CN113413835B

CN113413835B - Normal-pressure plasma fluidized bed device without inner electrode and application thereof

Info

Publication number: CN113413835B
Application number: CN202110671395.8A
Authority: CN
Inventors: 陈光良; 陈朝阳; 周云正; 吴科平
Original assignee: Hangzhou Yongqing Environmental Protection Technology Co ltd; Zhejiang Sci Tech University ZSTU
Current assignee: Hangzhou Yongqing Environmental Protection Technology Co ltd; Zhejiang Sci Tech University ZSTU
Priority date: 2021-06-17
Filing date: 2021-06-17
Publication date: 2022-10-21
Anticipated expiration: 2041-06-17
Also published as: CN113413835A

Abstract

The invention discloses a normal-pressure plasma fluidized bed device without an internal electrode and application thereof in powder modification. The normal pressure plasma fluidized bed device without the inner electrode comprises: the bed body is hollow, the bottom end of the bed body is provided with an air inlet, and the top of the bed body is provided with a feed inlet and an air outlet; the plasma jet preionization device comprises a discharge tube, a sleeve electrode and a high-voltage electrode, wherein the sleeve electrode is sleeved at the outer bottom of the discharge tube and is grounded; and the radio frequency induction coil is wound on the outer side wall of the bed body, is positioned between the gas outlet and the plasma jet flow preionization device, and is externally connected with a radio frequency power supply.

Description

Normal-pressure plasma fluidized bed device without inner electrode and application thereof

Technical Field

The invention relates to the field of plasmas, in particular to a normal-pressure plasma fluidized bed device without an internal electrode and application thereof.

Background

In recent years, fluidized beds are widely used in chemical production processes, and equipment and process are continuously improved. Fluidized beds are fluids that suspend a large number of solid particles in a moving fluid, such that the particles have certain apparent characteristics of the fluid. This state of flow-solid contact is referred to as solid fluidization, i.e. fluidized bed. The fluidized bed has the advantages of high efficiency, good adaptability, environmental protection and the like in the application of a combustion technology, a crushing technology, a drying technology and the like. The fluidized bed and the plasma are applied to material surface modification, so that the method is efficient and environment-friendly, and a large number of active particles such as ions, excited molecules, free radicals and the like act on the surface of a solid sample, so that original pollutants and impurities on the surface can be removed, and an etching effect and a grafted polar group are generated. Meanwhile, the surface of the sample is roughened by plasma modification, a plurality of nano depressions are formed, so that the specific surface area of the sample is increased, and the polar groups improve the wetting property of the solid surface. Meanwhile, the particles with the energy of 0-20 eV in the plasma can break most of chemical bonds with the bond energy of 0-10 eV on the surface of the solid polymer. The free radicals in the plasma will form a network cross-linking structure with these bonds, greatly activating the activity of the material surface. Bretagno adopts a method of combining a fluidized bed and low-pressure plasma to carry out surface modification on low-density polyethylene powder. Both nitrogen and ammonia plasma treatments increase the hydrophilicity of the surface treated powder. The modified powder surface is added with new functional groups such as carbon nitrogen, carbon oxygen and the like, and nitrogen plasma treatment can better dope nitrogen-containing functional groups than ammonia plasma; guangliang Chen designed a liquid electrode atmospheric pressure plasma fluidized bed and studied the discharge characteristics. The organosilicon polymer coated on the powder surface by the plasma fluidized bed greatly reduces the powder surface energy. The surface modification process changes the wettability of the powder from super-hydrophilicity to super-hydrophobicity, and the water contact angle of the surface of the modified powder is larger than 160 degrees. However, the central electrode in the plasma fluidized bed has influence on powder dynamics, and the high-voltage electrode can lead charged powder to be gathered, thereby influencing modification efficiency and limiting the wide-range application of the plasma fluidized bed. Therefore, there is an urgent need to develop a novel atmospheric pressure electrodeless high efficiency plasma fluidized bed to realize the high efficiency modification of the powder material.

Current heterogeneous photocatalytic processes use n-type semiconductors (e.g., tiO) ₂ ZnO, cdS, etc.) as a catalyst, which produces active factors under illumination to oxidize organic electron-losing species. Related studies have shown that almost all organic contaminants are presentCan be decomposed by heterogeneous photocatalytic oxidation. However, znO, cdS and the like are unstable and easy to cause optical corrosion in light, so that Zn appears in water ²⁺ 、Cd ²⁺ And (3) plasma. And TiO 2 ₂ The chemical property is very stable, non-toxic, cheap and easy to obtain, and the chemical property is attracted by a plurality of researchers in recent years. Meanwhile, the inorganic nano Ag has strong antibacterial property, and is a research hotspot in the field of antibacterial disinfection due to strong antibacterial activity, safe use, stable property and no drug resistance. However, a lot of researches show that the antibacterial activity of the inorganic Ag nano material is influenced by various factors such as the particle size, morphology and morphology of Ag nano particles, the dispersibility of the Ag nano particles, the properties of carrier materials and the like. Therefore, the preparation of inorganic Ag composite nano-materials with higher antibacterial activity becomes a key point and a difficult point of future research. If the high-activity nano Ag is firmly loaded on the commercial TiO ₂ The surface can effectively treat organic matters and bacteria and viruses in water or air, so the method has great potential in the field of wastewater and air purification. However, the robust formation of two nanoparticles into a composite catalyst still faces many challenges, directly affecting the stability of the composite catalyst.

Disclosure of Invention

Aiming at the technical problems and the defects in the field, the invention provides the normal-pressure plasma fluidized bed device without the inner electrode, the electrode does not exist in the bed body, the uniformity of a material modification space and a radio frequency discharge environment is improved, and the fluidized powder in the bed body is uniformly modified and has high efficiency.

An atmospheric pressure plasma fluidized bed device without an internal electrode, comprising:

the bed body is hollow, the bottom end of the bed body is provided with an air inlet, and the top of the bed body is provided with a feed inlet and an air outlet;

the plasma jet preionization device comprises a discharge tube, a sleeve electrode and a high-voltage electrode, wherein the sleeve electrode is sleeved at the outer bottom of the discharge tube and is grounded;

and the radio frequency induction coil is wound on the outer side wall of the bed body, is positioned between the gas outlet and the plasma jet flow preionization device, and is externally connected with a radio frequency power supply.

In the invention, rare gas can be introduced into the gas inlet and the jet flow gas inlet, and corresponding reactive gas can also be introduced according to specific modification requirements.

The invention adopts an external radio frequency coil combined with a 360-degree annular plasma jet preionization device, and the plasma jet preionization device simultaneously plays the functions of powder blowing stirring and preionization. In a preferred embodiment, the plasma jet preionization device (2) comprises 3 sets, and the included angle between every two sets is 120 degrees.

In a preferred embodiment, the air outlet is externally connected with a cyclone separator, and the bottom of the cyclone separator is provided with a dust storage bag.

In a preferred embodiment, the discharge tube is a quartz tube.

In a preferred embodiment, the sleeve electrode is a thin copper-clad tube with an inner diameter of 4-6 mm and a side wall thickness of 0.2-0.5 mm.

In a preferred embodiment, the bed body is a transparent quartz tube, the thickness of the side wall is 0.5-1 mm, and the inner diameter is 20-30 mm.

In a preferred embodiment, the feed inlet is connected with the feed hopper through a pipe with a valve.

In a preferred embodiment, the air inlet is funnel-shaped and is externally connected with an air source through an air inlet pipeline with an air flow meter.

In a preferred embodiment, a gas distributor is arranged in the bed body between the gas inlet and the plasma jet preionization device.

The invention also provides the application of the normal-pressure plasma fluidized bed device without the inner electrode in powder modification. The specific modification time can be adjusted according to the requirements and the physicochemical properties of the powder, and can be generally 5-20 min.

In a preferred example, the output voltage of the plasma jet power supply is more than 0V and not more than 30kV, and the frequency is 20-40 kHz;

the radio frequency power of the radio frequency power supply is larger than 0W and not larger than 2000W (namely 0-2000W is continuously adjustable), and the frequency is 13.56MHz. The two are combined to realize normal-pressure radio frequency discharge, and the fluidized powder in the bed body is uniformly modified.

The invention also provides a powder modification method, which adopts the normal-pressure plasma fluidized bed device without the internal electrode and comprises the following steps: adding the dried powder into a bed body, regulating and controlling the speed of fluidizing gas at a gas inlet and a jet gas outlet to enable the powder to be in a fluidized state, starting a plasma jet preionization device to preionize the fluidizing gas, regulating and controlling the radio frequency power of a radio frequency power supply to carry out normal-pressure radio frequency discharge, and modifying the powder. The optimal conditions can be selected mainly according to the commercialization degree of the discharge power supply, the optimal conditions for discharge, the optimal parameters for device modification and the lowest cost.

As a general inventive concept, the invention also provides a nano Ag/TiO material ₂ Composite catalyst, tiO ₂ On which nano Ag particles are loaded, and TiO ₂ P25 is used as a raw material and is obtained by modifying through the powder modification method, wherein the fluidizing gas is rare gas.

The nano Ag/TiO ₂ In the composite catalyst, the loading of the nano Ag particles can be as high as 30wt% (relative to the total mass of the catalyst). The loading capacity of the ultra-high Ag nano particles is attributed to that the titanium dioxide surface pollutants and impurities are removed by the normal-pressure radio frequency discharge of rare gases such as argon and the like, and meanwhile, the specific surface area is enlarged and the wettability is improved.

High activity particles in radio frequency plasma in TiO ₂ A plurality of nano-pits are formed on the surface, and the nano-Ag is just filled in and attached to the pits, so that the nano-Ag and the TiO are greatly enhanced ₂ Binding fastness of (2) to realize TiO ₂ Has the functions of sterilization, antivirus and organic matter degradation under visible light and ultraviolet rays, and has wider application in the field of photocatalysis.

The nano Ag/TiO ₂ The composite catalyst can effectively degrade organic matters in sewage and kill bacteria, viruses and microorganisms in the air.

The invention also provides the nano Ag/TiO ₂ Composite catalyst for sterilization and degradationApplication of organic matters (such as alkaline green and the like) in sewage.

Compared with the prior art, the invention has the main advantages that: according to the normal-pressure internal electrode-free plasma fluidized bed device, radio frequency discharge under normal pressure is realized through plasma jet preionization of normal-pressure dielectric barrier discharge, the problems of small modification space and non-uniform modification environment caused by traditional fluidized bed built-in electrodes are solved, and the problems of non-uniform and incomplete powder modification caused by adsorption and aggregation of charged powder generated by traditional fluidized bed built-in electrode discharge are solved. The normal-pressure plasma fluidized bed device without the inner electrode is used for modifying fluidized powder in the bed body, so that the specific surface area of the powder can be increased, the number of surface nano pits can be increased, the surface roughness can be improved, and the wettability can be improved. The modified powder is used as a carrier to load active nano particles, and the active nano particles can be firmly attached to the surface of the modified powder, so that the stability and the activity of the composite material are improved.

Drawings

FIG. 1 is a schematic structural view of an atmospheric pressure internal electrode-free plasma fluidized bed apparatus according to an embodiment, in which:

1. bed body 2. Plasma jet preionization device

3. Jet flow air inlet 4. Air inlet

5. Gas distributor 6 gas flowmeter

7. Air inlet pipeline 8 air source

9. Radio frequency induction coil 10, radio frequency power supply

11. An air outlet 12. A cyclone separator

13. A dust storage bag 14, a feed inlet 15 and a feed hopper;

FIGS. 2 (a) to (d) are respectively a SEM photograph of P25 in example, and TiO pretreated by an atmospheric pressure plasma fluidized bed apparatus without an internal electrode ₂ SEM photograph of (1) and Ag/TiO directly prepared from P25 in comparative example 1 ₂ SEM photograph of (silicon nitride) and example of TiO pretreated by atmospheric pressure plasma fluidized bed device without internal electrode ₂ Prepared Ag/TiO ₂ SEM photograph of (a);

FIGS. 3 (a) to (d) are each successivelyIs a TEM photograph of P25 in example, tiO pretreated by an atmospheric pressure plasma fluidized bed device without an internal electrode ₂ TEM image of (B) and Ag/TiO directly prepared from P25 in comparative example 1 ₂ TEM photograph of and example Normal pressure TiO pretreated without internal electrode plasma fluidized bed device ₂ Prepared Ag/TiO ₂ A TEM photograph of;

FIG. 4 is a plasma fluidized bed modified TiO with an internal electrode as disclosed in comparative example 2 using CN100376319C ₂ SEM photograph of (a);

FIG. 5 shows Ag/TiO samples of comparative example 1 without catalyst (a) in test example 1 ₂ (b) Ag/TiO of examples ₂ (c) Photo of killing mould;

FIG. 6 is a graph of the degradation rate of various components of the alkaline green solution for a simulated printing wastewater solution of test example 2.

Detailed Description

The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer.

Examples

The atmospheric pressure plasma fluidized bed device without an internal electrode of the present embodiment is shown in fig. 1, and comprises a hollow bed body 1. The bed body 1 is a transparent quartz tube, the side wall thickness is 0.5 mm, and the inner diameter is 30 mm. 3 sets of plasma jet preionization devices 2 are uniformly distributed along the circumferential direction of the bottom of the bed body 1, and the included angle between every two sets is 120 degrees.

The bottom of the bed body 1 is provided with an air inlet 4, the air inlet 4 is funnel-shaped, and is externally connected with an air source (such as nitrogen, argon and the like) 8 through an air inlet pipeline 7 with an air flow meter 6. A gas distributor 5 is arranged in the bed body 1 between the gas inlet 4 and the plasma jet preionization device 2.

The top end of the bed body 1 is provided with a feed inlet 14, and the feed inlet 14 is externally connected with a feed hopper 15 through a pipeline with a valve.

The side of the top of the bed body 1 is provided with an air outlet 11, the air outlet 11 is externally connected with a cyclone separator 12, and the bottom of the cyclone separator 12 is provided with a dust storage bag 13.

Plasma jet preionization device 2 is ordinary pressure dielectric barrier discharge device, establish including discharge tube, cover discharge tube outer bottom and grounded sleeve pipe electrode with locate high voltage electrode in the discharge tube, sleeve pipe electrode, high voltage electrode are external plasma power supply (HV)'s low pressure output end and high voltage output end respectively, be equipped with efflux air inlet 3 on the discharge tube and towards the inside efflux gas outlet of the bed body 1. The discharge tube is a quartz tube. The sleeve electrode is a thin copper sheet tube with an inner diameter of 6 mm and a side wall thickness of 0.5 mm.

A radio frequency induction coil 9 is wound on the outer side wall of the bed body 1, is positioned between the air outlet 11 and the plasma jet preionization device 2, and is externally connected with a radio frequency power supply (RF) 10.

P25 (a commercial titanium dioxide, whose SEM and TEM photographs are shown in fig. 2 (a) and 3 (a), respectively, and have a diameter of about 50nm and a smooth surface) was modified using the atmospheric pressure internal electrode-free plasma fluidized bed apparatus, which specifically includes: adding 1g of dry P25 into the bed body 1, regulating and controlling the speed of the fluidizing gas at the gas inlet 4 and the jet gas outlet to enable the P25 to be in a fluidized state, starting the plasma jet preionization device 2 to preionize the fluidizing gas, regulating and controlling the radio frequency power of the radio frequency power supply 10 to enable the preionized fluidizing gas to carry out normal-pressure radio frequency discharge in a radio frequency region (namely the internal space of the bed body 1 corresponding to the radio frequency induction coil 9), modifying the fluidized P25 for 15min, and obtaining the pretreated TiO ₂ SEM photographs and TEM photographs are shown in FIG. 2 (b) and FIG. 3 (b), respectively, and ordinary pressure radio frequency discharge treatment is performed to smooth the original TiO ₂ The surface is roughened by many depressions and pores, and the surface is made of TiO ₂ The particles become smaller in size, about 20nm in diameter, and their specific surface area is significantly increased. The fluidizing gas is argon, the output voltage of the plasma power supply is 7kV, the frequency is 11kHz, the radio-frequency power of the radio-frequency power supply 10 is 1500W, and the frequency is 13.56MHz.

Using the pretreated TiO ₂ Preparation of nano Ag/TiO ₂ Composite catalyst:

(1) 1g of silver nitrate powder was dissolved in 100mL of deionized water at room temperature,stirring uniformly for 30min until the powder is completely dissolved in water. Then slowly dripping 25wt% ammonia water solution into the solution to generate brown precipitate, and continuously and slowly dripping the ammonia water solution until the generated brown precipitate is completely dissolved to obtain transparent and clear [ Ag (NH) ₃ ) ₂ ]And (4) OH solution.

(2) Pre-treated 1g TiO ₂ Adding to colorless [ Ag (NH) ₃ ) ₂ ]And (4) carrying out ultrasonic dispersion in the OH solution to dissolve the OH solution to obtain a white colloidal solution.

(3) 100ml of 0.5 mol.L ^-1 The glucose solution was added to the white colloidal solution and stirring was continued for 2h, before the glucose solution was added to the mixed solution, the solution remained clear and transparent, and after 2h the solution turned cloudy and finally black as the glucose solution was added and the stirring time increased.

(4) And averagely introducing the mixed solution into a 50mL centrifuge tube, symmetrically placing the centrifuge tube into a centrifuge for centrifugation, respectively adding ethanol and deionized water into the centrifuge tube for cleaning, and centrifuging again, wherein the steps are repeated for at least three times.

(5) The black powder in the centrifuge tube was spread on the surface of aluminum foil and dried in an oven at 60 ℃ for 12h. Dried Ag/TiO ₂ Grinding the catalyst into powder particles by using a mortar to finally obtain the nano Ag/TiO ₂ The SEM and TEM photographs of the composite catalyst are shown in FIG. 2 (d) and FIG. 3 (d), respectively, and it is clearly seen that the nano-silver is uniformly dispersed and is mixed with TiO ₂ The combination is firm. This indicates that the nano-silver is successfully and uniformly fixed to the TiO by the assistance of the atmospheric radio frequency discharge ₂ Surface to obtain Ag/TiO ₂ A nanocomposite catalyst.

Comparative example 1

Preparation of Nano Ag/TiO with examples ₂ Compared with the process of composite catalyst, the difference is only that the P25 is directly used to replace the pretreated TiO in the step (2) ₂ As a carrier, the conditions of the other steps are the same, and the obtained nano Ag/TiO ₂ SEM and TEM photographs of the composite catalyst are shown in FIGS. 2 (c) and 3 (c), respectively, and it is clear that TiO treated by the injection frequency discharge treatment is often observed as compared with FIGS. 2 (d) and 3 (d) ₂ Prepared byNano Ag/TiO ₂ In the composite catalyst, the dispersibility and compatibility of Ag are better, which shows that TiO is subjected to surface modification assisted by normal-pressure radio-frequency discharge ₂ The surface depressions contribute to uniform Ag adhesion.

Comparative example 2

The modified TiO is obtained by adopting P25 used in a modified example of the plasma fluidized bed containing the inner electrode disclosed in CN100376319C, wherein the output voltage of a plasma power supply is 7kV, and the frequency is 11kHz ₂ The SEM photograph is shown in FIG. 4, which compares the example with the modified TiO of the atmospheric pressure plasma fluidized bed without the inner electrode ₂ Plasma fluidized bed treated TiO with internal electrode ₂ Uneven distribution and massive agglomeration. The specific reason is that the fluidized bed described in CN100376319C contains an internal electrode, the powder processing space is reduced, and the powder is blocked by the internal electrode so that the powder cannot be uniformly distributed in the bed body. In addition, due to the action of the electric field, part of charged powder particles can be adsorbed on the inner electrode or the wall of the discharge tube, so that the discharge efficiency is seriously influenced, and the surface treatment uniformity of the powder is obviously reduced. The plasma fluidized bed has no inner electrode, the plasma jet preionization device arranged at the bottom end of the bed body is combined with the radio frequency induction coil on the outer side wall of the bed body, the space in the bed body is not occupied, the ionizable region is greatly released, and the problem of powder adsorption and agglomeration is completely avoided.

Test example 1

FIG. 5 shows the example of the pre-treated TiO in the atmospheric pressure plasma fluidized bed without inner electrode ₂ Prepared Ag/TiO ₂ Photograph of the nano composite catalyst against fungus. The number of colonies cultured on the medium was about 110 (FIG. 5 (a)). Dispersion of unmodified Ag/TiO from comparative example 1 in the Medium under identical culture conditions ₂ (FIG. 5 (b)) modified Ag/TiO of examples ₂ FIG. 5 (c) shows that the modified Ag/TiO of examples ₂ The catalyst has better sterilization effect, which shows that the TiO is pretreated by the normal pressure radio frequency discharge ₂ The bactericidal performance of the composite catalyst can be obviously improved.

Test example 2

Ag/TiO ₂ Catalyst for degrading alkaline green under assistance of potassium hydrogen Persulfate (PMS)(BG 1) solution simulation of printing and dyeing wastewater solution: preparing (24 mg/L) alkaline green solution, measuring 200ml alkaline green solution in a 250ml beaker, and adding 100mg Ag/TiO ₂ Adding equal amount of potassium hydrogen persulfate into the catalyst, transferring into a light reaction instrument (350W, xenon lamp) for visible light catalytic degradation reaction, sampling with an injector with a filter device every 3min, testing absorbance with an ultraviolet spectrophotometer, and analyzing Ag/TiO ₂ The wastewater degradation efficiency of the catalyst.

As shown in fig. 6, a graph of the degradation rate of the alkaline green solution versus the simulated printing wastewater solution with different components is shown, blank. When only PMS is added, almost no degradation effect on BG1 solution is found after 30min of visible light action, and the catalytic degradation effect of PMS on dye can be neglected. After PMS and Ag nanoparticles are added, only 5% of BG1 is degraded after 30min of visible light action, and the result proves that certain active group ions for catalytic degradation cannot be generated between the Ag nanoparticles and the PMS, and the degradation effect on a BG1 solution is almost negligible. Control blank, PMS addition and commercial TiO untreated with plasma fluidized bed without internal electrode ₂ Then, 60% of BG1 was catalytically degraded by visible light for 30min, indicating PMS and TiO ₂ The interaction between them generates active radical ions which are favorable for catalytic degradation. With TiO ₂ Compared with the system, when the BG1 solution is added with PMS and Ag/TiO treated by the plasma fluidized bed without the inner electrode ₂ Then, after 30min of visible light, the degradation efficiency is obviously improved, about 99% of BG1 is degraded, and the Ag nanoparticles and TiO are proved ₂ The nano-particle composite heterostructure can effectively promote TiO ₂ More active radical ions are generated for photocatalytic degradation of BG1. Since Ag has a very good photosensitivity, it is combined with TiO ₂ Prepared into a heterostructure, and inhibits TiO through the mutual synergistic effect between the two ₂ Recombination of the photoproduction electron-hole pairs accelerates electron transfer, improves the visible light absorption efficiency of the photoproduction electron-hole pairs, and further improves the catalytic degradation efficiency of the photoproduction electron-hole pairs. In addition, tiO modification with the DBD fluidized bed (with internal electrode) of comparative example 2 ₂ Ag/TiO prepared by same silver mirror reaction ₂ As a contrast, it dyesThe degradation rate of the material degradation for 30min is only 89%, which is obviously less than the degradation efficiency of the radio frequency plasma fluidized bed modified catalyst of the embodiment which is nearly 100%, and the disadvantage is obvious.

Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention as defined by the appended claims.

Claims

1. A P25 powder modification method is characterized in that a normal-pressure plasma fluidized bed device without an internal electrode is adopted, and the normal-pressure plasma fluidized bed device without the internal electrode comprises the following steps:

the bed comprises a hollow bed body (1), wherein the bottom end of the hollow bed body is provided with an air inlet (4), and the top of the hollow bed body is provided with a feed inlet (14) and an air outlet (11);

the plasma jet preionization device comprises 3 sets of plasma jet preionization devices (2) which are circumferentially and uniformly distributed along the bottom of a bed body (1) and have an included angle of 120 degrees between every two sets, wherein each plasma jet preionization device (2) is a normal-pressure dielectric barrier discharge device and comprises a discharge tube, a sleeve electrode which is sleeved at the outer bottom of the discharge tube and is grounded, and a high-voltage electrode which is arranged in the discharge tube, the sleeve electrode and the high-voltage electrode are respectively externally connected with a low-voltage output end and a high-voltage output end of a plasma power supply, and the discharge tube is provided with a jet air inlet (3) and a jet air outlet which faces the interior of the bed body (1);

a radio frequency induction coil (9) wound on the outer side wall of the bed body (1) is positioned between the gas outlet (11) and the plasma jet preionization device (2) and is externally connected with a radio frequency power supply (10);

the P25 powder modification method comprises the following steps: adding dried P25 powder with smooth surface and 50nm diameter into a bed body (1), regulating and controlling the velocity of fluidizing gas at an air inlet (4) and a jet flow air outlet to enable the P25 powder to be in a fluidized state, starting a plasma jet flow pre-ionization device (2) to pre-ionize the fluidizing gas, regulating and controlling the radio frequency power of a radio frequency power supply (10) to perform normal-pressure radio frequency discharge, and modifying the P25 powder to obtain modified P25 powder with rough surface and 20nm diameter;

the output voltage of the plasma power supply is 7kV, the frequency is 11kHz, and the radio frequency power of the radio frequency power supply (10) is 1500W.

2. The method for modifying P25 powder according to claim 1, wherein the gas outlet (11) is externally connected with a cyclone separator (12), and a dust containing bag (13) is arranged at the bottom of the cyclone separator (12).

3. The method for modifying P25 powder according to claim 1, wherein the discharge tube is a quartz tube;

the sleeve electrode is a copper sheet thin tube, the inner diameter is 4-6 mm, and the side wall thickness is 0.2-0.5 mm;

the bed body (1) is a transparent quartz tube, the thickness of the side wall is 0.5-1 mm, and the inner diameter is 20-30 mm.

4. The P25 powder modification method according to claim 1, wherein the feed inlet (14) is externally connected with a feed hopper (15) through a pipeline with a valve;

the air inlet (4) is funnel-shaped and is externally connected with an air source (8) through an air inlet pipeline (7) with an air flowmeter (6);

a gas distributor (5) is arranged between the gas inlet (4) and the plasma jet flow preionization device (2) in the bed body (1).

5. The method for modifying P25 powder according to claim 1, wherein the frequency of the radio frequency power supply (10) is 13.56MHz.

6. A modified P25 powder obtained by modification according to the P25 powder modification method of any one of claims 1 to 5.

7. Nano Ag/TiO ₂ Composite catalyst, characterized in that TiO ₂ On which nano Ag particles are loaded, and TiO ₂ The P25 powder modification method according to any one of claims 1 to 5, wherein the fluidizing gas is a rare gas.

8. Nano Ag/TiO according to claim 7 ₂ The composite catalyst is applied to sterilization and degradation of organic matters in sewage.