CN113318598B

CN113318598B - Method for enhancing selective permeability of reverse osmosis membrane by adjusting pore diameter of base membrane

Info

Publication number: CN113318598B
Application number: CN202110535805.6A
Authority: CN
Inventors: 宋潇潇; 彭磊; 周勇; 高从堦
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Zhejiang University of Technology ZJUT
Priority date: 2021-05-17
Filing date: 2021-05-17
Publication date: 2022-11-11
Anticipated expiration: 2041-05-17
Also published as: CN113318598A

Abstract

The invention discloses a method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the aperture of a base membrane, which comprises the steps of adding sodium dodecyl sulfate with a certain concentration into a casting solution containing polysulfone, coating the casting solution on non-woven fabrics by scraping, and then carrying out phase inversion in a coagulating bath, wherein the exchange speed between a solvent and a non-solvent is accelerated due to the action of a highly hydrophilic end of the sodium dodecyl sulfate, so that the phase inversion speed is converted from delayed phase separation into instantaneous phase separation, thereby generating the base membrane with different aperture sizes, and carrying out interfacial polymerization reaction on an amine monomer dissolved in a water phase and a polyacyl chloride monomer dissolved in an oil phase on the base membrane to compound a polyamide ultrathin layer to form a thin-layer composite reverse osmosis membrane. According to the invention, the base membrane is modified, the pore diameter of the base membrane is increased to a certain extent, the compactness of the separation layer is improved, the water flux and the salt rejection rate of a final membrane product are improved, the selective permeability of the membrane is improved, and a good technical effect is obtained.

Description

Method for enhancing selective permeability of reverse osmosis membrane by adjusting pore diameter of base membrane

Technical Field

The invention relates to the technical field of membranes, in particular to a method for enhancing the selective permeability of a reverse osmosis membrane by adjusting the pore diameter of a base membrane.

Background

Water is a fundamental need for life and health maintenance, and 70.9% of the area is covered by water on the earth, but the real available fresh water resources are extremely limited. In the water resource of the whole world, the seawater which can not be directly drunk accounts for 97.5 percent. In the rest 2.5% of fresh water, 87% of ice and snow in glaciers cannot be directly utilized by human beings. In addition, the fresh water reserve of the underground water is very large, but most of the underground water is too deep from the ground surface, so that the underground water is not beneficial to mining and use. Fresh water resources which can be easily utilized by human beings at present mainly comprise river water, lake water and shallow groundwater. These fresh water reserves only account for 0.3% of the total fresh water. Therefore, the crisis of water resources is not slow enough, and the approaches for solving the problem of shortage of fresh water are many, and can be basically classified into two major approaches, namely 'open source' and 'throttling', and the 'throttling' mainly refers to the implementation of water storage engineering, the implementation of cross-basin water transfer and the like according to the local specific water resource distribution condition. The term "open source" refers to desalination of 97.5% of seawater and brackish water on earth, which cannot be directly drunk.

In a short decades-of-life mile, the seawater desalination technology rapidly rises from the edge industry that is not concerned, and becomes a global hotspot. The traditional seawater desalination technology comprises a distillation method, an ion exchange method, a membrane separation technology and the like.

Membrane separation technology is a new technology of separation that emerged at the beginning of the 20 th century and grew up rapidly after the 60's of the 20 th century. The membrane separation technology has the functions of separation, purification, concentration and refining, has the characteristics of high efficiency, environmental protection, energy conservation, easy control and the like, and can replace some disadvantages of the traditional separation technology in competition, so the membrane separation technology is widely applied to various fields. The reverse osmosis technology is widely applied to the fields of seawater desalination, wastewater treatment, concentrated pharmacy, ultrapure water preparation and the like.

The reverse osmosis technology is a membrane separation technology newly developed in the 60 s. As early as 1953, c.e.reid and e.j.breton found that cellulose acetate had excellent desalting performance and attracted attention. Subsequently, professor Sourirajan and Leob in the united states in 1960 developed the first asymmetric cellulose acetate membrane with high flux, which made reverse osmosis membrane practical and was first commercially produced in gulf universal atomic energy company in san diego, california. Subsequently, in 1978, cadotte forms a membrane composite membrane by selecting trimesoyl chloride and m-phenylenediamine on a polysulfone supporting base membrane for interfacial polymerization, so that another important milestone in the development history of membrane science is formed, and compared with a cellulose acetate membrane prepared by a phase inversion method, a desalting layer of the membrane composite membrane is thinner, so that the transmembrane transmission resistance of water is greatly reduced, and the flux is remarkably improved.

Based on the interfacial polymerization membrane-making method pioneered by Cadotte, a great deal of research has been focused on optimizing the polyamide layer by adjusting monomer concentration, reaction temperature, reaction time, post-treatment conditions, introduction of third-party substances of non-reactive monomers, and the like from the 20 th century to the 80 th. In contrast, the influence of the pore diameter of the base membrane on the separation performance of the polyamide reverse osmosis membrane and the micro-nano structure of the polyamide layer in the interfacial polymerization process is less, and the method has great research value.

Disclosure of Invention

In view of the problems of the prior art, the present invention aims to provide a method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of a base membrane.

The method for enhancing the selective permeability of the reverse osmosis membrane by adjusting the pore diameter of the base membrane is characterized by comprising the following steps of:

1) Preparing a casting solution: adding polysulfone particles into an organic solvent N, N-dimethylformamide, heating and stirring until the particles are completely dissolved, adding sodium dodecyl sulfate, stirring until the particles are completely dissolved to obtain a membrane casting solution, and standing and defoaming the membrane casting solution for later use; wherein, in the prepared membrane casting solution, the concentration of polysulfone is controlled at 12-20%, and the concentration of sodium dodecyl sulfate is controlled at 1-3%;

2) Preparation of a base film: paving a non-woven fabric on a plane glass plate, then uniformly coating the casting solution after defoaming in the step 1) on the non-woven fabric to enable the casting solution to fully soak the non-woven fabric, and uniformly scraping redundant liquid on the surface of the non-woven fabric by adopting a scraper to form a bottom film layer; then putting the bottom film layer into a coagulating bath for phase conversion, gelling into a film with a compact skin layer to prepare a base film, and putting the base film into deionized water for storage;

3) Preparing an aqueous phase solution: adding an amine monomer and an organic weak acid with hydrophilic groups into deionized water, stirring until the amine monomer and the organic weak acid are completely dissolved, and then adding an alkaline substance to adjust the pH value to 9-11.5 to obtain an aqueous phase solution;

4) Preparing an oil phase solution: adding a polyacyl chloride monomer into an organic solvent, and fully stirring until the polyacyl chloride monomer is completely dissolved to obtain an oil phase solution;

5) Preparing a reverse osmosis membrane: fixing the base membrane prepared in the step 2) by using two epoxy resin plate frames, pouring the aqueous phase solution prepared in the step 3) on the fixed base membrane for soaking for a period of time, pouring the aqueous phase solution, vertically placing the plate frames, draining redundant water drops on the surface of the base membrane until no water drops visible to naked eyes exist on the surface, pouring the oil phase solution prepared in the step 4) on the surface of the base membrane for soaking for a period of time, pouring the oil phase solution, drying in an oven to obtain a reverse osmosis membrane product, and putting the prepared reverse osmosis membrane product into deionized water for storage.

The method for enhancing the permselectivity of the reverse osmosis membrane by adjusting the aperture of the base membrane is characterized in that in the membrane casting solution prepared in the step 1), the concentration of polysulfone is controlled to be 14-16%, and the concentration of sodium dodecyl sulfate is 1-2.5%, preferably 2-2.5%.

The method for enhancing the permselectivity of the reverse osmosis membrane by adjusting the aperture of the basement membrane is characterized in that in the step 2), the temperature of a coagulation bath is 0-35 ℃, preferably 20-25 ℃, and the phase inversion time is 0.5-6min, preferably 0.5-1.5min.

The method for enhancing the permselectivity of the reverse osmosis membrane by adjusting the aperture of the base membrane is characterized in that in the step 3), the amine monomer is one of o-phenylenediamine, m-phenylenediamine or p-phenylenediamine, and preferably m-phenylenediamine; the concentration of the amine monomer in the aqueous solution is from 1 to 11%, preferably from 2 to 2.5%.

The method for enhancing the selective permeability of the reverse osmosis membrane by adjusting the pore diameter of the base membrane is characterized in that in the step 3), the organic weak acid is one of citric acid, malic acid or camphorsulfonic acid, and is preferably camphorsulfonic acid; the concentration of the weak organic acid in the aqueous solution is 1-11%, preferably 3.5-5.5%.

The method for enhancing the selective permeability of the reverse osmosis membrane by adjusting the aperture of the base membrane is characterized in that in the step 3), the alkaline substance is sodium hydroxide or triethylamine, preferably triethylamine; the pH in the aqueous solution is adjusted to 9.6-11.2.

The method for enhancing the selective permeability of the reverse osmosis membrane by adjusting the pore diameter of the basement membrane is characterized in that in the step 4), the organic solvent is Isopar-G or n-hexane, preferably n-hexane; the polybasic acyl chloride monomer is paraphthaloyl chloride or trimesoyl chloride, preferably trimesoyl chloride, and the concentration of the polybasic acyl chloride monomer in the oil phase solution is 0.05-0.22%.

The method for enhancing the permselectivity of the reverse osmosis membrane by adjusting the aperture of the basement membrane is characterized in that in the step 5), the water phase solution is poured on the basement membrane for soaking for 0.5-8.5min, preferably 1.5-2.5min.

The method for enhancing the permselectivity of the reverse osmosis membrane by adjusting the aperture of the basement membrane is characterized in that in the step 5), the oil phase solution is poured on the basement membrane for soaking for 0.5-3.5min, preferably 0.5-1.5min.

The method for enhancing the permselectivity of the reverse osmosis membrane by adjusting the aperture of the base membrane is characterized in that in the step 5), the drying temperature in an oven is 50-100 ℃, and the drying time is 1-10min.

In summary, compared with the prior art, the invention has the following beneficial effects:

(1) In the prior art, when the reverse osmosis membrane is optimized and improved, the design idea of the optimization and improvement is that the polyamide layer of the reverse osmosis membrane is optimized by adjusting the concentration of an amine monomer, the concentration of an acyl chloride monomer, the reaction temperature, the reaction time, the post-treatment condition, introducing a third-party substance of a non-reaction monomer and the like, and the optimization and improvement on the base membrane of the reverse osmosis membrane pay less attention. The application removes the performance of regulation and control reverse osmosis membrane from the angle of base film, through adjusting base film aperture reinforcing reverse osmosis membrane permselectivity, has great research value.

(2) When the performance of the reverse osmosis membrane is regulated from the perspective of the base membrane, a membrane casting solution is prepared, sodium dodecyl sulfate with a certain concentration is added into the membrane casting solution, and the sodium dodecyl sulfate is embedded into polysulfone in situ for phase inversion, so that the prepared base membrane has a more reasonable pore structure (namely the pore diameter of the base membrane is increased to a certain degree), and when a polyamide layer is formed by subsequent reaction on the base membrane, the polyamide layer has fewer defects, is more complete and has better crosslinking degree, and meanwhile, the mass transfer resistance to water is reduced, and the application effect is better.

(3) In the preparation process of the reverse osmosis membrane, the reverse osmosis membrane is prepared by modifying the base membrane and then carrying out interfacial polymerization on the base membrane, so that the water flux and the salt rejection rate are improved, the selective permeability of the membrane is improved, and a good technical effect is obtained. The method of the invention provides a modification condition for the polyamide membrane, and provides a favorable foundation for optimizing the permselectivity and industrialization of the polyamide membrane.

Drawings

FIG. 1 is a graph comparing SEM characterization results of the surfaces of base films M-16, S-1, S-1.5, S-2, S-2.5, and S-3 when the base films prepared in step 2) of examples 3 and 5-9 are named base films M-16, S-1, S-1.5, S-2, S-2.5, and S-3, respectively;

FIG. 2 is a comparison graph of SEM characterization results of cross sections of the membrane products M-16 obtained in example 3 and the membrane products S-1, S-1.5, S-2, S-2.5 and S-3 obtained in examples 5 to 9.

Detailed Description

The invention is further illustrated with reference to the following specific examples, without limiting the scope of the invention thereto.

Example 1:

a method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of a base membrane, comprising the steps of:

1) Preparing a casting solution: 1.2g of polysulfone particles (manufactured by Suweiter Polymer Co., ltd., U.S.A.) and 8.8g of an organic solvent N, N-dimethylformamide were put into a round-bottomed flask, and heated and stirred until they were completely dissolved to obtain a casting solution; standing and defoaming the casting solution for 24 hours for later use;

2) Preparation of a base film: paving a non-woven fabric on a plane glass plate, uniformly coating the casting solution after defoaming in the step 1) on the non-woven fabric (the non-woven fabric is produced by Mitsubishi corporation, the same below), fully soaking the non-woven fabric by the casting solution, and uniformly scraping redundant liquid on the surface of the non-woven fabric by adopting a scraper to form a bottom film layer; then putting the base film layer into a coagulating bath for phase transformation, wherein the temperature of the coagulating bath is 25 ℃, the phase transformation time is 1min, gelling is carried out to obtain a film with a compact skin layer, a base film is prepared, and the base film is put into deionized water for storage;

3) Preparation of aqueous phase solution: adding m-phenylenediamine and camphorsulfonic acid into deionized water, controlling the addition concentration of the m-phenylenediamine to be 2.2wt% and the addition concentration of the camphorsulfonic acid to be 4wt%, stirring until the m-phenylenediamine and the camphorsulfonic acid are completely dissolved, and then adding triethylamine to adjust the pH value to 10.0 to obtain an aqueous phase solution;

4) Preparation of oil phase solution: adding 0.11wt% of trimesoyl chloride into an n-hexane organic solvent, and fully stirring until the trimesoyl chloride is completely dissolved to obtain an oil phase solution;

5) Preparing a reverse osmosis membrane: fixing the base membrane prepared in the step 2) by using two epoxy resin plate frames, pouring the water phase solution prepared in the step 3) on the fixed base membrane for infiltration, removing the water phase solution after 2min, vertically placing the plate frames, draining redundant water drops on the surface of the base membrane until no water drops visible to naked eyes exist on the surface, pouring the oil phase solution prepared in the step 4) on the surface of the membrane for infiltration for 30s, pouring the oil phase solution, putting the membrane into a 60 ℃ oven for drying for 1min to obtain a reverse osmosis membrane product, and putting the reverse osmosis membrane product into deionized water for storage, wherein the membrane is named as M-12.

Example 2

Example 2 reverse osmosis membrane preparation process example 1 was repeated except that "step 1) of example 2) was replaced with a process in which 1.4g of polysulfone particles and 8.6g of organic solvent N, N-dimethylformamide were put in a round-bottomed flask, and heated and stirred until completely dissolved to obtain a casting solution; and standing and defoaming the casting solution for 24 hours for later use. The finally obtained membrane was designated by the number M-14.

Example 3

Example 3 preparation of a reverse osmosis membrane example 1 was repeated except that "step 1) of example 3) was replaced with a round-bottomed flask containing 1.6g of polysulfone particles and 8.4g of organic solvent N, N-dimethylformamide, and heated and stirred until completely dissolved to obtain a casting solution; and standing and defoaming the casting solution for 24 hours for later use. The finally obtained membrane was designated by the number M-16.

Example 4

Example 4 preparation of a reverse osmosis membrane example 1 was repeated except that "step 1) of example 4) was replaced with a round-bottomed flask containing 1.8g of polysulfone particles and 8.2g of organic solvent N, N-dimethylformamide, and heated and stirred until completely dissolved to obtain a casting solution; and standing and defoaming the casting solution for 24 hours for later use. The finally obtained membrane was designated by the number M-18.

Example 5:

example 5 preparation of a reverse osmosis membrane example 1 was repeated except that "step 1) of example 5 was replaced with a process in which 1.6g of polysulfone particles and 8.4g of organic solvent N, N-dimethylformamide were placed in a round-bottomed flask, heated and stirred to be completely dissolved, and then 0.1g of sodium dodecyl sulfate was added and stirred to be completely dissolved to obtain a casting solution; and standing and defoaming the casting solution for 24 hours for later use. The finally obtained membrane was designated by the number S-1.

Example 6

Example 6 preparation of a reverse osmosis membrane example 1 was repeated except that "step 1) of example 6 was replaced with a round-bottomed flask containing 1.6g of polysulfone particles and 8.4g of organic solvent N, N-dimethylformamide, and heated and stirred until completely dissolved, and then 0.15g of sodium dodecyl sulfate was added and stirred until completely dissolved to obtain a casting solution; and standing and defoaming the casting solution for 24 hours for later use. The finally obtained membrane was designated by the number S-1.5.

Example 7

Example 7 preparation of a reverse osmosis membrane example 1 was repeated except that "step 1) of example 7) was replaced with a round-bottomed flask containing 1.6g of polysulfone particles and 8.4g of organic solvent N, N-dimethylformamide, and the mixture was heated and stirred until completely dissolved, and then 0.2g of sodium dodecyl sulfate was added and stirred until completely dissolved to obtain a casting solution; and standing and defoaming the casting solution for 24 hours for later use. The finally obtained membrane was designated by the number S-2.

Example 8

Example 8 preparation of a reverse osmosis membrane example 1 was repeated except that "step 1) of example 8) was replaced with a round-bottomed flask containing 1.6g of polysulfone particles and 8.4g of organic solvent N, N-dimethylformamide, and the mixture was heated and stirred until completely dissolved, and then 0.25g of sodium dodecyl sulfate was added and stirred until completely dissolved to obtain a casting solution; and standing and defoaming the casting solution for 24 hours for later use. The finally obtained membrane was designated by the number S-2.5.

Example 9

Example 9 preparation of a reverse osmosis membrane example 1 was repeated except that "step 1) of example 9) was replaced with a round-bottomed flask containing 1.6g of polysulfone particles and 8.4g of organic solvent N, N-dimethylformamide, and the mixture was heated and stirred until completely dissolved, and then 0.3g of sodium dodecyl sulfate was added and stirred until completely dissolved to obtain a casting solution; and standing and defoaming the casting solution for 24 hours for later use. The finally obtained membrane was designated by the number S-3.

The base films prepared in step 2) of examples 3 and 5-9 were SEM-characterized and, for the sake of comparative analysis, the base films prepared in step 2) of examples 3 and 5-9 were designated as base films M-16, S-1, S-1.5, S-2, S-2.5 and S-3, respectively. The SEM characterization results of the membrane surfaces of the base membranes M-16, S-1, S-1.5, S-2, S-2.5 and S-3 are shown in a comparison graph in FIG. 1.

SEM characterization results of the cross sections of the membrane product M-16 obtained in example 3 and the membrane products S-1, S-1.5, S-2, S-2.5 and S-3 obtained in examples 5 to 9 are shown in FIG. 2.

Referring to fig. 1, with the increase of sodium dodecyl sulfate, the pore diameter of the surface of the base membrane shows a tendency of increasing first and then decreasing, because the viscosity of the casting solution is not greatly affected when the concentration of sodium dodecyl sulfate is low, and because the hydrophilic end of sodium dodecyl sulfate accelerates the action between the solvent and the non-solvent, so that instant phase separation is formed, which results in the formation of macropores, and with the continuous increase of sodium dodecyl sulfate, the viscosity of the casting solution becomes large, so that the instant phase separation is converted into delayed phase separation, the phase conversion rate becomes slow, the formation of macropores is inhibited, and the pores on the surface of the membrane gradually decrease.

XPS tests were performed on each of the film products S-1, S-1.5, S-2, S-2.5, and S-3 obtained in examples 5 to 9, to detect the content information of C, N, and O elements within 10nm of the film surface, and the ratio (a) of the oxygen atom content to the nitrogen atom content was calculated from the element content indicated by the scanning results, and the degree of Crosslinking (CD) of the polyamide layer was calculated from the oxygen nitrogen element content ratio, and the calculation formula was: CD = (4-2 a)/(1 + a). The test results are summarized in table 1.

Table 1: analysis result of crosslinking degree of Membrane

As can be seen from table 1 above, as the amount of sodium dodecyl sulfate increases, the degree of crosslinking of the polyamide layer tends to increase first and then decrease, because after the aqueous phase soaks, the base film with the smaller pore size of the aqueous phase remained in the pores of the large-pore-size base film is more, so that in the process of forming the nascent layer of the polyamide layer, the speed of the large pores being completely covered is slower than that of the small pores, which leads to the escape of carbon dioxide in the large pores, and finally leads to fewer defects of the polyamide layer of the large-pore-size base film, more complete, better degree of crosslinking and better interception effect.

The separation performance of the membranes was evaluated in a cross-flow filtration system. A high-concentration NaCl aqueous solution (NaCl concentration: 32000 ppm) was used as a feed solution. Permeate was withdrawn on the other side of the membrane driven by the applied test pressure. The test conditions were set as: the temperature of the feed liquid was 25 ℃, the pH of the feed liquid was 7.5. + -. 0.5, and the test pressure was 5.5MPa. After the membrane is pre-pressed for 1 hour, the permeation selectivity of the membrane is formally tested. The polyamide reverse osmosis membranes prepared in examples 1 to 9 of the present invention were tested by the above-described method, and the results of the membrane performance tests are detailed in the following table 2.

Table 2: membrane permselectivity test

From the data in table 2 above, it can be found that the rejection rate of the reverse osmosis membrane prepared after adding sodium dodecyl sulfate is obviously improved under the condition of almost no loss of water flux compared with the reverse osmosis membrane prepared without adding sodium dodecyl sulfate, and the rejection rate of the corresponding reverse osmosis membrane shows a trend of increasing first and then decreasing along with the increase of the concentration of sodium dodecyl sulfate. The large-aperture base membrane reduces the transmission resistance and path of water compared with the small-aperture base membrane, so that the flux of the reverse osmosis membrane prepared by the large-aperture base membrane is higher than that of the reverse osmosis membrane prepared by the small-aperture base membrane, and the selective permeability of the reverse osmosis membranes prepared by different apertures is different, and the increase of the aperture of the base membrane has a promoting effect on the permeability of the reverse osmosis membrane in a certain range. In the process of preparing the reverse osmosis membrane, the base membranes with smaller pore diameters of the water phase remained in the pores of the base membrane with large pore diameters are more, so that in the process of forming the polyamide layer primary layer, the speed of completely covering the large pores is slower than that of the small pores, carbon dioxide in the large pores escapes partially, and finally the defects of the polyamide layer of the base membrane with large pore diameters are fewer. By combining the section SEM electron microscope image of figure 2 and the cross-linking degree shown in the table 1, the defects of the polyamide layer of the large-aperture base film are fewer and more complete, the cross-linking degree is better, the compactness of the film is better, and therefore the interception effect of the film is better.

The statements in this specification merely set forth a list of implementations of the inventive concept and the scope of the present invention should not be construed as limited to the particular forms set forth in the examples.

Claims

1. A method for enhancing the selective permeability of a reverse osmosis membrane by adjusting the pore size of a base membrane, characterized by comprising the steps of:

3) Preparing an aqueous phase solution: adding an amine monomer and an organic weak acid with a hydrophilic group into deionized water, stirring until the amine monomer and the organic weak acid are completely dissolved, and then adding an alkaline substance to adjust the pH value to 9 to 11.5 to obtain an aqueous phase solution;

5) Preparing a reverse osmosis membrane: fixing the base membrane prepared in the step 2) by using two epoxy resin plate frames, pouring the aqueous phase solution prepared in the step 3) on the fixed base membrane for soaking for a period of time, pouring the aqueous phase solution, vertically placing the plate frames, draining redundant water drops on the surface of the base membrane until no water drops visible to naked eyes exist on the surface, pouring the oil phase solution prepared in the step 4) on the surface of the base membrane for soaking for a period of time, pouring the oil phase solution, drying in an oven to obtain a reverse osmosis membrane product, and putting the prepared reverse osmosis membrane product into deionized water for storage;

in the step 2), the temperature of the coagulation bath is 0-35 ℃, and the phase inversion time is 0.5-6 min;

in the step 3), the amine monomer is one of o-phenylenediamine, m-phenylenediamine or p-phenylenediamine, and the concentration of the amine monomer in the aqueous phase solution is 1-11%;

in the step 3), the organic weak acid is one of citric acid, malic acid or camphorsulfonic acid, and the concentration of the organic weak acid in the aqueous phase solution is 1-11%;

in the step 3), the alkaline substance is sodium hydroxide or triethylamine, and the pH value in the aqueous phase solution is adjusted to 9.6-11.2;

in the step 4), the organic solvent is Isopar-G or n-hexane, the polybasic acyl chloride monomer is paraphthaloyl chloride or trimesoyl chloride, and the concentration of the polybasic acyl chloride monomer in the oil phase solution is 0.05-0.22%.

2. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of a base membrane according to claim 1, wherein the concentration of polysulfone in the membrane casting solution prepared in step 1) is controlled to be 14-16% and the concentration of sodium dodecyl sulfate is 1-2.5%.

3. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of a base membrane according to claim 2, wherein the concentration of sodium dodecyl sulfate in the membrane casting solution prepared in the step 1) is 2 to 2.5%.

4. The method for enhancing permselectivity of reverse osmosis membranes by adjusting pore size of the basement membrane according to claim 1, wherein the coagulation bath temperature is 20-25 ℃ and the phase inversion time is 0.5-1.5min in step 2).

5. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of the base membrane according to claim 1, wherein in step 3), the amine monomer is m-phenylenediamine; the concentration of the amine monomer in the aqueous solution is 2-2.5%.

6. The method of claim 1, wherein in step 3), the weak organic acid is camphorsulfonic acid; the concentration of the weak organic acid in the aqueous solution is 3.5-5.5%.

7. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of the base membrane according to claim 1, wherein in step 3), the basic substance is triethylamine; the pH in the aqueous solution is adjusted to 9.6-11.2.

8. The method for enhancing the permselectivity of reverse osmosis membranes by adjusting the pore size of the basement membrane according to claim 1, wherein in step 4), the organic solvent is n-hexane; the polybasic acyl chloride monomer is trimesoyl chloride.

9. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of the basement membrane according to claim 1, wherein the aqueous solution is poured onto the basement membrane for a soaking time of 0.5 to 8.5min in step 5).

10. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of the base membrane according to claim 9, wherein the aqueous solution is poured onto the base membrane for a soaking time of 1.5 to 2.5min in step 5).

11. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of the basement membrane according to claim 1, wherein the oil phase solution is poured on the basement membrane for a soaking time of 0.5-3.5min in step 5).

12. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of the basement membrane according to claim 11, wherein the oil phase solution is poured on the basement membrane for a soaking time of 0.5 to 1.5min in step 5).

13. The method for enhancing the permselectivity of a reverse osmosis membrane by adjusting the pore size of the base membrane according to claim 1, wherein the drying temperature in the oven is 50-100 ℃ and the drying time is 1-10min in step 5).