CN115069090B - Intelligent nanofiltration membrane with double-electric-layer surface and preparation method thereof - Google Patents

Intelligent nanofiltration membrane with double-electric-layer surface and preparation method thereof Download PDF

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CN115069090B
CN115069090B CN202210856565.4A CN202210856565A CN115069090B CN 115069090 B CN115069090 B CN 115069090B CN 202210856565 A CN202210856565 A CN 202210856565A CN 115069090 B CN115069090 B CN 115069090B
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layer surface
nanofiltration membrane
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CN115069090A (en
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邵会菊
秦舒浩
常金燕
武晓
雷婷
刁延芳
张芳芳
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Guizhou Material Industrial Technology Research Institute
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • 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
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0006—Organic membrane manufacture by chemical reactions
    • 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
    • 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
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/78—Graft polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/26—Electrical properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Abstract

The invention discloses a preparation method of an intelligent nanofiltration membrane with an electric double layer surface, which introduces molecular chains with different chargers on the surface of a conductive membrane and utilizes the difference of the responsiveness of the molecular chains to electric field stimulation to form an electric double layer structure. The beneficial effects of the invention are as follows: the invention constructs a nanofiltration separation layer containing different charged molecular chains on the surface of the conductive ultrafiltration membrane, and uses an electric field to induce the molecular chains to generate orientation arrangement in the filtration process so as to form a special electric double layer structure, thereby realizing accurate molecular separation by adjusting parameters such as the direction, the intensity and the like of the electric field and improving the anti-pollution performance of the separation membrane by using the enhanced electrostatic repulsion effect.

Description

Intelligent nanofiltration membrane with double-electric-layer surface and preparation method thereof
Technical Field
The invention relates to the technical field of polymer intelligent membranes, in particular to an intelligent nanofiltration membrane with an electric double layer surface and a preparation method thereof.
Background
Nanofiltration is an important branch in a membrane separation technology, and the special micropore structure and the charge effect on the surface of the nanofiltration membrane enable the nanofiltration membrane to efficiently remove multivalent ions, dyes and other organic molecules in water according to pore size screening and Donnan effect, and can realize the effective separation of monovalent ions and divalent/multivalent ions, so that the nanofiltration membrane has wide application prospects in the fields of sea water desalination, biological purification, water treatment and the like. However, improving separation performance (high permeation, high selectivity rejection) and anti-fouling capability are two major problems facing the need for nanofiltration membranes during use. In particular, the increasing demands on separation accuracy of dye-containing wastewater systems place higher demands on the design of the surface microstructure of nanofiltration membranes. However, based on pressure driven nanofiltration membranes, the "trade-off" effect between permeability and selectivity makes it difficult to achieve both high permeability and high selectivity rejection of the membrane; in addition, unlike protein and other organic matters, dye molecules are charged in water due to dissociation, and active groups contained in the dye molecules are easy to interact with the surface of the nanofiltration membrane strongly so as to be adsorbed on the surface of the nanofiltration membrane, so that the surface of the nanofiltration membrane is more easy to be polluted. Therefore, how to construct the nano-filtration membrane surface microstructure capable of obviously reducing the interaction between dye and membrane surface, and to organically couple membrane separation with other technologies, further improves the separation performance and dye pollution (dyeing) resistance of the nano-filtration membrane, and is a key problem for solving the nano-filtration membrane trade-off effect and improving the pollution resistance.
The separation of substances is realized by the nanofiltration membrane by means of pore size screening and the Donnan effect, which is mainly influenced by the surface chargeability of the nanofiltration membrane. Thus, the surface charge plays an important role in nanofiltration membrane separation. Nanofiltration membranes can be classified into negatively charged nanofiltration membranes, positively charged nanofiltration membranes and amphoteric charged nanofiltration membranes according to the difference of surface charges. The pollutant with opposite charge on the surface of the membrane is easy to be adsorbed on the surface of the membrane to cause serious pollution due to the electrostatic effect, so that the positively charged or negatively charged nanofiltration membrane has good anti-pollution performance on the pollutant with the same charge, and has poor anti-pollution performance on the pollutant with opposite charge. The content of anionic groups and cationic groups in the amphoteric charge nanofiltration membrane is equal, the net charge is zero, and the electrostatic effect between the membrane surface and charged organic matters can be obviously reduced, so that the anti-pollution performance is improved. However, a decrease in surface charge means a decrease in the Donnan effect, reducing the effect of nanofiltration to remove dye.
Disclosure of Invention
The invention provides a preparation method of an intelligent nanofiltration membrane with an electric double layer surface, which introduces molecular chains with different chargers on the surface of a conductive membrane, utilizes the difference of the responsiveness of the molecular chains to electric field stimulation to form an electric double layer structure, and realizes the precise separation and high anti-pollution performance of the membrane by adjusting parameters such as the direction, the strength and the like of the electric field, thereby solving the technical problems related in the background technology.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the preparation method of the intelligent nanofiltration membrane with the double electric layer surface comprises the following steps of:
firstly, dissolving a polyamino polymer and a zwitterionic monomer in a certain mass ratio in a mixed solution of water and isopropanol at a temperature of 40-60 ℃, regulating the PH of the solution to 11-13 by adopting sodium hydroxide, stirring and raising the temperature to 70-90 ℃ while heating, and then carrying out constant-temperature reaction for 36-50 hours;
packaging the mixed solution completely reacted in the first step into a dialysis bag, and then soaking the dialysis bag in deionized water at room temperature for 36-50 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, placing the solution subjected to the dialysis in a vacuum drying oven at 60-80 ℃ for drying for 8-24 hours to obtain a mixture of the polyamino polymer and a grafted product thereof;
step four, dissolving the mixture obtained in the step three in dimethylacetamide to purify the prepared polyamino polymer grafted zwitterionic product;
fifthly, dissolving the polyamino polymer grafted zwitterionic product obtained in the step four and glutaraldehyde in deionized water according to a certain mass ratio to prepare a modified solution;
step six, the conductivity is 1.0 to 5.0x10 -3 Soaking the upper surface of the conductive ultrafiltration membrane within the S/cm range in the modified solution prepared in the step five for 1-10 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the conductive ultrafiltration membrane out of the modified solution, and repeatedly flushing the conductive ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
As a preferable improvement of the present invention, in the first step, the polyamino polymer is selected from any one of polyethyleneimine having a molecular weight of 1500 to 2000 and polyethyleneamine having a molecular weight of 1000 to 3000.
As a preferred modification of the present invention, in the first step, the zwitterionic monomer is selected from any one of sulfobetaine methacrylate, methacrylamide carboxylic acid betaine, 2-methacryloyloxyethyl phosphorylcholine.
As a preferred improvement of the present invention, in the first step, the volume ratio of water to isopropyl alcohol is 3 to 5:1.
as a preferred improvement of the invention, in step two, the dialysis bag has a molecular weight cut-off of 1800-3500.
As a preferred modification of the present invention, in step five, the temperature of the deionized water is 50 ℃.
The invention also provides an intelligent nanofiltration membrane with the double-electric-layer surface, which is prepared by the preparation method of the intelligent nanofiltration membrane with the double-electric-layer surface.
The beneficial effects of the invention are as follows: the invention constructs a nanofiltration separation layer containing different charged molecular chains on the surface of the conductive ultrafiltration membrane, and uses an electric field to induce the molecular chains to generate orientation arrangement in the filtration process so as to form a special electric double layer structure, thereby realizing accurate molecular separation by adjusting parameters such as the direction, the intensity and the like of the electric field and improving the anti-pollution performance of the separation membrane by using the enhanced electrostatic repulsion effect.
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For a clearer description of the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly introduced below, it being obvious that the drawings in the description below are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art, wherein:
FIG. 1 is a schematic representation of the "double electric layer" of the ultrafiltration membrane surface and its selective separation in accordance with the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered as not existing, and not falling within the scope of protection claimed by the present invention.
The invention provides a preparation method of an intelligent nanofiltration membrane with an electric double layer surface, which comprises the following steps:
firstly, dissolving a polyamino polymer and a zwitterionic monomer in a certain mass ratio in a mixed solution of water and isopropanol at a temperature of 40-60 ℃, regulating the PH of the solution to 11-13 by adopting sodium hydroxide, stirring and raising the temperature to 70-90 ℃ while heating, and then carrying out constant-temperature reaction for 36-50 hours;
specifically, the polyamino polymer is selected from any one of polyethyleneimine with molecular weight of 1500-2000 and polyethyleneamine with molecular weight of 1000-3000. The zwitterionic monomer is selected from any one of sulfobetaine methacrylate, methacrylamide carboxylic acid betaine and 2-methacryloyloxyethyl phosphorylcholine. The volume ratio of water to isopropanol is 3-5: 1.
packaging the mixed solution completely reacted in the first step into a dialysis bag, and then soaking the dialysis bag in deionized water at room temperature for 36-50 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
specifically, the molecular weight cut-off of the dialysis bag is 1800-3500.
Step three, placing the solution subjected to the dialysis in a vacuum drying oven at 60-80 ℃ for drying for 8-24 hours to obtain a mixture of the polyamino polymer and a grafted product thereof;
step four, dissolving the mixture obtained in the step three in dimethylacetamide to purify the prepared polyamino polymer grafted zwitterionic product;
fifthly, dissolving the polyamino polymer grafted amphoteric ion product in the fourth step and glutaraldehyde in deionized water at 50 ℃ according to a certain mass ratio to prepare a modified solution;
step six, the conductivity is 1.0 to 5.0x10 -3 Soaking the upper surface of the conductive ultrafiltration membrane within the S/cm range in the modified solution prepared in the step five for 1-10 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
referring specifically to fig. 1, the principle of constructing a nanofiltration separation layer is as follows: when the separation membrane is used as an anode (the positive electrode of the electric field is in contact with the separation membrane), positively charged molecular chains stretch away from the surface of the membrane due to the action of electrostatic repulsive force, and negatively charged molecular chains are tightly adsorbed on the surface of the membrane due to the action of electrostatic attractive force, so that an electric double layer structure in which the charged molecular chains are aligned is formed, as shown in the upper right of fig. 1; on the contrary, when the separation membrane is used as a cathode (the electric field cathode is in contact with the separation membrane), the negatively charged molecular chains stretch to the direction away from the membrane surface due to the action of electrostatic repulsive force, and meanwhile, the positively charged molecular chains are tightly adsorbed on the membrane surface due to the action of electrostatic attractive force, so that an electric double layer structure as shown in the lower right part of fig. 1 is formed, and thus, the accurate separation meeting the requirements can be realized by reversing the electric field electrode, and the pollution resistance of the separation membrane can be improved due to the enhanced electrostatic repulsive force.
And step seven, taking the conductive ultrafiltration membrane out of the modified solution, and repeatedly flushing the conductive ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
The following describes in detail a preparation method of an intelligent nanofiltration membrane with an electric double layer surface according to specific examples.
Example 1
Example 1 provides a method for preparing an intelligent nanofiltration membrane with an electric double layer surface, which is realized by the following steps:
step one, dissolving polyethyleneimine (PEI, molecular weight 1800) and sulfobetaine methacrylate (SBMA) in a mass ratio of 2:3 in a mixed solution of water and isopropanol (v/v=4), regulating the PH of the solution to 12 by adopting sodium hydroxide, stirring and raising the temperature to 80 ℃ and then carrying out constant-temperature reaction for 48 hours;
packaging the completely reacted mixed solution in the first step into a dialysis bag (with a molecular weight cut-off of 2000), and then soaking the dialysis bag in deionized water at room temperature for 48 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, placing the dialyzed solution in a vacuum drying oven at 60 ℃ for drying for 24 hours to obtain a mixture of PEI and PEI-g-SBMA;
step four, dissolving the mixture in dimethylacetamide to purify the PEI-g-SBMA product prepared;
step five, dissolving PEI-g-SBMA and glutaraldehyde prepared in the step four in deionized water at 50 ℃ in a mass ratio of 6:1 to prepare a modified solution;
step six, an electrically conductive polyvinylidene fluoride/styrene-maleic anhydride copolymer (PVDF/SMA) ultrafiltration membrane (conductivity 1.0X10) -3 S/cm) was immersed in the above-mentioned modifying solution for 3 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the ultrafiltration membrane out of the modified solution, and repeatedly flushing the ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
Example 2
Example 2 provides a method for preparing an intelligent nanofiltration membrane with an electric double layer surface, which is realized by the following steps:
step one, dissolving polyethyleneimine (PEI, molecular weight 1800) and methacrylamide Carboxylic Betaine (CBMA) in a mass ratio of 2:3 in a mixed solution of water and isopropanol (v/v=3), regulating the PH of the solution to 11 by adopting sodium hydroxide, stirring, heating to 90 ℃ while stirring, and then carrying out constant-temperature reaction for 36 hours;
packaging the completely reacted mixed solution in the first step into a dialysis bag (with a molecular weight cut-off of 2000), and then soaking the dialysis bag in deionized water at room temperature for 48 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, placing the dialyzed solution in a vacuum drying oven at 60 ℃ for drying for 24 hours to obtain a mixture of PEI and PEI-g-CBMA;
step four, dissolving the mixture in dimethylacetamide to purify the prepared PEI-g-CBMA product;
fifthly, dissolving PEI-g-CBMA and glutaraldehyde prepared in the fourth step into deionized water at 50 ℃ in a mass ratio of 6:1 to prepare a modified solution;
step six, an electrically conductive polyvinylidene fluoride/styrene-maleic anhydride copolymer (PVDF/SMA) ultrafiltration membrane (conductivity 2.5X10) -3 S/cm) was immersed in the above-mentioned modifying solution for 3 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the ultrafiltration membrane out of the modified solution, and repeatedly flushing the ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
Example 3
Example 3 provides a method for preparing an intelligent nanofiltration membrane with an electric double layer surface, which is realized by the following steps:
step one, dissolving polyvinyl amine (PVAM, molecular weight 1500) and sulfobetaine methacrylate (SBMA) in a mass ratio of 1:2 in a mixed solution of water and isopropanol (v/v=4) at 50 ℃, adjusting the PH of the solution to 12 by adopting sodium hydroxide, stirring and raising the temperature to 80 ℃ and then carrying out constant-temperature reaction for 48 hours;
packaging the completely reacted mixed solution in the first step into a dialysis bag (with a molecular weight cut-off of 1800), and then soaking the dialysis bag in deionized water at room temperature for 48 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, the dialyzed solution is dried for 10 hours in a vacuum drying oven at 80 ℃ to obtain a mixture of PVAM and PVAM-g-SBMA;
step four, dissolving the mixture in dimethylacetamide to purify the prepared PVAM-g-SBMA product;
step five, dissolving PVAM-g-SBMA and glutaraldehyde prepared in the step four in deionized water at 50 ℃ in a mass ratio of 5:1 to prepare a modified solution;
step six, an electrically conductive polyvinylidene fluoride/styrene-maleic anhydride copolymer (PVDF/SMA) ultrafiltration membrane (conductivity 4.5X10) -3 S/cm) is immersed in the above-mentioned modifying solution for 5 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the ultrafiltration membrane out of the modified solution, and repeatedly flushing the ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
Example 4
Example 4 provides a method for preparing an intelligent nanofiltration membrane with an electric double layer surface, which is realized by the following steps:
step one, dissolving polyvinyl amine (PVAM, molecular weight 2800), 2-Methacryloyloxyethyl Phosphorylcholine (MPC) in a mass ratio of 1:3 in a mixed solution of water/isopropanol (v/v=5), adjusting the PH of the solution to 13 by adopting sodium hydroxide, stirring and raising the temperature to 70 ℃ and then carrying out constant-temperature reaction for 50 hours;
packaging the completely reacted mixed solution in the first step into a dialysis bag (with the molecular weight cut-off of 3200), and then soaking the dialysis bag in deionized water at room temperature for 48 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, the dialyzed solution is dried for 24 hours in a vacuum drying oven at 60 ℃ to obtain a mixture of PVAM and PVAM-g-MPC;
step four, dissolving the mixture in dimethylacetamide to purify the prepared PVAM-g-MPC product;
step five, dissolving PVAM-g-MPC and glutaraldehyde prepared in the step four in deionized water at 50 ℃ in a mass ratio of 6:1 to prepare a modified solution;
step six, an ultrafiltration membrane of conductive polysulfone/styrene-maleic anhydride copolymer (PSF/SMA) (conductivity 3.5X10 -3 S/cm) is immersed in the above-mentioned modifying solution for 5 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the ultrafiltration membrane out of the modified solution, and repeatedly flushing the ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
Example 5
Example 5 provides a method for preparing an intelligent nanofiltration membrane with an electric double layer surface, which is realized by the following steps:
step one, dissolving polyvinyl amine (PVAM, molecular weight 2000) and sulfobetaine methacrylate (SBMA) in a mass ratio of 2:3 in a mixed solution of water and isopropanol (v/v=4) at 50 ℃, adjusting the PH of the solution to 12 by adopting sodium hydroxide, stirring and raising the temperature to 80 ℃ and then carrying out constant-temperature reaction for 48 hours;
packaging the completely reacted mixed solution in the first step into a dialysis bag (with molecular weight cut-off of 2200), and then soaking the dialysis bag in deionized water at room temperature for 48 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, the dialyzed solution is dried for 24 hours in a vacuum drying oven at 60 ℃ to obtain a mixture of PVAM and PVAM-g-SBMA;
step four, dissolving the mixture in dimethylacetamide to purify the prepared PVAM-g-SBMA product;
step five, dissolving PVAM-g-SBMA and glutaraldehyde prepared in the step four in deionized water at 50 ℃ in a mass ratio of 6:1 to prepare a modified solution;
step six, an ultrafiltration membrane of conductive polyethersulfone/styrene-maleic anhydride copolymer (PSF/SMA) (conductivity 2.6X10 -3 S/cm)Immersing the surface in the modified solution for 8 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the ultrafiltration membrane out of the modified solution, and repeatedly flushing the ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
Example 6
Example 6 provides a method for preparing an intelligent nanofiltration membrane with an electric double layer surface, which is implemented according to the following steps:
step one, dissolving polyvinyl amine (PVAM, molecular weight 2000) and sulfobetaine methacrylate (SBMA) in a mass ratio of 1:2 in a mixed solution of water and isopropanol (v/v=5) at 50 ℃, regulating the PH of the solution to 12 by adopting sodium hydroxide, stirring and raising the temperature to 80 ℃ and then carrying out constant-temperature reaction for 48 hours;
packaging the completely reacted mixed solution in the first step into a dialysis bag (with molecular weight cut-off of 2200), and then soaking the dialysis bag in deionized water at room temperature for 48 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, the dialyzed solution is dried for 24 hours in a vacuum drying oven at 60 ℃ to obtain a mixture of PVAM and PVAM-g-SBMA;
step four, dissolving the mixture in dimethylacetamide to purify the prepared PVAM-g-SBMA product;
step five, dissolving PVAM-g-SBMA and glutaraldehyde prepared in the step four in deionized water at 50 ℃ according to a mass ratio of 4:1 to prepare a modified solution;
step six, an ultrafiltration membrane of conductive polyethersulfone/styrene-maleic anhydride copolymer (PSF/SMA) (conductivity 4.3X10 -3 S/cm) is immersed in the above-mentioned modifying solution for 5 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the ultrafiltration membrane out of the modified solution, and repeatedly flushing the ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
Example 7
Example 7 provides a method for preparing an intelligent nanofiltration membrane with an electric double layer surface, which is implemented according to the following steps:
step one, dissolving polyethyleneimine (PEI, molecular weight 1800) and sulfobetaine methacrylate (SBMA) in a mass ratio of 2:3 in a mixed solution of water and isopropanol (v/v=4), regulating the PH of the solution to 12 by adopting sodium hydroxide, stirring and raising the temperature to 80 ℃ and then carrying out constant-temperature reaction for 48 hours;
packaging the completely reacted mixed solution in the first step into a dialysis bag (with a molecular weight cut-off of 2000), and then soaking the dialysis bag in deionized water at room temperature for 48 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, placing the dialyzed solution in a vacuum drying oven at 60 ℃ for drying for 24 hours to obtain a mixture of PEI and PEI-g-SBMA;
step four, dissolving the mixture in dimethylacetamide to purify the PEI-g-SBMA product prepared;
step five, dissolving PVAM-g-SBMA and glutaraldehyde prepared in the step four in deionized water at 50 ℃ according to a mass ratio of 4:1 to prepare a modified solution;
step six, an ultrafiltration membrane of conductive polyethersulfone/styrene-maleic anhydride copolymer (PES/SMA) (conductivity 4.3X10 -3 S/cm) is immersed in the above-mentioned modifying solution for 5 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the ultrafiltration membrane out of the modified solution, and repeatedly flushing the ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
Comparative example 1
Examples 6 and 7 employed PES/SMA conductive ultrafiltration membranes with negative charge on the surface (conductivity 4.3X10 - 3 S/cm), the specific preparation method is as follows:
dissolving 14wt% of PES, 3wt% of SMA,3wt% of carbon nano tube, 8wt% of polyvinyl alcohol and 72wt% of dimethylacetamide in a temperature range of 70 ℃ for 30 hours to obtain uniform casting solution;
after defoaming treatment for 6 hours, coating the glass plate by adopting an automatic film scraping machine, standing for 30 seconds in air, and then placing the glass plate into coagulating bath water for cross-conversion to form a film;
the prepared composite film was taken out of the coagulation bath and then placed in distilled water to remove the residual solvent.
Comparative example 2
Example 4 was performed using PSF/SMA conductive ultrafiltration membrane with negative charge on the surface (conductivity 3.5X10 -3 S/cm), the specific preparation method is as follows:
16wt% of PSF, 3wt% of SMA,3wt% of carbon nano tube, 8wt% of polyvinyl alcohol and 70wt% of dimethylacetamide are dissolved for 30 hours in a temperature range of 70 ℃ to obtain uniform casting solution;
after defoaming treatment for 6 hours, coating the glass plate by adopting an automatic film scraping machine, standing for 30 seconds in air, and then placing the glass plate into coagulating bath water for cross-conversion to form a film;
the prepared composite film was taken out of the coagulation bath and then placed in distilled water to remove the residual solvent.
Comparative example 3
Example 3 PVDF/SMA conductive ultrafiltration membrane with negative charge on the surface (conductivity 4.5X10 -3 S/cm), the specific preparation method is as follows:
dissolving 16wt% of PES, 3wt% of SMA,3wt% of carbon nano tube, 8wt% of polyvinyl alcohol and 70wt% of dimethylacetamide in a temperature range of 70 ℃ for 30 hours to obtain uniform casting solution;
after defoaming treatment for 6 hours, coating the glass plate by adopting an automatic film scraping machine, standing for 30 seconds in air, and then placing the glass plate into coagulating bath water for cross-conversion to form a film;
the prepared composite film was taken out of the coagulation bath and then placed in distilled water to remove the residual solvent.
The invention also provides an intelligent nanofiltration membrane with the double-electric-layer surface, which is prepared by the preparation method of the intelligent nanofiltration membrane with the double-electric-layer surface.
Among them, the electronically controlled separation properties of the intelligent nanofiltration membranes prepared by examples 1 to 7 and comparative examples 1 to 3 are shown in table 1.
Table 1 electric control separation performance of intelligent nanofiltration membrane
Figure BDA0003754624730000101
It should be further noted that the structures and properties of the dye molecules referred to in Table 1 are shown in Table 2.
TABLE 2 Structure and Properties of dye molecules
Figure BDA0003754624730000111
The beneficial effects of the invention are as follows: the invention constructs a nanofiltration separation layer containing different charged molecular chains on the surface of the conductive ultrafiltration membrane, and uses an electric field to induce the molecular chains to generate orientation arrangement in the filtration process so as to form a special electric double layer structure, thereby realizing accurate molecular separation by adjusting parameters such as the direction, the intensity and the like of the electric field and improving the anti-pollution performance of the separation membrane by using the enhanced electrostatic repulsion effect.
Although embodiments of the present invention have been disclosed above, it is not limited to the details and embodiments shown and described, it is well suited to various fields of use for which the invention would be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.

Claims (7)

1. The preparation method of the intelligent nanofiltration membrane with the double electric layer surface is characterized by comprising the following steps of:
firstly, dissolving a polyamino polymer and a zwitterionic monomer in a certain mass ratio in a mixed solution of water and isopropanol at a temperature of 40-60 ℃, regulating the PH of the solution to 11-13 by adopting sodium hydroxide, stirring and raising the temperature to 70-90 ℃ while heating, and then carrying out constant-temperature reaction for 36-50 hours;
packaging the mixed solution completely reacted in the first step into a dialysis bag, and then soaking the dialysis bag in deionized water at room temperature for 36-50 hours to remove residual zwitterionic monomers, sodium hydroxide ions and isopropanol solvent;
step three, placing the solution subjected to the dialysis in a vacuum drying oven at 60-80 ℃ for drying for 8-24 hours to obtain a mixture of the polyamino polymer and a grafted product thereof;
step four, dissolving the mixture obtained in the step three in dimethylacetamide to purify the prepared polyamino polymer grafted zwitterionic product;
fifthly, dissolving the polyamino polymer grafted zwitterionic product obtained in the step four and glutaraldehyde in deionized water according to a certain mass ratio to prepare a modified solution;
step six, the conductivity is 1.0 to 5.0x10 -3 Soaking the upper surface of the conductive ultrafiltration membrane within the S/cm range in the modified solution prepared in the step five for 1-10 hours to construct a nanofiltration separation layer containing positively and negatively charged molecular chains;
and step seven, taking the conductive ultrafiltration membrane out of the modified solution, and repeatedly flushing the conductive ultrafiltration membrane with deionized water to remove unreacted substances remained on the surface, thereby obtaining the intelligent nanofiltration membrane with the double-electric-layer surface.
2. The method for preparing the intelligent nanofiltration membrane with the electric double layer surface according to claim 1, wherein the method comprises the following steps: in the first step, the polyamino polymer is selected from any one of polyethyleneimine with molecular weight of 1500-2000 and polyethyleneamine with molecular weight of 1000-3000.
3. The method for preparing a smart nanofiltration membrane with an electric double layer surface according to claim 1, wherein in the first step, the zwitterionic monomer is selected from any one of sulfobetaine methacrylate, methacrylamide carboxylic acid betaine, and 2-methacryloyloxyethyl phosphorylcholine.
4. The method for preparing an intelligent nanofiltration membrane with an electric double layer surface as claimed in claim 1, wherein in the first step, the volume ratio of water to isopropanol is 3-5: 1.
5. the method of claim 1, wherein in step two, the dialysis bag has a molecular weight cut-off of 1800-3500.
6. The method of claim 1, wherein in the fifth step, the deionized water is at a temperature of 50 ℃.
7. An intelligent nanofiltration membrane with an electric double layer surface, which is characterized by being prepared by the preparation method of the intelligent nanofiltration membrane with the electric double layer surface according to any one of claims 1 to 6.
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