Preparation method of zsh / ssh composite material and application of zsh / ssh composite material in photocatalytic degradation of toluene

Abstract

The application provides a preparation method of ZnSn(OH)6 / SrSn(OH)6 composite material by using a hydrothermal method in one step, which provides a new idea for treating toluene in VOCs and belongs to the technical field of atmospheric pollution control engineering. The composite material is prepared by using ZnCl2, SrCl2*6H2O, SnCl4*5H2O and NaOH as raw materials, dissolving and mixing, hydrothermal treatment at 120 DEG C for 8h, washing several times with deionized water and ethanol, drying and grinding. When treating, the composite material for treating toluene in waste gas is put into a reactor for treatment. The preparation process is simple, easy to control, convenient to operate, low in cost, and the raw material is easy to obtain, and the product has the advantages of high degradation efficiency of toluene and the like. The composite material has an 86% degradation rate of toluene under the condition of ultraviolet light irradiation for 30min, and has important application prospect in treating organic waste gas.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of synthesis of photocatalytic materials and degradation of organic volatile matters, and particularly relates to a preparation method of photocatalytic materials, a degradation material for toluene in waste gas, and a treatment method. BACKGROUND

[0002] As one of the main environmental pollutants, volatile organic compounds (VOCs) not only directly harm the environment and human body, but also can generate secondary pollutants by photochemical reaction with nitrogen oxides under sunlight, thus causing serious indirect harm to the atmospheric environment. Therefore, effective governance of VOCs is of great significance to pollution reduction and carbon reduction.

[0003] Photocatalytic method is a new VOCs treatment technology developed in recent years, which can produce strong oxidizing active free radicals under mild conditions, so as to degrade organic pollutants such as benzene, toluene and formaldehyde into other small molecular compounds, CO2 and H2O. Therefore, photocatalytic technology is considered as an economic, efficient and environmentally friendly technology for VOCs degradation. Although TiO2 [1] , ZnO and other photocatalysts have achieved certain results in the treatment of VOCs, most photocatalysts are easily covered with excess intermediate products and secondary toxic by-products in the process of degrading organic pollutants, which leads to easy deactivation of the catalysts and poor photocatalytic stability. The new type of semiconductor photocatalyst SrSn(OH)6 has a larger band gap and stronger redox capacity. In addition, a large number of hydroxyl groups are uniformly distributed on the surface of SrSn(OH)6, which are easily oxidized to hydroxyl radicals (·OH) under ultraviolet light. ·OH is the main active group for degrading organic pollutants, so SrSn(OH)6 has great potential in photocatalytic oxidation of VOCs. However, SrSn(OH)6 has the shortcomings of narrow light absorption range and low efficiency of photo-generated electron-hole separation, which limits its photocatalytic efficiency. Therefore, it is of academic value and practical significance to develop new SrSn(OH)6 and its composite for treating VOCs.

[0004] In recent years, hydroxystannate has been widely used in fire and smoke suppression, gas sensing testing and other fields, and has been further explored in the degradation of VOCs, antibiotics and dyes. Hydroxystannate has shown excellent photocatalytic oxidation potential, so it has attracted more attention from researchers. In the current exploration of the photocatalytic performance of zinc hydroxystannate and strontium hydroxystannate, scholars mainly focus on the simple doping of metal atoms or non-metal atoms, and the best process exploration of monomer synthesis. The existing technology has not proved that ZnSn(OH)6 and SrSn(OH)6 composites can be synthesized in one step. It is found that different feeding ratios will affect the photocatalytic performance of the composite, and the composite system has good degradation effect on toluene under ultraviolet light. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is: addressing the issues of complex material preparation processes, complex regeneration, and environmental pollution associated with photocatalytic degradation of toluene in existing technologies. This invention provides a method for preparing a composite material that is rich in readily available raw materials, has high degradation efficiency, is simple to prepare, and is environmentally friendly; as well as a photocatalytic material and treatment method for treating toluene in waste gas.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing a composite photocatalytic material and its application, comprising the following steps:

[0007] 1. Preparation method of ZnSn(OH)6 / SrSn(OH)6 composite material (ZnSn(OH)6 is abbreviated as ZSH, SrSn(OH)6 as SSH, ZnSn(OH)6 / SrSn(OH)6 as ZSH / SSH)

[0008] 1) Using SrCl2·6H2O, ZnCl2, SnCl4·5H2O and NaOH as raw materials, wherein the molar ratio of SrCl2·6H2O to ZnCl2 is 0:5, 0.5:4.5, 0.75:4.25, 1:4, 2:3, 3:2, 4:1, 5:0;

[0009] 2) Dissolve the mixture of SrCl2·6H2O and ZnCl2, SnCl4·5H2O and NaOH from step 1) separately to obtain clear solutions;

[0010] 3) Add the NaOH solution obtained in step 2) dropwise to the SnCl4·5H2O solution under stirring, and then add the SrCl2·6H2O and ZnCl2 mixture dropwise.

[0011] 4) Transfer the mixed solution obtained in step 3) into a 150 mL polytetrafluoroethylene hydrothermal reactor and perform a hydrothermal reaction at 120 °C for 4-12 h.

[0012] 5) Wash the precipitate obtained in step 4 several times with deionized water and ethanol, dry it at 60℃, and grind it for later use. The centrifugation rate is 4500 r / min.

[0013] 2. Application of ZnSn(OH)6 / SrSn(OH)6 composite material in the photocatalytic degradation of toluene in waste gas

[0014] The toluene is a mixture of toluene standard gas and dry and wet air in a certain proportion, wherein the toluene flow rate is 42 SCCM and the dry and wet air are 25 SCCM respectively. The application method is to put a certain amount of catalyst into the photocatalytic reactor, wherein the light source is an ultraviolet lamp, and the peak intensity of gas chromatography reflects the toluene content in the tail gas after catalytic treatment.

[0015] Four groups of 50mg composite catalysts were weighed in parallel onto four quartz plates, and then evenly dispersed using anhydrous ethanol. After drying at 60℃, the catalysts were placed in a photocatalytic reactor, and a mixture of toluene standard gas and dry and humid air was introduced.

[0016] After the system stabilized, the UV lamp was turned on, and a sample was injected every two minutes to record the degradation of toluene by the catalyst. Each sample was tested for 30 minutes. An activity curve was plotted by comparing the ratio of the remaining toluene content in the mixed gas to the toluene content at system equilibrium.

[0017] In existing technologies, research on ZnSn(OH)6 and SrSn(OH)6 mainly focuses on modifying process conditions, doping, composite formation, and loading, primarily for photocatalytic hydrogen production and the degradation of pollutants such as VOCs, NOx, and dyes. To date, no research has proposed a one-step hydrothermal method for synthesizing ZnSn(OH)6 / SrSn(OH)6 composites and applying it to the field of photocatalytic VOC degradation. This invention breaks through the conventional understanding of ZnSn(OH)6 and SrSn(OH)6 in the field of photocatalysis, synthesizing a ZnSn(OH)6 / SrSn(OH)6 composite in one step. Research shows that the two successfully form a heterojunction, achieving a degradation rate of up to 86% for gaseous toluene. This invention has advantages such as simple operation, environmental friendliness, low cost, and high cycle stability, and has excellent prospects for industrial application. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments. This embodiment is implemented based on the technology of the present invention, and detailed implementation methods and specific operating procedures are given to illustrate the inventiveness of the present invention. However, the scope of protection of the present invention is not limited to the following embodiments. Attached Figure Description

[0019] Figure 1 X-ray diffraction (XRD) patterns of ZSH, SSH, and ZSH / SSH composite materials of various proportions synthesized by the method of the present invention;

[0020] Figure 2 SEM spectra of SSH (a), wood (b), ZSH (c), 20% ZnSn(OH)6 / SrSn(OH)6 (de), and TEM spectra of 20% ZSH / SSH (fh) prepared by the method of the present invention;

[0021] Figure 3 BET spectra of ZSH, SSH, and 20% ZSH / SSH prepared by the method of this invention;

[0022] Figure 4 The degradation activity curves of ZSH, SSH, and ZSH / SSH composite materials of various proportions prepared by the method of the present invention on toluene are shown.

[0023] Figure 5 Activity curves of catalysts prepared at different reaction times for the degradation of toluene;

[0024] Figure 6 Cyclic activity curves of 20% ZSH / SSH composite material for toluene degradation prepared under optimal conditions;

[0025] Example 1

[0026] A method for preparing a ZnSn(OH)6 / SrSn(OH)6 composite photocatalytic material includes the following steps:

[0027] S1. Using SrCl2·6H2O, ZnCl2, SnCl4·5H2O, and NaOH as raw materials, wherein the molar ratio of SrCl2·6H2O to ZnCl2 is 4:1. Weigh 1.067g of SrCl2·6H2O and ZnCl2, mix and dissolve them in 50mL of deionized water, stir well, and label this as solution B; weigh 1.753g of SnCl4·5H2O, dissolve it in 20mL of deionized water and 5mL of ethylene glycol, and label this as solution A; weigh 1.200g of NaOH, dissolve it in 25mL of deionized water, and label this as solution C.

[0028] S2. Add the C solution obtained in step S1 dropwise to the A solution under stirring, then add the B solution dropwise, and stir until a white turbid liquid is obtained.

[0029] S3. Transfer the mixed solution obtained in S2 into a 150 mL polytetrafluoroethylene hydrothermal reactor and perform a hydrothermal reaction at 120 °C for 8 h.

[0030] S4. Wash the precipitate obtained in S3 several times with deionized water and ethanol, dry it at 60℃, and grind it for later use. The centrifugation rate is 4500 r / min.

[0031] This implementation case demonstrates the one-step hydrothermal synthesis of ZnSn(OH)6 / SrSn(OH)6, as shown by XRD analysis. Figure 1The XRD patterns of ZnSn(OH)6 / SrSn(OH)6 composites with different ratios are shown in the figure. It can be observed that the diffraction peaks of pure ZSH and SSH are consistent with the standard cards. The intensity and sharpness of the diffraction peaks indicate that the prepared catalyst has high crystallinity. The diffraction peaks of the composite are similar to those of the SSH pattern, but four ZSH diffraction peaks appear at 22.9°, 32.6°, 52.9°, and 58.7°, corresponding to crystal planes (221), (501), (420), and (422), respectively. The peak intensity of ZSH gradually increases with increasing composite ratio, indicating that the composite photocatalyst has been successfully prepared.

[0032] Scanning electron microscopy was used to scan the morphology of SSH, ZSH, and 20% ZSH / SSH samples, such as... Figure 2 a-2b shows that SSH monomers have similar texture and structure to wood. ZSH( Figure 2 c) It exhibits uniform cubic particles. In the composite, the wood-grain-like grooved structure of SSH provides excellent bonding conditions for ZSH. TEM and HRTEM of 20% ZSH / SSH demonstrate that the two are bonded to form a heterojunction structure, while also showing lattice fringes with interplanar spacings of 310 and 222, corresponding to certain crystal planes of ZSH and SSH, respectively, further proving the formation of the heterojunction.

[0033] Table 1 shows the specific surface area and pore volume of SSH, ZSH, and 20% ZSH / SSH. The composite catalyst has a larger specific surface area and a pore volume between that of the two pure substances. The relatively larger specific surface area provides more active sites for the reaction, thus creating conditions for photocatalysis. Figure 3 The nitrogen adsorption-desorption curves for SSH, ZSH, and 20% ZSH / SSH are shown in the figure. As can be seen from the figure, the nitrogen adsorption-desorption curves of the samples belong to hollow capillary condensation (IV) type and have obvious H3 type hysteresis loop, which proves that there is a mesoporous structure in the catalyst samples.

[0034] Table 1. Specific surface area and pore volume of ZSH, SSH, and 20% ZSH / SSH

[0035]

[0036] This embodiment provides a photocatalyst for treating gaseous toluene, the composition of which is the composite photocatalytic material prepared by the method described above in this embodiment.

[0037] The toluene is a mixture of toluene standard gas and dry and wet air in a certain proportion, wherein the toluene flow rate is 42 SCCM and the dry and wet air are 25 SCCM respectively. The application method is to put a certain amount of catalyst into the photocatalytic reactor, wherein the light source is an ultraviolet lamp, and the peak intensity of gas chromatography reflects the toluene content in the tail gas after catalytic treatment.

[0038] Four groups of 50mg composite catalysts were weighed in parallel onto four quartz plates, and then evenly dispersed using anhydrous ethanol. After drying at 60℃, the catalysts were placed in a photocatalytic reactor, and a mixture of toluene standard gas and dry and humid air was introduced.

[0039] After the system stabilized, the UV lamp was turned on, and a sample was injected every two minutes to record the degradation of toluene by the catalyst. The test time for each sample was 30 minutes. The results showed that the degradation rate was as high as 86%, while the degradation rates of toluene by SSH and ZSH prepared under the same conditions were 35% and 40%, respectively, which was a significant improvement and achieved outstanding degradation results.

[0040] Example 2

[0041] In this embodiment, except that the ratio of S1, n(SrCl2·6H2O):n(ZnCl2) is replaced with 0.5:4.5, 0.75:4.25, 1:4, 2:3 or 3:2, everything else is the same as in Example 1.

[0042] This embodiment provides a photocatalyst for treating gaseous toluene, the composition of which is the composite photocatalytic material prepared by the method described above in this embodiment.

[0043] The toluene is a mixture of toluene standard gas and dry and wet air in a certain proportion, wherein the toluene flow rate is 42 SCCM and the dry and wet air are 25 SCCM respectively. The application method is to put a certain amount of catalyst into the photocatalytic reactor, wherein the light source is an ultraviolet lamp, and the peak intensity of gas chromatography reflects the toluene content in the tail gas after catalytic treatment.

[0044] Four groups of 50mg composite catalysts were weighed in parallel onto four quartz plates, and then evenly dispersed using anhydrous ethanol. After drying at 60℃, the catalysts were placed in a photocatalytic reactor, and a mixture of toluene standard gas and dry and humid air was introduced.

[0045] After the system stabilizes, turn on the UV lamp and inject one sample every two minutes to record the degradation of toluene by the catalyst. Each sample is tested for 30 minutes. Figure 4 As shown, the highest removal rate of toluene was achieved when n(SrCl2·6H2O):n(ZnCl2) = 4:1.

[0046] Example 3

[0047] Except for S3, where the reaction time is changed from 8h to 4h, 6h, 10h or 12h, all other aspects in this embodiment are the same as in Example 1.

[0048] This embodiment provides a photocatalyst for treating gaseous toluene, the composition of which is the composite photocatalytic material prepared by the method described above in this embodiment.

[0049] The toluene is a mixture of toluene standard gas and dry and wet air in a certain proportion, wherein the toluene flow rate is 42 SCCM and the dry and wet air are 25 SCCM respectively. The application method is to put a certain amount of catalyst into the photocatalytic reactor, wherein the light source is an ultraviolet lamp, and the peak intensity of gas chromatography reflects the toluene content in the tail gas after catalytic treatment.

[0050] Four groups of 50mg composite catalysts were weighed in parallel onto four quartz plates, and then evenly dispersed using anhydrous ethanol. After drying at 60℃, the catalysts were placed in a photocatalytic reactor, and a mixture of toluene standard gas and dry and humid air was introduced.

[0051] After the system stabilizes, turn on the UV lamp and inject one sample every two minutes to record the degradation of toluene by the catalyst. Each sample is tested for 30 minutes. Figure 5 As shown, when the reaction time is 8 hours, the removal rate of toluene is as high as 86.81%.

[0052] Example 4

[0053] In this embodiment, the photocatalytic reaction time was changed from 30 min to five repeated tests, but everything else was the same as in Example 1.

[0054] This embodiment provides a photocatalyst for treating gaseous toluene, the composition of which is the composite photocatalytic material prepared by the method described above in this embodiment.

[0055] The toluene is a mixture of toluene standard gas and dry and wet air in a certain proportion, wherein the toluene flow rate is 42 SCCM and the dry and wet air are 25 SCCM respectively. The application method is to put a certain amount of catalyst into the photocatalytic reactor, wherein the light source is an ultraviolet lamp, and the peak intensity of gas chromatography reflects the toluene content in the tail gas after catalytic treatment.

[0056] Four groups of 50mg composite catalysts were weighed in parallel onto four quartz plates, and then evenly dispersed using anhydrous ethanol. After drying at 60℃, the catalysts were placed in a photocatalytic reactor, and a mixture of toluene standard gas and dry and humid air was introduced.

[0057] After the system stabilizes, turn on the UV lamp and inject one sample every two minutes to record the degradation of toluene by the catalyst. Repeat the test five times for 30 minutes. Figure 6As shown, after five cycles, the removal rate of toluene remained stable at around 86%.

[0058] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing a composite photocatalytic material for treating toluene in waste gas, characterized in that, Includes the following steps: 1) Using SrCl2•6H2O, ZnCl2, SnCl4•5H2O and NaOH as raw materials, wherein the molar ratio of SrCl2•6H2O to ZnCl2 is 1:4, 2:3, 3:2, 4:1; 2) Dissolve the mixture of SrCl2•6H2O and ZnCl2, SnCl4•5H2O and NaOH from step 1) separately to obtain a clear solution; 3) Add the NaOH solution obtained in step 2) dropwise to the SnCl4•5H2O solution under stirring, and then add the SrCl2•6H2O and ZnCl2 mixture dropwise. 4) Transfer the mixed solution obtained in step 3) into a 150 mL polytetrafluoroethylene hydrothermal reactor and perform a hydrothermal reaction at 120 °C for 4-12 h. Step 4) Hydrothermal generation simultaneously produces ZnSn(OH)6 and SrSn(OH)6; (Sr+Zn):Sn = 1:1 molar ratio.

2. A composite photocatalytic material for treating toluene in waste gas prepared by the method described in claim 1.

3. An application of the composite photocatalytic material for treating toluene in waste gas as described in claim 2, characterized in that, The method of application is as follows: the photocatalyst is coated on the surface of a quartz plate, dried at 60°C, placed in a photocatalytic reactor, and degraded at 50-100 ppm toluene under ultraviolet light irradiation. The degradation effect is reflected by the peak area of ​​gas chromatography.

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