Method for removing pesticide residues in extract

Abstract

The invention relates to the technical field of separation and extraction of natural products, and discloses a method for removing pesticide residues in an extract, which comprises the following steps: S1, dissolving the extract with an ethanol aqueous solution to form a solution; s2, adding 0.4%-0.8% of an adsorbent into the solution, fully stirring, settling, and filtering supernate; s3, enabling the supernate to pass through macroporous resin at the flow speed of 3-6BV / h, and collecting effluent; and S4, extracting the effluent by using a supercritical carbon dioxide extraction method by taking the deep eutectic solvent as an entrainer, and separating to obtain an extract from which pesticide residues are removed. The adsorbent is prepared from the following raw materials in parts by weight: 25-30 parts of modified diatomite, 20-25 parts of aminated silicon dioxide and 10-15 parts of a nano iron oxide-carbon nanotube compound. According to the method, pesticide residues can be efficiently reduced, and meanwhile the purity of the extract is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of separation and extraction of natural products, and in particular to a method for removing pesticide residues in an extract. Background Art

[0002] The development of agriculture is inseparable from the use of pesticides, which can effectively control the damage of crops by biological factors such as pests, pathogens and weeds, thereby ensuring the yield and quality of crops. Pesticides can be divided into insecticides, fungicides, herbicides, acaricides and plant growth regulators according to the different targets of prevention and control. Among them, insecticides such as fenthion and bifenthrin are used to prevent and control pests and diseases spread by insects; fungicides such as pentachloronitrobenzene and vinylchloride are used to combat diseases caused by fungi and bacteria; herbicides such as atrazine, terbuthion and promethazine are used to inhibit the growth of weeds; acaricides such as chlorpyrifos, dichlorvos and cypermethrin are used to kill small arthropods such as ticks and mites; plant growth regulators such as auxins and gibberellins are used to regulate the growth and development of plants. Among these categories, insecticides, fungicides and herbicides are widely used in agricultural production.

[0003] However, pesticides can enter plants through many ways, such as direct manual spraying, long-term accumulation in the soil, irrigation from polluted water sources, and even cross-contamination during transportation and storage. Although pesticides sprayed directly on crops will gradually degrade under the influence of factors such as light and rain during the growth cycle, the rate of degradation is affected by the chemical properties of the pesticide itself and environmental conditions. Therefore, even degraded pesticides may leave residues in plant tissues.

[0004] At present, the problem of excessive pesticide residues is sometimes detected in extracts obtained by conventional plant extraction methods. This not only affects the quality of the extracts, but also poses a potential risk to human health. Therefore, it is particularly important to study an effective method for removing pesticide residues from extracts. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for removing pesticide residues in an extract, which can effectively reduce pesticide residues while ensuring the purity of the extract. The method is suitable for removing pesticide residues in various plant extracts, Chinese medicine extracts, and fruit and vegetable extracts.

[0006] The present invention solves the above technical problems by the following technical means:

[0007] A method for removing pesticide residues in an extract comprises the following steps:

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

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

[0010] S3. The supernatant was passed through a macroporous resin at a flow rate of 3-6 BV / h, and the effluent was collected;

[0011] S4. Using a deep eutectic solvent as an entrainer, the effluent is extracted by supercritical carbon dioxide extraction to separate and obtain an extract with pesticide residues removed.

[0012] Through multi-step treatments including adsorption, macroporous resin and supercritical carbon dioxide extraction, pesticide residues in the extract are effectively removed, ensuring that the pesticide residues 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 of the following raw materials in parts by weight: 25-30 parts of modified diatomaceous earth, 20-25 parts of amino-silicon dioxide, and 10-15 parts of nano-iron oxide-carbon nanotube composite.

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

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

[0017] By soaking diatomite in a dilute hydrochloric acid solution, impurities on the surface and inside of the diatomite, such as metal ions, carbonates and other inorganic pollutants, can be effectively removed. The acid treatment improves the purity of the diatomite and increases its surface active points, which promotes the modification reaction in the subsequent steps. Washing until the pH value of the solution is close to neutral can prevent acidic substances from affecting the subsequent magnetic particle precipitation reaction.

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

[0019] In the iron salt mixed solution, the pH is adjusted to alkaline by adding concentrated ammonia water to make Fe 3+ and Fe 2+Ions react chemically in the solution to generate magnetic nano-iron oxide (Fe3O4). This process is a co-precipitation reaction, which promotes the efficient generation of Fe3O4 by controlling the temperature (70-90°C) and pH value (about 10). At the same time, magnetic stirring helps to form a uniform precipitation and avoid particle agglomeration.

[0020] A3. The precipitate was added to ethanol together with sodium dodecyl sulfate to form a suspension, the pretreated diatomaceous earth was added to the suspension, and ultrasonically dispersed for 25-35 minutes to form a composite material;

[0021] Adding the surfactant sodium dodecyl sulfate to the suspension formed in ethanol can stabilize the nanoparticles, prevent particle agglomeration, and promote uniform dispersion of the nanoparticles. On this basis, the pretreated diatomaceous earth is ultrasonically dispersed in the suspension to enhance the contact between the nanoparticles and the pores and active sites on the surface of the diatomaceous earth, forming a stable composite material through physical adsorption and electrostatic effects. The ultrasonic dispersion process can further break up the nanoparticle clusters and ensure that the magnetic particles are evenly attached to the diatomaceous earth.

[0022] A4. Separate the composite material from the liquid phase using an external magnetic field, wash, and dry the washed composite material at 80-100° C. for 7-8 hours to obtain the modified diatomaceous earth.

[0023] The use of an external magnetic field to separate composite materials is based on the magnetism of Fe3O4 nanoparticles. This process can quickly and efficiently separate the composite materials from the liquid phase. The washing step removes excess surfactants and unreacted residues to ensure the purity of the composite materials. Subsequently, the composite materials are dried at 80-100°C to completely remove moisture and ensure the stability of the materials.

[0024] The pH value of the iron salt solution is adjusted by ammonia water, and the resulting iron oxide precipitate combines with diatomite, which increases its surface activity, thereby facilitating the selective adsorption of molecules with polar groups in pesticide residues. The addition of sodium dodecyl sulfate can further modify the surface properties of diatomite, adjust the pore size and hydrophobicity, and make it have a stronger adsorption capacity for pesticide residues. The iron oxide particles provide metal ion sites on the surface of the modified diatomite, which can form complexes with pesticide molecules containing ligands, making the adsorption effect more significant.

[0025] Preferably, the preparation steps of the amino silicon dioxide 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 value of the washing solution is close to neutral;

[0027] B2. Anhydrous ethanol and water are mixed in a ratio of 95:5 to form a mixed solution, and then γ-aminopropyltriethoxysilane is added, and the solution is stirred for 25-35 minutes to form a γ-aminopropyltriethoxysilane solution

[0028] B3. Slowly add the pretreated silica to the γ-aminopropyltriethoxysilane solution, react at room temperature for 6-12 hours to form amino silica, wash 3-5 times, and dry to obtain the amino silica.

[0029] By hydrolyzing the silane coupling agent (γ-aminopropyltriethoxysilane) and reacting it with the hydroxyl groups on the surface of silica, amino functional groups are introduced onto the surface of silica to functionalize the surface. The amino functional groups can interact with the hydrogen bonds or polar groups in the molecular structure of the pesticide and effectively adsorb the pesticide.

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

[0031] C1. The carbon nanotubes were ultrasonically treated in a mixed acid for 2-3 hours, washed, and dried for 2-4 hours to obtain pretreated carbon nanotubes;

[0032] C2. dissolving ferric chloride in deionized water to form a FeCl3 solution, adding ethylene glycol to the FeCl3 solution, stirring evenly, and heating at 85-95°C for 2-3 hours, adding 2 mol / L sodium hydroxide solution to react, collecting nano iron oxide nanoparticles by centrifugation, washing 3-5 times, and drying, and dispersing the nano iron oxide nanoparticles in ethylene glycol;

[0033] C3. Disperse the pretreated carbon nanotubes in an appropriate amount of ethylene glycol, use an ultrasonic device to perform ultrasonic dispersion 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 keep the reaction for 4-6 hours, collect the nano iron oxide-carbon nanotube complex precipitate by centrifugation, wash 3-5 times, and dry to obtain the nano iron oxide-carbon nanotube complex.

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

[0035] Carbon nanotubes have a large specific surface area, and the attachment of nano-iron oxide to their surface can increase the active sites of the composite material. The metal ions on the surface of the iron oxide coordinate or complex with specific functional groups (such as carboxyl, hydroxyl or phosphoryl) in the pesticide molecules, thereby enhancing the selective adsorption of pesticide residues.

[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 macroporous adsorption resin, XAD-4 macroporous adsorption resin or D001 macroporous adsorption resin.

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

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

[0040] Beneficial effects of the present invention:

[0041] (1) The present invention avoids the use of any organic solvents and toxic and hazardous substances as removal agents in the process of removing pesticide residues, and thus has 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 ensuring the purity and safety of the final product;

[0042] (2) The present invention utilizes adsorption, macroporous resin and supercritical carbon dioxide extraction multi-step treatment, which makes it have the characteristics of high removal rate and simple and easy process. It is particularly suitable for the removal of pesticide residues such as organophosphorus, organochlorine, carbamate, pyrethroid, triazole, phenoxycarboxylic acid, neonicotinoid insecticides and amide herbicides. DETAILED DESCRIPTION

[0043] The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention:

[0044] The extracts of all examples were ginseng extracts

[0045] Example 1

[0046] This embodiment is a method for removing pesticide residues in an extract.

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

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

[0049] S3. The supernatant was passed through a macroporous resin (HY-1 macroporous adsorption resin) at a flow rate of 3 BV / h, and the effluent was collected;

[0050] S4. Using 250 ml of deep eutectic solvent (a mixture of choline chloride and glycerol in a ratio of 1:1) as an entrainer, the effluent was extracted by supercritical carbon dioxide extraction to separate the extract from which the pesticide residues were removed. During the extraction process, the extraction pressure of the extraction kettle 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 kettle pressure was 5 MPa, and the separation kettle temperature was 30°C.

[0051] The adsorbent is composed of 25 g of modified diatomaceous earth, 20 g of amino silicon dioxide, and 10 g of nano iron oxide-carbon nanotube composite. The following is the preparation method of the adsorbent component.

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

[0053] A1. Soak 30 g of diatomaceous earth in 200 mL of 0.1 mol / L dilute hydrochloric acid solution, stir for 2 hours to remove impurities, and wash repeatedly until the pH value 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 water, stir evenly to prepare an iron salt mixed solution, heat the iron salt mixed solution to 70℃, and slowly add 25% concentrated ammonia water until the pH value reaches 10. Keep magnetic stirring during the process. Precipitation begins to form. Continue the reaction for 25 minutes and wash the precipitate.

[0055] A3. The precipitate was added to ethanol together with 0.6 g of sodium dodecyl sulfate to form a suspension, 30 g of pretreated diatomaceous earth was added to the suspension, and ultrasonically dispersed for 25 minutes to form a composite material;

[0056] A4. Separate the composite material from the liquid phase using an external magnetic field, wash, and dry the washed composite material at 80° C. for 8 hours to obtain modified diatomaceous earth.

[0057] The preparation steps of amino silicon dioxide 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 value of the washing solution is close to neutral;

[0059] B2. Anhydrous ethanol and water were mixed at a ratio of 95:5 to form a mixed solution, and then 6 mL of γ-aminopropyltriethoxysilane was added. The solution was stirred for 25 minutes to form a γ-aminopropyltriethoxysilane solution.

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

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

[0062] C1. 15 g 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. 5.4 g of ferric chloride was dissolved in 150 mL of deionized water to form a FeCl3 solution, 100 mL of ethylene glycol was added to the FeCl3 solution, stirred evenly, and heated at 85°C for 2 hours, 50 mL of 2 mol / L sodium hydroxide solution was added to react, nano-iron oxide nanoparticles were collected by centrifugation, washed 3-5 times, dried, and the nano-iron oxide nanoparticles were dispersed in ethylene glycol;

[0064] C3. Disperse the pretreated carbon nanotubes in an appropriate amount of ethylene glycol, use ultrasonic equipment to perform ultrasonic dispersion 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 keep the reaction for 4 hours, collect the nano-iron oxide-carbon nanotube complex precipitate by centrifugation, wash 3 times, and dry to obtain the nano-iron oxide-carbon nanotube complex.

[0065] Example 2

[0066] This embodiment is a method for removing pesticide residues in an extract.

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

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

[0069] S3. The supernatant was passed through a macroporous resin (XAD-4 macroporous adsorption resin) at a flow rate of 4.5 BV / h, and the effluent was collected;

[0070] S4. Using 375 ml of deep eutectic solvent (a mixture of choline chloride and glycerol in a ratio of 1:1) as an entrainer, the effluent was extracted by supercritical carbon dioxide extraction to separate the extract from which the pesticide residues were removed. During the extraction process, the extraction pressure of the extraction kettle 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 kettle pressure was 7.5 MPa, and the separation kettle temperature was 40°C.

[0071] The adsorbent is composed of 27.5 g of modified diatomaceous earth, 22.5 g of amino silicon dioxide, and 12.5 g of nano iron oxide-carbon nanotube composite. The following is the preparation method of the adsorbent component.

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

[0073] A1. 30 g of diatomaceous earth was soaked in 200 mL of 0.1 mol / L dilute hydrochloric acid solution, stirred for 2.5 hours to remove impurities, and washed repeatedly until the pH value of the solution was close to neutral to obtain pretreated diatomaceous earth;

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

[0075] A3. The precipitate was added to ethanol together with 0.6 g of sodium dodecyl sulfate to form a suspension, 30 g of pretreated diatomaceous earth was added to the suspension, and ultrasonically dispersed for 30 minutes to form a composite material;

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

[0077] The preparation steps of amino silicon dioxide 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 value of the washing solution is close to neutral;

[0079] B2. Anhydrous ethanol and water were mixed in a ratio of 95:5 to form a mixed solution, and then 6 mL of γ-aminopropyltriethoxysilane was added. The solution was stirred for 30 minutes to form a γ-aminopropyltriethoxysilane solution.

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

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

[0082] C1. 15 g 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. 5.4 g of ferric chloride was dissolved in 150 mL of deionized water to form a FeCl3 solution, 100 mL of ethylene glycol was added to the FeCl3 solution, stirred evenly, and heated at 90°C for 2.5 hours, 50 mL of 2 mol / L sodium hydroxide solution was added to react, nano-iron oxide nanoparticles were collected by centrifugation, washed 4 times, and dried, and the nano-iron oxide nanoparticles were dispersed in ethylene glycol;

[0084] C3. The pretreated carbon nanotubes were dispersed in an appropriate amount of ethylene glycol, and ultrasonic dispersion was performed using an ultrasonic device for 30 minutes to form a carbon nanotube solution. The iron oxide nanoparticle suspension was added dropwise, and the mixed solution was heated to 180°C in a nitrogen atmosphere and kept reacting for 5 hours. The nano-iron oxide-carbon nanotube complex was precipitated and collected by centrifugation, washed 4 times, and dried to obtain the nano-iron oxide-carbon nanotube complex.

[0085] Example 3

[0086] This embodiment is a method for removing pesticide residues in an extract.

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

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

[0089] S3. The supernatant was passed through a macroporous resin (D001 macroporous adsorption resin) at a flow rate of 6 BV / h, and the effluent was collected;

[0090] S4. Using 500 ml of deep eutectic solvent (a mixture of choline chloride and glycerol in a ratio of 1:1) as an entrainer, the effluent was extracted by supercritical carbon dioxide extraction to separate the extract from which the pesticide residues were removed. During the extraction process, the extraction pressure of the extraction kettle 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 kettle pressure was 10 MPa, and the separation kettle temperature was 50°C.

[0091] The adsorbent is composed of 30 g of modified diatomaceous earth, 25 g of amino-silicon dioxide, and 15 g of nano-iron oxide-carbon nanotube composite. The following is the preparation method of the adsorbent component.

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

[0093] A1. Soak 30 g of diatomaceous earth in 200 mL of 0.1 mol / L dilute hydrochloric acid solution, stir for 3 hours to remove impurities, and wash repeatedly until the pH value 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 water, stir evenly to prepare an iron salt mixed solution, heat the iron salt mixed solution to 90℃, and slowly add 25% concentrated ammonia water until the pH value reaches 10. Keep magnetic stirring during the process. Precipitation begins to form. Continue the reaction for 25-35 minutes and wash the precipitate.

[0095] A3. The precipitate was added to ethanol together with 0.6 g of sodium dodecyl sulfate to form a suspension, 30 g of pretreated diatomaceous earth was added to the suspension, and ultrasonically dispersed for 35 minutes to form a composite material;

[0096] A4. Separate the composite material from the liquid phase using an external magnetic field, wash, and dry the washed composite material at 80° C. for 8 hours to obtain modified diatomaceous earth.

[0097] The preparation steps of amino silicon dioxide 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 value of the washing solution is close to neutral;

[0099] B2. Anhydrous ethanol and water were mixed at a ratio of 95:5 to form a mixed solution, and then 6 mL of γ-aminopropyltriethoxysilane was added. The solution was stirred for 35 minutes to form a γ-aminopropyltriethoxysilane solution.

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

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

[0102] C1. 15 g 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. 5.4 g of ferric chloride was dissolved in 150 mL of deionized water to form a FeCl3 solution, 100 mL of ethylene glycol was added to the FeCl3 solution, stirred evenly, and heated at 95°C for 2 hours, 50 mL of 2 mol / L sodium hydroxide solution was added to react, nano-iron oxide nanoparticles were collected by centrifugation, washed 5 times, and dried, and the nano-iron oxide nanoparticles were dispersed in ethylene glycol;

[0104] C3. The pretreated carbon nanotubes were dispersed in an appropriate amount of ethylene glycol, and ultrasonic dispersion was performed using an ultrasonic device for 35 minutes to form a carbon nanotube solution. The iron oxide nanoparticle suspension was added dropwise, and the mixed solution was heated to 180°C in a nitrogen atmosphere and kept reacting for 6 hours. The nano-iron oxide-carbon nanotube complex was precipitated and collected by centrifugation, washed 5 times, and dried to obtain the nano-iron oxide-carbon nanotube complex.

[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 residues in the extracts were detected by gas chromatography-mass spectrometry (GC-MS). The concentration of the residual pesticide (procymidone) was quantitatively analyzed by comparison with the standard.

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

[0109] Table 1

[0110]

[0111]

[0112] The detection limit is 0.01ppm.

[0113] Compared with Comparative Example 1, Example 2 uses modified diatomaceous earth, amino silicon dioxide and nano iron oxide-carbon nanotube composite as adsorbents, combined with supercritical carbon dioxide extraction, to effectively remove procymidone residues, with a removal efficiency of more than 98.8%. This shows that this method has a very high ability to remove pesticide residues.

[0114] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.

Claims

1. A method for removing pesticide residues in an extract, characterized in that: The following steps are included: S1. dissolving the extract in an ethanol aqueous solution to form a solution; S2. Add 0.4%-0.8% of the adsorbent to the solution, stir thoroughly and allow to settle, and filter the supernatant; S3. The supernatant was passed through a macroporous resin at a flow rate of 3-6 BV / h, and the effluent was collected; S4. Using a deep eutectic solvent as an entrainer, the effluent is extracted by supercritical carbon dioxide extraction to separate and obtain an extract with pesticide residues removed.

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

3. A method for removing pesticide residues in an extract according to claim 1, characterized in that: The adsorbent in step S2 is made of the following raw materials in parts by weight: 25-30 parts of modified diatomaceous earth, 20-25 parts of amino silicon dioxide, and 10-15 parts of nano iron oxide-carbon nanotube composite.

4. A method for removing pesticide residues in an extract according to claim 3, characterized in that: The preparation steps of the modified diatomaceous earth include: A1. Soak the diatomaceous earth in a 0.1 mol / L dilute hydrochloric acid solution, stir for 2-3 hours to remove impurities, and wash repeatedly until the pH value of the solution is close to neutral to obtain pretreated diatomaceous earth; A2. Dissolve FeCl3·6H2O and FeSO4·7H2O in water, stir evenly to prepare an iron salt mixed solution, heat the iron salt mixed solution to 70-90°C, and slowly add 25% concentrated ammonia water until the pH value reaches 10. Keep magnetic stirring during the process. Precipitation begins to form. Continue the reaction for 25-35 minutes and wash the precipitate. A3. The precipitate was added to ethanol together with sodium dodecyl sulfate to form a suspension, the pretreated diatomaceous earth was added to the suspension, and ultrasonically dispersed for 25-35 minutes to form a composite material; A4. Separate the composite material from the liquid phase using an external magnetic field, wash, and dry the washed composite material at 80-100° C. for 7-8 hours to obtain the modified diatomaceous earth.

5. A method for removing pesticide residues in an extract according to claim 3, characterized in that: The preparation steps of the amino 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 value of the washing solution is close to neutral; B2. Anhydrous ethanol and water are mixed in a ratio of 95:5 to form a mixed solution, and then γ-aminopropyltriethoxysilane is added, and the solution is stirred for 25-35 minutes to form a γ-aminopropyltriethoxysilane solution B3. Slowly add the pretreated silica to the γ-aminopropyltriethoxysilane solution, react at room temperature for 6-12 hours to form amino silica, wash 3-5 times, and dry to obtain the amino silica.

6. A method for removing pesticide residues in an extract according to claim 3, characterized in that: The preparation steps of the nano iron oxide-carbon nanotube composite include: C1. The carbon nanotubes were ultrasonically treated in a mixed acid for 2-3 hours, washed, and dried for 2-4 hours to obtain pretreated carbon nanotubes; C2. dissolving ferric chloride in deionized water to form a FeCl3 solution, adding ethylene glycol to the FeCl3 solution, stirring evenly, and heating at 85-95°C for 2-3 hours, adding 2 mol / L sodium hydroxide solution to react, collecting nano iron oxide nanoparticles by centrifugation, washing 3-5 times, and drying, and dispersing the nano iron oxide nanoparticles in ethylene glycol; C3. Disperse the pretreated carbon nanotubes in an appropriate amount of ethylene glycol, use an ultrasonic device to perform ultrasonic dispersion 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 keep the reaction for 4-6 hours, collect the nano iron oxide-carbon nanotube complex precipitate by centrifugation, wash 3-5 times, and dry to obtain the nano iron oxide-carbon nanotube complex.

7. A method for removing pesticide residues in an extract according to claim 6, characterized in that: The mixed acid includes concentrated sulfuric acid and nitric acid in a volume ratio of 3:

1.

8. A method for removing pesticide residues in an extract according to claim 1, characterized in that: The macroporous resin in step S3 includes but is not limited to any one of HY-1 macroporous adsorption resin, XAD-4 macroporous adsorption resin or D001 macroporous adsorption resin.

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

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

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