CN101481156B - Pressurized light-catalyzed reaction system - Google Patents

Abstract

The invention provides a pressurized photocatalytic reaction system. The photocatalytic system uses semiconductor materials such as titanium dioxide as photocatalysts and ultraviolet lamps as light sources. Operates in an oxygen atmosphere. The beneficial effects of the present invention are mainly reflected in that the oxidative degradation efficiency of the photocatalytic system of the present invention is much higher than that without additional oxygen pressure or nitrogen pressure, the energy consumption is low, the catalyst is easy to recycle and reuse, and the industrial application prospect is good.

Description

A pressurized photocatalytic reaction system

(1) Technical field

The invention relates to a pressurized photocatalytic reaction system, in particular to a photocatalytic reaction system with high-pressure pure oxygen as an intensified condition.

(2) Background technology

Photocatalytic reaction is a kind of photochemical reaction process discovered in the 1970s. Titanium dioxide powder generates electron-hole pairs under the irradiation of ultraviolet light. This high energy electron-hole pair catalyzes the conversion of solvent water into hydroxyl radicals and initiates other chemical reactions in solution. Subsequent studies have found that in addition to titanium dioxide, there are various semiconductor materials such as zinc oxide and tin dioxide that can produce photoinduced electron-hole pair effects, which expands the research scope of photocatalytic reactions.

The current prevailing theory holds that both electrons and holes converted from light energy have catalytic ability. Holes are transferred to water molecules to generate hydroxyl radicals, while electrons are combined with dissolved oxygen, and after a series of free radical reactions, they are finally transformed into hydroxyl radicals.

This process can also be represented by the following equation:

h ⁺ +OH ^- → OH

h ⁺ +H ₂ O→ OH+H ⁺

e ^- +O _2(ads) → O _2(ads) ^-

The combination of surface oxygen and photogenerated electrons avoids the recombination of holes and photogenerated electrons, and O ₂ ^- will regenerate free radicals OH with H ⁺ during the reaction process:

·O _2(ads) ^- +H ⁺ →HO ₂ ·

2HO ₂ →O ₂ +H ₂ O ₂

H ₂ O ₂ +O _2(ads) ^- → OH+OH ^- +O ₂

Hydroxyl radicals have a high oxidizing ability, and can oxidize and decompose various organic compounds in the water phase almost non-selectively. The process can be carried out for a long enough time, and even the organic matter can be completely mineralized.

In view of the advantages of mild conditions, simple operation and control, simple reaction equipment, no secondary pollution, and easy preparation of catalysts, photocatalytic reactions have been extensively studied in laboratories in recent years. However, photocatalysis has the defects of low photon efficiency, high energy consumption, and the difficulty of recycling and reusing catalysts, which greatly limits the development of industrial applications, resulting in no examples of industrial applications in this field.

(3) Contents of the invention

The object of the present invention is to provide a pressurized photocatalytic system with high photon quantum efficiency, low energy consumption and easy recycling of the catalyst.

The technical scheme adopted in the present invention is:

A pressurized photocatalytic reaction system, the photocatalytic system uses a semiconductor photocatalyst as a catalyst and an ultraviolet lamp as a light source, and is characterized in that the photocatalytic system operates in a pure oxygen atmosphere of 1 to 5 atmospheres. The 1-5 atmospheric pressure refers to the additional oxygen pressure, that is, the relative pressure to the atmospheric pressure (absolute pressure 1at), and when the normal pressure oxygen pressure is applied, it is expressed as 0at. The pressures mentioned hereafter are all relative pressures.

The semiconductor photocatalyst is a photocatalyst commonly used in photocatalytic reactions in the field, such as semiconductor powders such as titanium dioxide, zinc oxide, and tin dioxide, but is not limited to the above three types.

The pressurized photocatalytic system mainly includes a high-pressure oxygen source, a photocatalytic reactor and a membrane separation device. The oxygen in the high-pressure oxygen source and the wastewater to be treated are input into the photocatalytic reactor at the same time, and are carried out under the irradiation of an ultraviolet lamp. Photocatalytic degradation reaction, the mixed liquid after the reaction passes through the membrane separation device to recover the semiconductor photocatalyst, and the waste liquid is depressurized and discharged.

In order to achieve the effect of complete gas-liquid mixing, the oxygen and the waste water to be treated are combined through a Venturi tube and then passed into the photocatalytic reactor.

Preferably, the photocatalytic system is carried out in an oxygen atmosphere of 5 atmospheres, and the oxygen is pressed into the Venturi tube through an air pump, and after being merged with the wastewater to be treated, it is input into the photocatalytic reactor, and the photocatalytic reaction is carried out under the irradiation of an ultraviolet lamp. Catalytic degradation reaction, the mixed liquid after the reaction passes through the membrane separation device to recover the semiconductor photocatalyst, and the waste liquid is depressurized and discharged.

The waste water to be treated can be all waste water suitable for photocatalytic reaction systems in this field. The present invention takes reactive brilliant red X-3B or reactive brilliant blue X-BR waste water and other implementation objects as examples, and it cannot be used as a reference for this invention. The limitation of the invention, because although the organic compounds that need to be oxidized and decomposed will be different in different wastewater, but in view of the principle is consistent, those skilled in the art have reason to believe that the photocatalytic reaction system of the present invention can be applied to all wastewater containing organic compounds Oxidative decomposition.

The reaction system diagram of the present invention is shown in Fig. 1:

The reaction system is mainly composed of a high-pressure gas source, a photocatalytic reactor, and a membrane separation system. The reaction system is continuous. Raw water is continuously injected into the system from the water tank through a high-pressure pump. After photocatalytic degradation, it is filtered out through the membrane module, while the photodegradation catalyst is trapped in the system by the membrane module for recycling.

The high-pressure air source can be a gas cylinder or an air pump, which injects high-pressure pure oxygen into the system to increase the dissolved oxygen content in the water. When the gas enters the system, it passes through a Venturi device to achieve the effect of complete gas-liquid mixing.

The main body of the photocatalytic reactor is a high-voltage resistant quartz sleeve. The aqueous solution mixed with the photocatalyst flows through the quartz tube. The ultraviolet light is generated by the ultraviolet light source, and the photocatalyst is irradiated to generate hydroxyl radicals, which are transmitted to the dissolved oxygen in the solution. Oxidizes organic matter in solution. The quartz tube is covered with a metal protective jacket to avoid the potential danger of quartz tube rupture, and can be passed into the medium to heat or cool the reactor.

The membrane separation system is used to intercept the photocatalyst in the solution, and the filtration methods can be microfiltration and ultrafiltration. The membrane module uses the high pressure in the system to push the solution out of the reaction system, while the catalyst is trapped in the reaction system for recycling. Excess oxygen in the solution and CO ₂ gas produced by the oxidation of organic matter pass through the membrane module along with the solution, and are discharged out of the system together, and released at reduced pressure.

At present, researchers are aware that oxygen should have a promoting effect in the photocatalytic process, but the general understanding of dissolved oxygen in the field of photocatalysis in the prior art generally belongs to a kind of loose and neglected attention. The research of the present invention reveals that the photocatalytic There is a positive correlation between dissolved oxygen concentration and photocatalytic efficiency in the catalytic process, and a new titanium dioxide photocatalytic system is designed to overcome the low photon efficiency, high energy consumption and catalyst The defect that it is difficult to recycle and reuse is conducive to the development of its industrial application. The pressurized photocatalytic reaction system of the present invention is applicable to any photocatalytic reaction using semiconductor materials as photocatalysts, such as photocatalytic degradation of dyes by titanium dioxide, photocatalytic degradation of pesticides or volatile organic pollutants by tin dioxide.

The beneficial effects of the present invention are mainly reflected in that the oxidative degradation efficiency of the photocatalytic system of the present invention is much higher than that of atmospheric oxygen pressure or nitrogen pressure, the energy consumption is low, the catalyst is easy to recycle and reuse, and the industrial application prospect is good.

(4) Description of drawings

Fig. 1 is the schematic diagram of photocatalytic system of the present invention;

Fig. 2 is the photolysis efficiency curve of titanium dioxide photocatalyst to reactive brilliant red X-3B under different oxygen pressures;

Fig. 3 is the photolysis efficiency curve of titanium dioxide photocatalyst to reactive brilliant blue X-BR under different oxygen pressures;

Fig. 4 is the photolysis efficiency graph of zinc oxide photocatalyst to aniline under different oxygen pressures;

Fig. 5 detects the pressurized photolysis curve of reactive brilliant red under 505nm titanium dioxide photocatalyst 5at oxygen and nitrogen pressure;

Fig. 6 is the pressurized photolysis curve figure that detects titanium dioxide photocatalyst 5at oxygen and nitrogen pressure under the pressure photolysis of reactive bright red under 278nm;

Fig. 7 is the graph of the photolysis efficiency of zinc oxide photocatalyst to phenol under different oxygen pressures;

Fig. 8 is a curve diagram of the photolysis efficiency of the herbicide R-2,4-D by the tin dioxide photocatalyst under different oxygen pressures.

(5) Specific implementation methods

The present invention is further described below in conjunction with specific embodiment, but protection scope of the present invention is not limited thereto:

The schematic diagram of the pressurized photocatalytic system is shown in Figure 1; 1 is the photocatalytic reactor, 2 is the high-pressure oxygen source, 3 is the membrane separation device, 4 is the ultraviolet lamp, 5 is the high-pressure quartz tube sleeve, 6 is the cooling jacket, 7 8 is a venturi tube, 9 is a high-pressure water inlet pump, 10 is a high-pressure circulation pump, 11 is a liquid flow meter, and the photocatalyst is directly put into the reactor.

Embodiment 1: the pressure photolysis of reactive brilliant red

Reactive Brilliant Red X-3B (Hangzhou Anlongda Chemical Co., Ltd.) was formulated into 100mg/L simulated wastewater, and entered into the pressurized photocatalytic system shown in Figure 1 for treatment, using titanium dioxide as a catalyst (amount of 500mg/L), The influence of oxygen pressure on the photolysis decolorization effect was detected at a wavelength of 505nm, and the experimental results are shown in Figure 2. From the experimental results, it can be seen that after photolysis treatment for 60 minutes, the photolysis efficiency under 5at pressure reached 72.97%, which was 27% higher than the decolorization rate of 57.38% by normal pressure oxygen (0at).

Embodiment 2: the pressurized photolysis of reactive brilliant blue X-BR

Reactive Brilliant Blue X-BR (Hangzhou Anlongda Chemical Co., Ltd.) was formulated into 100mg/L simulated wastewater, and entered into the pressurized photocatalytic system shown in Figure 1 for treatment, with titanium dioxide as the photocatalyst (amount of 500mg/L) , at a wavelength of 598nm to detect the effect of oxygen pressure on the photolysis decolorization effect, the experimental results are shown in Figure 3. It can be seen from the experimental results that after photolysis treatment for 60 minutes, the photolysis efficiency under 5at pressure has reached 37.65%, which is 140% higher than the decolorization rate of 15.6% by normal pressure oxygen (0at).

Embodiment 3: the pressurized photolysis of aniline

Aniline is formulated into simulated wastewater with 100 mg/L of aniline, which is then processed in a pressurized photocatalytic system as shown in Figure 1. Zinc oxide is used as a photocatalyst (amount of 3000 mg/L), and the effect of oxygen pressure on photolysis and decolorization is detected at a wavelength of 545 nm. The experimental results are shown in Figure 4. It can be seen from the experimental results that after photolysis treatment for 60 minutes, the photolysis efficiency under 5at pressure reached 31.12%, which was 39% higher than the photolysis efficiency of 22.35% under 1at oxygen pressure.

Embodiment 4: the pressure photolysis of reactive brilliant red

Reactive Brilliant Red X-3B was formulated into 100mg/L simulated wastewater, which was treated in a pressurized photocatalytic system as shown in Figure 1. Titanium dioxide was used as a photocatalyst (amount of 500mg/L), and oxygen and nitrogen were respectively introduced into the comparison test , the influence of gas pressure on the photolysis decolorization effect was detected at wavelengths of 505nm and 278nm respectively, and the experimental results are shown in Figure 5 and Figure 6. As can be seen from the experimental results, after photolysis treatment 60min, detect under 505nm, the photolysis efficiency under 5at oxygen pressure has reached 72.97%, has improved 126% (Fig. 5) than the decolorization rate of 32.30% under 5at nitrogen pressure; Detected at 278nm, the photolysis efficiency under 5at oxygen pressure reached 46.27%, which was 1154% higher than the 3.69% decolorization rate under 5at nitrogen pressure (Fig. 6). The experiment proves that increasing the pressure to increase the concentration of dissolved oxygen is the fundamental reason for the improvement of the photolysis effect, and only increasing the pressure of the system is ineffective.

Embodiment 5: the pressure photolysis of phenol

Phenol was formulated into simulated wastewater with phenol 50mg/L, and entered into the pressurized photocatalytic system shown in Figure 1 for treatment, using zinc oxide as the photocatalyst (amount of 3000mg/L), and detecting the effect of oxygen pressure on photolysis and decolorization at a wavelength of 510nm The experimental results are shown in Figure 7. It can be seen from the experimental results that after photolysis treatment for 60 minutes, the photolysis efficiency under 5at pressure reached 25.53%, which was 80% higher than the photolysis efficiency of 14.17% under 1at oxygen pressure.

Example 6: Pressurized photolysis of herbicide R-2,4-D

The herbicide R-2, 4-D is prepared into 20mg/L simulated wastewater, and enters the pressurized photocatalytic system shown in Fig. The influence of oxygen pressure on the photolysis decolorization effect was detected, and the experimental results are shown in Figure 8. It can be seen from the experimental results that after photolysis treatment for 60 minutes, the photolysis efficiency under 5at pressure reached 46.22%, which was 40% higher than the photolysis efficiency of 33.12% under 1at oxygen pressure.

Claims (5)

1. pressurized light-catalyzed reaction system, described pressurized light-catalyzed reaction system is a degradation catalyst with the semiconductor light-catalyst, is light source with the ultraviolet lamp, it is characterized in that: described photocatalytic system is moved in 1～5 atmospheric oxygen atmosphere.

2. pressurized light-catalyzed reaction system as claimed in claim 1 is characterized in that described semiconductor light-catalyst is the powder of titanium dioxide, zinc oxide or tindioxide.

3. pressurized light-catalyzed reaction system as claimed in claim 1 or 2, it is characterized in that: described pressurized light-catalyzed system mainly comprises hyperbaric oxygen source of the gas, photo catalysis reactor and membrane separation unit, oxygen in the described hyperbaric oxygen source of the gas is imported in the photo catalysis reactor with the waste water that needs to handle simultaneously, under ultra violet lamp, carry out the photocatalytic degradation reaction, after reacted mixed solution reclaims semiconductor light-catalyst through membrane separation unit, waste liquid step-down discharging.

4. pressurized light-catalyzed reaction system as claimed in claim 3 is characterized in that: described oxygen feeds photo catalysis reactor with the waste water that needs to handle after the Venturi manifold closes.

5. pressurized light-catalyzed reaction system as claimed in claim 3, it is characterized in that: described photocatalytic system is carried out in 5 atmospheric oxygen atmosphere, described oxygen is pressed into Venturi tube, converges in the back input photo catalysis reactor with the waste water that needs to handle by air pump, under ultra violet lamp, carry out the photocatalytic degradation reaction, after reacted mixed solution reclaims semiconductor light-catalyst through membrane separation unit, waste liquid step-down discharging.

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