Extraction process of vitex negundo oil

Abstract

The invention discloses an extraction process of chaste tree twig oil in the technical field of plant essential oil extraction. An ethanol aqueous solution is adopted for extraction, ultrasonic treatment and a composite enzymolysis technology are combined, the chaste tree twig cell structure is effectively destroyed, and the grease extraction rate is remarkably increased. And then selectively adsorbing impurities in the extracting solution by using a specially-made cobalt ferrite-deep eutectic solvent-biochar magnetic composite material, and realizing rapid separation through an external magnetic field. And the alkalescent ethanol water solution is adopted for elution, so that the structure stability of the deep eutectic solvent is protected while impurities are effectively desorbed. And finally, carrying out rotary evaporation and column chromatography refining to obtain the high-quality vitex negundo oil. The process integrates various extraction and purification technologies, has the advantages of high extraction efficiency, mild operation conditions, small environmental pollution and the like, and is particularly suitable for efficient extraction and refining of the vitex negundo oil.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plant essential oil extraction, and particularly relates to an extraction process of Vitex trifolia oil. BACKGROUND

[0002] As a wild shrub plant resource widely distributed in China, Vitex trifolia contains volatile oil in its leaves, flowers and seeds, which has high application value and can be used as a spice, a cosmetic ingredient and a potential medicinal ingredient. However, the traditional extraction method of Vitex trifolia oil has obvious limitations. The long-standing steam distillation method is simple to operate, but the oil yield is extremely low, which means that a large amount of plant resources are wasted, and long-time high-temperature heating can easily lead to the decomposition of heat-sensitive active ingredients, affecting the quality of the final product. In addition, another idea is to treat Vitex trifolia seeds with organic solvent extraction method, which can improve the oil yield, but a large amount of solvent is consumed in the production process, and the subsequent solvent recovery not only increases the energy consumption and production cost, but also brings the risk of environmental pollution and solvent residue, which is difficult to meet the requirements of modern green processing. Although the supercritical fluid extraction technology has excellent performance in yield and quality, its equipment investment is huge, and the operation and maintenance cost is high, which is economically poor for natural products such as Vitex trifolia oil with relatively low added value, and it is difficult to be widely applied in the industry. Therefore, developing a new type of Vitex trifolia oil extraction process that can balance high extraction efficiency, high product quality, low environmental impact and moderate cost has become a bottleneck that needs to be broken through in this field.

[0003] In the purification and refining process of oil, especially in the removal of polar impurities such as phenols, the traditional process faces severe challenges. Conventional methods such as alkali refining and adsorption often have problems such as complicated process, weak targeting, high loss rate of effective components, and possible secondary pollution. In recent years, deep eutectic solvent as a new type of green solvent has shown great potential in the field of selective separation. The halogen-free ternary deep eutectic solvent composed of betaine, glycolic acid and ethylene glycol shows excellent extraction efficiency for phenolic compounds in oil phase, and its entrainment rate for neutral oil is very low, showing excellent selectivity. This efficient separation behavior is mainly due to the strong hydrogen bonding and van der Waals force between deep eutectic solvent and phenolic compounds. However, how to efficiently and completely separate the liquid deep eutectic solvent from the treated oil phase, avoid its residue in the product, and realize the recycling of the solvent, is a practical problem that must be solved in continuous production.

[0004] In view of the above problems, the prior art lacks a comprehensive solution that can combine efficient extraction, targeted purification, green environmental protection and operational convenience. The technical personnel in the field have been seeking an innovative process which can greatly improve the yield and quality of Vitex oil and effectively overcome the shortcomings of the existing purification technology. For example, combining materials with specific adsorption function and magnetic carriers that are easy to separate to construct intelligent composite materials is considered a promising direction. By immobilizing deep eutectic solvent on a magnetic biochar carrier and introducing an external magnetic field for rapid separation, it is expected to simultaneously solve the problems of adsorption selectivity, separation efficiency and solvent residue. In addition, integrating physical or biological pretreatment methods such as ultrasonic waves and enzyme hydrolysis at the front end of the extraction process is expected to gently and efficiently destroy plant cell walls, further improving the initial oil extraction efficiency, thereby forming a complete, smooth and environmentally friendly technical path from raw materials to high-purity essential oil. The present application is born in such a technical background, aiming to provide a brand-new overall scheme for the extraction and purification of Vitex oil. SUMMARY

[0005] In view of the shortcomings of the prior art, the purpose of the present application is to provide an extraction process for Vitex oil.

[0006] In a first aspect of the present application, an extraction process for Vitex oil is provided, comprising the following steps: S1, crushing the leaves, flowers and branches of Vitex to obtain Vitex raw materials, mixing the Vitex raw materials with an ethanol aqueous solution and adding ascorbic acid to obtain a mixture; stirring the mixture at 48-52℃ and then performing ultrasonic treatment; subsequently adjusting the pH of the mixture to 4.5-5.5, adding cellulase, pectinase and protease, and performing enzyme hydrolysis at 50-55℃ to obtain an enzyme-hydrolyzed mixture; then performing cycle treatment by a high-pressure homogenizer to obtain a Vitex oil-water slurry; filtering the Vitex oil-water slurry through a screen to obtain a Vitex oil water-phase slurry; S2, placing the Vitex oil water-phase slurry in a reactor, adding cobalt ferrite-deep eutectic solvent-biochar magnetic composite material, and stirring at 38-42℃; standing; S3, applying a magnetic field outside the reactor to collect the liquid phase; washing the cobalt ferrite-deep eutectic solvent-biochar magnetic composite material with deionized water, transferring the washed cobalt ferrite-deep eutectic solvent-biochar magnetic composite material to an elution vessel, adding a sodium bicarbonate-ethanol-water mixed solution with a pH of 7.5-8.5, and stirring at 34-36℃; after elution, applying a magnetic field again, discarding the eluent containing impurities, and the regenerated composite material can be recycled; S4, the collected liquid phase is rotary evaporated at 38-42℃ under reduced pressure to obtain crude willow oil; the crude willow oil is refined by a chromatographic column filled with silica gel to obtain refined willow oil; the refined willow oil is mixed with anhydrous sodium sulfate, stirred, filtered, and purged with nitrogen.

[0007] In the present application, the willow oil extraction process described in the present application is a synergistic system integrating physical wall breaking, biological enzymatic hydrolysis, adsorption purification and magnetic separation technology. In the extraction stage, the mechanism mainly reflects the multiple and synergistic destruction of the cell wall of willow plant. After drying and crushing, the cell structure of the willow raw material is still relatively complete. Ethanol aqueous solution as an extraction solvent can better penetrate the cell membrane and dissolve the fat-soluble willow oil components than pure water. Ultrasonic treatment uses cavitation effect to generate strong shock waves and microjet, which physically tears the cell wall. Then, the composite enzyme preparation (cellulase, pectinase and protease) added in the weak acid environment plays a biological catalytic role. They can specifically hydrolyze cellulose, pectin and intracellular protein network that constitute the cell wall skeleton, respectively, thereby gently and efficiently completely disintegrating the cell structure, so that the intracellular willow oil is released into the water phase to the maximum extent. The subsequent high-pressure homogenization further breaks and homogenizes the oil droplets, forming a stable oil-water slurry, preparing for subsequent purification. In the purification stage, the core mechanism lies in the selective adsorption of the composite material to impurities and the application of magnetic separation technology. When the composite material is added to the willow oil water phase slurry, the deep eutectic solvent solidified on its surface begins to play a role. The deep eutectic solvent can selectively capture polar impurity molecules such as phenolic compounds and pigments in the slurry through the strong hydrogen bond network and van der Waals force provided by its components (betaine, glycollic acid, ethylene glycol), while adsorbing little of the main components of the target willow oil such as neutral triglycerides. Therefore, after adsorption by the composite material and separation using a magnetic field, the collected liquid phase is the purified willow oil phase, which guarantees the purity and yield of the willow oil. After adsorption, the composite material with adsorbed impurities can be quickly settled and separated from the purified oil phase by applying a magnetic field of a certain intensity outside the reactor due to the excellent magnetic properties of the composite material. By collecting the liquid phase and performing subsequent treatment, crude willow oil can be obtained. This process is efficient and energy-saving, avoiding tedious centrifugation or filtration operations. In the subsequent elution step, a weakly alkaline sodium bicarbonate-ethanol-water mixed solution is used as an eluent. The alkaline environment can break the hydrogen bond between the deep eutectic solvent and the impurity phenols, and ethanol can help dissolve the organic impurities eluted, thereby gently desorbing the impurities from the composite material, forming an impurity-containing eluent which is discarded, while not destroying the structure of the deep eutectic solvent, so that the composite material with adsorbed impurities can be regenerated and recycled. Finally, the refined willow oil is removed from trace amounts of solvent and water to obtain high-quality refined willow oil products.

[0008] As a preferred technical scheme of the present application, in step S1, the mixture is stirred at 48-52℃ for 2-4h.

[0009] As a preferred technical scheme of the present application, in step S2, the stirring time is 90-120min at 38-42℃.

[0010] As a preferred technical scheme of the present application, in step S3, the strength of the magnetic field applied outside the reactor is 0.4-0.6T.

[0011] As a preferred technical scheme of the present application, in step S4, the eluent of the chromatographic column filled with silica gel is a mixed solution of n-hexane and ethyl acetate.

[0012] As a preferred technical scheme of the present application, the preparation steps of the cobalt ferrite-eutectic solvent-biochar magnetic composite material include: A1, dissolving cobalt nitrate hexahydrate and iron nitrate nonahydrate in deionized water and stirring; adjusting the pH to 11-12 to obtain a mixed solution; transferring the mixed solution to a high-pressure reaction kettle and reacting at 195-205℃; after the reaction is completed, naturally cooling to room temperature, separating the precipitate using an external magnetic field, washing with anhydrous ethanol and deionized water alternately, and finally drying in a vacuum drying oven at 75-85℃ to obtain cobalt ferrite nano powder; A2, drying the sludge at 104-106℃, crushing and sieving to obtain dried sludge powder; mixing the dried sludge powder with an aqueous solution of iron chloride for impregnation to obtain an impregnated mixture; pyrolyzing the impregnated mixture in a tube furnace at 595-605℃ under nitrogen protection, after pyrolysis is completed, naturally cooling to room temperature, washing with deionized water until neutral, and then drying at 75-85℃ to obtain magnetic sludge-based biochar; A3, mixing betaine with glycollic acid and ethylene glycol and stirring at 78-82℃ to obtain a deep eutectic solvent; A4, dispersing the magnetic sludge-based biochar in the deep eutectic solvent, adding epichlorohydrin, ultrasonic dispersion, adding cobalt ferrite nano powder, and then stirring at 78-82℃ for reaction; after the reaction is completed, separating the product using an external magnetic field, washing the product with anhydrous ethanol, and finally drying in a vacuum drying oven at 75-85℃.

[0013] In the present application, the preparation of the cobalt ferrite-deep eutectic solvent-biochar magnetic composite material is a multi-step precise assembly and functionalization process, and the core is to construct a functional material with high adsorption capacity and convenient magnetic separation characteristics. First, in the synthesis stage of cobalt ferrite nanopowder, cobalt nitrate hexahydrate and iron nitrate nonahydrate are used as metal precursors, and the hydrothermal reaction is completed in a strong alkaline environment. The key mechanism is that cobalt ions and iron ions co-precipitate and crystallize under high temperature and high pressure conditions, directly forming cobalt ferrite with a spinel structure. This structure endows the nanopowder with strong intrinsic magnetism, and the high saturation magnetization lays a solid foundation for the subsequent magnetic response separation of the composite material. Second, the preparation of the magnetic sludge-based biochar realizes the unity of carrier functionalization and waste resource utilization. The residual sludge of the sewage treatment plant itself is rich in organic matter and inorganic ingredients. Under the condition of limited oxygen, high-temperature pyrolysis is carried out, and the organic matter is carbonized to form a biochar skeleton rich in pore structure, and the added ferric chloride is reduced during the pyrolysis process to generate magnetic iron oxides, which are in-situ embedded in the pores and surface of the biochar. This process not only utilizes the waste sludge, but also endows the biochar with preliminary magnetism, and the large specific surface area and rich surface functional groups also provide an ideal platform for subsequent loading. Finally, the assembly of the composite material is the key to functional integration. The deep eutectic solvent composed of betaine, glycolic acid and ethylene glycol prepared in the step, as a green and designable solvent, contains a large number of active groups such as hydroxyl and carboxyl groups in the molecule. Under the cross-linking action of epichlorohydrin, the deep eutectic solvent is anchored in the skeleton and pores of the magnetic biochar through covalent bonds. This immobilization process mainly fixes the matrix of the deep eutectic solvent, and exposes and retains a large number of its polar functional groups. Subsequently, the introduction of cobalt ferrite nanopowder, under the action of ultrasonic dispersion and stirring, the metal ions on its surface can further coordinate with the unreacted functional groups in the deep eutectic solvent, and may also be attached to the biochar through physical adsorption. In the finally formed composite material, the biochar serves as a three-dimensional skeleton to provide support and mass transfer channels; the cobalt ferrite serves as the main magnetic source to ensure that the material can be quickly manipulated by an external magnetic field; and the immobilized deep eutectic solvent becomes the key active site for selectively adsorbing polar impurities such as pigments and phenolic acids in jiangtiao oil.

[0014] As a preferred technical solution of the present application, in step A1, the mass ratio of cobalt nitrate hexahydrate to iron nitrate nonahydrate is 1:2.8.

[0015] As a preferred technical solution of the present application, in step A2, the pyrolysis time in the tube furnace at 595-605℃ is 2-4h.

[0016] As a preferred technical solution of the present application, in step A3, the mass ratio of betaine, glycolic acid and ethylene glycol is 10.0:6.1:4.7.

[0017] As a preferred technical scheme of the present application, the reaction time in step A4 is 6-8h under stirring at 78-82℃.

[0018] Compared with the prior art, the present application has the following beneficial effects: (1) The present process realizes significant improvement of extraction efficiency and product quality in the extraction stage of willow branch oil. By using ethanol aqueous solution as the extraction medium and combining the synergistic effect of ultrasonic treatment and complex enzymatic hydrolysis, the plant cell structure of willow branch can be efficiently destroyed and the oil components can be fully released. The cavitation effect generated by ultrasonic treatment can effectively break the cell wall, and the cellulase, pectinase and protease in the complex enzyme system can specifically degrade different components of the plant cell wall, further promoting the release of oil. This multi-technology combined extraction method can significantly improve the extraction rate of willow branch oil compared with the traditional water vapor distillation method, and effectively avoid the destruction of heat-sensitive active ingredients due to the lower operating temperature, better preserving the natural flavor and biological activity of willow branch oil.

[0019] (2) The present process innovatively uses a specially designed cobalt ferrite-deep eutectic solvent-biochar magnetic composite material in the purification stage, realizing efficient and green selective purification. The composite material combines the selective adsorption ability of deep eutectic solvent for polar impurities, the high specific surface area characteristics of biochar material, and the magnetic separation advantages of cobalt ferrite, which can accurately remove phenolic impurities in willow branch oil while maximizing the retention of effective ingredients. Especially worth mentioning is that by using a weakly alkaline sodium bicarbonate-ethanol-water mixed solution as an eluent, it can effectively desorb the adsorbed impurities and protect the structural stability of the deep eutectic solvent, ensuring the reusability of the composite material. This purification method has the advantages of high selectivity, simple operation, and environmental friendliness compared with traditional refining methods, and can be quickly separated by an external magnetic field, greatly improving the process efficiency.

[0020] (3) The present process realizes the organic combination of green environmental protection and resource recycling. The ethanol aqueous solution used in the entire process can be recycled, significantly reducing solvent consumption and environmental pollution. It is particularly worth emphasizing that the biochar used to prepare the composite material is derived from the excess sludge of a sewage treatment plant, realizing the resource utilization of waste and conforming to the concept of circular economy. The entire process from raw material treatment to final product refining forms a complete, efficient and environmentally friendly technical system, not only providing a new solution for the high-quality extraction of willow branch oil, but also providing a beneficial technical reference for the efficient extraction and purification of other plant essential oils, and has important application value. DETAILED DESCRIPTION

[0021] For the purpose of understanding the present application, the present application is illustrated by the following examples. It should be apparent to those skilled in the art that the examples are merely for the purpose of understanding the present application and should not be regarded as specific limitations to the present application.

[0022] Example 1

[0023] The present embodiment provides a process for extracting willow oil, comprising the following steps: Preparation of cobalt ferrite-eutectic solvent-biochar magnetic composite: Step A1, accurately weigh 10.0 g of cobalt nitrate hexahydrate and 28.0 g of iron nitrate nonahydrate, dissolve in 500 mL of deionized water, and dissolve for 30 minutes under magnetic stirring at 300 rpm. Then, under continuous stirring, slowly add 2 mol / L aqueous sodium hydroxide solution to adjust the pH of the mixed solution to 11.5. The resulting homogeneous suspension is transferred to a 100 mL polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle with a filling degree of 80%. After sealing the reaction kettle, it is placed in a forced air drying oven at 200℃ for 12 hours. After the reaction is completed, the reaction kettle is allowed to cool to room temperature naturally. The precipitate is separated under the action of an external 0.5T neodymium-iron-boron permanent magnet, and the supernatant is discarded. The precipitate is washed three times with 100 mL of anhydrous ethanol and 100 mL of deionized water, each time after washing under an external magnetic field. The washed product is transferred to a vacuum drying oven and dried at 80℃ for 12 hours to obtain black cobalt ferrite nanopowder, which is ground and reserved for use.

[0024] Step A2, take 100 g of residual sludge from a sewage treatment plant (dry basis), spread it on a ceramic evaporating dish, and place it in a 105℃ electric heating air drying oven for 24 hours until the weight is constant. The dried sludge block is broken with a mortar and passed through a 100 mesh standard sieve to obtain a dried sludge powder. Weigh 20 g of the dried sludge powder and mix it with 100 mL of a 25% mass fraction aqueous iron chloride hexahydrate solution in a 250 mL beaker, and immerse it at room temperature for 12 hours. Transfer the immersed mixture to an alumina ceramic boat and place it in the constant temperature zone of a tube furnace. Purge with high-purity nitrogen gas (flow rate 200 mL / min) for 30 minutes to remove air, then under nitrogen protection, increase the temperature to 600℃ at a rate of 10℃ / min, and pyrolyze at this temperature for 3 hours. After the pyrolysis is completed, it is naturally cooled to room temperature. Remove the product and wash it repeatedly with deionized water until the washing liquid is neutral (pH≈7), then dry it in an 80℃ oven for 12 hours to obtain a magnetic sludge-based biochar, which is stored in a desiccator.

[0025] Step A3, accurately weigh betaine 10.0 g, glycolic acid 6.1 g and ethylene glycol 4.7 g, and place them in a 100 mL round-bottom flask. Place the flask in an 80 °C oil bath and react for 2 hours under 400 rpm magnetic stirring until a homogeneous, transparent liquid is formed, i.e. a deep eutectic solvent is obtained, which is stored in a closed container for later use.

[0026] Step A4, weigh 10.0 g of magnetic sludge-based biochar prepared in step A2, and disperse it in 100 mL of deep eutectic solvent prepared in step A3. Then add 1.0 g of epichlorohydrin as a crosslinking agent, and ultrasonically disperse it in an ultrasonic cleaner at 500 W and 40 kHz for 45 minutes. Next, add 2.0 g of cobalt ferrite nanopowder prepared in step A1. Transfer the mixed system to a 250 mL three-necked round-bottom flask, and react for 7 hours under 80 °C oil bath and 600 rpm mechanical stirring. After the reaction is completed, separate the product by using a 0.5 T external magnetic field, and wash it with 100 mL of anhydrous ethanol three times to remove unreacted substances. Dry the final product in a 80 °C vacuum drying oven for 12 hours to obtain the final cobalt ferrite-deep eutectic solvent-biochar magnetic composite, which is ground and sieved through a 200 mesh sieve, and stored in a desiccator for later use.

[0027] Extraction of wattle oil: Step S1, collect 100 g of fresh wattle leaves, flowers and branches, and obtain about 35 g of wattle raw material. Use a traditional Chinese medicine grinder to crush the dried raw material, and sieve it through an 80 mesh standard sieve to obtain wattle powder. Weigh 30.0 g of wattle powder, and place it in a 1 L three-necked flask with stirring, and add 500 mL of 70% ethanol aqueous solution. Then add 0.5 g of L-ascorbic acid. Place the flask in a 50 °C constant temperature water bath, and react for 3 hours under 300 rpm stirring. At the same time, place the flask in an ultrasonic cleaner at 400 W and 40 kHz for ultrasonic treatment for 45 minutes. After the reaction is completed, adjust the pH of the mixture to 5.0 using 1 mol / L dilute hydrochloric acid solution. Then, add a complex enzyme preparation, including 0.5 g of cellulase (activity ≥ 10,000 U / g), 0.5 g of pectinase (activity ≥ 3,000 U / g) and 0.5 g of protease (activity ≥ 200,000 U / g). Enzymatically hydrolyze for 2.5 hours under a 52 °C constant temperature water bath and 200 rpm stirring. After the enzymatic hydrolysis is completed, heat the hydrolyzed mixture to 85 °C and keep it for 20 minutes for enzyme inactivation treatment. Transfer the mixture to a high-pressure homogenizer, and perform cyclic homogenization treatment 5 times under 50 MPa pressure. Filter the homogenized slurry with a 200 mesh nylon filter cloth, and collect the filtrate, i.e. wattle oil water phase slurry is obtained.

[0028] Step S2, transfer all the willow oil aqueous phase slurry obtained in step S1 to a 2L glass reactor. Add 10.0 g of the prepared cobalt ferrite-eutectic solvent-biochar magnetic composite material to the reactor. Place the reactor in a 40°C constant temperature water bath, and adsorb for 100 minutes at a stirring speed of 300 rpm. After adsorption is complete, stop stirring and stand for 30 minutes.

[0029] Step S3, apply a strong magnetic field of 0.5T outside the reactor, stand for 10 minutes, and let the magnetic composite material settle completely. Collect the willow oil-rich liquid phase for standby use. Wash the settled composite material twice with 100 mL of deionized water to remove the oil phase attached to the surface. Transfer all the washed composite material to a 500 mL elution bottle. Add 200 mL of eluent (consisting of 0.1 mol / L sodium bicarbonate, 60% volume fraction of ethanol aqueous solution, and pH adjusted to 8.0 with sodium hydroxide solution) to the bottle. Place the elution bottle in a 35°C constant temperature water bath, and elute for 30 minutes with stirring at 200 rpm. After elution is complete, apply a magnetic field of 0.5T to the bottom of the bottle again, stand for 5 minutes, and discard the impurity-containing eluent. The regenerated composite material can be recycled for use.

[0030] Step S4, concentrate the willow oil-rich liquid phase collected in step S3 using a rotary evaporator (vacuum degree -0.09 MPa) under a 40°C water bath condition to recover ethanol and obtain crude willow oil. Dissolve the crude willow oil with a small amount of n-hexane, and load it onto a glass chromatography column (column diameter 3 cm) filled with 100 g of 200-300 mesh silica gel. Use a gradient eluent of n-hexane and ethyl acetate mixed at a volume ratio of 4:1 to elute, and collect the target fractions. Combine the target fractions, and rotary evaporate again under a 40°C water bath condition at a vacuum degree of -0.09 MPa to remove the organic solvent. Mix the obtained refined willow oil with 10.0 g of anhydrous sodium sulfate, stir, filter, and perform nitrogen blowing (flow rate 50 mL / min) to remove trace amounts of solvent and moisture, and finally obtain the refined willow oil product.

[0031] Example 2

[0032] This example provides a willow oil extraction process, comprising the following steps: Preparation of cobalt ferrite-eutectic solvent-biochar magnetic composite material: Step Al, accurately weigh cobalt nitrate hexahydrate 10.0 g and iron nitrate nonahydrate 28.0 g, dissolve in 500 mL of deionized water under magnetic stirring at 300 rpm for 30 min. Then, slowly add 2 mol / L aqueous sodium hydroxide solution dropwise under continuous stirring to adjust the pH of the mixed solution to 11.0. Transfer the resulting homogeneous suspension into a 100 mL polytetrafluoroethylene-lined stainless steel autoclave with 80% filling degree. Seal the autoclave and place it in a forced air drying oven at 195 °C for 14 h. After the reaction, allow the autoclave to cool down to room temperature (about 25 °C) naturally. Separate the precipitate under an external 0.5 T neodymium-iron-boron permanent magnet field and discard the supernatant. Wash the precipitate with 100 mL of absolute ethanol and 100 mL of deionized water alternately for three times, each time followed by separation under an external magnetic field. Transfer the washed product into a vacuum drying oven and dry at 75 °C for 14 h to obtain black cobalt ferrite nanopowder, which is ready for use after grinding.

[0033] Step A2, take 100 g of residual sludge from a wastewater treatment plant (dry basis), spread it on a ceramic evaporating dish and place it in a 104 °C electric heating forced air drying oven for 26 h until constant weight. Crush the dried sludge block with a mortar and pass it through a 100 mesh standard sieve to obtain dried sludge powder. Accurately weigh 20 g of dried sludge powder and mix it with 100 mL of 25% mass fraction aqueous iron chloride hexahydrate solution in a 250 mL beaker, and immerse it at room temperature for 14 h. Transfer the immersed mixture into an alumina ceramic boat and place it in the constant temperature zone of a tube furnace. Introduce high-purity nitrogen gas (flow rate 200 mL / min) for 30 min to remove air, then heat it to 595 °C at a heating rate of 10 °C / min under nitrogen protection, and pyrolyze it at this temperature for 4 h. After pyrolysis, cool it to room temperature naturally. Take out the product, wash it repeatedly with deionized water until the washing liquid is neutral (pH ~ 7), then dry it in a 75 °C oven for 14 h to obtain magnetic sludge-based biochar, which is stored in a desiccator.

[0034] Step A3, accurately weigh betaine 10.0 g, glycolic acid 6.1 g and ethylene glycol 4.7 g, and place them in a 100 mL round-bottom flask. Place the flask in a 78 °C oil bath and react under magnetic stirring at 400 rpm for 2.5 h until a homogeneous, transparent liquid is formed, i.e. Bet-GA-EG deep eutectic solvent is obtained, which is stored in a closed container for later use.

[0035] Step A4, 10.0 g of magnetic sludge-based biochar prepared in step A2 was dispersed in 100 mL of deep eutectic solvent prepared in step A3. Then, 0.5 g of epichlorohydrin was added as a crosslinking agent, and ultrasonic dispersion was performed in an ultrasonic cleaner at 400 W and 40 kHz for 60 min. Next, 1.0 g of cobalt ferrite nanopowder prepared in step Al was added. The mixed system was transferred to a 250 mL three-necked round-bottom flask, and reaction was performed at 78 °C in an oil bath with 500 rpm mechanical stirring for 8 h. After the reaction was completed, the product was separated by using a 0.5 T external magnetic field, and washed with 100 mL of absolute ethanol three times to remove unreacted substances. The final product was dried in a vacuum drying oven at 75 °C for 14 h to obtain the final cobalt ferrite-deep eutectic solvent-biochar magnetic composite, which was ground and passed through a 200 mesh sieve and stored in a desiccator for use.

[0036] Extraction of Vitex oil: Step S1, 100 g of fresh Vitex leaves, flowers, and branches were collected to obtain about 35 g of Vitex raw material. The dried raw material was crushed using a traditional Chinese medicine crusher and passed through a 80 mesh standard sieve to obtain Vitex powder. 30.0 g of Vitex powder was weighed and placed in a 1 L three-necked flask with stirring, and 500 mL of 65% ethanol aqueous solution was added. Then, 0.3 g of L-ascorbic acid was added. The flask was placed in a 48 °C constant temperature water bath and reacted for 4 h with 300 rpm stirring. At the same time, the flask was placed in a 300 W, 40 kHz ultrasonic cleaner for ultrasonic treatment for 60 min. After the reaction was completed, the pH of the mixture was adjusted to 4.5 using 1 mol / L dilute hydrochloric acid solution. Then, a complex enzyme preparation was added, including 0.5 g of cellulase (activity ≥ 10,000 U / g), 0.5 g of pectinase (activity ≥ 3,000 U / g), and 0.5 g of protease (activity ≥ 200,000 U / g). Enzymatic hydrolysis was performed at 50 °C in a constant temperature water bath with 200 rpm stirring for 3 h. After the enzymatic hydrolysis was completed, the enzymatic hydrolysis mixture was heated to 80 °C and maintained for 30 min for enzyme inactivation treatment, and the mixture was transferred to a high-pressure homogenizer and treated with 50 MPa pressure for 5 cycles. The homogenized slurry was filtered with a 200 mesh nylon filter cloth, and the filtrate was collected to obtain the Vitex oil water phase slurry.

[0037] Step S2, all of the Vitex oil water phase slurry obtained in step S1 was transferred to a 2 L glass reactor. 8.0 g of the prepared cobalt ferrite-deep eutectic solvent-biochar magnetic composite was added to the reactor. The reactor was placed in a 38 °C constant temperature water bath, and adsorption was performed at a stirring speed of 300 rpm for 120 min. After the adsorption was completed, the stirring was stopped, and the system was allowed to stand for 30 min.

[0038] Step S3, a strong magnetic field of 0.4T was applied outside the reactor, and the magnetic composite material was allowed to settle for 10 minutes to ensure complete sedimentation. The liquid phase rich in wattle oil was collected for later use. The settled composite material was washed twice with 80 mL of deionized water to remove the oil phase attached to the surface. The washed composite material was transferred to a 500 mL elution bottle. 150 mL of eluent (consisting of 0.1 mol / L sodium bicarbonate, 60% ethanol aqueous solution, pH adjusted to 7.5 with sodium hydroxide solution) was added to the bottle. The elution bottle was placed in a 34°C constant temperature water bath and stirred at 200 rpm for 30 minutes for elution. After elution, the magnetic field of 0.4T was applied again at the bottom of the bottle, and after 5 minutes of standing, the eluent containing impurities was discarded, and the regenerated composite material could be recycled.

[0039] Step S4, the liquid phase rich in wattle oil collected in step S3 was concentrated using a rotary evaporator (vacuum degree -0.09 MPa) under the condition of a 38°C water bath, and ethanol was recovered to obtain crude wattle oil. The crude wattle oil was dissolved in a small amount of n-hexane and loaded onto a glass chromatography column (column diameter 3 cm) containing 100 g of 200-300 mesh silica gel. Gradient elution was performed using an eluent of n-hexane and ethyl acetate in a volume ratio of 4:1, and the target fractions were collected. The target fractions were combined and rotary evaporated again under the condition of a 38°C water bath and a vacuum degree of -0.09 MPa to remove the organic solvent. The refined wattle oil obtained was mixed with 10.0 g of anhydrous sodium sulfate, stirred and filtered, and purged with nitrogen gas (flow rate 50 mL / min) to remove trace amounts of solvent and moisture, finally obtaining the refined wattle oil product.

[0040] Example 3

[0041] This example provides a wattle oil extraction process, comprising the following steps: Preparation of cobalt ferrite-eutectic solvent-biochar magnetic composite material: Step Al, accurately weigh cobalt nitrate hexahydrate 10.0 g and iron nitrate nonahydrate 28.0 g, dissolve in 500 mL of deionized water, and dissolve for 30 minutes under magnetic stirring at 300 rpm. Then, under continuous stirring, slowly add 2 mol / L aqueous sodium hydroxide solution to adjust the pH of the mixed solution to 12.0. Transfer the resulting homogeneous suspension to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave with a filling degree of 80%. After sealing the reactor, place it in a forced air drying oven at 205 °C for 10 hours. After the reaction is completed, allow the reactor to cool naturally to room temperature (about 25 °C). Separate the precipitate under the action of an external 0.5 T neodymium-iron-boron permanent magnet and discard the supernatant. Wash the precipitate with 100 mL of anhydrous ethanol and 100 mL of deionized water alternately three times, each time after washing under an external magnetic field. Transfer the washed product to a vacuum drying oven and dry at 85 °C for 10 hours to obtain black cobalt ferrite nanopowder, which is ground and stored for later use.

[0042] Step A2, take 100 g of residual sludge from a sewage treatment plant (dry basis), and place it in a ceramic evaporating dish. Dry it in a 106 °C electric heating air drying oven for 22 hours until the weight is constant. Crush the dried sludge block with a mortar and pass it through a 100 mesh standard sieve to obtain dried sludge powder. Weigh 20 g of dried sludge powder and mix it with 100 mL of a 25% mass fraction aqueous iron chloride hexahydrate solution in a 250 mL beaker. Soak at room temperature for 10 hours. Transfer the soaked mixture to an alumina ceramic boat and place it in the constant temperature zone of a tube furnace. Introduce high-purity nitrogen gas (flow rate 200 mL / min) for 30 minutes to remove air, then under nitrogen protection, increase the temperature to 605 °C at a rate of 10 °C / min, and pyrolyze at this temperature for 2 hours. After pyrolysis is complete, cool naturally to room temperature. Remove the product and wash repeatedly with deionized water until the washing liquid is neutral (pH ≈ 7), then dry in an 85 °C oven for 10 hours to obtain magnetic sludge-based biochar, which is stored in a desiccator.

[0043] Step A3, accurately weigh betaine 10.0 g, glycolic acid 6.1 g, and ethylene glycol 4.7 g, and place them in a 100 mL round-bottom flask. Place the flask in an 82 °C oil bath and react under magnetic stirring at 400 rpm for 1.5 hours until a homogeneous, transparent liquid is formed, i.e. Bet-GA-EG deep eutectic solvent is obtained, which is stored in a sealed container for later use.

[0044] Step A4, 10.0 g of magnetic sludge-based biochar prepared in step A2 was dispersed in 100 mL of deep eutectic solvent prepared in step A3. Then, 1.0 g of epichlorohydrin was added as a crosslinking agent, and ultrasonic dispersion was performed in an ultrasonic cleaner at 600 W and 40 kHz for 30 min. Next, 3.0 g of cobalt ferrite nanopowder prepared in step A1 was added. The mixed system was transferred to a 250 mL three-necked round-bottom flask, and reacted at 82 °C in an oil bath under mechanical stirring at 700 rpm for 6 h. After the reaction was completed, the product was separated by using a 0.5 T external magnetic field, and washed with 100 mL of anhydrous ethanol three times to remove unreacted substances. The final product was dried in a vacuum drying oven at 85 °C for 10 h to obtain the final cobalt ferrite-deep eutectic solvent-biochar magnetic composite, which was ground and sieved through a 200 mesh sieve, and stored in a desiccator for use.

[0045] Extraction of Vitex oil: Step S1, 100 g of fresh Vitex leaves, flowers, and branches were collected to obtain about 35 g of Vitex raw material. The dried raw material was crushed using a traditional Chinese medicine crusher and sieved through an 80-mesh standard sieve to obtain Vitex powder. 30.0 g of Vitex powder was weighed and placed in a 1 L three-necked flask with stirring, and 500 mL of 75% ethanol aqueous solution was added. Then, 0.7 g of L-ascorbic acid was added. The flask was placed in a 52 °C constant temperature water bath and reacted for 2 h under stirring at 300 rpm. At the same time, the flask was placed in an ultrasonic cleaner at 500 W and 40 kHz for ultrasonic treatment for 30 min. After the reaction was completed, the pH of the mixture was adjusted to 5.5 using 1 mol / L dilute hydrochloric acid solution. Then, a complex enzyme preparation was added, including 0.83 g of cellulase (activity ≥ 10,000 U / g), 0.83 g of pectinase (activity ≥ 3,000 U / g), and 0.83 g of protease (activity ≥ 200,000 U / g). Enzymatic hydrolysis was carried out at 55 °C in a constant temperature water bath under stirring at 200 rpm for 2 h. After the enzymatic hydrolysis was completed, the enzymatic hydrolysis mixture was heated to 85 °C and maintained for 15 min for enzyme inactivation treatment. The mixture was transferred to a high-pressure homogenizer and subjected to cyclic homogenization treatment at 50 MPa for 5 times. The homogenized slurry was filtered using a 200-mesh nylon filter cloth, and the filtrate was collected to obtain the Vitex oil water-phase slurry.

[0046] Step S2, all of the Vitex oil water-phase slurry obtained in step S1 was transferred to a 2 L glass reactor. 12.0 g of the prepared cobalt ferrite-deep eutectic solvent-biochar magnetic composite was added to the reactor. The reactor was placed in a 42 °C constant temperature water bath, and adsorption was carried out at a stirring speed of 300 rpm for 90 min. After the adsorption was completed, the stirring was stopped, and the system was allowed to stand for 30 min.

[0047] Step S3, a strong magnetic field of 0.6 T was applied outside the reactor, and the mixture was allowed to stand for 10 minutes to ensure complete settling of the magnetic composite. The liquid phase rich in wattle oil was collected for later use. The settled composite was washed twice with 120 mL of deionized water to remove the oil phase adhering to the surface. The washed composite was transferred to a 500 mL elution bottle. 250 mL of eluent (consisting of 0.1 mol / L sodium bicarbonate, 60% (v / v) aqueous ethanol solution, pH adjusted to 8.5 with sodium hydroxide solution) was added to the bottle. The elution bottle was placed in a 36 °C constant temperature water bath and stirred at 200 rpm for 30 minutes for elution. After elution was complete, a magnetic field of 0.6 T was again applied to the bottom of the bottle, and after standing for 5 minutes, the eluent containing impurities was discarded, and the regenerated composite could be recycled.

[0048] Step S4, the liquid phase rich in wattle oil collected in step S3 was concentrated using a rotary evaporator (vacuum degree -0.09 MPa) under the condition of a 42 °C water bath, and ethanol was recovered to obtain crude wattle oil. The crude wattle oil was dissolved in a small amount of n-hexane and loaded onto a glass chromatography column (column diameter 3 cm) packed with 100 g of 200-300 mesh silica gel. Gradient elution was performed using an eluent consisting of n-hexane and ethyl acetate in a volume ratio of 4:1, and the target fractions were collected. The target fractions were combined and rotary evaporated again under the condition of a 42 °C water bath and a vacuum degree of -0.09 MPa to remove the organic solvent. The refined wattle oil obtained was mixed with 10.0 g of anhydrous sodium sulfate, stirred, filtered, and purged with nitrogen gas (flow rate 50 mL / min) to remove trace amounts of solvent and moisture, and finally the refined wattle oil product was obtained.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is in the extraction of wattle oil: Step S1, same as Example 1. Step S2, the step of adding cobalt ferrite-deep eutectic solvent-biochar magnetic composite was omitted, and the wattle oil aqueous phase slurry was directly subjected to subsequent treatment. Step S3, the slurry of step S2 was centrifuged at a speed of 8000 rpm for 20 minutes, and the supernatant oil phase was collected. Step S4, the collected supernatant oil phase was rotary evaporated at 40 °C, and the subsequent refining steps were the same as Example 1.

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that the preparation of the cobalt ferrite-biochar magnetic composite material: only steps A1 and A2 are performed to prepare cobalt ferrite nanopowder and magnetic sludge-based biochar. Steps A3 and A4 are omitted, and no deep eutectic solvent is prepared and loaded. 10.0 g of magnetic sludge-based biochar is treated with 2.0 g of cobalt ferrite nanopowder under 400 W ultrasonic conditions for 45 minutes, and then mixed under stirring at 80°C for 2 hours to obtain an unfunctionalized magnetic composite material. Extraction of wattle oil: Step S1, same as Example 1. Step S2, add 10.0 g of unfunctionalized cobalt ferrite-biochar magnetic composite material, and other conditions are the same as Example 1. Step S3, same as Example 1. Step S4, same as Example 1.

[0051] Comparative Example 3 The difference between this comparative example and Example 1 is that the extraction of wattle oil: Step S1, take 100 g of wattle raw material, crush and mix with 500 mL of 70% ethanol aqueous solution, and add 0.5 g of ascorbic acid. The mixture is stirred at 50°C for 3 hours while being treated with 400 W ultrasonic waves for 45 minutes. No enzymatic treatment is performed, and high-pressure homogenization is performed directly. Steps S2 to S4 are the same as Example 1.

[0052] The extraction process of wattle oil provided in the above examples and comparative examples is tested according to the test specifications of national and industry standards, and the test methods are as follows: Determination of wattle oil extraction rate: accurately weigh the mass of the refined wattle oil product obtained in each example and comparative example, use an analytical balance with a precision of 0.0001 g for weighing, and record the mass in g. The extraction rate is calculated by the following formula: extraction rate = (mass of refined wattle oil / mass of dried wattle raw material) x 100%. The mass of dried wattle raw material is calculated based on the 35.0 g obtained in Example 1 as the unified benchmark, and the same batch of raw material is used in all comparative tests to ensure the comparability of the results.

[0053] Evaluation of sensory and physical indicators of wattle oil: professional sensory evaluation method is used to evaluate the odor characteristics by nose smelling method. The yellow value and red value of the oil sample are determined using a Lovibond colorimeter with a 1-inch color cell in a standard light source box. The acid value determination method is as follows: accurately weigh 3.00 g of oil sample, dissolve in 50 mL of mixed solvent of diethyl ether and ethanol (volume ratio 1:1), use phenolphthalein as indicator, and titrate with 0.1 mol / L potassium hydroxide standard solution until pink color and no fading within 30 seconds as the end point. The acid value is expressed as the number of milligrams of potassium hydroxide consumed per gram of oil sample, with units of mg / g.

[0054] Vitex oil main component analysis: gas chromatography-mass spectrometry was used for analysis. Chromatographic conditions: DB-5MS capillary column was used, specification 30 m x 0.25 mm x 0.25 μm; the inlet temperature was 250 DEG C; the temperature rising program was that the initial temperature was 50 DEG C and maintained for 2 min, and then increased to 250 DEG C at a rate of 5 DEG C / min, and maintained for 10 min; the carrier gas was high-purity helium, and the flow rate was 1.0 mL / min; the sample injection amount was 1.0 μL, and the split ratio was 10:1. Mass spectrometry conditions: electron impact ion source was used, the ion source temperature was 230 DEG C; the electron energy was 70 eV; the mass scan range was m / z 35-500. Compound qualitative analysis was carried out by comparing NIST standard spectral library, and the relative percentage content of each component was calculated by using area normalization method, and the total content of main active ingredients such as β-eudesmol and eucalyptol was analyzed.

[0055] Composite material adsorption performance evaluation: the adsorption performance of the composite material was evaluated by determining the decolorization rate. Using a spectrophotometer, the absorbance values of the water phase slurry of the Vitex oil before and after being treated by the composite material in each example and the comparative example were determined at a wavelength of 420 nm with deionized water as a reference. Before determination, all samples were centrifuged at a speed of 5000 rpm for 10 min, and the supernatant was taken for determination. The decolorization rate calculation formula was: decolorization rate = (1-A1 / A0) x 100%, wherein A0 was the absorbance of the slurry before treatment, and A1 was the absorbance of the supernatant after treatment. The decolorization rate can be used as an evaluation index of the adsorption efficiency of the composite material on pigments and other impurities.

[0056] Vitex oil antioxidant activity determination: DPPH free radical scavenging method was used for determination. 0.0200 g of Vitex oil sample was accurately weighed, dissolved with anhydrous ethanol and diluted to 10.0 mL. 2.00 mL of sample solution was taken, 2.00 mL of DPPH ethanol solution with a concentration of 0.1 mmol / L was added, and after mixing, it was reacted at room temperature for 30 min under dark conditions. The absorbance value As was determined at a wavelength of 517 nm. At the same time, the absorbance value Aj of 2.00 mL of sample solution mixed with 2.00 mL of anhydrous ethanol, and the absorbance value Ac of 2.00 mL of anhydrous ethanol mixed with 2.00 mL of DPPH solution were determined. The DPPH free radical scavenging rate calculation formula was: scavenging rate = [1-(As-Aj) / Ac] x 100%. All absorbance determinations were carried out under the same conditions for three parallel experiments, and the average value was taken.

[0057] The above performance test data is shown in Table 1.

[0058] Table 1 Performance test results

[0059] From the above content, it can be known that compared with the comparative examples 1-3, the examples 1-3 of the present application effectively solve the multiple technical bottlenecks existing in the Vitex oil extraction process for a long time.

[0060] Firstly, in terms of extraction efficiency, the extraction rate of willow oil in Examples 1-3 is 0.25-0.3%, which is significantly higher than 0.15% of Comparative Example 1 and 0.17% of Comparative Example 3, which fully proves the high efficiency of ultrasonic synergistic complex enzymatic hydrolysis technology in destroying plant cell wall, and solves the problem of low oil yield in traditional water extraction or single extraction technology.

[0061] Secondly, in terms of product purity and quality, the acid value of willow oil obtained in Examples 1-3 is less than 0.9 mg / g, and the Lovibond yellow value is less than 0.5Y, which is much better than each comparative example, especially Comparative Example 1 which does not use composite material purification, the acid value is as high as 2.15 mg / g, and the yellow value is 5.0Y, which shows that the unique cobalt-iron oxide-eutectic solvent-biochar magnetic composite material can efficiently and selectively adsorb free fatty acids, pigments and other polar impurities, and solve the technical problems of low product purity and deep color in traditional process.

[0062] Furthermore, in terms of functional component retention and product value, the total content of main active ingredients in Examples 1-3 is more than 90%, while the total content of main active ingredients in Comparative Example 1 is only 85.2%, and the total content of main active ingredients in Comparative Example 2 is 88.6% without using deep eutectic solvent functionalization, which proves that the selective adsorption of deep eutectic solvent can better retain the effective components in willow oil while removing impurities.

[0063] In addition, the DPPH free radical scavenging rate of Examples 1-3 is more than 87%, which shows better antioxidant activity, further proving the high quality of the product.

[0064] Finally, the impurity removal rate of Comparative Example 2 is only 70.3%, which is significantly lower than the impurity removal rate of Examples which is more than 93.8%, which highlights the key adsorption role of deep eutectic solvent in the composite material; and the lower yield of Comparative Example 3 proves the necessity of the enzymatic hydrolysis step for the full release of oil.

[0065] In summary, by integrating ultrasonic, enzymatic hydrolysis, magnetic composite material adsorption and other key technologies, the present application solves a series of technical problems in willow oil extraction, such as low extraction rate, high impurity content in product, easy loss of effective components, and complicated process, and realizes efficient, high-quality and green comprehensive extraction effect.

Claims

1. A process for extracting Vitex negundo oil, characterized in that, Includes the following steps: S1. Crush the leaves, flowers, and branches of Vitex negundo to obtain Vitex negundo raw material. Mix the Vitex negundo raw material with an ethanol-water solution, add ascorbic acid, and obtain a mixture. Stir the mixture at 48-52℃, and then perform ultrasonic treatment. Subsequently, adjust the pH of the mixture to 4.5-5.5, add cellulase, pectinase, and protease, and enzymatically hydrolyze at 50-55℃ to obtain an enzymatically hydrolyzed mixture. Heat the enzymatically hydrolyzed mixture to 80-85℃ for enzyme inactivation treatment. Then, process it through a high-pressure homogenizer to obtain Vitex negundo oil-water slurry. Filter the Vitex negundo oil-water slurry through a sieve to obtain a Vitex negundo oil-water phase slurry. S2. Place the Vitex trifolia oil-water slurry in a reactor, add the cobalt ferrite-deep eutectic solvent-biochar magnetic composite material, and stir at 38-42℃; let stand. S3. Apply a magnetic field to the outside of the reactor and collect the liquid phase; wash the cobalt ferrite-deep eutectic solvent-biochar magnetic composite material with deionized water, transfer the washed cobalt ferrite-deep eutectic solvent-biochar magnetic composite material to the elution vessel, add a sodium bicarbonate-ethanol-water mixed solution with a pH of 7.5-8.5, and stir at 34-36℃. After elution, a magnetic field is applied again, the eluent containing impurities is discarded, and the regenerated composite material can be recycled. S4. The collected liquid phase is rotary evaporated at 38-42℃ under reduced pressure to obtain crude Vitex negundo oil. The crude Vitex negundo oil is purified by passing it through a silica gel chromatography column to obtain purified Vitex negundo oil. The purified Vitex negundo oil is mixed with anhydrous sodium sulfate, stirred, filtered, and purged with nitrogen.

2. The extraction process of Vitex negundo oil according to claim 1, characterized in that, In step S1, the mixture is stirred at 48-52℃ for 2-4 hours.

3. The extraction process of Vitex negundo oil according to claim 1, characterized in that, In step S2, the stirring time is 90-120 min at 38-42℃.

4. The extraction process of Vitex negundo oil according to claim 1, characterized in that, In step S3, a magnetic field with an intensity of 0.4-0.6T is applied to the outside of the reactor.

5. The extraction process of Vitex negundo oil according to claim 1, characterized in that, In step S4, the eluent for the silica gel-filled chromatography column is a mixed solution of n-hexane and ethyl acetate.

6. The extraction process of Vitex negundo oil according to any one of claims 1-5, characterized in that, The preparation steps of the cobalt ferrite-deep eutectic solvent-biochar magnetic composite material include: A1. Dissolve cobalt nitrate hexahydrate and ferric nitrate nonahydrate in deionized water and stir; adjust the pH to 11-12 to obtain a mixed solution; transfer the mixed solution to a high-pressure reactor and react at 195-205℃; after the reaction is completed, allow it to cool naturally to room temperature, separate the precipitate using an external magnetic field, wash it alternately with anhydrous ethanol and deionized water, and finally dry it in a vacuum drying oven at 75-85℃ to obtain cobalt ferrite nanopowder; A2. The sludge is dried at 104-106℃, crushed and sieved to obtain dried sludge powder; the dried sludge powder is mixed with an aqueous solution of ferric chloride and impregnated to obtain an impregnated mixture; the impregnated mixture is pyrolyzed in a tube furnace at 595-605℃ under nitrogen protection. After pyrolysis, it is naturally cooled to room temperature, washed with deionized water until neutral, and then dried at 75-85℃ to obtain magnetic sludge-based biochar. A3. Mix betaine with glycolic acid and ethylene glycol, and stir at 78-82℃ to obtain a deep eutectic solvent; A4. Magnetic sludge-based biochar is dispersed in a deep eutectic solvent, epichlorohydrin is added, and the mixture is ultrasonically dispersed. Cobalt ferrite nanopowder is then added, and the mixture is reacted under stirring at 78-82℃. After the reaction is completed, the product is separated using an external magnetic field, washed with anhydrous ethanol, and finally vacuum dried at 75-85℃.

7. The extraction process of Vitex negundo oil according to claim 6, characterized in that, In step A1, the mass ratio of cobalt nitrate hexahydrate to ferric nitrate nonahydrate is 1:2.

8.

8. The extraction process of Vitex negundo oil according to claim 6, characterized in that, In step A2, the pyrolysis time in a tubular furnace at 595-605℃ is 2-4 hours.

9. The extraction process of Vitex negundo oil according to claim 6, characterized in that, In step A3, the mass ratio of betaine, glycolic acid and ethylene glycol is 10.0:6.1:4.

7.

10. The extraction process of Vitex negundo oil according to claim 6, characterized in that, In step A4, the reaction time is 6-8 hours under stirring at 78-82℃.

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