A detection system for hydroxyl radicals generated by gas phase photocatalytic reaction

Abstract

The present invention discloses a detection system for hydroxyl radicals generated in a gas-phase photocatalytic reaction. The detection system of the present invention comprises a gas-phase photocatalytic reaction hydroxyl radical capture device and a continuous flow chemiluminescence device, wherein the gas-phase hydroxyl radical capture device mainly comprises: an excitation light source, a gas washing bottle and an absorption tube for holding a photocatalyst and a hydroxyl capture probe; the continuous flow chemiluminescence device mainly comprises a quartz beaker for holding reagents, a peristaltic pump, a detection cell, a photomultiplier tube and a chemiluminescence analyzer, a computer host and a display; the absorption liquid and the oxidant are pumped into the detection cell by a peristaltic pump; the photomultiplier tube is connected to a signal analyzer host to convert the optical signal generated in the detection cell into an electrical signal; the signal analyzer host is connected to a computer terminal. The detection method of the present invention is simple to operate, fast in determination speed and high in specificity, and is suitable for rapid screening and evaluation of •OH generation capabilities in various gas-phase systems.

Description

Technical Field

[0001] The invention relates to a detection system for generating hydroxyl radicals by gas phase photocatalytic reaction. Background Art

[0002] As environmental pollution becomes increasingly prominent, environmental pollution control technology is of great significance for environmental protection and restoration. As photocatalytic technology has the advantages of being green, energy-saving, and efficient, it is widely used in environmental pollution and sterilization and disinfection. The basic principle of semiconductor photocatalytic technology is that the semiconductor photocatalyst is excited by light (the excitation energy is greater than or equal to the band gap width of the semiconductor photocatalyst), and the electrons in the valence band of the photocatalyst migrate to the conduction band, thereby forming holes in the valence band. The generated electron-hole pairs are very easy to react with oxygen molecules, water molecules, etc. to generate highly reactive substances (ROS), mainly including O 2 •− , •OH, H 2 O 2 and 1 O 2 A large number of studies have shown that ROS, as a highly reactive species, plays an important role in environmental cleaning and air sterilization mediated by photocatalytic reactions. Among them, •OH, as the most reactive ROS, has an oxidation potential of 2.8 V and 1.8 V in acidic and neutral solutions, respectively, and can oxidize and decompose almost all organic pollutants and bacteria. Therefore, •OH plays a key role in photocatalytic degradation of organic matter and sterilization reactions, and is generally considered to be the most effective oxidant, so it has received widespread attention and in-depth research. Quantitative analysis of the generation of •OH is one of the important indicators for measuring the performance of photocatalytic systems in pollutant removal and bacterial sterilization. Due to the active nature and short lifetime of •OH (microseconds), although many methods have been developed to detect the generation of •OH in liquid-phase photocatalytic reactions, there are few reports on the detection of •OH in gas-phase photocatalytic reactions, which is one of the difficulties in the current detection of •OH.

[0003] In the process of treating gaseous pollutants such as VOCs or sterilization and disinfection by photocatalysis, the role of ROS can only be reflected through ROS scavengers, which can only provide a side evidence. In addition, the introduction of free radical scavengers is generally carried out under liquid phase conditions, which will change the original surface state of the catalyst and cannot essentially reflect the nature of the gas-solid interface photocatalytic reaction. At present, the detection methods of •OH in the photocatalytic reaction process include electron spin capture technology (ESR), fluorescence probe method (FL) and chemiluminescence method (CL), but these methods are generally carried out in solution in actual detection and cannot directly reflect the actual situation of the gas-phase photocatalytic reaction process. Gas-solid interface reactions involve more steps and reaction conditions than liquid-solid interfaces. For example, in gas-solid photocatalysis, the molecular structure, loading method and surface characteristics of the catalyst, as well as experimental conditions (such as gas flow rate, flow rate, humidity, light intensity and temperature, etc.) will have a direct impact on the amount of ROS generated. Therefore, it is of great significance to develop a new method for detecting gas-phase ROS, especially for accurate and rapid detection of •OH with the strongest oxidizing ability. Summary of the invention

[0004] The purpose of the present invention is to provide a detection system for generating hydroxyl radicals by gas phase photocatalytic reaction.

[0005] The present invention provides a detection system for generating hydroxyl radicals by gas phase photocatalytic reaction, comprising:

[0006] The gas-phase hydroxyl radical capture device comprises an air generator, a hydroxyl radical capture probe holding container, a photocatalytic reactor, an excitation light source, a photocatalyst, an absorption bottle, and a power source; the air generator is connected to the hydroxyl radical capture probe holding container through a pipeline; the excitation light source is connected to the hydroxyl radical capture probe holding container through a pipeline and is connected to the power source; the photocatalyst is placed in the photocatalytic reactor, the excitation light source is placed in the photocatalytic reactor, and irradiates the photocatalyst when turned on, and the bottom of the photocatalytic reactor is connected to the absorption bottle;

[0007] The CFCL device comprises two oxidant containers, a photomultiplier tube, a detection cell, a chemiluminescence signal analyzer host and a computer terminal; the two oxidant containers and the absorption bottle are connected to the detection cell through a pipeline, and the photomultiplier tube is placed at the bottom of the detection cell;

[0008] The photomultiplier tube is used to collect the optical signal generated in the detection cell and convert it into an electrical signal, which is then transmitted to the chemiluminescent signal analyzer host; the chemiluminescent signal analyzer host is connected to the computer terminal.

[0009] In the above-mentioned detection system for generating hydroxyl radicals by gas phase photocatalytic reaction, the excitation light source is an ultraviolet light source or a visible light source.

[0010] In the above-mentioned detection system for generating hydroxyl radicals by gas phase photocatalytic reaction, the hydroxyl radical capture probe holding container contains hydroxyl radical capture probes;

[0011] A flow meter is arranged on the pipeline connecting the air generator and the hydroxyl radical capture probe containing container;

[0012] A ballast is arranged on the pipeline connecting the excitation light source and the power supply.

[0013] In the above detection system for generating hydroxyl radicals by gas-phase photocatalytic reaction, a peristaltic pump is respectively arranged on the pipelines connecting the two oxidant containing containers and the detection pool, and the oxidant therein is transported to the detection pool by driving the peristaltic pump.

[0014] In the above detection system for generating hydroxyl radicals by gas-phase photocatalytic reaction, a peristaltic pump is arranged on the pipeline connecting the absorption bottle and the detection cell, and the hydroxyl radicals captured by the hydroxyl radical probe are transported to the detection cell by the peristaltic pump.

[0015] In the above-mentioned detection system for generating hydroxyl radicals by gas-phase photocatalytic reaction, the hydroxyl radical capture probe is contained in the absorption bottle; the excitation light source excites the loaded photocatalyst to generate hydroxyl radicals which are captured in situ by the probe, and the small portion of hydroxyl radicals which are not captured are further captured by the hydroxyl radical capture probe contained in the absorption bottle.

[0016] In the above detection system for generating hydroxyl radicals by gas phase photocatalytic reaction, the hydroxyl radical capture probe is phthalic acid hydrazide.

[0017] In the above detection system for generating hydroxyl radicals by gas phase photocatalytic reaction, the photocatalyst is at least one of titanium dioxide, zinc oxide and zirconium dioxide loaded on a carrier, and the carrier is a 304 stainless steel mesh or nickel foam. Specifically, the titanium dioxide can be mixed with silica sol and loaded on the 304 stainless steel mesh or nickel foam by spraying.

[0018] In the above-mentioned detection system for generating hydroxyl radicals by gas phase photocatalytic reaction, the two oxidant containing containers respectively contain H 2 O 2 and K 5 Cu(HIO 6 ) 2 .

[0019] The present invention also provides the above detection system for generating hydroxyl radicals in gas phase photocatalytic reaction, which is applied to evaluate the ability of generating hydroxyl radicals in gas phase photocatalytic reaction.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1) The present invention realizes the detection of •OH in gas phase photocatalytic reaction.

[0022] 2) The gas-phase photocatalytic reaction •OH detection system instrument device of the present invention is simple and applicable to the detection of •OH in various gas-phase reactions.

[0023] 3) The detection system of •OH in the gas phase photocatalytic reaction of the present invention has good specificity. By capturing •OH in situ, the generated adduct has stable properties, thus overcoming the problem of its short life span.

[0024] 4) The gas phase photocatalytic •OH detection system detection method of the present invention is simple to operate and has a fast measurement speed, and is suitable for rapid screening and evaluation of the ability of photocatalytic materials to generate •OH. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the device for detecting hydroxyl radicals in a photocatalytic reaction according to the present invention.

[0026] Figure 1 The tags are as follows:

[0027] 1. Air generator; 2. Flow meter; 3. Container for hydroxyl radical capture probe; 4. Photocatalytic reactor; 5. Excitation light source; 6. Loaded photocatalyst; 7. Absorption bottle; 8. Ballast; 9. Power supply; 10. 11. Oxidant container; 12. 13. 14. Peristaltic pump; 15. Photomultiplier tube; 16. Detection cell; 17. Chemiluminescence signal analyzer host; 18. Computer terminal; 19. Thick silicone tube; 20. Thin silicone tube.

[0028] Figure 2 Different proportions of TiO 2 and silica sol, TiO 2 SEM images of TiO immobilized on 304 stainless steel mesh and nickel foam; (a) and (b) are 1:1 TiO 2 The ratio of TiO 2 Loaded on 304 stainless steel mesh; (c) and (d) are 5:1 TiO 2 The ratio of TiO 2 Loaded on 304 stainless steel mesh; (e) and (f) are 10:1 TiO 2 The ratio of TiO 2Loaded on 304 stainless steel mesh; (g) and (h) are 5:1 TiO 2 The ratio of TiO 2 Loaded on nickel foam.

[0029] Figure 3 (a) is the chemiluminescence standard curve of the concentration of the standard product of the reaction between the hydroxyl radical capture probe and the hydroxyl radical. Figure 3 (b) The chemiluminescence signal changes over time after the hydroxyl capture absorbent is mixed with two oxidants, including the absorbent without light irradiation, the absorbent after only UV irradiation, and the absorbent after UV irradiation of the catalyst; the catalyst is 5:1 TiO 2 The ratio of TiO 2 On nickel foam, Phth (20 μM), H 2 O 2 (50 μM), K 5 Cu(HIO 6 ) 2 (50 μM).

[0030] Figure 4 is the variation of the amount of hydroxyl radicals produced by different catalysts with the photoreaction time; Figure 4 (a) TiO loaded on nickel foam and 304 stainless steel 2 Comparison of the ability to produce hydroxyl radicals; Figure 4 (b) TiO with different proportions loaded on 304 stainless steel 2 Comparison of the ability to generate hydroxyl radicals with silica sol; Figure 4 (c) TiO loaded on nickel foam and 304 stainless steel 2 Comparison of toluene removal capabilities; Figure 4 (d) TiO with different proportions loaded on 304 stainless steel 2 Comparison of toluene removal capacity with silica sol; Figure 4 UV represents the excitation light, and nickel foam represents TiO loaded on nickel foam. 2 As a catalyst, 304 stainless steel means TiO loaded on 304 stainless steel 2 As catalyst, UV-C represents ultraviolet irradiation catalyst, UV-C 1:1, UV-C 5:1, and UV-C 10:1 catalysts are TiO 2 and silica sol were loaded on the surface of 304 stainless steel in ratios of 1:1, 5:1, and 10:1. DETAILED DESCRIPTION

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0032] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0033] like Figure 1 FIG. 1 is a schematic diagram of a detection system for generating hydroxyl radicals by gas-phase photocatalytic reaction provided by the present invention, which includes two parts:

[0034] The first part is a gas-phase hydroxyl radical capture device, including an air generator 1, a flow meter 2, a hydroxyl radical capture probe holding container 3, a photocatalytic reactor 4, an excitation light source 5, a photocatalyst 6, an absorption bottle 7, a ballast 8, and a power supply 9. The air generator 1 is connected to the hydroxyl radical capture probe holding container 3 through a pipeline; the hydroxyl radical capture probe is contained in the hydroxyl radical capture probe holding container 3; a flow meter 2 is arranged on the pipeline connecting the air generator 1 and the hydroxyl radical capture probe holding container 3. The excitation light source 5 is connected to the hydroxyl radical capture probe holding container 3 through a pipeline, and is connected to the power supply 9, and a ballast 8 is arranged on the pipeline connecting the excitation light source 5 and the power supply 9. The photocatalyst 6 is placed in the photocatalytic reactor 4, the excitation light source 5 is placed in the photocatalytic reactor 4, and the photocatalyst 6 is irradiated in an open manner, and the bottom of the photocatalytic reactor 4 is connected to the absorption bottle 7.

[0035] The second part is a CFCL device, which includes two oxidant containers 10, 11, peristaltic pumps 12, 13, 14, a photomultiplier tube 15, a detection pool 16, a chemiluminescent signal analyzer host 17 and a computer terminal 18. The two oxidant containers 10, 11 and the absorption bottle 7 are connected to the detection pool 16 through pipelines, and the photomultiplier tube 15 is placed at the bottom of the detection pool 16; wherein the photomultiplier tube 15 is used to convert the optical signal generated in the detection pool 16 into an electrical signal, and then transmit it to the chemiluminescent signal analyzer host 17; the chemiluminescent signal analyzer host 17 is connected to the computer terminal 18. Peristaltic pumps 14, 13 are respectively arranged on the pipelines connecting the two oxidant containers 10, 11 and the detection pool 16, and a peristaltic pump 12 is arranged on the pipeline connecting the absorption bottle 7 and the detection pool 16, so as to pump the two oxidants contained in each container and the hydroxyl radicals captured by the hydroxyl radical probe into the detection pool 16 for mixing.

[0036] Furthermore, the excitation light source is an ultraviolet light source.

[0037] Furthermore, the absorption bottle 7 contains a hydroxyl radical capture probe; the excitation light source 5 excites the loaded photocatalyst 6 to produce hydroxyl radicals which are captured in situ by the probe, wherein a small portion of the hydroxyl radicals not captured are further captured by the hydroxyl radical capture probe contained in the absorption bottle 7.

[0038] Furthermore, the hydroxyl radical capture probe is phthalic acid hydrazide.

[0039] Furthermore, the photocatalyst 6 is at least one of titanium dioxide, zinc oxide and zirconium dioxide supported on a carrier, and the carrier is a 304 stainless steel mesh or nickel foam.

[0040] Furthermore, the two oxidant containers 10 and 11 contain H 2 O 2 and K 5 Cu(HIO 6 ) 2 .

[0041] The process of using the detection system for generating hydroxyl radicals by gas phase photocatalytic reaction provided by the present invention is as follows:

[0042] First, a certain flow of air is generated by an air generator 1, and a trace amount of probes with a certain humidity is brought into a photocatalytic reactor 4 through a hydroxyl radical capture probe holding container 3. The loaded catalyst 6 is excited by an excitation light source 5 to generate hydroxyl radicals which are captured in situ by the probe. A small part of the hydroxyl radicals that are not captured is further captured by an absorption bottle 7 containing a hydroxyl radical capture probe at the bottom. Next, a peristaltic pump (12, 13, 14) is used to provide power to mix the absorption liquid and the two oxidants in a detection cell 16. The (5-hydroxy-phthalic acid hydrazide, 5-OH-Phth) generated in the absorption liquid reacts with the oxidant to generate a chemiluminescent signal. The photomultiplier tube 15 is used to convert the optical signal generated in the detection cell 16 into an electrical signal, which is then transmitted to a chemiluminescent signal analyzer host 17. The signal analyzer host is connected to a computer terminal 18 to display the detection result on a computer screen.

[0043] TiO supported on nickel foam 2 Taking catalyst as an example, the specific implementation process of this method for detecting gas phase photocatalytic system is explained:

[0044] like Figure 1 As shown, a certain amount of Phth (phthaloyl) is first added to the hydroxyl radical capture probe container 3. When the experiment is carried out, the air generator 1 is started to bring a trace amount of Phth with a certain humidity into the photocatalytic reactor 4. The end of the photocatalytic reactor 4 is passed into an absorption bottle 7 containing a certain amount of Phth with the same concentration. The absorption liquid with different reaction times is pumped into the detection pool 16 by the peristaltic pump 12 to mix with the other two oxidants (H 2 O 2 and K 5 Cu(HIO 6 ) 2) are mixed to produce a chemiluminescent reaction, generating a luminescent signal. At the same time, the photomultiplier tube 15 located at the bottom of the detection pool 16 converts the received light signal into an electrical signal, transmits it to the chemiluminescent signal analyzer host 17, and after amplification, transmits it to the computer display screen of the computer terminal 18 through a data line. When the power supply 9 is not turned on, since no •OH is generated, the absorption liquid does not have any substance that can generate a chemiluminescent signal. When mixed with the oxidant in the detection pool 16, there is almost no luminescent signal, and a very low background signal (continuous over time) will appear on the computer display screen of the computer terminal 18. Figure 3 (a)); On the contrary, when the power supply 9 is turned on, even in the absence of the photocatalyst 6, the excitation light source 5 emits short-wavelength ultraviolet rays to irradiate water to produce hydroxyl radicals, which are specifically captured by Phth in the hydroxyl radical capture probe container 3 to generate 5-OH-Phth. 5-OH-Phth has a high luminescence quantum yield. When mixed with the oxidant in the detection cell 16, it will produce a strong chemiluminescence signal, and the chemiluminescence intensity detected every two minutes will change with the speed of •OH generation (such as Figure 3 (a) shows that due to the instability of the light source, it can be seen that the concentration of •OH first increases with time, then decreases, and finally stabilizes. When the photocatalyst 6 is placed in the photocatalytic reactor 4 against the wall of the photocatalytic reactor 4, the excitation light source 5 (ultraviolet light source) is turned on for photocatalytic reaction. It can be clearly seen that the concentration of •OH generated every two minutes becomes higher and higher, and finally stabilizes, which is more than 2.0 times the concentration of •OH generated under ultraviolet light conditions alone.

[0045] In previous reports, it is generally believed that •OH is the main active species for degrading toluene. In order to further verify the accuracy of •OH detected by the above method, the present invention uses the detection system for generating hydroxyl radicals by gas phase photocatalytic reaction to degrade toluene. The results are as follows Figure 4 As shown, different catalysts (TiO supported on nickel foam) were tested. 2 , TiO supported on 304 stainless steel 2 ,like Figure 2 The TiO 2 The catalysts loaded on the surface of 304 stainless steel with silica sol in the ratio of 1:1, 5:1, and 10:1 were denoted as UV-C 1:1, UV-C 5:1, and UV-C 10:1. The •OH ( Figure 4 (a), (b)), and then these catalysts were used for the degradation of toluene ( Figure 4 (c), (d)), from Figure 4 It can be clearly seen that the concentration order of •OH produced is: 2 >TiO supported on nickel foam 2 ; Different proportions of TiO2 The concentration order of •OH produced by silica sol loaded on 304 stainless steel mesh is 5:1>10:1>1:1, that is, TiO 2 The highest concentration of •OH was produced when the ratio of 5:1 and silica sol was loaded on the surface of 304 stainless steel as a photocatalyst. The degradation efficiency of toluene was almost consistent with the order of •OH production within the 20 min detection time. The above results further prove that this detection method successfully realizes the detection of •OH in the gas phase photocatalytic system.

Claims

1. A detection system for hydroxyl radicals generated by gas phase photocatalytic reaction, It is characterized in that It includes: A gas-phase hydroxyl radical capture device comprises an air generator, a hydroxyl radical capture probe holding container, a photocatalytic reactor, an excitation light source, a photocatalyst, an absorption bottle, and a power source; the air generator is connected to the hydroxyl radical capture probe holding container through a pipeline; the excitation light source is connected to the hydroxyl radical capture probe holding container through a pipeline and is connected to the power source; the photocatalyst is placed in the photocatalytic reactor, the excitation light source is placed in the photocatalytic reactor and irradiates the photocatalyst when turned on, and the bottom of the photocatalytic reactor is connected to the absorption bottle; It comprises two oxidant containers, a photomultiplier tube, a detection cell, a chemiluminescence signal analyzer host and a computer terminal; the two oxidant containers and the absorption bottle are connected to the detection cell through a pipeline, and the photomultiplier tube is placed at the bottom of the detection cell; The photomultiplier tube is used to collect the optical signal generated in the detection cell and convert it into an electrical signal, which is then transmitted to the chemiluminescent signal analyzer host; the chemiluminescent signal analyzer host is connected to the computer terminal; The hydroxyl radical capture probe storage container contains a hydroxyl radical capture probe; A flow meter is arranged on the pipeline connecting the air generator and the hydroxyl radical capture probe containing container; A ballast is arranged on the pipeline connecting the excitation light source and the power supply; A peristaltic pump is respectively arranged on the pipelines connecting the two oxidant containing containers and the detection cell; The two oxidant storage containers respectively store H 2 O 2 and K 5 Cu(HIO 6 ) 2 ; A peristaltic pump is arranged on the pipeline connecting the absorption bottle and the detection cell; The absorption bottle contains the hydroxyl radical capture probe; The hydroxyl radical capture probe is phthalic acid hydrazide; The photocatalyst is at least one of titanium dioxide, zinc oxide and zirconium dioxide loaded on a carrier, and the carrier is a 304 stainless steel mesh or foamed nickel.

2. The detection system for generating hydroxyl radicals by gas phase photocatalytic reaction according to claim 1, It is characterized in that The excitation light source is an ultraviolet light source or a visible light source.

3. Use of the detection system for generating hydroxyl radicals in gas-phase photocatalytic reactions according to claim 1 or 2 in evaluating the ability to generate hydroxyl radicals in gas-phase photocatalytic reactions.

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