CN113041856B - Method for preparing polyamide composite membrane with assistance of hydrophobic oleophylic microporous membrane - Google Patents

Method for preparing polyamide composite membrane with assistance of hydrophobic oleophylic microporous membrane Download PDF

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CN113041856B
CN113041856B CN201911365612.XA CN201911365612A CN113041856B CN 113041856 B CN113041856 B CN 113041856B CN 201911365612 A CN201911365612 A CN 201911365612A CN 113041856 B CN113041856 B CN 113041856B
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membrane
polyamide composite
ultrafiltration membrane
polyamide
microporous
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CN113041856A (en
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王建强
刘富
杨思民
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Ningbo Institute of Material Technology and Engineering of CAS
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Ningbo Institute of Material Technology and Engineering of CAS
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/56—Polyamides, e.g. polyester-amides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B01D2325/028—Microfluidic pore structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/38—Hydrophobic membranes

Abstract

The invention discloses a method for preparing a polyamide composite membrane with the assistance of a hydrophobic oleophylic microporous membrane, which comprises the steps of firstly attaching diamine monomers to a polymer ultrafiltration membrane, then covering the hydrophobic microporous membrane, then immersing the hydrophobic microporous membrane into emulsion prepared from acyl chloride monomers, finally removing the microporous membrane, flushing unreacted compounds on the surface of the polymer ultrafiltration membrane, and then placing the membrane at 55-70 ℃ for heat preservation for 5-15 min. The polyamide composite membrane prepared by the method utilizes the hydrophobic microporous membrane to control the release of acyl chloride monomers, has the characteristics of high controllability of a reaction process, small surface roughness of polyamide, controllable thickness (the thickness can be 10-200nm) of the polyamide layer, no need of an organic solvent bulk solution, better control of the structure and the morphology of the polyamide layer, improvement of the separation performance of the polyamide composite membrane, and reduction of the problem of using a large amount of organic solvents in a membrane preparation process.

Description

Method for preparing polyamide composite membrane with assistance of hydrophobic oleophylic microporous membrane
Technical Field
The invention relates to a preparation method of a separation membrane for substance separation, in particular to a preparation method of a polyamide composite membrane.
Background
Polyamide is currently the core separation layer of separation membranes such as nanofiltration, reverse osmosis and forward osmosis, and the polyamide composite membrane is widely applied to the fields of wastewater treatment, desalination, food industry, biological medicine and the like at present and is a leading product in the market. The polyamide layer is mainly prepared by the traditional interfacial polymerization technology, namely two reactive monomers are respectively dissolved in a water phase (the water phase monomers mainly comprise m-phenylenediamine, piperazine and the like) and an oil phase (the oil phase monomers are usually trimesoyl chloride), then the water phase solution is introduced to the surface of an ultrafiltration support layer, the redundant water phase solution on the surface of an ultrafiltration membrane is removed, then the oil phase solution is introduced to the surface of the ultrafiltration membrane pre-soaked by the water phase solution for interfacial polymerization reaction, and a polyamide separation layer with the thickness of 50-200nm is formed on the surface of the ultrafiltration membrane. Although the preparation technology of the polyamide composite membrane can meet the requirements of a plurality of applications, a large amount of water phase solution and oil phase solution are needed in the preparation process, and simultaneously, a large amount of water phase and oil phase waste liquid can be generated after the reaction is finished due to the low utilization rate of the reaction monomer. In addition, the reaction rate of the amine monomer and the acyl chloride monomer is high, so that the controllability of the process for preparing the polyamide by the interfacial polymerization method is poor. Therefore, the development of a novel polyamide separation layer preparation method and the realization of the greening and controllability of the polyamide preparation process have important significance.
With regard to the controllability of interfacial polymerization for the preparation of polyamide separation layers, various techniques have been reported. For example, Santan Karan et al first deposited 100-120nm thick Cd (OH) on the surface of an ultrafiltration membrane in 20152The controlled release of the aqueous diamine monomer by the nanowire layer, and the controlled release of the nanowire layer to the polyamide preparation in thickness, allows the polyamide separation layer to be less than 10nm thick (Science,2015,348, 1347-1351). In 2017, single and exquisite and the like are sequentially sprayed with an active diamine monomer and an active acyl chloride monomer on a porous supporting layer by a similar layer-by-layer assembly method, and a bulk phase reaction solution is atomized and dispersed into micro liquid drops by spraying, so that bulk phase diffusion is changed into micro phase diffusion, and a high-performance polyamide separation layer is prepared (Chinese patent 201710952970.5). ZHE Tan et al increase the viscosity of the aqueous solution by adding a polyvinyl alcohol polymer to the aqueous solution, thereby reducing the diffusion rate of a diamine monomer in the aqueous solution to the oil phase, and finally realizing the controllable preparation of the surface structure of the polyamide layer (Science,2018,360, 518-521). Maqsud r.chowdhury et al combines the interfacial polymerization technique with the electrostatic spraying technique, and electrostatically sprays the aqueous phase solution and the oil phase solution on the ultrafiltration membrane using the characteristics of electrostatic spraying 3D-like printing, thereby controlling the interfacial polymerization reaction kinetics and the thickness of the polyamide layer, and by this technique, the thickness of the polyamide layer can be accurately controlled on a few nanometers (Science,2018,361, 682-686). Although the preparation method of the polyamide has certain advantages in the aspects of thickness control of the polyamide layer and appearance control of the polyamide, the preparation method has operationComplicated process, low utilization rate of reaction monomers, and generation of a large amount of waste liquid (including waste water and waste organic solvent) containing unreacted monomers.
Disclosure of Invention
Aiming at the problems of poor process controllability, complex structure regulation, low utilization rate of reaction monomers, generation of a large amount of waste liquid and the like in the technology for preparing the polyamide separation layer by interfacial polymerization. The invention provides a novel method for preparing oil-free polyamide assisted by a porous water-proof oil-permeable membrane, which can realize effective control of a polyamide preparation process, greatly reduces the dependence on organic phase solution in the traditional method, and is a more green polyamide preparation method.
The technical scheme of the invention is to provide a method for preparing a polyamide composite membrane with the assistance of a hydrophobic oleophylic microporous membrane, which comprises the following steps:
(1) dissolving diamine monomer in water to prepare aqueous solution with mass concentration of 0.1-5%;
(2) dissolving a polyacyl chloride monomer in an organic solvent to prepare a solution with the mass concentration of 0.1-2%;
(3) dissolving a surfactant in water, wherein the mass concentration of the surfactant is 0.1-2%;
(4) adding the solution obtained in the step (2) into the solution obtained in the step (3), and stirring to prepare a stable oil-in-water emulsion, wherein the concentration of the emulsion is 1-30% (the concentration of the emulsion refers to the mass content of an oil phase in the emulsion);
(5) after the polymer ultrafiltration membrane is tiled, pouring the solution obtained in the step (1) on the polymer ultrafiltration membrane to enable the solution to be in contact with the membrane for 1-10 min; then removing redundant solution on the surface of the polymer ultrafiltration membrane;
(6) paving a hydrophobic microporous membrane on the surface of the polymer ultrafiltration membrane treated in the step (5) to form a double-layer membrane of the polymer ultrafiltration membrane and the microporous membrane, and keeping the double-layer membrane in a flat paving state (the periphery of the double-layer membrane can be fixed or the membrane can be adsorbed on the flat paving surface by utilizing the adsorption effect);
(7) and (3) immersing the double-layer film obtained in the step (6) into the emulsion obtained in the step (4), enabling the film to be in contact with the emulsion for 1-20min, then removing the microporous film, washing the exposed surface of the film by using a corresponding organic solvent, and finally preserving the temperature of the washed film for 5-15min at the temperature of 55-70 ℃ to obtain the polyamide composite film.
Further, in the step (1), the diamine monomer is one or more of piperazine, m-phenylenediamine, p-phenylenediamine and o-phenylenediamine.
Further, the polybasic acyl chloride monomer in the step (2) is one or more of isophthaloyl dichloride, terephthaloyl dichloride, trimesoyl chloride, benzene tetracarboxyl and cyclane polybasic acyl chloride.
Further, in the step (5), the polymer ultrafiltration membrane is at least one of a polysulfone ultrafiltration membrane, a polyethersulfone ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polyvinylidene fluoride ultrafiltration membrane, a polystyrene ultrafiltration membrane or a polyvinyl chloride ultrafiltration membrane.
Further, in the step (5), the microporous membrane is at least one of a polyvinylidene fluoride nanofiber membrane, a polytetrafluoroethylene membrane, a polysulfone nanofiber membrane, a polystyrene nanofiber membrane or a polyvinyl chloride nanofiber membrane.
Furthermore, the microporous membrane in the step (5) is a hydrophobic membrane, the aperture is 0.1-2 μm, and the characteristics can enable the microporous membrane to better play a water-resisting and oil-penetrating role, and the release control of the oil phase in demulsification is good.
The invention has the advantages and beneficial effects that:
the polyamide composite membrane prepared by the method has the characteristics of high controllability in the reaction process, small surface roughness of polyamide, controllable thickness (the thickness can be 10-200nm) of the polyamide layer, no need of an organic solvent bulk solution, better control of the structure and the morphology of the polyamide layer, improvement of the separation performance of the polyamide composite membrane, and reduction of the problem of using a large amount of organic solvent in the membrane preparation process. The technology of the invention has the following characteristic advantages: 1) the use of oil-in-water emulsions eliminates the problem of requiring a large amount of organic phase to participate directly in the conventional interfacial polymerization process; 2) the polymer ultrafiltration membrane is used as a basal membrane, the surface of the polymer ultrafiltration membrane is covered with a microporous membrane, the microporous membrane has hydrophobic property and plays a role in water and oil penetration, micron-sized oil phase droplets in the oil-in-water emulsion reach the surface of the polymer ultrafiltration membrane through diffusion, membrane surface adsorption, emulsion breaking and transfer, and the purpose of oil phase monomer slow release is achieved; 3) the slow release of the oil phase monomer reduces the reaction rate between the diamine and the acyl chloride monomer, thereby being beneficial to the release of reaction heat and finally obtaining a relatively smooth polyamide layer. The polyamide composite membrane prepared by the method can be widely applied to nanofiltration, reverse osmosis and forward osmosis processes.
Drawings
FIG. 1 is a Surface Electron Microscope (SEM) photograph of a polymer ultrafiltration membrane used in examples and comparative examples of the present invention.
Fig. 2 is a Surface Electron Microscope (SEM) photograph of the polyamide composite film prepared in the comparative example.
Fig. 3 is a Surface Electron Microscope (SEM) photograph of the polyamide composite film according to the first embodiment of the present invention.
FIG. 4 is a Surface Electron Microscope (SEM) photograph of the PTFE nanofiber membranes used in examples and comparative examples.
Detailed Description
The present invention will be further described with reference to the following embodiments.
Example one
(1) Dissolving piperazine monomer in water to prepare an aqueous solution with the mass concentration of 0.48%;
(2) dissolving a trimesoyl chloride monomer in n-hexane to prepare a solution with the mass concentration of 0.16%;
(3) dissolving sodium dodecyl benzene sulfonate in water, wherein the mass concentration of the surfactant is 0.2%;
(4) adding the solution obtained in the step (2) into the solution obtained in the step (3), and mechanically stirring to prepare a stable emulsion, wherein the emulsion concentration is 25% (namely the oil phase mass content in the emulsion is 25%);
(5) taking a polysulfone ultrafiltration membrane, flatly paving the polysulfone ultrafiltration membrane on the surface of a carrier (the carrier can be a porous flat plate, a compact ceramic plate, a glass plate and the like), pouring 50mL of the solution obtained in the step (1) on the surface of the polysulfone ultrafiltration membrane to enable the solution to be in contact with the membrane for 10min, and removing the redundant aqueous solution on the surface of the membrane (the redundant aqueous solution on the surface can be poured out by adopting a pouring mode);
(6) tiling a polytetrafluoroethylene nanofiber membrane on the polysulfone ultrafiltration membrane treated in the step (5) to form a polysulfone ultrafiltration membrane-polytetrafluoroethylene nanofiber membrane double-layer membrane, and fixing the double-layer membrane on a carrier in a tiled state; (piperazine monomer is remained at the contact interface between the polysulfone ultrafiltration membrane and the polytetrafluoroethylene nanofiber membrane)
(7) And (3) immersing the double-layer film obtained in the step (6) into 100mL of the emulsion obtained in the step (4), enabling the double-layer film to be in contact with the emulsion for 5min, then removing the polytetrafluoroethylene nanofiber film on the upper layer, washing the exposed film surface with an organic solvent, and finally preserving the temperature of the washed film for 10min at the temperature of 60 ℃ to obtain the polyamide composite film.
In step (7), the bilayer membrane is preferably still fixed on the surface of the carrier when immersed in the emulsion, which helps to maintain the flat state of the bilayer membrane, so that the bilayer membrane is in good contact with the emulsion to facilitate the reaction. After the reaction is finished, the polyamide composite membrane can be taken down from the carrier.
The thickness of the separation layer (i.e. polyamide layer formed by reaction) of the obtained polyamide composite membrane is 50nm, and the separation layer is used for 1000mg/L Na under the cross-flow condition and the external 5bar pressure2SO4The solution has 95 percent of retention performance and has the penetration flux of 35Lm to water-2h-1。
Example two
(1) Dissolving piperazine monomer in water to prepare an aqueous solution with the mass concentration of 5%;
(2) dissolving a trimesoyl chloride monomer in n-hexane to prepare a solution with the mass concentration of 1.6%;
(3) dissolving sodium dodecyl benzene sulfonate in water, wherein the mass concentration of the surfactant is 1%;
(4) adding the solution obtained in the step (2) into the solution obtained in the step (3), and mechanically stirring to prepare a stable emulsion, wherein the emulsion concentration is 10% (namely the oil phase mass content in the emulsion is 10%);
(5) flatly paving a polysulfone ultrafiltration membrane on the surface of a porous carrier, pouring 50mL of the solution obtained in the step (1) on the surface of the polysulfone ultrafiltration membrane to enable the solution to be in contact with the membrane for 10min, and then removing the redundant aqueous solution on the surface of the membrane;
(6) spreading a polytetrafluoroethylene nanofiber membrane on the polysulfone ultrafiltration membrane treated in the step (5) to form a polysulfone ultrafiltration membrane-polytetrafluoroethylene nanofiber membrane double-layer membrane, and fixing the double-layer membrane on a carrier in a spread state; (piperazine monomer is remained at the contact interface between the polysulfone ultrafiltration membrane and the polytetrafluoroethylene nanofiber membrane)
(7) Immersing the double-layer film obtained in the step (6) into 100mL of the emulsion obtained in the step (4), enabling the double-layer film to be in contact with the emulsion for 2min, then removing the polytetrafluoroethylene nanofiber film on the upper layer, washing the exposed film surface with a corresponding organic solvent, and finally preserving the temperature of the washed film for 10min at the temperature of 60 ℃ to obtain a polyamide composite film;
the thickness of the separation layer (i.e. polyamide layer formed by reaction) of the obtained polyamide composite membrane is 200nm, and the separation layer is used for 1000mg/L Na under the cross-flow condition and the external 5bar pressure2SO4Has 99.9 percent of retention performance and 17Lm of permeation flux to water-2h-1。
EXAMPLE III
(1) Dissolving piperazine monomer in water to prepare an aqueous solution with the mass concentration of 0.12%;
(2) dissolving a trimesoyl chloride monomer in n-hexane to prepare a solution with the mass concentration of 0.1%;
(3) dissolving sodium dodecyl sulfate in water, wherein the mass concentration of the surfactant is 0.1%;
(4) adding the solution obtained in the step (2) into the solution obtained in the step (3), and mechanically stirring to prepare a stable emulsion, wherein the emulsion concentration is 30% (namely the oil phase mass content in the emulsion is 30%);
(5) flatly paving a polysulfone ultrafiltration membrane on the surface of a porous carrier, pouring 50mL of the solution obtained in the step (1) on the surface of the polysulfone ultrafiltration membrane to enable the solution to be in contact with the membrane for 10min, and then removing the redundant aqueous solution on the surface of the membrane;
(6) tiling a polytetrafluoroethylene nanofiber membrane on the polysulfone ultrafiltration membrane treated in the step (5) to form a polysulfone ultrafiltration membrane-polytetrafluoroethylene nanofiber membrane double-layer membrane, and fixing the double-layer membrane on a carrier in a tiled state; (piperazine monomer is remained at the contact interface between the polysulfone ultrafiltration membrane and the polytetrafluoroethylene nanofiber membrane)
(7) And (3) immersing the double-layer membrane obtained in the step (6) into 100mL of the emulsion obtained in the step (4), enabling the double-layer membrane to be in contact with the emulsion for 20min, then removing the polytetrafluoroethylene nanofiber membrane on the upper layer, washing the exposed membrane surface with a corresponding organic solvent, and finally preserving the temperature of the washed membrane for 10min at the temperature of 60 ℃ to obtain the polyamide composite membrane.
The thickness of the separation layer (i.e. polyamide layer formed by reaction) of the obtained polyamide composite membrane is 10nm, and the separation layer is used for 1000mg/L Na under the cross-flow condition and the external 5bar pressure2SO4Has 60 percent of retention performance and 60Lm of permeation flux to water-2h-1。
Example four
(1) Dissolving an o-phenylenediamine monomer in water to prepare an aqueous solution with the mass concentration of 2%;
(2) dissolving a trimesoyl chloride monomer in n-hexane to prepare a solution with the mass concentration of 0.5%;
(3) dissolving sodium dodecyl benzene sulfonate in water, wherein the mass concentration of the surfactant is 0.2%;
(4) adding the solution obtained in the step (2) into the solution obtained in the step (3), and mechanically stirring to prepare a stable emulsion, wherein the emulsion concentration is 25% (namely the oil phase mass content in the emulsion is 25%);
(5) flatly paving a polysulfone ultrafiltration membrane on the surface of a compact ceramic plate, pouring 50mL of the solution obtained in the step (1) on the surface of the polysulfone ultrafiltration membrane to enable the solution to be in contact with the membrane for 10min, and then removing the redundant aqueous solution on the surface of the membrane;
(6) spreading a polytetrafluoroethylene nanofiber membrane on the polysulfone ultrafiltration membrane treated in the step (5) to form a polysulfone ultrafiltration membrane-polytetrafluoroethylene nanofiber membrane double-layer membrane, and fixing the double-layer membrane on a carrier in a spread state; (piperazine monomer is remained on the contact interface between the polysulfone ultrafiltration membrane and the polytetrafluoroethylene nanofiber membrane);
(7) and (5) immersing the double-layer film obtained in the step (6) into 100mL of the emulsion obtained in the step (4), contacting the double-layer film with the emulsion for 5min, then removing the polytetrafluoroethylene nanofiber film on the upper layer, washing the exposed film surface with an organic solvent, and finally preserving the temperature of the washed film for 10min at the temperature of 60 ℃ to obtain the polyamide composite film.
The thickness of the separation layer (i.e. polyamide layer formed by reaction) of the obtained polyamide composite membrane is 60nm, and the separation layer is used for 1000mg/L Na under the cross-flow condition and the external 10bar pressure2SO4Has 99 percent of retention performance and 15Lm of permeation flux to water-2h-1。
Comparative example
(1) Dissolving piperazine monomer in water to prepare an aqueous solution with the mass concentration of 0.48%;
(2) dissolving a trimesoyl chloride monomer in n-hexane to prepare a solution with the mass concentration of 0.16%;
(3) flatly spreading a polysulfone ultrafiltration membrane on the surface of a porous carrier, pouring 50mL of the solution obtained in the step (1) on the surface of the polysulfone ultrafiltration membrane to enable the solution to be in contact with the membrane for 10min, and then removing the redundant aqueous solution on the surface of the membrane;
(4) pouring 100mL of the solution obtained in the step (2) onto the membrane obtained in the step (3), removing unreacted solution after contacting for 2 minutes, washing the surface of the membrane by using a corresponding organic solvent, and finally, preserving the temperature of the ultrafiltration membrane at 60 ℃ for 10 minutes to obtain a polyamide composite membrane;
the separation layer of the obtained polyamide composite membrane has a thickness of 125nm and can be used for 1000mg/L Na under the conditions of cross flow and an external pressure of 5bar2SO4Has 98 percent of retention performance and 22Lm of permeation flux to water-2h-1。
FIG. 1 is a surface electron microscope photograph of a polysulfone ultrafiltration membrane used in the above examples and comparative examples, FIG. 2 is a surface electron microscope photograph of a polyamide composite membrane prepared in the comparative examples, FIG. 3 is a surface electron microscope photograph of a polyamide composite membrane prepared in the first example of the present invention, and composite membranes prepared in other examples have similar morphologies, thus only exemplifying the first example, and FIG. 4 is a surface electron microscope photograph of a polytetrafluoroethylene nanofiber membrane used in the above examples and comparative examples. The polyamide composite membrane prepared by the preparation method can be used for preparing a composite membrane with the thickness of the polyamide layer within the range of 10-200nm, a large amount of organic solvent bulk solution is not needed to be directly used, the structure and the shape of the polyamide layer can be better controlled, the separation performance of the polyamide composite membrane is improved, and the problem that a large amount of organic solvent is used in the membrane preparation process is solved, as shown in figures 2 and 3. Specifically, 1) in the traditional interfacial polymerization process, after a water phase is attached to a support body, an organic phase is directly contacted with the attached water phase so as to react on the surface of the support body, due to the influence of factors such as reaction heat, organic phase flow and the like, the traditional interfacial polymerization reaction has poor controllability, the use amount of the organic phase is large, and reaction waste liquid is more; 2) the invention takes the polymer ultrafiltration membrane shown in figure 1 as a basal membrane, the surface of the polymer ultrafiltration membrane is covered with the microporous membrane shown in figure 4, the microporous membrane has a pore diameter of 0.1-2 mu m and has hydrophobicity, namely the water contact angle of the microporous membrane generally requires more than 90 degrees, and the microporous membrane can be used for resisting water and penetrating oil, when an oil-in-water emulsion contacts the microporous membrane, the microporous membrane breaks the coating of a surfactant in the emulsion on an oil phase, so that micron-sized oil phase droplets become free oil drops without being coated by the surfactant, namely the oil phase in the oil-in-water emulsion reaches the surface of the polymer ultrafiltration membrane through diffusion, membrane surface adsorption, emulsion breaking and transmission and can be subjected to polymerization reaction with a diamine monomer staying on the surface of the polymer ultrafiltration membrane, and the microporous membrane has a control effect on the release of the oil phase monomer; 3) the slow release or controlled release of the oil phase monomer reduces the reaction rate between the diamine and the acyl chloride monomer, thereby facilitating the release of the reaction heat, making the reaction process smooth and mild, and finally obtaining a relatively smooth polyamide layer, as shown in fig. 3.
Materials, reagents and experimental equipment related to the embodiments of the present invention are commercially available products conforming to the field of separation membrane preparation unless otherwise specified.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, modifications and decorations can be made without departing from the core technology of the present invention, and these modifications and decorations shall also fall within the protection scope of the present invention. Any changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (6)

1. The method for preparing the polyamide composite membrane with the assistance of the hydrophobic oleophylic microporous membrane is characterized by comprising the following steps of:
(1) dissolving diamine monomer in water to prepare aqueous solution with mass concentration of 0.1-5%;
(2) dissolving a polyacyl chloride monomer in an organic solvent to prepare a solution with the mass concentration of 0.1-2%;
(3) dissolving a surfactant in water, wherein the mass concentration of the surfactant is 0.1-2%;
(4) adding the solution obtained in the step (2) into the solution obtained in the step (3), and stirring to prepare a stable oil-in-water emulsion, wherein the concentration of the emulsion is 1-30%;
(5) after the polymer ultrafiltration membrane is tiled, pouring the solution obtained in the step (1) on the polymer ultrafiltration membrane to enable the solution to be in contact with the membrane for 1-10 min; then removing the redundant solution on the surface of the polymer ultrafiltration membrane;
(6) paving a hydrophobic microporous membrane on the surface of the polymer ultrafiltration membrane treated in the step (5) to form a double-layer membrane of the polymer ultrafiltration membrane and the microporous membrane, and keeping the double-layer membrane in a flat paving state;
(7) and (3) immersing the double-layer film obtained in the step (6) into the emulsion obtained in the step (4), enabling the film to be in contact with the emulsion for 1-20min, then removing the microporous film, washing the exposed surface of the film by using a corresponding organic solvent, and finally preserving the temperature of the washed film for 5-15min at the temperature of 55-70 ℃ to obtain the polyamide composite film.
2. The method for preparing the polyamide composite membrane with the assistance of the hydrophobic lipophilic microporous membrane according to claim 1, wherein the diamine monomer in step (1) is one or more of piperazine, m-phenylenediamine, p-phenylenediamine and o-phenylenediamine.
3. The method for preparing the polyamide composite membrane with the assistance of the hydrophobic lipophilic microporous membrane according to claim 1, wherein the polyacyl chloride monomer in the step (2) is one or more of isophthaloyl chloride, terephthaloyl chloride, trimesoyl chloride, pyromellitic benzoyl and cycloalkane polyacyl chloride.
4. The method for preparing the polyamide composite membrane with the assistance of the hydrophobic and oleophylic microporous membrane according to claim 1, wherein the polymeric ultrafiltration membrane in the step (5) is at least one of a polysulfone ultrafiltration membrane, a polyethersulfone ultrafiltration membrane, a polyacrylonitrile ultrafiltration membrane, a polyvinylidene fluoride ultrafiltration membrane, a polystyrene ultrafiltration membrane or a polyvinyl chloride ultrafiltration membrane.
5. The method for preparing a polyamide composite membrane with the assistance of the hydrophobic lipophilic microporous membrane according to claim 1, wherein the microporous membrane in the step (6) is at least one of a polyvinylidene fluoride nanofiber membrane, a polytetrafluoroethylene membrane, a polysulfone nanofiber membrane, a polystyrene nanofiber membrane or a polyvinyl chloride nanofiber membrane.
6. The method for preparing the polyamide composite membrane with the assistance of the hydrophobic lipophilic microporous membrane according to claim 1, wherein the microporous membrane in the step (6) is a hydrophobic membrane and has a pore size of 0.1-2 μm.
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