A solid-liquid separation device and method for recovering nanoparticles

Abstract

This invention discloses a solid-liquid separation device and method for recovering nanoparticles, comprising a raw material tank and a raw material pump connected in sequence. The solid-liquid separation device further includes: a primary disc membrane assembly including a first inlet and a first outlet, the first inlet being connected to the raw material pump, and the first outlet being connected in sequence to a concentrate tank and a delivery pump; a secondary rotating disc membrane assembly including an air inlet, a fourth inlet, a third outlet, a filter cake outlet, and a rotating shaft fixedly disposed at the center of the rotating disc membrane, the fourth inlet being connected to the delivery pump, the third outlet being used to connect to the third inlet of the concentrate tank, the air inlet being connected to an air pipe, and the filter cake outlet being used to connect to a filter cake recovery tank. This invention can achieve solid-liquid separation of nanoparticles and obtain a filter cake with high solid content.

Description

Technical Field

[0001] This invention relates to a solid-liquid separation device, and more particularly to a solid-liquid separation device and method for recovering nanoparticles. Background Technology

[0002] With advancements in technology, particle sizes are becoming increasingly ultra-fine. Large quantities of high-purity nanoparticles are produced through hydrometallurgical or chemical processes. These powder slurries often contain a significant amount of residual anions and cations, which, if not thoroughly cleaned, can affect their performance and applications. Therefore, solid-liquid separation is essential. In the field of nanoparticles, the solid-liquid separation process for powder particles is frequently encountered.

[0003] As particle size decreases, the theoretical minimum separation factor of centrifuges increases, making the separation of ultrafine powders increasingly difficult. Typical industrial centrifuges can only separate particles with diameters in the micrometer range. Furthermore, centrifugal separation is difficult to scale up, and centrifugal washing operations are complex, labor-intensive, and inefficient. Gravity sedimentation is the most economical solid-liquid separation method, but it is suitable for separating relatively large particles. Various filtration technologies using filter cloth as the filter medium suffer from limitations in their ability to retain nanoparticles, resulting in significant product loss. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a solid-liquid separation device and method for recovering nanoparticles. This device and method can achieve solid-liquid separation of nanoparticles and obtain filter cake with high solid content.

[0005] This invention is achieved through the following technical solution:

[0006] A solid-liquid separation device for recovering nanoparticles includes a raw material tank and a raw material pump connected in sequence. The solid-liquid separation device further includes:

[0007] A primary disc membrane module, which can remove impurities including water-soluble impurities, includes a first inlet and a first outlet. The first inlet is connected to the raw material pump, and the first outlet is sequentially connected to a concentrate tank and a delivery pump.

[0008] The secondary rotating disc membrane assembly removes soluble small molecules, organic matter, and inorganic ions from nanoparticles. It includes an air inlet, a fourth inlet, a third outlet, a filter cake outlet, and a rotating shaft fixed at one end of the rotating disc membrane. The fourth inlet is connected to the delivery pump, and the third outlet is connected to the third inlet of the concentrate tank to circulate and concentrate the nanoparticles until no clear liquid remains. The air inlet is connected to an air duct, and the filter cake outlet is connected to a filter cake recovery tank.

[0009] Furthermore, the primary disc membrane assembly also includes a first permeate outlet, which is connected to a first permeate recovery tank, which can recover the first permeate.

[0010] Furthermore, the secondary rotating disc membrane assembly also includes a water inlet and a filtrate outlet. The water inlet is used to connect to a water pipe, and the filtrate outlet is arranged perpendicularly to the water inlet and connected to a filtrate recovery tank, which can recover the filtrate.

[0011] Furthermore, the air inlet includes a first air inlet and a second air inlet arranged perpendicularly to each other. The first air inlet is used to connect to the air duct inside the membrane, and the second air inlet is used to connect to the air duct outside the membrane.

[0012] Furthermore, the water inlet includes a first water inlet and a second water inlet arranged in parallel with each other. The first water inlet is used to connect to the water injection pipe inside the membrane, and the second water inlet is used to connect to the water injection pipe outside the membrane.

[0013] Furthermore, the primary disc film assembly includes a disc film, the spacing between the disc films is set to 5-20mm, and the inner surface of the disc film is fixedly provided with 1-3 layers of first inner mesh with a total thickness of 0.5-2mm, and the outer surface is fixedly provided with a first outer mesh with a thickness of 0.5-5mm.

[0014] Furthermore, the shapes of the first inner grid and the first outer grid are selected from one of square, circle, triangle, and rhombus, and the apertures are all 0.1 to 50 mm.

[0015] Furthermore, the disc film includes a first layer and a second layer; the first layer is PET, and the thickness of the PET is 200-600 μm; the second layer is selected from PVDF, polysulfone, polyethersulfone, and polyamide, and the thickness of the second layer is 5-15 μm and the pore size is 0.1-100 nm.

[0016] Furthermore, the secondary rotating disc membrane assembly includes a disc flat membrane, the spacing between the disc flat membranes is set to 20-50mm, the inner surface of the disc flat membrane is fixedly provided with 1-3 layers of second inner mesh with a total thickness of 0.5-2mm, and the outer surface is fixedly provided with a second outer mesh with a thickness of 0.5-5mm. The shape of the second inner mesh and the second outer mesh is selected from one of square, circle, triangle, and rhombus, and the aperture of each is 0.1-50mm.

[0017] Furthermore, the disc-shaped sheet film includes a first layer and a second layer; the first layer is PET, and the thickness of the PET is 200-600 μm; the second layer is selected from PVDF, polysulfone, polyethersulfone, and polyamide, and the thickness of the second layer is 5-15 μm and the pore size is 0.1-100 nm.

[0018] Furthermore, the operating pressure of the raw material pump is 0.1 to 1 MPa, the operating pressure of the delivery pump is 0.1 to 1 MPa, and the rotation speed of the shaft is 50 to 500 rpm.

[0019] A solid-liquid separation method for recovering nanoparticles, the method comprising the following steps:

[0020] Step S1: Feed nanoparticles with a solid content of 0.5-20% and a particle size of 0.1-1000nm into the raw material tank for later use;

[0021] Step S2: The nanopowder from step S1 is pumped to the first-stage disc membrane assembly to remove impurities, including water-soluble impurities, to obtain a first permeate and a first residual liquid. The first permeate is clear liquid, and the first residual liquid is a concentrated liquid with a concentration ratio of not less than 3.

[0022] Step S3: The first filtrate obtained in step S2 is transported to the secondary rotating disc membrane assembly by a transfer pump, and then connected to the concentrate tank 4 for circulation and concentration until no clear liquid remains. This removes impurities such as soluble small molecules, organic matter and inorganic ions from the nanoparticles. Finally, air is introduced to purge the disc plate membrane to obtain a high solids content filter cake.

[0023] Furthermore, in step S2: the membrane surface flow rate is 0.1–2 m / s, and the operating temperature is room temperature.

[0024] Furthermore, step S3 also includes:

[0025] When the content of the second permeate in the secondary rotating disc membrane module decreases by more than 30%, the membrane needs to be cleaned. Water is injected from the outer surface of the membrane for 5–30 minutes, followed by water injection from the inner surface for another 5–30 minutes. The cleaning flow rate is 0.1–2 m / s.

[0026] Furthermore, the operating temperature of step S3 is room temperature, the air pressure is 0.2-0.6 MPa, and the water pressure is 0.2-0.6 MPa.

[0027] Compared with the prior art, the advantages of this invention are:

[0028] 1. The present invention uses a solid-liquid separation device that combines a primary disc membrane assembly and a secondary rotating disc membrane assembly. The interlayer spacing between the disc membrane and the disc flat plate membrane is relatively large, which makes it less likely for high solid content nanoparticles to clog, thus facilitating the liquid-solid separation of nanoparticles.

[0029] 2. The primary disc membrane of the present invention adopts a staggered arrangement of large circular cuts, which can generate better shear force on the membrane surface and prevent the formation of filter cake; the disc membrane surface is attached with a mesh to prevent the formation of dense filter cake.

[0030] 3. The secondary disc membrane of the present invention adopts a rotating method, which can continue to concentrate even at high solid content. The surface of the disc flat membrane is covered with a mesh to prevent the formation of a dense filter cake, reduce filtration resistance, and facilitate the subsequent removal of the filter cake. The filter cake is then easily removed by blowing air onto the disc flat membrane in both directions. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the solid-liquid separation device for recovering nanoparticles according to the present invention;

[0032] Figure 2 For the present invention Figure 1 Cross-sectional view of the intermediate-level disc diaphragm assembly;

[0033] Figure 3 For the present invention Figure 1 Partial cross-sectional view of the secondary rotating disc membrane assembly;

[0034] 1. Feed tank; 2. Feed pump; 3. First-stage disc membrane assembly; 30. First inlet; 31. First outlet; 32. First permeate outlet; 33. Disc membrane; 34. First inner mesh; 35. First outer mesh; 36. First permeate recovery tank; 4. Concentrate tank; 40. Second inlet; 42. Third inlet; 5. Transfer pump; 6. Second-stage rotating disc membrane assembly; 60. Air inlet; 610. First air inlet; 601. Second air inlet; 61. Water inlet; 610. First water inlet; 611. Second water inlet; 62. Fourth inlet; 63. Third outlet; 64. Filtrate outlet; 640. Filtrate recovery tank; 65. Filter cake outlet; 650. Filter cake recovery tank; 66. Rotating shaft; 67. Disc-flat membrane; 68. Second inner mesh; 69. Second outer mesh. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed description, in conjunction with embodiments, is provided to enable those skilled in the art to fully understand the technical content of this invention. It should be understood that the following embodiments are for further illustration of this invention and should not be construed as limiting the scope of protection of this invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description of this invention all fall within the scope of protection of this invention. The specific preparation method parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to limit themselves to the specific values ​​in the examples below.

[0036] like Figure 1 As shown, an embodiment of the present invention provides a solid-liquid separation device for recovering nanoparticles, comprising a raw material tank 1, a raw material pump 2, a concentrated liquid tank 4, a transfer pump 5, a primary disc membrane assembly 3, and a secondary disc membrane assembly 6 connected in sequence to each other.

[0037] The first-stage disc membrane module 3 includes a first inlet 30 and a first outlet 31. The first inlet 30 is connected to the raw material pump 2, which transports the nanoparticles from the raw material tank 1 to the first-stage disc membrane module 3. Impurities, including water-soluble impurities, are removed, resulting in a first permeate and a first residual solution. The first permeate flows into the first permeate recovery tank 36 through the first permeate outlet 32 ​​for recovery, and the first residual solution flows out through the first outlet 31. The first outlet 31 is connected to the second inlet 40 of the concentrate tank 4. The concentrate tank 4 is also connected to the transfer pump 5, which can transport the first residual solution to the second-stage rotating disc membrane module 6 for further filtration to remove soluble small molecules, organic matter, and inorganic ions from the nanoparticles.

[0038] The primary disc membrane assembly 3 also includes disc membranes 33, with a spacing of 5 to 20 mm between the disc membranes 33. One to three layers of first inner mesh 34 with a total thickness of 0.5 to 2 mm are fixedly disposed on the inner surface of the disc membrane 33, and a first outer mesh 35 with a thickness of 0.5 to 5 mm is fixedly disposed on the outer surface of the disc membrane 33 to prevent the formation of a dense filter cake on the membrane surface.

[0039] The disc film 33 of the present invention is in the shape of a large circle, and the circles of the disc film 33 are arranged in an alternating pattern.

[0040] The shapes of the first inner grid 34 and the first outer grid 35 are selected from one of square, circle, triangle and rhombus, and the apertures are both 0.1 to 50 mm.

[0041] The disc film 33 of the present invention includes a first layer and a second layer, wherein the first layer is PET and the thickness of the PET is 200-600 μm;

[0042] The second layer is selected from one of PVDF, polysulfone, polyethersulfone, and polyamide, with a thickness of 5–15 μm and a pore size of 0.1–100 nm.

[0043] The secondary rotating disc membrane module 6 includes an air inlet 60, a fourth inlet 62, a third outlet 63, a filter cake outlet 65, and a rotating shaft 66 fixedly installed at the center of the rotating disc membrane. The fourth inlet 62 is connected to the delivery pump 5. The third outlet 63 is used to connect to the third inlet 42 of the concentrate tank 4 to realize the circulation and concentration of nanoparticles to zero. The air inlet 60 is connected to an air pipe to introduce air into the secondary rotating disc membrane module 6. The filter cake outlet 65 is used to connect to the filter cake recovery tank 650 to store the concentrated high solids content filter cake.

[0044] The secondary rotating disc membrane module 6 also includes a water inlet 61 and a filtrate outlet 64. The water inlet 61 is used to connect to a water pipe to inject water into the secondary rotating disc membrane module 6 to clean the disc flat membrane 67. The filtrate outlet 64 is set perpendicular to the water inlet 61 and is connected to the filtrate recovery tank 640. The filtrate recovery tank 640 can recover the filtrate after cleaning the disc flat membrane 67.

[0045] The air inlet 60 includes a first air inlet 600 and a second air inlet 601 arranged perpendicularly to each other. The first air inlet 600 is used to connect to the air duct inside the membrane, and the second air inlet 601 is used to connect to the air duct outside the membrane.

[0046] The water inlet 61 includes a first water inlet 610 and a second water inlet 611 that are vertically arranged. The first water inlet 610 is used to connect to the water injection pipe inside the membrane, and the second water inlet 611 is used to connect to the water injection pipe outside the membrane.

[0047] The operating pressure of the raw material pump 2 is 0.1 to 1 MPa, the operating pressure of the transfer pump 5 is 0.1 to 1 MPa, and the rotation speed of the shaft is 50 to 500 rpm.

[0048] The secondary rotating disc membrane assembly 6 includes disc flat membranes 67, with a spacing of 20-50 mm between the disc flat membranes 67. One to three layers of second inner mesh 68 with a total thickness of 0.5-2 mm are fixedly disposed on the inner surface of the disc flat membrane 67, and a second outer mesh 69 with a thickness of 0.5-5 mm is fixedly disposed on the outer surface of the disc flat membrane 67 to prevent the formation of a dense filter cake on the membrane surface. The shape of the second inner mesh 68 and the second outer mesh 69 is selected from one of square, circle, triangle, and rhombus, and the pore size is 0.1-50 mm.

[0049] The disc flat film 67 of this invention is circular, and the upper part of the secondary rotating disc film assembly 6 is cylindrical, while the lower part is conical with an angle of 60 to 100 degrees.

[0050] The disc flat film 67 includes a first layer and a second layer. The first layer is PET, and the thickness of the PET is 200-600μm.

[0051] The second layer is selected from one of PVDF, polysulfone, polyethersulfone, and polyamide, with a thickness of 5–15 μm and a pore size of 0.1–100 nm.

[0052] A solid-liquid separation method for recovering nanoparticles, the method comprising the following steps:

[0053] Step S1: Feed nanoparticles with a solid content of 0.5-20% and a particle size of 0.1-1000nm into raw material tank 1 for later use;

[0054] Step S2: The nanopowder from step S1 is transported to the primary disc membrane module 3 via the raw material pump 2. The membrane surface flow rate is 0.1-2 m / s, and the operating temperature is room temperature. This process can remove impurities, including water-soluble impurities, to obtain the first permeate and the first residual liquid. The first permeate is clear liquid, and the first residual liquid is a concentrated liquid with a concentration ratio of not less than 3.

[0055] Step S3: The first permeate obtained in step S2 is transported to the secondary rotating disc membrane module 6 via the transfer pump 5. The operating temperature is room temperature, the air pressure is 0.2-0.6 MPa, and the water pressure is 0.2-0.6 MPa. It is then connected to the concentrate tank 4 for circulation and concentration until no clear liquid remains. This removes impurities such as soluble small molecules, organic matter, and inorganic ions from the nanoparticles. Air is then introduced to purge the disc flat membrane 67, resulting in a high-solids-content filter cake. When the content of the second permeate in the secondary rotating disc membrane module 6 decreases by more than 30%, the membrane needs to be cleaned. Water is injected from the outer surface of the membrane for 5-30 minutes, and then water is injected from the inner surface of the membrane for 5-30 minutes. The cleaning flow rate is 0.1-2 m / s.

[0056] The following specific embodiments are used to further illustrate and describe the concept of the present invention, but it does not mean that the present invention is limited to the specific solutions described below. Any specific value within the range described in the embodiments is feasible.

[0057] Example 1

[0058] Step S1: Raw materials: Alumina raw materials with a solid content of 10% and a powder particle size of 0.5-1nm, of which 50% of the powder particles have a particle size of less than 0.6nm, are sent to raw material tank 1 for later use.

[0059] Step S2: The nanopowder from step S1 is transported by the raw material pump 2 at a pressure of 0.3 MPa to a disc membrane 33 formed by a PET carrier with a thickness of 30 μm and a PVDF with a thickness of 5 μm and a pore size of 0.1 nm for filtration. This removes impurities, including water-soluble impurities, and yields a first permeate and a first residual liquid. The first permeate is a clear liquid, and the first residual liquid is a concentrated liquid with a concentration ratio of 5.

[0060] The spacing between the disc films 33 is set to 5mm. Both the inner and outer surfaces of the disc films 33 have a first inner grid 34 with a thickness of 1mm and a pore size of 0.1mm and a first outer grid 35 with a diameter of 0.1mm. The flow velocity on the film surface is 0.1m / s.

[0061] Step S3: The first permeate obtained in step S2 is pumped through pump 5 and introduced into a disc-plate membrane 67 formed by a PET carrier with a thickness of 5000 μm and a PVDF with a thickness of 5 μm and a pore size of 0.3 nm under a pressure of 0.2 MPa. The shaft rotation speed is 50 rpm. The third outlet 63 of the secondary rotating disc membrane assembly 6 is connected to the third inlet of the concentrate tank 4 for circulation and concentration until no clear liquid appears. Then, 0.2 MPa of air is introduced to purge the outer surface of the disc-plate membrane 67 for 10 minutes, and then purge the inner surface of the disc-plate membrane for 10 minutes to dislodge the filter cake. The solid content of the formed filter cake is 50%. When the permeate flow rate of the membrane decreases by more than 30%, the membrane is cleaned with water. 0.2 MPa of water is injected into the outer surface of the membrane for 10 minutes, and then 0.2 MPa of water is injected into the inner surface of the membrane for 10 minutes. The cleaning flow rate is 0.1 m / s.

[0062] The spacing between the disc flat film 67 is set to 20mm. The inner surface of the disc flat film 67 has a diamond-shaped second inner mesh 68 with a thickness of 1mm and a pore size of 10mm. The outer surface of the disc flat film 67 has a diamond-shaped second outer mesh 69 with a thickness of 1mm and a pore size of 10mm.

[0063] Example 2

[0064] Step S1: Raw material: Lithium titanate raw material with a solid content of 5%, the powder particle size is 0.5-2nm, and 50% of it is less than 1nm, and it is sent to raw material tank 1 for later use.

[0065] Step S2: The nanopowder from step S1 is transported by the raw material pump 2 at a pressure of 11 MPa to a disc membrane 33 formed by a PET carrier with a thickness of 500 μm and a PVDF with a thickness of 15 μm and a pore size of 0.5 nm for filtration. This removes impurities, including water-soluble impurities, and yields a first permeate and a first residual liquid. The first permeate is a clear liquid, and the first residual liquid is a concentrated liquid with a concentration ratio of 6.

[0066] The spacing between the disc films 33 is set to 20mm. Both the inner and outer surfaces of the disc films 33 have a layer of rhomboid first inner grid 34 with a thickness of 1mm and a pore size of 10mm and a second outer grid 35. The flow velocity on the film surface is 2m / s.

[0067] Step S3: The first permeate obtained in step S2 is pumped through pump 5 at 1 MPa to a disc-plate membrane 67 formed by a PET carrier with a thickness of 500 μm and a PVDF carrier with a thickness of 15 μm and a pore size of 0.5 nm for filtration. The shaft rotation speed is 500 rpm. The third outlet 63 of the secondary rotating disc membrane assembly 6 is connected to the third inlet of the concentrate tank 4 for circulation and concentration until no clear liquid appears. Then, 0.6 MPa of air is introduced to purge the outer surface of the disc-plate membrane 67 for 30 minutes, and then purge the inner surface of the disc-plate membrane 67 for 30 minutes to dislodge the filter cake. The solid content of the formed filter cake is 60%. When the permeate flow rate of the membrane decreases by more than 30%, the membrane is cleaned with water. 0.6 MPa of water is injected into the outer surface of the membrane for 10 minutes, and then 0.6 MPa of water is injected into the inner surface of the membrane for 10 minutes. The cleaning flow rate is 2 m / s.

[0068] The spacing between the disc flat film 67 is set to 50mm. The inner surface of the disc flat film 67 has two layers of diamond-shaped first inner mesh 68 with a total thickness of 1mm and a pore size of 10mm. The outer surface of the disc flat film 67 has a layer of square second outer mesh 69 with a thickness of 1mm and a pore size of 10mm.

[0069] It should be noted that the above preferred embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A solid-liquid separation device for recovering nanoparticles, comprising a raw material tank (1) and a raw material pump (2) connected in sequence, characterized in that, The solid-liquid separation device also includes: A primary disc membrane assembly (3) is provided, which can remove impurities including water-soluble impurities and includes a first inlet (30) and a first outlet (31). The first inlet (30) is connected to the raw material pump (2), and the first outlet (31) is connected in sequence to a concentrate tank (4) and a transfer pump (5). The secondary rotating disc membrane assembly (6) removes soluble small molecules, organic matter and inorganic ion impurities from nanoparticles and includes an air inlet (60), a fourth inlet (62), a third outlet (63), a filter cake outlet (65) and a rotating shaft (66) fixedly disposed at one end of the center of the rotating disc membrane. The fourth inlet (62) is connected to the delivery pump (5). The third outlet (63) is used to connect to the third inlet (42) of the concentrate tank (4) to realize the circulation and concentration of nanoparticles until no clear liquid is obtained. The air inlet (60) is used to connect to the air pipe. The filter cake outlet (65) is used to connect to the filter cake recovery tank (650).

2. The solid-liquid separation device for recovering nanopowders according to claim 1, characterized in that: The primary disc membrane assembly (3) further includes a first permeate outlet (32), which is connected to a first permeate recovery tank (36), which can recover the first permeate.

3. The solid-liquid separation device for recovering nanopowders according to claim 1, characterized in that: The secondary rotating disc membrane assembly (6) further includes a water inlet (61) and a filtrate outlet (64). The water inlet (61) is used to connect to a water pipe. The filtrate outlet (64) is arranged perpendicularly to the water inlet (61) and connected to a filtrate recovery tank (640). The filtrate recovery tank (640) can recover the filtrate.

4. The solid-liquid separation device for recovering nanopowders according to claim 1, characterized in that: The air inlet (60) includes a first air inlet (600) and a second air inlet (601) arranged perpendicularly to each other. The first air inlet (600) is used to connect the air duct inside the membrane, and the second air inlet (601) is used to connect the air duct outside the membrane.

5. The solid-liquid separation device for recovering nanopowders according to claim 3, characterized in that: The water inlet (61) includes a first water inlet (610) and a second water inlet (611) arranged in parallel with each other. The first water inlet (610) is used to connect the water injection pipe inside the membrane, and the second water inlet (611) is used to connect the water injection pipe outside the membrane.

6. The solid-liquid separation device for recovering nanopowders according to claim 1, characterized in that: The first-level disc film assembly (3) includes a disc film (33), the spacing between the disc films (33) is set to 5~20mm, the inner surface of the disc film (33) is fixedly provided with 1~3 layers of first inner mesh (34) with a total thickness of 0.5~2mm, and the outer surface is fixedly provided with a first outer mesh (35) with a thickness of 0.5~5mm. The shapes of the first inner grid (34) and the first outer grid (35) are selected from one of square, circle, triangle and rhombus, and the apertures are all 0.1~50mm; The disc film (33) includes a first layer and a second layer; The first layer is PET, and the thickness of the PET is 200~600μm; The second layer is selected from PVDF, polysulfone, polyethersulfone, and polyamide, and the thickness of the second layer is 5~15μm and the pore size is 0.1~100nm.

7. The solid-liquid separation device for recovering nanopowders according to claim 1, characterized in that: The secondary rotating disc film assembly (6) includes a disc flat film (67), the spacing between the disc flat films (67) is set to 20~50mm, the inner surface of the disc flat film (67) is fixedly provided with 1~3 layers of second inner mesh (68) with a total thickness of 0.5~2mm, and the outer surface is fixedly provided with a second outer mesh (69) with a thickness of 0.5~5mm. The shape of the second inner grid (68) and the second outer grid (69) is selected from one of square, circle, triangle and rhombus, and the aperture is 0.1~50mm; The disc flat film (67) includes a first layer and a second layer; The first layer is PET, and the thickness of the PET is 200~600μm; The second layer is selected from PVDF, polysulfone, polyethersulfone, and polyamide, and the thickness of the second layer is 5~15μm and the pore size is 0.1~100nm.

8. The solid-liquid separation device for recovering nanopowders according to claim 1, characterized in that: The operating pressure of the raw material pump (2) is 0.1~1MPa, the operating pressure of the conveying pump (5) is 0.1~1MPa, and the rotation speed of the shaft is 50~500rpm.

9. A solid-liquid separation method for recovering nanoparticles, characterized in that, The method includes the following steps: Step S1: Feed nanoparticles with a solid content of 0.5-20% and a particle size of 0.1-1000nm into the raw material tank (1) for later use; Step S2: The nanoparticles from step S1 are transported to the primary disc membrane assembly (3) via the raw material pump (2) to remove impurities, including water-soluble impurities, and to obtain the first permeate and the first residual liquid. The first permeate is clear liquid and the first residual liquid is a concentrated liquid with a concentration ratio of not less than 3. Step S3: The first filtrate obtained in step S2 is transported to the secondary rotating disc membrane group (6) by the transfer pump (5), and then connected to the concentrate tank (4) for circulation and concentration until there is no clear liquid. This removes soluble small molecules, organic matter and inorganic ion impurities in the nanoparticles. Finally, air is introduced to purge the disc flat membrane (67) to obtain a high solid content filter cake.

10. The solid-liquid separation method for recovering nanopowders according to claim 9, characterized in that: Step S2: The membrane surface flow rate is 0.1~2m / s, and the operating temperature is room temperature; Step S3 further includes: When the content of the second permeate in the secondary rotating disc membrane module (6) decreases by more than 30%, the membrane needs to be cleaned. Water is injected from the outer surface of the membrane for 5-30 minutes, and then water is injected from the inner surface of the membrane for 5-30 minutes. The cleaning flow rate is 0.1-2 m / s. The operating temperature of step S3 is room temperature, the air pressure is 0.2~0.6MPa, and the water pressure is 0.2~0.6MPa.

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