Preparation method of ultrafiltration membrane

Abstract

The invention discloses a preparation method of an acid-base-resistant and high-temperature-resistant TiO2 modified high-flux PVDF (Polyvinylidene Fluoride) ultrafiltration membrane taking a modified PP (Polypropylene) porous membrane as a supporting layer. The separation membrane comprises the modified PP porous supporting layer and a TiO2 modified hydrophilic PVDF separation membrane layer. The preparation method comprises the following steps: firstly, preparing a high-temperature-resistant and acid and alkali-resistant PP porous support layer through two-way stretching, carrying out corona treatment, then carrying out physical blending modification on inorganic nano TiO2 and PVDF to prepare a membrane casting solution, uniformly coating the membrane casting solution on the PP porous support layer subjected to corona treatment, and preparing the TiO2 / PVDF / PP high-flux ultrafiltration membrane by adopting a phase inversion method. The membrane has excellent properties of good hydrophilicity, high flux, high temperature resistance, acid and alkali resistance and the like, and can be widely applied to the fields of medicines, foods, acid and alkali recovery, industrial water treatment, petrochemical engineering and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrafiltration membranes, and more specifically to a method for preparing an ultrafiltration membrane. Background Art

[0002] Ultrafiltration technology is a membrane separation technology. Its membranes are mostly porous asymmetric structures. The filtration process uses the pressure difference on both sides of the membrane as the mass transfer power and is based on the principle of mechanical screening. It has the characteristics of room temperature operation, no phase change, low energy consumption, and high separation accuracy. It has been widely used in drinking water purification, industrial water treatment, beverages, biology, food, medicine, environmental protection, chemical industry, metallurgy, petroleum, etc.

[0003] Polyvinylidene fluoride (PVDF) is a crystalline polymer with excellent performance. Its outstanding chemical stability, excellent mechanical strength, radiation resistance, anti-pollution and heat resistance make PVDF an ideal phase transfer membrane material and has been widely used in the preparation of porous membrane materials. Currently, most PVDF membranes on the market are ultrafiltration membranes prepared with PET non-woven fabrics as the support layer. The heat resistance and acid and alkali resistance are greatly affected by the properties of PET materials, which greatly limits its industrial application range. At the same time, due to the presence of a certain degree of hydrophobicity in PVDF membranes, it is easy to be contaminated during use, resulting in a decrease in flux and an increase in membrane costs.

[0004] Therefore, it is necessary to propose a method for preparing an ultrafiltration membrane to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to solve the problems mentioned in the above background technology and provide a method for preparing an ultrafiltration membrane.

[0006] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0007] A method for preparing an ultrafiltration membrane comprises the following steps:

[0008] S1. Pretreatment of PP porous support material: corona pretreatment is performed on the PP porous membrane or non-woven fabric to enhance the hydrophilicity of the membrane and its bonding performance with the PVDF separation membrane layer. The pretreated PP porous membrane or non-woven fabric is ready for use;

[0009] S2. Prepare a casting solution: Heat polyvinylidene fluoride, nano-TiO2, porogen, additives and solvent to 60° C. in a water bath according to the formula, stir to completely dissolve them, and stir to completely dissolve all components to obtain a casting solution;

[0010] S3, coating: the casting solution is allowed to stand for 24 hours under vacuum conditions to degas, and then coated on the PP porous membrane or non-woven fabric after corona pretreatment;

[0011] S4, forming a separation membrane: after the coating is completed, the coating is allowed to stand in the air for a while and then quickly immersed in a coagulation bath. By using a phase inversion method, the casting liquid layer coated on the surface of the PP porous material undergoes phase separation to form a separation membrane;

[0012] S4. Soaking: Soak the separation membrane formed by phase separation in pure water at 25° C. for three days to obtain a finished ultrafiltration membrane.

[0013] Preferably, the stirring time in the step S2 of preparing the casting solution lasts for 6 hours.

[0014] Preferably, the coagulation bath consists of a 30% ethanol aqueous solution.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention firstly prepares a PVDF membrane by physically blending and modifying nano-TiO2 and PVDF to improve the hydrophilicity of the membrane and thus increase the anti-pollution performance of the PVDF membrane. Secondly, a porous PP material is used as the supporting layer of the membrane to enhance the high temperature resistance and acid and alkali resistance of the membrane. Finally, a high-throughput anti-pollution TiO2 / PVDF / PP ultrafiltration membrane with good acid and alkali resistance and high temperature resistance is prepared. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Embodiment 1:

[0019] The mass percentage composition of 15% polyvinylidene fluoride, 2% nano-TiO2, 3% polyvinyl pyrrolidone, and 1% lithium chloride is placed in a three-hole flask, and then 79% N, N-dimethylacetamide is added to mix the components, heated to 60°C in a water bath, and stirred at a constant speed and constant temperature for 6 hours to fully mix the components to obtain a casting solution; the casting solution is allowed to stand for degassing under vacuum conditions for 24 hours, and then the casting solution is evenly coated on the porous PP membrane support layer after corona treatment and quickly immersed in a 30% ethanol aqueous solution coagulation bath at a temperature of 25°C to form a film, and the film in the coagulation bath is taken out and immersed in pure water at 25°C for 3 days. After that, the flux and retention rate of the membrane product are tested, and the results show that the membrane water flux is 850L / m2h at 0.1Mpa, and the bovine serum protein retention rate is 35%.

[0020] Embodiment 2:

[0021] The mass percentage composition of 15% polyvinylidene fluoride, 1% nano-TiO2, 5% polyvinyl pyrrolidone, and 1% lithium chloride is placed in a three-hole flask, and then 78% N, N-dimethylacetamide is added to mix the components, heated to 60°C in a water bath, and stirred at a constant speed and constant temperature for 6 hours to fully mix the components to obtain a casting solution; the casting solution is allowed to stand for degassing under vacuum conditions for 24 hours, and then the casting solution is evenly coated on the porous PP membrane support layer after corona treatment and quickly immersed in a 30% ethanol aqueous solution coagulation bath at a temperature of 25°C to form a film, and the film in the coagulation bath is taken out and immersed in pure water at 25°C for 3 days. After that, the flux and retention rate of the membrane product are tested, and the results show that the membrane water flux is 820L / m2h at 0.1Mpa, and the bovine serum protein retention rate is 37%.

[0022] Embodiment 3:

[0023] The mass percentage composition of 17% polyvinylidene fluoride, 2% nano-TiO2, 3% polyvinyl pyrrolidone, and 1% lithium chloride is placed in a three-hole flask, and then 77% N, N-dimethylacetamide is added to mix the components, heated to 60°C in a water bath, and stirred at a constant speed and constant temperature for 6 hours to fully mix the components to obtain a casting solution; the casting solution is allowed to stand for degassing under vacuum conditions for 24 hours, and then the casting solution is evenly coated on the porous PP membrane support layer after corona treatment and quickly immersed in a 30% ethanol aqueous solution coagulation bath at a temperature of 25°C to form a film, and the film in the coagulation bath is taken out and immersed in pure water at 25°C for 3 days. After that, the flux and retention rate of the membrane product are tested, and the results show that the membrane water flux is 820L / m2h at 0.1Mpa, and the bovine serum protein retention rate is 42%.

Claims

1. A method for preparing an ultrafiltration membrane, characterized in that: The following steps are involved: S1. Pretreatment of PP porous support material: corona pretreatment is performed on the PP porous membrane or non-woven fabric to enhance the hydrophilicity of the membrane and its bonding performance with the PVDF separation membrane layer. The pretreated PP porous membrane or non-woven fabric is ready for use; S2. Prepare a casting solution: Heat polyvinylidene fluoride, nano-TiO2, porogen, additives and solvent to 60° C. in a water bath according to the formula, stir to completely dissolve them, and stir to completely dissolve all components to obtain a casting solution; S3, coating: the casting solution is allowed to stand for 24 hours under vacuum conditions to degas, and then coated on the PP porous membrane or non-woven fabric after corona pretreatment; S4, forming a separation membrane: after the coating is completed, the casting liquid layer coated on the surface of the PP porous material is phase-separated to form a separation membrane by standing in the air for a while and then quickly immersing the coating in a coagulation bath. S4. Soaking: Soak the separation membrane formed by phase separation in pure water at 25° C. for three days to obtain a finished ultrafiltration membrane.

2. The method for preparing an ultrafiltration membrane according to claim 1, characterized in that: The stirring time in the step S2 of preparing the casting solution lasts for 6 hours.

3. The method for preparing an ultrafiltration membrane according to claim 1, characterized in that: The coagulation bath consists of a 30% ethanol aqueous solution.