate. The thickness of coating 1 can be adjusted according to application requirements. It is usually recommended to apply multiple layers, and apply the next layer after each layer is dry to ensure the uniformity and coverage of coating 1.

[0116] d) Drying: After coating, place the coating 1 in a dry environment for solvent casting drying. Place the coated metal substrate on a flat plate or cast machine, ensuring that it is placed horizontally to avoid the coating 1 from flowing and uneven. The drying process can be natural drying at room temperature, or drying at low temperature to accelerate drying. It is recommended that the temperature does not exceed 60°C to prevent the coating 1 from cracking or falling off.

[0117] e) Multi-layer coating: If multi-layer coating is required, repeat the coating and drying process after each layer is completely dry. It is usually recommended to apply 3 to 5 layers to obtain the desired coating thickness and performance.

[0118] f) Curing: If you need to improve the adhesion and durability of coating 1, you can perform low-temperature curing after the last layer is dried. Place the coated substrate in an oven, gradually increase the temperature to about 60°C, maintain for 1 to 2 hours, and then cool naturally.

[0119] S6. The vibrating screen applies an excitation force: The vibrating screen applies an excitation force to excite the piezoelectric material coated on the screen 2, causing the piezoelectric material to generate intrinsic free carriers. These free carriers further generate active oxygen free radicals. The specific process includes:

[0120] a) Installation and preparation of the vibrating screen: Install the screen 2 coated with piezoelectric material in the vibrating screen equipment. Make sure that the screen 2 is firmly fixed so that it remains stable during vibration.

[0121] b) Vibrating screen start: Start the vibrating screen equipment to make it start to generate mechanical vibrations. These vibrations will be transmitted to the piezoelectric material coated on the screen 2 through the screen 2.

[0122] c) Mechanical stress transfer: The mechanical stress generated by the vibrating screen acts on the piezoelectric material, causing periodic deformation of the crystal lattice inside the material. This deformation will cause changes in the charge distribution inside the piezoelectric material.

[0123] d) Electric field generation: Due to the piezoelectric effect, piezoelectric materials will generate an internal electric field under mechanical stress. This electric field can separate electrons and holes to form free carriers.

[0124] e) Free carrier generation: Electrons in the piezoelectric material are excited to the conduction band, forming electron-hole pairs. Electrons and holes move inside the material, forming intrinsic free carriers.

[0125] f) Free carrier migration: Free carriers (electrons and holes) migrate to the surface of the material under the action of the electric field. These free carriers have high energy and can react with surrounding molecules or atoms.

[0126] g) Generation of reactive oxygen free radicals: After free carriers migrate to the surface of piezoelectric materials, they react with oxygen molecules in the air to generate reactive oxygen free radicals (such as superoxide anions OH, etc.). These free radicals have high chemical activity and can be used to degrade pollutants or perform other chemical reactions.

[0127] h) Continuous reaction: The vibrating screen works continuously and maintains mechanical vibration, so that the piezoelectric material continuously generates free carriers and reactive oxygen radicals. The efficiency of free carrier generation can be optimized by adjusting the frequency and intensity of the vibrating screen.

[0128] S7. High-pressure spray device assistance: During the slag screening process, the screen 2 is sprayed with high pressure, and the mechanical force generated by the high-pressure spray device is used to further stimulate the piezoelectric material and enhance its ability to generate active oxygen free radicals, thereby improving the degradation efficiency of organic pollutants. The specific process includes:

[0129] a) Installation and preparation of high-pressure spray device: Install the high-pressure spray device above or on the side of the vibrating screen so that the spray water flow can evenly cover the screen coated with piezoelectric material 2. Ensure that the nozzle of the high-pressure spray device is clean and unblocked, and the water source is sufficient and maintains appropriate water pressure.

[0130] b) Start the vibrating screen and high-pressure spray device: Start the vibrating screen device to generate mechanical vibrations to stimulate the piezoelectric material to generate free carriers. At the same time, start the high-pressure spray device to spray high-pressure water onto the screen 2 coated with the piezoelectric material, and the high-pressure water exerts additional mechanical force on the piezoelectric material.

[0131] c) Mechanical force of high-pressure water flow: The water flow generated by the high-pressure spray device impacts the surface of the piezoelectric material, generating instantaneous high mechanical stress. This mechanical stress further enhances the piezoelectric effect of the piezoelectric material and promotes the generation of more free carriers.

[0132] d) Enhanced generation of free carriers: Under the combined effects of the vibration of the vibrating screen and the high-pressure spray water flow, the number of free carriers generated by the piezoelectric material increases significantly, and the free carriers migrate to the surface of the material.

[0133] S8. Dehydration and drying treatment of dewatering screen: install the screen 2 coated with piezoelectric material in the dewatering screen, start the dewatering screen equipment, and dehydrate and dry the slag treated by the vibrating screen. The piezoelectric material generates intrinsic free carriers under the action of vibration, which degrades organic pollutants in the slag.

[0134] During the degradation of organic pollutants, active oxygen free radicals act on organic pollutants in the slag, decomposing them into harmless small molecules, thus achieving the purification and resource utilization of the slag. The whole process not only ensures the screening efficiency, but also takes into account environmental protection and cost-effectiveness.

[0135] a) The active oxygen free radicals generated by the piezoelectric material come into contact with the organic pollutants in the slag, and an oxidation reaction occurs, decomposing the organic pollutants into harmless small molecules (such as carbon dioxide and water). The specific degradation reaction is as follows:

[0136] Oxidation reaction of hydroxyl radical (•OH):

[0137] R-H+•OH→R•+H2O

[0138] R•+O2→ROO•

[0139] ROO•+RH→ROOH+R•

[0140] Oxidation reaction of superoxide anion (O2-):

[0141] O2-+RH→H2O2+R•

[0142] R•+O2→ROO•.

[0143] b) The vibrating screen and high-pressure spray device work continuously to ensure that new active oxygen free radicals are continuously generated to react with organic pollutants and continuously degrade them. The dewatering screen dehydrates and dries the slag treated by the vibrating screen.

[0144] c) During the vibration process, the slag is constantly screened and turned over, which increases the contact area between organic pollutants and active oxygen free radicals and improves the degradation efficiency.

[0145] Through the above steps, the present invention effectively realizes the screening of slag and the degradation of organic pollutants, and provides a high-efficiency, low-cost comprehensive solution, which not only improves the utilization rate of slag, but also reduces environmental pollution.

[0146] Two embodiments are listed below to specifically illustrate the application process of this method.

[0147] Embodiment 1:

[0148] (1) Equipment and materials:

[0149] Vibrating screen equipment: three-layer screen 2, sandblasted in advance, the sizes of screen 2 are 20mm, 10mm, and 5mm, used for coarse screening and preliminary degradation of organic pollutants.

[0150] Dewatering screen equipment: Screen 2 size is 50μm, used for further dewatering and fine screening.

[0151] High-pressure spraying device: The spraying pressure is 1MPa, generating high-pressure water flow to assist in the degradation of organic pollutants.

[0152] Screen 2 coated with piezoelectric material: The coating consists of 62% BaTiO3, 24% polyvinyl acrylate (PVEA), 6% silicon carbide and 8% carbon nanotubes (CNTs).

[0153] Each layer of the screen 2 can also fix 6 piezoelectric material slow-release balls 3, and the diameters of the balls are 23 mm, 13 mm, and 8 mm respectively.

[0154] (2) Specific steps:

[0155] Coating preparation and coating: Weigh the components according to the ratio of 62% BaTiO3, 24% PVEA, 8% silicon carbide and 6% CNT. After mixing these components, add an appropriate amount of solvent (ethanol) and mix them evenly in an ultrasonic processor until a stable suspension is formed.

[0156] Coating process: The mixed piezoelectric material coating is evenly coated on the screen 2 of the vibrating screen and the dewatering screen. The solvent casting method is used for drying so that the coating adheres firmly to the surface of the screen 2.

[0157] Preparation of piezoelectric material sustained-release sphere 3: Weigh the components according to the ratio of 60% BaTiO3, 25% PVEA, 10% silicon carbide and 5% CNT. After mixing these components, add an appropriate amount of solvent (ethanol) and mix them evenly in an ultrasonic processor until a stable suspension is formed. After spray drying, place it in a solution containing a silane coupling agent, stir it for a certain period of time, and then dry it in an oven.

[0158] Parameter settings of the vibrating screen screening equipment: the exciting force is set to 420kN, and the frequency is set to 13Hz.

[0159] Installation of the screen 2: The screen 2 coated with the piezoelectric material is installed in the vibrating screen in order of size, with the top being 20 mm, the middle being 10 mm, and the bottom being 5 mm.

[0160] Start the vibrating screen: Start the vibrating screen equipment, and the slag passes through each layer of screen 2 under mechanical vibration for preliminary screening and processing. The piezoelectric material coated on the screen 2 generates free carriers under mechanical vibration, which react with oxygen molecules in the air to generate active oxygen free radicals, and preliminarily degrade organic pollutants.

[0161] High-pressure spray treatment: The spray pressure is set to 1 MPa. Install the high-pressure spray device above the vibrating screen to ensure that the high-pressure water flow evenly covers the screen 2. Start the high-pressure spray device to spray high-pressure water flow to further enhance the mechanical stress of the piezoelectric material and improve the generation efficiency of free carriers.

[0162] Dehydration and drying treatment of dewatering screen: The screen 2 coated with piezoelectric material is installed in the dewatering screen, and the size of the screen 2 is 50μm. The dewatering screen equipment is started to dehydrate and dry the slag treated by the vibrating screen. The piezoelectric material coated on the screen 2 continuously generates free carriers and active oxygen free radicals under the action of mechanical vibration, further degrading the organic pollutants in the slag.

[0163] The organic matter content of the slag before and after treatment was tested. The organic pollutant content of the treated slag dropped from 6.50% to 1.14%, a reduction of 82%. After screening and dehydration, the moisture content of the slag dropped significantly, making it drier and easier to handle. The purified slag can be further processed or directly used for resource utilization, such as fluidized filler, fire-free building materials, etc.

[0164] Embodiment 2:

[0165] (1) Equipment and materials:

[0166] Vibrating screen equipment: The sizes of screen 2 are 20mm, 10mm, and 5mm, which are used for coarse screening and preliminary degradation of organic pollutants.

[0167] Dewatering screen equipment: Screen 2 size is 50μm, used for further dewatering and fine screening.

[0168] High-pressure spraying device: The spraying pressure is 1MPa, generating high-pressure water flow to assist in the degradation of organic pollutants.

[0169] Screen 2 coated with piezoelectric material: The coating consists of 68% ZnO, 19% polyvinyl acrylate (PVEA), 8% silicon carbide and 5% carbon nanotubes (CNTs).

[0170] Each layer of the screen 2 can also fix 6 piezoelectric material slow-release balls 3, and the diameters of the balls are 23 mm, 13 mm, and 8 mm respectively.

[0171] (2) Specific steps:

[0172] Coating preparation and coating: Weigh the components according to the ratio of 68% ZnO, 19% PVEA, 8% silicon carbide and 5% CNT. After mixing these components, add an appropriate amount of solvent (ethanol) and mix them evenly in an ultrasonic processor until a stable suspension is formed.

[0173] Coating process: The mixed piezoelectric material coating is evenly coated on the screen 2 of the vibrating screen and the dewatering screen. The solvent casting method is used for drying so that the coating adheres firmly to the surface of the screen 2.

[0174] Preparation of piezoelectric material sustained-release sphere 3: Weigh the components according to the ratio of 60% ZnO, 25% PVEA, 10% silicon carbide and 5% CNT. After mixing these components, add an appropriate amount of solvent (ethanol) and mix them evenly in an ultrasonic processor until a stable suspension is formed. After spray drying, place it in a solution containing a silane coupling agent, stir it for a certain period of time, and then dry it in an oven.

[0175] Parameter settings of the vibrating screen screening equipment: the exciting force is set to 420kN, and the frequency is set to 13Hz.

[0176] Installation of the screen 2: The screen 2 coated with the piezoelectric material is installed in the vibrating screen in order of size, with the top being 20 mm, the middle being 10 mm, and the bottom being 5 mm.

[0177] Start the vibrating screen: Start the vibrating screen equipment, and the slag passes through each layer of screen 2 under mechanical vibration for preliminary screening and processing. The piezoelectric material coated on the screen 2 generates free carriers under mechanical vibration, which react with oxygen molecules in the air to generate active oxygen free radicals, and preliminarily degrade organic pollutants.

[0178] High-pressure spray treatment: The spray pressure is set to 1 MPa. Install the high-pressure spray device above the vibrating screen to ensure that the high-pressure water flow evenly covers the screen 2. Start the high-pressure spray device to spray high-pressure water flow to further enhance the mechanical stress of the piezoelectric material and improve the generation efficiency of free carriers.

[0179] Dehydration and drying treatment of dewatering screen: The screen 2 coated with piezoelectric material is installed in the dewatering screen, and the size of the screen 2 is 50μm. The dewatering screen equipment is started to dehydrate and dry the slag treated by the vibrating screen. The piezoelectric material coated on the screen 2 continuously generates free carriers and active oxygen free radicals under the action of mechanical vibration, further degrading the organic pollutants in the slag.

[0180] The organic matter content of the slag before and after treatment was tested. The organic pollutant content of the treated slag dropped from 7.11% to 0.88%, a reduction of 87%. After screening and dehydration, the moisture content of the slag dropped significantly, making it drier and easier to handle. The purified slag can be further processed or directly used for resource utilization, such as fluidized filler, fire-free building materials, etc.

[0181] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for using piezoelectric materials to screen soil and degrade pollutants, characterized in that: The following steps are involved: S1. Selection of piezoelectric materials: Select appropriate piezoelectric materials as raw materials for coating preparation; S2. Coating preparation: 62-68% of piezoelectric material, 19-24% of polyvinyl acrylate, 6-8% of silicon carbide, and 5-8% of carbon nanotubes are mixed by ultrasonic to prepare a piezoelectric material coating; S3. Screen structure design: According to the size of the soil particles, select a screen with a smaller hole diameter than the soil particles; S4. Screen installation and adjustment: Assemble the screen frame into a multi-layer screen structure and adjust the spacing between the multi-layer screens; S5. Piezoelectric material coating: The prepared piezoelectric material coating is evenly coated on the surface of the multi-layer screen; S6. Vibrating screen implements excitation force: through the excitation force of the vibrating screen, the piezoelectric material coated on the screen is excited to generate intrinsic free carriers in the piezoelectric material; S7. High-pressure spray device assistance: During the slag screening process, the screen is sprayed with high pressure to further stimulate the piezoelectric material to generate intrinsic free carriers; S8. Dehydration and drying treatment of dewatering screen: install the screen coated with piezoelectric material in the dewatering screen, start the dewatering screen equipment, and dehydrate and dry the slag treated by the vibrating screen. The piezoelectric material generates intrinsic free carriers under the action of vibration, which degrades the organic pollutants in the slag.

2. The method for using the piezoelectric material for slag screening and pollutant degradation according to claim 1 is characterized in that: In the step S1, the selected piezoelectric materials include BaTiO3, MoS2, ZnO, Ag / BaTiO3, and HPVDF / BTO-OV.

3. The method for using piezoelectric materials for slag screening and pollutant degradation according to claim 1 is characterized in that: In step S2, the coating preparation process includes: S21. Prepare a solution: dissolve a required amount of polyvinyl acrylate in deionized water or ethanol, and stir until completely dissolved to form a uniform polyvinyl acrylate solution; S22. Dispersing carbon nanotubes: adding a desired amount of carbon nanotubes to a polyvinyl acrylate solution, and ultrasonically treating the mixture using an ultrasonic processor to uniformly disperse the carbon nanotubes in the solution; S23. Adding silicon carbide: adding a desired amount of silicon carbide particles to the polyvinyl acrylate solution containing carbon nanotubes, and stirring thoroughly until the silicon carbide is evenly dispersed in the solution; S24. Adding a piezoelectric material: gradually adding a desired amount of a piezoelectric material to the polyvinyl acrylate solution containing carbon nanotubes, stirring thoroughly until the piezoelectric material is evenly dispersed in the solution; S25 ultrasonic treatment: the mixture formed in step S24 is again placed in an ultrasonic processor for further ultrasonic treatment to uniformly disperse the piezoelectric material, polyvinyl acrylate, and carbon nanotubes and bond them to each other; S26. Adjust viscosity: slowly add deionized water while stirring until the coating reaches the desired viscosity; S27. Degassing: The prepared coating mixture is allowed to stand, or a vacuum degassing device is used to remove bubbles generated during the mixing process; S28. Storage and Use: Store the prepared paint in a sealed container to avoid contact with light and air; stir slightly before use to ensure the uniformity of the paint.

4. The method for using piezoelectric materials for slag screening and pollutant degradation according to claim 3 is characterized in that: During the ultrasonic treatment in steps S22 and S25, the ultrasonic processor adopts an intermittent treatment method, heating for a period of time until the solution reaches a specified dissolution temperature, stopping heating, and continuing heating when the solution temperature is lower than the specified dissolution temperature, and repeating this operation until the ultrasonic treatment is completed.

5. The method for using piezoelectric materials for slag screening and pollutant degradation according to claim 1, characterized in that: In the step S3, when designing the screen structure, it also includes preparing piezoelectric material slow-release spheres to be sandwiched between the multiple layers of screens; The preparation process of piezoelectric material sustained-release spheres includes: S31. Prepare a solution: dissolve a desired amount of polyvinyl acrylate in ethanol and stir until completely dissolved to form a uniform polyvinyl acrylate solution; S32. Dispersing carbon nanotubes: adding a desired amount of carbon nanotubes to a polyvinyl acrylate solution, and ultrasonically treating the mixture using an ultrasonic processor to uniformly disperse the carbon nanotubes in the solution; S33 adding silicon carbide: adding a desired amount of silicon carbide particles to the polyvinyl acrylate solution containing carbon nanotubes, stirring thoroughly until the silicon carbide is evenly dispersed in the solution to form a mixed solution of a reinforcing material; S34. Adding a piezoelectric material: gradually adding a desired amount of a piezoelectric material to the polyvinyl acrylate solution containing carbon nanotubes, stirring thoroughly until the piezoelectric material is evenly dispersed in the solution; S35 ultrasonic treatment: the mixture formed in step S34 is again placed in an ultrasonic processor for further ultrasonic treatment to uniformly disperse the piezoelectric material, polyvinyl acrylate, and carbon nanotubes and bond them to each other; S36 spray drying: spray drying the prepared mixed solution of the piezoelectric material and the reinforcing material to form spherical particles, and controlling the size and shape of the particles; S37. Screening: Screening the particles obtained by spray drying to obtain a spherical piezoelectric material with uniform particle size; S38. Coupling agent treatment: Place the screened spherical piezoelectric material in a solution containing a silane coupling agent, stir it, and dry it for later use.

6. The method for using piezoelectric materials for slag screening and pollutant degradation according to claim 1, characterized in that: In step S4, the screen installation and adjustment specifically include: S41. Prepare the screen frame: Make sure the screen frame is clean and free of residue and dirt; S42. Install the lower screen: Place the lower screen with a larger aperture on the bottom of the screen frame, align the edge of the screen frame, and fix the top corners and edges of the lower screen; S43. Install the upper screen: Place the upper screen with a smaller aperture on the lower screen, align the edge of the screen frame, and fix the top corners and edges of the upper screen; S44. Spacing adjustment: adjust the spacing between the upper screen and the lower screen and fix it; S45. Fixing of vibration screen dehydration equipment: Install the screen frame with the screen onto the vibration screen equipment and fix it.

7. The method for using piezoelectric materials for slag screening and pollutant degradation according to claim 1, characterized in that: In step S5, the process of coating the piezoelectric material specifically includes: S51. Substrate preparation: Clean the metal substrate surface of the screen to remove all grease, dust and contaminants; S52. Paint preparation: Use a stirrer to gently stir until the paint is uniform; S53. Coating: coating the coating evenly on the metal substrate surface of the screen; when multiple layers of coating are applied, the next layer of coating is applied after each layer of coating is dried; S54. Drying: After coating is completed, the coating is placed in a dry environment for solvent casting drying.

8. The method for using piezoelectric materials for slag screening and pollutant degradation according to claim 1, characterized in that: In step S6, the process of exciting the piezoelectric material coated on the screen by the excitation force of the vibrating screen to make the piezoelectric material generate intrinsic free carriers includes: S61. Installation and preparation of the vibrating screen: The screen coated with the piezoelectric material is installed in the vibrating screen device and fixed firmly; S62. Vibrating screen start: start the vibrating screen equipment, start to generate mechanical vibration, and transmit the vibration to the piezoelectric material coated on the screen through the screen; S63. Mechanical stress transfer: The periodic deformation of the internal lattice of the piezoelectric material under the mechanical stress generated by the vibrating screen; S64. Electric field generation: Piezoelectric materials generate internal electric fields and separate electrons and holes to form free carriers; S65. Free carrier generation: The electrons in the piezoelectric material are excited to the conduction band to form electron-hole pairs. The electrons and holes move inside the material to form intrinsic free carriers. S66. Free carrier migration: Free carriers migrate to the surface of the material under the action of an electric field; S67. Generation of reactive oxygen free radicals: Free carriers react with oxygen molecules in the air to generate reactive oxygen free radicals; S68.Continuous reaction: The vibrating screen works continuously, maintaining mechanical vibration, so that the piezoelectric material continues to generate free carriers and active oxygen free radicals.

9. The method for using piezoelectric materials for slag screening and pollutant degradation according to claim 1, characterized in that: In step S7, during the slag screening process, the process of spraying the screen with high pressure to further excite the piezoelectric material to generate intrinsic free carriers includes: S71. Installation and preparation of high-pressure spray device: Install the high-pressure spray device above or on the side of the vibrating screen so that the spray water flow can evenly cover the screen coated with piezoelectric material; S72. Start the vibrating screen and high-pressure spray device: Start the vibrating screen equipment and generate mechanical vibration, and start the high-pressure spray device to spray high-pressure water onto the screen coated with piezoelectric material to apply additional mechanical force to the piezoelectric material; S73. Enhanced generation of free carriers: Under the combined effects of the vibration of the vibrating screen and the high-pressure spray water flow, the piezoelectric material generates more free carriers, and the free carriers migrate to the surface of the piezoelectric material.

10. The method for using piezoelectric materials for slag screening and pollutant degradation according to claim 1, characterized in that: In step S8, the process of dehydration and drying by the dehydration screen includes: S81. The active oxygen free radicals generated by the piezoelectric material come into contact with the organic pollutants in the slag, and an oxidation reaction occurs, decomposing the organic pollutants into harmless small molecules; S82. The vibrating screen and high-pressure spray device work continuously to generate new active oxygen free radicals to react with organic pollutants and continuously degrade organic pollutants; the dewatering screen dehydrates and dries the slag treated by the vibrating screen.

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