A surface-roughened porous hydrophilic separation membrane and a method for preparing the same

Abstract

The present application relates to a kind of porous hydrophilic separation membrane with rough surface and its preparation method, which comprises the preparation of casting solution, the prepared casting solution is heated to 30-60 ℃, uniformly coated on glass plate, form liquid film, the surface of liquid film is immersed in a layer of stainless steel grid with convex structure, and the liquid film after immersed stainless steel grid is placed in constant temperature and humidity environment, take down stainless steel grid, and continue to place the liquid film after taking down stainless steel grid in the constant temperature and humidity environment, get the separation membrane with concave-convex surface structure;Then, preparation of spraying liquid, and with separation membrane as receiving substrate, after electrostatic spraying of spraying liquid on the surface of substrate, the substrate is immersed into coagulation bath and coagulated into film, and after acid washing and washing, the product is obtained.The prepared separation membrane carries out the preparation process of porous membrane and the process of roughening membrane surface simultaneously, avoids the complicated operation of hydrophilic modification again, and simplifies the membrane preparation process.

Description

Technical Field

[0001] This invention relates to the field of separation membrane preparation technology, specifically to a porous hydrophilic separation membrane with a rough surface and its preparation method. Background Technology

[0002] With the rapid development of industrialization and urbanization in my country, people's demand for various resources has increased dramatically. Realizing the renewable use of water resources has become a key focus and hot topic in the work of governments and relevant environmental protection agencies around the world.

[0003] Compared to traditional chemical separation methods such as sieving, distillation, evaporation, extraction, and centrifugation, membrane separation technology, as a highly efficient and energy-saving new separation technology, combines the functions of separation, concentration, purification, and refining, and has become one of the most important means of water resource regeneration today. The key component of membrane separation technology is the separation membrane. According to separation size, separation membranes include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. Among them, microfiltration and ultrafiltration membranes are typical porous membranes and are currently the most widely used separation membrane types in the water treatment field. Based on the hydrophilicity or hydrophobicity of the membrane material, ultrafiltration membranes can be divided into hydrophilic ultrafiltration membranes and hydrophobic ultrafiltration membranes. Strongly hydrophilic separation membranes are beneficial for increasing water permeate flux and reducing membrane fouling, which is also one of the current development focuses of hydrophilic separation membrane technology.

[0004] Chinese patent document CN202011164302.4 describes a modification of existing separation membranes by composited polydopamine / graphene oxide layers onto a polyvinylidene fluoride (PVDF) membrane. This involves uniformly arranging large areas of hydrophilic and antifouling graphene oxide on the membrane surface, thus modifying the existing membrane. Through dopamine polymerization, graphene oxide and hydrophilic dopamine are directly fixed to the PVDF membrane surface. Because dopamine contains numerous hydrophilic groups such as amino groups, it prevents graphene oxide particle aggregation, increases membrane hydrophilicity, and exhibits strong adhesion to the membrane material, solving the problem of graphene oxide easily detaching during use. The hydrophilic composite membrane involved in this patent is obtained using a dip-coating heat-setting method, and is specifically designed for hydrophilizing polyvinylidene fluoride membranes, making the preparation process relatively complex.

[0005] Chinese patent document CN201710396109.5 describes the preparation of a high-efficiency hydrophilic modified antifouling polyethersulfone (PES) membrane. This membrane is prepared through two steps: physical blending and chemical grafting hydrophilic modification of a pure PES membrane. A hydrophilic block polymer is introduced to introduce the PES membrane, which has broad application prospects in oil-water separation. This patent relates to a membrane preparation method involving blending modification and chemical grafting hydrophilic modification, which is relatively complex and specifically targets the hydrophilic modification of PES membranes. Summary of the Invention

[0006] This invention provides a porous hydrophilic separation membrane with a rough surface and a method for preparing the same, in order to solve the above-mentioned problems.

[0007] The technical solution adopted in this invention is as follows: Firstly, this invention provides a method for preparing a porous hydrophilic separation membrane with a rough surface, the method comprising at least the following steps:

[0008] S1: Preparation of casting solution: After mixing the pore-forming agent and solvent, add the hydrophilic polymer while stirring, and stir to dissolve at a certain temperature to form a transparent viscous solution. Vacuum degassing for 6-48 hours yields the casting solution.

[0009] S2: Evaporation phase separation to form a film. The casting solution obtained in step S1 is heated to 30-60℃ and uniformly coated onto a glass plate to form a liquid film. A stainless steel mesh with a raised surface is immersed in the surface of the liquid film. The liquid film after immersion in the stainless steel mesh is placed in a constant temperature and humidity environment for 3-36 hours. Then, the stainless steel mesh is removed, and the liquid film after removing the stainless steel mesh is placed in the constant temperature and humidity environment for 3-36 hours before being taken out to obtain a separation membrane with a concave and convex surface structure.

[0010] S3: To prepare the spraying liquid, mix the pore-forming agent and solvent, stir and add the hydrophilic polymer, and stir to dissolve at a certain temperature to form a transparent viscous solution. Vacuum degassing yields the spraying liquid.

[0011] S4: Prepare a rough surface by electrostatic spraying. Using the separation membrane with an uneven surface structure obtained in step S2 as the receiving substrate, after electrostatic spraying the coating liquid on the substrate surface, immerse the substrate in a coagulation bath for 6-12 hours to solidify into a film. After acid washing, rinse with pure water to obtain a porous hydrophilic separation membrane with a rough surface.

[0012] Preferably, the mass fractions of each component in the casting solution are: 6-25 parts of hydrophilic polymer, 2-12 parts of pore-forming agent, and 63-92 parts of solvent; the mass fractions of each component in the spraying solution are: 4-20 parts of hydrophilic polymer, 1-12 parts of pore-forming agent, and 70-95 parts of solvent.

[0013] Preferably, the hydrophilic polymer used in the preparation of the casting solution and the spraying solution is at least one of polyethersulfone, polysulfone, polyamide, polyvinyl chloride and its copolymers, polyvinylidene fluoride and its copolymers, polyimide, polycarbonate, polyacrylate, and polytetrafluoroethylene.

[0014] Preferably, the pore-forming agent used in the preparation of the casting solution and the spraying solution comprises the following components by weight: 1-10 parts polymer, 0.1-1 parts inorganic matter, and 0.1-1 parts nano solid gas generator, wherein the polymer is selected from at least one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol; the inorganic matter is selected from at least one of lithium chloride, zinc chloride, acetone, organoframe metal compounds, and pure water; and the nano solid gas generator is at least one of calcium carbonate, barium carbonate, nano copper powder, or nano zinc powder.

[0015] Preferably, the solvent used in the preparation of the casting solution and the spraying solution is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide, acetone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, benzene, and toluene;

[0016] In step S4, the DC voltage for electrostatic spraying is 10-30kV, the receiving distance is 5-25cm, and the basic spraying rate is 1-5ml / h.

[0017] Preferably, the coagulation bath in step S4 is pure water or a mixed solution, wherein the mixed solution includes pure water and the solvent, and the mass ratio of the solvent is 5-45 wt%.

[0018] Preferably, the mesh diameter of the stainless steel mesh is 3-10 μm; the constant temperature and humidity environment in step S2 is a temperature of 30-80℃ and a relative humidity of 50-100%.

[0019] Preferably, the pickling in step S4 involves soaking in dilute hydrochloric acid or dilute nitric acid with a concentration of 0.1-1 mol / L for 4-12 hours.

[0020] Preferably, the stainless steel mesh is woven from metal material, and the mesh diameter of the stainless steel mesh is 3-10μm.

[0021] Secondly, the present invention provides a porous hydrophilic separation membrane with a rough surface, which is prepared by the above-mentioned preparation method and is used as an ultrafiltration membrane or microfiltration membrane in water treatment.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The separation membrane surface prepared by the present invention has a special stepped rough structure, namely, the millimeter-level uneven structure formed by the millimeter-level grid, the micrometer-level protrusion structure formed by electrostatic spraying, and the nanometer-level pores in the protrusion structure formed during the acid washing process. The interaction between these rough structures makes the separation membrane exhibit superhydrophilic properties, and the membrane surface contact angle is less than 30°.

[0024] (2) The separation membrane prepared by the present invention carries out the preparation process of the porous membrane and the roughening process of the membrane surface at the same time, avoiding the complicated operation of chemical or physical hydrophilic modification after the preparation of the porous membrane in the conventional process, simplifying the membrane preparation process and making it easy to operate.

[0025] (3) The mesh diameter and concave-convex points of the stainless steel mesh can be adjusted and optimized as needed. The micron-level protrusion structure formed by the electrostatic spraying process can be adjusted, and the size of the nano-level pores in the protrusion structure can be adjusted by adjusting the pickling process, etc., so that each structure on the surface of the separation membrane can be adjusted, and the hydrophilicity of the separation membrane can be controlled.

[0026] (4) The rough structure on the surface of the separation membrane is composed of recessed grids and protruding porous micron particles. The structure is firmly bonded, which makes the separation membrane structure stable and has a long service life. It can be used as an ultrafiltration membrane or microfiltration membrane in water treatment. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope image of the porous hydrophilic separation membrane with a rough surface prepared in Example 5 of the present invention;

[0028] Figure 2 The surface water contact angle is the rough porous hydrophilic separation membrane prepared in Example 5 of the present invention. Detailed Implementation

[0029] To better illustrate the present invention, it will now be further described in conjunction with examples.

[0030] In a first aspect, the present invention provides a method for preparing a porous hydrophilic separation membrane with a rough surface, the method comprising at least the following steps:

[0031] S1: Preparation of casting solution: After mixing the pore-forming agent and solvent, add the hydrophilic polymer while stirring, and stir to dissolve at a certain temperature to form a transparent viscous solution. Vacuum degassing for 6-48 hours yields the casting solution.

[0032] S2: Evaporation phase separation and film formation. The casting solution obtained in step S1 is heated to 30-60℃ and uniformly coated onto a glass plate to form a liquid film. A layer of stainless steel mesh with a raised surface is immersed in the surface of the liquid film. The structure of the stainless steel mesh is not specifically limited, and its uneven surface can achieve its function. The liquid film after being immersed in the stainless steel mesh is placed in a constant temperature and humidity environment for 3-36 hours. Then, the stainless steel mesh is removed, and the liquid film after removing the stainless steel mesh is placed in the constant temperature and humidity environment for 3-36 hours before being taken out to obtain a separation membrane with an uneven surface structure.

[0033] S3: To prepare the spraying liquid, mix the pore-forming agent and solvent, stir and add the hydrophilic polymer, and stir to dissolve at a certain temperature to form a transparent viscous solution. Vacuum degassing yields the spraying liquid.

[0034] S4: Prepare a rough surface by electrostatic spraying. Using the separation membrane with an uneven surface structure obtained in step S2 as the receiving substrate, after electrostatic spraying the coating liquid on the substrate surface, immerse the substrate in a coagulation bath for 6-12 hours to solidify into a film. After acid washing, rinse with pure water to obtain a porous hydrophilic separation membrane with a rough surface. Acid washing causes the nano solid gas generator in the pore-forming agent to generate gas, thereby forming nanoscale pores on the membrane surface.

[0035] Preferably, the mass fractions of each component in the casting solution are: 6-25 parts of hydrophilic polymer, 2-12 parts of pore-forming agent, and 63-92 parts of solvent; the mass fractions of each component in the spraying solution are: 4-20 parts of hydrophilic polymer, 1-12 parts of pore-forming agent, and 70-95 parts of solvent.

[0036] Preferably, the hydrophilic polymer used in the preparation of the casting solution and the spraying solution is at least one of polyethersulfone, polysulfone, polyamide, polyvinyl chloride and its copolymers, polyvinylidene fluoride and its copolymers, polyimide, polycarbonate, polyacrylate, and polytetrafluoroethylene.

[0037] Preferably, the pore-forming agent used in the preparation of the casting solution and the spraying solution comprises, by weight, the following components: 1-10 parts polymer, 0.1-1 parts inorganic matter, and 0.1-1 parts nano-solid gas generator, wherein the polymer is selected from at least one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol; the inorganic matter is selected from at least one of lithium chloride, zinc chloride, acetone, organometallic compounds, and pure water; and the nano-solid gas generator is at least one of calcium carbonate, barium carbonate, nano-copper powder, or nano-zinc powder. The nano-copper powder and nano-zinc powder have a particle size of 10-500 nm, and the specific structure of the organometallic compound is not specifically limited, but is preferably selected from zinc-based organometallic compounds and iron-based organometallic compounds.

[0038] Preferably, the solvent used in the preparation of the casting solution and the spraying solution is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide, acetone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, benzene, and toluene;

[0039] In step S4, the DC voltage for electrostatic spraying is 10-30kV, the receiving distance is 5-25cm, and the basic spraying rate is 1-5ml / h.

[0040] Preferably, the coagulation bath in step S4 is pure water or a mixed solution, wherein the mixed solution includes pure water and the solvent, and the mass ratio of the solvent is 5-45 wt%.

[0041] Preferably, the mesh diameter of the stainless steel mesh is 3-10 μm; the constant temperature and humidity environment in step S2 is a temperature of 30-80℃ and a relative humidity of 50-100%.

[0042] Preferably, the pickling in step S4 involves soaking in dilute hydrochloric acid or dilute nitric acid with a concentration of 0.1-1 mol / L for 4-12 hours.

[0043] Preferably, the stainless steel mesh is woven from metal material, and the mesh diameter of the stainless steel mesh is 3-10μm.

[0044] Secondly, the present invention provides a porous hydrophilic separation membrane with a rough surface, which is prepared by the above-mentioned preparation method and is used as an ultrafiltration membrane or microfiltration membrane in water treatment.

[0045] Example 1

[0046] A method for preparing a porous hydrophilic separation membrane with a rough surface includes the following steps: 4 wt% polyethylene glycol 6000, 0.5 wt% lithium chloride, 0.5 wt% calcium carbonate, and 83 wt% dimethyl sulfoxide are ultrasonically dispersed for 1 hour. Then, 12 wt% polysulfone is added and stirred at 60°C for 12 hours to dissolve, forming a transparent viscous solution. The solution is then degassed under vacuum for 12 hours to obtain a casting solution. The casting solution is heated to 40°C and uniformly coated onto a smooth, clean glass plate to a thickness of 100 micrometers, forming a liquid film. A layer of convex stainless steel mesh with a mesh diameter of 3 micrometers is immersed in the surface of the liquid film. The liquid film is then placed in a constant temperature and humidity environment at 40°C and 80% relative humidity for 3 hours, after which it is removed. The stainless steel mesh is removed, and the liquid film is then placed in the same constant temperature and humidity environment for another 6 hours before being removed, resulting in a separation membrane with a textured surface.

[0047] The spraying solution comprises the following components: 6 wt% polysulfone, 7 wt% polyethylene glycol 6000, 0.2 wt% lithium chloride, 0.8 wt% calcium carbonate, and 86 wt% dimethyl sulfoxide. Polyethylene glycol 6000, lithium chloride, calcium carbonate, and dimethyl sulfoxide are ultrasonically dispersed for 1 hour. Polysulfone is then added with stirring, and the mixture is stirred and dissolved at 60°C for 12 hours to form a transparent, viscous solution. This solution is then degassed under vacuum for 12 hours to obtain the spraying solution.

[0048] The electrostatic spraying conditions were a DC voltage of 10kV, a receiving distance of 5cm, and a spray liquid extrusion rate of 1ml / h. Using the separation membrane with an uneven surface structure as the substrate, the spray liquid was electrostatically sprayed onto the substrate surface for 3 hours. The substrate was then immersed in pure water for 6 hours to undergo non-solvent-induced phase separation and solidify into a film. After soaking in 0.2mol / L dilute hydrochloric acid for 6 hours, the membrane was rinsed with pure water to obtain a porous hydrophilic separation membrane with a rough surface structure.

[0049] Comparative Example 1

[0050] The preparation process and conditions of the casting solution were the same as in Example 1. The casting solution was heated to 40°C and uniformly coated onto a smooth and clean glass plate to a thickness of 100 micrometers, forming a liquid film. The liquid film was then immersed in pure water for 6 hours to undergo non-solvent-induced phase separation and solidify into a membrane, yielding a polysulfone porous membrane.

[0051] Example 2

[0052] A method for preparing a porous hydrophilic separation membrane with a rough surface includes the following steps: 10 wt% polyvinylpyrrolidone, 0.1 wt% zinc chloride, 0.2 wt% nano-copper powder, and 74.7 wt% N,N-dimethylacetamide are ultrasonically dispersed for 0.5 h. Then, 15 wt% polyethersulfone is added and stirred at 80 °C for 8 h to dissolve, forming a transparent viscous solution. The solution is then degassed under vacuum for 6 h to obtain a casting solution. The casting solution is heated to 60 °C and uniformly coated onto a smooth, clean glass plate to a thickness of 30 micrometers, forming a liquid film. A layer of stainless steel mesh with a raised surface structure (10 micrometers in diameter) is immersed in the surface of the liquid film. The liquid film is then placed at 80 °C and 50% relative humidity for 12 h, after which it is removed. The stainless steel mesh is removed, and the liquid film with the removed stainless steel mesh is placed in the same constant temperature and humidity environment for another 12 h before being removed, resulting in a separation membrane with a textured surface.

[0053] The coating solution comprises: 4 wt% polyethersulfone, 1 wt% polyvinylpyrrolidone, 0.5 wt% zinc chloride, 0.3 wt% nano-copper powder, and 94.2 wt% dimethylacetamide. The coating solution is prepared using the same method as the casting solution described above. Electrostatic spraying conditions are: DC voltage 30 kV, receiving distance 20 cm, and coating solution extrusion rate 3.5 ml / h. After electrostatically spraying the coating solution onto the substrate surface for 1 hour, the substrate is immersed in a 5 wt% dimethylacetamide aqueous solution for 12 hours, where non-solvent-initiated phase separation occurs, followed by film coagulation. Then, after soaking in 0.8 mol / L dilute nitric acid for 4 hours and rinsing with pure water, a porous hydrophilic separation membrane with a rough surface structure is obtained.

[0054] Comparative Example 2

[0055] The preparation process and conditions of the casting solution were the same as in Example 2. The casting solution was heated to 60°C and uniformly coated onto a smooth and clean glass plate to a thickness of 30 micrometers, forming a liquid film. The liquid film was then immersed in a 5 wt% dimethylacetamide aqueous solution for 12 hours to undergo non-solvent-initiated phase separation and solidify into a membrane, yielding a polyethersulfone porous membrane.

[0056] Example 3

[0057] A method for preparing a porous hydrophilic separation membrane with a rough surface includes the following steps: 5 wt% polyvinyl alcohol, 1 wt% acetone, 0.1 wt% barium carbonate, and 73.9 wt% tetrahydrofuran are ultrasonically dispersed for 4 hours. Then, 20 wt% polyvinyl chloride is added and stirred at 70°C for 20 hours to dissolve, forming a transparent viscous solution. The solution is then degassed under vacuum for 36 hours to obtain a casting solution. The casting solution is heated to 30°C and uniformly coated onto a smooth, clean glass plate to a thickness of 300 micrometers, forming a liquid film. A layer of stainless steel mesh with a raised surface structure, with a mesh diameter of 5 micrometers, is immersed in the surface of the liquid film. The liquid film is then placed at 50°C and 60% relative humidity for 24 hours, after which it is removed. The stainless steel mesh is removed, and the liquid film without the stainless steel mesh is placed in the same constant temperature and humidity environment as described above for another 36 hours before being removed, resulting in a separation membrane with a textured surface.

[0058] The coating solution comprises the following components by weight: 12 wt% polyvinyl chloride, 8 wt% polyvinyl alcohol, 0.1 wt% acetone, 1 wt% barium carbonate, and 78.9 wt% tetrahydrofuran. The coating solution was prepared using the same method as the casting solution described above. Electrostatic spraying conditions were: DC voltage 20 kV, receiving distance 25 cm, and coating solution extrusion rate 2 ml / h. After electrostatically spraying the coating solution onto the substrate surface for 8 hours, the substrate was immersed in a 25 wt% N,N-dimethylformamide aqueous solution for 6 hours, resulting in non-solvent-initiated phase separation and coagulation into a film. The film was then soaked in 0.1 mol / L dilute hydrochloric acid for 12 hours and rinsed with pure water to obtain a porous hydrophilic separation membrane with a rough surface structure.

[0059] Comparative Example 3

[0060] The preparation process and conditions of the casting solution were the same as in Example 3. The casting solution was heated to 30°C and uniformly coated onto a smooth and clean glass plate to a thickness of 300 micrometers, forming a liquid film. The liquid film was then immersed in a 25 wt% N,N-dimethylformamide aqueous solution for 6 hours, where non-solvent-initiated phase separation occurred, followed by solidification to obtain a porous polyvinyl chloride membrane.

[0061] Example 4

[0062] A method for preparing a porous hydrophilic separation membrane with a rough surface includes the following steps: 10 wt% polyethylene glycol-4000, 0.2 wt% iron-based organic framework metal compound, 0.3 wt% calcium carbonate, and 74.5 wt% toluene are ultrasonically dispersed for 0.5 h. Then, 15 wt% polycarbonate is added and stirred at 90°C for 10 h to dissolve, forming a transparent viscous solution. The solution is then degassed under vacuum for 12 h to obtain a casting solution. The casting solution is heated to 40°C and uniformly coated onto a smooth, clean glass plate to a thickness of 80 micrometers, forming a liquid film. A layer of stainless steel mesh with a raised surface structure, with a mesh diameter of 10 micrometers, is immersed in the surface of the liquid film. The liquid film is then placed at 60°C and 90% relative humidity for 14 h, after which it is removed. The stainless steel mesh is removed, and the liquid film without the stainless steel mesh is placed in the same constant temperature and humidity environment as described above for another 12 h before removal, resulting in a separation membrane with a textured surface.

[0063] The spraying solution comprises the following components: 5 wt% polycarbonate, 5 wt% polyethylene glycol-4000, 0.8 wt% iron-based organic framework metal compound, 0.1 wt% calcium carbonate, and 89.1 wt% toluene. The spraying solution is prepared using the same method as the casting solution described above. Electrostatic spraying conditions are: DC voltage 30 kV, receiving distance 6 cm, and spraying solution extrusion rate 2.8 ml / h. Using a separation membrane with an uneven surface structure as the substrate, the spraying solution is electrostatically sprayed onto the substrate surface for 7 hours. The substrate is then immersed in a 45 wt% tetrahydrofuran aqueous solution for 12 hours to undergo non-solvent-initiated phase separation and solidify into a film. After soaking in 0.5 mol / L dilute nitric acid for 8 hours, it is rinsed with pure water to obtain a porous hydrophilic separation membrane with a rough surface structure.

[0064] Comparative Example 4

[0065] The preparation process and conditions of the casting solution were the same as in Example 4. The casting solution was heated to 40°C and uniformly coated onto a smooth and clean glass plate to a thickness of 80 micrometers, forming a liquid film. The liquid film was then immersed in a 45 wt% tetrahydrofuran aqueous solution for 12 hours to undergo non-solvent-initiated phase separation and solidify into a membrane, yielding a polycarbonate porous membrane.

[0066] Example 5

[0067] A method for preparing a porous hydrophilic separation membrane with a rough surface includes the following steps: 7 wt% polyvinylpyrrolidone, 0.1 wt% lithium chloride, 0.9 wt% nano zinc powder, and 70 wt% solvent are ultrasonically dispersed for 0.5 h. Then, 22 wt% polyvinylidene fluoride is added with stirring, and the mixture is stirred and dissolved at 40 °C for 24 h to form a transparent viscous solution. The solution is then degassed under vacuum for 48 h to obtain a casting solution. The casting solution is heated to 50 °C and uniformly coated onto a smooth, clean glass plate to a thickness of 250 micrometers, forming a liquid film. A layer of stainless steel mesh with a raised surface structure (7 micrometers in diameter) is immersed in the surface of the liquid film. The liquid film is then placed at 50 °C and 100% relative humidity for 10 h, after which it is removed. The stainless steel mesh is removed, and the liquid film without the stainless steel mesh is placed in the same constant temperature and humidity environment as described above for 16 h before being removed, resulting in a separation membrane with a textured surface structure. The solvent includes toluene and benzene in a mass ratio of 9:1.

[0068] The spraying solution comprises the following components: 4 wt% polyvinylidene fluoride, 3 wt% polyvinylpyrrolidone, 0.4 wt% lithium chloride, 0.1 wt% nano zinc powder, and 92.5 wt% solvent, wherein the solvent includes toluene and benzene in a mass ratio of 9:1. The spraying solution is prepared using the same method as the casting solution described above. The electrostatic spraying conditions are: DC voltage 10 kV, receiving distance 15 cm, and spraying solution extrusion rate 1.8 ml / h. Using the previously obtained separation membrane with an uneven surface structure as the substrate, the spraying solution is electrostatically sprayed onto the substrate surface for 10 h. The substrate is then immersed in a 15 wt% tetrahydrofuran / toluene (tetrahydrofuran to toluene mass ratio 5:5) aqueous solution for 10 h to undergo non-solvent-initiated phase separation and solidify into a film. After soaking in 0.3 mol / L dilute hydrochloric acid for 6 h and rinsing with pure water, a porous hydrophilic separation membrane with a rough surface structure is obtained.

[0069] Comparative Example 5

[0070] The preparation process and conditions of the casting solution were the same as in Example 5. The casting solution was heated to 50°C and uniformly coated onto a smooth and clean glass plate to a thickness of 250 micrometers, forming a liquid film. The liquid film was then immersed in a 15 wt% tetrahydrofuran / toluene (tetrahydrofuran to toluene mass ratio 5:5) aqueous solution for 10 hours. After non-solvent-initiated phase separation, the film solidified to obtain a polyvinylidene fluoride porous membrane.

[0071] Example 6

[0072] A method for preparing a porous hydrophilic separation membrane with a rough surface includes the following steps: 7 wt% polyvinylpyrrolidone, 0.1 wt% pure water, 0.9 wt% barium carbonate, and 70 wt% solvent are ultrasonically dispersed for 2 hours. Then, 6 wt% hydrophilic polymer is added and stirred at 90°C for 6 hours to dissolve, forming a transparent viscous solution. The solution is then degassed under vacuum for 10 hours to obtain a casting solution. The casting solution is heated to 60°C and uniformly coated onto a smooth, clean glass plate to a thickness of 120 micrometers, forming a liquid film. A layer of stainless steel mesh with a raised surface structure (3 micrometers in diameter) is immersed in the surface of the liquid film. The liquid film is then placed at 80°C and 60% relative humidity for 8 hours, after which it is removed, and the stainless steel mesh is removed. The liquid film without the stainless steel mesh is then placed in the same constant temperature and humidity environment as described above for 24 hours before being removed, resulting in a separation membrane with a textured surface. The solvents include N,N-dimethylacetamide and acetone in a mass ratio of 7:3, and the hydrophilic polymers include polyvinylidene fluoride-copolymer-chlorotrifluoroethylene and polysulfone in a mass ratio of 8:2.

[0073] The spraying solution comprises the following components: 5 wt% hydrophilic polymer, 10 wt% polyvinylpyrrolidone, 0.1 wt% pure water, 0.3 wt% barium carbonate, and 84.6 wt% solvent. The hydrophilic polymer is composed of polyvinylidene fluoride-copolymer-chlorotrifluoroethylene and polysulfone in a mass ratio of 8:2. The solvent includes N,N-dimethylacetamide and acetone in a mass ratio of 7:3. The spraying solution is prepared using the same method as the casting solution described above. The electrostatic spraying conditions are: DC voltage 25 kV, receiving distance 5 cm, and spraying solution extrusion rate 3 ml / h. Using the previously obtained separation membrane with an uneven surface structure as a substrate, the spraying solution is electrostatically sprayed onto the substrate surface for 8 hours. The substrate is then immersed in pure water for 12 hours to undergo non-solvent-induced phase separation and solidify into a film. After soaking in 0.9 mol / L dilute nitric acid for 4 hours and rinsing with pure water, a porous hydrophilic separation membrane with a rough surface structure is obtained.

[0074] Comparative Example 6

[0075] The preparation process and conditions of the casting solution were the same as in Example 6. The casting solution was heated to 60°C and uniformly coated onto a smooth and clean glass plate to a thickness of 120 micrometers, forming a liquid film. The liquid film was then immersed in pure water for 12 hours to undergo non-solvent-induced phase separation and solidify into a membrane, yielding a polyvinylidene fluoride-copolymer-chlorotrifluoroethylene / polysulfone porous membrane.

[0076] Example 7

[0077] A method for preparing a porous hydrophilic separation membrane with a rough surface includes the following steps: 10 wt% polyethylene glycol 2000, 1 wt% barium carbonate, 0.2 wt% inorganic chloride, and 73.8 wt% solvent are ultrasonically dispersed for 2 hours. Then, 15 wt% hydrophilic polymer is added and stirred at 60°C for 14 hours to dissolve, forming a transparent viscous solution. The solution is then degassed under vacuum for 12 hours to obtain a casting solution. The casting solution is heated to 50°C and uniformly coated onto a smooth, clean glass plate to a thickness of 260 micrometers, forming a liquid film. A layer of stainless steel mesh with a raised surface structure (7 micrometers in diameter) is immersed in the surface of the liquid film. The liquid film is then placed at 50°C and 80% relative humidity for 5 hours, after which it is removed. The stainless steel mesh is removed, and the liquid film is placed under the same constant temperature and humidity environment for another 12 hours before being removed, resulting in a separation membrane with a textured surface. The inorganic components include lithium chloride and zinc chloride, with a mass ratio of 1:1. The solvents include N,N-dimethylacetamide and N,N-dimethylformamide, with a mass ratio of 6:4. The hydrophilic polymers include polysulfone and polytetrafluoroethylene, with a mass ratio of 9:1.

[0078] The spraying solution comprises the following components: 6 wt% hydrophilic polymer, 6 wt% polyethylene glycol 2000, 0.8 wt% barium carbonate, 0.2 wt% inorganic matter, and 87 wt% solvent. The inorganic matter includes lithium chloride and zinc chloride in a 1:1 mass ratio. The solvent includes N,N-dimethylacetamide and N,N-dimethylformamide in a 6:4 mass ratio. The hydrophilic polymer comprises polysulfone and polytetrafluoroethylene in a 9:1 mass ratio. The spraying solution is prepared using the same method as the casting solution described above. The electrostatic spraying conditions were a DC voltage of 10kV, a receiving distance of 18cm, and a spray liquid extrusion rate of 1.4ml / h. Using the obtained separation membrane with an uneven surface structure as the substrate, the spray liquid was electrostatically sprayed onto the substrate surface for 10h. The substrate was then immersed in pure water for 8h to undergo non-solvent-induced phase separation and solidify into a film. After soaking in 0.5mol / L dilute hydrochloric acid for 8h, it was rinsed with pure water to obtain a porous hydrophilic separation membrane with a rough surface structure.

[0079] Comparative Example 7

[0080] The preparation process and conditions of the casting solution were the same as in Example 7. The casting solution was heated to 50°C and uniformly coated onto a smooth and clean glass plate to a thickness of 260 micrometers, forming a liquid film. The liquid film was then immersed in pure water for 8 hours to undergo non-solvent-induced phase separation and solidify into a membrane, yielding a polysulfone / polytetrafluoroethylene porous membrane.

[0081] Example 8

[0082] A method for preparing a porous hydrophilic separation membrane with a rough surface includes the following steps: 7 wt% of a polymer, 0.8 wt% of a nano-solid gas generator, 1 wt% of zinc chloride, and 71.2 wt% of a solvent are ultrasonically dispersed for 1 hour. Then, 20 wt% of a hydrophilic polymer is added and stirred at 80°C for 10 hours to dissolve, forming a transparent viscous solution. The solution is then degassed under vacuum for 10 hours to obtain a casting solution. The casting solution is heated to 40°C and uniformly coated onto a smooth, clean glass plate to a thickness of 140 micrometers, forming a liquid film. A layer of stainless steel mesh with a raised surface structure (10 micrometers in diameter) is immersed in the surface of the liquid film. The liquid film is then placed at 60°C and 70% relative humidity for 6 hours, after which it is removed. The stainless steel mesh is removed, and the liquid film is placed under the same constant temperature and humidity environment for another 15 hours, resulting in a separation membrane with a textured surface. The polymers include polyvinylpyrrolidone and polyvinyl alcohol in a mass ratio of 1:9, the nano solid gas generators include calcium carbonate and barium carbonate in a mass ratio of 3:7, the solvents include N,N-dimethylacetamide and toluene in a mass ratio of 9:1, and the hydrophilic polymers include polyacrylate and polyimide in a mass ratio of 4:6.

[0083] The spraying solution comprises the following components: 5 wt% hydrophilic polymer, 5 wt% polymer, 0.2 wt% nano-solid gas generator, 0.4 wt% zinc chloride, and 89.4 wt% solvent. The spraying solution is prepared using the same method as the casting solution described above. Electrostatic spraying conditions are: DC voltage 30 kV, receiving distance 20 cm, and spraying solution extrusion rate 2.2 ml / h. After electrostatically spraying the solution onto the substrate surface for 6 hours, the substrate is immersed in pure water for 6 hours to undergo non-solvent-induced phase separation and solidify into a film. Then, after soaking in 0.4 mol / L dilute nitric acid for 10 hours and rinsing with pure water, a porous hydrophilic separation membrane with a rough surface structure is obtained. The polymers include polyvinylpyrrolidone and polyvinyl alcohol in a mass ratio of 1:9, the nano solid gas generators include calcium carbonate and barium carbonate in a mass ratio of 3:7, the solvents include N,N-dimethylacetamide and toluene in a mass ratio of 9:1, and the hydrophilic polymers include polyacrylate and polyimide in a mass ratio of 4:6.

[0084] Comparative Example 8

[0085] The preparation process and conditions of the casting solution were the same as in Example 8. The casting solution was heated to 50°C and uniformly coated onto a smooth and clean glass plate to a thickness of 260 micrometers, forming a liquid film. The liquid film was then immersed in pure water for 6 hours to undergo non-solvent-induced phase separation and solidify into a membrane, yielding a polyacrylate / polyimide porous membrane.

[0086] The properties of the porous membranes prepared in the Examples and Comparative Examples, such as pure water flux, water contact angle, bovine serum albumin (BSA), tensile strength, and elongation at break, are listed in Table 1.

[0087] The membrane water flux J is calculated according to the following formula:

[0088]

[0089] Where V is the volume of water permeated (L), and A is the membrane area (m²). 2 ), where t is the test time (h) and the test pressure is 0.1 MPa.

[0090] The water contact angle on the membrane surface was measured using a three-point measurement method. Five different locations were selected for each sample, and the final average value was taken.

[0091] The retention rate of bovine serum albumin (BSA) in the membrane was measured using ultraviolet absorption spectrometry. Before testing, the membrane surface was washed with purified water. After pre-pressurization at 0.1 MPa for 30 minutes, the prepared BSA solution was filtered. The stock solution and permeate were collected every 10 minutes. The absorbance of the stock solution and permeate was measured using a UV-Vis spectrophotometer (UV-2450, SHIMADZU, Japan). The retention rate was calculated using the following formula:

[0092]

[0093] In the formula: R is the retention rate (%); C p The absorbance value of the original solution; C f This represents the absorbance value of the transmitted liquid.

[0094] The membrane sample was cut into strips of 5×1cm. Using a universal testing machine (HY-1080, Laizhou Electronic Instruments Co., Ltd.), the tensile strength and elongation at break of the membrane were tested at 20℃ and 20mm / min. Each sample was tested 5 times and the average value was taken.

[0095] Table 1 Comparison of the performance of porous membranes prepared in the Examples and Comparative Examples

[0096]

[0097]

[0098] Table 1 (continued) Comparison of the performance of porous membranes prepared in the Examples and Comparative Examples

[0099]

[0100] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several changes and improvements without departing from the overall concept of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a porous hydrophilic separation membrane with a rough surface, characterized in that: The method includes at least the following steps: S1: Preparation of casting solution: After mixing the pore-forming agent and solvent, add the hydrophilic polymer while stirring, and stir to dissolve at a certain temperature to form a transparent viscous solution. Vacuum degassing for 6-48 hours yields the casting solution. S2: Evaporation phase separation to form a film. The casting solution obtained in step S1 is heated to 30-60℃ and uniformly coated onto a glass plate to form a liquid film. A stainless steel mesh with a raised surface is immersed in the surface of the liquid film. The liquid film after immersion in the stainless steel mesh is placed in a constant temperature and humidity environment for 3-36 hours. Then, the stainless steel mesh is removed, and the liquid film after removing the stainless steel mesh is placed in the constant temperature and humidity environment for 3-36 hours before being taken out to obtain a separation membrane with a concave and convex surface structure. S3: To prepare the spraying liquid, mix the pore-forming agent and solvent, stir and add the hydrophilic polymer, and stir to dissolve at a certain temperature to form a transparent viscous solution. Vacuum degassing yields the spraying liquid. S4: Prepare a rough surface by electrostatic spraying. Using the separation membrane with an uneven surface structure obtained in step S2 as the receiving substrate, after electrostatically spraying the coating liquid onto the substrate surface, immerse the substrate in a coagulation bath for 6-12 hours to solidify into a film. After acid washing, rinse with pure water to obtain a porous hydrophilic separation membrane with a rough surface. In this process, acid washing causes the nano-solid gas generator in the pore-forming agent to generate gas, thereby forming pores on the membrane surface. The nano solid gas generator is at least one of calcium carbonate, barium carbonate, nano copper, and nano zinc.

2. The method for preparing a porous hydrophilic separation membrane with a rough surface according to claim 1, characterized in that: The mass fractions of each component in the casting solution are: 6-25 parts hydrophilic polymer, 2-12 parts pore-forming agent, and 63-92 parts solvent; the mass fractions of each component in the spraying solution are: 4-20 parts hydrophilic polymer, 1-12 parts pore-forming agent, and 70-95 parts solvent.

3. The method for preparing a porous hydrophilic separation membrane with a rough surface according to claim 1, characterized in that: The hydrophilic polymer mentioned in the preparation of casting solution and spraying solution is at least one of polyethersulfone, polysulfone, polyamide, polyvinyl chloride and its copolymers, polyvinylidene fluoride and its copolymers, polyimide, polycarbonate, polyacrylate, and polytetrafluoroethylene.

4. The method for preparing a porous hydrophilic separation membrane with a rough surface according to claim 1, characterized in that: The pore-forming agent used in the preparation of casting liquid and spraying liquid comprises the following components by weight: 1-10 parts polymer, 0.1-1 parts inorganic matter and 0.1-1 parts nano solid gas generator, wherein the polymer is selected from at least one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol; and the inorganic matter is selected from at least one of lithium chloride, zinc chloride, acetone, organoframe metal compounds, and pure water.

5. The method for preparing a porous hydrophilic separation membrane with a rough surface according to claim 1, characterized in that: The solvents used in the preparation of casting solutions and spraying solutions are selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide, acetone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, benzene, and toluene; In step S4, the DC voltage for electrostatic spraying is 10-30kV, the receiving distance is 5-25cm, and the basic spraying rate is 1-5ml / h.

6. The method for preparing a porous hydrophilic separation membrane with a rough surface according to claim 5, characterized in that: The coagulation bath mentioned in step S4 is pure water or a mixed solution. The mixed solution includes pure water and the solvent, and the mass ratio of the solvent is 5-45 wt%.

7. The method for preparing a porous hydrophilic separation membrane with a rough surface according to claim 1, characterized in that: The stainless steel mesh has a mesh diameter of 3-10 μm; the constant temperature and humidity environment in step S2 is a temperature of 30-80℃ and a relative humidity of 50-100%.

8. A method for preparing a porous hydrophilic separation membrane with a rough surface according to claim 1, characterized in that: The pickling in step S4 involves soaking in dilute hydrochloric acid or dilute nitric acid with a concentration of 0.1-1 mol / L for 4-12 hours.

9. A method for preparing a porous hydrophilic separation membrane with a rough surface according to claim 1, characterized in that: The stainless steel mesh is woven from metal material, and the mesh diameter is 3-10 μm.

10. A porous hydrophilic separation membrane with a rough surface, characterized in that: The separation membrane is prepared by any one of the preparation methods described in claims 1-9, and is used as an ultrafiltration membrane or microfiltration membrane in water treatment.

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