A method for removing pesticide residues from an extract

Abstract

This invention relates to the field of natural product separation and extraction technology, and discloses a method for removing pesticide residues from extracts, comprising the following steps: S1. Dissolving the extract in an aqueous ethanol solution to form a solution; S2. Adding 0.4%-0.8% of an adsorbent to the solution, stirring thoroughly, allowing it to settle, and filtering the supernatant; S3. Passing the supernatant through a macroporous resin at a flow rate of 3-6 BV / h, and collecting the eluent; S4. Extracting the eluent using a deep eutectic solvent as an entrainer and employing supercritical carbon dioxide extraction to separate and obtain the extract free of pesticide residues. The adsorbent is made from the following raw materials in parts by weight: 25-30 parts modified diatomaceous earth, 20-25 parts aminated silica, and 10-15 parts nano-iron oxide-carbon nanotube composite. This invention can efficiently reduce pesticide residues while ensuring the purity of the extract.

Description

Technical Field

[0001] This invention relates to the field of natural product separation and extraction technology, and in particular to a method for removing pesticide residues from extracts. Background Technology

[0002] Agricultural development is inseparable from the use of pesticides. Pesticides effectively control the damage to crops caused by pests, pathogens, and weeds, thereby ensuring crop yield and quality. Pesticides can be classified according to their target pests, including insecticides, fungicides, herbicides, acaricides, and plant growth regulators. Insecticides such as phosmet and bifenthrin are used to control pests and insect-borne diseases; fungicides such as pentachloronitrobenzene and vinclozolin are used to combat diseases caused by fungi and bacteria; herbicides such as atrazine, terbufos, and propargite are used to suppress weed growth; acaricides such as permethrin, dichlorvos, and dicofol are used to kill ticks, mites, and other small arthropods; and plant growth regulators such as auxins and gibberellins are used to regulate plant growth and development. Among these categories, insecticides, fungicides, and herbicides are widely used in agricultural production.

[0003] However, pesticides can enter plants through various pathways, such as direct manual spraying, long-term accumulation in the soil, irrigation with contaminated water, and even cross-contamination during transportation and storage. Although pesticides sprayed directly on crops gradually degrade during the growth cycle due to factors such as sunlight and rainfall, the rate of degradation is affected by the chemical properties of the pesticide itself and environmental conditions. Therefore, even after degradation, pesticide residues may remain in plant tissues.

[0004] Currently, pesticide residues exceeding safe levels are sometimes detected in extracts obtained through conventional plant extraction methods. This not only affects the quality of the extracts but may also pose potential risks to human health. Therefore, researching an effective method for removing pesticide residues from extracts is of paramount importance. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for removing pesticide residues from extracts, which can efficiently reduce pesticide residues while ensuring the purity of the extract. It is applicable to the removal of pesticide residues from various plant extracts, traditional Chinese medicine extracts, and fruit and vegetable extracts.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] A method for removing pesticide residues from an extract includes the following steps:

[0008] S1. Dissolve the extract in an aqueous ethanol solution to form a solution;

[0009] S2. Add 0.4%-0.8% of the adsorbent to the solution, stir thoroughly, allow to settle, and filter the supernatant.

[0010] S3. Pass the supernatant through a macroporous resin at a flow rate of 3-6 BV / h and collect the effluent.

[0011] S4. Using a deep eutectic solvent as an entrainer, the effluent is extracted using supercritical carbon dioxide extraction to obtain an extract free of pesticide residues.

[0012] Through a multi-step process involving adsorption, macroporous resin, and supercritical carbon dioxide extraction, pesticide residues in the extract are effectively removed, ensuring that the pesticide residue levels in the final extract are below the detection limit.

[0013] Preferably, the alcohol content of the ethanol aqueous solution in step S1 is 90%-100%.

[0014] Preferably, the adsorbent in step S2 is made from the following raw materials in parts by weight: 25-30 parts modified diatomaceous earth, 20-25 parts aminated silica, and 10-15 parts nano-iron oxide-carbon nanotube composite.

[0015] Preferably, the preparation steps of the modified diatomaceous earth include:

[0016] A1. Soak diatomaceous earth in 0.1 mol / L dilute hydrochloric acid solution and stir for 2-3 hours to remove impurities. Wash repeatedly until the pH of the solution is close to neutral to obtain pretreated diatomaceous earth.

[0017] Immersing diatomaceous earth in a dilute hydrochloric acid solution effectively removes impurities from its surface and interior, such as inorganic contaminants like metal ions and carbonates. Acid treatment improves the purity of the diatomaceous earth and increases its surface active sites, promoting subsequent modification reactions. Washing is continued until the solution pH is close to neutral to prevent acidic substances from interfering with the subsequent precipitation of magnetic particles.

[0018] A2. Dissolve FeCl3·6H2O and FeSO4·7H2O in water, stir well, and prepare a mixed iron salt solution. Heat the mixed iron salt solution to 70-90℃, and slowly add 25% concentrated ammonia water until the pH value reaches 10. Maintain magnetic stirring during the process. Precipitation begins to form. Continue the reaction for 25-35 minutes, and then wash the precipitate.

[0019] In a mixed solution of iron salts, the pH is adjusted to alkaline by adding concentrated ammonia, thus making the Fe... 3+ and Fe 2+Ions undergo a chemical reaction in solution to generate magnetic nano-iron oxide (Fe3O4). This process is a co-precipitation reaction, and the efficient formation of Fe3O4 is promoted by controlling the temperature (70-90℃) and pH value (approximately 10). Simultaneously, magnetic stirring helps to form a uniform precipitate and prevents particle agglomeration.

[0020] A3. Add the precipitate and sodium dodecyl sulfonate together to ethanol to form a suspension. Add the pretreated diatomaceous earth to the suspension and ultrasonically disperse for 25-35 minutes to form a composite material.

[0021] In a suspension formed in ethanol, the addition of sodium dodecyl sulfonate, a surfactant, stabilizes the nanoparticles, prevents agglomeration, and promotes uniform dispersion. Based on this, pretreated diatomaceous earth is ultrasonically dispersed in the suspension, enhancing the contact between the nanoparticles and the pores and active sites on the diatomaceous earth surface. This leads to the formation of a stable composite material through physical adsorption and electrostatic interactions. The ultrasonic dispersion process further breaks up nanoparticle clusters, ensuring uniform adhesion of magnetic particles to the diatomaceous earth.

[0022] A4. The composite material is separated from the liquid phase by an external magnetic field, washed, and then dried at 80-100℃ for 7-8 hours to obtain the modified diatomaceous earth.

[0023] The separation of composite materials using an external magnetic field is based on the magnetic properties of Fe3O4 nanoparticles. This process allows for rapid and efficient separation of the composite material from the liquid phase. A washing step removes excess surfactants and unreacted residues, ensuring the purity of the composite material. Subsequently, drying at 80-100℃ completely removes moisture from the composite material, ensuring its stability.

[0024] In an iron salt solution, the pH is adjusted with ammonia. The resulting iron oxide precipitate binds with diatomaceous earth, enhancing its surface activity and thus facilitating the selective adsorption of molecules with polar groups in pesticide residues. The addition of sodium dodecyl sulfate further modifies the surface properties of diatomaceous earth, adjusting its pore size and hydrophobicity, resulting in a stronger adsorption capacity for pesticide residues. The iron oxide particles provide metal ion sites on the modified diatomaceous earth surface, allowing it to form complexes with pesticide molecules containing ligands, further enhancing the adsorption effect.

[0025] Preferably, the preparation steps of the aminated silica include:

[0026] B1. Soak the silica particles in a 0.1 mol / L dilute hydrochloric acid solution, stir for 1.5-2.5 hours, and wash repeatedly until the pH of the washing solution is close to neutral.

[0027] B2. Mix anhydrous ethanol and water in a 95:5 ratio to form a mixed solution, then add γ-aminopropyltriethoxysilane and stir the solution for 25-35 minutes to form a γ-aminopropyltriethoxysilane solution.

[0028] B3. The pretreated silica is slowly added to a solution of γ-aminopropyltriethoxysilane and reacted at room temperature for 6-12 hours to form aminated silica. The silica is washed 3-5 times and dried to obtain the aminated silica.

[0029] By hydrolyzing a silane coupling agent (γ-aminopropyltriethoxysilane) and condensing it with hydroxyl groups on the surface of silica, amino functional groups are introduced into the silica surface, making it functionalized. This allows it to interact with hydrogen bonds or polar groups in the pesticide molecule structure, thus effectively adsorbing pesticides.

[0030] Preferably, the preparation steps of the nano-iron oxide-carbon nanotube composite include:

[0031] C1. Sonicate carbon nanotubes in a mixed acid for 2-3 hours, wash, and dry for 2-4 hours to obtain pretreated carbon nanotubes;

[0032] C2. Dissolve ferric chloride in deionized water to form FeCl3 solution, add ethylene glycol to FeCl3 solution, stir well, heat at 85-95℃ for 2-3 hours, add 2mol / L sodium hydroxide solution to react, collect nano-iron oxide nanoparticles by centrifugation, wash 3-5 times, dry, and disperse the nano-iron oxide nanoparticles in ethylene glycol;

[0033] C3. Disperse the pretreated carbon nanotubes in an appropriate amount of ethylene glycol and ultrasonically disperse them for 25-35 minutes to form a carbon nanotube solution. Add the iron oxide nanoparticle suspension dropwise to the solution and heat the mixture to 180°C in a nitrogen atmosphere. Maintain the reaction for 4-6 hours. Collect the precipitate of the nano-iron oxide-carbon nanotube composite by centrifugation, wash it 3-5 times, and dry it to obtain the nano-iron oxide-carbon nanotube composite.

[0034] Carbon nanotubes are acid-treated to enhance their surface activity, and then combined with nano-iron oxide to generate a composite material with both magnetic and strong adsorption properties. The carboxyl and hydroxyl groups on the surface of carbon nanotubes can physically adsorb onto iron oxide nanoparticles, forming a stable composite structure.

[0035] Carbon nanotubes possess a large specific surface area, and the attachment of nano-iron oxide to their surface can increase the active sites of the composite material. Through coordination or complexation between metal ions on the iron oxide surface and specific functional groups (such as carboxyl, hydroxyl, or phosphoryl groups) in pesticide molecules, the selective adsorption of pesticide residues is enhanced.

[0036] Preferably, the mixed acid comprises concentrated sulfuric acid and nitric acid in a volume ratio of 3:1.

[0037] Preferably, the macroporous resin in step S3 includes, but is not limited to, any one of HY-1 type macroporous adsorption resin, XAD-4 type macroporous adsorption resin, or D001 type macroporous adsorption resin.

[0038] Preferably, the deep eutectic solvent in step S4 is a mixture of choline chloride and glycerol in a 1:1 ratio, and the amount used is 10%-40% of the extract weight.

[0039] Preferably, in the supercritical carbon dioxide extraction process of step S4, the extraction pressure in the extraction vessel is 15-35 MPa, the extraction temperature is 35-75℃, the extraction time is 1-4 h, the carbon dioxide flow rate is 6-12 L / h, the separation vessel pressure is 5-10 MPa, and the separation vessel temperature is 30-50℃.

[0040] The beneficial effects of this invention are:

[0041] (1) In the process of removing pesticide residues, this invention avoids the use of any organic solvents and toxic or harmful substances as removal agents, thus possessing the unique advantages of a safe and reliable removal process without secondary pollution. This method not only effectively removes pesticide residues but also ensures that the treatment process is environmentally friendly, thereby guaranteeing the purity and safety of the final product;

[0042] (2) This invention utilizes adsorption, macroporous resin and supercritical carbon dioxide extraction in a multi-step process, which results in a high removal rate and a simple and easy process. It is especially suitable for the removal of pesticide residues such as organophosphorus, organochlorine, carbamate, pyrethroid, triazole, phenoxycarboxylic acid, neonicotinoid insecticides and amide herbicides. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0044] The extracts in all embodiments are ginseng extracts.

[0045] Example 1

[0046] This embodiment describes a method for removing pesticide residues from an extract.

[0047] S1. Dissolve 500g of ginseng extract in 5L of ethanol-water solution to form a solution;

[0048] S2. Add 0.4% of the adsorbent to the solution, stir thoroughly, let it settle, and filter the supernatant;

[0049] S3. Pass the supernatant through macroporous resin (HY-1 type macroporous adsorption resin) at a flow rate of 3 BV / h and collect the effluent;

[0050] S4. Using 250 ml of a deep eutectic solvent (a 1:1 mixture of choline chloride and glycerol) as an entrainer, the eluent was extracted using supercritical carbon dioxide extraction to obtain an extract free of pesticide residues. During the extraction process, the extraction pressure in the extraction vessel was 15 MPa, the extraction temperature was 35 °C, the extraction time was 4 h, the carbon dioxide flow rate was 6 L / h, the separation vessel pressure was 5 MPa, and the separation vessel temperature was 30 °C.

[0051] The adsorbent consists of 25g of modified diatomaceous earth, 20g of aminated silica, and 10g of nano-iron oxide-carbon nanotube composite. The preparation method of the adsorbent components is described below.

[0052] The preparation steps of modified diatomaceous earth include,

[0053] A1. Soak 30g of diatomaceous earth in 200mL of 0.1mol / L dilute hydrochloric acid solution and stir for 2 hours to remove impurities. Wash repeatedly until the pH of the solution is close to neutral to obtain pretreated diatomaceous earth.

[0054] A2. Dissolve 5.4g FeCl3·6H2O and 3.4g FeSO4·7H2O in 200mL of water, stir well to prepare a mixed iron salt solution, heat the mixed iron salt solution to 70℃, and slowly add 25% concentrated ammonia water until the pH value reaches 10. Maintain magnetic stirring during the process. Precipitation begins to form. Continue the reaction for 25 minutes, and then wash the precipitate.

[0055] A3. Add the precipitate and 0.6g sodium dodecyl sulfonate to ethanol to form a suspension. Add 30g of pretreated diatomaceous earth to the suspension and ultrasonically disperse for 25 minutes to form a composite material.

[0056] A4. The composite material is separated from the liquid phase by an external magnetic field, washed, and then dried at 80°C for 8 hours to obtain modified diatomaceous earth.

[0057] The preparation steps of aminated silica include:

[0058] B1. Soak 25g of silica particles in 200mL of 0.1mol / L dilute hydrochloric acid solution, stir for 1.5 hours, and wash repeatedly until the pH of the washing solution is close to neutral.

[0059] B2. Anhydrous ethanol and water are mixed in a 95:5 ratio to form a mixed solution. Then, 6 mL of γ-aminopropyltriethoxysilane is added, and the solution is stirred for 25 minutes to form a γ-aminopropyltriethoxysilane solution.

[0060] B3. The pretreated silica was slowly added to a solution of γ-aminopropyltriethoxysilane and reacted at room temperature for 6 hours to form aminated silica. The silica was washed 3 times and dried to obtain aminated silica.

[0061] The preparation steps of the nano-iron oxide-carbon nanotube composite include:

[0062] C1. 15g of carbon nanotubes were ultrasonically treated in a mixed acid for 2 hours, washed, and dried for 2 hours to obtain pretreated carbon nanotubes.

[0063] C2. Dissolve 5.4g of ferric chloride in 150mL of deionized water to form FeCl3 solution. Add 100mL of ethylene glycol to the FeCl3 solution, stir well, and heat at 85℃ for 2 hours. Add 50mL of 2mol / L sodium hydroxide solution to react. Collect the nano-iron oxide nanoparticles by centrifugation, wash 3-5 times, dry, and disperse the nano-iron oxide nanoparticles in ethylene glycol.

[0064] C3. Disperse the pretreated carbon nanotubes in an appropriate amount of ethylene glycol and use an ultrasonic device to ultrasonically disperse them for 25-35 minutes to form a carbon nanotube solution. Add the iron oxide nanoparticle suspension dropwise, heat the mixed solution to 180°C in a nitrogen atmosphere, and maintain the reaction for 4 hours. Collect the precipitate of the nano-iron oxide-carbon nanotube composite by centrifugation, wash it 3 times, and dry it to obtain the nano-iron oxide-carbon nanotube composite.

[0065] Example 2

[0066] This embodiment is a method for removing pesticide residues from extracts.

[0067] S1. Dissolve 500g of ginseng extract in 5L of ethanol-water solution to form a solution;

[0068] S2. Add 0.6% of the adsorbent to the solution, stir thoroughly, let it settle, and filter the supernatant;

[0069] S3. Pass the supernatant through a macroporous resin (XAD-4 type macroporous adsorption resin) at a flow rate of 4.5 BV / h and collect the effluent.

[0070] S4. Using 375 ml of a deep eutectic solvent (a 1:1 mixture of choline chloride and glycerol) as an entrainer, the eluent was extracted using supercritical carbon dioxide extraction to obtain an extract free of pesticide residues. During the extraction process, the extraction pressure in the extraction vessel was 25 MPa, the extraction temperature was 55 °C, the extraction time was 2.5 h, the carbon dioxide flow rate was 9 L / h, the separation vessel pressure was 7.5 MPa, and the separation vessel temperature was 40 °C.

[0071] The adsorbent consists of 27.5g of modified diatomaceous earth, 22.5g of aminated silica, and 12.5g of nano-iron oxide-carbon nanotube composite. The preparation method of the adsorbent components is described below.

[0072] The preparation steps of modified diatomaceous earth include,

[0073] A1. Soak 30g of diatomaceous earth in 200mL of 0.1mol / L dilute hydrochloric acid solution and stir for 2.5 hours to remove impurities. Wash repeatedly until the pH of the solution is close to neutral to obtain pretreated diatomaceous earth.

[0074] A2. Dissolve 5.4g FeCl3·6H2O and 3.4g FeSO4·7H2O in 200mL of water, stir well to prepare a mixed iron salt solution, heat the mixed iron salt solution to 80℃, and slowly add 25% concentrated ammonia water until the pH value reaches 10. Maintain magnetic stirring during the process. Precipitation begins to form. Continue the reaction for 30 minutes, and then wash the precipitate.

[0075] A3. Add the precipitate and 0.6g sodium dodecyl sulfonate to ethanol to form a suspension. Add 30g of pretreated diatomaceous earth to the suspension and ultrasonically disperse for 30 minutes to form a composite material.

[0076] A4. The composite material is separated from the liquid phase by an external magnetic field, washed, and then dried at 90°C for 7.5 hours to obtain modified diatomaceous earth.

[0077] The preparation steps of aminated silica include:

[0078] B1. Soak 25g of silica particles in 200mL of 0.1mol / L dilute hydrochloric acid solution, stir for 2 hours, and wash repeatedly until the pH of the washing solution is close to neutral.

[0079] B2. Anhydrous ethanol and water are mixed in a 95:5 ratio to form a mixed solution. Then, 6 mL of γ-aminopropyltriethoxysilane is added, and the solution is stirred for 30 minutes to form a γ-aminopropyltriethoxysilane solution.

[0080] B3. The pretreated silica was slowly added to a solution of γ-aminopropyltriethoxysilane and reacted at room temperature for 9 hours to form aminated silica. The silica was washed 4 times and dried to obtain aminated silica.

[0081] The preparation steps of the nano-iron oxide-carbon nanotube composite include:

[0082] C1. 15g of carbon nanotubes were ultrasonically treated in a mixed acid for 2.5 hours, washed, and dried for 3 hours to obtain pretreated carbon nanotubes.

[0083] C2. Dissolve 5.4 g of ferric chloride in 150 mL of deionized water to form FeCl3 solution. Add 100 mL of ethylene glycol to the FeCl3 solution, stir well, and heat at 90 °C for 2.5 hours. Add 50 mL of 2 mol / L sodium hydroxide solution to react. Collect the nano-iron oxide nanoparticles by centrifugation, wash 4 times, dry, and disperse the nano-iron oxide nanoparticles in ethylene glycol.

[0084] C3. Disperse the pretreated carbon nanotubes in an appropriate amount of ethylene glycol and sonicate them for 30 minutes using an ultrasonic device to form a carbon nanotube solution. Add the iron oxide nanoparticle suspension dropwise, heat the mixed solution to 180°C in a nitrogen atmosphere, and maintain the reaction for 5 hours. Collect the precipitate of the nano-iron oxide-carbon nanotube composite by centrifugation, wash it 4 times, and dry it to obtain the nano-iron oxide-carbon nanotube composite.

[0085] Example 3

[0086] This embodiment describes a method for removing pesticide residues from extracts.

[0087] S1. Dissolve 500g of ginseng extract in 5L of ethanol-water solution to form a solution;

[0088] S2. Add 0.8% of the adsorbent to the solution, stir thoroughly, let it settle, and filter the supernatant;

[0089] S3. Pass the supernatant through a macroporous resin (D001 type macroporous adsorption resin) at a flow rate of 6 BV / h and collect the effluent.

[0090] S4. Using 500 ml of a deep eutectic solvent (a 1:1 mixture of choline chloride and glycerol) as an entrainer, the eluent was extracted using supercritical carbon dioxide extraction to obtain an extract free of pesticide residues. During the extraction process, the extraction pressure in the extraction vessel was 35 MPa, the extraction temperature was 75 °C, the extraction time was 1 h, the carbon dioxide flow rate was 12 L / h, the separation vessel pressure was 10 MPa, and the separation vessel temperature was 50 °C.

[0091] The adsorbent consists of 30g of modified diatomaceous earth, 25g of aminated silica, and 15g of nano-iron oxide-carbon nanotube composite. The preparation method of the adsorbent components is as follows.

[0092] The preparation steps of modified diatomaceous earth include,

[0093] A1. Soak 30g of diatomaceous earth in 200mL of 0.1mol / L dilute hydrochloric acid solution, stir for 3 hours to remove impurities, and wash repeatedly until the pH of the solution is close to neutral to obtain pretreated diatomaceous earth;

[0094] A2. Dissolve 5.4g FeCl3·6H2O and 3.4g FeSO4·7H2O in 200mL of water, stir well to prepare a mixed iron salt solution, heat the mixed iron salt solution to 90℃, and slowly add 25% concentrated ammonia water until the pH value reaches 10. Maintain magnetic stirring during the process. Precipitation begins to form. Continue the reaction for 25-35 minutes, and then wash the precipitate.

[0095] A3. Add the precipitate and 0.6g sodium dodecyl sulfonate to ethanol to form a suspension. Add 30g of pretreated diatomaceous earth to the suspension and ultrasonically disperse for 35 minutes to form a composite material.

[0096] A4. The composite material is separated from the liquid phase by an external magnetic field, washed, and then dried at 80°C for 8 hours to obtain modified diatomaceous earth.

[0097] The preparation steps of aminated silica include:

[0098] B1. Soak 25g of silica particles in 200mL of 0.1mol / L dilute hydrochloric acid solution, stir for 2.5 hours, and wash repeatedly until the pH of the washing solution is close to neutral.

[0099] B2. Anhydrous ethanol and water are mixed in a 95:5 ratio to form a mixed solution. Then, 6 mL of γ-aminopropyltriethoxysilane is added, and the solution is stirred for 35 minutes to form a γ-aminopropyltriethoxysilane solution.

[0100] B3. The pretreated silica was slowly added to a solution of γ-aminopropyltriethoxysilane and reacted at room temperature for 12 hours to form aminated silica. The silica was washed 5 times and dried to obtain aminated silica.

[0101] The preparation steps of the nano-iron oxide-carbon nanotube composite include:

[0102] C1. 15g of carbon nanotubes were ultrasonically treated in a mixed acid for 3 hours, washed, and dried for 4 hours to obtain pretreated carbon nanotubes.

[0103] C2. Dissolve 5.4 g of ferric chloride in 150 mL of deionized water to form FeCl3 solution. Add 100 mL of ethylene glycol to the FeCl3 solution, stir well, and heat at 95 °C for 2 hours. Add 50 mL of 2 mol / L sodium hydroxide solution to react. Collect the nano-iron oxide nanoparticles by centrifugation, wash 5 times, dry, and disperse the nano-iron oxide nanoparticles in ethylene glycol.

[0104] C3. Disperse the pretreated carbon nanotubes in an appropriate amount of ethylene glycol and sonicate them for 35 minutes using an ultrasonic device to form a carbon nanotube solution. Add the iron oxide nanoparticle suspension dropwise, heat the mixed solution to 180°C in a nitrogen atmosphere, and maintain the reaction for 6 hours. Collect the precipitate of the nano-iron oxide-carbon nanotube composite by centrifugation, wash it 5 times, and dry it to obtain the nano-iron oxide-carbon nanotube composite.

[0105] Comparative Example 1

[0106] The difference between this embodiment and Embodiment 2 is that the adsorbent is replaced with ordinary activated carbon.

[0107] The pesticide residue content in the extract was detected using gas chromatography-mass spectrometry (GC-MS). The concentration of the pesticide residue (iprodione) was quantitatively analyzed by comparison with standards.

[0108] The experimental data are shown in Table 1.

[0109] Table 1

[0110]

[0111]

[0112] The detection limit is 0.01 ppm.

[0113] Compared to Comparative Example 1, Example 2, using modified diatomaceous earth, aminated silica, and nano-iron oxide-carbon nanotube composites as adsorbents in conjunction with supercritical carbon dioxide extraction, effectively removed iprodione residues with removal efficiencies exceeding 98.8%. This demonstrates that this method possesses extremely high pesticide residue removal capabilities.

[0114] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A method for removing pesticide residues from an extract, characterized in that: Includes the following steps, S1. Dissolve the extract in an aqueous ethanol solution to form a solution; S2. Add 0.4%-0.8% of the adsorbent to the solution, stir thoroughly, allow to settle, and filter the supernatant. S3. Pass the supernatant through a macroporous resin at a flow rate of 3-6 BV / h and collect the effluent. S4. Using a deep eutectic solvent as an entrainer, the effluent is extracted using supercritical carbon dioxide extraction to obtain an extract free of pesticide residues. The adsorbent in step S2 is made from the following raw materials in parts by weight: 25-30 parts modified diatomaceous earth, 20-25 parts aminated silica, and 10-15 parts nano-iron oxide-carbon nanotube composite. The preparation steps of the modified diatomaceous earth include: A1. Soak diatomaceous earth in 0.1 mol / L dilute hydrochloric acid solution and stir for 2-3 hours to remove impurities. Wash repeatedly until the pH of the solution is close to neutral to obtain pretreated diatomaceous earth. A2. Dissolve FeCl3·6H2O and FeSO4·7H2O in water, stir well, and prepare a mixed iron salt solution. Heat the mixed iron salt solution to 70-90℃, and slowly add 25% concentrated ammonia water until the pH value reaches 10. Maintain magnetic stirring during the process. Precipitation begins to form. Continue the reaction for 25-35 minutes, and then wash the precipitate. A3. Add the precipitate and sodium dodecyl sulfonate together to ethanol to form a suspension. Add the pretreated diatomaceous earth to the suspension and ultrasonically disperse for 25-35 minutes to form a composite material. A4. The composite material is separated from the liquid phase by an external magnetic field, washed, and dried at 80-100℃ for 7-8 hours to obtain the modified diatomaceous earth. The preparation steps of the aminated silicon dioxide include: B1. Soak the silica particles in a 0.1 mol / L dilute hydrochloric acid solution, stir for 1.5-2.5 hours, and wash repeatedly until the pH of the washing solution is close to neutral. B2. Mix anhydrous ethanol and water in a 95:5 ratio to form a mixed solution, then add γ-aminopropyltriethoxysilane and stir the solution for 25-35 minutes to form a γ-aminopropyltriethoxysilane solution. B3. The pretreated silica is slowly added to a solution of γ-aminopropyltriethoxysilane and reacted at room temperature for 6-12 hours to form aminated silica. The silica is then washed 3-5 times and dried to obtain the aminated silica. The preparation steps of the nano-iron oxide-carbon nanotube composite include, C1. Sonicate carbon nanotubes in a mixed acid for 2-3 hours, wash, and dry for 2-4 hours to obtain pretreated carbon nanotubes; C2. Dissolve ferric chloride in deionized water to form FeCl3 solution, add ethylene glycol to FeCl3 solution, stir well, heat at 85-95℃ for 2-3 hours, add 2mol / L sodium hydroxide solution to react, collect nano-iron oxide nanoparticles by centrifugation, wash 3-5 times, dry, and disperse the nano-iron oxide nanoparticles in ethylene glycol; C3. Disperse the pretreated carbon nanotubes in an appropriate amount of ethylene glycol and ultrasonically disperse them for 25-35 minutes to form a carbon nanotube solution. Add the iron oxide nanoparticle suspension dropwise to the solution and heat the mixture to 180°C in a nitrogen atmosphere. Maintain the reaction for 4-6 hours. Collect the precipitate of the nano-iron oxide-carbon nanotube composite by centrifugation, wash it 3-5 times, and dry it to obtain the nano-iron oxide-carbon nanotube composite.

2. The method for removing pesticide residues from an extract according to claim 1, characterized in that: The alcohol content of the ethanol aqueous solution in step S1 is 90%-100%.

3. The method for removing pesticide residues from an extract according to claim 1, characterized in that: The mixed acid comprises concentrated sulfuric acid and nitric acid in a volume ratio of 3:

1.

4. The method for removing pesticide residues from an extract according to claim 1, characterized in that: The macroporous resin in step S3 includes one of HY-1 type macroporous adsorption resin, XAD-4 type macroporous adsorption resin, or D001 type macroporous adsorption resin.

5. The method for removing pesticide residues from an extract according to claim 1, characterized in that: The deep eutectic solvent in step S4 is a mixture of choline chloride and glycerol in a 1:1 ratio, and the amount used is 10%-40% of the weight of the extract.

6. The method for removing pesticide residues from an extract according to claim 1, characterized in that: In the supercritical carbon dioxide extraction process of step S4, the extraction pressure in the extraction vessel is 15-35 MPa, the extraction temperature is 35-75℃, the extraction time is 1-4 h, the carbon dioxide flow rate is 6-12 L / h, the separation vessel pressure is 5-10 MPa, and the separation vessel temperature is 30-50℃.

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