Centrifugal filtration device and method for its use in chitosan flocculation separation

Abstract

The application discloses a centrifugal filtering device and an application method thereof in chitosan flocculation precipitation separation, relates to the technical field of chitosan flocculation precipitation separation, and comprises a centrifugal tube assembly and a filtering tube assembly, the filtering tube assembly is placed in the centrifugal tube assembly, a filtering element is arranged at the bottom of the filtering tube assembly, a through hole capable of communicating the inside of the filtering tube assembly with the outside of the filtering tube assembly is arranged on the filtering element, a solution to be treated is placed in the centrifugal tube assembly, and the centrifugal tube assembly is used for being placed on a centrifugal equipment; during centrifugal process, the filtering tube assembly is compressed downwards, and supernatant separated from the centrifugal tube assembly enters the filtering tube assembly through the through hole on the filtering element. The application can avoid the flocculation blockage problem, make the solid-liquid separation more thorough, reduce the flocculation washing frequency, and avoid causing solid quantity loss.

Description

Technical Field

[0001] This invention relates to the field of chitosan flocculent precipitation separation technology, and in particular to a centrifugal filtration device and its application method in chitosan flocculent precipitation separation. Background Technology

[0002] Many reaction products are flocculent precipitates. For example, in the process of preparing chitosan flocculent powder, chitosan powder needs to be dissolved in an acid solution and a strong alkali solution is added to make it alkaline to obtain flocculent precipitate. At this time, it is necessary to remove the salt and excess alkali generated by acid-base neutralization in the solution.

[0003] Traditional methods for removing chitosan flocculent precipitates involve vacuum filtration using filter paper followed by washing with deionized water to remove impurities. However, chitosan flocculent precipitates tend to deposit on the filter paper surface, quickly clogging the filter pores and preventing further filtration. Therefore, centrifugation is generally used to separate these flocculent precipitates. Chitosan flocculent precipitates contain a large amount of water, with a density similar to water. When centrifuged using traditional centrifuge tubes, it is difficult to form a clear supernatant; instead, a turbid liquid forms, resulting in unsatisfactory separation. Multiple washes are required to remove the generated salts and excess alkali, and the turbid supernatant leads to significant precipitate loss during liquid dispensing. Therefore, solid-liquid separation of chitosan flocculent precipitates has always been a challenging experimental problem. Summary of the Invention

[0004] The purpose of this invention is to provide a centrifugal filtration device and its application method in the separation of chitosan flocculent precipitates, so as to solve the problems existing in the prior art, avoid clogging of flocculents, make solid-liquid separation more thorough, reduce the number of times flocculents are washed, and avoid solid loss.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a centrifugal filtration device, including a centrifuge tube assembly and a filter tube assembly. The filter tube assembly is placed inside the centrifuge tube assembly, and a filter element is provided at the bottom of the filter tube assembly. The filter element has a through hole that connects the inside of the filter tube assembly with the outside of the filter tube assembly. The centrifuge tube assembly is used to hold a solution to be processed and is used to place on a centrifuge device. During centrifugation, the filter tube assembly is compressed downwards, and the supernatant separated in the centrifuge tube assembly enters the filter tube assembly through the through hole on the filter element.

[0007] Preferably, the centrifuge tube assembly includes a lower centrifuge tube body and an upper centrifuge tube body, and the upper end of the lower centrifuge tube body and the lower end of the upper centrifuge tube body can be detachably connected.

[0008] Preferably, the centrifuge tube assembly further includes an annular connector, the upper and lower ends of the outer wall of the annular connector are threaded, and the upper end of the lower body of the centrifuge tube and the lower end of the annular connector are connected by threads, and the lower end of the upper body of the centrifuge tube and the upper end of the annular connector are connected by threads.

[0009] Preferably, the liquid level of the solution to be treated contained in the centrifuge tube assembly does not exceed 2 / 3 of the height of the lower tube of the centrifuge tube.

[0010] Preferably, the lower centrifuge tube has an outer diameter of 29mm, an inner diameter of 26mm, and a height of 70mm; the annular connector has an inner diameter of 20mm, an outer diameter of 29mm, and a height of 10mm; and the upper centrifuge tube has an outer diameter of 29mm, an inner diameter of 26mm, and a height of 40mm.

[0011] Preferably, the filter tube assembly includes a filter tube body and a mesh annular cap, the filter tube body has openings at both ends, and the lower end of the filter tube body is detachably connected to the mesh annular cap, and the filter element is located on the inner bottom surface of the mesh annular cap.

[0012] Preferably, the mesh annular cap has a connecting hole in the middle, the lower end of the filter tube can extend into the connecting hole and be threaded to the inner wall of the connecting hole, and the filter element is located at the connecting hole.

[0013] Preferably, the outer diameter of the filter tube body is smaller than the inner diameter of the centrifuge tube assembly, and the outer wall of the mesh annular cap contacts the inner wall of the centrifuge tube assembly; the upper end of the filter tube body is provided with an outwardly extending limiting ring, and the lower end face of the limiting ring can contact and limit the annular connector of the centrifuge tube assembly; the outer diameter of the filter tube body is 20mm, the height is 40mm to 70mm, the bottom inner ring diameter of the filter tube body is 18mm, and the outer diameter is 20mm; the outer diameter of the mesh annular cap is 26mm, and the inner diameter is 20mm.

[0014] Preferably, the filter element is filter paper, and the diameter of the filter paper is larger than the inner diameter of the filter tube body. The filter paper is placed in the connection hole and pressed by the lower end of the filter tube body.

[0015] This invention also provides a method for applying the centrifugal filtration device based on any one of the above technical solutions in the separation of chitosan flocculent precipitates, comprising: dissolving chitosan powder in an acidic solution, and adding a strong alkali under stirring until the solution becomes weakly alkaline to obtain a chitosan flocculent precipitate stock solution; adding the chitosan flocculent precipitate stock solution into the lower tube of a centrifuge tube, allowing the filter tube body to pass through an annular connector, placing filter paper in a mesh annular cap, and then tightening the mesh annular cap to the filter tube body to obtain a filter tube assembly; placing the filter tube assembly into the lower tube of a centrifuge tube, and using the annular connector to connect the upper tube body and the lower tube of the centrifuge tube. The centrifuge tube assembly is obtained by connecting the tubes together. Then, the centrifuge tube assembly is connected to the filter tube assembly and placed in the centrifuge. Under the action of centrifugal force, the filter tube assembly is compressed downward. At the same time, the supernatant is filtered into the filter tube body. After centrifugation, the supernatant in the filter tube body is suctioned out with a suction device, and the ring connector is loosened to remove the filter tube assembly. Then, deionized water is added to the lower tube of the centrifuge tube and stirred to mix evenly. The filter tube assembly is then put into the lower tube of the centrifuge tube, the ring connector is connected to the lower tube of the centrifuge tube, and centrifugation continues. The above operation is repeated until the salt and alkali in the solution are completely removed.

[0016] The present invention achieves the following technical effects compared to the prior art:

[0017] The centrifugal filtration device and its application method in the separation of chitosan flocculent precipitate provided by this invention include a centrifuge tube assembly and a filter tube assembly. The filter tube assembly is placed inside the centrifuge tube assembly, and a filter element is provided at the bottom of the filter tube assembly. The filter element has a through hole that connects the inside and outside of the filter tube assembly, thereby filtration through the filter element. This ensures that the separated supernatant can enter the filter tube assembly, while the flocculent precipitate is blocked outside the filter tube assembly. The centrifuge tube assembly is used to hold the solution to be processed and is placed on a centrifuge device. During centrifugation, the filter tube assembly is compressed downwards, causing the supernatant separated in the centrifuge tube assembly to be released. The liquid enters the filter tube assembly through the through holes on the filter element, and then is centrifuged through the outer centrifuge tube assembly, resulting in a state where the solid content continuously decreases from bottom to top. The inner filter tube assembly uses centrifugal force to move the dilute solution to the concentrated solution, thus filtering the dilute solution. This avoids the problem of flocculent deposits clogging the filter paper in traditional vacuum filtration methods. Finally, the supernatant in the inner filter tube assembly is sucked out by a suction device, thereby separating the flocculent precipitate from the aqueous solution. This ensures a relatively thorough solid-liquid separation, reduces the number of times the flocculent is washed, and also prevents the flocculent solids in the upper liquid from being sucked away by the suction device, thus preventing solid loss. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the centrifugal filtration device in Example 1;

[0020] Figure 2 This is a schematic diagram of the centrifuge tube assembly in Example 1;

[0021] Figure 3 This is a schematic diagram of the structure of the lower tube of the centrifuge tube in Example 1;

[0022] Figure 4 This is a schematic diagram of the annular connector in Embodiment 1;

[0023] Figure 5 for Figure 4 Top view;

[0024] Figure 6 This is a schematic diagram of the structure of the upper tube of the centrifuge tube in Example 1;

[0025] Figure 7 This is a schematic diagram of the filter tube assembly in Example 1;

[0026] Figure 8 This is a schematic diagram of the filter tube body in Example 1;

[0027] Figure 9 This is a top view of the bottom end of the filter tube in Embodiment 1;

[0028] Figure 10 This is a top view of the mesh annular screw cap in Embodiment 1;

[0029] Figure 11 This is a schematic diagram of the centrifugal filtration device before centrifugation in Example 1;

[0030] Figure 12 This is a schematic diagram of the centrifugal filtration device after centrifugation in Example 1;

[0031] Figure 13 The graph shows the relationship between the number of washes and the acetate concentration in Application Example 1.

[0032] Figure 14 The graph shows the relationship between the number of washes and the chloride ion concentration in Example 2.

[0033] Figure 15The graph shows the relationship between the number of washes and the lactate concentration in Example 3.

[0034] Figure 16 This is a graph showing the relationship between the number of washes and the acetate concentration in the comparative examples;

[0035] In the diagram: 1-Centrifuge tube assembly, 11-Lower centrifuge tube body, 12-Annular connector, 13-Upper centrifuge tube body, 14-Abutting ring, 2-Filter tube assembly, 21-Filter tube body, 22-Mesh annular cap, 23-Limiting ring. Detailed Implementation

[0036] 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.

[0037] The purpose of this invention is to provide a centrifugal filtration device and its application method in the separation of chitosan flocculent precipitates, so as to solve the problems existing in the prior art, avoid clogging of flocculents, make solid-liquid separation more thorough, reduce the number of times flocculents are washed, and avoid solid loss.

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] like Figures 1-12As shown, this embodiment provides a centrifugal filtration device, including a centrifuge tube assembly 1 and a filter tube assembly 2. The filter tube assembly 2 is placed inside the centrifuge tube assembly 1, and a filter element is provided at the bottom of the filter tube assembly 2. The filter element has a through hole that connects the inside of the filter tube assembly 2 with the outside of the filter tube assembly 2, thereby filtering through the filter element to ensure that the separated supernatant can enter the filter tube assembly 2, while flocculent precipitate is blocked outside the filter tube assembly 2. The centrifuge tube assembly 1 is used to hold the solution to be processed and is used to place on a centrifuge device. During centrifugation, the filter tube assembly 2 is compressed downwards and the supernatant separated in the centrifuge tube assembly 1 passes through the centrifuge tube assembly 1. The solution enters the filter tube assembly 2 through the through-holes on the filter element, and then is centrifuged through the outer centrifuge tube assembly 1, resulting in a state where the solid content continuously decreases from bottom to top. Meanwhile, the inner filter tube assembly 2 uses centrifugal force to move the solution from dilute to concentrated, thus filtering the dilute solution. This avoids the problem of flocculent deposits clogging the filter paper in traditional vacuum filtration methods. Finally, the supernatant in the inner filter tube assembly 2 is sucked out by a suction device, thereby achieving the separation of flocculent precipitate from the aqueous solution. This ensures a more thorough solid-liquid separation, reduces the number of times flocculent material is washed, and also prevents the flocculent solids in the upper liquid from being sucked away by the suction device, resulting in solid loss.

[0041] Specifically, the centrifuge tube assembly 1 includes a lower centrifuge tube body 11 and an upper centrifuge tube body 13. The upper end of the lower centrifuge tube body 11 and the lower end of the upper centrifuge tube body 13 can be detachably connected, thereby facilitating installation and disassembly and improving efficiency.

[0042] The centrifuge tube assembly 1 also includes an annular connector 12. Both the upper and lower ends of the outer wall of the annular connector 12 are threaded. The upper end of the lower tube body 11 of the centrifuge tube and the lower end of the annular connector 12 are connected by threads, and the lower end of the upper tube body 13 of the centrifuge tube and the upper end of the annular connector 12 are connected by threads, resulting in good connection stability.

[0043] The liquid level of the solution to be processed contained in the centrifuge tube assembly 1 shall not exceed 2 / 3 of the height of the lower tube body 11 of the centrifuge tube, thereby preventing liquid overflow during centrifugation.

[0044] As a preferred embodiment, the lower centrifuge tube 11 has an outer diameter of 29mm, an inner diameter of 26mm, and a height of 70mm; the annular connector 12 has an inner diameter of 20mm, an outer diameter of 29mm, and a height of 10mm; the upper centrifuge tube 13 has an outer diameter of 29mm, an inner diameter of 26mm, and a height of 40mm; those skilled in the art can also make adaptive modifications to the above dimensions according to actual needs.

[0045] The filter tube assembly 2 includes a filter tube body 21 and a mesh annular cap 22. The filter tube body 21 has openings at both ends, and the lower end of the filter tube body 21 can be detachably connected to the mesh annular cap 22. The filter element is located on the inner bottom surface of the mesh annular cap 22, which facilitates the replacement of the filter element.

[0046] The mesh annular cap 22 has a connection hole in the middle. The lower end of the filter tube body 21 can extend into the connection hole and be connected to the inner wall of the connection hole by threads. The filter element is located at the connection hole, so that the filter element can be pressed together by the filter tube body 21 and the mesh annular cap 22 to provide a stable filtration function.

[0047] The outer diameter of the filter tube body 21 is smaller than the inner diameter of the centrifuge tube assembly 1, and the outer wall of the mesh annular cap 22 is in contact with the inner wall of the centrifuge tube assembly 1. A limiting ring 23 extending outward is provided at the upper end of the filter tube body 21, and the lower end face of the limiting ring 23 can contact and limit the annular connector 12 of the centrifuge tube assembly 1, thereby limiting the lowest position of the filter tube body 21 in the centrifuge tube assembly 1. Correspondingly, an abutment ring 14 is provided in the middle of the inner wall of the annular connector 12, which can limit the limiting ring 23. As a preferred embodiment, the outer diameter of the filter tube body 21 is 20mm, the height is 40mm to 70mm, the bottom inner ring diameter of the filter tube body 21 is 18mm, and the outer diameter is 20mm. The outer diameter of the mesh annular cap 22 is 26mm, and the inner diameter is 20mm. Those skilled in the art can also make adaptive modifications to the above dimensions according to actual needs.

[0048] The filter element is filter paper, and the diameter of the filter paper is larger than the inner diameter of the filter tube body 21. The filter paper is placed in the connection hole and pressed by the lower end of the filter tube body 21 to prevent the filter paper from shifting during centrifugal filtration.

[0049] In this embodiment, PP polypropylene can be used as the specific material for centrifuge tube assembly 1 and filter tube assembly 2.

[0050] Example 2

[0051] This embodiment provides a method for applying the centrifugal filtration device in Embodiment 1 to the separation of chitosan flocculent precipitate, comprising: dissolving chitosan powder in an acid solution of 0.05 mol / L to 0.15 mol / L (weak acid: acetic acid, hydrochloric acid, lactic acid), and adding a strong alkali (strong alkali: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate) while stirring until the solution is weakly alkaline, thereby obtaining a chitosan flocculent precipitate stock solution; adding the chitosan flocculent precipitate stock solution into the lower tube 11 of a centrifuge tube, ensuring that the liquid level does not exceed 2 / 3 of the lower tube 11; passing the filter tube 21 (the length of the filter tube 21 can be determined according to the expected solid mass) through the annular connector 12; placing filter paper in the mesh annular cap 22; and then tightening the mesh annular cap 22 and the filter tube 21 to obtain the filter tube assembly 2; placing the filter tube assembly 2 into the lower tube 11 of the centrifuge tube, and using the annular connector... 12. Connect the upper tube body 13 and the lower tube body 11 of the centrifuge tube to obtain centrifuge tube assembly 1. Then, connect centrifuge tube assembly 1 with filter tube assembly 2 and place them together in a centrifuge device for centrifugation. At this time, under the action of centrifugal force, filter tube assembly 2 is compressed downward. At the same time, the supernatant is filtered into the filter tube body 21. Since the amount of solids in the supernatant is small, this filtration method is less likely to clog the filter element. After centrifugation, use a suction device (such as a pipette) to suck out the supernatant in the filter tube body 21 and loosen the annular connector 12 (at this time, the annular connector 12 and the upper tube body 13 of the centrifuge tube can remain connected). Take out the filter tube assembly 2, then add deionized water to the lower tube body 11 of the centrifuge tube and stir to mix evenly. Then, put the filter tube assembly 2 into the lower tube body 11 of the centrifuge tube, connect the annular connector 12 and the lower tube body 11 of the centrifuge tube, and continue centrifugation. Repeat the above operation until the salt and alkali in the solution are completely removed.

[0052] Specific application examples of the centrifugal filtration device in Example 1:

[0053] Application Example 1

[0054] Weigh 0.100g of chitosan powder and add 10mL of 0.05mol / L acetic acid. Stir until completely dissolved, then add 0.05mol / L sodium hydroxide solution until the pH value of the solution is approximately 8. Let stand for at least 0.5 hours to obtain the chitosan flocculent precipitate stock solution. Add the chitosan flocculent precipitate stock solution to the lower tube 11 of a centrifuge tube. Pass the filter tube 21 (60mm high) through the annular connector 12. Place a suitable size filter paper in the mesh annular cap 22 and tighten the mesh annular cap 22 to the lower end of the filter tube 21 to obtain the filter tube assembly 2. Place the filter tube assembly 2 into the lower tube 11 of the centrifuge tube. Use the annular connector 12 to extract the filter tube. Connect the lower tube 11 and upper tube 13 of the centrifuge tube using the ring connector 12; centrifuge at 5000 rpm / min for 5 minutes; after centrifugation, use a pipette to remove the clear liquid from the filter tube 21, loosen the ring connector 12, remove the filter tube assembly 2, add 15 mL of deionized water to the lower tube 11 of the centrifuge tube, stir with a glass rod until well mixed, then put the filter tube assembly 2 back into the lower tube 11 of the centrifuge tube and continue centrifugation; repeat the above operation, and take the clear liquid from the filter tube 21 for HPLC analysis to detect acetate ions until they are completely removed. The results are shown in the figure. Figure 13 After freeze-drying the flocculent material, 0.091 g of chitosan flocculent powder was obtained.

[0055] Application Example 2

[0056] Weigh 0.100g of chitosan powder, add 10mL of 0.15mol / L hydrochloric acid, stir until completely dissolved, then add 0.15mol / L potassium hydroxide solution until the pH value of the solution is about 8, and let it stand for more than 0.5 hours to obtain the chitosan flocculent precipitate stock solution; add the chitosan flocculent precipitate stock solution into the lower tube 11 of a centrifuge tube, pass the filter tube 21 (height 60mm) through the annular connector 12, place a filter paper of appropriate size in the mesh annular cap 22, and tighten the mesh annular cap 22 to the lower end of the filter tube 21 to obtain the filter tube assembly 2, and place the filter tube assembly 2 into the lower tube 11 of the centrifuge tube; use the annular connector Connect connector 12 to the lower tube 11 and upper tube 13 of the centrifuge tube; place in a centrifuge and centrifuge at 5000 rpm / min for 5 minutes; after centrifugation, use a pipette to remove the clear liquid from the filter tube 21, loosen the ring connector 12, remove the filter tube assembly 2, add 15 mL of deionized water to the lower tube 11 of the centrifuge tube, stir with a glass rod to mix evenly, then put the filter tube assembly 2 back into the lower tube 11 of the centrifuge tube and continue centrifugation; repeat the above operation, take the clear liquid from the filter tube 21 and detect chloride ions by silver nitrate precipitation until complete removal, and the results are shown in the figure. Figure 14 After freeze-drying the flocculent material, 0.088 g of chitosan flocculent powder was obtained.

[0057] Application Example 3

[0058] Weigh 0.100g of chitosan powder, add 10mL of 0.10mol / L lactic acid, stir until completely dissolved, then add 0.05mol / L sodium carbonate solution until the pH of the solution is approximately 8, and let stand for at least 0.5 hours to obtain the chitosan flocculent precipitate stock solution; add the chitosan flocculent precipitate stock solution to the lower tube 11 of a centrifuge tube, pass the filter tube 21 (60mm high) through the annular connector 12, place a suitable size filter paper in the mesh annular cap 22, and tighten the mesh annular cap 22 to the lower end of the filter tube 21 to obtain the filter tube assembly 2, and place the filter tube assembly 2 into the lower tube 11 of the centrifuge tube; use the annular connector 12 to further dissolve the chitosan powder. Connector 12 connects the lower tube 11 and upper tube 13 of the centrifuge tube; place in a centrifuge and centrifuge at 5000 rpm / min for 5 minutes; after centrifugation, use a pipette to remove the clear liquid from the filter tube 21, loosen the ring connector 12, remove the filter tube assembly 2, add 15 mL of deionized water to the lower tube 11 of the centrifuge tube, stir with a glass rod to mix evenly, then put the filter tube assembly 2 back into the lower tube 11 of the centrifuge tube and continue centrifugation; repeat the above operation, take the clear liquid from the filter tube 21 and perform HPLC analysis to detect lactate ions until they are completely removed. The results are shown in the figure. Figure 15 After freeze-drying the flocculent material, 0.086 g of chitosan flocculent powder was obtained.

[0059] Comparative Examples

[0060] Weigh 0.100 g of chitosan powder, add 10 mL of 0.05 mol / L acetic acid, stir until completely dissolved, then add 0.05 mol / L sodium hydroxide solution until the pH of the solution is approximately 8, and let stand for at least 0.5 hours to obtain the original chitosan flocculent precipitate. Add the original chitosan flocculent precipitate to a conventional 50 mL centrifuge tube, centrifuge at 5000 rpm / min for 5 minutes. After centrifugation, aspirate the supernatant from the centrifuge tube with a pipette, add 15 mL of deionized water, stir with a glass rod to mix thoroughly, and continue centrifuging. Repeat the above operation, and use HPLC to detect acetate ions in the supernatant until they are completely removed. The results are shown in the figure. Figure 16 After freeze-drying the flocculent material, 0.065g of chitosan flocculent powder was obtained.

[0061] Using a control experiment as a comparative example, such as a reaction temperature of 20℃~50℃, test schemes for reaction temperatures outside the 20℃~50℃ range can be provided.

[0062] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A centrifugal filtration device, characterized in that: The system includes a centrifuge tube assembly and a filter tube assembly. The filter tube assembly is placed inside the centrifuge tube assembly, and a filter element is provided at the bottom of the filter tube assembly. The filter element has a through hole that connects the inside of the filter tube assembly to the outside of the filter tube assembly. The centrifuge tube assembly is used to hold the solution to be processed and is used to place on a centrifuge device. During centrifugation, the filter tube assembly is compressed downwards, and the supernatant separated in the centrifuge tube assembly enters the filter tube assembly through the through hole on the filter element. The centrifuge tube assembly includes a lower centrifuge tube body and an upper centrifuge tube body, and the upper end of the lower centrifuge tube body and the lower end of the upper centrifuge tube body are detachably connected. It also includes an annular connector, the upper and lower ends of which are threaded. The upper end of the lower centrifuge tube and the lower end of the annular connector are connected by threads, and the lower end of the upper centrifuge tube and the upper end of the annular connector are connected by threads. The filter tube assembly includes a filter tube body and a mesh annular cap. The filter tube body is open at both ends, and the lower end of the filter tube body is detachably connected to the mesh annular cap. The filter element is located on the inner bottom surface of the mesh annular cap. The mesh annular cap has a connecting hole in the middle. The lower end of the filter tube body can extend into the connecting hole and is connected to the inner wall of the connecting hole by threads. The filter element is located at the connecting hole.

2. The centrifugal filtration device according to claim 1, characterized in that: The liquid level of the solution to be treated contained in the centrifuge tube assembly shall not exceed 2 / 3 of the height of the lower tube of the centrifuge tube.

3. The centrifugal filtration device according to claim 1, characterized in that: The lower centrifuge tube has an outer diameter of 29mm, an inner diameter of 26mm, and a height of 70mm; the annular connector has an inner diameter of 20mm, an outer diameter of 29mm, and a height of 10mm; the upper centrifuge tube has an outer diameter of 29mm, an inner diameter of 26mm, and a height of 40mm.

4. The centrifugal filtration device according to claim 1, characterized in that: The outer diameter of the filter tube body is smaller than the inner diameter of the centrifuge tube assembly, and the outer wall of the mesh annular cap contacts the inner wall of the centrifuge tube assembly; the upper end of the filter tube body is provided with an outwardly extending limiting ring, and the lower end face of the limiting ring can contact and limit the annular connector of the centrifuge tube assembly; the outer diameter of the filter tube body is 20mm, the height is 40mm~70mm, the bottom inner ring diameter of the filter tube body is 18mm, and the outer diameter is 20mm; the outer diameter of the mesh annular cap is 26mm, and the inner diameter is 20mm.

5. The centrifugal filtration device according to claim 1, characterized in that: The filter element is filter paper, and the diameter of the filter paper is larger than the inner diameter of the filter tube body. The filter paper is placed in the connection hole and pressed by the lower end of the filter tube body.

6. A method for applying the centrifugal filtration device according to any one of claims 1-5 in the separation of chitosan flocculent precipitates, characterized in that: include: Chitosan powder was dissolved in an acidic solution, and a strong alkali was added while stirring until the solution became weakly alkaline, resulting in a chitosan flocculent precipitate. This precipitate was added to the lower body of a centrifuge tube, allowing the filter tube to pass through an annular connector. Filter paper was placed in a mesh annular cap, and the cap was then screwed tightly onto the filter tube to obtain a filter tube assembly. This assembly was placed into the lower body of the centrifuge tube, and the upper and lower bodies were connected using the annular connector to form the centrifuge tube assembly. Finally, the centrifuge tube assembly was connected to the filter tube. The components are placed together in a centrifuge. Under centrifugal force, the filter tube assembly is compressed downwards, and the supernatant is filtered into the filter tube body. After centrifugation, the supernatant in the filter tube body is suctioned out using a suction device, and the annular connector is loosened to remove the filter tube assembly. Then, deionized water is added to the lower tube of the centrifuge tube and stirred until well mixed. The filter tube assembly is then installed into the lower tube of the centrifuge tube, the annular connector is connected to the lower tube of the centrifuge tube, and centrifugation continues. The above operation is repeated until the salt and alkali in the solution are completely removed.

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