Air purifying device

Abstract

The application discloses an air purification device and belongs to the technical field of atmospheric pollution control. The air purification device comprises an air inlet, a reverse corona plasma unit and an air outlet in sequence in the direction of air flow, wherein the reverse corona plasma unit comprises a corona electrode, an auxiliary electrode, a whole VOCs catalyst comprising a honeycomb base and a VOCs catalyst coated on the inner and outer surfaces of the honeycomb base, the inner and outer surfaces of the honeycomb base comprising whiskers, the active component of the whole VOCs catalyst comprising Ce-BiVO4-TiO2 / Ag and a grounding electrode. The air purification device can efficiently treat VOCs and bacteria in the air and reduce the adverse effects of bad air.

Description

[0001] This application is a divisional application of the patent application with the application date of August 26, 2022, the application number of 202211033269.0, and the invention name of "Air purification and sterilization method". TECHNICAL FIELD

[0002] Embodiments of the present application relate to the field of atmospheric pollution control technology, in particular to an air purification device. BACKGROUND

[0003] Air quality is closely related to the quality of life. Due to environmental influence, air (especially indoor air) contains bacteria such as Staphylococcus aureus and Escherichia coli, which can cause bacterial infections, and severe infections can lead to death. In addition, air (especially indoor air) also contains volatile organic compounds (VOCs). Most VOCs have three effects (carcinogenic, teratogenic, and mutagenic), and their toxicity, persistence, and non-degradability seriously endanger human health and human living space. SUMMARY

[0004] In order to solve at least one aspect of the above problems and defects in the prior art, embodiments of the present application propose an air purification and sterilization method, which is expected to sterilize air (especially indoor air in homes and workshops) and remove VOCs therein to improve the living environment.

[0005] According to one aspect of the present application, an air purification and sterilization method is provided, comprising:

[0006] A reverse corona plasma unit is provided to form a plasma, the reverse corona plasma unit is sequentially provided with a corona electrode, an auxiliary electrode, a monolithic VOCs catalyst, and a grounding electrode in the direction of airflow, the monolithic VOCs catalyst comprises a honeycomb-shaped substrate and a VOCs catalyst coated on the inner and outer surfaces of the honeycomb-shaped substrate, the inner and outer surfaces of the honeycomb-shaped substrate comprise whiskers, and the active ingredients of the monolithic VOCs catalyst comprise Ce-BiVO4-TiO2 / Ag;

[0007] Under the irradiation of visible light and / or ultraviolet light, VOCs and bacteria in the air are treated by Ce-BiVO4-TiO2 / Ag;

[0008] VOCs and bacteria in the air are treated using active ingredients in the plasma.

[0009] According to another aspect of the present application, an air purification device is provided, which sequentially comprises an air inlet, a reverse corona plasma unit, and an air outlet in the direction of airflow,

[0010] The anti-corona plasma unit comprises, in the direction of the airflow flow, in sequence:

[0011] A corona electrode;

[0012] An auxiliary electrode;

[0013] A monolithic VOCs catalyst comprising a honeycomb substrate and a VOCs catalyst coated on the inner and outer surfaces of the honeycomb substrate, the inner and outer surfaces of the honeycomb substrate comprising whiskers, the active ingredients of the monolithic VOCs catalyst comprising Ce-BiVO4-TiO2 / Ag; and

[0014] A ground electrode.

[0015] Other objects and advantages of the present application will become apparent and the present application will be more fully understood when considered in connection with the following description of preferred embodiments, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0016] These and / or other aspects and advantages of the present application will become apparent and be more fully understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0017] Figure 1 An air purification device according to one embodiment of the present application is shown;

[0018] Figure 2 An air purification and sterilization method according to one embodiment of the present application is shown. DETAILED DESCRIPTION

[0019] The technical solutions of the present application will be further described in detail below by way of examples, and in conjunction with the drawings. In the description, identical or similar reference numerals indicate identical or similar components. The following description of the embodiments of the present application with reference to the drawings is intended to explain the general inventive concept of the present application, and should not be understood as a limitation of the present application.

[0020] In addition, in the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. However, it will be apparent to one of ordinary skill in the art that one or more embodiments can be practiced without these specific details.

[0021] In the embodiments of the present application, an air purification device is provided to desirably sterilize bacteria in the air while being able to remove VOCs in the air.

[0022] As Figure 1 shown, the air purification device 100 is in the direction of the airflow flow (in the direction of the arrow A in the drawing) from the left to the right. The air purification device 100 comprises a corona electrode 110, an auxiliary electrode 120, and a ground electrode 130. Figure 1In the example shown, the air purification device 100 includes, in order from left to right (i.e., in the direction of the air flow), an air inlet 10, a reverse corona plasma cell 40, and an air outlet 60.

[0023] In an example, the air purification device 100 further includes a radiation cell 30 between the air inlet 10 and the reverse corona plasma cell 40.

[0024] In an example, the air purification device 100 further includes a filter cell 20 between the air inlet 10 and the radiation cell 30.

[0025] In an example, the air purification device 100 further includes a catalyst bed 50 between the reverse corona plasma cell 40 and the air outlet 60.

[0026] In use, air to be treated enters the air inlet 10 and passes through, in order, the filter cell 20 (if any), the radiation cell 30 (if any), the reverse corona plasma cell 40, and the catalyst bed 50 (if any), and finally exits the air outlet 60 as treated air.

[0027] The air inlet 10 and the air outlet 60 are provided at opposite ends of the air purification device 100 to allow air to be treated to enter and exit the air purification device 100. In the example shown, the air inlet 10 is located at the left end of the air purification device 100, and the air outlet 60 is located at the right end of the air purification device 100. Figure 1

[0028] The filter cell 20 is configured to adsorb dust in the air to avoid the dust remaining in the air, thereby causing adverse effects to humans (e.g., occupants or workers in a factory).

[0029] Further, as shown in the example, the filter cell 20 includes a main frame (not shown), an electrostatic net 22 located on the main frame, and a filter 24 located in the main frame. The filter 24 is disposed downstream of the electrostatic net 22 in the direction of the air flow. In the example shown, the electrostatic net 22 is located at the front side of the filter cell 20, and the filter 24 is located at the back side of the filter cell 20. In an example, the filter cell 20 further includes an interface to provide electrical energy to the electrostatic net. Figure 1 Figure 1

[0030] In an example, the main frame is generally a cuboid, and includes a hollow portion (e.g., in the form of a cuboid) at the lower portion thereof, and the filter 24 is located in the hollow portion. The interface is located at the upper portion of the main frame. Embodiments of the present disclosure do not limit the specific shape of the main frame, nor the location and shape of the hollow portion, as long as the main frame is capable of supporting the filter and the electrostatic net.

[0031] ​​​The main body frame (in particular, at the hollow portion thereof) comprises opposite first and second open sides. The first open side is closed by the electrostatic net 22. The second open side is provided with at least one mounting rod (not shown in the drawings) for mounting the radiation unit 31. The mounting rod can be arranged perpendicular to the air flow direction to facilitate the air flow in the flow direction (from left to right) and to help the UV radiation unit 30 form radiation light rays parallel to the flow direction. Of course, the mounting rod can also be arranged obliquely relative to the air flow direction.

[0032] The electrostatic net 22 is connected (e.g. via an interface) to a negative direct current high voltage power supply, so that the dust in the air is charged by the electrostatic net 22 to allow adsorption on the following filter 24 (which is grounded).

[0033] The filter 24 is integrally formed with an ultra-fine glass fiber filter paper, nylon wire and plastic frame by injection molding. In an example, the outer surface of the ultra-fine glass fiber filter paper has a moisture-proof coating. The filter 24 is in a V-shaped pleated paper structure, which can be prepared by a hot roller pressing process, for example. The V-shaped pleated paper structure can ensure that the filtering area is fully utilized, and the dust is uniformly distributed on the filter material surface, while it can also function as a flow guide to make the air flow uniform and the pressure drop slow, which is economical, safe and has a long service life.

[0034] The radiation unit 30 comprises at least one UV light source. The UV light source emits first UV radiation. The wavelength of the first UV radiation can be selected as 185 nm, 222 nm, 254 nm, 308 nm, etc., or a combination of several different wavelength UV light sources. The first UV radiation can be used to sterilize bacteria in the air. The first UV radiation can also act on the active ingredient of the integrated VOCs to facilitate the active ingredient to purify the air.

[0035] Optionally, the radiation unit 30 further comprises at least one visible light source. The visible light source emits visible light of 400-700 nm. The visible light can act on the active ingredient of the integrated VOCs to facilitate the active ingredient to purify the air.

[0036] The UV light source and the visible light source are both located on the mounting plate. The embodiments of the present application do not limit the number of UV light sources and visible light sources, which can be arranged as needed by those skilled in the art. The UV light source and the visible light source can be spaced one, two, three or more from each other, or the visible light source can be arranged in the middle of the mounting plate and the UV light source can be arranged at both ends of the mounting plate. The embodiments of the present application do not limit the arrangement of the UV light source and the visible light source. In an example, the UV light source and the visible light source are arranged on the mounting plate towards the integrated VOCs catalyst to facilitate the radiation emitted by the light source to more fully react with the integrated VOCs catalyst.

[0037] The reverse corona plasma unit 40 comprises, in order along the direction of the gas flow, a corona electrode 42, an auxiliary electrode 44, a monolithic VOCs catalyst 46, and a grounded electrode 48.

[0038] The corona electrode 42 is powered by a negative high-voltage DC power supply. During the discharge process, the corona electrode 42 ionizes the gas near the corona electrode 42 to generate a large number of negative charges, which can interact with the monolithic VOCs catalyst 46 to form a reverse corona plasma. The corona electrode 42 can be made of a tungsten wire with a diameter of 2-6 mm.

[0039] The auxiliary electrode 44 suppresses the development of spark discharge from the corona electrode 42. The auxiliary electrode 44 can be made of a tungsten wire with a diameter of 2-6 mm.

[0040] The monolithic VOCs catalyst 46 comprises a honeycomb substrate and a VOCs catalyst coated on the inner and outer surfaces of the honeycomb substrate.

[0041] The honeycomb substrate has a large specific surface area, which can provide more attachment sites for VOCs catalyst coating. In an example, the honeycomb substrate of the monolithic VOCs catalyst 46 is made of cordierite, foamed metal (nickel), alumina, or silicon carbide.

[0042] The inner and outer surfaces of the honeycomb substrate include whiskers. In an example, the whiskers include mullite whiskers, aluminum borate whiskers, or silicon carbide whiskers.

[0043] The active component of the monolithic VOCs catalyst 46 includes a Ce-BiVO4-TiO2 / Ag catalyst.

[0044] In an example, the method for preparing the monolithic VOCs catalyst comprises the following steps:

[0045] providing a honeycomb substrate with whiskers grown on the surface;

[0046] providing a Ce-BiVO4-TiO2 / Ag catalyst;

[0047] mixing the Ce-BiVO4-TiO2 / Ag catalyst, sodium carboxymethyl cellulose, silica sol, and water in a first mass ratio (e.g., (20-30):(15-20):(10-15):(30-45)) to obtain a first reactant, coating the first reactant on the inner and outer surfaces of the honeycomb substrate with whiskers grown on the surface, and performing a drying process and then calcining (calcining at 300-600°C for 3-6 hours) to obtain the monolithic VOCs catalyst.

[0048] providing a honeycomb substrate with whiskers grown on the surface comprises:

[0049] The honeycomb substrate is embedded by the whisker raw material, anhydrous aluminum sulfate and anhydrous sodium sulfate to obtain a mixture;

[0050] After the mixture is calcined at 900-1200℃ (for example, 1000℃) for 2-12 hours (for example, 8 hours) and cooled, the whiskers grow on the inner and outer surfaces of the honeycomb substrate.

[0051] In an example, the Ce-BiVO4-TiO2 / Ag catalyst is provided by:

[0052] A cerium source, a bismuth source, a vanadium source and citric acid are mixed according to a second mass ratio to form a sol, and after drying (for example, in a constant temperature drying oven) at 80-100℃ (for example, 90℃), a gel is formed, and the gel is calcined at 300-500℃ (for example, 350-400℃) for 3-8 hours (for example, 4-6 hours) to obtain active powder Ce-BiVO4.

[0053] The active powder Ce-BiVO4 solution is mixed with TiO2 according to a third mass ratio, and reacted under ultrasonic conditions (for example, under ultrasonic oscillation conditions) for 0.5-2 hours (for example, 1-1.5 hours), and after drying (for example, rotary drying) at 60-100℃ (for example, 80-90℃) for 2-5 hours (for example, 3-4 hours), the Ce-BiVO4-TiO2 is obtained by calcining at 300-500℃ (for example, 400-450℃) for 3-8 hours (for example, 5-6 hours).

[0054] The silver source is mixed with the Ce-BiVO4-TiO2 according to a fourth mass ratio, a reducing agent (for example, glycerol) is added to the mixed solution, and after drying (for example, rotary drying) at 60-100℃ (for example, 80-90℃) for 2-5 hours (for example, 3-4 hours), the Ce-BiVO4-TiO2 / Ag catalyst is obtained by calcining at 300-500℃ (for example, 400-450℃) for 3-8 hours (for example, 5-6 hours).

[0055] The inventors of the present application have found that the TiO2 catalyst has a wide (specifically, 3.2eV) band gap, and the utilization rate of ultraviolet light and visible light is low, and the light response range is low; BiVO4 can also be used as a photocatalytic material, but the utilization rate of visible light and ultraviolet light is also relatively low, thereby limiting the application of TiO2 and BiVO4 in photocatalysis. In view of this, the present application combines TiO2 and BiVO4 together and performs ion doping (Ce and Ag), which expands the light response range and improves the catalytic efficiency of the catalyst.

[0056] Specifically, cerium (Ce) ions are doped into the crystal structure of the BiVO4 catalyst, changing the internal composition of the catalyst, thereby changing its electronic structure, achieving regulation of its energy band and band gap width, and thus improving the photocatalytic activity. Cerium (Ce) ions are considered to be relatively effective dopants due to their unique 4f electron orbital configuration. Research results show that in the BiVO4 lattice, Ce substitution for Bi can significantly inhibit the recombination of photo-generated charges and improve the photocatalytic activity. The reason is that in Ce-doped BiVO4, under the conditions of Bi / V deficiency and O enrichment, Ce Bi 1+ and Ce V 1- are the main defects and can become p-type materials, in which Ce Bi 1+ degrades the activity with an unoccupied deep level, which is mainly composed of the 4f orbit of Ce and is a deep recombination center. For Ce V 1- defects, no localized states are found in Ce-BiVO4, which is sensitive to both chemical potential and Fermi energy, indicating that the conditions of Bi / V deficiency and O enrichment are conducive to eliminating deep level states and improving photocatalytic performance. Therefore, with the establishment of the Ce V 1- doping process, doping Ce into BiVO4 can enhance the photocatalytic activity.

[0057] When TiO2 and Ce-BiVO4 are combined, the lattice spacing is adjusted, which in turn causes a change in the crystal phase, thereby expanding the light response range.

[0058] In the above preparation process, Ag + is reduced to nano silver particles (AgNPs) during the calcination process, thereby making the Ce-BiVO4-TiO2 / Ag catalyst have excellent photocatalytic performance. Specifically, the photocatalyst absorbs light energy under the irradiation of a certain wavelength of radiation (such as ultraviolet light radiation and visible light radiation), and when excited by energy greater than its band gap, the electrons in the valence band are excited to jump to the conduction band, forming photo-generated electrons (e - ), and at the same time, holes (h + ) are generated in the valence band. h + has strong oxidizing properties, and e -The AgNPs have reducing property, and can respectively react with water and oxygen to produce hydroxyl radical, superoxide anion, hydrogen peroxide and singlet oxygen. The AgNPs can act as electron traps, and can assist electron-hole separation and trap electrons by generating local electric field, so that the number of active species such as hydroxyl radical, superoxide anion, hydrogen peroxide and singlet oxygen is increased, and thus the photocatalytic activity is enhanced. Moreover, the photo-generated electrons can collide with VOCs gas-phase molecules, so that the chemical bonds of the VOCs gas-phase molecules are broken to generate molecular fragments and other small molecule substances, and thus the VOCs in the air can be removed by using photocatalytic activity.

[0059] Moreover, the AgNPs also help air sterilization. The silver ions released from the AgNPs can interact with the enzyme and thiol group (—SH) of biological macromolecules in the bacterial body, so that the enzyme and the biological macromolecules are inactivated, and thus the growth of bacteria is limited. In addition, the AgNPs have nano effect, that is, the AgNPs adhere to the cell wall and penetrate into the bacterial cells, which can cause the structure of the bacterial cells to change, and thus the bacterial cells die, so that the hybrid film can also play a role in dark conditions.

[0060] Further, the cerium source includes at least one of cerium acetate and a hydrate thereof, cerium oxalate and a hydrate thereof, cerium nitrate and a hydrate thereof; the bismuth source includes at least one of bismuth citrate, bismuth trichloride, bismuth nitrate and a hydrate thereof; and the vanadium source includes at least one of vanadyl sulfate, vanadyl oxalate, vanadyl acetylacetone, vanadyl chloride and vanadyl phosphate.

[0061] In the embodiment in which cerium acetate, bismuth citrate and vanadyl oxalate are used, the second mass ratio is (10-15):(15-20):(5-10):(60-70), for example, 12:18:8:62.

[0062] Further, the third mass ratio is (15-20):(80-85), for example, 18:82. The fourth mass ratio is (10-20):(80-90), for example, 15:85.

[0063] In the embodiment of the present application, the corona electrode 42 ionizes the gas near the corona electrode 42 to generate a large number of negative charges during the discharge process, and the charges accumulate on the inner and outer surfaces of the monolithic VOCs catalyst 46; the accumulated charges generate a superimposed electric field in the internal pores of the honeycomb substrate, and when the field strength of the superimposed electric field reaches or exceeds the breakdown field strength of the whiskers on the internal pore surfaces of the honeycomb substrate, a reverse corona plasma is generated. The reverse corona plasma is generated in the internal pores of the honeycomb substrate, thereby forming a plasma reaction channel, in which the free electrons, high-energy ions, and active particles generated in the plasma reaction channel are closely combined with the active components of the VOCs catalyst on the inner and outer surfaces of the monolithic VOCs catalyst 46, fully exerting the advantages of both the high reactivity of the plasma and the high reaction selectivity of the VOCs, activating the reaction activity of the VOCs catalyst, improving the reaction selectivity of the reverse corona plasma, and promoting the VOCs reaction to occur at room temperature or low temperature. Ultimately, the VOCs in the air are oxidized to H2O and O2.

[0064] In the embodiment of the present application, during the reverse corona plasma discharge process, the dielectric constant of the active component Ce-BiVO4-TiO2 / Ag of the monolithic VOCs catalyst can reach more than 10000 at room temperature. During the reverse corona plasma discharge process, due to the presence of Ce-BiVO4-TiO2 / Ag, the monolithic VOCs catalyst can be polarized at a relatively small electric field strength, significantly enhancing the discharge intensity of the reverse corona plasma, thereby obtaining a large number of free electrons, hydroxyl radicals, ozone, and other active particles. In this way, on the one hand, the VOCs gas-phase molecules can be induced to undergo redox reactions to generate CO2 and H2O, and on the other hand, a large number of free electrons can cause serious breakdown and damage to the cell membranes of bacteria and viruses, enhancing the sterilization effect. In this way, the monolithic VOCs catalyst arranged in the reverse corona plasma can improve the energy utilization efficiency of the reverse corona plasma and reduce the energy consumption of the reverse corona plasma.

[0065] In an example, the plasma further includes second ultraviolet radiation. The second ultraviolet radiation can include a wavelength of 150 nm, or 160 nm. The second ultraviolet radiation has a wavelength that is less than the wavelength of the first ultraviolet radiation. The second ultraviolet radiation will work together with the first ultraviolet radiation to treat VOCs and bacteria in the air. This will be described in detail below.

[0066] In an example, the plasma can be used to sterilize air. The high-energy ions, active radicals, and other components contained in the plasma are very easy to chemically react with enzymes, proteins, and nucleic acids in bacteria, mold, spores, and viruses, and can destroy and disrupt the survival functions of microorganisms, causing all types of microorganisms to die. The directional movement of high-energy particles in the plasma can "crush" the proteins of bacteria, cells, and viruses and destroy the integrity of the genes, escape electrons and free electrons are accelerated to obtain very high energy, and the high-energy electrons and breakdown etching effects can cause serious breakdown and damage to the cell membranes of bacteria and viruses. The plasma targets to destroy various structures of microorganisms, etches the cell wall, destroys the biofilm and peroxidized lipids, and the bacterial DNA and RNA can be damaged by oxidation.

[0067] The catalyst bed 50 is used to treat ozone in air. Ozone can be generated, for example, during plasma formation, and the catalyst bed 50 located behind the reverse corona plasma cell 40 can treat it. The catalyst bed 50 includes a 3D foam ceramic carrier and a manganese, cobalt bimetallic active component loaded on the surface of the 3D foam ceramic carrier.

[0068] In an example, providing a catalyst bed includes:

[0069] Mn(CH3COO)2-4H2O, Co(CH3COO)2-4H2O, and anhydrous citric acid are mixed in a mass ratio of (15-20):(25-30):(50-60) to form a precursor solution, where the ion concentration in the precursor solution is 0.5-2 mol / L (e.g., 1 mol / L), and after drying at 60-100°C (e.g., 80-90°C) for 2-5 hours (e.g., 3 hours) and calcining at 300-500°C (e.g., 400°C) for 3-6 hours (e.g., 5 hours), Co a Mn 1-a O x a catalyst, where a is in the range of 0.2-0.8 (e.g., 0.2, 0.33, 0.5, 0.67, and 0.8);

[0070] The 3D foam ceramic (e.g., cut 3D foam ceramic) is impregnated in the Co a Mn 1-a O x catalyst solution (e.g., Co a Mn 1-a O x catalyst is dissolved in a solution of ethanol and water) under ultrasonic conditions for 0.5-1 hour, and then dried at 60-100°C (e.g., 80-90°C) for 2-8 hours (e.g., 5 hours).

[0071] The 3D foam ceramic catalyst bed Co aMn 1-a O x The main active component of the catalyst is MnO x , Co a Mn 1-a O x The catalyst presents a loose porous structure, which is conducive to the adsorption of Co a Mn 1-a O x on the surface of the catalyst, and then the catalytic reaction occurs.

[0072] The sol-gel method can make the metal salt precursor highly dispersed at the molecular level, so that the doping element Co can enter the MnO x crystal phase, thereby destroying the crystal structure of MnO x , which is conducive to the generation of a large number of oxygen vacancies on the surface of MnO x . When the oxygen molecules pass through the surface of MnO x , the ozone molecules are combined with the oxygen vacancies through the terminal oxygen atoms, and the oxygen vacancies are 2e - electron donors, which transfer 2e - electrons to the O atoms of ozone, causing the O-O bond of ozone to break, releasing oxygen and generating O 2－ ; the other terminal oxygen atom of ozone is combined with O 2－ adsorption to cause electron transfer, causing the O-O bond of ozone to break, releasing oxygen and generating O2 2－ ; finally, O2 2－ is decomposed to release oxygen, and the oxygen vacancies are restored and participate in the next ozone decomposition cycle. Thus, the catalyst bed of the present application can remove ozone in air.

[0073] In an embodiment of the present application, an air purification and sterilization method is also provided. As Figure 2 shown, the air purification and sterilization method comprises:

[0074] providing a reverse corona plasma unit to form a plasma, the reverse corona plasma unit being provided with a corona electrode, an auxiliary electrode, a monolithic VOCs catalyst and a grounding electrode in sequence in the direction of airflow, the monolithic VOCs catalyst comprising a honeycomb-shaped substrate and a VOCs catalyst coated on the inner and outer surfaces of the honeycomb-shaped substrate, the inner and outer surfaces of the honeycomb-shaped substrate comprising whiskers, and the active components of the monolithic VOCs catalyst comprising Ce-BiVO4-TiO2 / Ag,

[0075] under the irradiation of visible light and / or ultraviolet light, treating VOCs and bacteria in air by Ce-BiVO4-TiO2 / Ag;

[0076] treating VOCs and bacteria in air using active ingredients in plasma.

[0077] In embodiments of the present application, the active components (e.g., free electrons, high-energy ions, active particles) in the Ce-BiVO4-TiO2 / Ag in the monolithic VOCs catalyst and in the plasma treat the VOCs and bacteria in the air, achieving purification and sterilization of the air. That is, the two effects are synergistically treated to purify the air and sterilize, greatly improving the treatment efficiency compared to each individual technology.

[0078] In embodiments of the present application, the active components (specifically, Ce, Bi, V, Ag) in the Ce-BiVO4-TiO2 / Ag enable the method of the present application to allow the catalyst to play a photocatalytic reaction role under the action of visible light radiation. Compared with the TiO2 catalyst that can only absorb ultraviolet light radiation, the method of the present application is more efficient and less costly.

[0079] In an example, the air purification and sterilization method further comprises: treating the VOCs and bacteria in the air by a combination of the first ultraviolet radiation and the second ultraviolet radiation.

[0080] Further, treating the VOCs by the combination of the ultraviolet radiation comprises:

[0081] The combination of the ultraviolet radiation causes the molecular bonds of the VOCs to break to generate active molecular fragments;

[0082] The combination of the ultraviolet radiation causes oxygen and water vapor molecules in the air to generate first reaction species, the first reaction species comprising active oxygen atoms and hydroxyl radicals;

[0083] The first reaction species causes the active molecular fragments to oxidize to generate small-molecule compounds.

[0084] Embodiments of the present application use a combination of ultraviolet radiation of different wavelengths, which can provide stronger radiation energy, helping to treat the VOCs into as small active molecular fragments as possible. The small active molecular fragments can be more easily oxidized, i.e., generate small-molecule compounds. Thus, using a combination of ultraviolet radiation of different wavelengths can more efficiently treat the VOCs in the air.

[0085] In an example, the air purification and sterilization method further comprises: connecting the electrostatic net to a negative direct-current high-voltage power supply, so that the dust in the air is charged when passing through the electrostatic net; and causing the charged dust to be adsorbed on the surface of the filter. Thus, embodiments of the present application can effectively remove dust in the air, improving air quality.

[0086] In an example, the air purification and sterilization method further comprises: treating ozone in the air through the catalyst bed. Thus, the embodiments of the present application can effectively remove ozone in the air, avoiding the harm of ozone emission to human beings.

[0087] The following will illustrate the processing efficiency of the method of the present application on VOCs in the air with a specific example.

[0088] 1. Preparation of the integrated VOCs catalyst

[0089] Ce-acetate, Bi-citrate, vanadyl oxalate and citric acid are formed into a sol in a mass ratio of 12:18:8:62, and a gel is formed after drying at 90°C, and an active powder Ce-BiVO4 is obtained after calcination at 350°C for 5 hours. The active powder Ce-BiVO4 is dissolved in water, and then mixed with TiO2 powder in a mass ratio of 18:82, and reacted under ultrasonic oscillation for 1 hour. After rotary drying at 80°C for 3 hours, Ce-BiVO4-TiO2 is obtained after calcination at 400°C for 5 hours. AgNO3 is mixed with Ce-BiVO4-TiO2 in a mass ratio of 15:85, glycerol is added to the mixed solution, and after rotary drying at 80°C for 3 hours, Ce-BiVO4-TiO2 / Ag catalyst is obtained after calcination at 400°C for 5 hours.

[0090] Boron trioxide, aluminum nitrate, anhydrous aluminum sulfate and anhydrous sodium sulfate are added to the cordierite honeycomb substrate, so that the mass ratio of the cordierite silicon honeycomb substrate: boron trioxide: aluminum nitrate: anhydrous aluminum sulfate: anhydrous sodium sulfate is 30:15:15:20:15, and the cordierite honeycomb substrate is at least partially embedded, preferably fully embedded, by boron trioxide, aluminum nitrate, anhydrous aluminum sulfate and anhydrous sodium sulfate. The mixture is placed in a muffle furnace and calcined at 1000°C for 6 hours, and naturally cooled to room temperature. A dense aluminum borate whisker is formed on the surface of the cordierite honeycomb substrate.

[0091] The Ce-BiVO4-TiO2 / Ag catalyst powder is mixed with sodium carboxymethyl cellulose, silica sol and water in a mass ratio of 25:28:12:35 to obtain a catalyst slurry. The catalyst slurry is coated on the cordierite honeycomb substrate with the surface-grown aluminum borate whisker on a vacuum coating machine. The coated material is dried in a drying box at 100°C for 2 hours, and then calcined in a muffle furnace at 450°C for 6 hours to obtain the integrated VOCs catalyst of the present application.

[0092] 2. Processing VOCs

[0093] The air purification device of the present application is used for processing.

[0094] A VOCs simulation gas is provided, which includes 100 ppm formaldehyde, 100 ppm toluene, and 100 ppm styrene. The three gases are precisely controlled by mass flow meters to ensure that the flow rates of the three gases are the same, and the VOCs concentration is 300 ppm. After being mixed in a mixing tank, the gas is introduced into a reaction device, and air is selected as the carrier gas. The mixed gas is directly introduced into the reaction device. The plasma generation intensity of the reverse corona plasma unit is controlled by controlling the negative high-voltage DC power supply connected to the corona electrode. The VOCs concentration is detected in real time by connecting an online gas chromatograph to the gas outlet end of the reverse corona plasma unit. The negative high-voltage DC voltage intensity of the reverse corona plasma connected to the corona electrode is set to 6 kV, 8 kV, 10 kV, 12 kV, 14 kV, and 16 kV in sequence. The purification efficiency of the embodiment of the present application is calculated by using the following formula:

[0095]

[0096] In addition, a comparative example is provided. In the comparative example, a catalyst slurry is not coated on the cordierite honeycomb substrate on which whiskers grow, and the remaining conditions are the same as those of the embodiment of the present application.

[0097] Table 1 shows the purification effect of the embodiment of the present application and the comparative example. According to Table 1, the purification efficiency of the embodiment of the present application for VOCs is as high as 96%, which achieves a very high purification efficiency.

[0098] Table 1

[0099]

[0100] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An air purification device comprising, in sequence in the direction of air flow, an air inlet, a reverse corona plasma unit, and an air outlet, wherein the reverse corona plasma unit comprising, in sequence in the direction of air flow, a corona electrode; an auxiliary electrode; a monolithic VOCs catalyst comprising a honeycomb substrate and a VOCs catalyst coated on the inner and outer surfaces of the honeycomb substrate, the inner and outer surfaces of the honeycomb substrate comprising whiskers, the active component of the monolithic VOCs catalyst comprising Ce-BiVO4-TiO2 / Ag; and a grounding electrode; the air purification device further comprising a radiation unit between the air inlet and the reverse corona plasma unit, the radiation unit comprising at least one ultraviolet light source and at least one visible light source, the at least one ultraviolet light source and the at least one visible light source being located on a mounting plate; VOCs and bacteria in the air being treated by the Ce-BiVO4-TiO2 / Ag under irradiation of visible light and / or ultraviolet light; VOCs and bacteria in the air being treated by the active component in the plasma.

2. The air purification device of claim 1, wherein the method of preparing the monolithic VOCs catalyst comprises the following steps: providing a honeycomb substrate with whiskers grown on the surface; providing a Ce-BiVO4-TiO2 / Ag catalyst; mixing the Ce-BiVO4-TiO2 / Ag catalyst, sodium carboxymethyl cellulose, silica sol, and water in a first mass ratio to obtain a first reactant, coating the first reactant on the inner and outer surfaces of the honeycomb substrate with whiskers grown thereon, and performing a drying process and then calcining to obtain the monolithic VOCs catalyst, wherein the step of providing the Ce-BiVO4-TiO2 / Ag catalyst comprises: forming a sol from a cerium source, a bismuth source, a vanadium source, and citric acid in a second mass ratio, forming a gel after drying at 80-100°C, and calcining at 300-500°C for 3-8 hours to obtain an active powder Ce-BiVO4; mixing the active powder Ce-BiVO4 solution and TiO2 in a third mass ratio and reacting under ultrasonic conditions for 0.5-2 hours, drying at 60-100°C for 2-5 hours, and then calcining at 300-500°C for 3-8 hours to obtain Ce-BiVO4-TiO2. The silver source and the Ce-BiVO4-TiO2 are mixed according to the fourth mass ratio, a reducing agent is added to the mixed solution, and the mixture is dried at 60-100°C for 2-5 hours and then calcined at 300-500°C for 3-8 hours to obtain a Ce-BiVO4-TiO2 / Ag catalyst. In the calcination process, the Ag is reduced to nano-silver particles. + ​ 3. The air purification device of claim 2, wherein the first mass ratio is (20-30):(15-20):(10-15):(30-45); the cerium source comprises cerium acetate; the bismuth source comprises bismuth citrate; the vanadium source comprises vanadyl oxalate; the second mass ratio is (10-15):(15-20):(5-10):(60-70); the third mass ratio is (15-20):(80-85); the fourth mass ratio is (10-20):(80-90); the reducing agent is glycerol.

4. The air purification device of claim 3, wherein The corona electrode is powered by a negative high-voltage direct-current power supply, and is configured to ionize the gas near the corona electrode during discharging to generate a large number of negative charges, which can interact with the integrated VOCs catalyst to form a counter corona plasma. The corona electrode is made of a tungsten wire with a diameter of 2-6 mm. The auxiliary electrode is made of a tungsten wire with a diameter of 2-6 mm.

5. The air purification device according to any one of claims 1-4, wherein The air purification device further comprises a filter unit between the air inlet and the radiation unit, the filter unit comprising a main frame, a static web connected to the negative direct-current high-voltage power supply on the main frame, and a filter in the main frame, the filter being arranged downstream of the static web in the airflow direction.

6. The air purification device according to claim 5, wherein The main frame is a cuboid comprising a hollow portion at the lower part, and the filter is arranged in the hollow portion. The main frame comprises opposite first and second open sides, the first open side being closed by the static web, and the second open side being provided with at least one mounting rod for mounting the radiation unit, the at least one mounting rod being arranged perpendicular to the airflow direction.

7. The air purification device according to claim 6, wherein The filter is made of superfine glass fiber filter paper, nylon wire, and plastic frame injection molded in one piece. The superfine glass fiber filter paper has a moisture-proof coating on the outer surface. The filter has a V-shaped pleated paper structure.

8. The air purification device according to claim 7, wherein The air purification device further comprises a catalyst bed between the counter corona plasma unit and the air outlet, the catalyst bed comprising a 3D foam ceramic carrier and a manganese-cobalt bimetallic active component loaded on the surface of the 3D foam ceramic carrier.

9. The air purification device according to claim 8, wherein The catalyst bed is provided by the following steps: Mn(CH3COO)2.4H2O, Co(CH3COO)2.4H2O, anhydrous citric acid are mixed in a mass ratio of (15-20):(25-30):(50-60) to form a precursor solution, wherein the ion concentration in the precursor solution is 0.5-2 mol / L, and after drying at 60-100°C for 2-5 hours, the precursor is calcined at 300-500°C for 3-6 hours to obtain Co a Mn 1-a O x a catalyst, wherein a is in the range of 0.2-0.8; The 3D ceramic foam was impregnated in a Co a Mn 1-a O x under ultrasonic conditions for 0.5-1 hour, and then dried at 60-100°C for 2-8 hours.

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