阅读说明：本技术 具有分叉孔道结构的分离膜及其制备方法 (Separation membrane with bifurcated pore structure and preparation method thereof ) 是由 董德华 赵志博 叶正茂 于 2019-11-05 设计创作，主要内容包括：本发明技术属于膜技术领域,尤其涉及一种具有分叉孔道结构的分离膜制备方法及其应用,该分离膜可以应用于工业分离,包括液-液分离,固-液分离,气-固分离等,具体应用包括(不限于)油水分离、污水处理、海水淡化、制药、饮料和酒生产、工业尾气处理等。一种具有分叉孔道结构分离膜,所述分叉孔结构分离膜的分离层厚度为1-5 μm,膜下表面的开孔是孔径为10-200 μm,自下往上孔道逐渐分叉成小的孔道,最终在靠近分离层处的孔径为0.5-10 μm。本发明利用相转变形成厚度为1-5 μm的皮层作为多孔分离层,与现有的微通道膜和非对称膜相比,分离层厚度减少至不到原来的1/10,大大降低了分离层的过滤阻力。(The invention belongs to the technical field of membranes, and particularly relates to a preparation method and application of a separation membrane with a branched pore passage structure. A separation membrane with a bifurcate pore structure is provided, the thickness of the separation layer of the bifurcate pore structure separation membrane is 1-5 μm, the pore diameter of an opening on the lower surface of the membrane is 10-200 μm, the pore passage is gradually bifurcated into small pore passages from bottom to top, and the pore diameter close to the separation layer is 0.5-10 μm finally. The invention uses the cortex layer with the thickness of 1-5 μm formed by phase transition as the porous separation layer, and compared with the existing microchannel membrane and asymmetric membrane, the thickness of the separation layer is reduced to be less than 1/10, thereby greatly reducing the filtration resistance of the separation layer.)

1. A separation membrane with a bifurcated pore structure is characterized in that the thickness of the separation layer of the bifurcated pore structure is 1-5 mu m, the pore diameter of an opening on the lower surface of the membrane is 10-200 mu m, the pore passage is gradually bifurcated from bottom to top into small pore passages, and finally the pore diameter close to the separation layer is 0.5-10 mu m.

2. A method for preparing the separation membrane according to claim 1, comprising the steps of:

(1) mixing polymer, solvent, dispersant and membrane material powder to form uniform slurry which can be poured;

(2) placing a screen between an upper die and a lower die, pouring the slurry into the dies, and adding a flocculating agent on the slurry for phase transformation to obtain a film blank;

(3) and (3) demolding the membrane blank obtained in the step (2), removing the screen, soaking the membrane blank in water, drying, and sintering to obtain the separation membrane with the branched pore passage structure.

3. The method according to claim 2, wherein the step (2) of injecting the slurry into the mold with the upper surface of the slurry being 0.8 to 4 mm higher than the screen; the sieve mesh of the screen is 10-200 mu m.

4. The method according to claim 2, wherein the phase transition time in step (2) is 0.5 to 3 hours.

5. The preparation method according to claim 2, wherein the sintering in step (3) is carried out by the following specific method: firstly, the film blank is heated to 400 ℃ at the temperature of less than 2 ℃/min, the heat preservation is carried out for 0.5 to 2 hours, the polymer is removed, then the film blank is heated to a certain temperature at the temperature of less than 5 ℃/min, the heat preservation is carried out, and the film blank is sintered to the required mechanical strength.

6. The preparation method according to claim 2, wherein the time for soaking the film blank in water in the step (3) is more than 2 h; the drying is to dry the film blank in an oven to remove water.

7. The preparation method according to claim 2, wherein the mass percentages of the polymer, the solvent, the dispersant and the membrane material in the step (1) are respectively 10-40%, 4-10%, 0.3-1% and 30-85%.

8. The preparation method according to claim 2, wherein the polymer in step (1) is one or more of polyethersulfone, cellulose acetate, polyvinylidene fluoride, polysulfone, polyacrylonitrile, polychromide and polytrigenamine; the solvent is one or more of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, tetrahydrofuran, formylpiperidine and dioxan; the dispersant is polyvinylpyrrolidone, polypropylene alcohol or polyethylene glycol; the membrane material is ceramic powder, polymer, metal powder or carbon powder; the flocculating agent in the step (2) is one or more of water, ethanol and isopropanol.

9. The method of claim 2, wherein the mixing in step (1) is performed by ball milling for more than 24 hours.

10. The use of the separation membrane having a branched pore structure according to claim 1, wherein the separation membrane is applicable to industrial filtration, industrial dust removal, industrial catalysis, and industrial separation.

Technical Field

The invention belongs to the technical field of membranes, and particularly relates to a separation membrane with a branched pore passage structure and a preparation method thereof.

Background

Membrane separation is the filtration separation of liquid or solid from liquid or gas by controlling the pore size of the membrane. The structure of the separation membrane is divided into a separation layer and a support layer according to the functional requirements: the separation layer is provided with pores with controllable sizes, so that liquid or solid is filtered and separated, and the separation layer is generally thin (10-100 mu m) due to the large fluid permeation resistance and high preparation cost; the support layer supports the separation layer, provides the membrane with the required mechanical strength (thickness of 1-3 mm) and enhances the passage of liquids or gases therethrough. The pore structure of the support determines the filtration resistance. For example, the conventional ceramic separation membrane support adopts pore-forming agent to increase porosity and reduce filtration resistance. However, the pore channels formed by the granular pore-forming agent are bent, so that the transmission distance is increased (by 5-20 times), and the direction of the fluid is frequently changed in the transmission process, thereby greatly increasing the filtration resistance. The invention of publication No. CN105188893B discloses a channeled article and method of making the same, which utilizes a mesh screen as a template to guide and normalize the formation of finger-like holes during phase transformation, thereby forming a microchannel structure, and removing the screen to carry away the skin over the screen and open the microchannels. On the other side of the membrane is a porous layer (curved channel) with a traditional structure, the thickness of the porous layer is 10-1000 μm, generally about 100 μm; the patent publication No. CN103638826B discloses an asymmetric ceramic separation membrane and a preparation method thereof, wherein the asymmetric ceramic membrane disclosed in the patent is that a graphite layer is cast on a ceramic slurry layer, finger-shaped holes are formed in the slurry layer after phase transformation is finished, and the finger-shaped holes are opened after the graphite layer is burnt. On the other side of the membrane is a porous layer of 10-1000 μm. Both of these patents utilize micro-channels or finger-like pores formed by phase inversion in a ceramic membrane, with a 10-1000 μm porous layer on the other side of the membrane, which, like conventional porous structures, limits the further reduction of the filtration resistance of the fluid in the ceramic membrane.

The oxygen separation ceramic Membrane (Journal of Membrane Science541 (2017) 653-.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a separation membrane with a branched pore channel structure, and the separation membrane with the branched pore channel structure can reduce the mass transfer resistance and the production energy consumption in membrane separation.

The invention also aims to provide a preparation method of the separation membrane, which is simple to operate, effectively improves the mass transfer rate of the fluid in the supporting layer and reduces the mass transfer resistance of the fluid in the supporting layer.

In order to realize the purpose, the invention adopts the following technical scheme:

a separation membrane with a bifurcate pore structure is provided, the thickness of the separation layer of the bifurcate pore structure separation membrane is 1-5 μm, the pore diameter of an opening on the lower surface of the membrane is 10-200 μm, the pore passage is gradually bifurcated into small pore passages from bottom to top, and the pore diameter close to the separation layer is 0.5-10 μm finally.

A preparation method of the separation membrane comprises the following steps:

(1) mixing polymer, solvent, dispersant and membrane material powder to form uniform slurry which can be poured;

(2) placing a screen between an upper die and a lower die, pouring the slurry into the dies, and adding a flocculating agent on the slurry for phase transformation to obtain a film blank;

(3) and (3) demolding the membrane blank obtained in the step (2), removing the screen, soaking the membrane blank in water, drying, and sintering to obtain the separation membrane with the branched pore passage structure.

Preferably, the step (2) is to inject the slurry into the mould and make the upper surface of the slurry 0.8-4 mm higher than the screen; the sieve mesh of the screen is 10-200 mu m.

Preferably, the phase transition time of step (2) is 0.5 to 3 h.

Preferably, the sintering method in step (3) is as follows: firstly, the film blank is heated to 400 ℃ at the temperature of less than 2 ℃/min, the heat preservation is carried out for 0.5 to 2 hours, the polymer is removed, then the film blank is heated to a certain temperature at the temperature of less than 5 ℃/min, the heat preservation is carried out, and the film blank is sintered to the required mechanical strength.

Preferably, the time for soaking the film blank in water in the step (3) is more than 2 hours; the drying is to dry the film blank in an oven to remove water.

Preferably, the mass percentages of the polymer, the solvent, the dispersant and the membrane material in the step (1) are respectively 10-40%, 4-10%, 0.3-1% and 30-85%.

Preferably, the polymer in the step (1) is one or more of polyether sulfone, cellulose acetate, polyvinylidene fluoride, polysulfone, polyacrylonitrile, polycoolimine and polycoolamine; the solvent is one or more of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, tetrahydrofuran, formylpiperidine and dioxan; the dispersant is polyvinylpyrrolidone, polypropylene alcohol or polyethylene glycol; the membrane material is ceramic powder, polymer, metal powder or carbon powder; the flocculating agent in the step (2) is one or more of water, ethanol and isopropanol.

Preferably, the mixing in step (1) is performed by ball milling for more than 24 hours.

The application of the separation membrane with the branched pore passage structure can be applied to industrial filtration, industrial dust removal, industrial catalysis and industrial separation.

Advantageous effects

(1) The invention uses the cortex layer with the thickness of 0.5-5 μm formed by phase transition as the porous separation layer, and compared with the existing micro-channel membrane and asymmetric membrane, the thickness of the separation layer is reduced to be less than 1/10, thereby greatly reducing the filtration resistance of the separation layer.

(2) Compared with the common micro-channel structure or finger-shaped pore structure, the separation membrane prepared by the invention has the advantages that the dispersion and collection efficiency of fluid (gas or liquid) in the supporting layer is improved, and the mass transfer resistance of the fluid in the supporting layer is reduced.

Drawings

FIG. 1 is a flow chart of the preparation of a separation membrane having a bifurcated pore structure;

FIG. 2 is a schematic view of the formation of phase transition channels in a separation membrane having a bifurcated channel structure;

fig. 3 is a Scanning Electron Micrograph (SEM) image of the alumina ceramic film prepared in example 1, in which 3a is a cross-section of the alumina ceramic film, fig. 3b is an upper surface of the alumina ceramic film, and fig. 3c is a lower surface of the alumina ceramic film;

FIG. 4 is a Scanning Electron Micrograph (SEM) image of the zirconia ceramic membrane prepared in example 2, wherein 4a and 4b are cross-sections of the zirconia ceramic membrane; 4c is the upper part of the section of the zirconia ceramic membrane;

FIG. 5 is an electron micrograph of the pore structure of the inventive separation membranes published under the numbers CN105188893B (a) and CN103638826B (b);

FIG. 6 is an electron micrograph of the pore structure of the presently disclosed oxygen separation ceramic Membrane having a dendritic pore structure (journal of Membrane Science541 (2017), 653-. Fig. 6a and 6b show cross-sections of ceramic membranes. (ii) a

FIG. 7 is a comparison of the air permeability of the alumina ceramic membrane with a branched channel structure prepared by the present invention and the micro-channel alumina ceramic separation membrane prepared by the patent method with publication number CN 105188893B.

FIG. 8 is a comparison of the air permeability of the zirconia ceramic membrane with a branched channel structure prepared by the present invention and the micro-channel zirconia ceramic separation membrane prepared by the patent method with publication number CN 105188893B.

Detailed Description

The above-described aspects of the present invention will be further described in detail by the following examples and comparative examples in order to further understand the features and technical means of the present invention and achieve the specific objects and functions of the present invention. However, it should not be understood that the scope of the present invention as defined above is limited to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.