An ultrasonic-assisted corn by-product co-upgrading method

Abstract

The application provides an ultrasonic-assisted corn by-product synergistic upgrading processing method, taking corn by-products as raw materials, drying and crushing and passing through a 30-mesh to 60-mesh sieve, then washing with ultrapure water by vortex oscillation to remove water-soluble impurities, then adding water-ethanol-petroleum ether extraction liquid according to a solid-liquid mass-volume ratio of 1:4, applying ultrasonic treatment with a power of 200W to 400W and a frequency of 40kHz in a constant-temperature water bath at 40 DEG C to 60 DEG C for 30min, centrifugally separating the solid-liquid two phases after the ultrasonic treatment, and drying the solid phase to obtain the upgraded product. Under the ultrasonic-assisted action, the free-state mycotoxins of deoxynivalenol, zearalenone and fumonisin FB1, FB2 and FB3 are simultaneously dissolved out, the removal rate reaches 77.0% to 90.7% under the optimal treatment time of 30min, and the secondary release of the combined-state toxins caused by the destruction of the matrix structure is avoided by strictly controlling the ultrasonic time; the organic solvent recycling can be realized by the reduced-pressure distillation of the extraction waste liquid.

Description

Technical Field

[0001] This invention relates to the field of agricultural biotechnology, and more specifically, to an ultrasound-assisted method for the synergistic improvement of corn by-products. Background Technology

[0002] Mycotoxins are toxic secondary metabolites produced by filamentous fungi such as Aspergillus and Fusarium. Corn and its byproducts, due to their rich nutritional content and long storage period, are susceptible to contamination by deoxynivalenone (DON), zearalenone (ZEN), nivalenol (NIV), and fumonisins (FMs). Monitoring data from major corn-producing areas such as Jilin and Liaoning provinces show high rates of co-contamination by these toxins, with some samples exceeding standards significantly. This not only leads to waste of grain resources but also poses a direct threat to food security and public health by causing acute poisoning or chronic damage to humans and animals through the food and feed chains.

[0003] Current technologies for detoxifying mycotoxins in cereals have formed a diverse system: physical methods, such as sieving, color sorting, and cold plasma, have the advantage of simple operation, but their effectiveness in removing deeply contaminated toxins is limited; biological methods, such as microbial degradation and enzymatic hydrolysis, are environmentally friendly, but face industrialization bottlenecks due to long reaction cycles and high costs; among chemical methods, ozone and oxidants can efficiently degrade toxins, but may damage the quality of raw materials or cause secondary pollution. Organic solvent extraction has attracted much attention due to its high selectivity and fast detoxification speed, but research on its process optimization and industrial applicability for the synergistic removal of multiple toxins in corn by-products remains relatively weak.

[0004] In summary, for deeply contaminated corn by-products, single detoxification technologies are insufficient for the efficient removal of multiple toxins. Furthermore, existing organic solvent processes primarily focus on single toxins, lacking systematic exploration of the synergistic removal of DON, ZEN, NIV, and FMs, and the industrial-scale process parameters remain unclear. Therefore, there is an urgent need to develop an efficient and low-cost industrial-scale technology for detoxifying corn by-products containing mycotoxins. Summary of the Invention

[0005] In view of this, the present invention proposes an ultrasound-assisted synergistic quality improvement processing method for corn by-products. Using corn by-products as raw materials, an anhydrous ethanol-petroleum ether mixed extraction system is adopted. By optimizing the ultrasonic extraction time, the removal effect of this process on four target toxins is explored, key technical parameters are clarified, and theoretical basis and practice are provided for the detoxification technology of corn by-products.

[0006] To achieve the above objectives, the present invention provides the following technical solution: An ultrasound-assisted method for synergistic quality improvement of corn by-products includes the following steps: Corn processing byproducts contaminated with multiple fungal toxins were crushed and sieved to obtain a powdery matrix with a particle size of 30-60 mesh. Ultrapure water was added to the powdered matrix for vortex wetting, followed by centrifugation and collection of the precipitate to remove water-soluble impurities; Add water-ethanol-petroleum ether extract to the precipitate at a solid-liquid mass-volume ratio of 1:3-1:5, and apply ultrasonic treatment at a power of 200W-400W and a frequency of 40kHz for 20 to 40 minutes under a constant temperature water bath at 40℃ to 60℃. After ultrasonication, the solid and liquid phases were separated by centrifugation. The solid residue was collected and dried to obtain an improved corn by-product with a synchronously reduced level of mycotoxin residue.

[0007] Furthermore, the corn processing by-product is selected from at least one of corn germ meal, corn bran, or corn gluten meal.

[0008] Furthermore, in the crushing and screening step, the corn by-product raw material is dried to a moisture content of no more than 12% and then mechanically crushed, and the crushed material is passed through a 40-mesh standard sieve.

[0009] Furthermore, the vortex oscillation wetting process includes: Add 20 mL of ultrapure water to every 5,000 g of sieved powder, vortex at 2000 rpm-3000 rpm for 15 min-25 min, then centrifuge at 7000 rpm-9000 rpm for 8 min-12 min, discard the supernatant and collect the precipitate.

[0010] Furthermore, the solid-liquid mass-volume ratio of the aqueous ethanol-petroleum ether extract is preferably 1:4, and the volume ratio of anhydrous ethanol to petroleum ether is 1:1.

[0011] Furthermore, the ultrasonic treatment process includes: applying ultrasonic treatment with a power of 200W and a frequency of 40kHz in a constant temperature water bath at 50℃ for 30 minutes.

[0012] Furthermore, the centrifugal separation process includes: Centrifuge at 7000 rpm for 8-12 minutes, and dry the resulting solid residue at room temperature or at a low temperature below 40°C.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves the synergistic removal of deoxynivalenol, zearalenone, and fumonisins FB1, FB2, and FB3. Under the optimal treatment time of 30 minutes, the removal rates of the five mycotoxins reached 90.7%, 88.0%, 82.1%, 80.4%, and 77.0%, respectively, while simultaneously reducing the residual levels of each toxin to below the safety threshold for feed and food processing. By strictly controlling the ultrasonic treatment time, the system can effectively inhibit the secondary release of bound toxins caused by matrix structure damage while promoting the efficient dissolution of free toxins. Furthermore, the organic solvent can be recovered and reused through vacuum distillation. The overall operation is convenient and has low equipment dependence, providing a suitable industrialization technical path for the clean upgrading and resource utilization of corn by-products. Attached Figure Description

[0014] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings: Figure 1 This is a schematic diagram showing the changes in DON content of deoxynivalenol at different ultrasonic treatment times in an embodiment of the present invention. Figure 2 This is a schematic diagram showing the changes in zearalenone (ZEN) content in zearalenone at different ultrasonic treatment times in an embodiment of the present invention. Figure 3 This is a schematic diagram showing the changes in fumonisin FB1 content at different ultrasonic treatment times in an embodiment of the present invention. Figure 4 This is a schematic diagram showing the changes in fumonisin FB2 content at different ultrasonic treatment times in an embodiment of the present invention; Figure 5 This is a schematic diagram showing the changes in fumonisin FB3 content at different ultrasonic treatment times in an embodiment of the present invention. Detailed Implementation

[0015] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0016] This embodiment proposes an ultrasound-assisted method for the synergistic improvement of corn by-products. Using corn processing by-products contaminated with multiple mycotoxins as raw materials, selective extraction is performed under ultrasound-assisted conditions using a mixed solvent of anhydrous ethanol and petroleum ether. This simultaneously reduces the residual levels of multiple mycotoxins such as deoxynivalenol, zearalenone, and fumonisin, thereby achieving a cleaner and higher-quality corn by-product matrix.

[0017] The corn by-products in this embodiment include corn germ meal, corn bran, corn gluten meal, and other by-products generated during the deep processing of corn. The initial mycotoxin content ranges as follows: deoxynivalenol 8000-10000 μg / kg, zearalenone 150-200 μg / kg, fumonisin FB1 2000-3000 μg / kg, fumonisin FB2 500-700 μg / kg, and fumonisin FB3 250-350 μg / kg.

[0018] The above raw materials were pretreated by crushing and sieving. Corn by-product raw materials were crushed and passed through a 40-mesh standard sieve. 5.000 g of sample (n=2, parallel determination) was accurately weighed and processed according to the pretreatment method in LS / T 6133-2018: 20 mL of acetonitrile-water-acetic acid (70:29:1, v / v) extraction solution was added, vortexed, and centrifuged at 7000 rpm for 10 min. 0.6 mL of the supernatant was mixed with 0.6 mL of ultrapure water and centrifuged at 4 ℃ and 12000 rpm for 10 min. The supernatant was filtered through a 0.2 μm polytetrafluoroethylene filter membrane, and 180 μL of the filtrate was mixed with 20 μL of stable isotope internal standard solution. The contents of DON, ZEN, NIV, and FMs (FB1, FB2, FB3) were determined by LC-MS / MS.

[0019] Accurately weigh 5.000 g of pretreated corn by-product powder and place it in a stoppered conical flask. Add 20 mL of ultrapure water and vortex at 2000-3000 rpm for 15-25 min, preferably 20 min, to fully wet the material and initially dissolve water-soluble impurities. Then, centrifuge in a medical centrifuge at 7000-9000 rpm for 8-12 min, preferably 8000 rpm for 10 min. Discard the supernatant and collect the precipitate for later use. Washing with water removes water-soluble sugars and inorganic salts adhering to the surface, reducing the co-dissolution of impurities during subsequent organic solvent extraction.

[0020] The extractant is a mixture of anhydrous ethanol and petroleum ether at a volume ratio of 1:1. Anhydrous ethanol provides a moderately polar environment and exhibits good solubility for highly polar deoxynivalenol and fumonisin; petroleum ether, as a weakly polar solvent, has efficient dissolution capability for lipid-soluble zearalenone. The two solvents, when mixed in equal volumes, form a complex solvent system with a polarity gradient, which can simultaneously accommodate the solubility characteristics of different types of mycotoxins. The mixed solvent is added to the precipitate at a solid-liquid mass-volume ratio of 1:3 to 1:5, preferably 1:4, i.e., 4 mL of mixed solvent per gram of precipitate.

[0021] The mixture was placed in an ultrasonic extraction device and ultrasonically treated under a constant temperature water bath at 40°C to 60°C. The ultrasonic power was set to 200 to 400 W, the ultrasonic frequency to 40 kHz, and the ultrasonic treatment time to 20 to 40 min, preferably 30 min. The microjets and mechanical vibrations generated by ultrasonic cavitation can enhance the penetration of solvent molecules into the matrix pores, promote the diffusion of free fungal toxins from the cell wall and protein binding sites into the liquid phase, and at the same time avoid excessive destruction of the matrix structure caused by prolonged ultrasonication, which could lead to the secondary release of bound toxins.

[0022] After ultrasonic extraction, the mixture was transferred to centrifuge tubes and centrifuged at 7000 rpm for 8 to 12 minutes, preferably 7000 rpm for 10 minutes, to ensure complete separation of the solid residue from the liquid phase. The supernatant was collected as the extraction waste liquid rich in mycotoxins. The solid residue was dried at room temperature or at a low temperature below 40°C to obtain the upgraded corn by-product matrix. To verify the upgrading effect, the contents of the above four types of mycotoxins were determined using the same LC-MS / MS method.

[0023] The pretreatment procedure is as follows: Accurately weigh 5.000 g of sample, add 20 mL of acetonitrile-water-acetic acid mixed extraction solution, wherein the volume ratio of acetonitrile, water and acetic acid is 70:29:1, vortex to mix, and then rotate and shake for 18-22 min, preferably 20 min. Centrifuge at 7000 rpm for 8-12 min, preferably 10 min. Take 0.6 mL of supernatant and mix it with 0.6 mL of ultrapure water, and centrifuge at 12000 rpm at 4℃ for 8-12 min, preferably 10 min. After filtering the supernatant through a 0.2 μm polytetrafluoroethylene filter membrane, take 180 μL of the filtrate and mix it with 20 μL of stable isotope internal standard mixture for LC-MS / MS analysis.

[0024] The liquid chromatography conditions were set as follows: a Phenomenex Kinetex C18 column with dimensions of 100 mm × 2.1 mm and a packing particle size of 1.7 μm was used. In positive ion mode, the mobile phase consisted of phase A and phase B. Phase A was a 1 mmol / L ammonium acetate aqueous solution containing 0.1% formic acid, and phase B was a methanol solution containing 0.1% formic acid. In negative ion mode, phase A was an aqueous solution containing 0.05% acetic acid, and phase B was a methanol solution containing 0.05% acetic acid.

[0025] The elution gradient program was set as follows: 0-2 min to maintain 5% B phase; 2-50 min to linearly increase to 90% B phase; 50-70 min to continue linearly increasing to 95% B phase; 70-75 min to maintain 95% B phase. The column temperature was controlled at 30℃, the mobile phase flow rate was 0.25 mL / min, and the injection volume was 5 μL.

[0026] Mass spectrometry conditions were set as follows: an electrospray ionization source was used, with a spray voltage of 5500 V in positive ion mode and -4500 V in negative ion mode; the ion transmission tube temperature and capillary temperature were both 300℃; the sheath gas flow rate was 35 arb; and the auxiliary gas flow rate was 15 arb. Both the sheath gas and the auxiliary gas were high-purity nitrogen with a purity of not less than 99.99%. The mass scan range was m / z 70-1000, and the detection mode was multiple reaction monitoring (MRM). Quantitative correction was performed using the stable isotope internal standard method, and the removal rates of each toxin were calculated.

[0027] Example 1 A corn by-product raw material with an initial deoxynivalenol (DON) content of 9386.84 μg / kg, zearalenone (ZEN) content of 183.73 μg / kg, fumonisin FB1 content of 2607.74 μg / kg, fumonisin FB2 content of 586.88 μg / kg, and fumonisin FB3 content of 302.25 μg / kg was crushed and passed through a 40-mesh sieve.

[0028] Accurately weigh 5.000 g of powder, add 20 mL of ultrapure water and vortex for 20 min, centrifuge at 8000 rpm for 10 min, discard the supernatant and collect the precipitate.

[0029] Add 20 mL of a mixture of anhydrous ethanol and petroleum ether in a volume ratio of 1:1 at a solid-liquid ratio of 1:4, and then subject the mixture to ultrasonic treatment at 200 W and 40 kHz for 30 min in a constant temperature water bath at 50℃.

[0030] After sonication, the solid phase was separated by centrifugation at 7000 rpm for 10 min and then dried.

[0031] After testing, the content of deoxynivalenol (DON) in the treated sample decreased to 870.97 μg / kg, with a removal rate of 90.7%; the content of zearalenone (ZEN) decreased to 22.17 μg / kg, with a removal rate of 88.0%; the content of fumonisin FB1 decreased to 467.34 μg / kg, with a removal rate of 82.1%; the content of fumonisin FB2 decreased to 115.24 μg / kg, with a removal rate of 80.4%; and the content of fumonisin FB3 decreased to 69.61 μg / kg, with a removal rate of 77.0%. This example demonstrates that under 30 min of ultrasonic treatment, the mixed solvent achieved efficient and synergistic dissolution of multiple types of free mycotoxins.

[0032] Example 2 Using the same raw materials and pretreatment process as in Example 1, only the ultrasonic treatment time was extended to 60 min, while the other parameters remained unchanged.

[0033] After treatment, the content of deoxynivalenol (DON) in the sample was 1301.58 μg / kg, with a removal rate reduced to 86.1%; the content of zearalenone (ZEN) was 42.58 μg / kg, with a removal rate reduced to 76.8%; the content of fumonisin FB1 was 563.71 μg / kg, with a removal rate reduced to 78.4%; the content of fumonisin FB2 was 147.00 μg / kg, with a removal rate reduced to 74.9%; and the content of fumonisin FB3 was 81.23 μg / kg, with a removal rate reduced to 73.1%.

[0034] Compared to Example 1, the content of each toxin increased to varying degrees. This phenomenon is attributed to the fact that 60 minutes of ultrasound treatment exceeded the optimal treatment time, disrupting the binding structure of the matrix such as cellulose and protein in the corn by-products. The bound toxins, originally bound to the matrix by covalent or hydrogen bonds, were released and re-dissolved into the extract, leading to a decrease in removal efficiency. This example demonstrates that longer ultrasound time is not necessarily better; the treatment time must be strictly controlled to avoid the secondary release of bound toxins.

[0035] Example 3 Using the same raw materials and pretreatment process as in Example 1, the ultrasonic treatment time was further extended to 90 min, while the other parameters remained unchanged.

[0036] After treatment, the content of deoxynivalenol (DON) in the sample was 1097.74 μg / kg, with a removal rate of 88.3%; the content of zearalenone (ZEN) was 28.36 μg / kg, with a removal rate of 84.6%; the content of fumonisin FB1 was 518.35 μg / kg, with a removal rate of 80.1%; the content of fumonisin FB2 was 135.56 μg / kg, with a removal rate of 76.9%; and the content of fumonisin FB3 was 77.67 μg / kg, with a removal rate of 74.3%.

[0037] Compared to Example 2, the content of each toxin decreased slightly but did not return to the level of Example 1. This is because the extraction system gradually approached dissolution equilibrium after 90 min, and some toxins underwent slight chemical degradation under the continuous ultrasonic cavitation effect and thermal effect. At the same time, the release rate and degradation rate of bound toxins reached a dynamic equilibrium.

[0038] Based on the data from Examples 1 to 3, the statistical results are shown in Table 1 (content of various mycotoxins in corn by-products under different ultrasonic extraction times), and the corresponding content change trends are as follows: Figure 1-5 As shown.

[0039] Table 1

[0040] Table 1 shows that 30 min is the optimal ultrasonic treatment time, at which point free toxins have been fully dissolved, while bound toxins have not yet been released in large quantities. Under this condition, the removal rate of various toxins reaches 77.0% to 90.7%, achieving sufficient dissolution of free toxins. Extending the ultrasonic time to 60 min disrupts the matrix structure of corn by-products, leading to the release of bound toxins, which causes a rebound in toxin content and a decrease in the removal rate. At 90 min, the system approaches dissolution equilibrium, and the content slightly decreases.

[0041] Example 4 Using the same raw materials as in Example 1, the effect of different solvent ratios on the synergistic removal effect was investigated. Three groups were set up with anhydrous ethanol to petroleum ether volume ratios of 1:2, 1:1 and 2:1, and a solid-liquid ratio of 1:4. The mixture was ultrasonicated at 50°C for 30 min.

[0042] When the volume ratio is 1:2, the proportion of petroleum ether is relatively high, and the removal rate of zearalenone (ZEN) increases to over 90%, but the removal rates of deoxynivalenol (DON) and fumonisin (FB1) decrease to around 75%, indicating that the weakly polar solvent has limited ability to dissolve polar toxins.

[0043] When the volume ratio is 2:1, the proportion of anhydrous ethanol is relatively high, increasing the removal rate of deoxynivalenol (DON) to 92%, but decreasing the removal rate of zearalenone (ZEN) to 82%, indicating that the polar solvent is not efficient enough for extracting lipophilic toxins. At a volume ratio of 1:1, the removal rates of all toxins are at a relatively high level, ranging from 77% to 90.7%, proving that this ratio can achieve synergistic removal of both polar and lipophilic toxins, making it the optimal solvent ratio.

[0044] Example 5 Using the same raw materials and process parameters as in Example 1, only the solid-liquid ratio was adjusted to 1:3, that is, 3 mL of mixed solvent for every gram of precipitate.

[0045] The removal rate of each toxin decreased by 3% to 5% after treatment compared with Example 1, indicating that when the amount of solvent is insufficient, the toxin dissolution does not reach saturation equilibrium, and free toxins remain inside the matrix.

[0046] When the solid-liquid ratio was adjusted to 1:5, the removal rate of each toxin increased by 1% to 2% compared to Example 1, but the increased solvent consumption led to higher subsequent recovery costs. Considering both removal efficiency and economy, a solid-liquid ratio of 1:4 is the preferred parameter for industrial application.

[0047] This invention utilizes anhydrous ethanol and petroleum ether to construct a broad-spectrum extraction system, and shortens the extraction time and reduces the processing temperature through ultrasonic cavitation. The ultrasonic cavitation bubbles generate localized high temperature, high pressure, and high-speed microjets upon collapse. This physical effect disrupts the matrix surface boundary layer, increases the solid-liquid mass transfer coefficient, and allows the solvent to rapidly penetrate into the cell interior and protein interstitial spaces, carrying free fungal toxins to the liquid phase. A processing time of 30 minutes is sufficient to achieve complete dissolution of free toxins while maintaining the structural integrity of matrix proteins and cellulose, preventing the release of bound toxins.

[0048] The differences in removal efficiency of different toxins are directly related to their molecular polarity, structural characteristics, and binding strength to the matrix. Deoxynivalenol and fumonisin FB1 molecules contain multiple hydroxyl and carboxyl groups, exhibiting strong hydrogen bonding with matrix proteins, thus showing significant release of bound states and content rebound when exceeding the limit. Zearalenone, a lipophilic lactone compound, has weaker binding to the matrix, and its content fluctuation is mainly dominated by solvent saturation. Fumonisin FB3 has a small molecular size and relatively weak polarity, resulting in the weakest binding to the matrix and thus the smallest content fluctuation. These differentiated behaviors further demonstrate that the method of this invention has a recognizable removal effect on toxins with different structural types.

[0049] After treatment using the method of this invention, the residual levels of multiple mycotoxins in corn by-products are simultaneously reduced to below the safe threshold, allowing them to be directly used as high-quality feed ingredients or food processing additives, thus achieving high-value utilization of contaminated corn by-products. After the extraction waste liquid undergoes vacuum distillation to recover organic solvents, the residual toxin concentrate can be centrally treated for harmless disposal, with a solvent recovery rate exceeding 85%, meeting the economic and environmental requirements for industrial production. This invention features clear process parameters, simple operation steps, and low equipment dependence, making it easy to integrate into existing corn deep-processing production lines. It provides an industrially feasible technical path for the synergistic removal and resource-based quality improvement of mycotoxins in corn by-products.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for synergistic quality improvement of corn by-products with ultrasound assistance, comprising the following steps: Corn processing byproducts contaminated with multiple fungal toxins were crushed and sieved to obtain a powdery matrix with a particle size of 30-60 mesh. Ultrapure water was added to the powdered matrix for vortex wetting, followed by centrifugation and collection of the precipitate to remove water-soluble impurities; Add water-ethanol-petroleum ether extract to the precipitate at a solid-liquid mass-volume ratio of 1:3-1:5, and apply ultrasonic treatment at a power of 200W-400W and a frequency of 40kHz for 20 to 40 minutes under a constant temperature water bath at 40℃ to 60℃. After ultrasonication, the solid and liquid phases were separated by centrifugation. The solid residue was collected and dried to obtain an improved corn by-product with a synchronously reduced level of mycotoxin residue.

2. The method according to claim 1, characterized in that, The corn processing by-product is selected from at least one of corn germ meal, corn bran, or corn gluten meal.

3. The method according to claim 1, characterized in that, In the crushing and screening step, the corn by-product raw material is dried to a moisture content of no more than 12% and then mechanically crushed. The crushed material is then passed through a 40-mesh standard sieve.

4. The method according to claim 1, characterized in that, The vortex oscillation wetting process includes: Add 20 mL of ultrapure water to every 5,000 g of sieved powder, vortex at 2000 rpm-3000 rpm for 15 min-25 min, then centrifuge at 7000 rpm-9000 rpm for 8 min-12 min, discard the supernatant and collect the precipitate.

5. The method according to claim 1, characterized in that, The preferred solid-liquid mass-volume ratio of the aqueous ethanol-petroleum ether extract is 1:4, and the volume ratio of anhydrous ethanol to petroleum ether is 1:

1.

6. The method according to claim 1, characterized in that, The ultrasonic treatment process includes applying ultrasonic treatment with a power of 200W and a frequency of 40kHz in a constant temperature water bath at 50℃ for 30 minutes.

7. The method according to claim 1, characterized in that, The centrifugation process includes: Centrifuge at 7000 rpm for 8-12 minutes, and dry the resulting solid residue at room temperature or at a low temperature below 40°C.

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