Filtering method in water-soluble plant crushed powder extraction process and application

Abstract

The invention belongs to the technical field of vaccine adjuvant extraction, and particularly relates to a filtering method and application in the extraction process of water-soluble plant broken powder. PVPP is added into the bark powder, and the mass ratio of the bark powder to the PVPP is 1: (0.5-3); adding purified water according to a ratio of 1: (15-40) based on the mass of the bark, and stirring and extracting for 1-5 hours; pouring into a 0.22 mu m filter cup, filtering under negative pressure, and collecting filtrate; and after draining, adding the same volume of purified water to wash a filter cake, and collecting filtrate. The filtering effect is good, the process period is greatly shortened, and the filtering cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of vaccine adjuvant extraction, and in particular relates to a filtering method and application in the process of extracting water-soluble plant crushed powder. Background Art

[0002] Water-soluble plant extracts, such as saponins, flavonoids, pectin, alkaloids and other substances, are extracted from different parts of plants, such as seeds, roots, stems and leaves, and have a variety of biological activities, including immunomodulatory, anti-inflammatory and hypoglycemic properties. They show inherent low immunogenicity and have the ability to effectively regulate innate and adaptive immune responses. For example, plant saponins can promote the growth and development of the body's immune organs through a variety of signaling pathways, regulate the activity of a variety of immune cells, increase the secretion of immune-related cytokines and antigen-specific antibodies, and thus play a role in immune activity. However, the chemical structure of plant saponins determines that they have certain hemolysis and cytotoxicity. With the development of science and technology, these shortcomings can be avoided or reduced through certain technical means.

[0003] For example, there are two main methods for extracting saponins, namely water extraction and organic solvent extraction. Water extraction: Add dry saponin powder to water, heat to boiling, keep boiling for a period of time to fully dissolve the saponin, then cool and filter to obtain a water extract of saponin. Organic solvent extraction: Add dry saponin powder to an appropriate amount of organic solvent, heat and stir to fully dissolve the saponin, then cool and filter to obtain an organic solvent extract of saponin. Due to the toxicity and volatility of organic solvents, there is also the technical problem of high cost of organic solvents.

[0004] The crudely extracted plant saponins contain a lot of solid particle impurities of uneven sizes, and cannot be directly filtered. The filtering methods for plant saponin liquid mainly include the following: ‌Centrifugal filtration‌: During the extraction process, the extract is centrifuged and filtered, and the filter residue is discarded to obtain the filtrate. It is suitable for preliminary filtration, simple to operate, and is a commonly used filtration method. However, this filtration method may not be able to completely remove all impurities, and after centrifugal filtration, it is necessary to go through pre-filtration and filtration to achieve the desired turbidity effect, that is, centrifugation + pre-filtration + microfiltration is required to obtain an extract with a turbidity of less than 5NTU. There are many steps, a long process time, and a high cost.

[0005] ‌Macroporous resin adsorption‌: Use macroporous adsorption resin to adsorb the concentrated extract to remove some impurities. The amount of resin used is usually a certain proportion of the amount of material. First, elute with a certain amount of water, then elute with 95% ethanol or other concentrations of ethanol, and collect the ethanol eluate‌. It can effectively remove some impurities, but requires subsequent elution steps.

[0006] Ultrafiltration separation: In the process of traditional Chinese medicine (TCM) manufacturing, ultrafiltration separation technology is used for clarification. Although ultrafiltration technology can effectively improve the stability and safety of the preparation quality, in a complex solution environment, the separation behavior of saponins is inconsistent with the membrane retention molecular weight, which may lead to poor separation effects. This may be related to the surface activity of saponins. After reaching the critical micelle concentration, they mostly exist in the form of colloidal particles and micelles with different molecular weights, interfering with the membrane separation effect. It is applicable to occasions where high-purity products are required, but may be greatly affected by the solution environment.

[0007] Inorganic ceramic membrane filtration: Inorganic ceramic membranes (such as zirconia membranes) are used for filtration. The membrane pore size is 0.05 - 0.2 μm, which can effectively remove impurities and obtain a purified saponin extract.

[0008] Each of the above filtration methods has technical problems: For example, 1., 2. The solid content in the extract is relatively high, and macroporous resin adsorption cannot be used, which is well known to those skilled in the art. 3. Before ultrafiltration, it is necessary to first perform sterilization filtration on the extract, and the solid content of the extraction material is relatively high, which is not applicable; 4. For inorganic ceramic membrane filtration, the solid content of the feed liquid is high and it is easy to be blocked, which is not applicable.

[0009] PVPP (crosslinked polyvinylpyrrolidone) is a crosslinked polymer that is insoluble in water, strong acids, strong bases, and general organic solvents and is formed by the polymerization of vinylpyrrolidone monomers under specific conditions. As an important high-molecular fine chemical product, PVPP has many excellent and unique properties and has been widely used in the fields of cosmetics, food, medicine, etc. The characteristic crosslinked polyvinylpyrrolidone (PVPP) can be regarded as being formed by physically or chemically crosslinking linear PVP molecular chains. Currently, it is used as an adsorbent and clarifying agent.

[0010] Chinese Patent CN111372604A records a saponin extraction, a crude aqueous extract of Quillaja saponaria Molina containing at least the QS-21 main peak and the 2018 component, where the ratio of the 2018 component / QS-21 main peak measured by UV absorbance at 214 nm ≤ 0.75, the method for obtaining such an extract and related aspects. This patent mentions adding PVPP, and its main purpose is to use the adsorption complexation of PVPP to remove some impurities in the extract. The steps of its examples are centrifuging the bark extract to obtain a crude extract, adding PVPP to complex the crude extract and then filtering, which has the technical problems of high cost and complex steps.

[0011] The specification of Chinese Patent CNCN105985400A describes a method for preparing active ingredients in camellia seeds, which includes first extracting the rich camellia seed oil in camellia seeds using safe and inexpensive organic solvents to obtain camellia seed cake meal; obtaining a crude extract of camellia saponin using aqueous ethanol, removing impurities with PVPP and acidic alumina, and then further obtaining total camellia saponin using macroporous strongly basic anion exchange resin. The present invention not only avoids the generation of caramel color during high-temperature pressing and the generation of an emulsified layer in the aqueous enzymatic method, but also through the macroporous strongly basic anion exchange resin, camellia saponin can be divided into saponins that can undergo ion exchange and those that are difficult to undergo ion exchange. The method provided by the present invention is simple and the technical route is feasible. In this patent, PVPP and acidic alumina are used for impurity removal treatment, and the complexation adsorption effect of PVPP and acidic alumina is utilized. Using PVPP and acidic alumina as adsorbents and complexing agents is a conventional technique well-known to those skilled in the art.

[0012] Regarding the technical problems existing in the filtration in the above two patents, first: both are two-step treatments, adding PVPP after obtaining the crude extract, which increases the process time; second: filtering by adding PVPP alone reduces the membrane flux and increases the usage amount of filters. Therefore, if the above two comparative patents want to achieve the same filtration effect as the present invention patent, they need to spend higher time and consumable costs. Summary of the Invention

[0013] To solve the above technical problems, the present invention provides a filtration method and application in the extraction process of water-soluble plant crushed powder substances. All steps are carried out at room temperature, filtering solid particulate matter to obtain a clear saponin extract. The filtration effect is good, and directly filtering after extraction at room temperature simplifies the filtration steps, greatly shortens the process cycle, shortens the filtration time, and greatly reduces the filtration cost; and in the present invention, the filter aid effect of PVPP under certain conditions is discovered, developing a new and broader application range for PVPP.

[0014] A filtration method in the extraction process of water-soluble plant crushed powder substances of the present invention for solving the above technical problems includes the following steps: (1) Crushing the bark; (2) Adding PVPP to the bark powder, by mass, the ratio of bark powder:PVPP is 1:0.5 - 3; (3) Adding purified water in a ratio of 1:15 - 40 based on the mass of the bark powder, stirring and extracting for 1 - 5 h; (4) Pouring into a 0.22 um filtration cup and filtering under negative pressure to collect the filtrate; (5) After drying the filter cake, adding the same volume of purified water to wash the filter cake and collecting the filtrate, thus obtaining.

[0015] In the optimization solution, the bark powder is a water-soluble plant crushed powder. The water-soluble plant extract includes substances such as saponins, flavonoids, pectin, and alkaloids; in the optimization solution, it is saponins.

[0016] In a further optimized solution, the bark powder is Quillaja saponaria bark powder, ginkgo leaf powder, and plane tree bark powder; in the optimized solution, the bark powder is Quillaja saponaria bark powder.

[0017] The particle size of the bark powder is 100 - 300 mesh.

[0018] The particle size of the bark powder is 150 - 300 mesh.

[0019] By mass, the bark powder: PVPP = 1:0.5, 1:1, 1:2, or 1:3.

[0020] In a further optimized solution, the bark powder: PVPP = 1:1.

[0021] The negative pressure in step (2) is 2000 - 4000 Pa.

[0022] In step (3), purified water is added in a ratio of 1:15, 1:20, 1:25, 1:30, 1:35, or 1:40.

[0023] In step (3), purified water is added in a ratio of 1:30.

[0024] In step (3), stir and extract for 4 h.

[0025] In step (5), after filtering and drying, add purified water of equal volume to rinse the filter cake 2 times or more and collect the filtrate.

[0026] The application of the method described in the present invention in the preparation of a filter aid, further, the application of PVPP in the preparation of a filter aid.

[0027] In the present invention, the mixture of water-absorbed PVPP and water-absorbed bark powder not only has the function of removing polyphenolic impurities, but also has a good filter aid effect. After the water-absorbed PVPP and bark powder are mixed evenly and precipitated, a filter cake is formed, which plays a filter aid role and helps in filtration.

[0028] In the filtration method of the present invention, PVPP is used for filtration aid. After the "PVPP + bark powder + water" is mixed in a certain ratio, fully absorbs water, is mixed evenly, and then stands to form a filter cake. Uneven gaps are formed between PVPP and the bark powder, through which the liquid can pass, while the solid particles will be intercepted, thus playing a filter aid role. In the present invention, PVPP not only has the function of adsorption and complexation but also has a filter aid function, while in other methods, only its adsorption and complexation function is used. It is found through retrieval that there is no other literature or patent before this patent that discovers PVPP can form a filter aid effect with substances such as bark powder.

[0029] Specifically, the reason for the formation of the filter aid by mixing PVPP and bark powder after water absorption: PVPP after water absorption alone has no filter aid effect, and bark powder after water absorption alone has no filter aid effect. After PVPP in the form of an irregular-shaped colloid after water absorption is mixed with bark powder, gaps of different sizes are formed between PVPP particles through the supporting effect of bark powder, and a filter cake is formed after precipitation layer by layer, thus playing a filter aid role.

[0030] The method in the present invention is simple to operate, simplifies the filtration steps, shortens the process cycle by more than 50%, and greatly reduces the filtration cost. It can be applied to water-soluble substances that need to be pulverized and extracted from water-soluble plants, and is mainly applicable to filtering the saponin solution extracted from plant saponins.

[0031] In the present invention, the turbidity before filtration > 40000 NTU, and the turbidity after filtration < 5 NTU.

[0032] The method in the present invention can be applied to the filtration during the extraction of plant crushed powder substances, and is more applicable to the filtration of plant saponin extracts. Detailed implementation mode

[0033] The following further elaborates on the present invention in combination with specific embodiments: Example 1 Take 10 g of crushed soap tree bark powder (particle size: 150 mesh), add 10 g of PVPP according to a ratio of 1:1, and add 300 ml of purified water according to a mass-volume ratio of bark powder and water of 1:30. After stirring and extracting for 4 h, pour it into a 0.22-μm cup filter for suction filtration, and collect 170 ml of filtrate. After calculation, the membrane flux is 135.35 L / m 2 . It can be seen that PVPP and bark powder have a good filter aid effect after water absorption and mixing. The effects of different raw material ratios vary greatly. Compared with the following control group 1, the filtration capacity of the filter is increased by 6 times or more, and compared with the following control group 6, the filtration capacity of the filter is increased by more than 5 times.

[0034] Example 2 Take 20 g of crushed soap tree bark powder (particle size: 150 mesh), add 10 g of PVPP according to a ratio of 2:1, and add 300 ml of purified water according to a mass-volume ratio of bark powder and water of 1:15. After stirring and extracting for 4 h, pour it into a 0.22-μm cup filter for suction filtration, and collect 110 ml of filtrate after rinsing. After calculation, the membrane flux is 87.58 L / m 2 .

[0035] Example 3 Take 10 g of pulverized Quillaja saponaria bark powder (particle size: 150 mesh), add 20 g of PVPP according to a ratio of 1:2, and add 300 ml of purified water according to a mass-volume ratio of bark powder to water of 1:30. After stirring and extracting for 4 h, pour it into a 0.22-μm cup filter for suction filtration. After rinsing, collect 126 ml of filtrate. The calculated membrane flux is 100.32 L / m 2 .

[0036] The above Examples 1, 2, and 3 illustrate that different addition ratios of PVPP and bark powder have a significant impact on the filter-aid effect.

[0037] Example 4 Take 10 g of pulverized Quillaja saponaria bark powder (particle size: 100 mesh), add 10 g of PVPP according to a ratio of 1:1, and add 300 ml of purified water according to a mass-volume ratio of bark powder to water of 1:30. After stirring and extracting for 4 h, pour it into a 0.22-μm cup filter for suction filtration. Collect 158 ml of filtrate. The calculated membrane flux is 125.8 L / m 2 .

[0038] Example 5 Take 10 g of pulverized Quillaja saponaria bark powder (particle size: 200 mesh), add 10 g of PVPP according to a ratio of 1:1, and add 300 ml of purified water according to a mass-volume ratio of bark powder to water of 1:30. After stirring and extracting for 4 h, pour it into a 0.22-μm cup filter for suction filtration. Collect 176 ml of filtrate. The calculated membrane flux is 140.13 L / m 2 .

[0039] Example 6 Take 10 g of pulverized Quillaja saponaria bark powder (particle size: 300 mesh), add 10 g of PVPP according to a ratio of 1:1, and add 300 ml of purified water according to a mass-volume ratio of bark powder to water of 1:30. After stirring and extracting for 4 h, pour it into a 0.22-μm cup filter for suction filtration. Collect 165 ml of filtrate. The calculated membrane flux is 137.17 L / m 2 .

[0040] The above Examples 1, 4, 5, and 6 illustrate that the mixing of PVPP and bark powder with different particle sizes after water absorption has a significant impact on the filter-aid effect.

[0041] Example 7 Take 10 g of pulverized Platanus orientalis bark powder (particle size: 200 mesh), add 10 g of PVPP according to a ratio of 1:1, and add 300 ml of purified water according to a mass-volume ratio of bark powder to water of 1:30. After stirring and extracting for 4 h, pour it into a 0.22-μm cup filter for suction filtration. Collect 165 ml of filtrate. The calculated membrane flux is 135.5 L / m 2 .

[0042] Example 8 Take 10 g of pulverized ginkgo leaf powder (particle size: 200 mesh), add 10 g of PVPP in a 1:1 ratio, and add 300 ml of purified water in a mass-to-volume ratio of bark powder to water of 1:30. Stir and extract for 4 h, then pour into a 0.22-μm cup filter for suction filtration. Collect 141 ml of filtrate. After calculation, the membrane flux is 115.79 L / m 2 .

[0043] The above Examples 5, 7 and 8 illustrate that the comparison of the filter aid effect of the mixture of PVPP and sycamore bark powder after water absorption has no obvious influence on the filter aid effect of the mixture of PVPP and bark powder after water absorption. The comparison of the filter aid effect of the mixture of PVPP and ginkgo leaf powder after water absorption has a weak influence on the filter aid effect of the mixture of PVPP and bark powder after water absorption, but still has a good filter aid effect.

[0044] Example 9 Take 100 g of pulverized soap tree bark powder, add 100 g of PVPP in a 1:1 ratio, and add 3000 ml of purified water in a mass-to-volume ratio of bark powder to water of 1:30. Stir and extract for 4 h, then pour into a 0.22-μm cup filter. Collect 2850 ml of filtrate. Add 500 ml of purified water to the filter cup again for suction filtration. After collecting 450 ml of filtrate, add 500 ml of purified water to the filter cup again for suction filtration. Collect 520 ml of filtrate. Combine the filtrates from the three suction filtrations to obtain the crude extraction filtrate.

[0045] The main purpose of filtration in the present invention is to remove solid particles to obtain a clarified liquid, combining centrifugation + pre-filtration + 0.22-μm filtration. In the above Control Groups 4-6 and Example 9, the dosages of each raw material were increased for filtration. In Example 9, compared with the following Control Group 4, the two steps of centrifugation and 2-μm pre-filtration were removed, and the same filtration effect was achieved. The clarity of the filtrate was almost the same as that in Control Group 4, both being less than 2 NTU.

[0046] Example 9 simplifies the steps, reduces the cost, and shortens the overall process time; compared with the following Control Group 5, Example 9 increases the filtration capacity of the filter by more than 6 times; compared with Control Group 6, Example 9 increases the filtration capacity of the filter by more than 7 times.

[0047] Example 10 Take 10 g of pulverized soap tree bark powder (particle size: 150 mesh), add 5 g of PVPP in a 1:0.5 ratio, and add 50 ml of purified water in a mass-to-volume ratio of bark powder to water of 1:20. Stir and extract for 1 h, then pour into a 0.22-μm cup filter for suction filtration.

[0048] Example 11 Take 10 g of crushed Quillaja saponaria bark powder (particle size: 150 mesh), add 30 g of PVPP in a ratio of 1:3, and add 100 ml of purified water in a ratio of 1:15 of the mass-volume ratio of bark powder to water. Stir and extract for 5 h, then pour into a 0.22-μm cup filter for suction filtration.

[0049] Example 12 Take 10 g of crushed Quillaja saponaria bark powder (particle size: 150 mesh), add 10 g of PVPP in a ratio of 1:1, and add 250 ml of purified water in a ratio of 1:25 of the mass-volume ratio of bark powder to water. Stir and extract for 4 h, then pour into a 0.22-μm cup filter for suction filtration.

[0050] Example 13 Take 10 g of crushed Quillaja saponaria bark powder (particle size: 250 mesh), add 20 g of PVPP in a ratio of 1:2, and add 350 ml of purified water in a ratio of 1:35 of the mass-volume ratio of bark powder to water. Stir and extract for 4 h, then pour into a 0.22-μm cup filter for suction filtration.

[0051] Example 14 Take 10 g of crushed Quillaja saponaria bark powder (particle size: 200 mesh), add 30 g of PVPP in a ratio of 1:3, and add 400 ml of purified water in a ratio of 1:40 of the mass-volume ratio of bark powder to water. Stir and extract for 4 h, then pour into a 0.22-μm cup filter for suction filtration.

[0052] In the present invention, the mixture of water-absorbed PVPP and water-absorbed bark powder not only has the function of removing polyphenolic impurities, but also has a good filter-aid effect. After the water-absorbed PVPP and bark powder are mixed evenly and precipitated, a filter cake is formed, which plays a filter-aid role and helps filtration.

[0053] Example 15 Take 10 g of crushed Quillaja saponaria bark powder (particle size: 200 mesh), add 50 g of PVPP in a ratio of 1:5, and add 400 ml of purified water in a ratio of 1:30 of the mass-volume ratio of bark powder to water. Stir and extract for 4 h, then pour into a 0.22-μm cup filter for suction filtration. In this example, the stirring is not smooth and the filtration is not good.

[0054] Control Group 1 Take 10 g of crushed Quillaja saponaria bark powder with a particle size of 150 mesh, add 300 ml of purified water in a ratio of 1:30 of the mass-volume ratio of bark powder to water. Stir and extract for 4 hours, then stir and mix evenly and pour into a 0.22-μm cup filter for suction filtration (filter membrane diameter 4 cm). The filter is blocked, and 28 ml of the supernatant is collected. After calculation, the membrane flux is 22.89 L / m 2 .

[0055] Control Group 2 Take 10 g of PVPP, add 300 ml of purified water according to the mass-volume ratio of PVPP to water of 1:30, stir and extract for 4 hours, then stir and mix evenly, pour into a 0.22-μm cup filter for suction filtration (filter membrane diameter 4 cm), and collect 31 ml of supernatant. After calculation, the membrane flux is 24.68 L / m 2 .

[0056] In the control group 2 of the present invention, the single PVPP does not have a filter-aid effect and will hinder filtration, seriously reducing the membrane flux of the filter, so a filter with a larger membrane area needs to be used, resulting in a substantial increase in the filtration cost. However, the present invention removes the centrifugation step, and uses the filter-aid effect after adding PVPP and bark powder in proportion to form a filter cake to improve the membrane flux of the filter, greatly reducing the use of the filter and significantly reducing the filtration cost.

[0057] Control group 3 Take 10 g of crushed soap tree bark powder (particle size: 200 mesh), add 10 g of PVPP according to the ratio of 1:1, and add 300 ml of purified water according to the mass-volume ratio of bark powder to water of 1:30, stir and extract for 4 h, then mix evenly and balance, and centrifuge (8000 r / min, 10 min). Take the supernatant and pour it into a 2-μm cup filter for suction filtration, collect 260 ml of filtrate, pour the filtrate into a 0.22-μm cup filter for suction filtration, and collect 200 ml of filtrate. After calculation, the membrane flux is 159.24 L / m 2 .

[0058] The above Example 5 and Control Group 3 illustrate that the filter-aid effect of the mixture of PVPP and bark powder with different particle sizes after water absorption and the effect of pre-filtration and re-filtration after centrifugation do not have a particularly large difference. However, the method in the present invention can save more than 50% of the time and more than 60% of the filtration cost.

[0059] Control group 4 Take 100 g of crushed soap tree bark powder, add 3000 ml of purified water according to the mass-volume ratio of bark powder to water of 1:30, stir and extract for 4 hours, then centrifuge (8000 g, 10 min) to collect 2816 ml of supernatant. Add 3000 ml of purified water to the centrifugal precipitate, stir and extract for 1 hour, then centrifuge (8000 g, 10 min) to collect 2995 ml of supernatant. After combining the supernatants collected from the two extractions, pass through a 2-μm filter, collect the filtered supernatant and pass it through a 0.22-μm cup filter. The filtrates collected twice are combined to obtain the crude extraction filtrate.

[0060] Control group 5 Take 100 g of crushed soap tree bark powder, add 3000 ml of purified water according to the mass-volume ratio of bark powder to water of 1:30, absorb and swell for 4 h, then transfer to a 0.22-μm cup filter, collect 465 ml of filtrate, and the filter is blocked.

[0061] Control group 6 Take 100 g of PVPP, add 3000 ml of purified water according to the mass - volume ratio of PVPP to water of 1:30, stir and extract for 4 h, then pour it into a 0.22 - um cup - type filter, and collect 375 ml of filtrate.

[0062] Experiment 1 Compare the costs of the centrifugation, pre - filtration, and filtration steps in Example 5, the method in Control Group 3, and the method in the comparative patent respectively. Example 5: Take 10 g of pulverized soap tree bark powder (particle size: 200 mesh), add 10 g of PVPP according to a ratio of 1:1, add 300 ml of purified water according to the mass - volume ratio of bark powder to water of 1:30, stir and extract for 4 hours, then pour it into a 0.22 - um cup - type filter for suction filtration, and collect 176 ml of filtrate. Control Group 3: Take 10 g of pulverized soap tree bark powder (particle size: 200 mesh), add 10 g of PVPP according to a ratio of 1:1, add 300 ml of purified water according to the mass - volume ratio of bark powder to water of 1:30, stir and extract for 4 h, mix and balance, then centrifuge (8000 r / min, 10 min), take the supernatant and pour it into a 2 - um cup - type filter for suction filtration, collect 260 ml of filtrate, and then pour the filtrate into a 0.22 - um cup - type filter for suction filtration.

[0063] Comparative patent method: The content in Chinese Patent CN111372604A.

[0064] Specifically, see the content in Table 1 below: Table 1 Comparison of time - consuming and cost of different extraction and filtration methods

[0065] (Note: The centrifugation cost is calculated as a total of 10 yuan for single - use of 10 min plus equipment depreciation. The pre - filtration and filtration are calculated at the filter purchase price of 15 yuan. The comparative patent method and the method in Example 9 process the same feed liquid. Referring to the number of filters used in the membrane flux of Example 2, it is 5.7, and it is calculated as 5.) It can be seen from Table 1 above that: Compared with the method in Control Group 3, the time - consuming of the method in Example 5 is reduced by 67%, and the consumable cost is reduced by more than 60%; compared with the method in the comparative patent, the time - consuming is reduced by 50%, and the consumable cost is reduced by more than 80%. The method in the present invention greatly reduces the cost of the filtration step after extraction. And in the production process of the comparative patent, nanofiltration or ultrafiltration or diafiltration all need to be carried out after filtration. Otherwise, it will greatly reduce the filtration flux and increase the production cost, and it is not feasible for large - scale production.

[0066] The explanations of relevant terms in the present invention are as follows: Filtration: Filtration is an operation in which, under the action of a driving force or other external force, the liquid (or gas) in a suspension (or a gas containing solid particles) passes through a medium, and the solid particles and other substances are intercepted by the filter medium, so as to separate the solid and other substances from the liquid (or gas).

[0067] Ultrafiltration: Ultrafiltration is one of the membrane separation technologies driven by pressure. Aimed at separating macromolecules from small molecules, the membrane pore size ranges from 20 to 1000 Å. The ultrafiltration membrane only allows the solvent (such as water molecules), inorganic salts and small molecule organic substances in the solution to pass through, while intercepting macromolecular substances such as suspended solids, colloids, proteins and microorganisms in the solution, so as to achieve the purpose of purification and separation.

[0068] Nanofiltration: Nanofiltration (NF) is used to separate substances with relatively small molecular weights, such as inorganic salts or small molecule organic substances such as glucose and sucrose, from the solvent. Nanofiltration is also called low-pressure reverse osmosis, which is a new field of membrane separation technology. Its separation performance is between reverse osmosis and ultrafiltration, allowing some inorganic salts and certain solvents to pass through the membrane, so as to achieve the separation effect.

[0069] Diafiltration: Diafiltration is not another membrane process or membrane operation. It is a design scheme adopted to achieve better purification or separation effects. Since a simple process cannot achieve the complete separation of macromolecules and low molecular weight solutes, and complete separation is often required in the biotechnology or pharmaceutical, food industry, and fine chemical industries, researchers have discovered an operation method in which the retained substances can be continuously diluted with a solvent (such as water) to gradually wash away the low molecular weight solutes completely, and this is called diafiltration. During the diafiltration operation, when the material to be treated passes through the membrane, due to the selective permeability of the membrane between the small molecule and macromolecule components in the material, the small molecules are continuously removed as they pass through the membrane with the solvent, improving the separation degree of the retained components and the permeated components, so as to achieve the purpose of purifying the material.

[0070] Adsorbent: An adsorbent is a solid substance that can effectively adsorb certain components from a gas or liquid. Adsorbents generally have the following characteristics: large specific surface area, suitable pore structure and surface structure; strong adsorption capacity for adsorbates; generally do not react chemically with adsorbates and media; easy to manufacture and regenerate; have good mechanical strength, etc. Adsorbents can be classified according to pore size, particle shape, chemical composition, surface polarity, etc., such as macroporous and microporous adsorbents, powdered, granular, and strip-shaped adsorbents, carbonaceous and oxide adsorbents, polar and non-polar adsorbents, etc.

[0071] Complexing agent: A complexing agent is a type of chemical that can form complexes with metal ions, thereby improving the chemical properties of metal ions in aqueous solutions. Complexing agents can play roles in many fields, such as industry, healthcare, environmental protection, etc. Their special molecular structures can interact with metal ions at the molecular level to form stable complexes. Complexing agents can be used in fields such as metal ion decontamination, water treatment, metal catalysis, fertilizers, cosmetics, and medicine. In the medical field, complexing agents can form stable complexes with metal ions and can be used to treat iron deficiency anemia, cardiovascular diseases, tumors, and infectious diseases, etc.

[0072] Filter aid: When a filter aid is added to the solution to be filtered, it can adsorb and aggregate fine solid particles, not only accelerating the filtration rate but also making it easier to clarify. In the processing of instant tea, diatomaceous earth, white clay, refined talc powder, etc. with different particle sizes are used as filter aids for the filtration of black tea extracts.

[0073] The above-mentioned embodiments / tests are merely examples given for clear illustration and are not limitations on the implementation modes. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation modes here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A filtering method in the process of extracting water-soluble plant powder, characterized in that: The following steps are involved: (1) Crushing bark; (2) Add PVPP to the bark powder, and the bark powder: PVPP = 1:0.5-3 by mass; (3) Add purified water at a ratio of 1:15-40 based on the weight of the bark, and stir to extract for 1-5 hours; (4) Pour into a 0.22um filter cup and collect the filtrate by negative pressure filtration; (5) After filtering, add an equal volume of purified water to rinse the filter cake and collect the filtrate.

2. The filtering method in the process of extracting water-soluble plant crushed powder according to claim 1, characterized in that: The bark powder is water-soluble plant bark powder.

3. The filtering method in the process of extracting water-soluble plant crushed powder according to claim 2, characterized in that: The bark powder is soap tree bark powder.

4. The filtering method in the process of extracting water-soluble plant crushed powder according to claim 1, characterized in that: The bark powder in step (1) has a particle size of 100-300 meshes.

5. The filtering method in the process of extracting water-soluble plant crushed powder according to claim 4, characterized in that: The bark powder has a particle size of 150-300 meshes.

6. The filtering method in the process of extracting water-soluble plant crushed powder according to claim 1, characterized in that: By mass, the bark powder:PVPP=1:0.5, 1:1, 1:2 and 1:

3.

7. The filtering method in the process of extracting water-soluble plant crushed powder according to claim 6, characterized in that: The bark powder:PVPP=1:

1.

8. The filtering method in the process of extracting water-soluble plant crushed powder according to claim 1, characterized in that: In the step (3), purified water is added in a ratio of 1:15, 1:20, 1:25, 1:30, 1:35 or 1:

40.

9. The filtering method in the process of extracting water-soluble plant crushed powder according to claim 8, characterized in that: In the step (3), purified water is added at a ratio of 1:

30.

10. The application of the method described in right 1 in preparing a filter aid is characterized in that: The PVPP is used in preparing a filter aid.

Images