Preparation method of a novel inorganic nanofiltration membrane and product prepared thereby

Abstract

The application discloses a preparation method of a novel inorganic nanofiltration membrane and a product prepared by the method. The preparation method comprises the following steps: taking zirconium sol or aluminum sol with a concentration of greater than or equal to 0.8 mol / L as a basis, forming a dispersion system in which an oil phase wraps the sol by using a microemulsion method, and then completing a sol-gel process in the water phase separated from the oil phase to form a uniformly dispersed gel body; the obtained microemulsion is uniformly coated on the surface of a porous ceramic membrane as a coating solution; and the novel inorganic nanofiltration membrane is obtained through drying and sintering. The application reduces the particle size of particles, inhibits the gel drying cracking, and finally prevents the cracking of the membrane layer, so that a continuous membrane is effectively formed. The application is easy to operate and adjust, stable and controllable, and is beneficial to popularization and application, and has a positive promoting effect on the development of nanofiltration membrane technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic membrane, in particular to a preparation method of inorganic nanofiltration membrane and the product prepared by the method. BACKGROUND

[0002] Inorganic membrane has higher chemical stability, thermal stability and mechanical stability compared with polymer membrane. Ceramic membrane can be generally divided into macro-porous, meso-porous and micro-porous membrane according to pore size. In the preparation of macro-porous and meso-porous ceramic membrane, suspension or colloidal sol is usually deposited on a porous support, and then sintering or calcination process is performed. In recent years, a large amount of research has been conducted on the development of inorganic nanofiltration membrane, and sol-gel process is widely used due to its convenient operation and easy adjustment.

[0003] The prior art usually adopts sol-gel method to prepare sol particles with smaller particle size, and then nanometer oxide particles are prepared by aging, drying and calcination. After preparation of dispersion liquid, the inorganic nanofiltration membrane is formed by coating on the surface of porous ceramic membrane. However, the prior art has a large technical defect: due to the rapid hydrolysis and condensation chemical reaction of the precursor, it has always been a problem to control the sol particles to be small enough. In addition, the aging and drying process is prone to cracking, which causes cracks on the membrane surface and cannot form a continuous membrane, thereby causing defects of the nanofiltration membrane. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art, and provides a novel preparation method of inorganic nanofiltration membrane. The preparation method is based on zirconium sol or aluminum sol with a concentration of ≥0.8 mol / L, and a dispersion system of sol wrapped by oil phase is formed by microemulsion method. Then, the sol-gel process is completed in the water phase separated from the oil phase, so as to reduce the particle size. The prepared microemulsion is uniformly coated on the surface of the ceramic membrane, which effectively inhibits the cracking of the gel during drying, and finally prevents the cracking of the membrane layer. Another object of the present application is to provide a product prepared by the above novel preparation method of inorganic nanofiltration membrane.

[0005] The object of the present application is achieved by the following technical solutions:

[0006] The present application provides a novel preparation method of inorganic nanofiltration membrane, which comprises the following steps:

[0007] (1) Zirconium sol or aluminum sol with a concentration of ≥0.8 mol / L, preferably a concentration of 0.8-2.5 mol / L, is used to form a transparent microemulsion of water-in-oil by emulsifying with oil phase at a temperature of 5-20℃ according to the volume ratio of zirconium sol or aluminum sol: oil phase = 1:2-9, and then a stable microemulsion system with a viscosity of 20-60 mPa.s is obtained by mixing and aging, which is used as a coating liquid;

[0008] (2) using a one-time thin film coating method, the coating solution is coated on the surface of the porous ceramic membrane, the coating time is 10-40s, after drying, sintering is carried out at a temperature of 550-620℃, and the temperature is kept for 20-60min, so that a new type of inorganic nanofiltration membrane with a particle size of 5-10nm and an average pore size of 1-10nm is obtained.

[0009] Further, the oil phase of the application is composed of solvent, surfactant, and co-surfactant according to the volume ratio of solvent: surfactant: co-surfactant = 1: 0.2-0.4: 0.1-0.4; wherein the solvent is one or a combination of cyclohexane, heptane, and isopentane, the surfactant is triton-100 or cetyltrimethylammonium bromide, and the co-surfactant is one or a combination of n-butanol, n-pentanol, and isobutyl alcohol.

[0010] Further, the aging temperature of step (1) is 20-40℃, and the aging time is 12-36h. The drying temperature in step (2) is ≤25℃, and the drying time is 6-12h.

[0011] In the above scheme, the pore size of the porous ceramic membrane of the application is 50-200nm. 1-5wt% Y(NO3)3·5H2O is added to the zirconium sol.

[0012] The product obtained by the preparation method of the new type of inorganic nanofiltration membrane.

[0013] The application has the following beneficial effects:

[0014] (1) The application is a technical improvement based on the preparation of inorganic nanofiltration membranes by sol-gel method, and the sol is used as the water phase in the microemulsion system, so that it is uniformly distributed in the oil phase to form microemulsion droplets. This method realizes an independent gel process in each microemulsion droplet, effectively controls the particle size to the minimum value.

[0015] (2) The application uses a microemulsion method for preparation, and the oil phase is used as the main solvent of the membrane solution. Due to the barrier of the microemulsion oil phase, the agglomeration of particles is inhibited, and the dispersion and uniformity of the particles are further improved.

[0016] (3) The prepared microemulsion is uniformly coated on the surface of the ceramic membrane, effectively inhibiting the cracking of the gel during drying, and finally preventing the cracking of the membrane layer. The application is easy to operate and adjust, stable and controllable, and is conducive to popularization and application, and has a positive promoting effect on the development of nanofiltration membrane technology. BRIEF DESCRIPTION OF DRAWINGS

[0017] The application will be further described in detail below in combination with examples and drawings:

[0018] Figure 1is a surface scanning photo of a new inorganic nanofiltration membrane prepared by the embodiment one of the present application;

[0019] Figure 2 is a surface scanning photo of a new inorganic nanofiltration membrane prepared by the embodiment two of the present application. DETAILED DESCRIPTION

[0020] Embodiment one:

[0021] The preparation method of the new inorganic nanofiltration membrane in this embodiment is as follows:

[0022] (1) The zirconium sol with a concentration of 1.2 mol / L and 2wt% of Y(NO3)3·5H2O is used to form a water-in-oil transparent microemulsion by high-speed emulsification with the oil phase at a volume ratio of zirconium sol:oil phase = 1:6 at a temperature of 15℃, and then a stable microemulsion system with a viscosity of 45 mPa.s obtained by mixing and aging at a temperature of 30℃ for 24h is used as a coating solution; wherein the oil phase is composed of cyclohexane, triton-100 and n-butanol at a volume ratio of cyclohexane:triton-100:n-butanol = 1:0.3:0.4;

[0023] (2) The coating solution is coated on the surface of a porous ceramic membrane with a pore size of 100 nm by a one-time thin film coating method, and dried at a temperature of 20℃ for 12h, and then sintered at a temperature of 600℃ for 50min to obtain a new inorganic nanofiltration membrane with uniform particle distribution, a particle size of 6nm and an average pore size of 5nm, as shown in Figure 1 , the membrane surface is free of defects and cracks, and the particle size and pore size meet the requirements.

[0024] Embodiment two:

[0025] The preparation method of the new inorganic nanofiltration membrane in this embodiment is as follows:

[0026] (1) The aluminum sol with a concentration of 1.5 mol / L is used to form a water-in-oil transparent microemulsion by high-speed emulsification with the oil phase at a volume ratio of aluminum sol:oil phase = 1:5 at a temperature of 20℃, and then a stable microemulsion system with a viscosity of 37 mPa.s obtained by mixing and aging at a temperature of 35℃ for 30h is used as a coating solution; wherein the oil phase is composed of heptane, cetyltrimethylammonium bromide and n-pentanol at a volume ratio of heptane:cetyltrimethylammonium bromide:n-pentanol = 1:0.2:0.3;

[0027] (2) The coating solution is coated on the surface of a porous ceramic membrane with a pore size of 60 nm by a one-time thin film coating method, and dried at a temperature of 15℃ for 9h, and then sintered at a temperature of 580℃ for 30min to obtain a new inorganic nanofiltration membrane with uniform particle distribution, a particle size of 8nm and an average pore size of 4nm, as shown inFigure 2 As shown, the film surface is defect-free and crack-free, and the particle size and pore size meet the requirements.

Claims

1. A method for preparing a novel inorganic nanofiltration membrane, characterized in that... Includes the following steps: (1) Using zirconium sol or aluminum sol with a concentration ≥0.8mol / L, at a volume ratio of zirconium sol or aluminum sol: oil phase = 1:2~9, emulsify with the oil phase at a temperature of 5~20℃ to form a transparent water-in-oil microemulsion. Then, after mixing, age at a temperature of 20~40℃ for 12~36h to obtain a stable microemulsion system with a viscosity of 20~60mPa.s as the coating liquid; wherein, 1~5wt% Y(NO3)3·5H2O is added to the zirconium sol; the oil phase is composed of solvent, surfactant, and co-surfactant at a volume ratio of solvent:surfactant:co-surfactant = 1:0.2~0.4:0.1~0.4; wherein, the solvent is one or a combination of cyclohexane, heptane, and isopentane, the surfactant is Triton-100 or hexadecyltrimethylammonium bromide, and the co-surfactant is one or a combination of n-butanol, n-pentanol, and isobutanol. (2) The coating liquid is coated on the surface of a porous ceramic membrane with a pore size of 50-200 nm using a one-time thin film coating method. The coating time is 10-40 s. After drying at ≤25℃ for 6-12 h, the membrane is sintered at 550-620℃ for 20-60 min to obtain a novel inorganic nanofiltration membrane with a particle size of 5-10 nm, an average pore size of 1-10 nm, and no defects or cracks on the membrane surface.

2. The method for preparing the novel inorganic nanofiltration membrane according to claim 1, characterized in that: The concentration of the zirconium sol or aluminum sol is 0.8–2.5 mol / L.

3. The product prepared by the method of preparing the novel inorganic nanofiltration membrane according to any one of claims 1-2.

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