A multi-zone confined double-scale nanopore mass transfer membrane based on interfacial force regulation and a preparation method thereof

Abstract

The application discloses a multi-zone limited double-scale nanopore mass transfer membrane based on interface force regulation and a preparation method thereof, and belongs to the technical field of nanometer membrane limited mass transfer. Through step-by-step interface polymerization, mask regulation and directional modification, the application realizes precise construction of the membrane layer in the axial direction, and forms a nanopore channel structure with the functions of inlet dehydration, intermediate limited selective mass transfer and outlet rehydration. The double-scale pore structure can effectively reduce the water mass transfer resistance and inhibit the non-selective transport of solutes while reducing the pore size. Compared with a traditional uniform structure membrane, the double-scale pore structure can realize higher water transport efficiency and lower energy consumption while maintaining structural stability.

Description

Technical Field

[0001] This invention belongs to the field of nanomembrane confinement mass transfer technology, and more specifically, relates to a multi-region confinement dual-scale nanoporous mass transfer membrane based on interfacial force regulation and its preparation method. Background Technology

[0002] Nanoconfined membrane mass transfer technology, with its advantages of high efficiency, energy saving, and environmental friendliness, has been widely used in seawater desalination, wastewater treatment, and substance purification. Among them, polyamide (PA) membranes are the core materials for processes such as reverse osmosis (RO) and nanofiltration. Their selective mass transfer performance is mainly limited by multiple factors such as nanopore structure, interfacial interactions, and mechanical stability. However, existing nanoconfined mass transfer membrane technologies face a critical problem in balancing selective mass transfer efficiency and energy consumption for mass transport when treating small-molecule neutral pollutants such as boric acid. On the one hand, boric acid molecules are small, neutral, and easily form hydrogen bonds with water molecules, making it difficult to achieve effective selective transport through traditional static size sieving or charge repulsion mechanisms (traditional polyamide membranes). On the other hand, optimizing membrane pore size or hydrophilicity / hydrophobicity to improve the selectivity of mass transport often sacrifices water transport efficiency or requires higher operating pressures, resulting in a surge in energy consumption and membrane structure failure.

[0003] Existing membrane modification strategies mainly focus on single-dimensional optimization, lacking functional partitioning and mechanical regulation mechanisms along the mass transfer direction within the pores. This results in water molecules and solutes remaining in similar interfacial environments throughout the mass transfer process: on the one hand, hydrogen bonds between water molecules and solutes in the inlet region are difficult to break effectively, leading to solute co-migration with water; on the other hand, the middle section of the pores lacks effective confinement and sieving effects, resulting in insufficient mass transfer selectivity; simultaneously, the water molecule recombination efficiency in the outlet region is low, affecting the overall flux output. For example, introducing polymer chains to adjust the membrane pore structure, regulating pore chemical properties to enhance molecular recognition capabilities, or using hydrophilic coatings to improve water transport efficiency have all failed to address the segmented design of the dynamic characteristics of the mass transfer process.

[0004] Furthermore, single-structure membranes are prone to pore deformation or structural collapse under high-pressure operation, further restricting the long-term stability and reliability of engineering applications. Therefore, there is an urgent need to develop a novel membrane structure capable of synergistically optimizing mass transfer behavior and mechanical stability at the nanoscale. By constructing confined structures with functional partitioning features within the pores, differentiated regulation of water molecules and solutes at different mass transfer stages can be achieved. This would ensure structural stability while reducing energy consumption, breaking through the performance trade-off bottleneck between mass transfer selectivity and mass transport efficiency in traditional membrane materials. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, the technical problem this invention aims to solve is to provide a multi-zone confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation. This nanoporous mass transfer membrane possesses three functional zones: "inlet dehydration - intermediate confinement - outlet rehydration," simultaneously achieving high water transport efficiency, high removal rate of difficult-to-retain neutral solutes, and high salt rejection rate. Another technical problem this invention aims to solve is to provide a method for preparing the aforementioned nanoporous mass transfer membrane. This method involves first forming independent three-zone functional zones through stepwise polymerization, and then utilizing "mask blocking + targeted modifier wetting" to achieve precise regulation of the chemical characteristics of each zone.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation includes the following steps:

[0008] 1) Dissolve 2-isopropyl-1,3-phenylenediamine, triethylamine, and D(+)-10-camphorsulfonic acid in deionized water to obtain aqueous phase A; immerse the pretreated polysulfone substrate in aqueous phase A for monomer adsorption, and then immerse it in organic phase A for interfacial polymerization to obtain a polysulfone-supported substrate film with an inlet region coating.

[0009] 2) Dissolve 2-trifluoromethyl-1,3-phenylenediamine or 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine, triethylamine, D(+)-10-camphorsulfonic acid, and citric acid in deionized water to obtain aqueous phase B; cover the inlet region of the membrane obtained in step 1) with a mask, immerse the middle region of the membrane in aqueous phase B for monomer adsorption, and then immerse it in organic phase B for interfacial polymerization reaction to obtain a polysulfone-supported base membrane containing an inlet region coating and a middle region coating;

[0010] 3) Dissolve 2-(dihydroxyethyl)-1,3-phenylenediamine, triethylamine, and D(+)-10-camphorsulfonic acid in deionized water to obtain aqueous phase C; cover the inlet and middle regions of the membrane obtained in step 2) with a mask, immerse the permeate side of the membrane in aqueous phase C for monomer adsorption, and then immerse it in organic phase C for interfacial polymerization reaction to obtain a polysulfone-supported base membrane containing an inlet coating, a middle coating, and an outlet coating;

[0011] 4) By masking non-target areas, the membrane obtained in step 3) is modified sequentially in the inlet dehydration zone, the confined intermediate zone, and the outlet dehydration zone. The modified membrane is then dried and activated to obtain a nanoporous mass transfer membrane.

[0012] Preferably, in step 1), the mass fraction of 2-isopropyl-1,3-phenylenediamine is 3wt%~3.5wt%, the mass fraction of triethylamine is 2wt%, the mass fraction of D(+)-10-camphorsulfonic acid is 4wt%, and the organic phase A is a 0.12wt% hexane solution of trimesoyl chloride.

[0013] Preferably, in step 1), the time for immersing the polysulfone substrate in aqueous phase A is 30 min, the reaction time for immersing in organic phase A is 30 s, and the interfacial polymerization reaction temperature is 23~27℃.

[0014] Preferably, in step 2), the specific ratio of aqueous phase B and organic phase B is as follows:

[0015] When 2-trifluoromethyl-1,3-phenylenediamine is used, the mass fraction of 2-trifluoromethyl-1,3-phenylenediamine is 3.4 wt%, the mass fraction of triethylamine is 2 wt%, the mass fraction of D(+)-10-camphorsulfonic acid is 4 wt%, and the mass fraction of citric acid is 0.5 wt%; organic phase B is a 0.18 wt% hexane solution of pyromellitic acid chloride.

[0016] When 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine is used, the mass fraction of 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine is 3.4 wt%, the mass fraction of triethylamine is 1 wt%, the mass fraction of D(+)-10-camphorsulfonic acid is 4 wt%, and the mass fraction of citric acid is 0.3 wt%; organic phase B is a 0.2 wt% hexane solution of trimesoyl chloride.

[0017] Preferably, in step 2), the time for immersing the middle region of the membrane in the aqueous phase B is 20-25 min, the reaction time for immersing in the organic phase B is 1-1.5 min, and the interfacial polymerization reaction temperature is 23-27℃.

[0018] Preferably, in step 3), the mass fraction of 2-(dihydroxyethyl)-1,3-phenylenediamine is 3.4 wt%, the mass fraction of triethylamine is 2 wt%, the mass fraction of D(+)-10-camphorsulfonic acid is 4 wt%, and the organic phase C is a 0.1 wt% hexane solution of trimesoyl chloride.

[0019] Preferably, in step 3), the time for immersing the membrane in the aqueous phase C on the permeate side is 30 min, the reaction time for immersing in the organic phase C is 20 s, and the interfacial polymerization reaction temperature is 23~27℃.

[0020] Preferably, in step 4), the specific steps for modifying the obtained membrane sequentially in the inlet dehydration zone, the confined intermediate zone, and the outlet rehydration zone are as follows:

[0021] S1. Modification of the inlet dehydration zone: Cover the confined intermediate zone and the outlet rehydration zone with a mask, immerse the inlet zone of the membrane in a hexane solution of 1~1.5wt% trimethylchlorosilane, react at 25℃ for 20~30 min, then rinse and dry for later use.

[0022] S2, Modification of the confined intermediate region: Replace the mask covering the inlet dehydration zone and outlet rehydration zone of the membrane obtained in step S1, immerse the intermediate region of the membrane in a 0.3~0.5wt% dichloromethane solution of pentafluorobenzoyl chloride or an ethanol solution of 0.3wt% perfluorooctyltriethoxysilane, react at 20~30℃ for 20~30 min, then rinse and dry for later use;

[0023] S3. Modification of the outlet heavy water zone: Remove the full mask and immerse the outlet side of the membrane obtained in step S2 in an ethanol solution of 2~2.5wt% ethylene glycol. React at 40~45℃ for 40~60 min, then rinse and dry to obtain the modified membrane.

[0024] The nanoporous mass transfer membrane prepared by the method described above for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0026] 1) This invention achieves multi-region construction of the membrane layer in the axial direction through stepwise interfacial polymerization combined with mask regulation and directional modification, forming a nanochannel structure with inlet dehydration, intermediate confined mass transfer, and outlet rehydration characteristics. Interfacial force regulation enables different functional regions to form a synergistic force and structural support relationship, which significantly improves the mechanical stability and compressive strength of the membrane while optimizing selective mass transfer behavior. Then, by using "mask blocking + targeted modifier wetting", the modifier reacts only with the active sites of the target region without affecting other regions, and finally achieves precise regulation of the chemical characteristics of each region.

[0027] 2) The dual-scale pore structure of the nanoporous mass transfer membrane prepared by this invention effectively reduces mass transfer resistance and inhibits non-selective solute transport. Compared with traditional homogeneous structure membranes, it achieves higher water transport efficiency while maintaining structural stability, with a neutral solute removal rate of 87%~95% and a NaCl rejection rate of over 99%. It exhibits excellent selective mass transfer performance and operational stability, achieving a triple breakthrough of "high water transport efficiency, high neutral solute removal rate, and high salt rejection rate", solving the problem of "difficulty in balancing water transport efficiency and neutral solute rejection rate" in traditional membranes.

[0028] 3) This invention uses high concentration of trimesoyl chloride to correspond to small pore size in the middle region and low concentration to correspond to large pore size in the inlet / outlet region. By adjusting parameters such as modifier concentration, reaction time, and activation conditions, it can still maintain efficient and selective mass transfer performance, proving that the process parameters of this invention have a wide range of adaptability and can meet the needs of different application scenarios. Attached Figure Description

[0029] Figure 1 The graph shows a comparison of the material transport efficiency and mass transfer energy consumption between Examples 1-6 and Comparative Example 1. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described below with reference to specific embodiments. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] The specific preparation process of the raw materials used in the following examples is as follows:

[0032] 1. Preparation of 2-isopropyl-1,3-phenylenediamine:

[0033] 1) Dissolve 0.1 mol of m-phenylenediamine in 80 mL of anhydrous dichloromethane, purge with nitrogen, add 0.01 mol of anhydrous sodium acetate, cool to 0-5 °C in an ice-water bath, slowly add 0.22 mol of acetic anhydride, and stir at 25 °C for 4 h. After the reaction is complete, add 50 mL of saturated sodium bicarbonate solution to the system, stir to neutralize the residual acetic acid, and then separate, wash, dry, and distill under reduced pressure to obtain N,N'-diacetyl-m-phenylenediamine.

[0034] 2) Mix 0.1 mol N,N'-diacetyl-m-phenylenediamine and 60 mL DMF, purge with nitrogen, add 0.15 mol cesium carbonate and stir for 30 min to activate the amino group, raise the temperature to 35 °C, and slowly add 0.12 mol isopropyl bromide. After the addition is complete, maintain the temperature at 35 °C and stir at 300 r / min for 7 h. After the reaction is complete, pour the system into ice water to precipitate the solid, filter, wash and dry to obtain N,N'-diacetyl-2-isopropyl-1,3-phenylenediamine.

[0035] 3) 0.08 mol N,N'-diacetyl-2-isopropyl-1,3-phenylenediamine and 50 mL 6 mol / L hydrochloric acid were heated under reflux for 6 h. The reaction was monitored by TLC until the starting material was completely eliminated. The mixture was cooled to room temperature and the pH was adjusted to 10-11. A white solid precipitated out. The solid was filtered and the filter cake was recrystallized from anhydrous ethanol to obtain 2-isopropyl-1,3-phenylenediamine.

[0036] 2. Preparation of 2-trifluoromethyl-1,3-phenylenediamine:

[0037] 1) Under nitrogen protection, 0.1 mol of 2-chloro-1,3-dinitrobenzene was dissolved in 100 mL of anhydrous tetrahydrofuran and cooled to 0-5 °C in an ice-water bath; 0.01 mol of tetrabutylamine fluoride in tetrahydrofuran solution was slowly added dropwise while stirring for 10 min; then 0.15 mol of trifluoromethyltrimethylsilane was slowly added dropwise, and after the addition was complete, 0.2 mol of anhydrous potassium carbonate was added, and the reaction was stirred at 25 °C for 8 h. The reaction was quenched by adding 50 mL of saturated ammonium chloride solution to the system, and the mixture was dried by separation and distilled under reduced pressure to obtain a pale yellow solid 2-trifluoromethyl-1,3-dinitrobenzene.

[0038] 2) In a three-necked flask, add 0.08 mol of 2-trifluoromethyl-1,3-dinitrobenzene, 0.6 mol of iron powder, 0.3 mol of ammonium chloride, and 80 mL of anhydrous ethanol. Heat to reflux temperature and react for 6 h. After the reaction is complete, filter while hot to remove iron residue. Distill the filtrate under reduced pressure to remove ethanol. Add 50 mL of distilled water to the residue and extract with dichloromethane. Combine the organic phases and dry with anhydrous sodium sulfate. Finally, remove the solvent by reduced pressure distillation and collect the fraction at 135-140℃ / 0.08 MPa to obtain a colorless, transparent liquid, 2-trifluoromethyl-1,3-phenylenediamine.

[0039] 3. Preparation of 2-(dihydroxyethyl)-1,3-phenylenediamine:

[0040] 1) Take 0.1 mol m-phenylenediamine and 80 mL anhydrous dichloromethane, add 0.01 mol anhydrous sodium acetate under nitrogen protection, dissolve and clarify in an ice-water bath, slowly add 0.22 mol acetic anhydride, keep stirring in an ice-water bath for 30 min, then heat to 25℃ and react for 4 h. After the reaction is complete, add 50 mL saturated sodium bicarbonate solution to neutralize the residual acetic acid, let stand for layering, wash and dry, remove dichloromethane by vacuum distillation at 40℃ and 0.09 MPa, and obtain white needle-like crystals of N,N'-diacetyl-m-phenylenediamine;

[0041] 2) Take 0.1 mol of the product from step 1) and 80 mL of anhydrous DMF, add 0.15 mol of anhydrous cesium carbonate under nitrogen protection, activate at room temperature for 30 min, then raise the temperature to 50 °C, slowly add 0.12 mol of 3-bromo-1,2-propanediol, and after the addition is complete, maintain the temperature at 50 °C and stir at 300 r / min for 8 h. After the reaction is complete, slowly pour the system into 200 mL of ice water and stir vigorously for 10 min. After a white solid precipitates, filter, wash, and dry under vacuum at 50 °C for 4 h to obtain N,N'-diacetyl-2-(1,2-dihydroxyethyl)-1,3-phenylenediamine;

[0042] 3) Take 0.08 mol of the product from step 2) and 50 mL of 6 mol / L hydrochloric acid solution, heat to reflux temperature, react for 6 h, cool to room temperature, slowly adjust the pH value to 10-11, let stand to crystallize, filter, wash, and dry under vacuum at 60 °C and 0.09 MPa for 8 h to obtain white crystals of 2-(dihydroxyethyl)-1,3-phenylenediamine.

[0043] 4. Preparation of 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine:

[0044] 1) Take 0.1 mol m-phenylenediamine and 100 mL anhydrous DCM, replace the air with nitrogen three times, cool to 0-5℃ in an ice-water bath, add 0.25 mol triethylamine dropwise, stir for 10 min, then add 0.22 mol benzoyl chloride dropwise. After the addition is complete, stir at 25℃ for 5 h. Wash the reaction solution with dilute hydrochloric acid and saturated sodium bicarbonate, dry the organic phase, and remove the solvent under reduced pressure to obtain white solid N,N'-dibenzoylm-phenylenediamine;

[0045] 2) Add 0.08 mol of the product from step 1), 0.25 mol of paraformaldehyde and 40 mL of concentrated hydrochloric acid to a 250 mL flask, stir at 60 °C for 8 h, dilute the reaction solution with water and extract with diethyl ether, dry the organic phase to remove the solvent, and obtain a pale yellow solid.

[0046] 3) In a 250 mL pressure-resistant bottle, add 0.06 mol of the product from step 2) above and 60 mL of anhydrous methanol, add 0.25 mol of trimethylamine aqueous solution dropwise, seal and stir at 50 °C for 12 h, remove the solvent under reduced pressure, recrystallize the crude product with anhydrous ethanol to obtain white needle-like crystals of N,N'-dibenzoyl target compound chloride.

[0047] 4) Take 0.04 mol of the crystals from step 3) above and 50 mL of 10% NaOH solution and reflux for 6 h. After cooling, adjust the pH to 7-8, concentrate and crystallize with ethanol, and dry under vacuum to obtain 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine chloride;

[0048] 5) The 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine chloride obtained in step 4) above is dissolved in deionized water to prepare a solution, which is then loaded onto the pretreated OH solution. - A strong basic anion exchange resin column was used as the eluent, and elution was performed with deionized water. The effluent was monitored with silver nitrate reagent until no Cl- was detected. - Detection; collect the eluent containing the target substance, and freeze-dry it to obtain 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine (free quaternary ammonium cationic form).

[0049] Example 1

[0050] A method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation includes the following steps:

[0051] 1) Pretreatment of polysulfone substrate: Select a polysulfone substrate with a thickness of 150μm and a porosity of 45%, and clean it with deionized water and ethanol for 15min each. After drying at 60℃ to constant weight, it is treated with 30W plasma for 5min to obtain the pretreated polysulfone substrate.

[0052] 2) By mass fraction, 3.4 wt% 2-isopropyl-1,3-phenylenediamine, 2 wt% triethylamine, and 4 wt% D(+)-10-camphorsulfonic acid were added to deionized water and stirred at 25°C for 30 min until completely dissolved. The pH was adjusted to 7.2 to obtain aqueous phase A solution. 0.12 wt% trimesoyl chloride was dissolved in hexane and stirred at 25°C for 20 min until uniformly dispersed to obtain organic phase A solution.

[0053] The pretreated polysulfone substrate was first immersed in aqueous phase A for 30 min, drained, and then immersed in organic phase A for 30 s. After the reaction, it was rinsed with hexane and dried at 50 °C for 1.5 h to obtain a polysulfone support film with an inlet region coating.

[0054] 3) By mass fraction, 3.4 wt% 2-trifluoromethyl-1,3-phenylenediamine, 2 wt% triethylamine, 4 wt% D(+)-10-camphorsulfonic acid, and 0.5 wt% citric acid were added to deionized water, and the pH was adjusted to 7.2 to obtain aqueous phase B solution; 0.18 wt% trimesoyl chloride was dissolved in hexane and stirred at 25°C for 20 min until uniformly dispersed to obtain organic phase B solution;

[0055] Cover the inlet region of the membrane obtained in step 2) with a mask, immerse the middle region of the membrane in aqueous phase B for 20 min, drain it and then immerse it in organic phase B for 1 min. After the reaction is completed, rinse with hexane and dry to obtain a polysulfone-supported base membrane containing inlet region coating and middle region coating.

[0056] 4) By mass fraction, 3.4 wt% 2-(dihydroxyethyl)-1,3-phenylenediamine, 2 wt% triethylamine, and 4 wt% D(+)-10-camphorsulfonic acid were added to deionized water, and the pH was adjusted to 7.2 to obtain aqueous phase C solution; 0.1 wt% trimesoyl chloride was dissolved in hexane and stirred at 25°C for 20 min until uniformly dispersed to obtain organic phase C solution;

[0057] Cover the inlet and middle regions of the membrane obtained in step 3) with a mask, immerse the permeate side of the membrane in aqueous phase C for 30 min, drain it, and then immerse it in organic phase C for 20 s. After the reaction is completed, rinse with hexane and dry to obtain a polysulfone-supported base membrane containing inlet coating, middle coating and outlet coating.

[0058] 5) Use a polytetrafluoroethylene mask to precisely cover the confined intermediate zone and the outlet rehydration zone, exposing only the inlet dehydration zone. Align the mask edge with the zone boundary. Immerse the inlet zone of the membrane in a 1 wt% trimethylchlorosilane n-hexane solution, react at 25°C for 30 min with a stirring rate of 50 r / min. Remove the membrane, rinse the inlet zone three times with n-hexane to remove unreacted modifier, rinse the surface with deionized water to remove residual solvent, and then dry.

[0059] Remove the original mask and replace it with a new polytetrafluoroethylene mask to cover the inlet dehydration zone and the outlet rehydration zone, exposing only the confined intermediate zone. Immerse the intermediate zone of the membrane in a 0.5 wt% solution of pentafluorobenzoyl chloride in dichloromethane, react at 20°C for 20 min, rinse the intermediate zone twice with dichloromethane, rinse with deionized water, and then dry.

[0060] Remove the full mask, immerse the outlet side of the obtained membrane in a 2wt% ethylene glycol ethanol solution, react at 40℃ for 1 hour, rinse the outlet area twice with ethanol, rinse with deionized water, and dry at 50℃ for 1.5 hours to obtain the modified membrane.

[0061] 6) The membrane was placed in a dead-end filter tank and activated for 2 hours at 60 bar pressure and 25 °C with simulated seawater containing 32000 ppm NaCl and 5 ppm boric acid, with a stirring rate of 500 r / min, to obtain a nanoporous mass transfer membrane with an inlet / outlet pore size of 0.72 nm and a middle pore size of 0.35 nm.

[0062] Example 2

[0063] A method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation includes the following steps:

[0064] 1) Pretreatment of the polysulfone substrate: completely consistent with step 1) of Example 1;

[0065] 2) Preparation of polysulfone-supported substrate film with inlet region coating: completely consistent with step 2) of Example 1;

[0066] 3) By mass fraction, add 3.4wt% 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine, 1wt% triethylamine, 4wt% D(+)-10-camphorsulfonic acid, and 0.3wt% citric acid to deionized water, stir at 25℃ for 40 min until completely dissolved, and adjust the pH to 6.8-7 to obtain aqueous phase B solution; dissolve 0.2wt% trimesoyl chloride in hexane, stir at 25℃ for 20 min until uniformly dispersed to obtain organic phase B solution;

[0067] Cover the inlet region of the membrane obtained in step 2) with a mask, immerse the middle region of the membrane in aqueous phase B for 25 min, drain it and then immerse it in organic phase B for 1.5 min. After the reaction is completed, rinse it with hexane 3 times and dry it at 45°C for 2 h to obtain a polysulfone-supported base membrane containing inlet region coating and middle region coating.

[0068] 4) Preparation of a polysulfone-supported substrate film containing an inlet region coating, an intermediate region coating, and an outlet region coating: completely consistent with step 4) of Example 1;

[0069] 5) Use a polytetrafluoroethylene mask to precisely cover the confined intermediate zone and the outlet rehydration zone, exposing only the inlet dehydration zone. Align the mask edge with the zone boundary. Immerse the inlet zone of the membrane in a 1 wt% trimethylchlorosilane n-hexane solution, react at 25°C for 30 min with a stirring rate of 50 r / min. Remove the membrane, rinse the inlet zone three times with n-hexane to remove unreacted modifier, rinse the surface with deionized water to remove residual solvent, and then dry.

[0070] Remove the original mask and replace it with a new polytetrafluoroethylene mask to cover the inlet dehydration zone and the outlet rehydration zone, exposing only the confined intermediate zone. Immerse the intermediate zone of the membrane in an ethanol solution of 0.3 wt% perfluorooctyltriethoxysilane, react at 30°C for 30 min, rinse the intermediate zone twice with ethanol, rinse with deionized water, and then dry.

[0071] Remove the full mask, immerse the outlet side of the obtained membrane in a 2wt% ethylene glycol ethanol solution, react at 40℃ for 1 hour, rinse the outlet area twice with ethanol, rinse with deionized water, and dry at 45℃ for 2 hours to obtain the modified membrane.

[0072] 6) The membrane was placed in a dead-end filter tank and activated for 2 hours at 60 bar pressure and 25 °C with simulated seawater containing 32000 ppm NaCl and 5 ppm boric acid, with a stirring rate of 500 r / min, to obtain a nanoporous mass transfer membrane with an inlet / outlet pore size of 0.72 nm and a middle pore size of 0.53 nm.

[0073] Example 3

[0074] In the preparation of the multi-zone confined dual-scale nanoporous mass transfer membrane, in step 5), the middle zone of the membrane is immersed in a 0.3 wt% solution of pentafluorobenzoyl chloride in dichloromethane. The remaining steps and parameters are the same as in Example 1. The nanoporous mass transfer membrane has an inlet / outlet pore size of 0.75 nm and a middle zone pore size of 0.46 nm.

[0075] Example 4

[0076] In the preparation of the multi-region confined dual-scale nanoporous mass transfer membrane, in step 5), the outlet side of the obtained membrane was immersed in an ethanol solution of 2wt% ethylene glycol and reacted at a constant temperature of 40°C for 40 min. The remaining steps and parameters were the same as in Example 1. The nanoporous mass transfer membrane was obtained with an inlet pore size of 0.7 nm, an outlet pore size of 0.78 nm, and a middle pore size of 0.43 nm.

[0077] Example 5

[0078] In the preparation of the multi-zone confined dual-scale nanoporous mass transfer membrane, in step 6), the membrane was activated for 2 hours with simulated seawater containing 32000 ppm NaCl and 8 ppm boric acid at a pressure of 40 bar and a temperature of 25°C. The stirring rate was still 500 r / min. The remaining steps and parameters were the same as in Example 1. The nanoporous mass transfer membrane was obtained with an inlet / outlet pore size of 0.65 nm and an intermediate pore size of 0.41 nm.

[0079] Example 6

[0080] In preparing the multi-region confined dual-scale nanoporous mass transfer membrane, in step 5), the inlet region of the membrane was immersed in a 1.2 wt% trimethylchlorosilane n-hexane solution; in step 6), the activation time was 3 h, and the remaining steps and parameters were the same as in Example 1. The nanoporous mass transfer membrane obtained had an inlet region pore size of 0.7 nm, an outlet region pore size of 0.72 nm, and an intermediate region pore size of 0.36 nm.

[0081] Comparative Example 1

[0082] This comparative example was prepared using the traditional single-step interfacial polymerization method, without segmented polymerization or in-situ modification. The specific steps are as follows:

[0083] (1) Pretreatment of polysulfone substrate: completely consistent with step 1) of Example 1;

[0084] (2) Prepare a homogeneous aqueous solution: Add 3.4 wt% unmodified m-phenylenediamine, 2 wt% triethylamine, and 4 wt% D(+)-10-camphorsulfonic acid to deionized water by mass fraction, stir at 25°C for 30 min until completely dissolved, and adjust the pH to 7.2;

[0085] (3) Prepare a homogeneous organic phase solution: Dissolve 0.15 wt% trimesoyl chloride in hexane and stir at 25°C for 20 min until uniformly dispersed;

[0086] (4) Single-step interfacial polymerization: The pretreated polysulfone substrate was immersed in the above aqueous solution for 30 min, drained and then immersed in the organic solution for 1 min. After the reaction was completed, it was rinsed with hexane and dried.

[0087] (5) Post-processing: The membrane was activated directly according to the activation conditions in step 6) of Example 1 to obtain a traditional uniform polyamide membrane with uniform pore size of about 0.45 nm. The BET test showed only a single peak pore size distribution with no obvious partitioning of large and small pores.

[0088] Example 7

[0089] The performance of the sample films prepared in Examples 1-6 and Comparative Example 1 was tested as follows:

[0090] 1. Sample preparation: Cut the prepared sample films into circular samples with a diameter of 47 mm, soak them in deionized water for 1 hour in advance to remove residual activation solution and impurities on the surface, drain the surface water and set aside.

[0091] 2. Test setup: A dead-end filtration device is used to fix the membrane sample in the filtration tank, ensuring that the membrane and the sealing gasket are tightly bonded and there is no leakage.

[0092] 3. Basic Test Conditions: Except for Example 5, the test conditions for all other samples were uniformly set as follows: operating pressure 60 bar, operating temperature 25°C, feed solution was simulated seawater containing 32000 ppm NaCl and 5 ppm boric acid, feed solution pH adjusted to 7.5, and stirring rate 500 r / min; the test conditions for Example 5 were: operating pressure 40 bar, operating temperature 25°C, feed solution was simulated seawater containing 32000 ppm NaCl and 8 ppm boric acid, pH 7.5, and stirring rate 500 r / min. Test results are as follows... Figure 1 As shown in Table 1.

[0093] Table 1 Performance test results of the sample films prepared in Examples 1-6 and Comparative Example 1

[0094] <![CDATA[Mass transport efficiency (water transport efficiency) (10 -11 m 3 ·m -2 ·s -1 ·Pa -1 )]]> Selective mass transfer efficiency (boric acid removal rate) NaCl retention rate <![CDATA[Mass transfer energy consumption (kWh / m 3 )]]> Example 1 2.82 89.5% 99.25% 0.88 Example 2 2.78 90.2% 99.31% 0.82 Example 3 3.05 88.2% 99.38% 0.85 Example 4 2.91 90.1% 99.40% 0.83 Example 5 2.45 87.6% 99.03% 0.95 Example 6 3.28 95.0% 99.46% 0.74 Comparative Example 1 0.32 71.8% 98.55% 1.35

[0095] Depend on Figure 1 As shown in Table 1, the dual-scale pore structure of the nanoporous mass transfer membrane prepared in this invention effectively reduces water transport resistance and suppresses non-selective solute transport. This invention achieves interfacial force regulation by regionally modifying the physicochemical properties of the membrane microstructure interface. After interfacial force regulation, efficient water-solute selective mass transfer can be achieved while reducing the pore size, overcoming the traditional limitation of low selective mass transfer efficiency when reducing pore size.

[0096] Comparative Example 1, lacking segmented polymerization and partitioned modification, could not form a functional partition of "inlet dehydration - intermediate confinement - outlet rehydration", resulting in difficulty in achieving both water transport efficiency and solute removal rate. In contrast, this invention constructs physical partitions through segmented polymerization and endows precise chemical functions through in-situ modification, achieving synergistic optimization of target substance mass transfer efficiency and selective mass transfer performance between substances.

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation, characterized in that, Includes the following steps: 1) 2-Isopropyl-1,3-phenylenediamine, triethylamine, and D(+)-10-camphorsulfonic acid were dissolved in deionized water to obtain aqueous phase A; the pretreated polysulfone substrate was first immersed in aqueous phase A for monomer adsorption, and then immersed in organic phase A for interfacial polymerization to obtain a polysulfone-supported substrate film with an inlet region coating; the organic phase A was a 0.12 wt% hexane solution of pyromellitic chlorobenzene chloride; 2) Dissolve 2-trifluoromethyl-1,3-phenylenediamine or 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine, triethylamine, D(+)-10-camphorsulfonic acid, and citric acid in deionized water to obtain aqueous phase B; cover the inlet region of the membrane obtained in step 1) with a mask, and immerse the middle region of the membrane sequentially in aqueous phase B for monomer adsorption, and then immerse it in organic phase B for interfacial polymerization reaction to obtain a polysulfone-supported base membrane containing an inlet region coating and a middle region coating; the organic phase B is a hexane solution of 0.18wt% or 0.2wt% pyromellitic acid chloride; 3) Dissolve 2-(dihydroxyethyl)-1,3-phenylenediamine, triethylamine, and D(+)-10-camphorsulfonic acid in deionized water to obtain aqueous phase C; cover the inlet and middle regions of the membrane obtained in step 2) with a mask, immerse the permeate side of the membrane sequentially in aqueous phase C for monomer adsorption, and then immerse it in organic phase C for interfacial polymerization reaction to obtain a polysulfone-supported membrane containing an inlet coating, a middle coating, and an outlet coating; the organic phase C is a 0.1 wt% hexane solution of trimesoyl chloride; 4) By masking non-target areas, the membrane obtained in step 3) is modified sequentially in the inlet dehydration zone, the confined intermediate zone, and the outlet dehydration zone. The modified membrane is then dried and activated to obtain a nanoporous mass transfer membrane. The modification of the inlet dehydration zone is as follows: the confined intermediate zone and the outlet rehydration zone are covered with a mask, the inlet zone of the membrane is immersed in a hexane solution of 1~1.5wt% trimethylchlorosilane, reacted at 25°C for 20~30 min, and then rinsed and dried for later use. The modification of the confined intermediate region is as follows: the inlet dehydration zone and outlet rehydration zone of the membrane obtained by replacing the mask covering are replaced, and the intermediate region of the membrane is immersed in a 0.3~0.5wt% dichloromethane solution of pentafluorobenzoyl chloride or an ethanol solution of 0.3wt% perfluorooctyltriethoxysilane. After reacting at 20~30℃ for 20~30 min, it is rinsed and dried for later use. The modification of the outlet heavy water zone is as follows: remove the full mask, immerse the outlet side of the obtained membrane in an ethanol solution of 2~2.5wt% ethylene glycol, react at 40~45℃ for 40~60 min, and then rinse and dry to obtain the modified membrane.

2. The method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation according to claim 1, characterized in that, In step 1), the mass fraction of 2-isopropyl-1,3-phenylenediamine is 3wt%~3.5wt%, the mass fraction of triethylamine is 2wt%, and the mass fraction of D(+)-10-camphorsulfonic acid is 4wt%.

3. The method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation according to claim 1, characterized in that, In step 1), the time for immersing the polysulfone substrate in aqueous phase A is 30 min, the reaction time for immersing it in organic phase A is 30 s, and the interfacial polymerization reaction temperature is 23~27℃.

4. The method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane with interfacial force modulation according to claim 1, characterized in that, In step 2), the specific ratio of aqueous phase B and organic phase B is as follows: When using 2-trifluoromethyl-1,3-phenylenediamine, the mass fraction of 2-trifluoromethyl-1,3-phenylenediamine is 3.4 wt%, the mass fraction of triethylamine is 2 wt%, the mass fraction of D(+)-10-camphorsulfonic acid is 4 wt%, and the mass fraction of citric acid is 0.5 wt%; organic phase B is a 0.18 wt% hexane solution of pyromellitic acid chloride. Alternatively, when using 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine, the mass fraction of 4,6-bis[(trimethylammonium)methyl]-1,3-phenylenediamine is 3.4 wt%, the mass fraction of triethylamine is 1 wt%, the mass fraction of D(+)-10-camphorsulfonic acid is 4 wt%, and the mass fraction of citric acid is 0.3 wt%; organic phase B is a 0.2 wt% hexane solution of trimesoyl chloride.

5. The method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation according to claim 1, characterized in that, In step 2), the time for immersing the middle region of the membrane in aqueous phase B is 20-25 min, the reaction time for immersing in organic phase B is 1-1.5 min, and the interfacial polymerization reaction temperature is 23-27℃.

6. The method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation according to claim 1, characterized in that, In step 3), the mass fraction of 2-(dihydroxyethyl)-1,3-phenylenediamine is 3.4 wt%, the mass fraction of triethylamine is 2 wt%, and the mass fraction of D(+)-10-camphorsulfonic acid is 4 wt%.

7. The method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation according to claim 1, characterized in that, In step 3), the time for immersing the membrane in the aqueous phase C on the permeate side is 30 min, the reaction time for immersing in the organic phase C is 20 s, and the interfacial polymerization reaction temperature is 23~27℃.

8. A nanoporous mass transfer membrane prepared by the method for preparing a multi-region confined dual-scale nanoporous mass transfer membrane based on interfacial force regulation as described in any one of claims 1-7.

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