Method for organic matter concentration and separation and synchronous freezing crystallization and salt separation of high-salt wastewater

Abstract

The present invention relates to the technical field of the utilization of waste salts as resources and freeze crystallization of waste salts, and in particular to a method for organic matter concentration and separation and synchronous freezing crystallization and salt separation of high-salt wastewater. The method can achieve treatment of salt-containing wastewater containing high-concentration organic matters and comprises: adding wastewater to a stabilizer in a hot molten state for pretreatment; then performing cooling concentration on the high-salt wastewater solution containing the stabilizer to obtain an organic concentrated solution, performing solvent-based extraction and rectification to obtain a dissolved stabilizer solution, and recovering the organic waste solution; performing cryogenic freezing treatment on the salt water, from which the organic matters have been removed, to form ice crystals and a concentrated solution; performing gradient freezing crystallization on the concentrated solution to form ice crystals and high-purity saturated salt water; and performing centrifugal drying treatment to prepare a pure salt. The beneficial effects are: the method can not only realize efficient removal of impurities from organic matters in waste salts, but also synchronously realize crystallization and salt separation of waste salts, and has the advantages of having simple treatment procedures and a short treatment cycle, being modularizable, etc.

Description

A method for organic matter concentration, separation, and simultaneous freeze-crystallization desalination in high-salt wastewater Technical Field

[0001] This invention relates to the fields of waste salt resource utilization and freeze crystallization technology, specifically a method for the concentration and separation of organic matter in high-salt wastewater and simultaneous freeze crystallization for salt separation. Background Technology

[0002] In the production processes of various industries such as chemical, pharmaceutical, petroleum, papermaking, dairy processing, and food canning, large amounts of high-salinity organic wastewater are generated. The COD concentration in this wastewater exceeds 5 g / L, and the salt content is higher than 1.5%, primarily consisting of sodium or potassium salts, including sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate. Conventional treatment of this high-salinity organic wastewater or waste liquid results in a large amount of complex waste salt containing organic matter, which falls under the category of hazardous waste, making it unusable and a critical technical challenge for the industry. While multi-effect evaporation technology can improve the salt separation efficiency in wastewater to some extent, its high investment cost and difficulty in improving salt recovery quality are significant issues. In recent years, the combination of membrane filtration and freeze crystallization technology has been considered an effective process for treating high-salinity wastewater; however, this combined process is susceptible to organic contamination, cumbersome to operate, and places high demands on the freeze crystallizer, leading to unsatisfactory salt separation results. Therefore, to address these problems, a method for organic matter concentration and separation combined with simultaneous freeze crystallization for high-salinity wastewater was designed. Summary of the Invention

[0003] The purpose of this invention is to provide a method for the concentration, separation, and simultaneous freezing and crystallization of organic matter in high-salt wastewater to solve the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] A method for concentrating, separating, and simultaneously freezing and crystallizing organic matter in high-salt wastewater includes the following steps:

[0006] S1: Add the organic high-salt wastewater to the hot-melted extraction stabilizer for mixing and pretreatment to obtain the organic high-salt wastewater pretreatment material;

[0007] S2: Pump the organic high-salt wastewater pretreatment material obtained in S1 into a low-temperature crystallization tank and stir to obtain organic concentrated crystals and high-salt water.

[0008] S3: The organic concentrated crystals obtained in S2 are thermally melted and purified using a combination of reverse extraction and distillation. The purified solvent is then recycled to the wastewater pretreatment unit for reuse, and the organic waste liquid is recovered.

[0009] S4: The high-salt water obtained in S2 is pumped into a low-temperature cryogenic crystallizer for a first low-temperature cryogenic crystallization to obtain a salt concentrate and secondary crystallized salt, and to produce pure ice crystals;

[0010] S5: Pump the salt concentrate obtained in S4 into a low-temperature cryogenic crystallizer for secondary low-temperature cryogenic crystallization to obtain secondary crystallized salt; perform post-processing on the primary crystallized salt and secondary crystallized salt to obtain pure salt.

[0011] More optimally: the organic high-salt wastewater in step S1 contains one or both of sodium sulfate or potassium sulfate, with a salt content of 1.5% to 10.0% and an initial COD concentration of 0.5 g / L to 4 g / L.

[0012] In a more optimized manner: the extraction stabilizer in step S1 is dimethyl sulfoxide (DMSO), and the volume ratio of the extraction stabilizer to wastewater is 1~5:200~300; the temperature of the hot melting in step S1 is 30~60℃.

[0013] In a more optimized manner: the temperature of the low-temperature crystallization tank in step S2 is 10~25℃; the speed of the pump in step S2 is 0.1L / min~5L / min; and the stirring speed in step S2 is 30~50r / min.

[0014] In a more optimized manner: the hot melting temperature in step S3 is 30~60℃; the reagent used for reverse extraction is N,N-dimethylformamide (DMF); the parameters of the distillation process in step S3 are: temperature 80~120℃, pressure -0.2~-0.1MPa.

[0015] In a more optimized manner: the low-temperature cryogenic crystallizer mentioned in step S4 is an OSLO horizontal continuous cooling crystallizer with the following parameters: the length of the external cooler is 80.00cm~150.00cm and the diameter is 10.00cm~35.00cm; the speed of the pump mentioned in step S4 is 0.1L / min~5L / min, and the material is driven by an axial flow circulating pump.

[0016] In a more optimized manner, the first-stage low-temperature freezing crystallization adopts a three-step gradient cooling process, the specific process being: the first step cooling to 10~20℃ at a rate of 5~10℃ / min; the second step cooling to -5~10℃ at a rate of 10~20℃ / min; and the third step cooling to -15~-5℃ at a rate of 2.0-5.0℃ / min.

[0017] In a more optimized manner: the secondary low-temperature freezing crystallization process described in step S5 is the same as the primary low-temperature freezing crystallization process.

[0018] In a more optimized manner, the post-processing process in step S5 is as follows: the primary and secondary crystallized salts are centrifuged at low temperature, washed with alcohol, and then vacuum dried at low temperature; the parameters of the low-temperature centrifugation are: temperature 0~5℃, centrifugation speed 500~3000r / min; the alcohol used for washing is methanol or ethanol; the parameters of the vacuum drying are: temperature -20~10℃, vacuum degree 20~100Pa, drying time 2~6h.

[0019] This invention is based on the low-temperature recrystallization characteristics of DMSO and DMF. By adding an extraction stabilizer to high-salt wastewater, the organic matter in the wastewater is concentrated and separated under low-temperature cooling conditions. The extraction stabilizer can be purified by reverse extraction and distillation processes and can be recycled for wastewater pretreatment. The collected high-salt water is subjected to gradient freeze crystallization in an OSLO horizontal continuous cooling crystallizer to remove residual stabilizer and generate salt concentrate and crystalline salt, while clean ice crystals (water) are discharged. Finally, the salt concentrate is subjected to secondary freeze crystallization and centrifugal drying to obtain high-purity salt. Beneficial effects

[0020] (1) This invention innovatively uses DMSO solvent to wash and extract organic matter in high-salt organic wastewater, which can effectively stabilize organic matter in DMSO medium; after cooling and crystallization, it can achieve efficient concentration of organic matter in wastewater. This process has high impurity removal efficiency for organic matter in wastewater, is simple to operate, and is easy to modularize.

[0021] (2) In the method described in this invention, the extraction stabilizer DMSO is back-extracted by DMF and then separated and recycled by distillation. This process has high organic matter removal efficiency and can save costs.

[0022] (3) In the method described in this invention, after the high brine is subjected to two-step gradient freezing crystallization treatment in the OSLO horizontal continuous cooling crystallizer, ice crystals (water) and crystallized salt and salt concentrate can be obtained respectively. This process has high wastewater treatment efficiency, low energy consumption and high cold energy utilization rate.

[0023] (4) In the method described in this invention, methanol or ethanol is used for alcohol washing and drying of the crystallized salt, which can improve the purity of the crystallized salt, and the dehydration efficiency is good, resulting in high purity of the salt obtained after drying. The purity of sodium sulfate is >80%; the purity of potassium sulfate is >85%. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0025] Figure 1 shows the process flow of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1: A method for organic matter concentration, separation, and simultaneous freeze-crystallization of high-salt wastewater: The initial contents of each component in the high-salt wastewater are shown in Table 1. The method includes the following steps:

[0028] S1: Add wastewater containing COD up to 0.5 g / L and sodium sulfate up to 1.5% to DMSO at 30℃ and mix and pretreat at a volume ratio of 1:200, stirring until homogeneous;

[0029] S2: The pretreated organic wastewater is pumped into a low-temperature crystallization tank at a pumping speed of 0.1L / min. The organic matter is concentrated and crystallized under stirring conditions of 30r / min, and the wastewater containing sodium sulfate is separated and collected.

[0030] S3: After the organic concentrated crystals collected in step S2 are melted at 30°C, DMSO is extracted by reverse extraction using DMF. Then, the DMSO is purified and separated by distillation at 80°C and a distillation pressure of -0.2MPa. The purified solvent is returned to the wastewater pretreatment unit for reuse. Finally, the remaining organic waste liquid is recovered.

[0031] S4: The sodium sulfate-containing wastewater collected in step S2 is pumped into an OSLO horizontal continuous cooling crystallizer at a pumping rate of 5 L / min. The cooler is 80 cm long and 10 cm in diameter. A three-step gradient cooling process is used to remove residual DMSO. The first step involves cooling at a rate of 5 °C / min to 10 °C; the second step involves cooling at a rate of 10 °C / min to -5 °C; and the third step involves cooling at a rate of 2.0 °C / min to -15 °C. A concentrated sodium sulfate solution and sodium sulfate crystals are prepared, and pure ice crystals (water) are produced.

[0032] S5: Pump the concentrated liquid collected in step S4 into a low-temperature cryogenic crystallizer for secondary low-temperature cryogenic crystallization. Centrifuge all sodium sulfate crystals at low temperature. After washing with ethanol, the sodium sulfate crystals are dried under vacuum at -20°C with a vacuum degree of 20 Pa for 2 hours to obtain pure sodium sulfate.

[0033] Example 2: A method for organic matter concentration, separation, and simultaneous freeze-crystallization of high-salt wastewater: The initial contents of each component in the high-salt wastewater are shown in Table 1. The method includes the following steps:

[0034] S1: Add wastewater containing COD up to 1.5 g / L and potassium sulfate up to 5% to DMSO at 30℃ and mix and pretreat at a volume ratio of 1:300, stirring until homogeneous;

[0035] S2: The pretreated organic wastewater is pumped into a low-temperature crystallization tank at a pumping speed of 5L / min. Under the stirring condition of 50r / min, the organic matter is concentrated and crystallized, and the wastewater containing potassium sulfate is separated and collected.

[0036] S3: After the organic concentrated crystals collected in step S2 are melted at 60°C, DMSO is extracted by reverse extraction using DMF. Then, the DMSO is purified and separated by distillation at 120°C and a distillation pressure of -0.2MPa. The purified solvent is returned to the wastewater pretreatment unit for reuse. Finally, the remaining organic waste liquid is recycled.

[0037] S4: The potassium sulfate-containing wastewater collected in step S2 is pumped into an OSLO horizontal continuous cooling crystallizer at a pumping rate of 0.1 L / min. The cooler is 150 cm long and 10 cm in diameter. A three-step gradient cooling process is used to remove residual DMSO. The first step involves cooling at a rate of 20 °C / min to 10 °C; the second step involves cooling at a rate of 10 °C / min to -5 °C; and the third step involves cooling at a rate of 2.0 °C / min to -15 °C. This process yields a concentrated potassium sulfate solution and potassium sulfate crystals, and produces pure ice crystals (water).

[0038] S5: Pump the concentrated liquid collected in step S4 into a low-temperature cryogenic crystallizer for secondary low-temperature cryogenic crystallization. Centrifuge all potassium sulfate crystals at low temperature. After washing with ethanol, the potassium sulfate crystals are dried under vacuum at -20°C with a vacuum degree of 100 Pa for 2 hours to obtain pure potassium sulfate.

[0039] Example 3: A method for organic matter concentration, separation, and simultaneous freeze-crystallization of high-salt wastewater: The initial contents of each component in the high-salt wastewater are shown in Table 1. The method includes the following steps:

[0040] S1: Add wastewater containing 4.0 g / L COD, 5% sodium sulfate, and 2.5% potassium sulfate to DMSO at 40℃ and mix and pretreat at a volume ratio of 1:100, stirring until homogeneous;

[0041] S2: The pretreated organic wastewater is pumped into a low-temperature crystallization tank at a pumping speed of 0.5L / min. Under the stirring condition of 30r / min, the organic matter is concentrated and crystallized, and the wastewater containing sodium sulfate and potassium sulfate is separated and collected.

[0042] S3: After the organic concentrated crystals collected in step S2 are melted at 40°C, DMSO is extracted by reverse extraction using DMF. Then, the DMSO is purified and separated by distillation at 80°C and a distillation pressure of -0.1MPa. The purified solvent is returned to the wastewater pretreatment unit for reuse. Finally, the remaining organic waste liquid is recycled.

[0043] S4: The wastewater containing potassium sulfate and sodium sulfate collected in step S2 is pumped into an OSLO horizontal continuous cooling crystallizer at a pumping rate of 0.5 L / min. The cooler is 80 cm long and 20 cm in diameter. A three-step gradient cooling process is used to remove residual DMSO. The first step is a cooling rate of 10 °C / min, cooling to 15 °C; the second step is a cooling rate of 15 °C / min, cooling to 0 °C; and the third step is a cooling rate of 5.0 °C / min, cooling to -5 °C. A concentrated solution of potassium sulfate and sodium sulfate and potassium sulfate and sodium sulfate crystals are prepared, and pure ice crystals (water) are produced.

[0044] S5: Pump the concentrated liquid collected in step S4 into a low-temperature cryogenic crystallizer for secondary low-temperature cryogenic crystallization. Centrifuge all potassium sulfate and sodium sulfate crystals at low temperature. After washing the crystals with ethanol, perform vacuum low-temperature drying at -20℃ with a vacuum degree of 60Pa. After drying for 2 hours, pure potassium sulfate and sodium sulfate salts are obtained.

[0045] Comparative Example 1: No extraction stabilizer DMSO was added, and no subsequent reverse extraction was performed. The rest was the same as in Example 3, as follows:

[0046] S1: Pre-treat wastewater containing COD up to 4.0 g / L, sodium sulfate 5%, and potassium sulfate 2.5%;

[0047] S2: The pretreated organic wastewater is pumped into a low-temperature crystallization tank at a pumping speed of 0.5L / min. Under the stirring condition of 30r / min, the organic matter is concentrated and crystallized, and the wastewater containing potassium sulfate and sodium sulfate is separated and collected.

[0048] S3: The wastewater containing potassium sulfate and sodium sulfate collected in step S2 is pumped into an OSLO horizontal continuous cooling crystallizer at a pumping rate of 0.5 L / min. The cooler is 80 cm long and 20 cm in diameter. A three-step gradient cooling process is used to remove residual DMSO. The first step is a cooling rate of 10 °C / min, cooling to 15 °C; the second step is a cooling rate of 15 °C / min, cooling to 0 °C; and the third step is a cooling rate of 5.0 °C / min, cooling to -5 °C. A concentrated solution of potassium sulfate and sodium sulfate and potassium sulfate and sodium sulfate crystals are prepared, and pure ice crystals (water) are produced.

[0049] S4: The concentrated liquid collected in step S3 is pumped into a low-temperature cryogenic crystallizer for secondary low-temperature cryogenic crystallization. All potassium sulfate and sodium sulfate crystals are centrifuged at low temperature. After washing with ethanol, the crystals are dried under vacuum at -20°C with a vacuum degree of 60 Pa for 2 hours to obtain pure potassium sulfate and sodium sulfate salts.

[0050] Comparative Example 2: A triple-effect evaporator was used for evaporation and concentration, followed by brine separation, which replaced low-temperature freezing crystallization. The rest of the process was the same as in Example 3, as detailed below:

[0051] S1: Add wastewater containing 4.0 g / L COD, 5% sodium sulfate, and 2.5% potassium sulfate to DMSO at 40℃ and mix and pretreat at a volume ratio of 1:100, stirring until homogeneous;

[0052] S2: The pretreated organic wastewater is pumped into a low-temperature crystallization tank at a pumping speed of 0.5L / min. Under the stirring condition of 30r / min, the organic matter is concentrated and crystallized, and the wastewater containing sodium sulfate and potassium sulfate is separated and collected.

[0053] S3: After the organic concentrated crystals collected in step S2 are melted at 40°C, DMSO is extracted by reverse extraction using DMF. Then, the DMSO is purified and separated by distillation at 80°C and a distillation pressure of -0.1MPa. The purified solvent is returned to the wastewater pretreatment unit for reuse. Finally, the remaining organic waste liquid is recycled.

[0054] S4: The wastewater containing potassium sulfate and sodium sulfate collected in step S2 is evaporated using a triple-effect evaporator at a temperature of 120°C to obtain the first steam and wastewater concentrate. The evaporation time is 5 hours. Then, the wastewater concentrate is evaporated at 160°C to obtain the second steam and residual liquid I. The total evaporation time is 5 hours. The residual liquid I is evaporated at 260°C to obtain the third steam and residual liquid II. The total evaporation time is 3 hours. The total pressure in the triple-effect evaporator evaporation process is 9 MPa. Potassium sulfate and sodium sulfate concentrates are obtained. Then, brine separation is performed to obtain potassium sulfate and sodium sulfate crystalline salts. The crystalline salts are washed with ethanol and then dried under vacuum at -20°C with a vacuum degree of 60 Pa for 2 hours to obtain pure potassium sulfate and sodium sulfate salts.

[0055] Example 1: Sodium sulfate wastewater 1.5% 0.5% Example 2: Potassium sulfate wastewater 5% 1.5% Example 3: Sodium sulfate-potassium sulfate wastewater Sodium sulfate 5%, potassium sulfate 2.5% 4. Comparative Example 4: Sodium sulfate-potassium sulfate wastewater Sodium sulfate 5%, potassium sulfate 2.5% 4. Comparative Example 5: Sodium sulfate-potassium sulfate wastewater Sodium sulfate 5%, potassium sulfate 2.5%

[0056] Table 1

[0057] Testing: The purity and COD concentration ratio of the pure salt obtained from the examples and comparative examples were calculated, and the following data were obtained:

[0058] Example Crystallized Salt Purity (%) COD Concentration Ratio (%) Example 1 >80% >80 Example 2 >85% >85 Example 3 Sodium Sulfate >90%, Potassium Sulfate >80% >83 Comparative Example 1 Sodium Sulfate >76%, Potassium Sulfate >70% >72 Comparative Example 2 Sodium Sulfate >78%, Potassium Sulfate >73% >76

[0059] Table 2

[0060] Conclusion: The methods in Examples 1-3 can achieve efficient concentration of over 80% of organic matter, while the purity of waste salt can reach over 80%. Comparative Example 1, compared to Example 3, did not add the extraction stabilizer DMSO, resulting in decreased performance. Comparative Example 2 used a multi-effect evaporator for evaporation and concentration, followed by brine separation, instead of low-temperature freezing crystallization. Compared to Example 3, this method was more complex, and both the concentration ratio of organic matter and the purity of the crystallized salt decreased. Therefore, the method described in this invention not only satisfies the requirements for the concentration and collection of organic matter in wastewater but also simultaneously achieves the separation and purification of salt in wastewater. Furthermore, this method exhibits high wastewater treatment efficiency, low energy consumption, and high cold energy utilization.

[0061] 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. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover 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 process, method, article, or apparatus.

[0062] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for concentrating, separating, and simultaneously freezing and crystallizing organic matter in high-salt wastewater, characterized in that: Includes the following steps: S1: Add the organic high-salt wastewater to the hot-melted extraction stabilizer for mixing and pretreatment to obtain the organic high-salt wastewater pretreatment material; S2: Pump the organic high-salt wastewater pretreatment material obtained in S1 into a low-temperature crystallization tank and stir to obtain organic concentrated crystals and high-salt water. S3: The organic concentrated crystals obtained in S2 are thermally melted, and the solvent is purified by a combination of reverse extraction and distillation. The purified solvent is then returned to the wastewater pretreatment unit for reuse. And recycle organic waste liquid; S4: The high-salt water obtained in S2 is pumped into a low-temperature cryogenic crystallizer for a first low-temperature cryogenic crystallization to obtain a salt concentrate and primary crystallized salt, and to produce pure ice crystals; the first low-temperature cryogenic crystallization adopts a three-step gradient cooling process, the specific process is as follows: the first step is to cool down to 10~20℃ at a rate of 5~10℃ / min; the second step is to cool down to -5~10℃ at a rate of 10~20℃ / min; the third step is to cool down to -15~-5℃ at a rate of 2.0-5.0℃ / min; S5: Pump the salt concentrate obtained in S4 into a low-temperature cryogenic crystallizer for secondary low-temperature cryogenic crystallization to obtain secondary crystallized salt; perform post-processing on the primary crystallized salt and secondary crystallized salt to obtain pure salt.

2. The method for concentrating, separating, and simultaneously freezing and crystallizing organic matter in high-salt wastewater according to claim 1, characterized in that: The organic high-salt wastewater mentioned in step S1 contains one or both of sodium sulfate or potassium sulfate, with a salt content of 1.5% to 10.0% and an initial COD concentration of 0.5 g / L to 4 g / L.

3. The method for organic matter concentration, separation, and simultaneous freeze-crystallization of high-salt wastewater according to claim 1, characterized in that: The extraction stabilizer in step S1 is dimethyl sulfoxide, and the volume ratio of the extraction stabilizer to wastewater is 1~5:200~300; the temperature of the hot melting in step S1 is 30~60℃.

4. The method for organic matter concentration, separation, and simultaneous freeze-crystallization of high-salt wastewater according to claim 1, characterized in that: The temperature of the low-temperature crystallization tank in step S2 is 10~25℃; the speed of the pump in step S2 is 0.1L / min~5L / min; the stirring speed in step S2 is 30~50r / min.

5. The method for organic matter concentration, separation, and simultaneous freeze-crystallization of high-salt wastewater according to claim 1, characterized in that: The hot melting temperature in step S3 is 30~60℃; the reagent used for reverse extraction is N,N-dimethylformamide; the parameters of the distillation process in step S3 are: temperature 80~120℃, pressure -0.2~-0.1MPa.

6. The method for concentrating, separating, and simultaneously freezing and crystallizing organic matter in high-salt wastewater according to claim 1, characterized in that: The low-temperature cryogenic crystallizer mentioned in step S4 is an OSLO horizontal continuous cooling crystallizer with the following parameters: the length of the external cooler is 80.00cm~150.00cm and the diameter is 10.00cm~35.00cm; the speed of the pump mentioned in step S4 is 0.1L / min~5L / min, and the material is driven by an axial flow circulating pump.

7. The method for organic matter concentration, separation, and simultaneous freeze-crystallization of high-salt wastewater according to claim 1, characterized in that: The secondary low-temperature freezing crystallization process described in step S5 is the same as the primary low-temperature freezing crystallization process.

8. The method for concentrating, separating, and simultaneously freezing and crystallizing organic matter in high-salt wastewater according to claim 1, characterized in that: The post-processing process described in step S5 is as follows: the primary and secondary crystallized salts are centrifuged at low temperature, washed with alcohol, and then vacuum dried at low temperature; the parameters of the low-temperature centrifugation are: temperature 0~5℃, centrifugation speed 500~3000r / min; the alcohol used for washing is methanol or ethanol; the parameters of the vacuum drying are: temperature -20~10℃, vacuum degree 20~100Pa, drying time 2~6h.

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