Method for preparing an aerogel material and use thereof

Abstract

The application discloses a TiO2 / SnIn4S8 / chitosan aerogel photocatalyst and a preparation method and application thereof. The TiO2 / SnIn4S8 is used as a material matrix, and chitosan is used as a structural framework. An aerogel photocatalyst with an oriented pore structure is prepared through an oriented freezing method, the problem of difficult recycling of powder materials is solved, tetracycline and Cr(Ⅵ) can be effectively degraded under visible light, the aerogel photocatalyst has good stability and repeatability, and has a good prospect in practical water environment application.

Description

Technical Field

[0001] The present invention belongs to the field of functional materials, specifically the field of photocatalysis, and relates to the preparation and application of a TiO2 / SnIn4S8 / chitosan aerogel photocatalyst. Background Art

[0002] Photocatalytic technology is a green, environmentally friendly and energy-saving technology, and is considered to be an ideal method for pollutants in water. Using metal sulfides as photocatalytic materials can effectively degrade pollutants in water bodies. However, most current photocatalytic technologies use powdered catalysts, which are not conducive to recycling and hinder their industrial application. How to solve this problem has become a major research hotspot. Chitosan (CS) is one of the most abundant biopolymers in nature. It has the advantages of high efficiency, biodegradability and environmental protection. Many researchers have applied chitosan gel to wastewater treatment. Therefore, the metal sulfide composite catalyst is compounded with CS to prepare an aerogel material, which is expected to help improve its recyclability while maintaining its photocatalytic performance. Summary of the Invention

[0003] The present invention aims to provide an aerogel photocatalyst with a TiO2 / SnIn4S8 composite material as the material matrix and chitosan as the structural framework, wherein the obtained aerogel photocatalyst is prepared by an oriented freezing method. The construction of the aerogel can greatly improve the recyclability of the material.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] The first aspect of the present invention provides a preparation method of a TiO2 / SnIn4S8 / chitosan aerogel photocatalyst. The TiO2 / SnIn4S8 / chitosan photocatalyst uses a TiO2 / SnIn4S8 composite material as a material matrix and chitosan as a structural framework.

[0006] The aforementioned TiO2 / SnIn4S8 / chitosan aerogel photocatalyst is further improved, wherein the TiO2 / SnIn4S8 composite material accounts for 15-45% by weight of the aerogel photocatalyst. (Reference patent for the preparation method of the TiO2 / SnIn4S8 composite material: CN202310884082.X)

[0007] The preparation method of the TiO2 / SnIn4S8 / chitosan aerogel photocatalyst comprises the following steps:

[0008] The TiO2 / SnIn4S8 / chitosan aerogel photocatalyst is used to mix the TiO2 / SnIn4S8 / chitosan aerogel photocatalyst with wastewater containing tetracycline and hexavalent chromium, stir the mixture in the dark, and wait for adsorption equilibrium. Then, a photocatalytic reaction is carried out under illumination to degrade the tetracycline and reduce the hexavalent chromium. The resulting TiO2 / SnIn4S8 / chitosan aerogel photocatalyst can simultaneously degrade tetracycline and hexavalent chromium, providing a preparation strategy for the photocatalytic degradation of various water pollutants.

[0009] The significant advantages of the present invention are:

[0010] (1) The simultaneous photocatalytic degradation of tetracycline and hexavalent chromium in the same degradation system is more in line with the actual water environment.

[0011] (2) Compared with traditional powder catalysts, we use aerogel as the structural framework and load the catalyst in chitosan, which greatly improves the recyclability of the material and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a SEM image of the cross section of the TiO2 / SnIn4S8 chitosan aerogel photocatalyst prepared in Example 3 of the present invention.

[0013] Figure 2 This is a SEM image of the longitudinal section of the TiO2 / SnIn4S8 chitosan aerogel photocatalyst prepared in Example 3 of the present invention.

[0014] Figure 3 The photocatalytic degradation of tetracycline and hexavalent chromium by the TiO2 / SnIn4S8 chitosan aerogel photocatalyst prepared in Examples 1 to 4 of the present invention is shown in Figure a. The degradation of tetracycline is shown in Figure b. The degradation of hexavalent chromium is shown in Figure 2.

[0015] Figure 4 This is a cyclic degradation experiment of tetracycline and hexavalent chromium using the TiO2 / SnIn4S8 chitosan aerogel photocatalyst prepared in Examples 1 to 4 of the present invention.

[0016] Figure 5 This is a physical picture of the TiO2 / SnIn4S8 chitosan aerogel photocatalyst prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described below through specific examples in conjunction with the accompanying drawings.

[0018] Preparation of TiO2 / SnIn4S8 composite photocatalyst (see patent: CN202310884082.X)

[0019] (1) Measure 20 mL of 40% hydrofluoric acid solution and add it to a polyethylene liner. Slowly add 1 g of Ti3AlC2 powder to the hydrofluoric acid solution, seal with a mucous membrane, and stir for 24 hours. Wash the precipitate with deionized water until neutral, then dry it in a vacuum drying oven at 60°C for 12 hours. The obtained Ti3C2 powder is calcined in a tube furnace at 500°C for 0.5 hours to obtain multilayered TiO2 nanoparticles.

[0020] (2) Dissolve SnCl4·5H2O and InCl3·4H2O in acetic acid solution to prepare 0.6mmol / L Sn 4+ solution and 2.4mmol / L In 3+ solution.

[0021] (3) Weigh 12 mg of TiO2 and dissolve it in 60 mL of deionized water. Ultrasonicate for 30 minutes. Add 1 mL of Sn 4+ Solution, 1mL In 3+ The solution and 6 mmol of thioacetamide were mixed and transferred to an autoclave for a hydrothermal reaction at 150°C for 12 hours. After completion of the reaction, the mixture was cooled to room temperature. The precipitate was washed with deionized water and anhydrous ethanol until neutral, and then dried in a vacuum oven at 60°C for 12 hours to obtain a 6 wt% TiO2 / SnIn4S8 composite photocatalyst, designated 6-TS.

[0022] Example 1

[0023] Preparation of 15wt% TiO2 / SnIn4S8 Composite Material / Chitosan Photocatalyst

[0024] (1) Disperse 3 g of chitosan evenly in 97 mL of 2% acetic acid solution, ultrasonicate for 30 min, and heat and stir for 30 min to disperse the chitosan evenly in the acetic acid solution. Weigh 30 mg of TiO2 / SnIn4S8 composite material and dissolve it in water. Add 200 mL of chitosan solution and ultrasonicate for 30 min.

[0025] (2) After uniform dispersion, the mixture was poured into a polytetrafluoroethylene tube, placed on a copper plate, and then poured into liquid nitrogen for an orientation freezing test. After the reaction was completed, the mixture was placed in an ultra-low temperature freezer and frozen for 6 hours. After vacuum drying in a freeze dryer, the desired sample was obtained. It was named TSC3.

[0026] Comparative Example 1

[0027] (1) 3 g of chitosan was evenly dispersed in 97 mL of 2% acetic acid solution, ultrasonicated for 30 min, and heated and stirred for 30 min to make the chitosan evenly dispersed in the acetic acid solution.

[0028] (2) The mixture was then poured into a polytetrafluoroethylene tube, placed on a copper plate, and filled with liquid nitrogen for an orientation freezing test. After the reaction was completed, the mixture was placed in an ultra-low temperature freezer and frozen for 6 hours. After vacuum drying in a freeze dryer, the desired sample was obtained. Pure chitosan aerogel was obtained and named CS.

[0029] Depend on Figure 1 It can be seen from the cross section of the sample that the sample presents a well-arranged microchannel structure. The sample is composed of a large number of connected pore structures, and the pore structure and size are not much different, forming a honeycomb layered network skeleton. This may be because ice crystals grow rapidly at ultra-low temperatures (-196°C), and chitosan molecular chains are evenly arranged, forming a good honeycomb structure and regular and orderly directional channels. During the freeze casting process, due to the directional growth of ice, Figure 1 The layered structure can be easily identified in the MgCl2O3 sample. It is speculated that the layered structure improves the mechanical properties of the sample and provides more active sites by increasing the specific surface area. Figure 2 This is the longitudinal section of the sample (parallel to the freezing orientation direction). The longitudinal section of the material is a number of parallel strips, similar to the radial section of wood. This may be due to the rapid growth of freezing orientation and the rapid upward growth of ice crystals.

[0030] Example 2

[0031] A TiO2 / SnIn4S8 / chitosan aerogel photocatalyst with chitosan as its structural framework is substantially the same as that in Example 1, except that the mass percentage of the TiO2 / SnIn4S8 composite material to the chitosan in the TiO2 / SnIn4S8 composite photocatalyst in Example 2 is 30%. This photocatalyst is designated TSC6.

[0032] Example 3

[0033] A TiO2 / SnIn4S8 / chitosan aerogel photocatalyst with chitosan as its structural framework is substantially the same as that of Example 1, differing only in that the TiO2 / SnIn4S8 composite material accounts for 45% of the chitosan by mass in the TiO2 / SnIn4S8 composite photocatalyst of Example 3. This photocatalyst is designated TSC9.

[0034] Example 4

[0035] Photocatalytic simultaneous degradation of tetracycline and hexavalent chromium

[0036] The TiO2 / SnIn4S8 / chitosan aerogel photocatalysts and aerogel photocatalyst prepared in Examples 1-3 and Comparative Example 1 were added to 50 mL of a solution containing 20 mg / L tetracycline and 15 mg / L hexavalent chromium. The dark reaction was allowed to proceed for 60 minutes to achieve adsorption-desorption equilibrium. The photocatalytic reaction was then carried out under a 300W xenon lamp for 120 minutes to degrade the tetracycline and reduce the hexavalent chromium in the water.

[0037] Depend on Figure 3 The TC degradation efficiencies of TSC3, TSC6, TSC9, and CS after 2 hours of illumination were 48.90%, 79.07%, 96.11%, and 3.6%, respectively. The Cr(VI) reduction efficiencies were 36.16%, 43.73%, 58.51%, and 5.9%, respectively. TSC9 achieved the highest degradation efficiency, demonstrating that a higher TiO2 / SnIn4S8 composite ratio resulted in a more effective catalyst.

[0038] Depend on Figure 4 Three cycles of photocatalytic degradation of TC and Cr(VI) demonstrate the excellent stability of the TSC aerogel. Within 120 minutes, the degradation rate of tetracycline decreased from 96.11% to 69.08%, and the degradation rate of Cr(VI) decreased from 58.51% to 39.18%. This demonstrates the excellent reusability of the TSC aerogel for the degradation of TC and Cr(VI). The reduction in active sites during the cleaning process may be responsible for the decreased tetracycline degradation ability.

[0039] Figure 5 This is a photo of the TiO2 / SnIn4S8 chitosan aerogel photocatalyst prepared in Example 3 of the present invention. Compared with powder catalysts, the aerogel material prepared in the present invention easily floats on the water surface, which is convenient for recycling.

[0040] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a TiO2 / SnIn4S8 / chitosan aerogel photocatalyst, characterized in that: The TiO2 / SnIn4S8 composite material is added to the chitosan solution, and the TiO2 / SnIn4S8 composite material is wrapped with chitosan, wherein the mass percentage of the TiO2 / SnIn4S8 composite material to the chitosan is 15-45wt%; The preparation method specifically comprises the following steps: (1) Disperse chitosan evenly in acetic acid solution, and after ultrasonication and stirring, disperse chitosan evenly in the acetic acid solution; (2) Weigh a certain amount of TiO2 / SnIn4S8 composite material, dissolve it in water, add a certain amount of chitosan solution, and use an ultrasonic machine to perform ultrasonic dispersion; (3) After being evenly dispersed, pour it into a polytetrafluoroethylene tube for orientation freezing experiment; after the reaction is completed, freeze it in an ultra-low temperature refrigerator, and then use a freeze dryer for vacuum drying to obtain the desired sample; In step (1), the amount of chitosan is 1-5 g, the acetic acid content in the acetic acid solution is 1-5 wt %, and the ultrasonic and stirring time is 30-60 min; In step (2), the amount of TiO2 / SnIn4S8 composite material used is 30-90 mg, the amount of chitosan solution used is 200 mL, and the ultrasonic dispersion time is 30 min; The orientation freezing experiment in step (3) uses liquid nitrogen as a cooling source, the reaction time is 5-15 minutes, the ultra-low temperature refrigerator freezing time is 6-12 hours, and the vacuum drying time is 12-24 hours.

2. The TiO2 / SnIn4S8 / chitosan aerogel photocatalyst prepared according to the preparation method of claim 1.

3. The use of the TiO2 / SnIn4S8 / chitosan aerogel photocatalyst according to claim 2, characterized in that: Used to degrade tetracycline and reduce Cr(VI) in water.

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