Method for extracting wormwood essential oil by using nanometer ferroferric oxide assisted supercritical carbon dioxide

Abstract

The invention relates to a method for extracting wormwood essential oil through nanometer ferroferric oxide assisted supercritical carbon dioxide. According to the technical scheme, the method comprises the following steps of 1, wormwood pretreatment, wherein wormwood raw materials are treated for pretreatment; uniformly adhering the nano particles to the surface of the wormwood powder according to the mass ratio of the wormwood powder to the nano ferroferric oxide of 15: 1; 2, performing supercritical carbon dioxide extraction on wormwood essential oil; the method has the beneficial effects that through the efficient wall breaking and magnetic response recovery characteristics of the nano ferroferric oxide, the extraction efficiency of specific active ingredients of the nano ferroferric oxide is greatly improved, and the industrialization value of wormwood is fully released; meanwhile, by means of the green and environment-friendly advantages of supercritical carbon dioxide and the reusability of nano materials, the problem of chemical adjuvant residues or high energy consumption is avoided, and the extraction process route of the special wormwood essential oil is enriched.

Description

Technical Field

[0001] This invention relates to the field of plant essential oil extraction, and in particular to a method for extracting Artemisia argyi essential oil using nano-iron oxide-assisted supercritical carbon dioxide. Background Technology

[0002] Artemisia argyi essential oil, a natural active ingredient extracted from the Artemisia argyi plant (a member of the Asteraceae family), is rich in terpenes, flavonoids, and phenolic compounds. It has irreplaceable application value in medicine (such as anti-inflammatory and analgesic), daily chemical products (such as mosquito repellent and skincare), and health and wellness (such as moxibustion therapy). Its extraction efficiency and quality directly determine the industrial added value of Artemisia argyi resources. Currently, the industrial extraction method for Artemisia argyi essential oil is dominated by supercritical carbon dioxide extraction. This technology, due to its advantages such as mild extraction temperature (typically 35-55℃), absence of organic solvent residue, and maximum preservation of the active ingredients in the essential oil, has become the preferred process for producing high-end Artemisia argyi essential oil.

[0003] The cell walls of Artemisia argyi leaves and stems are composed of cellulose, hemicellulose, and lignin, forming a dense network structure. The essential oil components within these cells are encapsulated in organelles such as thylakoids, making full release difficult through the osmosis of supercritical carbon dioxide. Traditional supercritical carbon dioxide extraction relies solely on the diffusion and osmosis of carbon dioxide molecules to disrupt the cell walls, lacking an active cell-wall breaking mechanism. This results in generally low essential oil extraction rates, with an industry average of only 1.8%-2.2%. A large amount of essential oil remains in the extraction residue, leading to resource waste. Furthermore, to improve extraction rates, some production processes optimize by extending extraction time (e.g., from 2 hours to 4 hours) or increasing extraction pressure (e.g., from 25 MPa to 35 MPa). However, this not only increases equipment energy consumption and production costs but may also cause degradation of heat-sensitive active components (such as thujone and α-thujol) in the essential oil due to prolonged high-temperature and high-pressure environments, affecting the quality of the essential oil.

[0004] To address the cell wall barrier problem, existing technologies have developed auxiliary extraction methods such as mechanical pulverization, enzymatic hydrolysis, and ultrasonic assistance, but all of these have significant limitations. While mechanical grinding can physically break down some cell walls, the particle size is difficult to control precisely (usually only reaching 40-60 mesh), easily leading to over-grinding and raw material agglomeration, which hinders carbon dioxide penetration. Furthermore, the localized high temperatures generated during grinding (reaching over 60°C) accelerate essential oil volatilization. Enzymatic hydrolysis requires the use of cellulase, hemicellulase, and other biological enzymes, which can specifically degrade cell wall components. However, the enzymatic hydrolysis reaction has stringent requirements for temperature (45-55°C) and pH (adjusted to 4.5-5.5), with a reaction cycle of 8-12 hours. Moreover, the enzyme preparations are expensive (accounting for approximately 15%-20% of the total extraction cost), making it difficult to scale up production. Ultrasonic-assisted methods use shock waves generated by cavitation to break down cell walls, but the penetration depth of ultrasound is limited (usually no more than 5cm). In large extraction vessels, this can lead to insufficient localized cell wall disruption but uneven overall results. Additionally, high-intensity ultrasound may cause oxidation of active ingredients in the essential oil, affecting product stability. Therefore, the industry urgently needs a new type of auxiliary extraction technology that can efficiently destroy the cell walls of Artemisia argyi and improve the essential oil extraction rate, while also taking into account ease of operation, cost control, and protection of essential oil quality.

[0005] Magnetic nanomaterials, with their unique nanoscale effects and magnetic response characteristics, have shown great application potential in the extraction of active ingredients from plants. Among them, nano-ferric oxide (Fe3O4) has become a highly anticipated auxiliary extraction material due to its mature preparation process, low cost, and good biocompatibility. Its nanoscale particle size (typically 20-100 nm) gives it a large specific surface area (up to 50-100 m² / g), allowing for sufficient contact with the cell walls of Artemisia argyi. Simultaneously, nano-ferric oxide particles possess a certain mechanical strength, which can disrupt the cell wall structure through physical collisions and adsorption, promoting the release of essential oils from within the cells. More importantly, nano-ferric oxide exhibits excellent magnetic responsiveness, enabling rapid separation and recovery under an external magnetic field, avoiding the problems of traditional auxiliary materials (such as diatomaceous earth and activated carbon) being difficult to separate from the extraction system and easily introducing impurities. Combining nano-ferric oxide with supercritical carbon dioxide extraction technology holds promise for constructing a new integrated system for extracting Artemisia argyi essential oil, encompassing "high-efficiency cell wall disruption, green extraction, and material recovery," providing a novel technological path to overcome existing technological bottlenecks.

[0006] However, research on the application of nano-ferric oxide in the extraction of Artemisia argyi essential oil is still in its infancy. How to optimize the preparation process of nano-ferric oxide (such as particle size control and surface modification) to adapt it to the supercritical carbon dioxide extraction environment (high pressure and low temperature), and achieve efficient mixing and synergistic cell wall disruption with Artemisia argyi raw materials, as well as how to design reasonable extraction process parameters (such as the proportion of nanomaterials added, extraction pressure, and temperature) to improve the extraction rate while ensuring the quality of essential oil, have become key technical problems that urgently need to be solved.

[0007] Based on this, the present invention proposes a method for supercritical carbon dioxide extraction of Artemisia argyi essential oil assisted by nano-ferric oxide. Summary of the Invention

[0008] The purpose of this invention is to address the aforementioned deficiencies in existing technologies by providing a method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide. This method aims to overcome the limitations of existing technologies through material design and process optimization, thereby achieving efficient, green, and large-scale extraction of Artemisia argyi essential oil.

[0009] The present invention discloses a method for supercritical carbon dioxide extraction of Artemisia argyi essential oil using nano-ferric oxide, the technical solution of which includes the following processes: I. Artemisia argyi pretreatment: Pretreatment of raw Artemisia argyi; Nano-Fe3O4 was placed in a vacuum drying oven and fed into a high-speed mixer in a mass ratio of 15:1 between Artemisia argyi powder and nano-Fe3O4, so that the nanoparticles were evenly attached to the surface of Artemisia argyi powder. II. Supercritical carbon dioxide extraction of Artemisia argyi essential oil; III. Recovery of nano-ferric oxide and purification of crude artemisia essential oil: Step 1: Transfer the crude mugwort essential oil, which has been de-CO2 removed, into a sealed adsorption tank with a stirring function. Stir to make the liquid uniform, insert an electric electromagnetic rod and completely immerse it, maintain a magnetic field strength of 0.3-0.5T for adsorption, turn off the stirring and let it stand, then remove the electromagnetic rod to complete the separation of nano-iron oxide from the essential oil. Step 2: Place the electromagnetic rod with adsorbed nano-iron oxide into anhydrous ethanol and ultrasonically clean it to remove the essential oil residue adhering to the surface. Step 3: Turn off the power to the electromagnetic rod. After the magnetic field is lost, the nano-iron oxide will fall off. Centrifuge to separate and collect the nanoparticles at the bottom. Step 4: Place the collected nano-Fe3O4 in a vacuum drying oven to restore its dispersibility and magnetic activity, and then reuse it for extraction. Step 5: Pass the essential oil liquid separated in Step 1 into a precision filter to trap waxy and plant solid particle impurities, and collect the clear essential oil liquid; Step Six: The clarified essential oil liquid is fed into a molecular distillation apparatus to separate trace impurities and highly active ingredients by the difference in boiling points. The distillate is then collected as high-purity Artemisia argyi essential oil. Step 7: Test the residual amount, purity, and active ingredient content of the purified essential oil in nano-ferric oxide. If it passes the test, store it in a brown sealed container in a cool, dry place.

[0010] Preferably, the supercritical carbon dioxide extraction of Artemisia argyi essential oil mentioned in this invention includes the following steps: Step 1: Open the turning drum (5) of the supercritical carbon dioxide instrument, add the pretreated mugwort into the turning drum (5), close the turning drum (5), turn on the motor (3), and let the spiral stirring paddle rotate. The pretreated mugwort begins to be disturbed under the action of the spiral blade (22). Step 2: Open the carbon dioxide gas tank (1), and the carbon dioxide gas reaches the high pressure pump (2) through the gas delivery pipe (12). Under the action of the high pressure pump (2), the gas pressure is raised to the supercritical pressure of 20MPa-30MPa, and the carbon dioxide gas becomes supercritical carbon dioxide gas. Step 3: Supercritical carbon dioxide gas reaches the uniform flow dispersion grid (4), and the gas quickly fills the fast air inlet section (19) at the bottom of the uniform flow dispersion grid (4). Then, under the action of the uniform flow grid section (18) at the top, the concentrated gas flow is dispersed, which plays a role in uniform flow and ensures that the gas can contact the Artemisia argyi raw material evenly, thereby improving the efficiency of the extraction and reaction process. Step 4: The gas passes through the uniform flow dispersion grid (4) and reaches the turning cylinder (5). The temperature inside the cylinder is raised by the external heating jacket. Under the action of the propeller blades (22), the pretreated Artemisia argyi raw material comes into full contact with supercritical carbon dioxide. In this process, the nano-sized iron tetroxide adsorbed on the pretreated Artemisia argyi raw material will assist the supercritical carbon dioxide gas in breaking the cell wall and improving the extraction rate of Artemisia argyi essential oil. Step 5: When the supercritical carbon dioxide gas reaches the top of the turning cylinder (5), it is blocked by the lower filter diversion cover (17) at the bottom of the impurity-blocking uniform flow screen (6), which further ensures the extraction efficiency of mugwort essential oil. At the same time, the lower filter diversion cover (17) also plays a filtering role on the essential oil and mugwort raw materials. Under the action of its internal mesh, the essential oil flows through evenly. Step 6: Artemisia essential oil reaches pressure reducing valve (7) through feed pipe (13). At this time, the pressure decreases, causing the supercritical carbon dioxide in the Artemisia essential oil to precipitate due to the pressure drop, thus playing a separation role. Step 7: The separated Artemisia argyi essential oil reaches the separation vessel (8) and flows into the collection tank (10) through the discharge valve (9) at its bottom. The separated carbon dioxide gas enters the booster pump (11) through the recovery gas pipe (14). Under the action of the booster pump (11), the recovered carbon dioxide gas is pumped back into the carbon dioxide gas tank (1) to realize the recovery and utilization of carbon dioxide gas.

[0011] Preferably, the supercritical carbon dioxide instrument mentioned in this invention includes a carbon dioxide tank (1), a high-pressure pump (2), a motor (3), a uniform flow dispersion grid (4), a turning cylinder (5), a filtration screen (6), a separation vessel (8), a collection tank (10), a booster pump (11), a gas supply pipe (12), a feed pipe (13), and a recovery gas pipe (14). The uniform flow dispersion grid (4) is installed on the lower side of the turning cylinder (5), and the motor (3) is installed on the lower part of the uniform flow dispersion grid (4). The filtration screen (6) is installed on the upper side of the turning cylinder (5). One end of the feed pipe (13) is connected to the filtration screen (6), and the other end is connected to the separation vessel (8). One side of the uniform flow dispersion grid (4) is connected to the carbon dioxide tank (1) through the gas supply pipe (12) and the high-pressure pump (2). The upper end of the carbon dioxide tank (1) is connected to the top of the separation vessel (8) through the recovery gas pipe (14) and the booster pump (11). The collection tank (10) is installed below the separation vessel (8).

[0012] Preferably, the uniform flow dispersion grid (4) mentioned in this invention is provided with a uniform flow grid (4.1) inside, and the upper and lower ends of the impurity blocking uniform flow screen (6) are respectively equipped with filter diversion screens; the output end of the motor (3) is connected to the stirring shaft (5.1) through the transmission shaft, and the propeller blades (5.2) are distributed outside the stirring shaft (5.1).

[0013] Preferably, the specific steps of the mugwort pretreatment mentioned in this invention are as follows: Step 1: Select fresh mugwort that is free from mold and pests, place it in a constant temperature forced-air drying oven, and dry it at 60℃ for 24 hours to reduce the moisture content of the mugwort to 8%-10%; then remove withered leaves, hard stem segments and mud impurities by vibrating screening machine, leaving only the leaves and tender stems. Step 2: First, use a jaw crusher to coarsely crush the mugwort into small pieces, then send it to a universal pulverizer for fine crushing; after crushing, sieve and collect the mugwort powder that is not sieved, and return the coarse material that is sieved to the universal pulverizer for secondary crushing; Step 3: Place the nano-ferric oxide in a vacuum drying oven, and add it to a high-speed mixer in sequence according to the mass ratio of artemisia powder to nano-ferric oxide of 15:1, so that the nanoparticles are evenly attached to the surface of the artemisia powder. Step 4: Preheat ethanol in a constant temperature water bath; slowly add the Artemisia argyi-nanoparticle composite system to the preheated ethanol and stir to fully soften the cell walls of the Artemisia argyi cells; Step 5: The impregnated mixture is sent to a vacuum rotary evaporator for de-alcoholization under reduced pressure; the de-alcoholized material is then air-dried at low temperature until it is loose and ready for use.

[0014] Preferably, the nano-sized iron(III) oxide used in the pretreatment of Artemisia argyi mentioned in this invention is prepared by chemical vapor deposition.

[0015] Preferably, the method for preparing nano-ferric oxide by chemical vapor deposition mentioned in this invention includes the following steps: Step 1: Select analytical grade ferrocene as the iron source and anhydrous ethanol as the solvent. Under nitrogen protection, slowly add ferrocene to anhydrous ethanol, and then add glucose as a carbon source auxiliary agent. Stir with a magnetic stirrer to form a homogeneous, precipitate-free ferrocene-glucose ethanol solution, and seal and store it in a brown reagent bottle for later use. Step 2: Select a single-crystal silicon wafer as the deposition substrate. First, place it in an ultrasonic cleaning tank filled with acetone to remove surface organic contaminants. Then, replace it with anhydrous ethanol and perform ultrasonic cleaning again. Finally, use deionized water for ultrasonic cleaning. After completion, place the substrate in a forced-air drying oven to dry it. After taking it out, place it in an oxygen plasma treatment instrument to introduce hydroxyl bonds on the silicon wafer surface to improve the uniformity of subsequent Fe3O4 nucleation. After treatment, immediately place it in a desiccator to cool to room temperature. Step 3: High-purity argon is selected as the carrier gas and oxygen as the reaction gas. The gas is dehydrated and impurity removed by a gas purification device equipped with a 5A molecular sieve. The purified gas is connected to the gas path control system and calibrated by a mass flow controller. An additional "Zn(acac)2 vapor pipeline" is added for subsequent auxiliary nucleation. Step 4: Evacuate the reaction chamber to below 5 Pa, turn off the vacuum pump and maintain the pressure to ensure there is no air leakage in the reaction chamber; then fix the pretreated silicon wafer on the quartz sample holder in the middle of the reaction chamber, ensuring that the substrate surface is perpendicular to the airflow direction; Step 5: Start the argon gas supply line and introduce argon gas into the reaction chamber. At the same time, open the exhaust valve of the reaction chamber to replace the air in the reaction chamber. Then start the Zn(acac)2 vapor pipeline and introduce Zn(acac)2 vapor into the reaction chamber to deposit an ultrathin ZnO transition layer on the silicon wafer surface. Then stop the Zn(acac)2 supply and continue to purge the residual vapor with argon gas. Step 6: Turn on the heating system of the reaction chamber and start the heating program; during the heating process, monitor the internal temperature of the reaction chamber in real time with an infrared thermometer. When the temperature reaches 400℃, maintain this temperature to ensure that the temperature field of the reaction chamber is uniform and stable. Step 7: Connect the prepared ferrocene-glucose ethanol solution to the micro-injection pump, and simultaneously raise the temperature of the vaporization chamber to 180°C; start the micro-injection pump, and the solution enters the vaporization chamber through the conduit and vaporizes rapidly. The precursor vapor formed is carried by the argon carrier gas and enters the reaction chamber with a stable gas flow. Step 8: While introducing the precursor vapor, start the oxygen gas path and adjust it to argon:oxygen = 8:1. Use a gas mixer to fully mix argon, oxygen and precursor vapor to ensure that the mixed gas is evenly distributed in the reaction chamber. Step 9: After the deposition reaction begins, observe the surface condition of the substrate through the observation window of the reaction chamber, and record the pressure, temperature and gas flow parameters of the reaction chamber at the same time. During this period, ferrocene vapor decomposes into elemental iron, which reacts with oxygen to generate Fe3O4. Glucose is simultaneously pyrolyzed to form an amorphous carbon layer to coat Fe3O4. The ZnO transition layer assists in nucleation and inhibits particle agglomeration. Step 10: After deposition for a period of time, first turn off the micro-injection pump and stop the supply of precursor solution; keep the flow rates of argon and oxygen constant and continue to introduce mixed gas into the reaction chamber to thoroughly purge the unreacted precursor vapor and reaction byproducts remaining in the reaction chamber. Step 11: Turn off the heating system of the reaction chamber, adjust the argon flow rate, and shut off the oxygen supply to allow the reaction chamber to cool down naturally under argon protection; record the cooling rate in real time through the temperature monitoring system. Step 12: When the internal temperature of the reaction chamber drops below 50°C, shut off the argon gas supply and stop the gas supply; open the reaction chamber door, use quartz tweezers to remove the silicon wafer sample with the deposited Fe3O4 nanofilm, and immediately place it in a desiccator to avoid moisture absorption or contamination of the sample; Step 13: Place the extracted sample into a petri dish containing dilute hydrochloric acid to soak and remove the ZnO transition layer. Then rinse with anhydrous ethanol and use a soft brush to scrub the sample surface to remove loose particles. Place the sample in a vacuum drying oven to dry, and obtain a mesoporous nanoscale Fe3O4 sample.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention applies nano-ferric oxide-assisted supercritical carbon dioxide extraction technology to the extraction of Artemisia argyi essential oil. By leveraging the efficient cell wall disruption and magnetic response recovery characteristics of nano-ferric oxide, it solves the problems of insufficient destruction of the dense cell walls of Artemisia argyi and low essential oil extraction rate in traditional supercritical carbon dioxide extraction. This significantly improves the extraction efficiency of its unique active ingredients (such as terpenes and flavonoids), fully releasing the industrial value of Artemisia argyi. At the same time, relying on the green and environmentally friendly advantages of supercritical carbon dioxide and the reusability of nanomaterials, it avoids the problems of chemical auxiliary agent residues or high energy consumption, enriches the extraction process of characteristic Artemisia argyi essential oil, and helps its high-quality application in the fields of medicine and daily chemicals. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a supercritical carbon dioxide analyzer; Figure 2 This is a schematic diagram of the uniform flow dispersion grid; Figure 3 This is a structural diagram of the motor and stirring shaft; Figure 4 These are iron oxide particles on a 3μm scale; Figure 5 These are iron oxide particles on a 20μm scale; Figure 6 These are iron oxide particles on a 2μm scale; Figure 7 These are iron oxide particles on a 5μm scale; In the diagram above: 1. Carbon dioxide gas tank; 2. High-pressure pump; 3. Motor; 4. Uniform flow dispersion grid; 5. Turning cylinder; 6. Impurity blocking uniform flow screen; 7. Pressure reducing valve; 8. Separation vessel; 9. Discharge valve; 10. Collection tank; 11. Booster pump; 12. Gas delivery pipe; 13. Material delivery pipe; 14. Recovered gas pipe; 4.1 Uniform flow grid; 5.1. Stirring shaft; 5.2. Propeller blade. Detailed Implementation

[0018] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0019] The method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide as mentioned in this invention includes the following steps: I. Pretreatment of Artemisia argyi: The raw material of Artemisia argyi undergoes the following pretreatment: Step 1: Select fresh mugwort that is free from mold and pests, place it in a constant temperature forced-air drying oven, and dry it at 60℃ for 24 hours to reduce the moisture content of the mugwort to 8%-10%; then remove withered leaves, hard stem segments and mud and sand impurities by a vibrating screening machine, leaving only the leaves and tender stems. Step 2: First, use a jaw crusher to coarsely crush the mugwort into small pieces of 2-5cm, and then send it to a universal pulverizer for fine crushing; after crushing, the material is screened through a 40-mesh standard sieve, the mugwort powder under the sieve is collected, and the coarse material on the sieve is returned to the universal pulverizer for secondary crushing. Step 3: Place the nano-ferric oxide in a vacuum drying oven and dry at 80°C for 2 hours; according to the mass ratio of Artemisia argyi powder to nano-ferric oxide of 15:1, put them into a high-speed mixer in sequence, first premix at 500 rpm for 3 minutes, then mix at 1500 rpm for 10 minutes, so that the nanoparticles are evenly attached to the surface of Artemisia argyi powder. Step 4: Preheat 95% food-grade ethanol to 35°C in a constant temperature water bath; slowly add the Artemisia argyi-nanoparticle composite system to the preheated ethanol, first stir at 150 rpm for 10 min, then stir at 300 rpm for 20 min, and soak for a total of 30 min to fully soften the cell walls of the Artemisia argyi cells. Step 5: The impregnated mixture is sent to a vacuum rotary evaporator and subjected to de-alcoholization at 45℃ and -0.08MPa for 15 minutes (residual ethanol content ≤1%). The de-alcoholized material is then air-dried at ≤50℃ until it is loose and ready for use.

[0020] II. Supercritical carbon dioxide extraction of Artemisia argyi essential oil, including the following steps: Step 1: Open the turning drum 5 of the supercritical carbon dioxide instrument, add the pretreated mugwort into the turning drum 5, close the turning drum 5, turn on the motor 3, and let the spiral agitator rotate. The pretreated mugwort begins to be disturbed under the action of the spiral blade 22. Step 2: Open carbon dioxide cylinder 1. Carbon dioxide gas reaches high pressure pump 2 through gas delivery pipe 12. Under the action of high pressure pump 2, the gas pressure is raised to the supercritical pressure of 20MPa-30MPa, and the carbon dioxide gas becomes supercritical carbon dioxide gas. Step 3: Supercritical carbon dioxide gas reaches the uniform flow dispersion grid 4. The gas quickly fills the fast air inlet section 19 at the bottom of the uniform flow dispersion grid 4. Then, under the action of the uniform flow grid section 18 at the top, the concentrated gas flow is dispersed, which plays a role in uniform flow and ensures that the gas can contact the Artemisia argyi raw material evenly, thereby improving the efficiency of extraction, reaction and other processes. Step 4: The gas passes through the uniform flow dispersion grid 4 and reaches the turning cylinder 5. Through the external heating jacket, the temperature inside the cylinder is raised to above 31°C. Under the action of the propeller blades 22, the pretreated Artemisia argyi raw material comes into full contact with supercritical carbon dioxide. In this process, the nano-sized iron oxide adsorbed on the pretreated Artemisia argyi raw material will assist the supercritical carbon dioxide gas in breaking the cell wall and improving the extraction rate of Artemisia argyi essential oil. Step 5: When the supercritical carbon dioxide gas reaches the top of the turning cylinder 5, it will be blocked by the lower filter diversion cover 17 at the bottom of the impurity-blocking and uniform flow screen 6, ensuring that the supercritical carbon dioxide gas will not flow out too quickly, further ensuring the extraction efficiency of mugwort essential oil. At the same time, the lower filter diversion cover 17 will also filter the essential oil and mugwort raw materials. Under the action of its fine mesh, the essential oil flows through evenly. The supercritical carbon dioxide analyzer mentioned in this invention includes a carbon dioxide tank 1, a high-pressure pump 2, a motor 3, a uniform flow dispersion grid 4, a tilting cylinder 5, a sieve for preventing impurities and promoting uniform flow 6, a pressure reducing valve 7, a separation vessel 8, a discharge valve 9, a collection tank 10, a booster pump 11, a gas supply pipe 12, a material supply pipe 13, and a recovery gas pipe 14. The uniform flow dispersion grid 4 is installed on the lower side of the tilting cylinder 5, and the motor 3 is installed on the lower part of the uniform flow dispersion grid 4. The sieve for preventing impurities and promoting uniform flow 6 is installed on the upper side of the tilting cylinder 5. One end of the material supply pipe 13 is connected to the sieve for preventing impurities and promoting uniform flow 6, and the other end is connected to the separation vessel 8 through the pressure reducing valve 7. One side of the uniform flow dispersion grid 4 is connected to the carbon dioxide tank 1 through the gas supply pipe 12 and the high-pressure pump 2. The upper end of the carbon dioxide tank 1 is connected to the top of the separation vessel 8 through the recovery gas pipe 14 and the booster pump 11. The discharge valve 9 is installed at the bottom of the separation vessel 8, and the collection tank 10 is installed below the separation vessel 8.

[0021] The uniform flow dispersion grid 4 mentioned in this invention has a uniform flow grid 4.1 inside, and filter divider screens are installed at the upper and lower ends of the impurity blocking uniform flow screen 6 respectively; the output end of the motor 3 is connected to the stirring shaft 5.1 through the transmission shaft, and propeller blades 5.2 are distributed outside the stirring shaft 5.1.

[0022] Step 6: The mugwort essential oil reaches the pressure reducing valve 7 through the feed pipe 13. At this time, the pressure decreases, causing the supercritical carbon dioxide in the mugwort essential oil to precipitate due to the pressure drop, thus achieving a separation effect. Step 7: The separated mugwort essential oil reaches the separation vessel 8 and flows into the collection tank 10 through the discharge valve 9 at its bottom. The separated carbon dioxide gas enters the booster pump 11 through the recovery gas pipe 14. Under the action of the booster pump 11, the recovered carbon dioxide gas is pumped back into the carbon dioxide gas tank 1 to realize the recovery and utilization of carbon dioxide gas. III. Recovery of nano-ferric oxide and purification of crude artemisia essential oil: Step 1: Transfer the CO2-free crude mugwort essential oil (containing impurities such as nano-ferric oxide and wax) into a sealed adsorption tank with a stirring function. Turn on the stirring at 150-200 r / min to make the liquid uniform. Insert an electric electromagnetic rod and completely immerse it. Maintain a magnetic field strength of 0.3-0.5T for 20-30 minutes for adsorption. Turn off the stirring and let it stand for 5 minutes. Then remove the electromagnetic rod to complete the separation of nano-ferric oxide and essential oil. Step 2: Place the electromagnetic rod with adsorbed nano-iron oxide into anhydrous ethanol and ultrasonically clean it for 10-15 minutes to remove the essential oil residue adhering to the surface. Step 3: Turn off the power to the electromagnetic rod. After the magnetic field is lost, the nano-iron oxide will fall off. Centrifuge (3000-5000 r / min, 5 min) to collect the nanoparticles at the bottom. Step 4: Place the collected nano-ferric oxide in a vacuum drying oven and dry it at 60-80℃ for 2 hours to restore its dispersibility and magnetic activity, so that it can be used for extraction again. Step 5: Pass the essential oil liquid separated in Step 1 into a precision filtration device, using a 0.22μm organic filter membrane, and control the filtration pressure at 0.2-0.3MPa to trap impurities such as wax and plant solid particles, and collect the clarified essential oil liquid. Step 6: Send the clarified essential oil liquid into a molecular distillation device, set the evaporation temperature to 60-70℃, the condensation temperature to 10-15℃, and the system vacuum degree to 1-5Pa. Separate trace impurities and highly active ingredients by the difference in boiling points, and collect the distillate to obtain high-purity Artemisia argyi essential oil. Step 7: Test the residual amount, purity, and active ingredient content of the purified essential oil in nano-ferric oxide. If it passes the test, store it in a brown sealed container in a cool, dry place.

[0023] Example 2 differs from Example 1 in that: The nano-sized iron oxide mentioned in this invention is prepared by chemical vapor deposition, specifically including the following process: Step 1: Select analytical grade ferrocene (C 10 H 10 Using Fe as the iron source and anhydrous ethanol as the solvent, ferrocene was slowly added to anhydrous ethanol at a concentration of 0.08 mol / L at room temperature (25°C) under nitrogen protection. Glucose (0.02 mol / L) was then added as a carbon source auxiliary agent. The mixture was stirred at 300 rpm for 25 min using a magnetic stirrer to form a homogeneous, precipitate-free ferrocene-glucose ethanol solution, which was then sealed and stored in a brown reagent bottle for later use. Step 2: Select a single-crystal silicon wafer (10mm×10mm×0.5mm) as the deposition substrate. First, place it in an ultrasonic cleaning tank filled with acetone, set the ultrasonic power to 150W and the frequency to 40kHz, and ultrasonically clean for 18 minutes to remove surface organic contaminants. Then, replace it with anhydrous ethanol and clean for 18 minutes while maintaining the same ultrasonic parameters. Finally, ultrasonically clean with deionized water for 18 minutes. After completion, place the substrate in a 105℃ forced-air drying oven to dry for 30 minutes. After removal, place it in an oxygen plasma treatment instrument, set the power to 80W and the oxygen flow rate to 10sccm, and treat for 5 minutes to introduce hydroxyl bonds on the silicon wafer surface, thereby improving the uniformity of subsequent Fe3O4 nucleation. After treatment, immediately place it in a desiccator to cool to room temperature. Step 3: High-purity argon (99.999%) is used as the carrier gas, and oxygen (99.99%) is used as the reaction gas. Both are dehydrated and purified using a gas purification device equipped with a 5A molecular sieve. The purified gases are then connected to the gas path control system and calibrated using a mass flow controller to ensure that the argon flow rate error is ≤ ±1 sccm and the oxygen flow rate error is ≤ ±0.5 sccm. An additional "Zn(acac)2 vapor pipeline" is added for subsequent auxiliary nucleation. Step 4: Turn on the main power of the CVD reaction system, check whether the sealing gasket of the reaction chamber door is intact, close the door and start the vacuum pump to evacuate the vacuum degree of the reaction chamber to below 5Pa, turn off the vacuum pump and maintain the pressure for 10 minutes, observe the vacuum degree change ≤0.2Pa, and confirm that there is no air leakage in the reaction chamber; then fix the pretreated silicon wafer on the quartz sample holder in the middle of the reaction chamber, ensuring that the substrate surface is perpendicular to the airflow direction; Step 5: Start the argon gas supply line, set the flow rate to 80 sccm, and introduce argon gas into the reaction chamber. At the same time, open the reaction chamber exhaust valve and control the exhaust rate to maintain the reaction chamber pressure at 101 kPa. Continue to introduce argon gas for 12 minutes to complete the replacement of air in the reaction chamber. Then start the Zn(acac)2 vapor pipeline, set the vaporization temperature to 120℃ and the carrier gas flow rate to 5 sccm, and introduce Zn(acac)2 vapor into the reaction chamber for 10 minutes to deposit an ultrathin ZnO transition layer (approximately 5 nm thick) on the silicon wafer surface. Then stop the Zn(acac)2 supply and continue to introduce argon gas for 5 minutes to purge the residual vapor. Step 6: Turn on the heating system of the reaction chamber, set the heating rate to 8℃ / min, the target temperature to 400℃, and start the heating program; during the heating process, monitor the internal temperature of the reaction chamber in real time with an infrared thermometer to ensure that the actual temperature deviates from the set temperature by ≤±2℃. When the temperature reaches 400℃, maintain this temperature for 15 minutes to make the temperature field of the reaction chamber uniform and stable. Step 7: Connect the ferrocene-glucose ethanol solution prepared in Step 1 to the micro-injection pump, set the injection rate to 0.3 mL / min, and simultaneously raise the temperature of the vaporization chamber to 180℃ and keep it at that temperature for 5 min; start the micro-injection pump, and the solution enters the vaporization chamber through the conduit and vaporizes rapidly. The precursor vapor formed is carried by the argon carrier gas and enters the reaction chamber with a stable gas flow. Step 8: While introducing the precursor vapor, start the oxygen gas path, set the oxygen flow rate to 10 sccm, and adjust the argon:oxygen ratio to 8:1 to improve the oxidation sufficiency of Fe3O4. Control the total gas flow rate at 190 sccm. Use a gas mixer to fully mix argon, oxygen and precursor vapor to ensure that the mixed gas is evenly distributed in the reaction chamber. Step 9: After the deposition reaction begins, observe the surface condition of the substrate through the observation window of the reaction chamber every 6 minutes, and record the pressure, temperature and gas flow rate parameters of the reaction chamber at the same time; keep the deposition time at 40 minutes. During this period, ferrocene vapor decomposes into elemental iron, which reacts with oxygen to generate Fe3O4. Glucose is simultaneously pyrolyzed to form an amorphous carbon layer to coat Fe3O4. The ZnO transition layer assists in nucleation and inhibits particle agglomeration. Step 10: After the deposition time reaches 40 min, first turn off the micro-injection pump and stop the supply of precursor solution; keep the flow rates of argon and oxygen constant, and continue to introduce mixed gas into the reaction chamber for 15 min to thoroughly purge the unreacted precursor vapor and reaction byproducts remaining in the reaction chamber. Step 11: Turn off the heating system of the reaction chamber, adjust the argon flow rate to 100 sccm, and shut off the oxygen supply to allow the reaction chamber to cool down naturally under argon protection; record the cooling rate in real time through the temperature monitoring system to ensure that the cooling rate is ≤8℃ / min (to reduce stress risk) and avoid sample cracking; Step 12: When the internal temperature of the reaction chamber drops below 50°C, shut off the argon gas supply and stop the gas supply; open the reaction chamber door, use quartz tweezers to remove the silicon wafer sample with the deposited Fe3O4 nanofilm, and immediately place it in a desiccator to avoid moisture absorption or contamination of the sample; Step 13: Place the extracted sample into a petri dish containing 0.1 mol / L dilute hydrochloric acid and soak for 5 min (to remove the ZnO transition layer). Then rinse three times with anhydrous ethanol and gently brush the sample surface with a soft brush to remove loose particles. Place the sample in a vacuum drying oven at 60℃ and dry for 20 min to obtain a mesoporous nanoscale Fe3O4 sample. Step Fourteen: Cut the dried sample into 2mm×2mm pieces, fix them on the sample stage of the scanning electron microscope (SEM) with conductive adhesive, and sputter gold for 30 seconds to enhance the conductivity of the sample. Step 15: Observe the surface morphology of the sample using a scanning electron microscope (SEM) (magnification 50,000x) to confirm that Fe3O4 is nanoscale. Figure 4 , Figure 5 , Figure 6 , Figure 7 Simultaneously, XRD characterization confirmed the phase purity of Fe3O4.

[0024] The above description is merely a partial preferred embodiment of the present invention. Any person skilled in the art can modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide, characterized in that: The process includes the following: I. Artemisia argyi pretreatment: Pretreatment of raw Artemisia argyi; Nano-Fe3O4 was placed in a vacuum drying oven and fed into a high-speed mixer in a mass ratio of 15:1 between Artemisia argyi powder and nano-Fe3O4, so that the nanoparticles were evenly attached to the surface of Artemisia argyi powder. II. Supercritical carbon dioxide extraction of Artemisia argyi essential oil; III. Recovery of nano-ferric oxide and purification of crude artemisia essential oil: Step 1: Transfer the crude mugwort essential oil, which has been de-CO2 removed, into a sealed adsorption tank with a stirring function. Stir to make the liquid uniform, insert an electric electromagnetic rod and completely immerse it, maintain a magnetic field strength of 0.3-0.5T for adsorption, turn off the stirring and let it stand, then remove the electromagnetic rod to complete the separation of nano-iron oxide from the essential oil. Step 2: Place the electromagnetic rod with adsorbed nano-iron oxide into anhydrous ethanol and ultrasonically clean it to remove the essential oil residue adhering to the surface. Step 3: Turn off the power to the electromagnetic rod. After the magnetic field is lost, the nano-iron oxide will fall off. Centrifuge to separate and collect the nanoparticles at the bottom. Step 4: Place the collected nano-Fe3O4 in a vacuum drying oven to restore its dispersibility and magnetic activity, and then reuse it for extraction. Step 5: Pass the essential oil liquid separated in Step 1 into a precision filter to trap waxy and plant solid particle impurities, and collect the clear essential oil liquid; Step Six: The clarified essential oil liquid is fed into a molecular distillation apparatus to separate trace impurities and highly active ingredients by the difference in boiling points. The distillate is then collected as high-purity Artemisia argyi essential oil. Step 7: Test the residual amount, purity, and active ingredient content of the purified essential oil in nano-ferric oxide. If it passes the test, store it in a brown sealed container in a cool, dry place.

2. The method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide according to claim 1, characterized in that: Supercritical carbon dioxide extraction of Artemisia argyi essential oil includes the following steps: Step 1: Open the turning drum (5) of the supercritical carbon dioxide instrument, add the pretreated mugwort into the turning drum (5), close the turning drum (5), turn on the motor (3), and let the spiral stirring paddle rotate. The pretreated mugwort begins to be disturbed under the action of the spiral blade (22). Step 2: Open the carbon dioxide gas tank (1), and the carbon dioxide gas reaches the high pressure pump (2) through the gas delivery pipe (12). Under the action of the high pressure pump (2), the gas pressure is raised to the supercritical pressure of 20MPa-30MPa, and the carbon dioxide gas becomes supercritical carbon dioxide gas. Step 3: Supercritical carbon dioxide gas reaches the uniform flow dispersion grid (4), and the gas quickly fills the fast air inlet section (19) at the bottom of the uniform flow dispersion grid (4). Then, under the action of the uniform flow grid section (18) at the top, the concentrated gas flow is dispersed, which plays a role in uniform flow and ensures that the gas can contact the Artemisia argyi raw material evenly, thereby improving the efficiency of the extraction and reaction process. Step 4: The gas passes through the uniform flow dispersion grid (4) and reaches the turning cylinder (5). The temperature inside the cylinder is raised by the external heating jacket. Under the action of the propeller blades (22), the pretreated Artemisia argyi raw material comes into full contact with supercritical carbon dioxide. In this process, the nano-sized iron tetroxide adsorbed on the pretreated Artemisia argyi raw material will assist the supercritical carbon dioxide gas in breaking the cell wall and improving the extraction rate of Artemisia argyi essential oil. Step 5: When the supercritical carbon dioxide gas reaches the top of the turning cylinder (5), it is blocked by the lower filter diversion cover (17) at the bottom of the impurity-blocking uniform flow screen (6), which further ensures the extraction efficiency of mugwort essential oil. At the same time, the lower filter diversion cover (17) also plays a filtering role on the essential oil and mugwort raw materials. Under the action of its internal mesh, the essential oil flows through evenly. Step 6: Artemisia essential oil reaches pressure reducing valve (7) through feed pipe (13). At this time, the pressure decreases, causing the supercritical carbon dioxide in the Artemisia essential oil to precipitate due to the pressure drop, thus playing a separation role. Step 7: The separated Artemisia argyi essential oil reaches the separation vessel (8) and flows into the collection tank (10) through the discharge valve (9) at its bottom. The separated carbon dioxide gas enters the booster pump (11) through the recovery gas pipe (14). Under the action of the booster pump (11), the recovered carbon dioxide gas is pumped back into the carbon dioxide gas tank (1) to realize the recovery and utilization of carbon dioxide gas.

3. The method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide according to claim 2, characterized in that: The supercritical carbon dioxide instrument includes a carbon dioxide tank (1), a high-pressure pump (2), a motor (3), a uniform flow dispersion grid (4), a turning cylinder (5), a sieve for preventing impurities and uniform flow (6), a separation vessel (8), a collection tank (10), a booster pump (11), a gas supply pipe (12), a feed pipe (13), and a recovery gas pipe (14). The uniform flow dispersion grid (4) is installed on the lower side of the turning cylinder (5), and the motor (3) is installed on the lower part of the uniform flow dispersion grid (4). The sieve for preventing impurities and uniform flow (6) is installed on the upper side of the turning cylinder (5). One end of the feed pipe (13) is connected to the sieve for preventing impurities and uniform flow (6), and the other end is connected to the separation vessel (8). One side of the uniform flow dispersion grid (4) is connected to the carbon dioxide tank (1) through the gas supply pipe (12) and the high-pressure pump (2). The upper end of the carbon dioxide tank (1) is connected to the top of the separation vessel (8) through the recovery gas pipe (14) and the booster pump (11). The collection tank (10) is installed below the separation vessel (8).

4. The method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide according to claim 3, characterized in that: The uniform flow dispersion grid (4) is provided with a uniform flow grid (4.1) inside, and the upper and lower ends of the impurity blocking uniform flow screen (6) are respectively equipped with filter diversion screens; the output end of the motor (3) is connected to the stirring shaft (5.1) through the transmission shaft, and the propeller blades (5.2) are distributed outside the stirring shaft (5.1).

5. The method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide according to claim 4, characterized in that: The specific steps for pre-treating mugwort are as follows: Step 1: Select fresh mugwort that is free from mold and pests, place it in a constant temperature forced-air drying oven, and dry it at 60℃ for 24 hours to reduce the moisture content of the mugwort to 8%-10%; then remove withered leaves, hard stem segments and mud impurities by vibrating screening machine, leaving only the leaves and tender stems. Step 2: First, use a jaw crusher to coarsely crush the mugwort into small pieces, then send it to a universal pulverizer for fine crushing; after crushing, sieve and collect the mugwort powder that is not sieved, and return the coarse material that is sieved to the universal pulverizer for secondary crushing; Step 3: Place the nano-ferric oxide in a vacuum drying oven, and add it to a high-speed mixer in sequence according to the mass ratio of artemisia powder to nano-ferric oxide of 15:1, so that the nanoparticles are evenly attached to the surface of the artemisia powder. Step 4: Preheat ethanol in a constant temperature water bath; slowly add the Artemisia argyi-nanoparticle composite system to the preheated ethanol and stir to fully soften the cell walls of the Artemisia argyi cells; Step 5: The impregnated mixture is sent to a vacuum rotary evaporator for de-alcoholization under reduced pressure; the de-alcoholized material is then air-dried at low temperature until it is loose and ready for use.

6. The method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide according to claim 5, characterized in that: The nano-sized iron(III) oxide used in the pretreatment of Artemisia argyi was prepared by chemical vapor deposition.

7. The method for extracting Artemisia argyi essential oil using nano-ferric oxide-assisted supercritical carbon dioxide according to claim 6, characterized in that: A method for preparing nano-sized iron(III) oxide by chemical vapor deposition includes the following steps: Step 1: Select analytical grade ferrocene as the iron source and anhydrous ethanol as the solvent. Under nitrogen protection, slowly add ferrocene to anhydrous ethanol, and then add glucose as a carbon source auxiliary agent. Stir with a magnetic stirrer to form a homogeneous, precipitate-free ferrocene-glucose ethanol solution, and seal and store it in a brown reagent bottle for later use. Step 2: Select a single-crystal silicon wafer as the deposition substrate. First, place it in an ultrasonic cleaning tank filled with acetone to remove surface organic contaminants. Then, replace it with anhydrous ethanol and perform ultrasonic cleaning again. Finally, use deionized water for ultrasonic cleaning. After completion, place the substrate in a forced-air drying oven to dry it. After taking it out, place it in an oxygen plasma treatment instrument to introduce hydroxyl bonds on the silicon wafer surface to improve the uniformity of subsequent Fe3O4 nucleation. After treatment, immediately place it in a desiccator to cool to room temperature. Step 3: High-purity argon is selected as the carrier gas and oxygen as the reaction gas. The gas is dehydrated and impurity removed by a gas purification device equipped with a 5A molecular sieve. The purified gas is connected to the gas path control system and calibrated by a mass flow controller. An additional "Zn(acac)2 vapor pipeline" is added for subsequent auxiliary nucleation. Step 4: Evacuate the reaction chamber to below 5 Pa, turn off the vacuum pump and maintain the pressure to ensure there is no air leakage in the reaction chamber; then fix the pretreated silicon wafer on the quartz sample holder in the middle of the reaction chamber, ensuring that the substrate surface is perpendicular to the airflow direction; Step 5: Start the argon gas supply line and introduce argon gas into the reaction chamber. At the same time, open the exhaust valve of the reaction chamber to replace the air in the reaction chamber. Then start the Zn(acac)2 vapor pipeline and introduce Zn(acac)2 vapor into the reaction chamber to deposit an ultrathin ZnO transition layer on the silicon wafer surface. Then stop the Zn(acac)2 supply and continue to purge the residual vapor with argon gas. Step 6: Turn on the heating system of the reaction chamber and start the heating program; during the heating process, monitor the internal temperature of the reaction chamber in real time with an infrared thermometer. When the temperature reaches 400℃, maintain this temperature to ensure that the temperature field of the reaction chamber is uniform and stable. Step 7: Connect the prepared ferrocene-glucose ethanol solution to the micro-injection pump, and simultaneously raise the temperature of the vaporization chamber to 180°C; start the micro-injection pump, and the solution enters the vaporization chamber through the conduit and vaporizes rapidly. The precursor vapor formed is carried by the argon carrier gas and enters the reaction chamber with a stable gas flow. Step 8: While introducing the precursor vapor, start the oxygen gas path and adjust it to argon:oxygen = 8:

1. Use a gas mixer to fully mix argon, oxygen and precursor vapor to ensure that the mixed gas is evenly distributed in the reaction chamber. Step 9: After the deposition reaction begins, observe the surface condition of the substrate through the observation window of the reaction chamber, and record the pressure, temperature and gas flow parameters of the reaction chamber at the same time. During this period, ferrocene vapor decomposes into elemental iron, which reacts with oxygen to generate Fe3O4. Glucose is simultaneously pyrolyzed to form an amorphous carbon layer to coat Fe3O4. The ZnO transition layer assists in nucleation and inhibits particle agglomeration. Step 10: After deposition for a period of time, first turn off the micro-injection pump and stop the supply of precursor solution; keep the flow rates of argon and oxygen constant and continue to introduce mixed gas into the reaction chamber to thoroughly purge the unreacted precursor vapor and reaction byproducts remaining in the reaction chamber. Step 11: Turn off the heating system of the reaction chamber, adjust the argon flow rate, and shut off the oxygen supply to allow the reaction chamber to cool down naturally under argon protection; record the cooling rate in real time through the temperature monitoring system. Step 12: When the internal temperature of the reaction chamber drops below 50°C, shut off the argon gas supply and stop the gas supply; open the reaction chamber door, use quartz tweezers to remove the silicon wafer sample with the deposited Fe3O4 nanofilm, and immediately place it in a desiccator to avoid moisture absorption or contamination of the sample; Step 13: Place the extracted sample into a petri dish containing dilute hydrochloric acid to soak and remove the ZnO transition layer. Then rinse with anhydrous ethanol and use a soft brush to scrub the sample surface to remove loose particles. Place the sample in a vacuum drying oven to dry, and obtain a mesoporous nanoscale Fe3O4 sample.

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