Functional film for removing aflatoxin B1 through photocatalysis as well as preparation method and application of functional film

Abstract

The invention belongs to the technical field of food harmful pollutant control and photocatalytic film materials, and particularly relates to a functional film for removing aflatoxin B1 through photocatalysis as well as a preparation method and application of the functional film. According to the preparation method of the functional film for removing the aflatoxin B1 through photocatalysis, a stainless steel net is used as a substrate, a polyimide / silver phosphotungstate photocatalyst (MPI) is used as an active component, polyvinylidene fluoride (PVDF) is used as a polymer matrix, and the functional film with the performance of degrading the AFB1 through visible light catalysis is prepared by fixing the PVDF and the MPI on the stainless steel net. The prepared functional film has a porous network structure, the powder catalyst MPI is uniformly dispersed in the network structure of PVDF, agglomeration of MPI can be inhibited, the defect that the AFB1 adsorption capacity is reduced due to the fact that active sites of the material are covered is overcome, and the functional film has excellent performance of visible light catalytic degradation of aflatoxin B1 at normal temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of food harmful pollutant control and photocatalytic film materials, and specifically relates to a functional film for photocatalytically removing aflatoxin B1, a preparation method and an application thereof. Background Art

[0002] Aflatoxin B1 (AFB1) is a highly toxic and carcinogenic fungal toxin that often contaminates edible oils such as peanut oil, corn oil, rice bran oil and other agricultural products, posing a serious threat to human health. Currently, common methods for removing AFB1 from oils and fats include physical adsorption (such as activated carbon, clay), chemical degradation (such as ozone oxidation, alkali treatment) and biodegradation (such as microbial degradation). However, these methods have obvious disadvantages, such as physical adsorption may cause loss of oil nutrients and the adsorbent is difficult to regenerate; chemical degradation is prone to introduce secondary pollution or change the quality of the oil; biodegradation efficiency is low and the stability is poor. In contrast, photocatalytic technology has shown significant advantages. It can efficiently degrade AFB1 under mild conditions without destroying the nutritional components of the oil and fat and leaving no harmful residues. The catalyst is reusable, and it is both green and environmentally friendly and energy-efficient, providing a new solution for the detoxification technology of edible oils such as peanut oil.

[0003] Photocatalytic technology typically uses powdered photocatalysts as its core active component. Powdered photocatalysts are simple to prepare and have a high active component content. However, powdered catalysts are often difficult to separate from the system, making their recovery and reuse difficult and potentially causing secondary food contamination. Meanwhile, photocatalytic functional films, by immobilizing the active components onto a substrate material, enable rapid separation and recycling, reducing catalyst waste and costs, and lowering environmental pollution risks. This is of great significance for continuous catalytic reactions and industrialized continuous production applications.

[0004] However, when constructing a photocatalytic functional film, in order to achieve uniform dispersion of the powdered catalyst, it is inevitable to introduce a dispersion medium such as various dispersion solvents or dispersion matrix materials. Although the use of the dispersion medium can improve the processing convenience and film uniformity of the thin film catalyst material, the dispersion solvent is prone to waste gas pollution after use, which has an impact on the environment. At the same time, the dispersion solvent is easily heated to cause discoloration and cross-linking, which affects the mechanical properties of the film. While the dispersion matrix material and the catalytic material can form a composite layer with higher strength after compounding, the matrix material is easy to cover the active sites of the catalytic material after use, thereby causing a significant deterioration in the catalyst's ability to remove AFB1. Therefore, for the efficient removal of AFB1 in oil and fat systems, no method for constructing a suitable functional photocatalytic thin film material has been reported in the prior art.

[0005] Therefore, how to develop a functional photocatalytic film for removing AFB1 from oils and fats, which can not only inhibit the agglomeration of powder catalysts and promote recovery and separation, but also significantly improve the photocatalytic performance of the material to obtain excellent AFB1 removal ability, has become a technical problem to be solved urgently in the present invention. Summary of the Invention

[0006] In response to the above-mentioned problems, the present invention aims to provide a functional film for photocatalytically removing aflatoxin B1, as well as its preparation method and application. The present invention uses a stainless steel mesh as a substrate, a polyimide / silver phosphotungstate photocatalyst as an active component, and polyvinylidene fluoride as a polymer matrix to produce a functional film with visible light catalytic degradation of AFB1. The functional film for photocatalytically removing aflatoxin B1 prepared by the present invention can solve the problem of powder catalyst being difficult to recycle and causing secondary pollution during photocatalytic degradation of aflatoxin B1. In particular, it can solve the problem of a significant decrease in AFB1 removal ability caused by the covering of catalytic active sites after the preparation of existing films.

[0007] To achieve the above object, the first aspect of the present invention adopts the following technical solution:

[0008] A method for preparing a functional film for photocatalytic removal of aflatoxin B1 comprises the following steps:

[0009] The polyimide / silver phosphotungstate photocatalyst is mixed with a polymer matrix solution, then coated on a substrate and dried to obtain the functional film for photocatalytic removal of aflatoxin B1; wherein the substrate is a stainless steel mesh; and the polymer matrix used in the polymer matrix solution is polyvinylidene fluoride.

[0010] In order to improve the removal efficiency of the functional film for aflatoxin B1, as a preferred solution, the mass ratio of the polyimide / silver phosphotungstate photocatalyst to the polymer matrix solution is 1:(2-6), more preferably 1:(2-5), and most preferably 1:2.

[0011] As a preferred solution, the polymer matrix solution is prepared by dissolving a polymer matrix in an organic solvent; the organic solvent is N,N-2-methylacetamide; the mass concentration of the polymer matrix solution is 8% to 12%, more preferably 10%.

[0012] As a preferred solution, the preparation method of the polyimide / phosphotungstic acid silver photocatalyst includes the following steps: reacting phosphotungstic acid and melamine in water, adding a water-soluble silver salt solution for self-assembly after the reaction, and performing solid-liquid separation after the self-assembly; washing the solid obtained by the solid-liquid separation and mixing it with pyromellitic anhydride, performing a solid-phase thermal polymerization reaction, and finally grinding to obtain the polyimide / phosphotungstic acid silver photocatalyst.

[0013] As a further preferred embodiment, the phosphotungstic acid solution and melamine are reacted in water by adding the phosphotungstic acid solution to the melamine solution for reaction; the molar ratio of the phosphotungstic acid, melamine, and silver ions in the water-soluble silver salt solution is 1:(3-8):(1-3); the melamine solution is obtained by dissolving melamine in water, and the concentration of the melamine solution is 0.05-0.30 mol / L; the phosphotungstic acid solution is obtained by dissolving phosphotungstic acid in water, and the concentration of the phosphotungstic acid solution is 0.05-0.30 mol / L; the concentration of silver ions in the water-soluble silver salt solution is 0.20-1.10 mol / L; the reaction time is 0.5-4 h; the self-assembly time is 0.5-4 h; the temperature of the solid-phase thermal polymerization reaction is 300-350° C., and the time is 3-6 h.

[0014] As a further preferred solution, the mixing is stirring mixing, and the mixing time is 5 to 60 minutes; the coating is one of brushing, scraping, and spin coating; the drying temperature is 40 to 110° C., and the drying time is 0.5 to 5 hours.

[0015] As a preferred solution, the area of the substrate is 1 to 280 cm 2 The pore size of the substrate is 150 to 830 μm; the substrate is pre-cleaned and dried before coating; every 10 to 15 cm 2 The amount of the polyimide / silver phosphotungstate photocatalyst used is 0.6 to 1.4 g. Further preferably, the pore size of the substrate is 150 to 180 μm.

[0016] The second aspect of the present invention adopts the following technical solution:

[0017] A functional film for photocatalytically removing aflatoxin B1 prepared by the above preparation method.

[0018] The third aspect of the present invention adopts the following technical solution:

[0019] An application of the functional film for photocatalytically removing aflatoxin B1 is the application of the functional film for photocatalytically removing aflatoxin B1 in photocatalytically removing aflatoxin B1 from oil samples.

[0020] As a preferred solution, the photocatalytic removal is a photocatalytic reaction carried out under visible light with a wavelength of λ≥420nm; the oil sample is one or more of peanut oil, corn oil, and rice bran oil.

[0021] The technical solution of the present invention has the following advantages and beneficial effects:

[0022] The preparation method of the functional film for photocatalytic removal of aflatoxin B1 provided by the present invention is mixed with polyimide / silver phosphotungstate photocatalyst (MPI) by polyvinylidene fluoride (PVDF), so that MPI is fixed on a stainless steel mesh to prepare a functional film with visible light catalytic degradation of AFB1 performance. In the preparation method of the present invention, stainless steel mesh is used as a substrate, polyimide / silver phosphotungstate photocatalyst is used as an active component, and polyvinylidene fluoride is used as a polymer matrix. The prepared photocatalytic functional film has a porous network structure and a large specific surface area. At the same time, the powder catalyst MPI is evenly dispersed in the network structure of PVDF, suppresses the agglomeration of MPI, and is especially capable of promoting the separation of photogenerated carriers, making up for the defect that the material active site is covered and causes the adsorption capacity of AFB1 to decrease. At the same time, the present invention adopts PVDF as a composite film prepared by the polymer matrix, and its charge transfer rate and photoelectric conversion efficiency are significantly enhanced.

[0023] Therefore, the functional film for photocatalytic removal of aflatoxin B1 prepared by the present invention has advantages such as uniform component dispersion and close contact, easy recycling, no secondary pollution, and reusability. In particular, the functional film of the present invention has excellent visible light catalytic degradation performance of aflatoxin B1 at room temperature. Compared with existing photocatalysts such as polyimide / silver phosphotungstate, polyimide, carbon nitride, and titanium dioxide, it has high photocatalytic efficiency, simple operation, easy recycling, and no secondary pollution. At the same time, the preparation process of the present invention is simple and suitable for large-scale industrial production. It has broad application prospects and practical application value in the field of aflatoxin B1 degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope (SEM) image of the functional film (MPDF) for photocatalytic removal of aflatoxin B1 prepared in Example 1 of the present invention;

[0025] Figure 2 This is a transmission electron microscope (TEM) image of the functional film (MPDF) for photocatalytic removal of aflatoxin B1 prepared in Example 1 of the present invention;

[0026] Figure 3 X-ray diffraction (PXRD) patterns of the functional films (MPDF, MPVP, MPSP, MPVA) and the powder catalyst (MPI) for photocatalytic removal of aflatoxin B1 prepared in Example 1 of the present invention and Comparative Examples 1 to 3;

[0027] Figure 4 Fourier transform infrared spectroscopy (FTIR) of the functional films (MPDF, MPVP, MPSP, MPVA) and the powder catalyst (MPI) for photocatalytic removal of aflatoxin B1 prepared in Example 1 of the present invention and Comparative Examples 1 to 3;

[0028] Figure 5 The UV-Vis DRS graphs are of the functional films (MPDF, MPVP, MPSP, MPVA) and the powder catalyst (MPI) for photocatalytic removal of aflatoxin B1 prepared in Example 1 of the present invention and Comparative Examples 1 to 3;

[0029] Figure 6 The degradation rate and rate constant test results of aflatoxin B1 by the functional films for photocatalytic removal of aflatoxin B1 according to Examples 1 to 5 of the present invention are shown;

[0030] Figure 7 The degradation rate and rate constant test results of aflatoxin B1 by the functional films for photocatalytic removal of aflatoxin B1 in Examples 1 and 6 to 9 of the present invention are shown;

[0031] Figure 8 The test results of the recycling ability of the functional film for photocatalytic removal of aflatoxin B1 in Example 1 of the present invention for degradation of AFB1 are shown;

[0032] Figure 9 These are the test results of the degradation rate of aflatoxin B1 by the functional film (MPDF) for photocatalytic removal of aflatoxin B1 according to Example 1 of the present invention, the existing powder catalyst polyimide (PI-325), the powder catalyst carbon nitride (GCN), and the powder catalyst titanium dioxide (P25). DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clear, the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the raw materials used, unless otherwise specified, are all commonly used in the art, available to the public or commercially available.

[0035] Melamine, pyromellitic anhydride, silver nitrate, phosphotungstic acid, potassium carbonate, and other reagents used in the following embodiments of the present invention were all commercially available analytical grade reagents. Polyvinylidene fluoride (PVDF), polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), and polystyrene (PSP) were all injection molding grade and purchased from Tianjin Xiens Biochemical Technology Co., Ltd. Stainless steel mesh (food grade) was sourced from Haoquan Sieve Factory in Shangyu District, Shaoxing City, with a pore size of 150 to 830 μm.

[0036] The present invention provides a method for preparing a functional film for photocatalytic removal of aflatoxin B1, comprising the following steps:

[0037] The polyimide / silver phosphotungstate photocatalyst is mixed with a polymer matrix solution, then coated on a substrate and dried to obtain a functional film for photocatalytic removal of aflatoxin B1; wherein the substrate is a stainless steel mesh; and the polymer matrix used in the polymer matrix solution is polyvinylidene fluoride.

[0038] In order to improve the removal efficiency of the functional film for aflatoxin B1, preferably, the mass ratio of the polyimide / silver phosphotungstate photocatalyst to the polymer matrix solution is 1:(2-6), more preferably 1:(2-5), and most preferably 1:2.

[0039] Furthermore, the polymer matrix solution is prepared by dissolving the polymer matrix in an organic solvent; the organic solvent is N,N-2-methylacetamide; and the mass concentration of the polymer matrix solution is 8% to 12%, more preferably 10%.

[0040] The polyimide / silver phosphotungstic acid photocatalyst used in the present invention can be prepared independently with reference to the prior art CN117299210A and is not particularly limited in the present invention. Furthermore, the preparation method of the polyimide / silver phosphotungstic acid photocatalyst comprises the following steps: reacting phosphotungstic acid and melamine in water, adding a water-soluble silver salt solution to self-assemble after the reaction, and performing solid-liquid separation after the self-assembly; washing the solid obtained from the solid-liquid separation, mixing it with pyromellitic anhydride, performing a solid-phase thermal polymerization reaction, and finally grinding to obtain the polyimide / silver phosphotungstic acid photocatalyst.

[0041] Furthermore, the phosphotungstic acid solution and melamine are reacted in water by adding the phosphotungstic acid solution to the melamine solution for reaction. The molar ratio of phosphotungstic acid, melamine, and silver ions in the water-soluble silver salt solution is 1:(3-8):(1-3), more preferably 1:5:2. The melamine solution is obtained by dissolving melamine in water, and the concentration of the melamine solution is 0.05-0.30 mol / L, more preferably 0.085 mol / L. The phosphotungstic acid solution is obtained by dissolving phosphotungstic acid in water, and the concentration of the phosphotungstic acid solution is 0.05-0.30 mol / L, more preferably 0.085 mol / L. The concentration of silver ions in the water-soluble silver salt solution is 0.20-1.10 mol / L, more preferably 0.34 mol / L.

[0042] Furthermore, the reaction time is 0.5 to 4 hours, more preferably 3 hours. The self-assembly time is 0.5 to 4 hours, more preferably 2 hours. The solid-phase thermal polymerization reaction temperature is 300 to 350°C, and the time is 3 to 6 hours. More preferably, the solid-phase thermal polymerization reaction temperature is 325°C, and the time is 4 hours.

[0043] Furthermore, the molar amount of pyromellitic anhydride is the same as the molar amount of melamine.

[0044] Furthermore, the washing step is performed by first washing with hot water and then washing with ethanol. The temperature of the hot water is ≥ 50°C. More preferably, the number of hot water washes is 3 or more, and the number of ethanol washes is 3 or more. Preferably, the rate of heating to the solid-phase thermal polymerization reaction temperature is 2 to 20°C / min.

[0045] More specifically, the polyimide / silver phosphotungstate photocatalyst used in the following examples, comparative examples, and test examples of the present invention was prepared with reference to the prior art CN117299210A, and the specific steps are as follows:

[0046] 1) Disperse 0.0085 mol of melamine in 100 mL of deionized water and magnetically stir in a 90°C oil bath for 30 minutes to obtain a uniform melamine solution. Dissolve 0.0017 mol of phosphotungstic acid in 20 mL of water to obtain a phosphotungstic acid solution. Add the phosphotungstic acid solution dropwise to the melamine solution and continue stirring for 3 hours to obtain a suspension. Subsequently, add 10 mL of an aqueous solution containing 0.0034 mol of silver nitrate dropwise to the suspension. After stirring for 2 hours, immediately filter the precipitate, wash it three times with 70°C hot water, then three times with ethanol, dry it in an oven at 80°C for 12 hours, and grind it to obtain a yellow-green powder.

[0047] 2) 0.0085 mol of pyromellitic anhydride was ground with the yellow-green powder for 30 minutes to obtain a solid-phase thermal polymerization precursor. The solid-phase thermal polymerization precursor was placed in a semi-enclosed porcelain crucible and transferred to a muffle furnace. Under ambient air pressure, the temperature was increased from room temperature to 325°C at a rate of 10°C / min and held for 4 hours to obtain a dark yellow powder. Further grinding was performed to obtain a powdered polyimide / silver phosphotungstate photocatalyst, designated as MPI.

[0048] In the preparation method of the present invention, mixing is performed by stirring for 5 to 60 minutes, more preferably 10 minutes. Coating is performed by brushing, knife coating, or spin coating, more preferably brushing. The brushing process ensures the flatness of the film and uniformly disperses the MPI in the PVDF network structure. The drying temperature is 40 to 110° C., and the drying time is 0.5 to 5 hours.

[0049] Furthermore, the area of the substrate is 1 to 280 cm 2 The pore size of the substrate is 150 to 830 μm. More preferably, the pore size of the substrate is 150 to 180 μm. 2 The substrate has a corresponding amount of polyimide / silver phosphotungstate photocatalyst of 0.6 to 1.4 g.

[0050] Furthermore, the substrate is pre-cleaned and dried before coating. The present invention does not impose any particular restrictions on the cleaning and drying process. Technicians can routinely adjust the cleaning and drying process parameters, as long as the surface of the resulting substrate is free of oil and impurities and meets the film preparation requirements. For example, in the following embodiments and comparative examples of the present invention, the substrate used is a stainless steel mesh, which needs to be cleaned and dried before use. The specific steps are: 2 The stainless steel mesh was repeatedly washed five times with water containing detergent, then placed in anhydrous ethanol for ultrasonic oscillation for 15 minutes, then placed in deionized water for ultrasonic oscillation for 10 minutes, and then placed in a blast drying oven at 80°C to obtain a stainless steel base for standby use.

[0051] Furthermore, when the functional film for photocatalytic removal of aflatoxin B1 is used to photocatalytically remove aflatoxin B1 from oil samples, the light power density of the photocatalytic removal is 100 to 2000 mW / cm 2 , for example, 1300 mW / cm 2 .

[0052] Furthermore, when performing photocatalytic removal of aflatoxin B1, the functional film for photocatalytic removal of aflatoxin B1 is added to an oil-water mixture containing aflatoxin B1 and stirred to form a suspension. The suspension is then exposed to a light source to perform a photocatalytic removal reaction. For example, when the concentration of aflatoxin B1 in the oil-water mixture is 200 μg / kg, the photocatalytic removal reaction lasts for 20 to 100 minutes.

[0053] Example 1

[0054] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0055] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 150 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0056] (2) 3.36 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 0.84 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 4:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The mixture was dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 4-MPDF-1, or MPDF).

[0057] Example 2

[0058] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0059] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 150 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0060] (2) 2.8 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 1.4 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 2:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The film was dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 2-MPDF-1).

[0061] Example 3

[0062] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0063] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 150 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0064] (2) 3.15 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 1.05 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 3:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The mixture was dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 3-MPDF-1).

[0065] Example 4

[0066] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0067] (1) The area is 12.25cm 2A stainless steel mesh (pore size 150 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0068] (2) 3.5 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 0.7 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 5:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The film was dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 5-MPDF-1).

[0069] Example 5

[0070] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0071] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 150 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0072] (2) 3.6 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 0.6 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 6:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The film was dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 6-MPDF-1).

[0073] Example 6

[0074] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0075] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 830 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0076] (2) 3.36 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 0.84 g of powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 minutes (the mass ratio of the polymer matrix solution to MPI was 4:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The mixture was dried in a forced air drying oven (80°C) for 1 hour to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 4-MPDF-830).

[0077] Example 7

[0078] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0079] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 380 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0080] (2) 3.36 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 0.84 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 4:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The mixture was dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 4-MPDF-380).

[0081] Example 8

[0082] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0083] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 250 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0084] (2) 3.36 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 0.84 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 4:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The film was dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 4-MPDF-250).

[0085] Example 9

[0086] This embodiment provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0087] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 180 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0088] (2) 3.36 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, the solvent is N,N-2-methylacetamide) and 0.84 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 4:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1). The mixture was dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this embodiment (denoted as 4-MPDF-180).

[0089] Comparative Example 1

[0090] This comparative example provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0091] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 150 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0092] (2) 3.36 g of a 10% mass fraction polyvinylpyrrolidone solution (PVP, the solvent is N,N-2-methylacetamide) and 0.84 g of a powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 4:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1), and dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this comparative example (denoted as MPVP).

[0093] Comparative Example 2

[0094] This comparative example provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0095] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 150 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0096] (2) 3.36 g of 10% by mass polyvinyl alcohol (PVA, solvent: N,N-2-methylacetamide) and 0.84 g of powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 4:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1), and dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this comparative example (denoted as MPVA).

[0097] Comparative Example 3

[0098] This comparative example provides a functional film for photocatalytically removing aflatoxin B1, and a preparation method thereof comprises the following steps:

[0099] (1) The area is 12.25cm 2 A stainless steel mesh (pore size 150 μm) was cleaned to remove oil and impurities on the surface, and then placed in a forced air drying oven at 80° C. to obtain a stainless steel substrate.

[0100] (2) 3.36 g of 10% by mass polystyrene (PSP, solvent: N,N-2-methylacetamide) and 0.84 g of powdered polyimide / silver phosphotungstate photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of the polymer matrix solution to MPI was 4:1), and then evenly brushed onto one surface of the stainless steel substrate obtained in step (1), and dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1 in this comparative example (denoted as MPSP).

[0101] Test Example 1: Thin Film Micromorphology and Structure Analysis

[0102] The microscopic morphology of the functional film (MPDF) for photocatalytic removal of aflatoxin B1 prepared in Example 1 was observed using a SU-8020 field emission scanning electron microscope and a Tecnai G2 F20 field emission transmission electron microscope. The scanning electron microscope (SEM) and transmission electron microscope (TEM) images obtained are shown in FIG. Figure 1 and Figure 2 shown.

[0103] Combine Figure 1 and Figure 2 It can be seen that the functional film for photocatalytic removal of aflatoxin B1 prepared in Example 1 is a porous network structure of stacked planar layers, and the polyimide / silver phosphotungstate powder catalyst MPI is uniformly dispersed on the surface of the film.

[0104] Further, a D8 Advance X-ray diffractometer was used with a Cu target Kα ray as the X-ray source to analyze the crystal structures of the functional films (MPDF, MPVP, MPVA, MPSP) for photocatalytic removal of aflatoxin B1 prepared in Example 1 and Comparative Examples 1 to 3 and the powdered polyimide / silver phosphotungstate photocatalyst (MPI). The obtained X-ray diffraction (PXRD) results are as follows: Figure 3 A Bruker Tensor II Fourier transform infrared spectrometer was used to analyze the chemical functional groups of the functional films (MPDF, MPVP, MPVA, MPSP) for photocatalytic removal of aflatoxin B1 prepared in Example 1 and Comparative Examples 1 to 3, as well as the powdered polyimide / silver phosphotungstate photocatalyst (MPI), with a scanning range of 400 to 4000 cm -1 The Fourier transform infrared spectroscopy (FTIR) results are as follows: Figure 4 shown.

[0105] Combine Figure 3 and Figure 4 The results showed that after the polymer matrix and powder catalyst MPI were immobilized on the stainless steel mesh substrate, no new diffraction peaks and chemical structure information appeared, indicating that the composite process of the photocatalytic functional film was non-covalent bonding.

[0106] The light absorption properties of the functional films (MPDF, MPVP, MPVA, MPSP) for photocatalytic removal of aflatoxin B1 prepared in Example 1 and Comparative Examples 1 to 3 and the powdered polyimide / silver phosphotungstate photocatalyst (MPI) were further analyzed using an Analytikjena Specord 200 UV-visible spectrophotometer with BaSO4 as a reference. The measurement range was 200 to 800 nm. The results are as follows: Figure 5 shown.

[0107] Depend on Figure 5 As can be seen, compared to Comparative Examples 1-3 and the powder catalyst, the functional film for photocatalytic aflatoxin B1 removal provided by Example 1 of the present invention has the highest visible light absorption area and the best visible light absorption performance. This indicates that by using polyvinylidene fluoride as the polymer matrix, the present invention significantly increases the light absorption intensity of the powder catalyst in the visible light region, significantly improving visible light absorption and utilization, thereby enhancing its photocatalytic activity.

[0108] Test Example 2: Aflatoxin B1 Removal Effect Test

[0109] 12.25cm 2 The functional film for photocatalytic removal of aflatoxin B1 prepared in Examples 1 to 9 or Comparative Examples 1 to 3 was placed in 30 mL of an oil-water mixture solution containing 200 μg / kg aflatoxin B1 (in the oil-water mixture, peanut oil: water = 7:3, v / v), and the resulting suspension was placed in the dark and magnetically stirred for 30 minutes to reach adsorption-desorption equilibrium. Then, a photocatalytic reaction was carried out under visible light with a wavelength of λ ≥ 420 nm (the optical power density was about 1300 mW / cm 2 ), working current 15A. After the reaction reaches the predetermined time, take 3mL of the reaction solution as a sample. Weigh 2.0g of the sample into a 50mL centrifuge tube, add 1.0g of NaCl and 25mL of methanol-water mixture (V 甲醇 :V 水 =7:3), vortexed for 20 minutes, and centrifuged at 7000 rpm for 5 minutes. After centrifugation, the extract was aspirated and filtered. 15 mL of the filtrate was diluted and mixed with 30 mL of deionized water. The mixture was filtered through glass fiber filter paper one to two times until the filtrate was clear. 15 mL of the filtrate was transferred into a 20 mL syringe. A CNW aflatoxin B1 immunoaffinity column (Shanghai Anpu Technology Co., Ltd.) was connected to the lower end of the syringe. The column was rinsed with water twice, 10 mL each time, and all the effluent was discarded until air had passed through the column. 2 mL of methanol was added for elution. The entire eluate was collected, purged with nitrogen, and re-dissolved in 2 mL of methanol for high-performance liquid chromatography analysis of aflatoxin B1 content. The photocatalytic reaction time was set to 100 minutes, and the aflatoxin B1 content in the samples after the photocatalytic reaction was analyzed.

[0110] The specific conditions for HPLC were as follows: an InertSustain C18 column (4.6×250 mm, 5 μm particle size); an HPLC instrument equipped with a fluorescence spectrometer detector with an excitation wavelength of 365 nm and an emission wavelength of 436 nm; a mobile phase consisting of an acetonitrile / methanol / water mixture with a volume ratio of 22.5:22.5:55, a flow rate of 0.5 mL / min, and an injection volume of 10 μL.

[0111] Calculation of the degradation rate and rate constant of aflatoxin B1: Taking the change in the AFB1 content in the reaction sample as an indicator, the degradation rate is calculated as follows: Degradation rate = (1-c / c0) × 100%, where c is the AFB1 concentration in the sample at reaction time t, μg·L -1 ; c0 is the initial concentration of AFB1 before the reaction, μg·L -1 The photocatalytic degradation rate constant k of AFB1 was obtained by fitting the pseudo-first-order kinetic equation: -ln(c / c0)=kt+b, where t is the reaction time, h; c is the AFB1 concentration in the sample at reaction time t, μg·L -1 ; c0 is the initial concentration of AFB1 before the reaction, μg·L -1 ; k is the reaction rate constant, h -1 .

[0112] A powdered polyimide / silver phosphotungstate photocatalyst (MPI) was used as a control to determine the degradation rate and rate constant of aflatoxin B1. The mass of the powdered catalyst used in the MPI test remained consistent with the mass of the MPI raw material contained in the functional film material described above. Other testing conditions were the same as those used for the functional film processing.

[0113] Among them, the photocatalytic removal of aflatoxin B1 functional films of Examples 1 to 5 have the following degradation rates and rate constants for aflatoxin B1 when irradiated for 0, 25, 50, 75, and 100 minutes: Figure 6 As shown (the upper figure is the degradation rate, the lower figure is the rate constant). The degradation rate and rate constant of aflatoxin B1 of the functional film of Example 1 and Examples 6 to 9 for photocatalytic removal of aflatoxin B1 at 0, 25, 50, 75, and 100 minutes of light irradiation are as follows: Figure 7 Table 1 shows the degradation rates and rate constants of aflatoxin B1 obtained by the functional films prepared in Examples 1 to 9 and Comparative Examples 1 to 3, and the powdered polyimide / silver phosphotungstate photocatalyst (MPI) after 100 minutes of illumination (the upper figure shows the degradation rate, and the lower figure shows the rate constant).

[0114] Table 1. Degradation rate and rate constant of photocatalytic degradation of AFB1

[0115]

[0116] Combined with Table 1 Figure 6 、 Figure 7 It can be seen that compared with the functional films prepared in Comparative Examples 1 to 3 using polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), and polystyrene (PSP) as polymer matrices, Example 1 of the present invention uses polyvinylidene fluoride as the polymer matrix. After compounding with polyimide / silver phosphotungstate powder catalyst, it can effectively make up for the defect of covered catalytic active sites and promote a significant improvement in the degradation rate of AFB1. The degradation rate of aflatoxin B1 after 100 minutes of illumination is 55.38%, and the rate constant is 0.3408h -1 , essentially reaching the catalytic level of a powder catalyst. Furthermore, a comparison of Examples 2 and 3 with the powder catalyst shows that when the ratio of polymer matrix solution to MPI is 2-3:1, the degradation rate of aflatoxin B1 after 100 minutes of illumination is significantly superior to that of the powder catalyst MPI, achieving superior aflatoxin B1 degradation. Furthermore, a comparison of Example 1 with Examples 6-9 shows that the optimal aflatoxin B1 degradation effect is achieved when the pore size of the stainless steel mesh is 150 μm. However, pore sizes below 150 μm are less effective due to the reduced strength of the stainless steel mesh, making it unsuitable for film use. Therefore, stainless steel mesh with a pore size below 150 μm is not used in the present invention.

[0117] Furthermore, the present invention uses experiments to explore the mechanism of photocatalytic degradation of AFB1 by powder catalyst and functional film of Example 1. It is found that the mechanism of photocatalytic degradation of AFB1 by powder catalyst is an addition reaction dominated by ·OH. The mechanism of photocatalytic degradation of AFB1 by functional film is 1 O2-dominated cycloaddition reaction at the C=C position of the furan ring. It can be seen that the functional film constructed by the present invention effectively solves the problem of reduced AFB1 adsorption capacity caused by the covering of the active sites of the catalytic material by changing the mechanism of photocatalytic degradation of AFB1.

[0118] Test Example 3: Recyclability Test of Functional Films

[0119] This experiment investigated the recycling capability of the functional film for photocatalytic removal of aflatoxin B1 in Example 1 for degradation of AFB1. The specific experimental process was as follows: (1) a 280 cm 2A stainless steel mesh (pore size 150 μm) was cleaned to remove surface oil and impurities, and then dried in a forced air drying oven at 80°C to obtain a stainless steel substrate. (2) 18.00 g of a 10% mass fraction polyvinylidene fluoride solution (PVDF, solvent: N,N-2-methylacetamide) and 9.00 g of powdered polyimide / phosphotungstic acid silver photocatalyst (MPI) were stirred and mixed for 10 min (the mass ratio of polymer matrix solution to MPI was 2:1), and then evenly brushed onto one side of the stainless steel substrate obtained in step (1), and dried in a forced air drying oven (80°C) for 1 h to obtain a functional film for photocatalytic removal of aflatoxin B1. (3) The functional film for photocatalytic removal of aflatoxin B1 prepared in step (2) was placed in 500 mL of an oil-water mixed solution containing 200 μg / kg aflatoxin B1 (in the oil-water mixed solution, peanut oil: water = 8:2, v / v), and the resulting suspension was placed in the dark and magnetically stirred for 30 minutes to reach adsorption-desorption equilibrium. Then, the photocatalytic reaction was carried out under a cold light LED ultraviolet lamp with a wavelength of λ = 254 nm and a rated power of 80 W (the light power density was about 1.99 mW / cm 2 ), the system temperature is 75 ° C. During the experiment, after each photocatalytic degradation reaction of AFB1 is completed, the functional film is directly taken out and used for the next photocatalytic degradation reaction of AFB1. The photocatalytic degradation cycle test is carried out, and the change of AFB1 degradation rate during each cycle is recorded. The test results of the recycling ability are as follows Figure 8 shown.

[0120] Depend on Figure 8 The recycling test results show that the AFB1 removal activity of the functional film of the present invention does not change after multiple cycles, indicating that no shedding loss occurs, thereby confirming that the functional film of the present invention has good recycling ability and can be reused.

[0121] Test Example 4: Comparison of aflatoxin B1 removal effects with existing catalysts

[0122] To further illustrate the special effect of the functional film for photocatalytic removal of aflatoxin B1 provided by the present invention, the present invention compares the aflatoxin B1 removal effect of the functional film (MPDF) for photocatalytic removal of aflatoxin B1 in Example 1 with the photocatalysts polyimide (PI-325), carbon nitride (GCN), and titanium dioxide (P25) reported in the prior art, and uses the photolysis of aflatoxin B1 without adding any photocatalyst as a control group.

[0123] Among them, when testing polyimide (PI-325), the photocatalytic functional film in Test Example 2 was replaced with photocatalyst polyimide (PI-325). The mass of polyimide (PI-325) was consistent with the mass of the catalyst in the functional film, and the other parameters remained consistent with Test Example 2. The polyimide used was obtained by the following steps: melamine and pyromellitic anhydride with a molar ratio of 1:1 were ground together for 30 minutes and then solid-phase thermal polycondensed. The solid-phase thermal polycondensation method was to calcine from room temperature to 325°C at a heating rate of 10°C / min under air ambient pressure, and keep warm for 4 hours. The solid-phase thermal polycondensation product was ground to obtain a photocatalyst polyimide.

[0124] When testing carbon nitride (GCN), the photocatalytic functional film in Test Example 2 is replaced with photocatalyst carbon nitride (GCN). The mass of carbon nitride is consistent with the mass of the catalyst in the functional film, and the other parameters remain consistent with those in Test Example 2. The carbon nitride (GCN) used is obtained by the following steps: 10g of melamine is fully ground in a mortar and transferred to a ceramic crucible, which is then placed in a muffle furnace. In an air atmosphere, the temperature is raised from room temperature to 550°C at a rate of 15°C / min, maintained at a constant temperature for 4h, and then naturally cooled to room temperature. After grinding the product, a light yellow powder is obtained, which is the photocatalyst graphite phase carbon nitride (g-C3N4, abbreviated as GCN).

[0125] When testing titanium dioxide (P25), the photocatalytic functional film in Test Example 2 was replaced with photocatalyst titanium dioxide (P25, photocatalyst, from Evonik Degussa brand). The quality of titanium dioxide was consistent with the quality of the catalyst in the functional film, and the other parameters remained consistent with Test Example 2.

[0126] The photocatalytic reaction time was set to 0 min, 25 min, 50 min, 75 min, and 100 min, respectively, and the degradation test of aflatoxin B1 was carried out. The photodegradation of aflatoxin B1 obtained by the test (control group) and the photocatalytic degradation of aflatoxin B1 by the functional film (MPDF) for photocatalytic removal of aflatoxin B1 according to Example 1 of the present invention, polyimide (PI-325), carbon nitride (GCN), and titanium dioxide (P25) were shown in the following figure. Figure 9 shown.

[0127] Depend on Figure 9The test results and the calculation of the rate constant show that when no catalytic material is added, the degradation rate of aflatoxin B1 in the control group is 2.44% after 25 minutes of illumination, 3.36% after 50 minutes of illumination, 4.01% after 75 minutes of illumination, and 6.78% after 100 minutes of illumination, indicating that aflatoxin B1 hardly undergoes photolysis under the irradiation of light. After using the photocatalyst, the degradation rate of aflatoxin B1 was 7.78% after 100 minutes of illumination using polyimide (PI-325), and the rate constant was 0.043h -1 The degradation rate of aflatoxin B1 was 16.45% after 100 min of irradiation with GCN, and the rate constant was 0.057 h -1 When titanium dioxide (P25) was irradiated for 100 min, the degradation rate of aflatoxin B1 was 21.74%, and the rate constant was 0.13 h -1 When the functional film of Example 1 of the present invention is used, the degradation rate of aflatoxin B1 is 25.76% after 25 minutes of illumination, 35.71% after 50 minutes of illumination, 40.39% after 75 minutes of illumination, and 55.38% after 100 minutes of illumination, with a rate constant of 0.3408 h -1 .

[0128] From the above results, it can be seen that after 100 minutes of illumination, the rate of photocatalytic degradation of aflatoxin B1 by the functional film in Example 1 of the present invention is 7.8, 6.0, and 2.7 times that of the photocatalytic materials PI-325, GCN, and P25, respectively, indicating that the functional film for photocatalytic removal of aflatoxin B1 provided by the present invention can effectively improve the removal effect of aflatoxin B1 compared with the existing photocatalytic materials for removing aflatoxin B1.

[0129] In summary, the present invention uses a stainless steel mesh as a substrate, a polyimide / silver phosphotungstate photocatalyst as an active component, and polyvinylidene fluoride as a polymer matrix. The photocatalytic functional film prepared has a porous network structure, and the powder catalyst MPI is evenly dispersed in the network structure of PVDF, which inhibits the agglomeration of MPI, and is particularly capable of promoting the separation of photogenerated carriers, compensating for the defect that the active sites of the material are covered, resulting in a decrease in the adsorption capacity of AFB1. Therefore, the functional film for photocatalytic removal of aflatoxin B1 prepared by the present invention has excellent visible light catalytic degradation of aflatoxin B1 at room temperature. Compared with photocatalysts in the prior art such as polyimide / silver phosphotungstate, polyimide, carbon nitride, and titanium dioxide, it has the characteristics of high photocatalytic efficiency, simple operation, easy recovery, and no secondary pollution. It has broad application prospects and practical application value in the degradation of aflatoxin B1 in oil and fat systems.

[0130] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a functional film for photocatalytic removal of aflatoxin B1, characterized in that: The following steps are involved: The polyimide / silver phosphotungstate photocatalyst is mixed with a polymer matrix solution, then coated on a substrate and dried to obtain the functional film for photocatalytic removal of aflatoxin B1; wherein the substrate is a stainless steel mesh; and the polymer matrix used in the polymer matrix solution is polyvinylidene fluoride.

2. The method for preparing a functional film for photocatalytic removal of aflatoxin B1 according to claim 1, characterized in that: The mass ratio of the polyimide / silver phosphotungstate photocatalyst to the polymer matrix solution is 1:(2-6).

3. The method for preparing a functional film for photocatalytic removal of aflatoxin B1 according to claim 1, characterized in that: The polymer matrix solution is prepared by dissolving a polymer matrix in an organic solvent; the organic solvent is N,N-2-methylacetamide; and the mass concentration of the polymer matrix solution is 8% to 12%.

4. The method for preparing a functional film for photocatalytic removal of aflatoxin B1 according to claim 1, characterized in that: The preparation method of the polyimide / phosphotungstic acid silver photocatalyst comprises the following steps: reacting phosphotungstic acid and melamine in water, adding a water-soluble silver salt solution for self-assembly after the reaction, and performing solid-liquid separation; washing the solid obtained by the solid-liquid separation, mixing it with pyromellitic anhydride, performing a solid-phase thermal polymerization reaction, and finally grinding to obtain the polyimide / phosphotungstic acid silver photocatalyst.

5. The method for preparing a functional film for photocatalytic removal of aflatoxin B1 according to claim 4, characterized in that: The phosphotungstic acid solution and melamine are reacted in water by adding the phosphotungstic acid solution to the melamine solution for reaction; the molar ratio of the phosphotungstic acid, melamine, and silver ions in the water-soluble silver salt solution is 1:(3-8):(1-3); the melamine solution is obtained by dissolving melamine in water, and the concentration of the melamine solution is 0.05-0.30 mol / L; the phosphotungstic acid solution is obtained by dissolving phosphotungstic acid in water, and the concentration of the phosphotungstic acid solution is 0.05-0.30 mol / L; the concentration of silver ions in the water-soluble silver salt solution is 0.20-1.10 mol / L; the reaction time is 0.5-4 hours; the self-assembly time is 0.5-4 hours; the temperature of the solid-phase thermal polymerization reaction is 300-350° C., and the time is 3-6 hours.

6. The method for preparing a functional film for photocatalytic removal of aflatoxin B1 according to any one of claims 1 to 5, characterized in that: The mixing is performed by stirring for 5 to 60 minutes; the coating is performed by brushing, scraping, or spin coating; and the drying temperature is 40 to 110° C. for 0.5 to 5 hours.

7. The method for preparing a functional film for photocatalytic removal of aflatoxin B1 according to any one of claims 1 to 5, characterized in that: The area of the substrate is 1 to 280 cm 2 The pore size of the substrate is 150~830μm; the substrate is pre-cleaned and dried before coating; Every 10~15cm 2 The substrate has a corresponding amount of polyimide / silver phosphotungstate photocatalyst of 0.6~1.4g.

8. A functional film for photocatalytically removing aflatoxin B1 prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the functional film for photocatalytic removal of aflatoxin B1 as claimed in claim 8, characterized in that: The application is the application of the functional film for photocatalytically removing aflatoxin B1 in photocatalytically removing aflatoxin B1 from oil samples.

10. The use of the functional film for photocatalytic removal of aflatoxin B1 according to claim 9, characterized in that: The photocatalytic removal is a photocatalytic reaction carried out under visible light with a wavelength of λ≥420nm; the oil sample is one or more of peanut oil, corn oil, and rice bran oil.

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