Sa@cds / g-c3n4 composite material, preparation method thereof and application in aflatoxin removal

Abstract

To provide: a SA@CDs / g-C3 N4 composite material capable of effectively removing a residual aflatoxin in a food, being mild in effect, environmentally-friendly, safe, and easy to recycle, and capable of avoiding an impact of the residual material on food quality; a preparation method thereof; and an application thereof.SOLUTION: A preparation method of a SA@CDs / g-C3 N4 composite material includes: adding a CDs / g-C3 N4 composite into water, and uniformly dispersing same through ultrasonic treatment; adding sodium alginate, intensely stirring and fully mixing a mixture, and forming a pregel solution; transferring the fully mixed pregel solution into a mold, and freeze-drying the pregel solution to obtain solid sponge; and soaking the sponge in a CaCl2 solution for gel, performing washing with deionized water, performing freeze-drying, and obtaining the SA@CDs / g- C3 N4 composite material.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention belongs to the technical field of organic materials, and specifically relates to SA@CDs / g-C 3 N 4 composite materials, a method for preparing the same, and use in aflatoxin removal.

Background Art

[0002] Foods such as grains, edible oils, and meat are susceptible to environmental pollution during cultivation, storage, and breeding, which may cause problems in food safety. In addition, microorganisms that cause diseases may multiply in these foods and form mycotoxins. Among them, a typical mycotoxin is aflatoxin (AFT), which may cause significant economic losses and health hazards. How to detoxify this is a major issue for the food industry. Currently, aflatoxin removal technologies include physical methods and chemical methods. Chemical methods generally use strong oxidants (such as ozone and hydrogen peroxide). When treating agricultural products and foods with these strong oxidants, good removal of aflatoxin can be achieved. However, since the nutrients and flavor substances of agricultural products are destroyed, the flavor and nutrition of the products are affected, and the scale-up is also limited. Physical methods generally use high-temperature treatment, and some of the flavors and nutrients with low boiling points and instability are destroyed after high-temperature treatment. Therefore, these methods have the disadvantages of unstable effects, large losses of nutrients, and contamination by new harmful components, and it is difficult to meet the requirements of the development of the modern agricultural product industry. Therefore, it is of great significance to explore a more environmentally friendly, effective, and safe method for removing aflatoxin in foods.

Summary of the Invention

[0003] The present invention provides a method for preparing SA@CDs / g-C 3 N 4 composite materials, and the steps are as follows: CDs / g-C 3 N 4The composite was added to water, sonicated to disperse it uniformly, then sodium alginate was added and stirred vigorously to mix well, forming a pre-gel solution. The well-mixed pre-gel solution was transferred to a mold and then freeze-dried to obtain a solid sponge. The solid sponge was immersed in a CaCl 2 solution for gelation, then washed with deionized water and freeze-dried to obtain the SA@CDs / g-C 3 N 4 composite material. In the method for preparing the above SA@CDs / g-C 3 N 4 composite material, the mass-volume ratio of the composite to water is selected from 1:300 to 1:800, preferably 1:500, g / mL. 3 N 4 In the method for preparing the above SA@CDs / g-C composite material, the mass ratio of the composite to sodium alginate is selected from 1:4 to 1:10, preferably 1:7.5. 3 N 4 In the method for preparing the above SA@CDs / g-C 3 N 4 composite material, the concentration of the CaCl In the method for preparing the above SA@CDs / g-C 3 N 4 solution is selected from 1 to 8 wt%, preferably 3 wt%. 2 The present invention provides a method for preparing the above CDs / g-C N 3 N 4 composite, and the steps are as follows: Melamine and trithiocyanuric acid were added to water and stirred uniformly. Then the CDs solution was added and stirred uniformly. The mixed solution was filtered, washed and dried, transferred to a muffle furnace, and calcined at high temperature to obtain the CDs / g-C 3 N 4 composite. In the method for preparing the above CDs / g-C 3 N 4 composite, the molar ratio of melamine to trithiocyanuric acid is selected from 1:0.5 to 1:1.5, preferably 1:1. In the method for preparing the above CDs / g-C 3 N 4In the method for preparing the composite, the molar volume ratio of melamine to water is selected from 1:4000 to 1:8000, preferably 1:6000, in mol / mL. The above CDs / g-C 3 N 4 In the method for preparing the composite, the volume ratio of the CDs solution to water is selected from 1 to 7:60, preferably 3:60. The above CDs / g-C 3 N 4 In the method for preparing the composite, as the high-temperature calcination conditions, the temperature is raised to 550 - 650 °C at a rate of 2 - 6 °C / min, and calcined at this temperature for 3 - 6 h. Preferably, the temperature is raised to 600 °C at a rate of 3 °C / min and calcined at this temperature for 4 h. The present invention provides a method for preparing the above CDs solution, and its steps are as follows: Put orange juice into a reactor lined with polytetrafluoroethylene, heat it at a high temperature, and after natural cooling, centrifuge and filter the reaction product to form a transparent tea-yellow carbon quantum dot solution, that is, the CDs solution. In the method for preparing the above CDs solution, as the high-temperature heating conditions, heat at 180 - 210 °C for 8 - 12 h, preferably heat at 200 °C for 10 h. The present invention provides an SA@CDs / g-C 3 N 4 composite material prepared by the above method. The present invention relates to the use of the above SA@CDs / g-C 3 N 4 in the removal of aflatoxin in food. The aflatoxin is selected from aflatoxin B 1 and the like.

Advantages of the Invention

[0004] The present invention has the following beneficial effects. The SA@CDs / g-C 3 N 4 composite material prepared by the present invention can effectively remove residual aflatoxin in food, has a mild action, is environmentally friendly, safe, easy to recycle, and can avoid the influence of material residues on food quality.

Brief Description of the Drawings

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Figure 1

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Figure 5

Modes for Carrying Out the Invention

[0006] Unless otherwise specified, other materials used in the present invention are available through commercial sources. Unless otherwise specified, other terms used in the present invention generally have meanings commonly understood by those skilled in the art. The present invention will be described in more detail below with reference to data in connection with specific embodiments. The following examples are for illustrative purposes of the present invention and do not limit the scope of the present invention in any way.

[0007] Example 1 SA@CDs / g-C 3 N 4 Prepare the composite material, and the steps are as follows: (1) Preparation of carbon quantum dot solution Add 30 mL of orange juice from fresh oranges to a 100 mL reactor lined with polytetrafluoroethylene, and heat at 200 °C for 10 h. After natural cooling, the reaction product is centrifuged and filtered through a 0.22 μm polyethersulfone filter to form a transparent tea-yellow carbon quantum dot (CDs) solution. The XRD pattern and FTIR spectrum of the carbon quantum dot solution are shown in Figure 1. As can be seen from Figure 1, the prepared carbon quantum dots have an amorphous structure and have functional groups such as carbonyl groups and hydroxyl groups on the surface. (2) CDs / g-C 3 N 4 Preparation of the composite Add 1.26 g of melamine (0.01 mol) and 3.16 g of trithiocyanuric acid (0.01 mol) to 60 mL of deionized water, stir for 1 h to obtain a uniform mixed solution, add a certain volume (1 mL, 3 mL, 5 mL, and 7 mL respectively) of the CDs solution to the above mixed solution, and continue to stir for 12 h. Filter, wash, and dry the mixed solution, transfer it to a muffle furnace, heat it to 600 °C at a rate of 3 °C / min, and calcine at this temperature for 4 h to obtain CDs / g-C 3 N 4 Obtain the composite, abbreviated as CSTCN-x photocatalyst, where x = 1, 3, 5, and 7, that is, the products obtained under the preparation conditions of 1 mL, 3 mL, 5 mL, and 7 mL of the CDs solution respectively. For comparison, in the present invention, the product prepared under the same conditions without adding the CDs solution is abbreviated as STCN.

[0008] As shown in Figure 2, the physical characteristics of the prepared CSTCN-3 and STCN are identified. Here, a is the SEM image of STCN, b and c are the TEM images of STCN at different magnifications, d is the SEM image of CSTCN-3, e - g are the TEM images of CSTCN-3 at different magnifications, h is the HRTEM image (the inserted figure is the SAED image), and i - l are the corresponding TEM-EDX elemental patterns of CSTCN-3.

[0009] The micromorphologies of STCN and CSTCN-3 are observed by SEM images. As can be seen from Figure 2a, STCN has a nanorod structure. As can be seen from Figure 2d, after doping with CDs, CSTCN-3 maintains the nanorod structure, but a large number of pores are generated on the surface. As is clearly shown from the TEM images of Figure 2b and Figure 2e, both STCN and CSTCN-3 have a hollow structure. As can be seen from Figure 2c and Figure 2f, CSTCN-3 has a thin wall, which is considered to be due to a large amount of gas released during the firing process. As can be seen from the enlarged TEM image of CSTCN-3 shown in Figure 2g, CDs are successfully doped into STCN. As can be seen from Figure 2h, lattice lines belonging to the carbon (001) crystal plane appear in the HRTEM, which further indicates that CDs are strongly bonded to STCN. Furthermore, as can be seen from the related TEM-EDX elemental patterns of CSTCN-3 shown in Figure 2i - Figure 2l, C, N, O, and S are uniformly distributed in the sample. From the above results, it is confirmed that CDs derived from citrus fruits are successfully fixed on g-C 3 N 4 nanotubes.

[0010] Figure 3 shows the XRD pattern (a), FT-IR spectrum (b), UV-vis absorption spectrum (c), PL spectrum (d), EIS diagram (e), and transient photocurrent response (f) of the product obtained in step (2) above. As can be seen from the XRD spectrum, the prepared g-C3 N 4 Regarding the crystal structure of the materials, as shown in Figure 3a, all samples showed two similar characteristic diffraction peaks. The broad peak at 13.1° corresponded to the in-plane repeating motif of the tris-s-triazine ring, and the sharp peak at 27.3° was due to the faceted stacking of the conjugated aromatic units. Similar to the XRD images, the FT-IR spectra of all samples showed almost the same characteristic peaks. As shown in Figure 3b, the sharp peak at 816 cm -1 was due to the formation of heptazine, and the multiple peaks in the range of 1100 - 1750 cm -1 were due to the stretching vibrations of the C-N heterocycle. The broad peak in the range of 3000 - 3500 cm -1 was due to adsorbed water and N-H stretching vibrations. Since the CSTCN-x curves modified with CDs showed no significant changes compared with STCN, it was shown that the crystal and molecular structures of STCN in the composite materials were not affected by the CDs.

[0011] Improving light absorption is one of the most effective ways to improve the catalytic performance of photocatalysts. As shown in Figure 3c, due to the quantum effect of CDs, the light absorption ability of the CSTCN-x composite materials was significantly improved. Also, as the quantum dot concentration increased, the absorption was further promoted. The color of the samples gradually changed from yellow to brown. Photoluminescence and time-resolved photoluminescence were used to measure the separation and transfer efficiency of photo-generated carriers. As shown in Figure 3d, after the introduction of CDs, the CSTCN-x composite materials showed lower PL intensity than STCN. This result indicates that the introduction of CDs can effectively promote the separation of carriers. To further evaluate the effective separation and transfer efficiency of photo-generated carriers in CSTCN-x, electrochemical property evaluations were carried out. Figure 3e shows the electrochemical impedance spectrum (EIS) of the prepared catalysts. Compared with STCN, CSTCN-3 shows a shorter arc radius, indicating a smaller charge transfer resistance and more effective charge separation efficiency. Furthermore, as shown in Figure 3f, CSTCN-3 shows the highest photocurrent response intensity in the repeated cycles of "switching" illumination, indicating a fast carrier transport speed in visible light. As can be seen from this, CSTCN-3 has the best photocatalytic performance. However, with the increase in the CDs doping concentration, the photocurrent response intensity decreases, which is considered to be due to the introduction of new complex sites due to the increase in CDs.

[0012] Figure 4 shows the high-resolution XPS spectra of STCN and CSTCN-3. The surface components and elemental compositions of the prepared samples were analyzed using XPS spectra. The high-resolution C1s spectrum in Figure 4a can be deconvoluted into two peaks with binding energies of 284.7 and 287.9 eV, which are attributed to C-C / C=C and N-C=N, respectively. As shown in Figure 4b, the N1s spectrum can be fitted to three peaks located at 398.4, 399.9, and 401.1 eV. These peaks correspond to C-N=C, N-(C) 3 and N-Hx, respectively. Figure 4c shows the three peaks obtained in the high-resolution O1s spectrum, which are attributed to C=O at 531.5 eV, C-O at 532.2 eV, and O-H / adsorbed water at 533.3 eV, respectively. Note that compared with STCN, the contents of C=O and C-O on the surface of CSTCN-3 increase significantly, which is considered to be due to the presence of a large number of oxygen-containing functional groups on the CD surface. A weak S element signal was observed in the high-resolution S2p spectrum. The peak at 163.4 eV was identified as an S-N bond, and the peak at 162.8 eV was identified as the formation of sulfur oxides. Furthermore, all the peaks of O1s in CSTCN-3 are shifted towards the lower binding energy side, which suggests the presence of an electron flow in the CDs in the composite material. Since CSTCN-3 has the best photocatalytic performance, in the present invention, CSTCN-3 was directly used to prepare the SA@CSTCN composite as in the following step (3).

[0013] (3) Preparation of SA@CDs / g-C 3 N 4 Composite material preparation 0.1 g of the CSTCN-3 photocatalyst was added to 50 mL of deionized water and sonicated for more than 30 min to disperse it uniformly. Then, 0.75 g of sodium alginate (SA) was added and stirred vigorously for 6 h to mix well and form a pregel solution. The well-mixed pregel solution was transferred to a mold and then freeze-dried for 24 h to obtain a solid sponge. The solid sponge was immersed in 300 mL of 3 wt% CaCl 2 solution for 6 h to gelate. After washing thoroughly with deionized water and freeze-drying for 36 h, a sodium alginate gel sheet with CSTCN-3 attached, that is, SA@CDs / g-C 3 N 4 composite material was obtained. Since its physical form is sponge-like, it is also called SA@CSTCN sponge. For comparison, in the present invention, SA sponge was prepared under the same conditions without adding the CSTCN photocatalyst.

[0014] Figure 5 shows the preparation flowchart of SA@CSTCN sponge (a), the appearance diagrams of SA sponge and SA@CSTCN sponge (b), the surface SEM diagram of SA@CSTCN sponge (c), and the cross-section SEM diagram of SA@CSTCN sponge (d). As shown in Figure 5a, which is a schematic diagram of the preparation of SA@CSTCN sponge, through the freeze-drying process, the ice crystals in the SA gel sublimated to form pores. Then, Ca 2+ was added to crosslink and solidify the gel, giving a certain mechanical strength. When there is no photocatalyst, the prepared SA sponge shows translucency, indicating that light transmits well through the SA gel matrix. When compared with the SA sponge, the SA@CSTCN sponge shows yellow, indicating that the catalyst is well-dispersed (Figure 5b). As shown in Figures 5c and 5d of the SA@CSTCN sponge, when the pores are large, not only is the reflection of photons promoted, but more reactive sites can be obtained. Furthermore, the abundant pores give the sponge buoyancy, ensuring a continuous supply of oxygen and promoting the generation of ROS.

[0015] Application Example 1 Removal of Aflatoxin B in Peanuts 1 : 1 kg of peanuts were taken 5 times. 1 g of CSTCN (including CSTCN-1, CSTCN-3, CSTCN-5, and CSTCN-7) and 3 g of SA@CSTCN were added to the peanuts respectively, and they were uniformly stirred at a uniform speed of 230 rpm for 8 min, 400 kg of pure water was added and uniformly mixed, irradiated with light for 6 h, left standing until solid-liquid separation, the supernatant was discarded, air-dried, and Aflatoxin B in the peanuts 1 was removed.

[0016] 5 g of peanuts before and after detoxification according to the above method were taken, 10 mL of cold methanol was added for elution, left standing, 1 mL of the suspension was put into a centrifuge tube, vortex shocked for 2 min, centrifuged at 4 °C and 10,000 rpm for 10 min, and the aflatoxin concentration in the supernatant was analyzed using high performance liquid chromatography (HPLC). When the toxin concentration decreased by 85% or more, it met the requirements of the national standard and was recorded as a successful removal. The test results are shown in Table 1: Table 1 JPEG2025077957000002.jpg51147 The above test results show that the CSTCN prepared according to the present invention can effectively decompose and remove aflatoxin in peanuts. After combining CSTCN and SA to form SA@CSTCN, the material becomes sponge-like and is easy to recycle, so it has little impact on the quality of food.

[0017] Application Example 2 Aflatoxin B in Peanut Oil 1Removal: 1 kg of peanut oil was taken 5 times. 1 g of CSTCN (including CSTCN-1, CSTCN-3, CSTCN-5, and CSTCN-7) and 3 g of SA@CSTCN were added to the peanut oil respectively, 10 kg of pure water was added, shaken for 35 min, stirred under light irradiation for 6 h, centrifuged at 10,000 rpm for 10 min, allowed to stand, and the aqueous layer was discarded, that is, aflatoxin B in peanut oil insoluble in water 1 was removed. 5 mL of peanut oil before and after detoxification according to the above method was taken respectively, 5 mL of acetonitrile was added, allowed to stand, 1 mL of the supernatant was put into a centrifuge tube, centrifuged at 13,000 rpm at 4 °C for 10 min, and the aflatoxin concentration in the supernatant was analyzed using high performance liquid chromatography (HPLC). When the toxin concentration decreased by 85% or more, it met the requirements of the national standard and was recorded as a successful removal. The test results are shown in Table 2: Table 2 JPEG2025077957000003.jpg51147 The above test results indicate that the CSTCN and SA@CSTCN sponges prepared according to the present invention are also effective in decomposing and removing aflatoxin in peanut oil.

[0018] The above-described content is only a preferred embodiment of the present invention and does not limit the present invention in any way. Those skilled in the art can obtain equivalent embodiments by making equivalent changes such as modifications and deformations to the above-disclosed technical content. However, as long as it does not deviate from the content of the technical solution of the present invention, any simple modification, equivalent change or deformation added to the above embodiments based on the technical essence of the present invention shall be included in the protection scope of the technical solution of the present invention.

Claims

1. CDs / g-C ３ N ４ The composite is added to water and ultrasonicated to disperse it uniformly, then sodium alginate is added and stirred vigorously to form a pregel solution, the well-mixed pregel solution is transferred to a mold and then freeze-dried to obtain a solid sponge, and the solid sponge is then cooled to 100°C and cooled to 30°C. ２ The SA@CDs / g-C was gelled by immersion in the solution, then washed with deionized water and freeze-dried. ３ N ４ Obtaining a composite material, The CDs / g-C ３ N ４ The mass volume ratio of the composite to water is selected from 1:300 to 1:800 g / mL, and the CDs / g-C ３ N ４ The mass ratio of the composite to sodium alginate is selected from 1:4 to 1:10, and the CaCl ２ The concentration of the solution is selected from 1 to 8 wt %; The CDs / g-C ３ N ４ The steps of the method for preparing the composite are as follows: Melamine and trithiocyanuric acid are added to water and stirred uniformly, then the CDs solution is added and stirred uniformly, the mixed solution is filtered, washed and dried, transferred to a muffle furnace, and calcined at high temperature to obtain CDs / g-C. ３ N ４ Obtaining a compound, The molar ratio of the melamine to the trithiocyanuric acid is selected from 1:0.5 to 1:1.5, and the high-temperature firing conditions include heating to 550 to 650° C. at a rate of 2 to 6° C. / min and firing at this temperature for 3 to 6 hours, The steps of the preparation method of the CDs solution are as follows: Orange juice is placed in a polytetrafluoroethylene-lined reactor and heated at 180-210 °C for 8-12 h. After natural cooling, the reaction product is centrifuged and filtered to form a transparent brown-yellow carbon quantum dot solution, i.e., CDs solution, SA@CDs / g-C. ３ N ４ Methods for preparing composite materials.

2. SA@CDs / g-C prepared by the method of claim 1 ３ N ４ Composite material.

3. The SA@CDs / g-C according to claim 2 in removing aflatoxins from food ３ N ４ Use of composite materials.

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