CN107469639A - Composite nanometer filtering film and preparation method thereof - Google Patents

Abstract

The invention relates to a composite nanofiltration membrane and a preparation method thereof. The preparation method comprises the following steps: adding polyol, binder, surfactant and alkali agent into water, stirring and dissolving to obtain an aqueous phase solution; adding isocyanate monomers to an organic solvent, stirring and dissolving to obtain an organic phase solution; soak the ultrafiltration basement membrane in the aqueous phase solution, then take it out and dry; soak the dried ultrafiltration basement membrane in the organic phase solution for reaction to obtain a pre-finished nanofiltration membrane; The pre-finished nanofiltration membrane is heat-treated at 50-70° C. to obtain the composite nanofiltration membrane. Therefore, the composite nanofiltration membrane prepared by the above preparation method has higher rejection rate and permeation flux. The method of interfacial polymerization simplifies the operation compared with the prior art, the process is easy to control, and it can also overcome the defect that the thickness uniformity of the active layer will be poor and affect the membrane separation performance caused by modification methods such as coating.

Description

Composite nanofiltration membrane and preparation method thereof

technical field

The invention relates to the technical field of membrane separation, in particular to a composite nanofiltration membrane and a preparation method thereof.

Background technique

Membrane separation can be operated under mild conditions without phase transition, and is one of the important technologies in the chemical industry. The core of membrane separation is the membrane, and the structure and physical and chemical properties of the membrane material are crucial to the separation performance. Commonly used membrane materials are polyvinylidene fluoride, polysulfone, polyethersulfone and polyacrylonitrile. These materials have excellent anti-ultraviolet and aging resistance, and good chemical stability. They are not corroded by acids and alkalis at room temperature, and they also have good thermal stability and mechanical strength. They are excellent film-forming materials. However, the disadvantage is that they all have strong hydrophobicity. The hydrophobic nature of the membrane material makes it easy for the separation membrane to absorb proteins, oil droplets, colloids or other organic substances in the water when it is used in water treatment, resulting in blockage of the membrane pores and a rapid decrease in the permeation flux. At the same time, these materials are difficult to modify and extremely The large size restricts the wide application of the membrane. In order to meet production requirements, membrane materials must be functionally modified.

In recent years, some research groups have carried out research on the modification of polysulfone membrane surface in order to solve the problem of the hydrophilicity of polysulfone membrane surface and the poor pollution ability of pits. The current modification research can be roughly divided into blending between organic substances or compounding of organic/inorganic substances. Among them, the method of modifying the membrane material by combining organic/inorganic substances may easily lead to problems such as decreased membrane flux or poor stability due to the difference in compatibility between the two.

As for organic blend membranes and surface modified membranes, such as polyacrylonitrile and polysulfone blend membranes, compared with pure polyacrylonitrile membranes or polysulfone membranes, the water flux of the blend membranes is significantly improved; Chemically modified polysulfone membrane, the amphiphilic block copolymer containing polydimethylaminoethyl methacrylate and polysulfone are used for solution blending, and the composite membrane is prepared by immersion precipitation phase inversion method, which is carried out with bromo acid solution After the surface quaternization treatment, the surface of the membrane has anions and cations, and the hydrophilicity and anti-fouling ability of the membrane are significantly improved. Or use dopamine to modify polysulfone membrane: first modify polysulfone with dopamine and then form a membrane, which can flexibly and conveniently adjust the membrane structure according to the needs of use, and the prepared composite membrane has good backwashing and anti-pollution properties. However, the above method needs to adopt preparation techniques such as casting solution blending phase inversion method, surface modification method or layer-by-layer self-assembly method. The properties have a great correlation; the surface modification method has poor stability and short service life; and the layer-by-layer self-assembly process is complicated and difficult to operate.

Contents of the invention

Based on the above review, it is necessary to provide a preparation method of composite nanofiltration membrane, which is simple to operate, easy to control the process, and the obtained composite nanofiltration membrane has high rejection rate and permeation flux.

A preparation method of a composite nanofiltration membrane, comprising the steps of:

Add polyol, binder, surfactant and alkaline agent into water, stir and dissolve to obtain an aqueous phase solution; wherein, the mass concentration of the polyol is 0.1-5%, and the mass concentration of the binder is 0.1-5% %, the mass concentration of the surfactant is 0.01-1.5%, the mass concentration of the alkali agent is 0.01-1.5%; the molecular weight of the polyol is not more than 2000 Daltons (Da);

Adding the isocyanate monomer into the organic solvent, stirring and dissolving to obtain an organic phase solution; wherein, the mass concentration of the isocyanate monomer is 1-5%;

Soak the ultrafiltration basement membrane in the aqueous phase solution, then take it out and dry it;

The dried ultrafiltration base membrane is soaked in the organic phase solution for reaction to obtain a pre-finished nanofiltration membrane;

The pre-finished nanofiltration membrane is heat-treated at 50-70° C. to obtain the composite nanofiltration membrane.

In one embodiment, the molecular weight of the polyol is 200-1000 Da.

In one of the embodiments, the polyhydric alcohol is ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, neopentyl glycol, glycerol, glycerin, trimethylolethane, One or a mixture of two or more of trimethylolpropane, ethylenediamine pentaerythritol, pentaerythritol, xylitol, sorbitol or polyethylene glycol (PEG). Glycerol and polyethylene glycols are preferred.

In one embodiment, the temperature of the heat treatment is 55-65°C.

In one of the embodiments, the isocyanate monomer is hexamethylene diisocyanate, 4,4-dicyclohexylmethane diisocyanate, trimethylhexane diisocyanate, tetramethylxylylene diisocyanate, isofor One or a mixture of two or more of ketone diisocyanate, diphenylmethane-4,4'-diisocyanate, and toluene diisocyanate. Preference is given to hexamethylene diisocyanate, toluene diisocyanate and diphenylmethane-4,4'-diisocyanate.

In one embodiment, the immersion time of the ultrafiltration basement membrane in the aqueous phase solution is 1-60 min, preferably 20-40 min; the reaction time is 1-60 min, preferably 20-40 min.

In one of the embodiments, the drying temperature is 20-40°C. The drying time is preferably 20-40 minutes.

In one of the embodiments, the organic solvent is n-hexane, cyclohexane, dodecane, heptane, octane, dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone , dimethyl sulfoxide, trifluorotrichloroethane or a mixture of two or more. Preference is given to n-hexane and cyclohexane.

In one of the embodiments, the ultrafiltration base membrane is polyethersulfone, sulfonated polyethersulfone, polysulfone, polyvinylidene fluoride, polyacrylonitrile, polyvinyl chloride, polypropylene, or polyimide any kind. Polysulfone is preferred.

In the present invention, the binder, surfactant and alkaline agent can be selected from binders commonly used in the art, preferably the binder is sodium hydroxymethyl cellulose, and the surfactant is sodium lauryl sulfate , the alkali agent is sodium hydroxide (potassium), organic base (such as triethylamine) and the like.

In the present invention, the composite nanofiltration membrane can be tubular membrane, capillary membrane, spiral wound membrane, flat membrane or hollow fiber membrane.

The invention also provides the composite nanofiltration membrane prepared by the preparation method of the composite nanofiltration membrane.

Principle of the present invention and advantage are as follows:

The preparation method of the composite nanofiltration membrane of the present invention, by sequentially immersing the ultrafiltration base membrane in the aqueous phase solution comprising polyols and the organic phase solution comprising isocyanate monomers, and impelling the two monomers to carry out interfacial polymerization, to Composite polyurethane on ultrafiltration base membrane.

Among them, the concentration of each component in the aqueous phase solution and the organic phase solution is reasonably controlled to promote the polymerization and obtain a suitable polymerization rate. Composite polyurethane with suitable molecular weight on the membrane can obtain better molecular rejection and permeation flux, and the polyurethane contains a large number of hydroxyl groups and has good hydrophilicity. In addition, after the polymerization is completed, the membrane is heat-treated at a specific temperature, which has a pore-closing effect on the active layer of the nanofiltration membrane, and further ensures the rejection rate of the composite nanofiltration membrane.

Therefore, the composite nanofiltration membrane prepared by the above preparation method has higher rejection rate and permeation flux. The method of interfacial polymerization simplifies the operation compared with the prior art, the process is easy to control, and it can also overcome the defect that the thickness uniformity of the active layer will be poor and affect the membrane separation performance caused by modification methods such as coating. In addition, polyurethane has good biocompatibility and is non-toxic, and is a good biological material, so the composite nanofiltration membrane of the present invention has good separation performance for macromolecular PEG.

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

1. The preparation method of the composite nanofiltration membrane of the present invention has the advantages of simple and convenient operation, mild modification conditions and low equipment requirements;

2. The nanofiltration membrane prepared by the preparation method has high rejection rate and permeation flux, good hydrophilic performance, and good separation performance for macromolecular PEG. At the same time, the film layer of composite polyurethane has good mechanical properties, which is beneficial to improve the service life of the film.

3. The preparation method covers the surface of the ultrafiltration base membrane with a lower molecular weight polyurethane layer, which does not damage the structure and performance of the ultrafiltration base membrane. The nanofiltration membrane is suitable for industrial production and application.

detailed description

The composite nanofiltration membrane of the present invention and its preparation method will be further described in detail below in conjunction with specific examples.

The composite nanofiltration membrane prepared by the embodiment of the present invention is used to separate macromolecular organic polymers. The rejection rate (R) and water permeation flux (F) are two important parameters for evaluating the composite nanofiltration membrane. The calculation formula of R is as follows Formula (1) shown.

Among them, R is the rejection rate, c _f is the concentration of the feed solution, and c _p is the concentration of the permeate.

The calculation formula of F is shown in formula (2).

Where, F is the permeate flux (L·m ^-2 ·h ^-1 ), V is the volume of the permeate (L), S is the effective area of the membrane (m ² ), and t is the permeation time (h).

Spectrophotometry is used to separate the concentration of macromolecular organic polymers. For dilute solutions of organic polymers, the absorbance conforms to Lambert-Beer's law. First measure the standard curve, and then calculate the raw material concentration c _f and permeate concentration c _p according to the standard curve equation, and substitute them into the formula (1) for calculation. All films were tested three times, and the results of the three tests were averaged.

Below in conjunction with embodiment the present invention is described in further detail:

Example 1

(1) Weigh PEG 1000 (0.125g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml of deionized water, Heat and stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 1.0 g of hexamethylene diisocyanate and dissolve it in 50 ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove the excess organic phase solution, place the reacted membrane in a constant temperature oven for drying at 60°C, rinse it with water, pre-press and form it, and then conduct a membrane performance test.

The prepared membrane was pre-pressed at 0.6MPa, and the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG1000, PEG6000, and PEG20000 were respectively tested at 0.4MPa and room temperature. The results are shown in Table 1 .

Comparative example 1:

(1) Weigh PEG 1000 (0.125g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml of deionized water, Heat and stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 1.0 g of hexamethylene diisocyanate and dissolve it in 50 ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove excess organic phase solution, rinse the reacted membrane with water directly, pre-press molding, and then perform membrane performance test.

The prepared membrane was pre-compressed with 0.6MPa. Under 0.4MPa and room temperature, the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG 1000, PEG 6000, and PEG 20000 were tested respectively. The obtained results See Table 1.

Comparative example 2

(1) Weigh PEG 1000 (0.125g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml of deionized water, Heat and stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 1.0 g of hexamethylene diisocyanate and dissolve it in 50 ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove the excess organic phase solution, place the reacted membrane in a constant temperature oven for drying at 80°C, rinse it with water, pre-press and form it, and then conduct a membrane performance test.

The prepared membrane was pre-pressed at 0.6MPa, and the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG1000, PEG6000, and PEG20000 were respectively tested at 0.4MPa and room temperature. The results are shown in Table 1 .

Table 1

According to the results in Table 1, it can be seen that heat treatment at an appropriate temperature can further increase the rejection rate of the membrane, and obtain a composite nanofiltration membrane with a higher rejection rate.

Example 2:

(1) Weigh PEG200 (0.125g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml deionized water, heat Stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 1.0 g of hexamethylene diisocyanate and dissolve it in 50 ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove the excess organic phase solution, place the reacted membrane in a constant temperature oven for drying at 60°C, rinse it with water, pre-press and form it, and then conduct a membrane performance test.

The prepared membrane was pre-pressed at 0.6MPa, and the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG1000, PEG6000, and PEG20000 were respectively tested at 0.4MPa and room temperature. The results are shown in Table 2 .

Example 3:

(1) Weigh PEG600 (0.125g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml deionized water, heat Stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 1.0 g of hexamethylene diisocyanate and dissolve it in 50 ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove the excess organic phase solution, place the reacted membrane in a constant temperature oven for drying at 60°C, rinse it with water, pre-press and form it, and then conduct a membrane performance test.

The prepared membrane was pre-pressed at 0.6MPa, and the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG1000, PEG6000, and PEG20000 were respectively tested at 0.4MPa and room temperature. The results are shown in Table 2 .

Comparative example 3:

(1) Weigh PEG2000 (0.125g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml deionized water, heat Stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 1.0 g of hexamethylene diisocyanate and dissolve it in 50 ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove the excess organic phase solution, place the reacted membrane in a constant temperature oven for drying at 60°C, rinse it with water, pre-press and form it, and then conduct a membrane performance test.

The prepared membrane was pre-pressed at 0.6MPa, and the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG1000, PEG6000, and PEG20000 were respectively tested at 0.4MPa and room temperature. The results are shown in Table 2 .

Table 2

According to the results in Table 2, it can be seen that the permeation flux (F) and the rejection rate (R) of the composite nanofiltration membrane with a molecular weight of 2000 Da decreased significantly. In addition, within a certain molecular weight range, composite nanofiltration membranes with different molecular weight cut-offs can be obtained by adjusting the polyol molecules in the aqueous phase solution. The pore size of the composite nanofiltration membrane modified by polyurethane interfacial polymerization is adjustable, and the preparation process is controllable.

Example 4:

(1) Weigh PEG1000 (0.125g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml deionized water, heat Stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 1.0 g of toluene diisocyanate and dissolve it in 50 ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove the excess organic phase solution, place the reacted membrane in a constant temperature oven for drying at 60°C, rinse it with water, pre-press and form it, and then conduct a membrane performance test.

The prepared membrane was pre-pressed at 0.6MPa, and the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG1000, PEG6000, and PEG20000 were respectively tested at 0.4MPa and room temperature. The results are shown in Table 3 .

Example 5:

(1) Weigh PEG1000 (0.125g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml deionized water, heat Stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 1.0g of diphenylmethane-4,4'-diisocyanate and dissolve it in 50ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove the excess organic phase solution, place the reacted membrane in a constant temperature oven for drying at 60°C, rinse it with water, pre-press and form it, and then conduct a membrane performance test.

The prepared membrane was pre-pressed with 0.6MPa, and the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG1000, PEG6000, and PEG20000 were respectively tested at 0.4MPa and room temperature. The results are shown in Table 3 .

table 3

According to the results in Table 3, it can be seen that polyurethane-modified composite nanofiltration membranes with better retention performance can be prepared by using different isocyanates for interfacial polymerization.

Example 6

(1) Weigh PEG 1000 (2.5g), sodium hydroxymethylcellulose (0.125g), sodium lauryl sulfate (0.01g) and sodium hydroxide (0.05g) into 50ml deionized water, Heat and stir to dissolve it completely, then cool to room temperature to obtain an aqueous phase solution;

(2) Soak the polysulfone ultrafiltration base membrane in the aqueous phase solution for 30 minutes;

(3) Remove excess aqueous phase solution, and then place the film in a constant temperature box to dry at 30°C (about 30min);

(4) Measure 2.5g of hexamethylene diisocyanate and dissolve it in 50ml of n-hexane solution to obtain an organic phase solution;

(5) Soak the dried film in the organic phase solution for 30 minutes;

(6) Remove excess organic phase solution, place the reacted film in an oven at 60°C, dry it, rinse it with water, pre-press and form it, and then conduct a film performance test.

The prepared membrane was pre-pressed at 0.6MPa, and the rejection rate (R) and permeation flux (F) of the membrane to 1000ppm PEG1000, PEG6000, and PEG20000 were respectively tested at 0.4MPa and room temperature. The results are shown in Table 4 .

Table 4

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. a kind of preparation method of composite nanometer filtering film, it is characterised in that comprise the following steps：

Polyalcohol, adhesive, surfactant and alkaline agent are added into water, stirring and dissolving, obtain aqueous phase solution；Wherein, it is described The mass concentration of polyalcohol is 0.1~5%, and the mass concentration of binding agent is 0.1~5%, and the mass concentration of surfactant is 0.01~1.5%, the mass concentration of alkaline agent is 0.01~1.5%；The molecular weight of the polyalcohol is less than 2000Da；

Isocyanate-monomer is added into organic solvent, stirring and dissolving, obtains organic phase solution；Wherein, the isocyanates list The mass concentration of body is 1~5%；

Ultrafiltration membranes are soaked in the aqueous phase solution, then takes out, dry；

Ultrafiltration membranes after drying are soaked in the organic phase solution and reacted, obtain NF membrane preform；

The NF membrane preform is heat-treated in 50~70 DEG C；Produce the composite nanometer filtering film.

2. the preparation method of composite nanometer filtering film according to claim 1, it is characterised in that the molecular weight of the polyalcohol is 200~1000Da.

3. the preparation method of composite nanometer filtering film according to claim 2, it is characterised in that the polyalcohol be ethylene glycol, Propane diols, diglycol, triethylene-glycol, neopentyl glycol, glycerine, glycerine, trimethylolethane, trihydroxy methyl third Mixture more than one or both of alkane, ethylenediamine pentaerythrite, pentaerythrite, xylitol, sorbierite or polyethylene glycol.

4. the preparation method of composite nanometer filtering film according to claim 1, it is characterised in that the temperature of the heat treatment is 55 ~65 DEG C.

5. the preparation method of composite nanometer filtering film according to claim 1, it is characterised in that the isocyanate-monomer is six Methylene diisocyanate, 4,4- dicyclohexyl methyl hydride diisocyanates, trimethylhexane diisocyanate, durol diformazan In phenylene diisocyanate, IPDI, diphenyl methane -4,4 '-diisocyanate, toluene di-isocyanate(TDI) One or more kinds of mixtures.

6. the preparation method of the composite nanometer filtering film according to claim any one of 1-5, it is characterised in that soak ultrafiltration membranes It is 1~60min to steep the soak time in the aqueous phase solution；The time of the reaction is 1~60min.

7. the preparation method of the composite nanometer filtering film according to claim any one of 1-5, it is characterised in that the temperature of the drying Spend for 20~40 DEG C.

8. the preparation method of the composite nanometer filtering film according to claim any one of 1-5, it is characterised in that the organic solvent For n-hexane, hexamethylene, dodecane, heptane, octane, dimethyl acetamide, N,N-dimethylformamide, N- crassitudes Mixture more than one or both of ketone, dimethyl sulfoxide (DMSO), trifluorotrichloroethane.

9. the preparation method of the composite nanometer filtering film according to claim any one of 1-5, it is characterised in that the ultrafiltration membranes Material be polyether sulfone, sulfonated polyether sulfone, polysulfones, Kynoar, polyacrylonitrile, polyvinyl chloride, polypropylene or polyimides In any one.

10. composite nanometer filtering film made from the preparation method of the composite nanometer filtering film described in claim any one of 1-9.