A method for extraction coupled with photocatalytic degradation of environmental pollutants

Abstract

The application provides a method for extracting and coupling photocatalytic degradation of environmental pollutants, which adopts Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst as a photocatalyst and adopts [BMIM]PF6 ionic liquid as an extractant to treat environmental pollutants. By introducing ionic liquid into the photocatalytic system, an ionic liquid bridge is built between the reactants and the photocatalyst, the mass transfer effect is significantly improved in a short time, the extraction and coupling photocatalytic efficiency reaches 83.83% within 60 min, which is 2.12 times of that without the extractant, and when the illumination time is prolonged to 120 min, the extraction and coupling photocatalytic degradation rate is improved to 90.5%.

Description

Technical Field

[0001] This invention belongs to the field of organic matter catalytic degradation technology, and relates to an extraction-coordinated photocatalytic system, specifically a method for extraction coupled with photocatalytic degradation of environmental pollutants. Background Technology

[0002] While the widespread use of tetracycline (TC) worldwide has brought medical convenience, the water pollution and human health problems it causes have become a significant challenge. Recently, a research team led by Yong Guo et al., through theoretical calculations, revealed the role of superoxide radicals (∙O2) in the TC activation process. - The lowest energy barrier was observed (43.4 kcal / mol), followed by photogenerated holes (h). + (50.1 kcal / mol). Therefore, the focus is on ∙O2, which plays a dominant role in the degradation of TC. - Designing efficient photocatalysts is of great significance.

[0003] Currently, multiple studies have indicated that Fe(II) can effectively activate the production of O2·2O2·2O3 ... - This free radical can not only directly participate in the degradation of pollutants as the main active ingredient, but also generate ･OH ​​through single-electron activation, thus participating in the reaction together. Simultaneously, the extraordinary electronic structure of the ultra-small metal clusters allows its metal sites to effectively induce photogenerated electrons (electrons). - Directed transfer occurs. Therefore, trinuclear iron clusters (Fe3) are prepared to replace noble metal co-catalysts, promoting photogenerated electrons. - The transfer reduces itself to Fe(II) while simultaneously promoting the transfer of ∙O2. - The formation of Fe3 enables efficient degradation of TC. However, the instability of its structure due to changes in the valence state of Fe3 is a problem that urgently needs to be solved.

[0004] Compared to traditional heterojunctions, S-type heterojunctions overcome the problem of limited carrier transfer capability. Their internal electric field induces weak photogenerated carrier recombination, significantly preserving two types of strong photogenerated carriers. - and h + It exhibits excellent redox capabilities. Its unique layered composite material, due to its "face-to-face" contact form, is conducive to the formation of heterostructures and can provide a good attachment carrier for Fe3, which is expected to solve the problem of Fe3's own unstable valence state.

[0005] Furthermore, the two-dimensional graphitic carbon nitride (g-C3N4) in the S-type heterojunction is compatible with the band gap structure of the ZnIn2S4 nanosheets, and the two are in close contact to form an S-type heterojunction. Therefore, leveraging the synergistic advantages of the layered S-type ZnIn2S4 / g-C3N4 heterojunction support and the Fe3 cocatalyst holds promise for constructing a highly efficient photocatalytic system.

[0006] Finally, although photocatalytic degradation of tetracycline (TC) has great application potential, the limited dispersibility of solid photocatalysts in aqueous solutions inhibits their contact with organic substrates, significantly reducing the reaction rate. Ionic liquids (ILs), as "green solvents," can not only extract TC from the aqueous phase at room temperature and pressure, but also serve as a dispersion and stabilization system for photocatalytic reaction media and photocatalysts. Introducing ionic liquids into photocatalytic degradation systems is expected to improve the degradation efficiency of tetracycline. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for extraction coupled with photocatalytic degradation of environmental pollutants, and to solve the technical problem that the catalytic degradation efficiency of the tetracycline system in the existing technology needs to be further improved.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A method for extracting and coupling photocatalytic degradation of environmental pollutants, wherein the method uses a Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst as a photocatalyst and a [BMIM]PF6 ionic liquid as an extractant to treat environmental pollutants; wherein the environmental pollutant is tetracycline.

[0010] The method includes the following steps: dissolving tetracycline in a solvent to obtain a tetracycline solution; then adding [BMIM]PF6 ionic liquid to the tetracycline solution, stirring evenly, and performing ultrasonic extraction; after ultrasonic extraction, adding Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst, and performing photocatalytic degradation reaction under light irradiation.

[0011] The Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst is composed of Fe3 cocatalyst and ZnIn2S4 / g-C3N4S-type heterojunction support, with the Fe3 cocatalyst supported on the ZnIn2S4 / g-C3N4S-type heterojunction support; the ZnIn2S4 / g-C3N4S-type heterojunction support is composed of g-C3N4 nanosheets and ZnIn2S4 nanosheets, with the g-C3N4 nanosheets dispersed and attached to the ZnIn2S4 nanosheets.

[0012] The present invention also includes the following technical features:

[0013] Specifically, the conditions for ultrasonic extraction are: ultrasonic frequency of 40 kHz, ultrasonic power of 120 W, and ultrasonic time of 10 min.

[0014] Specifically, the illumination conditions are as follows: a 300W xenon lamp is used as the light source, and the wavelength of the light λ > 420nm.

[0015] Specifically, the photocatalytic degradation reaction takes 30 to 120 minutes.

[0016] Specifically, the mass concentration of the tetracycline solution is 33 mg / L, and the volume ratio of the tetracycline solution to the [BMIM]PF6 ionic liquid is 15:(5-10); 5 mg of Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst is added to every 15 mL of tetracycline solution.

[0017] Specifically, the solvent is a mixture of water and acetone, with a volume ratio of water to acetone of 2:1.

[0018] Specifically, the preparation method of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst includes: firstly, using urea as a raw material, g-C3N4 nanosheets are prepared; then, using iron salts, protonic acid salts, and protonic acid salts as raw materials, Fe3 cocatalyst is prepared; finally, using zinc salts, indium salts, and sulfur-containing compounds as raw materials, Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst is prepared.

[0019] Specifically, the preparation method of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst includes the following steps:

[0020] Step 1: Preparation of g-C3N4 nanosheets:

[0021] Urea was placed in a lidded crucible and kept at 540°C for 3 hours. After cooling, yellow blocky g-C3N4 was obtained. Then the lid of the lidded crucible was opened and kept at 500°C for 2 hours. After cooling, g-C3N4 nanosheets were obtained.

[0022] Step 2, Preparation of Fe3 co-catalyst:

[0023] Iron salts, protonic acid salts, and protonic acid were dissolved in water, and after standing for 7 days, black crystals were collected by filtration to obtain Fe3 co-catalyst.

[0024] Step 3: Preparation of Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst:

[0025] Zinc salt, indium salt, and sulfur-containing compound were dissolved in water with a pH of 2.5. Then, Fe3 cocatalyst prepared in step 2 and g-C3N4 nanosheets prepared in step 1 were added sequentially. After stirring evenly, the above mixed solution was placed in an 80 ℃ water bath for 2 h. The precipitated product was washed alternately with water and anhydrous ethanol, and then centrifuged, dried, and ground sequentially to obtain Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst.

[0026] Specifically, in step two, the iron salt is FeCl2•4H2O, the protic acid salt is sodium acetate, the protic acid is acetic acid, and the molar ratio of FeCl2•4H2O, sodium acetate, and acetic acid is 0.05:0.12:0.05.

[0027] Specifically, in step three, the zinc salt is ZnCl2, the indium salt is InCl3•4H2O, and the sulfur-containing compound is thioacetamide; the molar ratio of ZnCl2, InCl3•4H2O, and the sulfur-containing compound is 0.40:0.80:1.60; the mass ratio of ZnCl2, InCl3•4H2O, the sulfur-containing compound, Fe3 cocatalyst, and g-C3N4 nanosheets is 54.4:228.2:120:(10~50):40.

[0028] The beneficial technical effects of this invention compared to the prior art are as follows:

[0029] (I) This invention introduces ionic liquid into the photocatalytic system, which builds an "ionic liquid bridge" between the reactants and the photocatalyst, significantly improving the mass transfer effect in a short time. The extraction coupled photocatalytic efficiency reaches 83.83% within 60 min, which is 2.12 times that without extractant. When the light exposure time is extended to 120 min, the extraction coupled photocatalytic degradation rate increases to 90.5%.

[0030] (II) In the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst of the present invention, g-C3N4 nanosheets and ZnIn2S4 nanosheets are in close contact and form a ZnIn2S4 / g-C3N4 S-type heterojunction support. An internal electric field is formed inside the S-type heterojunction support, which accelerates the recombination of photoexcited carriers with low efficiency, thereby enabling the two strong photogenerating... - and h + The material retains its excellent redox capabilities. Meanwhile, the layered ZnIn2S4 / g-C3N4S heterojunction support is attached with a targeted trinuclear iron cluster (Fe3) cocatalyst, which not only endows the material with a larger specific surface area and abundant micropores, but also regulates the generation of tetracycline degradation active species. The two work synergistically to improve the degradation efficiency of tetracycline. Attached Figure Description

[0031] Figure 1 Scanning electron microscope (SEM) images of the g-C3N4 nanosheets prepared in Example 1, the ZnIn2S4 nanosheets prepared in Comparative Example 1, and the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst prepared in Example 1. Figure 1In the image: a is a scanning electron microscope (SEM) image of g-C3N4 nanosheets, b is a scanning electron microscope (SEM) image of ZnIn2S4 nanosheets, and c is a scanning electron microscope (SEM) image of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst.

[0032] Figure 2 This is a transmission electron microscope (TEM) image of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst prepared in Example 1. Figure 2 In the image: a is the lowest magnification transmission electron microscope (TEM) image, b is a relatively low magnification TEM image, and c is a high magnification TEM image.

[0033] Figure 3 The images show the STEM image and corresponding EDS spectrum of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst prepared in Example 1.

[0034] Figure 4 The diagram shows the average charge density difference and the S-type charge transfer mechanism of the ZnIn2S4 / g-C3N4 composite material; Figure 4 In the diagram: a is the average charge density difference diagram, and b is the S-type charge transfer mechanism diagram; the yellow area represents electron accumulation, and the cyan area represents electron depletion.

[0035] Figure 5 The image shows a comparison of the dark adsorption effects of the g-C3N4 nanosheets prepared in Example 1, the Fe3-ZnIn2S4 / g-C3N4 composite photocatalysts prepared in Examples 1 to 3, the ZnIn2S4 nanosheets prepared in Comparative Example 1, and the ZnIn2S4 / g-C3N4 S-type heterojunction supports prepared in Comparative Examples 2 to 4.

[0036] Figure 6 This is a comparison of the dark adsorption effects and photodegradation effects of the g-C3N4 nanosheets prepared in Example 1, the Fe3-ZnIn2S4 / g-C3N4 composite photocatalysts prepared in Examples 1 to 3, the ZnIn2S4 nanosheets prepared in Comparative Example 1, and the ZnIn2S4 / g-C3N4 S-type heterojunction supports prepared in Comparative Examples 2 to 4.

[0037] Figure 7 This is a comparison of the extraction effects of [BMIM]PF6 ionic liquid on tetracycline at different extraction times.

[0038] Figure 8 This is a schematic diagram illustrating the degradation of tetracycline under visible light irradiation in an extraction-coupled photocatalytic system.

[0039] The technical solution of the present invention will be further described below with reference to the embodiments. Detailed Implementation

[0040] The structural features of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst of the present invention are as follows: g-C3N4 nanosheets are dispersed and attached to 3D flower-like ZnIn2S4 nanosheets and tightly bonded together, generating a strong interfacial coupling effect to form a ZnIn2S4 / g-C3N4S-type heterojunction support. During the preparation process, pH control can prevent the self-aggregation of ZnIn2S4 nanosheets, allowing them to self-assemble into a 3D flower-like structure. Then, Fe3 cocatalyst is loaded onto the ZnIn2S4 / g-C3N4S-type heterojunction support, thus forming the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst.

[0041] The degradation mechanism of this invention is as follows: Figure 8 As shown, a π-π interaction exists between the [BMIM]PF6 imidazole ring and the tetracycline benzene ring, which promotes the extraction of tetracycline from solution into the ionic liquid (IL) phase. Then, under visible light excitation, the optimal-performing and stable Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst (FZCN-3) performs a photocatalytic degradation reaction of tetracycline. Ultimately, the tetracycline content in the IL phase decreases, breaking the extraction equilibrium and promoting the continuous entry of tetracycline from solution into the IL phase, forming a continuous extraction-coupled photocatalytic reaction system, thereby achieving the deep conversion of tetracycline.

[0042] It should be noted that all raw materials used in this invention, unless otherwise specified, are those known in the art. For example, the [BMIM]PF6 ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid) is a product known in the prior art, with CAS number 174501-64-5, preferably produced by Bide Pharmaceuticals, with catalog number BD32294, and a standard purity of 98%.

[0043] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0044] Example 1:

[0045] This embodiment provides a method for preparing a Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst, which specifically includes the following steps:

[0046] Step 1: Preparation of g-C3N4 nanosheets:

[0047] Urea was placed in a covered crucible and heated to 540°C at a heating rate of 2.5°C / min. The temperature was maintained for 3 hours and then cooled to room temperature to obtain yellow lumpy g-C3N4. The temperature was then increased at a rate of 1°C / min and maintained at 500°C with the lid off for 2 hours. After natural cooling, a light yellow flaky g-C3N4 powder product was obtained, which is g-C3N4 nanosheets (denoted as CN).

[0048] Step 2, Preparation of Fe III 2Fe II (μ3-O)(CH3CO2)6(H2O)3 cluster (Fe3 co-catalyst):

[0049] Dissolve 0.05 mol FeCl₂•4H₂O, 0.12 mol sodium acetate, and 0.05 mol acetic acid in 150 mL of deionized water. After standing for 7 days, filter and collect the black crystals, which is FeCl₂•4H₂O. III 2Fe II (μ3-O)(CH3CO2)6(H2O)3 cluster (denoted as Fe3).

[0050] Step 3: Preparation of Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst:

[0051] ZnCl2 (0.40 mmol, 54.4 mg), InCl3•4H2O (0.80 mmol, 228.2 mg), and thioacetamide (TAA, 1.60 mmol, 120 mg) were dissolved in 40 mL of deionized water (pH = 2.5). Then, 30 mg of Fe3 obtained in step two and 40 mg of CN obtained in step one were added sequentially. After stirring evenly, the mixture was placed in an 80 °C water bath for 2 h. The precipitate was washed alternately with deionized water and anhydrous ethanol, and then centrifuged, dried, and ground sequentially to obtain the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst (denoted as FZCN-3).

[0052] Example 2:

[0053] This embodiment provides a method for preparing a Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst, which is basically the same as that in Example 1, except that in step three, the amount of Fe3 added is 10 mg; the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst (denoted as FZCN-1) is finally obtained.

[0054] Example 3:

[0055] This embodiment provides a method for preparing a Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst, which is basically the same as that in Example 1, except that in step three, the amount of Fe3 added is 50 mg; the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst (denoted as FZCN-5) is finally obtained.

[0056] Comparative Example 1:

[0057] This comparative example provides a method for preparing ZnIn2S4 nanosheets. The method specifically includes the following steps: ZnCl2 (0.40 mmol), InCl3•4H2O (0.80 mmol), and thioacetamide (TAA, 1.60 mmol) are dissolved in 40 mL of deionized water (pH = 2.5). After stirring until homogeneous, the mixture is placed in an 80°C water bath for 2 h. The resulting precipitate is washed alternately with deionized water and anhydrous ethanol, then centrifuged, dried, and ground to finally obtain ZnIn2S4 nanosheets (denoted as ZIS).

[0058] Comparative Example 2:

[0059] This comparative example presents a method for preparing a ZnIn2S4 / g-C3N4S type heterojunction support, which specifically includes the following steps:

[0060] Step 1: Preparation of g-C3N4 nanosheets:

[0061] In this comparative example, step one is exactly the same as step one in Example 1.

[0062] Step 2, Preparation of ZnIn2S4 / g-C3N4S type heterojunction support:

[0063] ZnCl2 (0.40 mmol), InCl3•4H2O (0.80 mmol), and thioacetamide (TAA, 1.60 mmol) were dissolved in 40 mL of deionized water (pH = 2.5). Then, 20 mg of g-C3N4 nanosheets prepared in step one were added, and the mixture was stirred evenly. The mixture was then placed in an 80 °C water bath for 2 h. The precipitate was washed alternately with deionized water and anhydrous ethanol, centrifuged, dried, and ground to obtain a pale yellow solid product, which is the ZnIn2S4 / g-C3N4S-type heterojunction support (denoted as ZCN-2).

[0064] Comparative Example 3:

[0065] This comparative example provides a method for preparing a ZnIn2S4 / g-C3N4S-type heterojunction support, which is basically the same as that of Comparative Example 2, except that in step two, the amount of g-C3N4 nanosheets added is 40mg; finally, a ZnIn2S4 / g-C3N4S-type heterojunction support (denoted as ZCN-4) is obtained.

[0066] Comparative Example 4:

[0067] This comparative example provides a method for preparing a ZnIn2S4 / g-C3N4S-type heterojunction support, which is basically the same as that of Comparative Example 2, except that in step two, the amount of g-C3N4 nanosheets added is 60mg; finally, a ZnIn2S4 / g-C3N4S-type heterojunction support (denoted as ZCN-6) is obtained.

[0068] Material characterization and density functional theory calculation results for Example 1 and Comparative Examples 1 to 4:

[0069] (A) Figure 1 The microstructures of the g-C3N4 nanosheets (CN) prepared in Example 1, the ZnIn2S4 nanosheets (ZIS) prepared in Comparative Example 1, and the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst (FZCN-3) prepared in Example 1 are shown. Figure 1 As shown, ZIS nanosheets exhibit a 3D flower-like structure through self-assembly, preventing self-aggregation. Meanwhile, CN nanosheets attach to the ZIS nanoflowers, improving CN stacking and facilitating the formation of a stable heterostructure.

[0070] (B) Figure 2 The microstructure of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst (FZCN-3) prepared in Example 1 is shown, as follows: Figure 2 As shown, the presence of lattice fringes on the ZIS (102) reflective surface and the full face-to-face contact between ZIS and CN indicate the formation of an effective heterojunction interface, thereby promoting the efficiency of charge separation and migration.

[0071] (C) Figure 3 The elemental distribution of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst (FZCN-3) is shown, such as... Figure 3 As shown, the uniform distribution of C, N, Zn, In, S, Fe, and O elements in the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst confirms that ultra-small Fe3 is uniformly dispersed on the surface of the heterojunction, indicating that the present invention has successfully prepared the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst.

[0072] (D) Calculation and plotting using density functional theory (DFT) Figure 4This study reveals the average charge density difference diagram and S-type charge transfer mechanism of the ZnIn2S4 / g-C3N4 S-type heterojunction supports prepared in Comparative Examples 2 to 4. Figure 4 It is evident that the strong electron-electron interaction mainly occurs at the ZnIn2S4 / g-C3N4 interface, causing electrons (e - The electron spontaneously transfers from CN to ZIS, thereby generating an internal electric field pointing from CN to ZIS. Subsequently, the internal electric field induces photogenerated electrons in the conduction band of ZIS. - Photogenerated h in CN valence band + The combination forms an S-shaped heterojunction, and under the influence of the Fe metal sites, e is strongly reduced. - It is further transferred to Fe3 anchored on the ZCN surface.

[0073] Verification of the effects of Examples 1 to 3 and Comparative Examples 1 to 4:

[0074] (E) Dark Adsorption Experiment: 15 mg of g-C3N4 nanosheets prepared in Example 1, Fe3-ZnIn2S4 / g-C3N4 composite photocatalysts prepared in Examples 1 to 3, ZnIn2S4 nanosheets prepared in Comparative Example 1, and ZnIn2S4 / g-C3N4 S-type heterojunction supports prepared in Comparative Examples 2 to 4 were weighed and placed in 50 mL of tetracycline aqueous solution (50 mg / L). The mixtures were stirred in the dark for 30 min to reach adsorption equilibrium. The results were plotted... Figure 5 .

[0075] Depend on Figure 5 It can be seen that, under constant conditions, changing the composite ratio of binary or ternary composite materials results in different dark adsorption performance of the photocatalysts for tetracycline. The adsorption capacities of FZCN-3, FZCN-1, and FZCN-5 prepared in Examples 1, 2, and 3 are comparable, and all are higher than those of ZIS prepared in Comparative Example 1, CN prepared in Example 1, ZCN-4 prepared in Comparative Example 3, and ZCN-6 prepared in Comparative Example 4.

[0076] (F) Photocatalytic activity experiment: 15 mg of g-C3N4 nanosheets prepared in Example 1, Fe3-ZnIn2S4 / g-C3N4 composite photocatalysts prepared in Examples 1 to 3, ZnIn2S4 nanosheets prepared in Comparative Example 1, and ZnIn2S4 / g-C3N4 S-type heterojunction supports prepared in Comparative Examples 2 to 4 were weighed and placed in 50 mL of tetracycline aqueous solution (50 mg / L). A 300 W xenon lamp was used as the light source, and light below 420 nm was filtered out. The photocatalytic degradation reaction was carried out for 120 min under stirring conditions. The results were plotted. Figure 6 .

[0077] Depend on Figure 6It is evident that, under constant conditions, changing the composite ratio of binary or ternary composite materials results in different photocatalytic degradation performances of tetracycline. In the binary composite material, the ZCN-4 prepared in Comparative Example 3 exhibited the best photocatalytic degradation effect when 40 mg of CN was added. Subsequently, when 30 mg of Fe3 was further introduced using ZCN-4 as a support, the photocatalytic degradation effect of the ternary composite material FZCN-3 prepared in Example 1 was further enhanced.

[0078] Optimization of extraction time for tetracycline via ultrasonic extraction with ionic liquids:

[0079] Based on the above results, this invention determines that an extraction-coupled photocatalytic degradation system for tetracycline can be constructed based on the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst (denoted as FZCN-3) prepared in Example 1. Before constructing the system, it is necessary to determine the ultrasonic extraction time of the ionic liquid. This invention designs an optimization experiment for the ultrasonic extraction time of tetracycline, the specific process of which is as follows: Tetracycline (5 mg) is dissolved in 150 mL of a 2:1 volume ratio of deionized water / acetone (dispersant) mixed solvent to obtain a tetracycline solution (33 mg / L). Then, 15 mL of the tetracycline solution is extracted, and 7 mL of [BMIM]PF6 ionic liquid (extractant) is added to the 15 mL tetracycline solution. After stirring evenly, the solution is divided into four groups, and ultrasonically treated at a frequency of 40 kHz and a power of 120 W for 5 min, 10 min, 20 min, and 30 min, respectively. The experimental results are plotted... Figure 7 .

[0080] Depend on Figure 7 It can be seen that when other conditions are constant, the extraction performance of [BMIM]PF6 ionic liquid for tetracycline varies with the change of ultrasonic extraction time. When the ultrasonic extraction time is 10 min, the extraction rate reaches its peak, and then the extraction rate decreases with the extension of time. Therefore, this invention finally determined that 10 min is the time required for extraction equilibrium.

[0081] Example 4:

[0082] This embodiment provides a method for extraction coupled with photocatalytic degradation of environmental pollutants. The method uses the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst prepared in Example 1 as the photocatalyst and [BMIM]PF6 ionic liquid as the extractant to catalytically degrade tetracycline in the system.

[0083] The specific method is as follows: Tetracycline (5 mg) was dissolved in 150 mL of a 2:1 volume ratio of deionized water / acetone (dispersant) to prepare a tetracycline solution (33 mg / L); then 15 mL of the tetracycline solution was extracted, and 5 mL of [BMIM]PF6 ionic liquid (extractant) was added to the 15 mL tetracycline solution. After stirring evenly, the mixture was ultrasonicated at a frequency of 40 kHz and a power of 120 W for 10 min to reach extraction equilibrium. Subsequently, 5 mg of FZCN-3 photocatalyst was added, and a 300 W xenon lamp was used as the light source to filter out light below 420 nm. The photocatalytic degradation reaction was carried out for 120 min under stirring conditions.

[0084] In this embodiment, starting from 0.5 h of the photocatalytic degradation reaction, 3 mL of reaction solution was drawn every half hour, filtered through a 0.45 μm syringe filter, and the absorbance of the remaining tetracycline was analyzed using a ZY-902 UV-Vis spectrophotometer at the maximum absorption wavelength of 357 nm.

[0085] Example 5:

[0086] This embodiment provides a method for extraction coupled with photocatalytic degradation of environmental pollutants. This method is basically the same as that in Example 4, except that the amount of [BMIM]PF6 ionic liquid added is 7 mL.

[0087] Example 6:

[0088] This embodiment provides a method for extraction coupled with photocatalytic degradation of environmental pollutants. This method is basically the same as that in Example 4, except that the amount of [BMIM]PF6 ionic liquid added is 10 mL.

[0089] Comparative Example 5:

[0090] This comparative example provides a method for the single photocatalytic degradation of environmental pollutants, which is basically the same as that in Example 4, except that [BMIM]PF6 ionic liquid is not added.

[0091] Verification of the effects of Examples 4 to 6 and Comparative Example 5:

[0092] Table 1. Degradation performance of tetracycline by the extraction-coupled photocatalytic system

[0093]

[0094] As shown in Table 1, when other conditions are constant, changing the amount of ionic liquid alters the extraction-coupled photocatalytic degradation performance of tetracycline. When using 7 mL of [BMIM]PF6 ionic liquid (Example 7), the extraction-coupled photocatalytic system exhibits the best degradation performance for tetracycline, reaching 83.83% within 60 min, which is 2.12 times that without the extractant. When the illumination time is extended to 120 min, the extraction-coupled photocatalytic degradation rate increases to 90.5%.

Claims

1. A method of photocatalytic degradation of environmental pollutants coupled with extraction, characterized in that, The method adopts [BMIM]PF6 ionic liquid as an extractant, and adopts Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst as a photocatalyst to treat environmental pollutants; the environmental pollutants are tetracycline; The method comprises the following processes: dissolving tetracycline in a solvent to prepare a tetracycline solution; then adding [BMIM]PF6 ionic liquid to the tetracycline solution, stirring uniformly, and then performing ultrasonic extraction; after the ultrasonic extraction is completed, adding Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst, and performing a photocatalytic degradation reaction under light conditions.

2. The method for extraction coupled with photocatalytic degradation of environmental pollutants as described in claim 1, characterized in that, The ultrasonic extraction is performed at an ultrasonic frequency of 40 KHz, an ultrasonic power of 120 W, and an ultrasonic time of 10 min.

3. The method for extraction coupled with photocatalytic degradation of environmental pollutants as described in claim 1, characterized in that, The light condition is that a 300-watt xenon lamp is used as a light source, and the wavelength of light is λ>420 nm.

4. The method for extraction coupled with photocatalytic degradation of environmental pollutants as described in claim 1, characterized in that, The photocatalytic degradation reaction is performed for 30-120 min.

5. The method of photocatalytic degradation of environmental pollutants by extraction coupling as claimed in claim 1, wherein, The mass concentration of the tetracycline solution is 33 mg / L, the volume ratio of the tetracycline solution to the [BMIM]PF6 ionic liquid is 15:(5-10), and 5 mg of Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst is added to every 15 mL of the tetracycline solution.

6. The method of photocatalytic degradation of environmental pollutants by extraction coupling according to claim 1, characterized in that, The solvent is a mixed solvent of water and acetone, and the volume ratio of water to acetone is 2:

1.

7. The method for extraction coupled with photocatalytic degradation of environmental pollutants as described in claim 1, characterized in that, The Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst is composed of Fe3 cocatalyst and ZnIn2S4 / g-C3N4 S-type heterojunction carrier, and the Fe3 cocatalyst is loaded on the ZnIn2S4 / g-C3N4 S-type heterojunction carrier; the ZnIn2S4 / g-C3N4 S-type heterojunction carrier is composed of g-C3N4 nanosheets and ZnIn2S4 nanosheets, and the g-C3N4 nanosheets are dispersed and attached on the ZnIn2S4 nanosheets.

8. The method for extraction coupled with photocatalytic degradation of environmental pollutants as described in claim 1, characterized in that, The preparation method of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst comprises the following steps: first, preparing g-C3N4 nanosheets by using urea as a raw material; then, preparing Fe3 cocatalyst by using iron salt, proton acid salt and proton acid as raw materials; and finally, preparing Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst by using zinc salt, indium salt and sulfur-containing compound as raw materials.

9. The method for extraction coupled with photocatalytic degradation of environmental pollutants as described in claim 7, characterized in that, The preparation method of the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst comprises the following steps: Step one, preparing g-C3N4 nanosheets: Put urea into a covered crucible, keep it at 540℃ for 3 h, cool it down, and then take out yellow block-shaped g-C3N4; then open the cover of the crucible, keep it at 500℃ for 2 h, cool it down, and then prepare g-C3N4 nanosheets; Step two, preparing Fe3 cocatalyst: Dissolve iron salt, proton acid salt and proton acid in water, stand for 7 days, filter and collect black crystals, and then obtain Fe3 cocatalyst; Step three, preparing Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst: The zinc salt, the indium salt and the sulfur-containing compound are dissolved in water with a pH value of 2.5, and then the Fe3 cocatalyst prepared in step two and the g-C3N4 nanosheet prepared in step one are added in sequence. After stirring uniformly, the above mixed solution is placed in a water bath at 80 ℃ for reaction for 2 h. After the obtained precipitated product is washed with water and anhydrous ethanol alternately, centrifugation, drying and grinding are carried out in sequence to prepare the Fe3-ZnIn2S4 / g-C3N4 composite photocatalyst.

10. The method of claim 9, wherein the extraction-coupled photocatalytic degradation of environmental pollutants is carried out in the presence of a magnetic field. In step two, the iron salt is FeCl2·4H2O, the protonic acid salt is sodium acetate, and the protonic acid is acetic acid. The molar ratio of FeCl2·4H2O, sodium acetate and acetic acid is 0.05:0.12:0.

05. In step three, the zinc salt is ZnCl2, the indium salt is InCl3·4H2O, and the sulfur-containing compound is thioacetamide. The mass ratio of ZnCl2, InCl3·4H2O, the sulfur-containing compound, the Fe3 cocatalyst and the g-C3N4 nanosheet is 54.4:228.2:120:(10-50):40.

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