Method for treating microplastics and benzothiazole pollutants by electric stimulation and anaerobic microorganisms

Abstract

The embodiment of the application discloses a method for treating microplastics and benzothiazole pollutants by electric stimulation and anaerobic microorganisms, relates to the technical field of environmental pollution treatment, and can effectively improve the treatment effect and efficiency of pollutants. The method comprises the following steps: arranging an anode and a cathode in a treatment medium containing microplastics and benzothiazole pollutants at a preset interval, wherein the treatment medium also contains anaerobic microorganisms; adding an electrolyte to the treatment medium and adjusting the electrolyte to a preset conductivity; connecting the anode and the cathode to a direct current power supply and applying a preset voltage to the treatment medium, and electrically stimulating the treatment medium at a preset temperature for a preset time. The application is suitable for pollution treatment scenes.

Description

Technical Field

[0001] This application relates to the field of environmental pollution control technology, specifically to a method for treating microplastics and benzothiazole pollutants by electrostimulation in conjunction with anaerobic microorganisms. Background Technology

[0002] With the widespread use of plastic products and the rapid development of the chemical industry, plastic products in the environment continuously undergo oxidation and degradation processes, forming and releasing microplastics (plastic fragments and particles with a diameter of less than 5 mm) and nanoplastics (NPs, plastic particles with a diameter of less than 100 nanometers). Microplastics can coexist in water bodies for extended periods, posing potential environmental risks. Furthermore, during plastic manufacturing and molding processes, various additives, such as benzothiazole compounds, are added to polymers in specific proportions. Benzothiazole compounds are typical nitrogen-containing heterocyclic organic pollutants with stable chemical structures, exhibiting biotoxicity and recalcitrant degradation characteristics. Their persistent presence in the environment poses a serious threat to ecosystems and human health. Microplastics, characterized by their small particle size, large specific surface area, and strong adsorption capacity, readily adsorb organic pollutants such as benzothiazoles, forming complex pollution systems. Therefore, the problem of combined pollution by microplastics and benzothiazole pollutants in aquatic and soil environments is becoming increasingly prominent.

[0003] Traditional pollution treatment technologies, such as adsorption, photocatalysis, and biodegradation, suffer from problems such as long treatment cycles, slow synergistic removal efficiency for complex pollutants, and the generation of secondary products. Among these, biodegradation has lower costs and produces relatively clean and environmentally friendly products that can be recycled. However, biodegradation is extremely inefficient at breaking down microplastics, and benzothiazole pollutants can inhibit microbial activity. Summary of the Invention

[0004] In view of this, this application provides a method for treating microplastics and benzothiazole pollutants by electrostimulation in conjunction with anaerobic microorganisms, which can effectively improve the treatment effect and efficiency of pollutants.

[0005] An embodiment of this application provides a method for treating microplastics and benzothiazole pollutants using electrostimulation in conjunction with anaerobic microorganisms, comprising: placing an anode and a cathode at a preset distance in a medium containing microplastics and benzothiazole pollutants, wherein the medium also contains anaerobic microorganisms; adding an electrolyte to the medium and adjusting it to a preset conductivity; connecting the anode and the cathode to a DC power supply and applying a preset voltage; and electrostimulating the medium at a preset temperature for a preset duration.

[0006] In one specific implementation, the medium to be treated contains sludge, the sludge contains anaerobic microorganisms, and the liquid-to-solid ratio of the water in the medium to the sludge is (5-10):1.

[0007] In one specific implementation, after the medium to be treated is electrically stimulated for a preset time at a preset temperature, the method further includes: allowing the medium to be treated to settle or filter, and extracting a quantitative sample from the medium at preset intervals to measure the concentration of microplastics and benzothiazole pollutants in the sample; performing solid-liquid separation on the sludge suspension in the medium to be treated, and recycling it after separation and drying.

[0008] In one specific implementation, the anode is a carbon fiber brush electrode loaded with nano-zero valent iron, and the cathode is a graphite electrode.

[0009] In one specific implementation, the preset conductivity is 5-20 mS / cm, the electrolyte is persulfate, and the amount of electrolyte added is 0.5-2 g / L.

[0010] In one specific implementation, the preset distance between the anode and the cathode is 4-6 cm; the preset voltage is 0.8-1.2V; the preset temperature is 35±5℃; and the preset duration is 72-96 hours.

[0011] In one specific implementation, the preset duration of the electrical stimulation response of the medium to be treated at a preset temperature further includes: during the electrical stimulation response, continuously stirring the medium to be treated with a magnetic stirrer at a stirring rate of 300±50 r / min.

[0012] In one specific embodiment, the microplastics include at least one of the following: polyvinyl chloride, polypropylene, and polybutylene terephthalate; the particle size of the microplastics ranges from 0.12 to 0.15 mm.

[0013] In one specific implementation, before the electrical stimulation response of the medium to be treated at a preset temperature for a preset duration, the method further includes: introducing nitrogen gas into the medium to be treated at an aeration rate of 3 L / min to enhance the activity of anaerobic microorganisms.

[0014] In one specific implementation, the filter membrane used for filtration has a pore size ≤ 0.22 μm; the solid-liquid separation is performed by centrifugation, the centrifugation speed is 8000-10000 r / min, and the centrifugation time is ≥ 20 min.

[0015] The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms provided in the embodiments of this application first places the anode and cathode at a preset distance in a medium containing microplastics and benzothiazole pollutants, wherein the medium also contains anaerobic microorganisms; then, an electrolyte is added to the medium and adjusted to a preset conductivity; then, the anode and cathode are connected to a DC power supply and a preset voltage is applied, and the medium is electrostimulated at a preset temperature for a preset duration, thereby treating microplastics and benzothiazole pollutants under the synergistic effect of electrostimulation and anaerobic microorganisms. This method can effectively improve the treatment effect and efficiency of pollutants. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating a method for treating microplastics and benzothiazole contaminants using electrical stimulation in conjunction with anaerobic microorganisms, as provided in this application embodiment; Figure 2 This is a schematic diagram illustrating the principle of an electrically stimulated anaerobic microbial treatment of microplastics and benzothiazole pollutants, provided in an embodiment of this application.

[0018] Figure 3 The diagram illustrates the degradation effect of benzothiazole in microplastics (PVC and PBAT) and benzothiazole pollutants in an electrically stimulated anaerobic microbial treatment method, as provided in this application embodiment. Detailed Implementation

[0019] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0020] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0021] Current technologies for treating microplastics and benzothiazole pollutants in the environment, such as adsorption, photocatalysis, and biodegradation, suffer from problems including long treatment cycles, slow synergistic removal efficiency for complex pollutants, and the potential generation of secondary products. To address these issues, alternative technologies are needed. Figure 1 As shown, embodiments of this application provide a method for the synergistic treatment of microplastics and benzothiazole contaminants using electrical stimulation and anaerobic microorganisms. This method may include: S11. The anode and cathode are placed at a preset distance in the medium to be treated, which contains microplastics and benzothiazole pollutants, and the medium to be treated also contains anaerobic microorganisms.

[0022] In this embodiment, the medium to be treated can be contaminated water or soil suspension, etc., and the microplastics can be plastic fragments or particles with a diameter of less than 5 mm. Benzothiazole pollutants can specifically be benzothiazole or benzothiazole-2-carboxylic acid, etc.

[0023] The anode and cathode can be used to electrically stimulate the medium to be treated. Anaerobic microorganisms can work synergistically during anaerobic digestion to convert organic matter into methane and carbon dioxide. Anaerobic microorganisms can include hydrolytic fermenting bacteria, hydrogen-producing and acetic acid-producing bacteria, methanogenic archaea, sulfate-reducing bacteria, anaerobic ammonia-oxidizing bacteria, etc.

[0024] S12. Add electrolyte to the medium to be treated and adjust it to the preset conductivity.

[0025] Adding electrolytes to the medium to be treated to achieve a suitable preset conductivity can promote the conductivity and chemical reaction of the medium, thereby improving the treatment effect and efficiency of pollutants.

[0026] S13. Connect the anode and cathode to a DC power supply and apply a preset voltage. Set a preset time for the electrical stimulation reaction of the medium to be treated at a preset temperature.

[0027] Voltage and temperature are important factors affecting the reaction rate. In this embodiment, a DC power supply is used to apply a preset voltage to the anode and cathode, and the medium to be treated is configured to undergo an electrical stimulation reaction for a preset duration at a preset temperature, so as to improve the effect of electrical stimulation reaction under appropriate voltage, temperature and other parameters.

[0028] The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms provided in the embodiments of this application first places the anode and cathode at a preset distance in a medium containing microplastics and benzothiazole pollutants, wherein the medium also contains anaerobic microorganisms; then, an electrolyte is added to the medium and adjusted to a preset conductivity; then, the anode and cathode are connected to a DC power supply and a preset voltage is applied, and the medium is electrostimulated at a preset temperature for a preset duration, thereby treating microplastics and benzothiazole pollutants under the synergistic effect of electrostimulation and anaerobic microorganisms. This method can effectively improve the treatment effect and efficiency of pollutants.

[0029] Optionally, in one embodiment of this application, the medium to be treated contains sludge, the sludge contains anaerobic microorganisms, and the liquid-solid ratio of the water in the medium to the sludge is (5-10):1.

[0030] In this embodiment, a bioreactor can be constructed for the medium to be treated. The medium to be treated is polluted water, and the liquid-to-solid ratio of the water mass to the sludge mass in the medium to be treated is configured as (5-10):1. The sludge contains anaerobic microorganisms, which can be used for biodegradation and are easy to recycle and reuse.

[0031] Optionally, in one embodiment of this application, after step S13, where the medium to be treated is electrically stimulated for a preset time at a preset temperature, the method further includes: allowing the medium to be treated to settle or filter, and extracting a quantitative sample from the medium to be treated at preset intervals to measure the concentration of microplastics and benzothiazole pollutants in the sample; performing solid-liquid separation on the sludge suspension in the medium to be treated, and recycling it after separation and drying.

[0032] The medium to be treated is allowed to settle or be filtered, and quantitative samples are taken from the medium at preset intervals for measurement, such as 12 hours. If the concentration of microplastics and benzothiazole pollutants in the sample reaches the target value, the sludge suspension in the medium to be treated can be separated into solid and liquid components, dried, and then recycled for reuse to reduce the cost of pollutant treatment.

[0033] Optionally, in one embodiment of this application, the anode is a carbon fiber brush electrode loaded with nano-zero valent iron, and the cathode is a graphite electrode.

[0034] Carbon fiber brush electrodes are three-dimensional porous electrodes made with carbon fiber bundles as the core and metal wires such as titanium wires as the skeleton. They possess high specific surface area, excellent conductivity, corrosion resistance, and biocompatibility, making them suitable for efficient mass transfer and microbial attachment. Nano-zero-valent iron (nZVI) loaded on carbon fiber brush electrodes is a highly efficient nanomaterial for environmental remediation. Due to its extremely small particle size (typically less than 100 nanometers), it has a huge specific surface area and extremely high surface activity, enabling it to efficiently remove various pollutants from soil and groundwater. Figure 2 The diagram shown illustrates the principle of electrostimulation synergistic anaerobic microbial treatment of microplastics and benzothiazole pollutants in this embodiment. Under the action of the nano-zero-valent iron catalytic zone, active oxide species are generated, promoting the decomposition of organic matter and microplastics.

[0035] In this embodiment, the anode is a carbon fiber brush electrode loaded with nano-zero valent iron, which is conducive to the adhesion of microorganisms. Under electrical stimulation, the anode generates highly oxidizing active substances such as hydroxyl radicals and sulfate radicals, and the activity of electroactive anaerobic microorganisms is increased. This can, on the one hand, attack the chemical bonds on the surface of microplastics, causing the microplastics to undergo oxidative cleavage, gradually reducing the particle size until they decompose into small molecule organic matter; on the other hand, under the action of free radicals and anaerobic electroactive microorganisms, the heterocyclic structure of benzothiazole pollutants can be destroyed, achieving mineralization and decomposition. The cathode is a graphite electrode. The hydrogen gas and hydroxide ions and sulfate ions generated at the cathode can assist in the breakup of microplastics and the desorption of pollutants, further improving the synergistic treatment effect.

[0036] Optionally, in one embodiment of this application, the preset conductivity is 5-20 mS / cm, the electrolyte is persulfate, and the amount of electrolyte added is 0.5-2 g / L.

[0037] Persulfate has excellent solubility, providing a high concentration of ions. It completely dissociates in water and offers good conductivity, meeting the current density requirements of electrochemical devices. For example, in this embodiment, to configure the medium to be treated with a preset conductivity of 5-20 mS / cm, persulfate is added at a rate of 0.5-2 g / L relative to the medium to be treated.

[0038] Optionally, in one embodiment of this application, the preset distance between the anode and cathode is 4-6 cm; the preset voltage is 0.8-1.2V; the preset temperature is 35±5℃; and the preset duration is 72-96 hours.

[0039] The anode and cathode constitute a pair of electrodes. In this embodiment, in order to improve the reaction efficiency, multiple pairs of electrodes can be set in the medium to be treated. The preset distance between the anode and cathode of each pair of electrodes is 4-6 cm, so as to further improve the treatment effect and efficiency of pollutants in the medium to be treated.

[0040] Optionally, in one embodiment of this application, step S13, which involves the electrical stimulation reaction of the medium to be treated at a preset temperature for a preset duration, further includes: during the electrical stimulation reaction, using a magnetic stirrer to continuously stir the medium to be treated at a stirring rate of 300±50 r / min.

[0041] By equipping the bioreactor containing the medium to be treated with a magnetic stirrer, the reactants in the medium to be treated can be dispersed throughout the bioreactor under the stirring action of the magnetic stirrer, avoiding excessively high or low local concentrations and preventing local overheating or overcooling.

[0042] Optionally, in one embodiment of this application, the microplastics include at least one of the following: polyvinyl chloride, polypropylene, and polybutylene terephthalate; the particle size of the microplastics ranges from 0.12 to 0.15 mm.

[0043] There are various types of microplastics. Polyvinyl chloride (PVC) is a polymer formed by the free radical polymerization of vinyl chloride monomers under the initiator of peroxides, azo compounds, or under the influence of light and heat. Polypropylene (PP) is a semi-crystalline thermoplastic polymer made from propylene monomers through an addition polymerization reaction. Polybutylene terephthalate (PBAT) is a thermoplastic biodegradable plastic formed by the copolymerization of 1,4-butanediol, adipic acid, and terephthalic acid through a transesterification reaction. Furthermore, to further improve reaction efficiency, the particle size range of the microplastics in the treatment medium can be 0.12-0.15 mm.

[0044] Optionally, in one embodiment of this application, before step S13, which involves electrically stimulating the medium to be treated for a preset duration at a preset temperature, the method further includes: introducing nitrogen gas into the medium to be treated at an aeration rate of 3 L / min to enhance the activity of anaerobic microorganisms.

[0045] Nitrogen can significantly enhance microbial activity through physical action and microenvironment regulation. Aeration or stirring with nitrogen can generate bubbles and liquid flow, which can accelerate the diffusion of substances at the bottom of the medium being treated, promote the release of metabolic products from the inside, and improve reaction kinetics.

[0046] Optionally, in one embodiment of this application, the filter membrane used for filtration has a pore size ≤0.22μm; solid-liquid separation is achieved by centrifugation, with a centrifugation speed of 8000-10000 r / min and a centrifugation time ≥20 min. Centrifugation is fast and efficient, and the separation conditions can be precisely controlled by adjusting the speed and time. It can achieve solid-liquid separation of sludge suspension in the medium to be treated in a short time, and the sludge can be recycled and reused after separation and drying.

[0047] Specifically, this can be verified through Examples 1 and 2.

[0048] Example 1: In a system of electrically stimulated anaerobic microorganisms, the anode and cathode are set at a predetermined distance. The sludge was placed in a treatment medium containing polyethylene microplastics (PVC) and benzothiazole contaminants at a concentration of 50 mg / L, with 1 g of PVC added. The power supply voltage was set to 1.0 V, and persulfate electrolyte was added at a concentration of 1.0 g / L, along with necessary nutrients (4.10 mg / L CaCl2, 4.10 mg / L MgCl2, and 20.41 mg / L KH2PO4). The preset temperature for the electrostimulation reaction in the reactor was set to 35 °C. Artificially prepared water and pretreated sludge were mixed at a mass ratio of 5:1 to construct the start-up system, and nitrogen was introduced to maintain the anaerobic system. During the process, the treatment medium was continuously stirred at a stirring rate of 300 r / min using a magnetic stirrer. After a 60-day acclimatization period, the microorganisms in the system reached a stable active state. After acclimatization, the electrostimulation reaction was conducted in the system for a preset duration of 72 h, and then the supernatant was taken from the sampling port to determine the benzothiazole content. A control group was set up, in which no polyethylene microplastics (PVC) were added. For example... Figure 3 As shown, the results indicate that the degradation rate of benzothiazole reached approximately 99.8% in both the control group (without PVC microplastics) and the experimental group (with PVC microplastics). The results demonstrate that the electrostimulation synergistic effect of anaerobic microorganisms in this embodiment has a good removal effect on benzothiazole in mixed pollutants.

[0049] Example 2: In a system of electrically stimulated anaerobic microorganisms, the anode and cathode are set at a predetermined distance. The soil suspension containing polybutylene terephthalate (PBAT) and benzothiazole pollutants was placed in the treatment medium. The specific method of Example 2 was similar to that of Example 1. The reactor in Example 2 was also incubated at room temperature for 60 days, and the concentration of benzothiazole was 50 mg / L, with 1 g of microplastic PBAT added to the reactor. After acclimatization, the system was electrically stimulated for a preset duration of 96 h. Samples were then taken from the reactor sampling port to determine the benzothiazole content and analyze the particle size of the microplastic PBAT. Figure 3As shown, the degradation rate of benzothiazole reached 100% in the experimental groups with added microplastic PBAT. Furthermore, particle size analysis revealed that the particle size of the microplastic PBAT decreased to varying degrees. The experimental results of Examples 1 and 2 both effectively improved the treatment effect and efficiency of pollutants. It is evident that the anode of this application uses a carbon fiber brush electrode loaded with nano-zero-valent iron, which exhibits strong catalytic activity, high microbial adsorption capacity, and good stability. The reaction process requires no additional oxidant, produces no secondary pollution, has mild reaction conditions, low energy consumption, and is easy to operate. It achieves the synergistic treatment of microplastics and benzothiazole-like composite pollutants, capable of both pyrolyzing microplastics and oxidizing and decomposing organic pollutants, with high treatment efficiency. It is suitable for the remediation of different types of water and soil pollution and has broad application prospects.

[0050] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The directional terms mentioned in the embodiments of this application, such as "upper," "lower," "inner," and "outer," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the referred device or element must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of this application. "A plurality of" means at least two.

[0051] In the embodiments of this application, "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0052] References to "one embodiment" or "some embodiments" as used in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in another embodiment" appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0053] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0054] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for treating microplastics and benzothiazole pollutants by electrostimulation in conjunction with anaerobic microorganisms, characterized in that, include: The anode and cathode are placed at a preset distance in a medium to be treated containing microplastics and benzothiazole pollutants, wherein the medium to be treated also contains anaerobic microorganisms. An electrolyte is added to the medium to be treated and adjusted to a preset conductivity. The anode and cathode are connected to a DC power supply, and a preset voltage is applied to the medium to be treated to electrically stimulate the medium for a preset duration at a preset temperature.

2. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 1, characterized in that, The medium to be treated contains sludge, the sludge contains anaerobic microorganisms, and the liquid-to-solid ratio of the water in the medium to the sludge is (5-10):

1.

3. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 2, characterized in that, After the method involves electrically stimulating the medium to be treated at a preset temperature for a preset duration, the method further includes: The medium to be treated is allowed to stand and settle or filtered, and a quantitative sample is extracted from the medium at preset intervals to measure the concentration of microplastics and benzothiazole pollutants in the sample. The sludge suspension in the medium to be treated is subjected to solid-liquid separation, and then dried and recycled.

4. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 1, characterized in that, The anode is a carbon fiber brush electrode loaded with nano-zero valent iron, and the cathode is a graphite electrode.

5. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 1, characterized in that, The preset conductivity is 5-20 mS / cm, the electrolyte is persulfate, and the amount of electrolyte added is 0.5-2 g / L.

6. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 1, characterized in that, The preset distance between the anode and the cathode is 4-6 cm; the preset voltage is 0.8-1.2V; the preset temperature is 35±5℃; and the preset duration is 72-96 hours.

7. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 1, characterized in that, The preset duration of the electrical stimulation response of the medium to be treated at a preset temperature further includes: during the electrical stimulation response, the medium to be treated is continuously stirred at a stirring rate of 300±50 r / min using a magnetic stirrer.

8. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 1, characterized in that, The microplastics include at least one of the following: polyvinyl chloride, polypropylene, and polybutylene terephthalate; the particle size of the microplastics ranges from 0.12 to 0.15 mm.

9. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 1, characterized in that, Before the preset duration of the electrical stimulation response of the medium to be treated at a preset temperature, the method further includes: introducing nitrogen gas into the medium to be treated at an aeration rate of 3 L / min to enhance the activity of anaerobic microorganisms.

10. The method for treating microplastics and benzothiazole pollutants by electrostimulation synergistically with anaerobic microorganisms according to claim 3, characterized in that, The filter membrane used for filtration has a pore size ≤ 0.22 μm; the solid-liquid separation is performed by centrifugation, the centrifugation speed is 8000-10000 r / min, and the centrifugation time is ≥ 20 min.

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