Nano-bubble induced amphiphilic compound self-assembled polyamide composite membrane as well as preparation method and application of nano-bubble induced amphiphilic compound self-assembled polyamide composite membrane

Abstract

The invention discloses a nano-bubble induced amphiphilic compound self-assembled polyamide membrane as well as a preparation method and application thereof. The method comprises the following steps: firstly, inducing an amphiphilic imidazole-ureido compound HCx to be self-assembled at a nano bubble-ethanol / water interface by utilizing nano bubbles generated by mixing ethanol and water; thirdly, covering the surface of the solution with an organic phase solution, and promoting separation and crystallization of HCx on the surface of the nanobubble by utilizing the characteristic of low solubility of the HCx in the organic phase solution in the process that the nanobubble migrates from the ethanol / aqueous solution to the organic phase solution, so as to form armored nanobubbles; and finally, carrying out interfacial polymerization reaction on an organic phase solution containing the armored nanobubbles and a water phase solution, constructing a nano cavity in the polyamide separation layer through the armored nanobubbles, and anchoring the HCx artificial water channel nanoparticles around the nano cavity by utilizing a nanobubble carrier, so as to obtain the HCx artificial water channel nanoparticles. Therefore, the polyamide composite membrane rich in nano cavity water channel and HCx artificial water channel nanoparticles is formed, and the water flux and salt rejection rate of the composite membrane are synergistically improved.

Description

TECHNICAL FIELD

[0001] The application discloses a kind of nano bubble induced amphiphilic compound self-assembly polyamide composite membrane and its preparation method and application, belong to separation membrane preparation and application technical field. BACKGROUND

[0002] Self-assembly is one of the effective methods for constructing complex ordered structures in nature and synthetic systems, among which amphiphilic molecules such as surfactants and block copolymers are commonly used self-assembly components, which usually contain hydrophilic head and hydrophobic alkane chain two different functional groups. Their unique self-assembly characteristics provide a micro-reaction domain for the polymerization reaction occurring at the liquid-liquid interface. Interfacial polymerization is a key method for preparing polyamide composite membranes. During the interfacial polymerization process, amine monomers and acyl chloride monomers diffuse from aqueous and organic phase solutions to the interface of the two phases, respectively, and undergo condensation reaction. This mass transfer process is closely coupled with the reaction kinetics at the phase interface. Therefore, subtle changes at the phase interface or in the bulk phase (such as aqueous and organic phases) can affect the interfacial polymerization process and lead to changes in the microstructure and macroscopic properties of the polyamide membrane.

[0003] When amphiphilic molecules meet interfacial polymerization, the monolayer arrangement of the molecules at the liquid-liquid interface and the micellar structure formed by self-assembly in the bulk phase often become the focus of research. Park et al. used the monolayer self-assembly arrangement of amphiphilic surfactant molecules at the interface of the two phases, and through the strong complexation between the surfactant molecules and the amine monomers, the Marangoni instability at the interface was enhanced, and a polyamide separation layer with rich nano-cavities and crumpled structures was constructed (Nano Lett. 2023, 23, 4822-4829). Patent CN 112755817B, a kind of composite nanofiltration membrane with high performance, its preparation method and application, introduces surfactants (diester phosphoric acid compounds) into the organic phase, uses the electrostatic interaction between the compounds and the organic phase monomers and their self-assembly characteristics at the interface, and adjusts the interfacial polymerization process to control the structure of the polyamide separation layer. Different is that patent CN 112892230B, a high desalination polyamide composite reverse osmosis membrane for seawater desalination and its preparation method, uses the synergistic effect between surfactant sodium dodecyl sulfate and triblock ether polymer Pluronic F127 to form a three-dimensional network micellar structure in the aqueous solution, effectively regulating the separation layer structure by affecting the diffusion rate of amine monomers. However, the self-assembly behavior of amphiphilic molecules often affects the interfacial stability during the interfacial polymerization process through direct or indirect ways, which may damage the dense structure of the polyamide separation layer. SUMMARY

[0004] In view of this, the present application proposes a kind of polyamide composite membrane preparation method of nano bubble induced amphiphilic compound self-assembly, first, using the nano bubble generated by ethanol and water mixing induces amphiphilic compound HCx Self-assembly in nano bubble-ethanol / water interface, form nano bubble@HCx;Subsequently, nano bubble is migrated from ethanol / water solution to organic phase solution, using the low solubility characteristics of HCx In organic phase solution, promote the HCx of nano bubble@HCx Surface precipitation and crystallization, form nano bubble@HCx Sub-nanometer artificial water channel in organic phase solution Nanoparticle (i.e. armored nanobubble);Finally, the organic phase solution containing armored nanobubble and aqueous solution are carried out interfacial polymerization reaction, the armored nanobubble is constructed in the polyamide separation layer, and the HCx artificial water channel nanoparticle is anchored around the nanocavity by using the nanobubble carrier, to form the polyamide composite membrane rich in nanocavity water channel and HCx artificial water channel nanoparticle, to improve the water flux and salt rejection rate of the composite membrane.

[0005] To achieve the above object, the present application adopts the following technical solutions:

[0006] A kind of polyamide composite membrane of nano bubble induced amphiphilic compound self-assembly, including support layer and polyamide separation skin layer, nanocavity is distributed in polyamide separation skin layer, HCx artificial water channel nanoparticle is distributed around nanocavity, and HCx structural formula is as follows:

[0007]

[0008] Wherein, R represents linear alkyl of different carbon atom number, including but not limited to any one of butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tetradecyl, octadecyl.

[0009] A kind of polyamide composite membrane preparation method of nano bubble induced amphiphilic compound self-assembly, first, using the nano bubble generated by ethanol and water mixing induces amphiphilic compound HCx Self-assembly in gas-liquid interface, form the directional arrangement structure of hydrophilic group towards solution, hydrophobic group towards bubble interior-nano bubble@HCx;Subsequently, nano bubble@HCx It is migrated to the organic phase solution in its upper layer from ethanol / water solution, using the low solubility characteristics of HCx In organic phase solution, promote the HCx of nano bubble@HCx Surface precipitation and crystallization, form armored nanobubble;Finally, the organic phase solution containing armored nanobubble is covered on the surface of aqueous solution to carry out interfacial polymerization reaction, the armored nanobubble is constructed in the polyamide separation layer, and the HCx artificial water channel nanoparticle is anchored around the nanocavity by using the nanobubble carrier, to form the polyamide composite membrane rich in nanocavity and HCx artificial water channel nanoparticle.

[0010] A method for preparing a polyamide composite membrane by inducing self-assembly of an amphiphilic compound by nanobubbles, specifically comprising the following steps:

[0011] (1) Pre-loading armored nanobubbles in an organic phase solution: first, adding an amphiphilic compound HCx and water into ethanol in sequence; then, covering the surface of the above solution with an organic phase solution containing a polyacyl chloride, promoting rapid mixing of ethanol and water solution by ultrasonic to generate nanobubbles, inducing self-assembly of HCx on the surface of nanobubbles by using the gas-liquid interface of ethanol / water and nanobubbles, forming nanobubble@HCx; at the same time, promoting the transmission of the formed nanobubble@HCx from the ethanol / water solution to the organic phase solution, inducing the HCx on the surface of nanobubbles to precipitate and crystallize in the organic phase solution by using the low solubility characteristics of HCx in the organic phase solution, forming armored nanobubbles, thereby pre-loading armored nanobubbles in the organic phase solution, and absorbing the organic phase solution containing armored nanobubbles and polyacyl chloride on the upper layer of the ethanol and water mixed solution for standby.

[0012] (2) Preparing a polyamide composite membrane: placing a porous support layer in a reaction container, and pouring a water phase solution containing a polyamine and an organic phase solution containing armored nanobubbles and a polyacyl chloride in sequence, after the interfacial polymerization reaction is completed, the solution between the polyamide separation layer and the support layer is filtered out through the support layer by the outlet at the bottom of the reaction container, the polyamide separation layer is loaded on the support layer, and a polyamide composite membrane is obtained after further post-processing.

[0013] The amphiphilic compound HCx in step (1) includes but is not limited to any one of HC4, HC5, HC6, HC7, HC8, HC9, HC10, HC11, HC12, HC14, HC18, the concentration of HCx in the ethanol / water solution is 0.1-2.0wt.%, or any range defined by two numerical values of 0.1wt.%, 0.2wt.%, 0.3wt.%, 0.4wt.%, 0.5wt.%, 0.6wt.%, 0.7wt.%, 0.8wt.%, 0.9wt.%, 1.0wt.%, 1.1wt.%, 1.2wt.%, 1.3wt.%, 1.4wt.%, 1.5wt.%, 1.6wt.%, 1.7wt.%, 1.8wt.%, 1.9wt.%, 2.0wt.%, and preferably 0.2-1.0wt.%.

[0014] The volume ratio of ethanol / water in step (1) is 20 / 80 to 80 / 20, HCx has good solubility in the above volume ratio of ethanol / water solution, the number of ultrasonic is 1-4 times, the ultrasonic time is 1-5 seconds, the ultrasonic power is 100-500W, and the ultrasonic frequency is 10-50kHz.

[0015] The porous support layer in step (2) includes, but is not limited to, any one of polysulfone, polyethersulfone, polyethylene, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polyimide and cellulose acetate.

[0016] The polyamine in step (2) includes, but is not limited to, any one or more of piperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,5-dimethylpiperazine, 2,6-diaminotoluene, 3,5-diaminobenzoic acid, polyethyleneimine, diethylenetriamine, N,N-dimethyl-m-phenylenediamine, and the concentration of the polyamine is 0.25-2.5wt%; the polyacyl chloride includes, but is not limited to, any one or more of trimesoyl chloride, isophthaloyl chloride, fumaryl chloride, malonyl chloride, cyclohexanetricarboxylic acid chloride, cyclopentanetetracarboxylic acid chloride, naphthalene dicarboxylic acid chloride, chlorosulfonyl benzene dicarboxylic acid chloride, tetrahydrofuran dicarboxylic acid chloride, 5-(1-pyrrolidinyl)-isophthaloyl chloride, and the concentration of the polyacyl chloride is 0.05-0.25wt%; and the organic phase solvent is n-hexane.

[0017] The interfacial polymerization reaction time in step (2) is 40-120s, and preferably 45-90s.

[0018] The post-processing process in step (2) includes rinsing and heat treatment of the composite membrane, that is, rinsing the membrane surface with n-hexane, and heat treating the composite membrane at 30-90℃ for 2-5min.

[0019] Compared with the prior art, the present application has the following beneficial effects: (1) Compared with the traditional self-assembly regulation and control interfacial polymerization strategy of amphiphilic molecules, the present application completes the self-assembly of HCx in the pretreatment process, effectively avoiding the influence of the self-assembly of amphiphilic molecules on the stability of the interface in the interfacial polymerization process; (2) Breaking through the limitation of the traditional nanobubble template method which is only used for regulating and controlling the nano-cavity structure, the present application innovatively proposes the nanobubble "one stone three birds" strategy, which not only uses the nanobubble as a template for constructing the nano-cavity, but also uses the nanobubble to induce the self-assembly of the amphiphilic compound HCx, and uses the nanobubble as a carrier to position and load the HCx nanoparticles around the nano-cavity, through the multifunctional synergistic effect of the nanobubble, the controllability of the separation layer structure is significantly improved; (3) Ingeniously using the low solubility characteristics of HCx in the organic phase solution, promoting the precipitation and crystallization of HCx in the organic phase solution, forming HCx sub-nanometer artificial water channel nanoparticles, further improving the water permeability and selectivity of the polyamide composite membrane. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The TEM image of HC7 artificial water channel nanoparticles.

[0021] Figure 2 The SEM images of the surface and cross section of the polyamide layer prepared without introducing HCx for Comparative Example 1.

[0022] Figure 3 Example 2 shows SEM images of the surface and cross-section of the separation layer prepared by nanobubbles@HC6 artificial water channel nanoparticles.

[0023] Figure 4 Example 2: TEM image of the cross-section of the separation layer prepared by nanobubbles@HC6 artificial water channel nanoparticles.

[0024] Figure 5 Example 5 shows SEM images of the surface and cross-section of the separation layer prepared by nanobubbles@HC7 artificial water channel nanoparticles.

[0025] Figure 6 Example 6 shows SEM images of the surface and cross-section of the separation layer prepared by nanobubbles@HC8 artificial water channel nanoparticles.

[0026] Figure 7 This is a schematic diagram illustrating the effect of nanobubbles on the self-assembly of HC7 compounds and the influence of armored nanobubbles on the interfacial polymerization process. Detailed Implementation

[0027] The technical solution will be described in detail below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention and do not represent all embodiments.

[0028] Comparative Example 1:

[0029] A method for preparing a polyamide reverse osmosis membrane, specifically comprising:

[0030] First, the bottom outlet of the reaction vessel was connected to a vacuum pump, and a polysulfone support layer was placed inside the vessel (approximately 40 mm in radius). Next, 2.25 mL of water was added to 0.75 mL of ethanol, and a hexane solution containing 0.1 wt% trimesoyl chloride was placed over the ethanol / water solution. The mixture was sonicated three times, for 3 seconds each time, at a power of 300 W and a frequency of 40 kHz, to promote the mixing of ethanol and water to generate nanobubbles and facilitate their migration into the organic phase solution. Subsequently, the organic solution on top of the ethanol / water mixture was aspirated and allowed to stand for 2 minutes. Then, an aqueous phase solution containing 2.0 wt% m-phenylenediamine (approximately 2.4 mm in height) and the stood organic phase solution (approximately 0.6 mm in height) were added sequentially to the vessel. The interfacial polymerization reaction time was 60 seconds. The solution between the polysulfone support layer and the polyamide separation layer was then filtered out using a vacuum pump. Finally, the polyamide separation layer was removed by lifting, the surface of the composite membrane was rinsed with hexane, and the composite membrane was heat-treated in an 80°C oven for 3 minutes.

[0031] Comparative Example 2:

[0032] A polyamide reverse osmosis membrane preparation method based on HC6 powder, specifically:

[0033] First, connect the bottom outlet of the reaction container to the vacuum pump, and place a polysulfone support layer inside the container (radius about 40 mm); then, sequentially add a 2.0wt% m-phenylenediamine-containing aqueous solution (height about 2.4 mm) and a 0.5wt% HC6 powder + 0.1wt% trimesoyl chloride-containing organic phase solution (height about 0.6 mm) into the container. The interfacial polymerization reaction time is 60 s, and the subsequent experimental conditions are the same as those of Comparative Example 1.

[0034] The preparation method of the amphiphilic compound HC6 is as follows: dissolve 3 mmol of histamine (H) and 3 mmol of hexyl isocyanate (C6) in 2.5 mL of ethyl acetate, 5 mL of acetonitrile, and 5 mL of tetrahydrofuran. Then, heat the above mixture at 80°C for 3 h, and cool to room temperature after the reaction is completed. Subsequently, dissolve the obtained white product in a small amount of ethanol, and add an excess of n-hexane, and stir for 0.5 h to obtain HC6 white powder.

[0035] Example 1:

[0036] A polyamide reverse osmosis composite membrane preparation method for inducing HC6 self-assembly by nanobubbles, specifically:

[0037] First, connect the bottom outlet of the reaction container to the vacuum pump, and place a polysulfone support layer inside the container; then, sequentially add 0.3wt% HC6 powder and 2.25 mL of water into 0.75 mL of ethanol, and cover a n-hexane solution containing 0.1wt% trimesoyl chloride on top of the ethanol / water solution, repeat ultrasonic for 3 times, each time for 3 s, ultrasonic power is 300 W, and frequency is 40 kHz, to promote the generation of nanobubbles by mixing ethanol and water. Subsequently, the amphiphilic compound HC6 self-assembles at the gas-liquid interface (nanobubbles-ethanol / water solution), under the assistance of ultrasonic, the nanobubbles modified by HC6 migrate to the organic phase, forming nanobubble@HC6 artificial water channel nanoparticles, achieving preloading of armored nanobubbles in the organic phase solution; the subsequent experimental steps and conditions are the same as those of Comparative Example 1.

[0038] Examples 2-4:

[0039] The HC6 concentration is 0.5wt%, 0.7wt%, and 0.9wt% respectively, and the remaining experimental conditions are the same as those of Example 1.

[0040] Example 5:

[0041] A polyamide reverse osmosis composite membrane preparation method for inducing HC7 self-assembly by nanobubbles, specifically:

[0042] The rest of the experimental steps and conditions are the same as Example 1 except that 0.5wt% HC6 powder is replaced by 0.5wt% HC7 powder.

[0043] The preparation method of the amphiphilic compound HC7 is as follows: 3 mmol of histamine (H) and 3 mmol of heptyl isocyanate (C7) are dissolved in 2.5 mL of ethyl acetate, 5 mL of acetonitrile and 5 mL of tetrahydrofuran. Then, the above mixture is heated at 80°C for 3h, and after the reaction is completed, it is cooled to room temperature. Subsequently, the white product obtained is dissolved in a small amount of ethanol, and an excess of n-hexane is added, and after stirring for 0.5h, HC7 white powder is obtained.

[0044] Example 6:

[0045] A preparation method of a polyamide reverse osmosis composite membrane induced by HC8 self-assembly of nanobubbles, specifically comprising:

[0046] The rest of the experimental steps and conditions are the same as Example 1 except that 0.5wt% HC6 powder is replaced by 0.5wt% HC8 powder.

[0047] The preparation method of the amphiphilic compound HC8 is as follows: 3 mmol of histamine (H) and 3 mmol of octyl isocyanate (C8) are dissolved in 2.5 mL of ethyl acetate, 5 mL of acetonitrile and 5 mL of tetrahydrofuran. Then, the above mixture is heated at 80°C for 3h, and after the reaction is completed, it is cooled to room temperature. Subsequently, the white product obtained is dissolved in a small amount of ethanol, and an excess of n-hexane is added, and after stirring for 0.5h, HC8 white powder is obtained.

[0048] Test example:

[0049] The test process of the performance of the polyamide reverse osmosis membrane, specifically comprising:

[0050] The reverse osmosis composite membrane is placed in a cross-flow filtration device, the concentration of sodium chloride in the feed liquid is 2000ppm, the operating temperature is 25°C, the pressure is 2MPa, and the effective permeation area of the membrane is 12.56cm 2 , and at least 1h of operation is maintained to keep the permeation flux stable.

[0051] Table 1 is a table of performance data of reverse osmosis membranes prepared by self-assembly of HC6, HC7 and HC8 induced by nanobubbles. The water flux of PA-HC6-0.3% membrane prepared by self-assembly of HC6 induced by nanobubbles is significantly improved compared with the control membrane, which is mainly due to the construction of nanobubble@HC6 artificial water channel nanoparticles and the additional fluid channels provided by HC6 artificial water channel nanoparticles for the transmembrane transport of water molecules. With the increase of HC6 concentration, the number of HC6 sub-nanometer transport channels in PA-HC6-0.5% membrane increases, and the water flux is improved by about 110% compared with the control membrane, while maintaining a high salt rejection rate. When the HC6 concentration is further increased, the water flux of PA-HC6-0.7% and PA-HC6-0.9% membranes gradually decreases, which may be due to the excessive accumulation of HC6 artificial water channel nanoparticles in the separation layer, which limits the transmembrane transport of water molecules due to the strong hydrogen bonding between HC6 artificial water channel nanoparticles and water molecules. In addition, the sub-nanometer structure of HC6 artificial water channel nanoparticles provides additional ion sieving ability for the polyamide separation layer, resulting in a slight increase in the salt rejection rate of PA-HC6 series membranes compared with the control membrane. In contrast, the HC6 compound without self-assembly does not show a significant effect on the performance of the RO membrane. The salt rejection rate of Comparative Example 2 is consistent with that of Comparative Example 1, and the water flux is slightly improved. This result again confirms that the nanobubble@HCx artificial water channel nanoparticles formed by the self-assembly of HCx molecules induced by nanobubbles can effectively improve the performance of the RO membrane (including water flux and salt rejection rate).

[0052] Table 1 Water flux and salt rejection rate of reverse osmosis composite membranes prepared in Comparative Example 1 and Examples 1-6

[0053]

[0054] To analyze the structure of HCx artificial water channel nanoparticles, we took the amphiphilic compound HC7 as an example for research, Figure 1 a shows that the HC7 nanoparticles precipitated in the organic phase solution are hollow nanospheres, which means that nanobubble@HC7 artificial water channel nanoparticles are formed, and further indicates that nanobubbles@HC7 are formed in the ethanol / water solution. At a higher magnification, it can be observed that the edges of HC7 hollow nanospheres are arranged in a short-range ordered periodic arrangement, with a plane spacing of 2.67 and 1.34 nm, respectively, corresponding to the (100) and (200) planes of HCx artificial water channel nanoparticles Figure 1 b).

[0055] After introducing nanobubble@HCx artificial water channel nanoparticles into the interfacial polymerization process, the structure of the separation layer changes significantly. Compared with the control membrane, Figure 2 , the surface of PA-HC6-0.5% membrane is rougher Figure 3), which significantly improved the effective permeation area of the separation layer, and the intrinsic thickness of the separation layer was reduced from 57 nm of the control membrane to 24 nm, effectively reducing the resistance of water molecules to cross the membrane. To analyze the dispersion state of HC6 nanoparticles in the separation layer, the cross-sectional structure of the PA-HC6-0.5% membrane was observed by TEM, Figure 4 showed that HC6 nanoparticles were mainly distributed around the nanobubbles. This result indicated that nanobubbles not only induced the self-assembly of amphiphilic compound HCx, but also served as carriers to load HCx nanoparticles inside the separation layer. These HC6 nanoparticles provided additional fluid channels for the cross-membrane transport of water molecules, and the water permeability of the reverse osmosis membrane was greatly enhanced under the synergistic effect of the separation layer structure optimization and HC6 nanoparticles.

[0056] Thereafter, with the extension of the hydrophobic alkyl chain of HCx, the intrinsic thickness of the PA-HC7-0.5% ( Figure 5 ) and PA-HC8-0.5% membrane ( Figure 6 ) remained almost unchanged, while the apparent thickness gradually increased, resulting in a continuous decrease in the water flux of the membrane (Table 1). The significant change in the thickness of the separation layer may be related to the precipitation process of the amphiphilic compound HCx. In the organic phase solution, HC8 with a long alkyl chain structure continuously precipitates on the surface of the nanobubbles, eventually forming nanoparticles with increased size. These large-sized nanoparticles adsorb on the surface of the nanobubbles, significantly enhancing the stability of the nanobubbles and increasing the concentration of the nanobubbles in the organic phase solution. During the interfacial polymerization process, the high content of nanobubbles promotes the formation of a multilayer nanocavity structure, resulting in an increase in the thickness of the separation layer of the PA-HC8-0.5% membrane, which in turn affects the water flux of the membrane.

[0057] In summary, by adding amphiphilic compound HCx to the ethanol / water solution, nanobubbles can be effectively used to induce the self-assembly of HCx ( Figure 7 a, occurring in ethanol-water); then, the precipitation of HCx in the organic phase solution promotes the formation of nanobubble@HCx artificial water channel nanoparticles (armored nanobubbles) Figure 7 a, occurring in the organic phase); subsequently, armored nanobubbles are used to construct a rich nanocavity in the separation layer, and HCx nanoparticles are anchored around the nanocavity by the nanobubble carrier Figure 7 b), forming a polyamide composite membrane rich in nanocavity water channels and HCx artificial water channel nanoparticles, thereby significantly improving the permeation and separation performance of the polyamide composite membrane.

Claims

1. A polyamide composite film in which nanobubbles induce self-assembly of an amphiphilic compound, characterized by, The polyamide composite membrane comprises a support layer and a polyamide separation skin layer, wherein nanocavities are distributed in the polyamide separation skin layer, and HCx artificial water channel nanoparticles are distributed around the nanocavities, and the HCx has the following structure: In the formula, R represents a linear alkyl group with different carbon atom numbers, and the linear alkyl group includes any one of butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tetradecyl and octadecyl.

2. The method for producing a polyamide composite film in which nano bubbles induce self-assembly of an amphiphilic compound according to claim 1, characterized by, The method comprises the following steps: (1) Pre-loading armored nanobubbles in an organic phase solution: first, adding an amphiphilic compound HCx and water into ethanol in sequence; then, covering an organic phase solution containing a polybasic acid chloride on the surface of the ethanol / water solution, promoting rapid mixing of ethanol and water by ultrasonic to generate nanobubbles, and inducing self-assembly of HCx on the surface of the nanobubbles by using the gas-liquid interface of the nanobubbles and ethanol / water; at the same time, promoting the transmission of the nanobubbles modified by HCx from the ethanol / water solution to the organic phase solution, and inducing the HCx on the surface of the nanobubbles to precipitate and crystallize in the organic phase solution by using the low solubility of HCx in the organic phase solution, so as to form armored nanobubbles, thereby pre-loading armored nanobubbles in the organic phase solution, and absorbing the organic phase solution containing armored nanobubbles and polybasic acid chloride on the upper layer of the ethanol / water mixed solution for standby; (2) Preparing a polyamide composite membrane: placing a porous support layer in a reaction container, and pouring a water phase solution containing a polybasic amine and an organic phase solution containing armored nanobubbles and a polybasic acid chloride in sequence; After the interfacial polymerization reaction is completed, the solution between the polyamide separation layer and the support layer is filtered out through the support layer, and the prepared polyamide separation layer is lifted by using the support layer, and a polyamide composite membrane is obtained through further post-processing.

3. The method for preparing a polyamide composite film in which nano bubbles induce self-assembly of an amphiphilic compound according to claim 2, characterized by, The amphiphilic compound HCx includes any one of HC4, HC5, HC6, HC7, HC8, HC9, HC10, HC11, HC12, HC14 and HC18, and the concentration of HCx in the ethanol aqueous solution is 0.1-2.0 wt.%.

4. The method of claim 2, wherein the polyamide composite film is prepared by a process comprising: (a) dissolving the polyamide compound in a solvent to prepare a solution; (b) adding the nano-bubbles to the solution; (c) applying the solution to a substrate to form a film; and (d) drying the film. In step (1), the volume ratio of ethanol / water is 20 / 80 to 80 / 20, the number of ultrasonic is 1-4 times, the ultrasonic time is 1-5 seconds, the ultrasonic power is 100-500 W, and the ultrasonic frequency is 10-50 kHz.

5. The method of claim 2, wherein the method is characterized by, In step (2), the porous support layer includes any one of polysulfone, polyether sulfone, polyethylene, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polyimide and cellulose acetate.

6. The method of claim 2, wherein the method is characterized by, The polyamine in step (2) includes any one or more of piperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,5-dimethylpiperazine, 2,6-diaminotoluene, 3,5-diaminobenzoic acid, polyethyleneimine, diethylenetriamine, N,N-dimethyl-m-phenylenediamine, and the concentration of the polyamine is 0.25-2.5 wt.%; the polyacyl chloride includes any one or more of trimesoyl chloride, isophthaloyl chloride, fumaryl chloride, malonyl chloride, cyclohexanetricarboxylic acid chloride, cyclopentanetetracarboxylic acid chloride, naphthalene dicarboxylic acid chloride, chlorosulfonyl benzene dicarboxylic acid chloride, tetrahydrofuran dicarboxylic acid chloride, 5-(1-pyrrolidinyl)-isophthaloyl chloride, and the concentration of the polyacyl chloride is 0.05-0.25 wt.%; and the organic phase solvent is n-hexane.

7. The method of claim 2, wherein the method is characterized by, The interfacial polymerization reaction time in step (2) is 40-120 s, and the post-treatment process includes rinsing and heat treatment of the composite membrane, i.e. rinsing the membrane surface with n-hexane, and heat treating the composite membrane at 30-90°C for 2-5 min.

8. Use of the polyamide composite membrane of claim 1, or the polyamide composite membrane prepared by the method of any one of claims 2-7, in a solution desalination process.

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